Transmucosal administration of pentobarbital and phenytoin solution induces euthanasia in bearded dragons (Pogona vitticeps)

OBJECTIVE

To assess the efficacy of transmucosal euthanasia solution to induce euthanasia.

ANIMALS

6 bearded dragons (Pogona vitticeps).

METHODS

An initial dose of euthanasia solution containing pentobarbital and phenytoin sodium was administered transmucosally in conscious lizards (100 mg/kg pentobarbital dose), followed by a second dose 20 minutes later (400 mg/kg pentobarbital dose). The presence of movement, leakage of euthanasia solution, behaviors consistent with oral irritation, respiratory rate, heart rate, palpebral and corneal reflex, and response to noxious stimuli were recorded until death, confirmed by the absence of Doppler cardiac flow and cardiac electrical activity. The time to loss of all parameters was calculated. Postmortem evaluation allowed for histopathologic evaluation of the oral cavity and gastrointestinal tract to detect potential mucosal damage from the alkaline euthanasia solution.

RESULTS

The median time to death was 300 minutes (range, 300 to 360 minutes), median time to respiratory arrest was 30 minutes (range, 30 to 50 minutes), and median time to loss of deep pain response was 30 minutes (range, 20 to 50 minutes). Signs consistent with oral irritation occurred in 4 of 6 (66.7%) lizards, including 2 lizards that exhibited whole-body spasms after euthanasia solution administration. Histopathologic changes indicating peracute mucosal ulceration, suspected to be from caustic causes, were identified in 1 (1/6 [16.7%]) lizard.

CLINICAL RELEVANCE

Transmucosal euthanasia solution administration resulted in clinical euthanasia within 6 hours. This method should be utilized only after premedication with analgesic and/or anesthetic medications due to the potential for acute mucosal ulceration and behaviors that may be distressing in client-owned animals.

Enteral Pentobarbital in the Difficult to Sedate Critically Ill Children

OBJECTIVE

Difficult analgosedation is common and challenging in the pediatric intensive care unit (PICU). It is important to study alternative and supplemental sedatives for when the first-line agents become -insufficient.

METHODS

In this retrospective chart-review study, we report our center's experience in using intermittent doses of enteral pentobarbital as an adjunct sedative in 13 difficult to sedate critically ill and mechanically ventilated children. We compare the average sedation score and cumulative doses of other -sedatives (opioids, benzodiazepines and alpha-2 agonists) in the 24 hours before and 24 hours after enteral -pentobarbital initiation.

RESULTS

The addition of enteral pentobarbital was associated with lower State Behavioral State (SBS) scores in 8 out of the 13 patients and on average smaller doses of opioids (decreased by 11%), benzodiazepines (BZD) (decreased by 5%) and alpha-agonists (decreased by 20%). No adverse effects were noted attributable to pentobarbital administration.

CONCLUSION

Enteral pentobarbital seems to be safe and effective agent in the difficult to sedate critically ill child.

The immune response to systemically administered endotoxin in the murine intestinal microcirculation under pentobarbital versus isoflurane anesthesia

BACKGROUND

Pentobarbital and isoflurane are commonly used veterinary anesthetics. Due to the dangers of overdose by repeat-bolus regimen of pentobarbital, isoflurane has been recommended. However, literature suggests isoflurane-induced inhibition of cytokine and adhesion molecule release, impacting leukocyte adhesion.

OBJECTIVE

This study aims to characterize the impacts of pentobarbital versus isoflurane on leukocyte interactions within the intestinal microcirculation with and without endotoxin challenge.

METHODS

Female BALB/c mice were subjected to pentobarbital or isoflurane (N = 20) and challenged with endotoxin or saline by intraperitoneal injection. The mice were kept under anesthesia for 2 hours. Fluorochromes, rhodamine-6 G and fluorescein isothiocyanate, were injected intravenously. To visualize leukocyte adhesion within the intestinal microcirculation, laparotomy and intravital microscopy was performed. Leukocyte rolling and adhesion was quantified offline in a blinded fashion.

RESULTS

Within collecting venules, leukocyte rolling and adhesion showed no significant differences between pentobarbital and isoflurane anesthesia under basal conditions. Endotoxin challenge caused a similar response in both anesthetic groups. Within postcapillary venules, no statistical differences between the two anesthetics were found for adhering leukocytes under basal conditions or following endotoxin challenge either. However, leukocyte rolling after LPS-challenge was significantly decreased in postcapillary venules during isoflurane anesthesia compared to pentobarbital anesthesia.

CONCLUSIONS

Isoflurane anesthesia showed only minor differences in the immune response to endotoxin within the intestinal microcirculation compared to pentobarbital anesthesia. Due to the superior safety profile of volatile anesthetics, immunological studies may choose isoflurane over pentobarbital as the veterinary anesthetic of choice.

General Anesthesia Blocks Pain-Induced Hemorrhage and Locomotor Deficits After Spinal Cord Injury in Rats

Research has shown that engaging pain (nociceptive) pathways after spinal cord injury (SCI) aggravates secondary injury and undermines locomotor recovery. This is significant because SCI is commonly accompanied by additional tissue damage (polytrauma) that drives nociceptive activity. Cutting communication with the brain by means of a surgical transection, or pharmacologically transecting the cord by slowly infusing a sodium channel blocker (lidocaine) rostral to a thoracic contusion, blocks pain-induced hemorrhage. These observations suggest that the adverse effect of pain after SCI depends on supraspinal (brain) systems. We hypothesize that inhibiting brain activity using a general anesthetic (e.g., pentobarbital, isoflurane) should have a protective effect. The present study shows that placing rats in an anesthetic state with pentobarbital or isoflurane 24 h after a lower thoracic contusion injury blocks pain-induced intraspinal inflammation and hemorrhage when administered before pain. Pentobarbital also extends protective effects against locomotor deficits produced by noxious stimulation. Inducing anesthesia after noxious stimulation, however, has no effect. Similarly, subanesthetic dosages of pentobarbital were also ineffective at blocking pain-induced hemorrhage. Also examined were the hemodynamic impacts of both pain and anesthetic delivery after SCI. Peripheral pain-input induced an acute increase in systolic blood pressure; isoflurane and pentobarbital prevent this increase, which may contribute to the protective effect of anesthesia. The results suggest that placing patients with SCI in a state akin to a medically induced coma can have a protective effect that blocks the adverse effects of pain.

Survey of veterinarians who use pentobarbital for euthanasia suggests knowledge gaps regarding animal disposal

OBJECTIVE

To assess (1) veterinarians' knowledge and practices regarding disposal of euthanized animals, (2) the extent to which veterinarians communicate with their clients about potential risks of rendering pentobarbital-euthanized animals, and (3) the extent to which veterinarians communicate potential relay toxicosis and environmental risks of pentobarbital-euthanized animals to clients.

SAMPLE

A stratified random sample of AVMA members.

METHODS

Over a 3-week period in early 2021, 16,831 of the AVMA's 99,500 members were surveyed, with 2,093 responses (a 12% response rate). Respondents were assigned to 1 of 3 categories on the basis of their answers: veterinarians euthanizing only food-producing species, veterinarians euthanizing only non-food-producing species, and veterinarians euthanizing both food-producing and non-food-producing species (ie, veterinarians euthanizing mixed species).

RESULTS

Veterinarians responding to this survey appeared to be aware of the major methods of animal disposal, and about 89% reported communicating the method of euthanasia with clients to help ensure appropriate animal disposal. However, the need for additional education on local, state, and federal laws and rendering, as well as on risks of relay toxicosis including wildlife predation and environmental impacts, was reported.

CLINICAL RELEVANCE

Survey results identified gaps in veterinarians' knowledge regarding animal disposal following pentobarbital euthanasia. Further education on this topic may be beneficial, particularly for early- and midcareer veterinarians who euthanize non-food-producing species and for veterinarians who euthanize mixed species in urban and suburban communities.

Thermal Response of Laboratory Rats (Rattus norvegicus) during the Application of Six Methods of Euthanasia Assessed by Infrared Thermography

Refinement is one of the principles aiming to promote welfare in research animals. The techniques used during an experimental protocol, including euthanasia selection, must prevent and minimize suffering. Although the current euthanasia methods applied to laboratory rodents are accepted, the controversial findings regarding the potential stress/distress they can cause is a field of research. The objective was to assess the thermal response of Wistar rats during various euthanasia methods using infrared thermography (IRT) to determine the method that prevents or diminishes the stress response and prolonged suffering. Pentobarbital (G1), CO2 (G2), decapitation (G3), isoflurane (G4), ketamine + xylazine (G5), and ketamine + CO2 (G6) were evaluated at five evaluation times with IRT to identify changes in the surface temperature of four anatomical regions: ocular (T°ocu), auricular (T°ear), interscapular (T°dor), and caudal (T°tai). Significant differences (p < 0.05) were found in G2 and G4, registering temperature increases from the administration of the drug to the cessation of respiratory rate and heart rate. Particularly, isoflurane showed a marked thermal response in T°ocu, T°ear, T°dor, and T°tai, suggesting that, in general, inhalant euthanasia methods induce stress in rats and that isoflurane might potentially cause distress, an effect that must be considered when deciding humane euthanasia methods in laboratory rodents.

Defining a "Good Death": Exploring Veterinarians' Perceptions of Companion Animal Euthanasia

This study was designed to determine how veterinarians define a good euthanasia experience. This information is used to generate a working definition of companion animal euthanasia that aligns with animal welfare standards and pet owners' expectations. An electronic survey distributed via veterinary-related social media (Facebook, Instagram) and listservs were completed by 249 veterinarians who perform feline and/or canine euthanasia. Our results suggest that very few veterinarians feel their veterinary school training adequately prepared them for euthanasia. When veterinarians were asked to rank a list of physiologic conditions and anatomical traits in order of euthanasia-related concerns, respiratory distress was ranked the highest, while the most concerning physical changes were reported to be indications or impressions of seizures or pain. The most commonly reported euthanasia injection technique performed by participants was intravenous administration of pentobarbital sodium (97%), and most veterinarians preferred having owners present (57%) or having no preference (38%) during euthanasia. Results suggest that veterinarians want a pain-free, anxiety-free experience for the patient, appreciate the use of sedatives before euthanasia, and feel that when available and appropriate, home euthanasia offers several benefits. This understanding of the numerous aspects involved in a good euthanasia experience can help inform the creation of an updated definition of companion animal euthanasia that strives to prioritize the welfare of the patient as well as the needs and expectations of the pet owner.

Case report: Fatal poisoning caused by additive effects of two barbiturates

A case of fatal poisoning involving multiple psychotropic drugs is presented. Quantitative toxicological analysis showed femoral blood concentrations of pentobarbital, phenobarbital, duloxetine, acetaminophen and tramadol were 10.39, 22.57, 0.22, 0.61 and 0.22 μg/ml, respectively. We concluded that the death was due to the additive effects of two barbiturates. As both pentobarbital and phenobarbital act on gamma-aminobutyric acid (GABA) receptors, central nervous system activity was suppressed, causing respiratory depression. Additive pharmacological effects should be considered in cases of massive ingestion of multiple drugs.

Chrysanthemum morifolium and Its Bioactive Substance Enhanced the Sleep Quality in Rodent Models via Cl- Channel Activation

Dried Chrysanthemum morifolium (Chry) flowers have been used in Korea as a traditional insomnia treatment. In this study, the sleep-promoting activity and improving sleep quality of Chry extract (ext) and its active substance linarin were analyzed by pentobarbital-induced sleep experiment in mice and electroencephalography (EEG), electromyogram (EMG) analysis in rats. In a dose-dependent manner, Chry ext and linarin promoted longer sleep duration in the pentobarbital-induced sleep test compared to pentobarbital-only groups at both hypnotic and subhypnotic doses. Chry ext administration also significantly improved sleep quality, as seen in the relative power of low-frequency (delta) waves when compared with the control group. Linarin increased Cl- uptake in the SH-SY5Y human cell line and chloride influx was reduced by bicuculline. After administration of Chry ext, the hippocampus, frontal cortex, and hypothalamus from rodents were collected and blotted for glutamic acid decarboxylase (GAD)65/67 and gamma-aminobutyric acid (GABA)A receptors subunit expression levels. The expression of α1-subunits, β2-subunits, and GAD65/67 of the GABAA receptor was modulated in the rodent brain. In conclusion, Chry ext augments pentobarbital-induced sleep duration and enhances sleep quality in EEG waves. These effects might be due to the activation of the Cl- channel.

A Case of Barbiturate Poisoning From Pentobarbital in a Young Japanese Patient

Concomitant prescriptions of psychotropic drugs such as sleeping pills, antidepressants, and anti-anxiety medications are common. The relationship between the number of psychotropic drug prescriptions and the incidence of drug overdose has not been reported. However, efforts have been made to reduce the number of concomitant prescriptions hoping that fewer prescriptions of multiple drugs will lower the incidence of drug overdoses. Furthermore, among sleeping pills, prescriptions of barbiturates have been gradually decreasing due to the risk of severe side effects and addiction. This report features a case of an overdose of pentobarbital tablets that caused the classic medical triad (impaired consciousness, hypotension, and hypothermia) of barbiturate intoxication under the characteristics of borderline personality disorder.

Intralipid Emulsion Therapy for the Treatment of Suspected Toxicity in 2 Avian Species

Intravenous lipid emulsion (ILE) therapy has shown promise as a treatment option for a variety of lipophilic toxins. Two birds presented for suspected ingestion of a toxic substance. A blue-and-gold macaw (Ara ararauna) presented after chewing a block of bromethalin rodenticide without overt clinical signs at the time of presentation. Additionally, a free-ranging bald eagle (Haliaeetus leucocephalus) was found weak and depressed near a municipal landfill after presumptive ingestion of pentobarbital. Both birds were treated with ILE therapy for potential intoxication without any adverse events. The macaw was clinically normal after 3 days of hospitalization and at a 1-week reevaluation. The eagle was transferred to a rehabilitation center after markedly improved mentation and strength and was released 7 days later. Clinicians should consider ILE therapy for the treatment of lipophilic toxicities; however, monitoring is recommended for persistent lipemia and other adverse effects that have been reported in the veterinary literature.

Development and Stability of a New Formulation of Pentobarbital Suppositories for Paediatric Procedural Sedation

Pentobarbital is a drug of choice to limit motion in children during paediatric procedural sedations (PPSs). However, despite the rectal route being preferred for infants and children, no pentobarbital suppositories are marketed, and therefore they must be prepared by compounding pharmacies. In this study, two suppository formulations of 30, 40, 50, and 60 mg of pentobarbital sodium were developed using hard-fat Witepsol^® W25 either alone (formulation F1) or with oleic acid (formulation F2). The two formulations were subjected to the following tests described in the European Pharmacopoeia: uniformity of dosage units, softening time, resistance to rupture, and disintegration time. The stability of both formulations was also investigated for 41 weeks of storage at 5 ± 3 °C using a stability-indicating liquid chromatography method to quantify pentobarbital sodium and research breakdown product (BP). Although both formulae were compliant to uniformity of dosage, the results were in favour of a faster disintegration of F2 compared to F1 (-63%). On the other hand, F1 was found to be stable after 41 weeks of storage unlike F2 for which several new peaks were detected during the chromatographic analysis, suggesting a shorter stability of only 28 weeks. Both formulae still need to be clinically investigated to confirm their safety and efficiency for PPS.

Evaluation of Oral Transmucosal Administration of Pentobarbital for Euthanasia of Conscious Wild Birds

This prospective study evaluated oral transmucosal pentobarbital sodium at three doses in 110 wild-caught wild birds requiring euthanasia. Birds received transmucosal pentobarbital at five (430 mg/kg), six (516 mg/kg), and seven times (602 mg/kg) the intravenous dose for mammals. Time to first effects and loss of consciousness, presence of pupillary light and corneal reflexes, apnea, and asystole were recorded each minute. When asystole was not achieved at 5 minutes, IV pentobarbital was administered. Combining data for all doses, loss of consciousness occurred at a median (range) of 2 minutes (0-4.75 min), apnea at 3 minutes (0-6 min), and asystole at 4 minutes (0.5-5 min). Loss of consciousness and apnea occurred significantly faster in the 602 mg/kg dose group than in the 430 mg/kg group (p = 0.009, difference of 0.6 ± 0.2 min; p = 0.024, difference of 0.7 ± 0.3 min), respectively. Apnea and asystole were achieved in 80/110 birds within 5 minutes. Oral transmucosal pentobarbital results in rapid loss of consciousness and respiratory arrest and provides a reliable alternative euthanasia method compared to intravenous administration.

A Comparison of Brain-State Dynamics across Common Anesthetic Agents in Male Sprague-Dawley Rats

Anesthesia is a powerful tool in neuroscientific research, especially in sleep research where it has the experimental advantage of allowing surgical interventions that are ethically problematic in natural sleep. Yet, while it is well documented that different anesthetic agents produce a variety of brain states, and consequently have differential effects on a multitude of neurophysiological factors, these outcomes vary based on dosages, the animal species used, and the pharmacological mechanisms specific to each anesthetic agent. Thus, our aim was to conduct a controlled comparison of spontaneous electrophysiological dynamics at a surgical plane of anesthesia under six common research anesthetics using a ubiquitous animal model, the Sprague-Dawley rat. From this direct comparison, we also evaluated which anesthetic agents may serve as pharmacological proxies for the electrophysiological features and dynamics of unconscious states such as sleep and coma. We found that at a surgical plane, pentobarbital, isoflurane and propofol all produced a continuous pattern of burst-suppression activity, which is a neurophysiological state characteristically observed during coma. In contrast, ketamine-xylazine produced synchronized, slow-oscillatory activity, similar to that observed during slow-wave sleep. Notably, both urethane and chloral hydrate produced the spontaneous, cyclical alternations between forebrain activation (REM-like) and deactivation (non-REM-like) that are similar to those observed during natural sleep. Thus, choice of anesthesia, in conjunction with continuous brain state monitoring, are critical considerations in order to avoid brain-state confounds when conducting neurophysiological experiments.

Evaluation of a human urine barbiturate test to screen for pentobarbital euthanasia of dogs and cats

Pentobarbital is used commonly to euthanize animals. Occasionally during a death investigation, it is necessary to determine whether a cat or dog was euthanized via pentobarbital overdose. Screening for the detection of barbiturates including pentobarbital can be performed using commercial immunochromatographic tests. We used a commercial immunochromatographic test for barbiturates in humans to screen for barbiturates in urine collected postmortem from 20 dogs and 20 cats to determine whether they had been euthanized with pentobarbital. Additionally, we analyzed the urine for pentobarbital using liquid chromatography-mass spectrometry as a confirmatory test. Screening and confirmation testing revealed 100% agreement between the tests and with the euthanasia status of each animal. Our results support the use of the immunochromatographic test for the screening of urine collected postmortem to assess for the presence of barbiturates, specifically pentobarbital, used for euthanasia.

The possible mechanism of Datura stramonium on pentobarbital-induced sleep in mice

BACKGROUND

Insomnia leads to the development of mental problems and missing of accuracy in affected persons. Various investigations have previously revealed which medicinal plants play a role in the improvement of insomnia. In this study, we evaluated the effect of hydro-alcoholic extract of Datura stramonium on insomnia in mice.

METHODS

The extracts and fractions at different concentrations were injected intraperitoneally (i.p.) to mice 30 min before the sodium pentobarbital (30 mg/kg, i.p.). Additionally, the blood was collected from cardiac and serum separated to measure brain-derived neurotrophic factor (BDNF). The LC-MS was done to identify the active components. Flumazenil or naloxone were also applied to study the possible mechanism of extract. The PC12 cells were then exposed to different doses of extract and fractions, in order to evaluate cytotoxicity by MTT assay and the measured LD₅₀.

RESULTS

The hydro-alcoholic extracts of calyx, seed and petal elevated sleep duration and decreased sleep latency. In addition, water, ethyl acetate and n-butanol fractions of hydro-alcoholic extract of petal increased sleep duration. Of note, Naloxone significantly reversed the hypnotic effect of the extract. The extract increased the level of BDNF in serums. As well, the toxicity assessment revealed that the extracts had not toxic on PC12 cells. The LD₅₀ value was obtained as 4.8 g/kg.

CONCLUSION

This research demonstrated that D. stramonium (including seed, petal and calyx) increased the hypnotic effect without neurotoxicity on PC12 cells. Sleep induction may be related to its active ingredients as well as the effect on opioid receptors.

Frontoparietal anodal tDCS reduces ketamine-induced oscillopathies

During the prodromal phase of schizophrenia with its complex and insidious clinical picture, electroencephalographic recordings detect widespread oscillation disturbances (or oscillopathies) during the wake-sleep cycle. Neural oscillations are electrobiomarkers of the connectivity state within systems. A single-systemic administration of ketamine, a non-competitive NMDA glutamate receptor antagonist, transiently reproduces the oscillopathies with a clinical picture reminiscent of the psychosis prodrome. This acute pharmacological model may help the research and development of innovative treatments against psychotic transition. Transcranial electrical stimulation is recognized as an appropriate non-invasive therapeutic modality since it can increase cognitive performance and modulate neural oscillations with little or no side effects. Therefore, our objective was to set up, in the sedated adult rat, a stimulation method that is able to normalize ketamine-induced increase in gamma-frequency (30-80 Hz) oscillations and decrease in sigma-frequency (10-17 Hz) oscillations. Unilateral and bipolar frontoparietal (FP), transcranial anodal stimulation by direct current (<+1 mA) was applied in ketamine-treated rats. A concomitant bilateral electroencephalographic recording of the parietal cortex measured the stimulation effects on its spontaneously occurring oscillations. A 5 min FP anodal tDCS immediately and quickly reduced, significantly with an intensity-effect relationship, the ketamine-induced gamma hyperactivity, and sigma hypoactivity at least in the bilateral parietal cortex. A duration effect was also recorded. The tDCS also tended to diminish the ketamine-induced delta hypoactivity. These preliminary neurophysiological findings are promising for developing a therapeutic proof-of-concept against neuropsychiatric disorders.

Pentobarbital Anesthesia Suppresses the Glucose Response to Acute Intermittent Hypoxia in Rat

A key feature of sleep disordered breathing syndromes, such as obstructive sleep apnea is intermittent hypoxia. Intermittent hypoxia is well accepted to drive the sympathoexcitation that is frequently associated with hypertension and diabetes, with measurable effects after just 1 h. The aim of this study was to directly measure the glucose response to 1 h of acute intermittent hypoxia in pentobarbital anesthetized rats, compared to conscious rats. However, we found that while a glucose response is measurable in conscious rats exposed to intermittent hypoxia, it is suppressed in anesthetized rats. Intermittent hypoxia for 1, 2, or 8 h increased blood glucose by 0.7 ± 0.1 mmol/L in conscious rats but had no effect in anesthetized rats (−0.1 ± 0.2 mmol/L). These results were independent of the frequency of the hypoxia challenges, fasting state, vagotomy, or paralytic agents. A supraphysiological challenge of 3 min of hypoxia was able to induce a glycemic response indicating that the reflex response is not abolished under pentobarbital anesthesia. We conclude that pentobarbital anesthesia is unsuitable for investigations into glycemic response pathways in response to intermittent hypoxia in rats.

Assessment of Controlled Substance Distribution to U.S. Veterinary Teaching Institutions From 2006 to 2019

Objective: To evaluate the changing pattern of distribution of Schedule II and III opioids, barbiturates, and stimulants to veterinary educational institutions in the United States.

Design: Longitudinal study.

Sample: Veterinary teaching institutions that use Schedule II and III drugs.

Procedures: Distribution of controlled substances to veterinary teaching institutions was obtained from the Drug Enforcement Administration's Automated Reports and Consolidated Orders System (ARCOS) for opioids (e.g., methadone, fentanyl, codeine), barbiturates (pentobarbital, butalbital), and stimulants (amphetamine, methylphenidate, lisdexamfetamine) from 2006–2019. Opioids were converted to their morphine milligram equivalents (MME) for evaluation over time.

Results: Controlled substance distribution to veterinary schools exhibited dynamic, and agent specific, changes. The total MME for 11 opioids peaked in 2013 and decreased by 17.3% in 2019. Methadone accounted for two-fifths (42.3%) and fentanyl over one-third (35.4%) of the total MME in 2019. Pentobarbital distribution was greatest by weight of all substances studied and peaked in 2011 at 69.4 kg. Stimulants underwent a pronounced decline and were very modest by 2014.

Conclusions and Clinical Relevance: Opioids by total MME in veterinary teaching practice have undergone more modest changes than opioids used with humans. Hydrocodone, codeine and recently fentanyl use have declined while methadone increased. Stimulant distribution decreased to become negligible. Together, this pattern of findings warrant continued monitoring.

Pentobarbital Coma With Therapeutic Hypothermia for Treatment of Refractory Intracranial Hypertension in Traumatic Brain Injury Patients: A Single Institution Experience

Introduction Traumatic brain injury (TBI) results in primary and secondary brain injuries. Secondary brain injury can lead to cerebral edema resulting in increased intracranial pressure (ICP) secondary to the rigid encasement of the skull. Increased ICP leads to decreased cerebral perfusion pressure which leads to cerebral ischemia. Refractory intracranial hypertension (RICH) occurs when ICP remains elevated despite first-tier therapies such as head elevation, straightening of the neck, analgesia, sedation, paralytics, cerebrospinal fluid (CSF) drainage, mannitol and/or hypertonic saline administration. If unresponsive to these measures, second-tier therapies such as hypothermia, barbiturate infusion, and/or surgery are employed. Methods This was a retrospective review of patients admitted at Arrowhead Regional Medical Center from 2008 to 2019 for severe TBI who developed RICH requiring placement into a pentobarbital-induced coma with therapeutic hypothermia. Primary endpoints included mortality, good recovery which was designated at Glasgow outcome scale (GOS) of 4 or 5, and improvement in ICP (goal is <20 mmHg). Secondary endpoints included complications, length of intensive care unit (ICU) stay, length of hospital stay, length of pentobarbital coma, length of hypothermia, need for vasopressors, and decompressive surgery versus no decompressive surgery. Results Our study included 18 patients placed in pentobarbital coma with hypothermia for RICH. The overall mortality rate in our study was 50%; with 60% mortality in pentobarbital/hypothermia only group, and 46% mortality in surgery plus pentobarbital/hypothermia group. Maximum ICP prior to pentobarbital/hypothermia was significantly lower in patients who had a prior decompressive craniectomy than in patients who were placed into pentobarbital/hypothermia protocol first (28.3 vs 35.4, p<0.0238). ICP was significantly reduced at 4 hours, 8 hours, 12 hours, 24 hours, and 48 hours after pentobarbital and hypothermia treatment. Initial ICP and maximum ICP prior to pentobarbital/hypothermia was significantly correlated with mortality (p=0.022 and p=0.026). Patients with an ICP>25 mmHg prior to pentobarbital/hypothermia initiation had an increased risk of mortality (p=0.0455). There was no statistically significant difference in mean ICP after 24 hours after pentobarbital/hypothermia protocol in survivors vs non-survivors. Increased time to reach 33°C was associated with increased mortality (r=0.47, p=0.047); with a 10.5-fold increase in mortality for >7 hours (OR 10.5, p=0.039). Conclusion Prolonged cooling time >7 hours was associated with a 10.5-fold increase in mortality and ICP>25 mmHg prior to initiation of pentobarbital and hypothermia is suggestive of a poor response to treatment. We recommend patients with severe TBI who develop RICH should first undergo a 12 x 15 cm decompressive hemicraniectomy because they have better survival and are more likely to have ICP <25 mmHg as the highest elevation of ICP if the ICP were to become and stay elevated again. Pentobarbital and hypothermia should be initiated if the ICP becomes elevated and sustained above 20 mmHg with a prior decompressive hemicraniectomy and refractory to other medical therapies. However, our data suggests that patients are unlikely to survive if there ICP does not decrease to less than 15mmHg at 8 and 12 hours after pentobarbital/hypothermia and remain less than 20 mmHg within first 48 hours.

Stability of Pentobarbital Hydrogel for Rectal Administration in Pediatric Procedural Sedation

Purpose: Pentobarbital is a sedative agent to limit children motion during computed tomography or magnetic resonance imaging (MRI) and ensures the successful completion of the imaging procedure. However, data on rectal drug formulation and its stability in practice are not available. The aim of this study was to formulate and evaluate the stability of a ready-to-use rectal pentobarbital gel. Methods: The formulation consisted of a hydrated gel containing 25 mg/mL of pentobarbital sodium, packaged in 10-mL amber glass bottles and stored at either 22°C to 25°C or 2°C to 8°C. At each predetermined time point, samples were taken for visual inspection, pH measurement, and analysis by a validated stability-indicating high-performance liquid chromatography (HPLC) method. The viscosity parameters of the hydrogel formulation were assessed. Results: The freshly prepared rectal formulations appeared clear, colorless, and particular-free with pH readings of 9.75 to 9.83. Over the 90 days of the study period, there was no significant change in appearance or pH values for all stability samples. The HPLC results confirmed the chemical stability when stored at 2°C to 8°C or at 22°C to 25°C. Conclusion: Pentobarbital hydrogel 25 mg/mL are stable chemically at least 90 days and can be administered to children for an effective and fast sedation.

Hypnotic Effects of Lactobacillus fermentum PS150TM on Pentobarbital-Induced Sleep in Mice

The bidirectional communication between the gastrointestinal tract and the central nervous system appears to be functionally linked to the intestinal microbiome, namely the microbiome-gut-brain axis (MGBA). Probiotics with health benefits on psychiatric or neurological illnesses are generally called psychobiotics, and some of them may also be able to improve sleep by targeting the MGBA. This study aimed to investigate the effects of a psychobiotic strain, Lactobacillus fermentum PS150TM (PS150TM), on sleep improvement by using a pentobarbital-induced sleep mouse model. Compared with the vehicle control group, the oral administration of PS150TM, but not the other L. fermentum strains, significantly decreased the sleep latency and increased the sleep duration of mice, suggesting strain-specific sleep-improving effects of PS150TM. Moreover, the ingestion of diphenhydramine, an antihistamine used to treat insomnia, as a drug control group, only increased the sleep duration of mice. We also found that the sleep-improving effects of PS150TM are time- and dose-dependent. Furthermore, the oral administration of PS150TM could attenuate a caffeine-induced sleep disturbance in mice, and PS150TM appeared to increase the expression of the gene encoding the adenosine 1 receptor in the hypothalamus of mice, as assessed by quantitative real-time polymerase chain reaction. Taken together, our results present a potential application of PS150TM as a dietary supplement for sleep improvement.

Iatrogenic Propylene Glycol Intoxication Due to High-Dose Pentobarbital for Refractory Intracranial Hypertension: A Case Report

Propylene glycol is a rarely reported toxicity from high-dose administration of certain intravenous drugs, including lorazepam and pentobarbital. We present a case of iatrogenic propylene glycol toxicity secondary to a high-dose pentobarbital infusion for the treatment of refractory intracranial hypertension due to cerebral venous sinus thrombosis. The patient developed metabolic acidosis and acute kidney failure secondary to propylene glycol toxicity. After initiation of continuous renal replacement therapy, the patient's acute renal failure and lactic acidosis resolved. Using the Naranjo scale, this case received a score of 5, defining it as a "probable" adverse drug event. In patients who develop lactic acidosis and acute renal failure after initiation of high-dose pentobarbital, propylene glycol toxicity should be higher up in the differential diagnosis. Monitoring the serum osmolality while on pentobarbital could help provide valuable information to prevent iatrogenic propylene glycol toxicity.

Effectiveness of the Sleep Enhancement by Green Romaine Lettuce (Lactuca sativa) in a Rodent Model

This study was conducted to investigate the effects of the extracts of green romaine lettuce (GRE) on sleep enhancement. GRE contains 1071.7 and 199.2 µg/g of extracts of lactucin and lactucopicrin, respectively, known as sleep enhancement substances. When 100 mg/kg of GRE was administered orally, sleep latency and duration time were significantly increased compared to controls (p < 0.05). Rapid eye movement (REM) sleep decreased with 100 mg/kg of GRE administration and non-REM (NREM) sleep also increased. There was no significant difference between REM and NREM among the oral GRE administration groups receiving 100, 120, and 160 mg/kg GRE. In the caffeine-induced insomnia model, total sleep time was significantly increased by 100 mg/kg GRE administration compared to the caffeine-treated group (p < 0.05). In addition, GRE inhibited the binding of [3H]-flumazenil in a concentration-dependent manner, and affinity of both lactucin and lactucopicrin to gamma-aminobutyric acid (GABA)A-benzodiazepine (BDZ) receptor was 80.7% and 55.9%, respectively. Finally, in the pentobarbital-induced sleep mouse model, the sleep enhancement effect of GRE was inhibited by flumazenil, an antagonist of BDZ. Thus, these results demonstrate that GRE acts via a GABAergic mechanism to promote sleep in a rodent model.

Is Orally Administered Pentobarbital a Safe and Effective Alternative to Chloral Hydrate for Pediatric Procedural Sedation?

OBJECTIVES

Chloral hydrate had been extensively used for children undergoing sedation for imaging studies, but after the manufacturer discontinued production, pediatric sedation providers explored alternative sedation medications. Those medications needed to be at least as safe and as effective as chloral hydrate. In this study, we examined if pentobarbital is a suitable replacement for chloral hydrate.

METHODS

Subjects who received pentobarbital were recruited from a prospectively collected database, whereas we used a retrospective chart review to study subjects who received chloral hydrate. Sedation success was defined as the ability to provide adequate sedation using a single medication. We included electively performed sedations for subjects aged 2 months to 3 years who received either pentobarbital or chloral hydrate orally. We excluded subjects stratified as American Academy of Anesthesiologists category III or higher and those who received sedation for electroencephalogram. The data collected captured subject demographics and complications.

RESULTS

Five hundred thirty-four subjects were included in the final analysis, 368 in the chloral hydrate group and 166 in the pentobarbital group. Subjects who received pentobarbital had a statistically significant higher success rate [136 (82%) vs 238 (65%), p < 0.001], but longer sleeping time (18.1% vs 0%, p < 0.001) in all age groups. Subjects who received chloral hydrate had a higher risk of airway complications in the <1 year of age group (6.5% vs 1.8%, p = 0.03).

CONCLUSIONS

For pediatric patients younger than 3 years of age undergoing sedation for imaging studies, oral pentobarbital may be at least as effective and as safe as chloral hydrate, making it an acceptable and practical alternative.

Development of a Quantitative Gas Chromatography-Tandem Mass Spectrometry Method for the Determination of Pentobarbital in Dog Food

In 2017, a commercially available dog food was found by our laboratory to be adulterated with the euthanasia drug pentobarbital. An FDA class 1 voluntary recall by the company ensued. Since there is no set tolerance for pentobarbital in food or feed, a sensitive method for its detection was required. We describe a simple, yet efficient, method for the extraction and quantitative analysis of the barbiturate in dog food. The procedure relies on a combined food emergency response network (FERN) and QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach to sample extraction followed by quantitative analysis by gas chromatography-tandem mass spectrometry (GC/MS/MS) using pentobarbital- d₅ as an internal standard. This procedure improves upon other GC/MS methodologies in that derivatization of pentobarbital or its deuterated internal standard is unnecessary, and sensitivity to a calculated limit of detection (LOD) of 0.6 ppb and a limit of quantitation (LOQ) of 2 ppb is achieved.

Sleep spindle dynamics during NREM and REM sleep following distinct general anaesthesia in control rats and in a rat model of Parkinson's disease cholinopathy

On the basis of our previous studies and the important role of the thalamo-cortical network in states of unconsciousness, such as anaesthesia and sleep, and in sleep spindles generation, we investigated sleep spindles (SS) and high-voltage sleep spindle (HVS) dynamics during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep following different types of general anaesthesia in both physiological controls and in a rat model of Parkinson's disease (PD) cholinopathy, to follow the impact of anaesthesia on post-anaesthesia sleep at the thalamo-cortical level through an altered sleep spindle dynamics. We recorded 6 hr of spontaneous sleep in all rats, both before and 48 hr after ketamine/diazepam or pentobarbital anaesthesia, and we used 1 hr of NREM or REM sleep from each to validate visually the automatically detected SS or HVS for their extraction and analysis. In the controls, SS occurred mainly during NREM, whereas HVS occurred only during REM sleep. Ketamine/diazepam anaesthesia promoted HVS, prolonged SS during NREM, induced HVS of increased frequency during REM, and increased SS/HVS densities during REM versus NREM sleep. Pentobarbital anaesthesia decreased the frequency of SS during NREM and the HVS density during REM sleep. Although the pedunculopontine tegmental nucleus lesion prolonged SS only during NREM sleep, in these rats, ketamine/diazepam anaesthesia suppressed HVS during both sleep states, whereas pentobarbital anaesthesia promoted HVS during REM sleep. The different impacts of two anaesthetic regimens on the thalamo-cortical regulatory network are expressed through their distinct sleep spindle generation and dynamics that are dependent on the NREM and REM state regulatory neuronal substrate.

Novel Metabolomic Comparison of Arterial and Jugular Venous Blood in Severe Adult Traumatic Brain Injury Patients and the Impact of Pentobarbital Infusion

Treatment of severe traumatic brain injury (TBI) in the intensive care unit focuses on controlling intracranial pressure, ensuring sufficient cerebral perfusion, and monitoring for secondary injuries. However, there are limited prognostic tools and no biomarkers or tests of the evolving neuropathology. Metabolomics has the potential to be a powerful tool to indirectly monitor evolving dysfunctional metabolism. We compared metabolite levels in simultaneously collected arterial and jugular venous samples in acute TBI patients undergoing intensive care as well as in healthy control volunteers. Our results show that, first, many circulating metabolites are decreased in TBI patients compared with healthy controls days after injury; both proline and hydroxyproline were depleted by ≥60% compared with healthy controls, as was gluconate. Second, both arterial and jugular venous plasma metabolomic analysis separates TBI patients from healthy controls and shows that distinct combinations of metabolites are driving the group separation in the two blood types. Third, TBI patients under heavy sedation with pentobarbital at the time of blood collection were discernibly different from patients not receiving pentobarbital. These results highlight the importance of accounting for medications in metabolomics analysis. Jugular venous plasma metabolomics shows potential as a minimally invasive tool to identify and study dysfunctional cerebral metabolism after TBI.

Hypnotic Effect of Red Cabbage (Brassica oleracea) on Pentobarbital-Induced Sleep in Mice

Objective:

The present study was performed to investigate the effect of hydroalcoholic extract of red cabbage and its fractions on sleeping behavior in mice.

Materials and Methods:

The extract and its fractions were injected to mice and sleep duration as well as sleep latency were recorded. Furthermore, toxicity of the extract was determined both in vivo and in vitro.

Results:

The extract increased sleep duration at doses of 50–200mg/kg (P < 0.001). This observed hypnotic effect was comparable to that of diazepam (3mg/kg) (P < 0.001 in comparison with control group). Ethyl acetate, n-butanol, and aqueous fractions could increase sleep duration (P < 0.001). The sleep latency was decreased by the extract (P < 0.001) and only ethyl acetate fraction (P < 0.001). LD₅₀ value for red cabbage extract was 2.4g/kg. There was no toxic effect on viability of cultured neuronal cells (PC12). Rotarod test results showed that there were no significant differences between the extract groups and the control group.

Conclusion:

The results suggest that red cabbage potentiates pentobarbital hypnosis without any toxic effect. The main component(s) responsible for this effect is most likely to be intermediate polar agent(s) such as flavonoids, which are found in ethyl acetate fraction of this plant.

Pitfall in Pupillometry: Exaggerated Ciliospinal Reflex in a Patient in Barbiturate Coma Mimicking a Nonreactive Pupil

Although a neurological examination is fundamental to the evaluation of comatose patients, it is less reliable in a medically induced coma. A commonly misinterpreted finding in patients in a pentobarbital coma is altered pupillary reactivity secondary to an exaggerated ciliospinal reflex. Recognizing an exaggerated ciliospinal reflex in patients in a pentobarbital coma is important and may prevent unnecessary intervention. We present a patient induced in a pentobarbital coma for the treatment of status epilepticus who exhibited a nonreactive pupil secondary to an exaggerated ciliospinal reflex confirmed by pupillometry. We also discuss the anatomy of the ciliospinal reflex and literature regarding its clinical relevance.

Pentobarbital Removal During Continuous Venovenous Hemofiltration: Case Report and Review of the Literature

BACKGROUND:

Renal replacement therapy may enhance the elimination of barbiturates. Pentobarbital clearance during continuous venovenous hemofiltration (CVVH) has not been described previously. We report a patient case involving the measurement of serial pentobarbital levels during CVVH and review relevant literature characterizing extracorporeal pentobarbital elimination.

METHODS:

The following is a retrospective report of a previously healthy 26-year-old woman who sustained a severe traumatic brain injury (TBI) and required administration of pentobarbital on hospital day 0 for intracranial pressure (ICP) control. Given concern for interference with the patient's ongoing neurologic assessments, pentobarbital was discontinued on hospital day 4. The patient's hospital course was complicated by acute kidney injury (AKI), requiring initiation of CVVH on hospital day 5. Daily serum pentobarbital levels were obtained during CVVH.

RESULTS:

While on CVVH, the patient's estimated pentobarbital clearance ranged from 6 to 44 mL/min and the elimination half-life ranged from 17.7 to 65.9 hours. Based on reductions in pentobarbital clearance during CVVH interruption, the elimination of drug was dependent upon extracorporeal removal in this patient. CVVH facilitated pentobarbital elimination in a manner approaching endogenous clearance in healthy individuals.

CONCLUSION:

We report clinically significant pentobarbital removal by CVVH in a patient with severe TBI. Application of CVVH may expedite reliable neurologic assessments and facilitate the application of clinical brain death examination following pentobarbital exposure.

The Emergence of Second-Generation Lethal Injection Protocols: A Brief History and Review

The history of capital punishment in the United States is long and controversial. In many cases, lethal injection has brought medical personnel, ethically and professionally charged with preserving life, into the arena of assisting the state in taking life. U.S. Supreme Court decisions, including Baze v. Rees (2008) and Glossip v. Gross (2015), have evaluated and condoned lethal injection protocols. Despite the judicial validation of some midazolam-containing protocols, controversy exists about the level of unconsciousness provided due to the ceiling effects of the drug. Drug shortages, induced in part by manufacturers under pressure by death penalty opponents and governments opposed to capital punishment, have forced states to sometimes use creative means to obtain medications for use in lethal injection, even proposing to allow inmates to supply their own drugs for use in execution. Others have resorted to using compounding pharmacies and enacting tougher execution secrecy laws to protect the identities of those involved in the process. Professional organizations representing health care team members, including nursing, medicine, and pharmacy, among others, have roundly denounced the medicalization of capital punishment. Legal challenges continue to mount at all levels, leading to an uncertain future for lethal injection.

Sedation methods for transthoracic echocardiography in children with Trisomy 21-a retrospective study

BACKGROUND

Many children with Trisomy 21 have neurologic or behavioral problems that make it difficult for them to remain still during noninvasive imaging studies, such as transthoracic echocardiograms (TTEcho). Recently, intranasal dexmedetomidine sedation has been introduced for this purpose. However, dexmedetomidine has been associated with bradycardia. Children with Trisomy 21 have been reported to have a higher risk of bradycardia and airway obstruction with sedation or anesthesia compared to children without Trisomy 21.

OBJECTIVE

Our aim was to quantify the incidence of age-defined bradycardia and other adverse effects in patients with Trisomy 21 under sedation for TTEcho using a variety of sedation and anesthesia techniques available and utilized at our institution in this challenging patient population, including intranasal dexmedetomidine, oral pentobarbital, general anesthesia with propofol, and general anesthesia with sevoflurane. Our primary hypothesis was that intranasal dexmedetomidine sedation would result in a significantly higher risk of bradycardia in patients with Trisomy 21, compared with other sedative or anesthetic regimens.

METHODS

This is a retrospective, observational study of 147 consecutive patients with Trisomy 21 who were sedated or anesthetized for transthoracic echocardiography. Efficacy of sedation was defined as no need for rescue sedation or conversion to an alternate technique. Lowest and highest heart rate, systolic blood pressure, oxygen saturation, and PR interval from formal electrocardiograms were extracted from the electronic medical record. These data were compared to age-defined normal values to determine adverse events.

RESULTS

Four methods of sedation or anesthesia were utilized to perform sedated transthoracic echocardiography: general anesthesia with sevoflurane by mask, general anesthesia with sevoflurane induction followed by intravenous propofol maintenance, oral pentobarbital, and intranasal dexmedetomidine. Intranasal dexmedetomidine 2.5 mcg·kg^-1 was an effective sedative as a single dose for TTEcho in 37 of 41 (90%) cases. Oral pentobarbital 5 mg·kg^-1 as a single dose for young children with Trisomy 21 was effective in 55 of 75 (73%) cases. Intranasal dexmedetomidine sedation was not associated with a significantly higher risk of bradycardia in patients with Trisomy 21, compared with other sedative or anesthetic regimens, when compared to oral pentobarbital for patients under 2 years of age and general anesthesia for children 3 years and older. The two general anesthesia groups showed lowest heart rates of 66.9 ± 15.9 min^-1 for sevoflurane and 69.0 ± 11.5 min^-1 for sevoflurane-propofol. Hypotension was present in all groups ranging between an incidence of 56% in the sevoflurane group to 11% in the oral pentobarbital group. Oxygen saturation and clinically significant desaturation occurred in 14% of the oral pentobarbital group.

CONCLUSION

Intranasal dexmedetomidine sedation was not associated with a significantly higher risk of bradycardia in patients with Trisomy 21, compared with other sedative or anesthetic regimens.

Integrating the Forensic Sciences in Wildlife Case Investigations: A Case Report of Pentobarbital and Phenytoin Toxicosis in a Bald Eagle (Haliaeetus leucocephalus)

The application of medical knowledge to the purpose of law is the foundation of forensic pathology. A forensic postmortem examination often involves the expertise of multiple scientific disciplines to reconstruct the full story surrounding the death of an animal. Wildlife poses additional challenges in forensic investigations due to little or no associated history, and the disruptive effects of decomposition. To illustrate the multidisciplinary nature of wildlife forensic medicine, the authors outline a case of secondary pentobarbital/phenytoin toxicosis in a bald eagle (Haliaeetus leucocephalus). The eagle was the single fatality in a group of 8 birds that fed on euthanized domestic cat remains that had been improperly disposed of in a landfill. Cooperation between responding law enforcement officers, pathologists, and other forensic scientists led to the successful diagnosis and resolution of the case.

Enhancing GABA Signaling during Middle Adulthood Prevents Age-Dependent GABAergic Interneuron Decline and Learning and Memory Deficits in ApoE4 Mice

Apolipoprotein E4 (apoE4) is the major genetic risk factor for Alzheimer's disease (AD). However, the underlying mechanisms are still poorly understood. We previously reported that female apoE4 knock-in (KI) mice had an age-dependent decline in hilar GABAergic interneurons that correlated with the extent of learning and memory deficits, as determined by Morris water maze (MWM), in aged mice. Enhancing GABA signaling by treating aged apoE4-KI mice with the GABAA receptor potentiator pentobarbital (PB) for 4 weeks before and during MWM rescued the learning and memory deficits. Here, we report that withdrawal of PB treatment for 2 weeks before MWM abolished the rescue in aged apoE4-KI mice, suggesting the importance of continuously enhancing GABA signaling in the rescue. However, treating apoE4-KI mice during middle adulthood (9-11 months of age) with PB for 6 weeks prevented age-dependent hilar GABAergic interneuron decline and learning and memory deficits, when examined at 16 month of age. These data imply that increasing inhibitory tone after substantial GABAergic interneuron loss may be an effective symptomatic, but not a disease-modifying, treatment for AD related to apoE4, whereas a similar intervention before substantial interneuron loss could be a disease-modifying therapeutic.

SIGNIFICANCE STATEMENT

We previously reported that female apoE4-KI mice had an age-dependent decline in hilar GABAergic interneurons that correlated with the extent of cognitive deficits in aged mice. The current study demonstrates that enhancing GABA signaling by treating aged apoE4-KI mice with a GABAA receptor potentiator pentobarbital (PB) before and during behavioral tests rescued the cognitive deficits; but withdrawal of PB treatment for 2 weeks before the tests abolished the rescue, suggesting the importance of continuously enhancing GABA signaling. However, treating apoE4-KI mice during middle adulthood with PB for a short period of time prevented age-dependent hilar GABAergic interneuron decline and cognitive deficits late in life, suggesting early intervention by enhancing GABA signaling as a potential strategy to prevent AD related to apoE4.

Effectiveness of Pharmacological Therapies for Intracranial Hypertension in Children With Severe Traumatic Brain Injury--Results From an Automated Data Collection System Time-Synched to Drug Administration

OBJECTIVES

To describe acute cerebral hemodynamic effects of medications commonly used to treat intracranial hypertension in children with traumatic brain injury. Currently, data supporting the efficacy of these medications are insufficient.

DESIGN

In this prospective observational study, intracranial hypertension (intracranial pressure ≥ 20 mm Hg for > 5 min) was treated by clinical protocol. Administration times of medications for intracranial hypertension (fentanyl, 3% hypertonic saline, mannitol, and pentobarbital) were prospectively recorded and synchronized with an automated database that collected intracranial pressure and cerebral perfusion pressure every 5 seconds. Intracranial pressure crises confounded by external stimulation or mechanical ventilator adjustments were excluded. Mean intracranial pressure and cerebral perfusion pressure from epochs following drug administration were compared with baseline values using Kruskal-Wallis analysis of variance and Dunn test. Frailty modeling was used to analyze the time to intracranial pressure crisis resolution. Mixed-effect models compared intracranial pressure and cerebral perfusion pressure 5 minutes after the medication versus baseline and rates of treatment failure.

SETTING

A tertiary care children's hospital.

PATIENTS

Children with severe traumatic brain injury (Glasgow Coma Scale score ≤ 8).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We analyzed 196 doses of fentanyl, hypertonic saline, mannitol, and pentobarbital administered to 16 children (median: 12 doses per patient). Overall, intracranial pressure significantly decreased following the administration of fentanyl, hypertonic saline, and pentobarbital. After controlling for administration of multiple medications, intracranial pressure was decreased following hypertonic saline and pentobarbital administration; cerebral perfusion pressure was decreased following fentanyl and was increased following hypertonic saline administration. After adjusting for significant covariates (including age, Glasgow Coma Scale score, and intracranial pressure), hypertonic saline was associated with a two-fold faster resolution of intracranial hypertension than either fentanyl or pentobarbital. Fentanyl was significantly associated with the most frequent treatment failure.

CONCLUSIONS

Intracranial pressure decreased after multiple drug administrations, but hypertonic saline may warrant consideration as the first-line drug for treating intracranial hypertension, as it was associated with the most favorable cerebral hemodynamics and fastest resolution of intracranial hypertension.

[Time point and methods for emergency killing in cattle]

Emergency killing is defined as the killing of injured or ill animals to avoid excessive pain or harm. Decision-making for emergency killing or a prolonged therapy can be difficult and has to be based on the case history and results of the clinical examination contributing to the prognosis, particularly in downer cows. Evaluation of enzyme activities and total bilirubin can be used as additional factors pointing to a guarded prognosis; however, none of these parameters provides a clear cut-off value indicating a poor prognosis and mandatory emergency killing. Euthanasia by intravenous drug application is seen as the least stressful method of killing and should therefore always be the first method of choice for emergency killing in cattle. Drugs containing pentobarbital as well as a combination of three different drugs (T61-Injektionslösung, MSD Animal Health) are available for euthanasia in cattle. All drugs must be administered by a veterinarian. Before application of pentobarbital, an animal should be deeply sedated. The administration of T61 requires anaesthesia of the animal and it is not licensed for use in pregnant animals. Alternative methods for emeragency killing, including captive bolt stunning and the use of firearms, although not regularly performed by veterinarians, should be assessed concerning their correct application and performance. When captive bolt stunning or emergency killing using firearms is performed, the correct position of the device is crucial as well as a quick exsanguination or the application of a pithing rod for the actual killing of the animal after captive bolt stunning. In addition to medical considerations, economic and personal factors contribute to the decision about emergency killing in cattle. Therefore, veterinarians should aim to evaluate each case thoroughly based on personal knowledge and experience, case history, clinical findings and laboratory parameters to avoid prolonged suffering of the animal.

Stability of Fentanyl Citrate, Hydromorphone Hydrochloride, Ketamine Hydrochloride, Midazolam, Morphine Sulfate, and Pentobarbital Sodium in Polypropylene Syringes

PURPOSE

Determine the stability of fentanyl 10 mcg/mL in 0.9% sodium chloride, fentanyl 10 mcg/mL in 5% dextrose, fentanyl 50 mcg/mL, hydromorphone 100 mcg/mL in 0.9% sodium chloride, ketamine 10 mg/mL, midazolam 0.4 mg/mL in 5% dextrose, midazolam 5 mg/mL, morphine 1 mg/mL in 0.9% sodium chloride, morphine 1 mg/mL in 5% dextrose, and pentobarbital 50 mg/mL when stored as single drug entities at room temperature in polypropylene syringes.

METHODS

Four 5 mL samples of each drug and concentration were prepared in 10 mL polypropylene syringes. The samples were stored at ambient room temperature in a locked cabinet. Triplicate determinations of drug concentration for each sample were performed initially, on day 50 or 51, and on day 100 using high-performance liquid chromatography with diode-array detection.

RESULTS

With the exception of the hydromorphone 100 mcg/mL dilution, all compounds were found to contain greater than 95% of their initial concentration remaining at 100 days. Each sample remained clear and colorless when visually inspected.

Milk Collected at Night Induces Sedative and Anxiolytic-Like Effects and Augments Pentobarbital-Induced Sleeping Behavior in Mice

Milk has long been known and used to promote sleep. The sleep-promoting effect of milk has been attributed to its psychological associations (i.e., the memory of a mother giving milk at bedtime) and its rich store of sleep-promoting constituents (e.g., tryptophan). Studies have shown that milk harvested at night (Night milk) contains exceptionally high amounts of tryptophan and melatonin. In the present study, we evaluated the psychopharmacological properties of Night milk, particularly its probable sleep-promoting/enhancing, and anxiolytic effects. Night milk was orally administered to ICR mice at various concentrations (100, 200, or 300 mg/kg). An hour after administration, assessment of its sedative (open-field and rotarod tests) and sedative sleep-potentiating effects (pentobarbital-induced sleeping test) was conducted. For comparison, the effects of Day milk (daytime milking) were also assessed. In addition, the effects of Night milk on anxiety behavior (elevated plus maze [EPM] test) and electroencephalographic (EEG) waves were evaluated. Night milk-treated animals exhibited decreased spontaneous locomotion (open-field test) and impaired motor balance and coordination (rotarod test). Furthermore, Night milk shortened the sleep onset and prolonged the sleep duration induced by pentobarbital sodium. These effects were comparable to that of diazepam. In addition, Night milk significantly increased the percentage of time spent and entries into the open arms of the EPM, indicating that it also has anxiolytic effects. No significant changes in EEG waves were observed. Altogether, these findings suggest that Night milk is a promising natural aid for sleep- and anxiety-related disturbances.

The hepatic circadian clock modulates xenobiotic metabolism in mice

The circadian clock generates daily cycles of gene expression that regulate physiological processes. The liver plays an important role in xenobiotic metabolism and also has been shown to possess its own cell-based clock. The liver clock is synchronized by the master clock in the brain, and a portion of rhythmic gene expression can be driven by behavior of the organism as a whole even when the hepatic clock is suppressed. So far, however, there is relatively little evidence indicating whether the liver clock is functionally important in modulating xenobiotic metabolism. Thus, mice lacking circadian clock function in the whole body or specifically in liver were challenged with pentobarbital and acetaminophen, and pentobarbital sleep time (PBST) and acetaminophen toxicity, respectively, was assessed at different times of day in mutant and control mice. The results suggest that the liver clock is essential for rhythmic changes in xenobiotic detoxification. Surprisingly, it seems that the way in which the clock is disrupted determines the rate of xenobiotic metabolism in the liver. CLOCK-deficient mice are remarkably resistant to acetaminophen and exhibit a longer PBST, while PERIOD-deficient mice have a short PBST. These results indicate an essential role of the tissue-intrinsic peripheral circadian oscillator in the liver in regulating xenobiotic metabolism.

Local O2 Balance in Cerebral Ischemia-Reperfusion Improved during Pentobarbital Compared with Isoflurane Anesthesia

BACKGROUND

Most anesthetics affect cerebral blood flow and metabolism. We compared microregional O2 balance in cerebral ischemia-reperfusion during pentobarbital and isoflurane anesthesia.

METHODS

After 1 hour of middle cerebral artery occlusion and a 2-hour reperfusion under isoflurane (1.4%, n = 14) or pentobarbital (50 mg/kg, n = 14) anesthesia in rats, regional cerebral blood flow using (14)C-iodoantipyrine autoradiography, microregional arterial and venous O2 saturation (20-60 μm in diameter) using cryomicrospectrophotometry, and the size of cortical infarct were determined.

RESULTS

Ischemia-reperfusion decreased the average cortical venous O2 saturation in both pentobarbital and isoflurane groups (P < .0001), which was higher (P < .05) with pentobarbital despite a similar average regional cerebral blood flow and O2 consumption. The heterogeneity of venous O2 saturation reported as a coefficient of variation (100 × standard deviation/mean) was smaller (P < .005) with pentobarbital than that with isoflurane (7.5 versus 16.1). The number of veins with low venous O2 saturation (<50%) was smaller (P < .005) with pentobarbital (5 of 80 versus 24 of 80). The percentage of cortical infarct in total cortex was smaller with pentobarbital (5.2 ± 2.5% versus 12.3 ± 2.6%, P < .001).

CONCLUSIONS

In the cerebral ischemic-reperfused cortex, the average venous O2 saturation was higher, and its heterogeneity and the number of veins with low O2 saturation were smaller under pentobarbital than isoflurane anesthesia. This improvement in microregional O2 balance with pentobarbital was accompanied by the reduced cortical infarct. Our data suggest that the neurologic outcome could vary during cerebral ischemia-reperfusion depending on the anesthetics used.

Rescue of Methyl-CpG Binding Protein 2 Dysfunction-induced Defects in Newborn Neurons by Pentobarbital

Rett syndrome is a neurodevelopmental disorder that usually arises from mutations or deletions in methyl-CpG binding protein 2 (MeCP2), a transcriptional regulator that affects neuronal development and maturation without causing cell loss. Here, we show that silencing of MeCP2 decreased neurite arborization and synaptogenesis in cultured hippocampal neurons from rat fetal brains. These structural defects were associated with alterations in synaptic transmission and neural network activity. Similar retardation of dendritic growth was also observed in MeCP2-deficient newborn granule cells in the dentate gyrus of adult mouse brains in vivo, demonstrating direct and cell-autonomous effects on individual neurons. These defects, caused by MeCP2 deficiency, were reversed by treatment with the US Food and Drug Administration-approved drug, pentobarbital, in vitro and in vivo, possibly caused by modulation of γ-aminobutyric acid signaling. The results indicate that drugs modulating γ-aminobutyric acid signaling are potential therapeutics for Rett syndrome.

Comparison of dexmedetomidine with pentobarbital for pediatric MRI sedation

BACKGROUND AND OBJECTIVE

Intravenous pentobarbital has been used in the past to sedate pediatric patients in preparation for MRI; however, the drug has unpredictable sedation time. Dexmedetomidine, because of its short half-life, is gaining popularity for pediatric MRI sedation in settings where the use of propofol is restricted for nonanesthesiologists. The objective was to compare induction time, recovery time, total sedation time, sedation failure rate, and adverse outcomes of patients sedated with pentobarbital and dexmedetomidine in preparation for pediatric MRI.

METHODS

We reviewed a sedation database that contains clinical data for all children undergoing MRI studies while sedated with pentobarbital or dexmedetomidine between May 15, 2008, and October 30, 2010.

RESULTS

During the study period, 281 sedations were induced in preparation for MRI (160 with pentobarbital, and 121 with dexmedetomidine). The 2 groups were comparable with regard to age, weight, gender, and American Society of Anesthesiologists status. The dexmedetomidine group had a significantly shorter recovery time (39 ± 21 vs 49 ± 27 minutes [P = .002]) and total sedation time (107 ± 28 vs 157 ± 44 minutes [P = .0001]). Induction time was similar between the groups. The adverse event rate for the study population was 3%.

CONCLUSIONS

Dexmedetomidine and pentobarbital can both be used successfully for MRI sedation in children. However, dexmedetomidine had a significantly shorter recovery time and total sedation time in our population.

Influence of anesthetic agent, depth of anesthesia and body temperature on cardiovascular functional parameters in the rat

Sedating animals is sometimes necessary in experimental research. This paper presents and discusses the influence of four of the most common anesthetic agents on cardiovascular parameters in rats. We also studied the influence of body temperature. Ten-week-old Sprague-Dawley rats were anesthetized with either isoflurane, pentobarbital, ketamine/xylazine or tiletamine/zolazepam (n = 12 in each group). A pressure-sensing catheter was placed in the right carotid artery for the continuous measurement of arterial pressure, and echocardiography was performed. Indices of cardiac function were significantly higher in the tiletamine/zolazepam rats compared with the other groups. Heart rate was highest but stroke volume lowest with pentobarbital. Left ventricular diastolic dimension was lower in the pentobarbital and tiletamine/zolazepam rats compared with the isoflurane or ketamine/xylazine rats. Intraventricular diastolic pressure was similar in all groups whereas intraventricular systolic pressure, as well as both systolic and diastolic aortic pressures, was significantly higher in the tiletamine/zolazepam rats compared with the other groups. No hemodynamic indices differed significantly among the isoflurane, pentobarbital and ketamine/xylazine rats. Lowering body temperature significantly reduced heart rate and cardiac output but had no apparent effect on hemodynamic parameters. In conclusion, although cardiac functional parameters differed between the different anesthetic agents in ways that could be of relevance to the researcher, they may all have a role in experimental cardiology. Importantly, tiletamine/zolazepam anesthesia resulted in significantly higher indices of cardiac function and elevated blood pressures compared with the other anesthetic agents, a finding that should be kept in mind when interpreting data obtained in rats sedated on this regimen.

Complications of three deep sedation methods for magnetic resonance imaging

Background:

Propofol and pentobarbital are commonly used to sedate children undergoing magnetic resonance imaging (MRI).

Aim/Objective:

To compare the safety of three types of sedation: intravenous propofol (PROP), mixed pentobarbital/propofol (PENT), and mixed pentobarbital group requiring supplemental sedation (PENT SUPP) regimens in pediatric patients following deep sedation (DS) for noncardiac MRI.

Materials and Methods:

We conducted a case-control study matching 619 cases with complications with 619 controls using data from our institution's sedation database for children deeply sedated for noncardiac MRI. Cases were defined as patients with any complication and we characterized complications from cases, and used a conditional logistic regression model to assess the association between three DS methods and occurrence of complications after adjusting for confounding variables.

Results:

We found that complications occurred in association with 794 (10.1%) of the 7,839 DSs performed for MRI between 1998 and 2008. Of the 794 cases, 619 cases met inclusion criteria for the study. Among the 619 cases that met inclusion criteria, 24 (0.3% of 7,839 DSs total) were associated with major complications. Type of sedation was significantly associated with the occurrence of complications, and the PENT group was associated with decreased odds of complications when compared to the PROP regimen (OR 0.68; 95% CI 0.46, 0.98; P=0.040) and compared to the PENT SUPP group (OR 0.60; 95% CI 0.31, 0.89; P<0.0001).

Conclusions:

DS with a pentobarbital technique was associated with decreased odds for complications when compared to a propofol-based technique or a pentobarbital technique requiring supplemental sedation.

An unusual case of relay pentobarbital toxicosis in a dog

Sodium pentobarbital and phenytoin are common constituents of veterinary euthanasia solutions in the United States. Relay, or secondary, barbiturate toxicosis has been reported in carnivorous animals that have fed from the carcasses of euthanized livestock. This case report presents barbiturate toxicosis in a dog. A 2-year-old female spayed Australian shepherd presented comatose 2 h after ingesting an unknown substance on the beach. The material was retrieved from the stomach by gastric lavage and visually identified as fish or other animal tissue. The dog recovered with symptomatic and supportive therapy and was released on the third day of hospitalization. Tissue found on the beach near where the dog walked and a urine sample from the dog were analyzed by gas chromatography/mass spectrometry. Both samples were positive for pentobarbital and phenytoin. The tissue was consistent with mammalian blubber based on gross and histological examination. Three weeks previously, a juvenile humpback whale had stranded on the beach where the dog had ingested the unknown substance. The whale had been euthanized with a barbiturate solution, necropsied, and removed from the beach. It was not definitively determined that the pentobarbital-containing blubber ingested by the dog was from the euthanized whale, but that was the most likely source. Although attempts were made to remove the whale's remains from the beach, practical considerations made complete removal challenging, if not impossible.

Reinforcement magnitude modulation of rate dependent effects in pigeons and rats

Response rate can influence the behavioral effects of many drugs. Reinforcement magnitude may also influence drug effects. Further, reinforcement magnitude can influence rate-dependent effects. For example, in an earlier report, we showed that rate-dependent effects of two antidepressants depended on reinforcement magnitude. The ability of reinforcement magnitude to interact with rate-dependency has not been well characterized. It is not known whether our previous results are specific to antidepressants or generalize to other drug classes. Here, we further examine rate-magnitude interactions by studying effects of two stimulants (d-amphetamine [0.32-5.6 mg/kg] and cocaine [0.32-10 mg/kg]) and two sedatives (chlordiazepoxide [1.78-32 mg/kg] and pentobarbital [1.0-17.8 mg/kg]) in pigeons responding under a 3-component multiple fixed-interval (FI) 300-s schedule maintained by 2-, 4-, or 8-s of food access. We also examine the effects of d-amphetamine [0.32-3.2 mg/kg] and pentobarbital [1.8-10 mg/kg] in rats responding under a similar multiple FI300-s schedule maintained by 2- or 10- food pellet (45 mg) delivery. In pigeons, cocaine and, to a lesser extent, chlordiazepoxide exerted rate-dependent effects that were diminished by increasing durations of food access. The relationship was less apparent for pentobarbital, and not present for d-amphetamine. In rats, rate-dependent effects of pentobarbital and d-amphetamine were not modulated by reinforcement magnitude. In conclusion, some drugs appear to exert rate-dependent effect which are diminished when reinforcement magnitude is relatively high. Subsequent analysis of the rate-dependency data suggest the effects of reinforcement magnitude may be due to a diminution of drug-induced increases in low-rate behavior that occurs early in the fixed-interval.

Effects of drugs and drug combinations in pigeons trained to discriminate among pentobarbital, dizocilpine, a combination of these drugs, and saline

Drugs with multiple actions can have complex discriminative-stimulus properties. An approach to studying such drugs is to train subjects to discriminate among drug combinations and individual drugs in the combination so that all of the complex discriminative stimuli are present during training. In the current experiments, a four-choice procedure was used to train pigeons to discriminate among dizocilpine (noncompetitive NMDA receptor blocker), pentobarbital (GABA(A) receptor agonist), a fixed-dose combination of these two drugs, and saline. Following extended training, low doses of pentobarbital or dizocilpine administered alone produced saline-appropriate responding. Higher doses of pentobarbital produced responding on the pentobarbital-appropriate key and higher doses of dizocilpine produced responding on the dizocilpine key. Administering the lowest doses of pentobarbital and dizocilpine together resulted in responding on the saline-appropriate key. Increasing the dose of pentobarbital in the presence of low doses of dizocilpine produced responding primarily on the pentobarbital-appropriate key; increasing the dose of dizocilpine in the presence of the lowest dose of pentobarbital produced responding primarily on the dizocilpine-appropriate key. Combining the higher doses of pentobarbital and dizocilpine resulted in responding primarily on the drug-combination key. Low doses of phencyclidine or ethanol produced responding on the saline-appropriate key, but intermediate doses resulted in individual subjects responding predominately on either the pentobarbital key, the dizocilpine key, or the drug-combination key depending on the subject. After the highest dose of phencyclidine or ethanol, most subjects responded predominantly on the drug-combination key. Low doses of other drugs tested produced responding on the saline-appropriate key. With the highest diazepam doses responding was largely confined to the pentobarbital-appropriate key. The highest doses of dextromethorphan or dextrorphan resulted in responding on the dizocilpine key more frequently than on other keys. Across a range of doses, morphine produced responding predominantly on the saline key. The results using the four-key procedure emphasized the role of both GABA(A) and NMDA receptors in the complex discriminative stimulus properties of phencyclidine and of ethanol.

Noninvasive real-time measurement of nasal mucociliary clearance in mice by pinhole gamma scintigraphy

Mucociliary clearance (MCC) is the key defense mechanism in the upper airways, as the removal of debris-laden mucus in the sinuses completely depends on MCC. So far, how the nasal MCC is regulated remains unknown. Recently, mice deficient in genes encoding the components of MCC apparatus have been generated, which will allow investigators to conduct more in-depth nasal MCC studies. However, the methodology necessary to comprehensively evaluate the nasal MCC in this species is not well established. We therefore developed a novel method to measure nasal MCC in live mice using pinhole gamma camera. Insoluble radiolabeled particles were delivered into the noses of lightly anesthetized mice. The nasal clearance of these particles was measured continuously in a real-time manner. The effect of three different anesthetics-avertin, pentobarbital, and isoflurane-on nasal MCC was also determined. In mice anesthetized by 1.1% isoflurane, radiolabeled particles were immediately moved into the oropharynx, which was significantly accelerated by the treatment of hypertonic but not isotonic saline. According to the clearance rate, the mouse nasal MCC presented two distinct phases: a rapid phase and a slow phase. In addition, we found that isoflurane had a very small inhibitory effect on nasal MCC vs. both avertin and pentobarbital. This was further supported by its dose response. Collectively, we have developed a noninvasive method to monitor the real-time nasal MCC in live mice under physiological conditions. It provides more comprehensive evaluation on nasal MCC rather than assessing a single component of the MCC apparatus in isolation.