Comparison of oral Midazolam-Ketamine and Midazolam-Promethazine as sedative agents in pediatric dentistry

BACKGROUND

Investigation was designed to evaluate the behavioral changes in children receiving dental treatment while they have been administered combination of Midazolam/Ketamine or Midazolam/Promethazine.

MATERIALS AND METHODS

This was a randomized double blind clinical trial with cases being selected from those uncooperative children aged 2 to 6 years from those referred for treatment under general anesthesia. Anxiety score of all cases were recorded before any attempt using Frankel's anxiety scoring system with those in negative category being included. Cases with at least a pair of similar size cavities on similar teeth were selected with each tooth being randomly allocated for one sedative regimen group. To avoid sequence effect, half of the patients received one regimen at the first visit while the other half received the other regimen as the first. Each case served as control for him or herself to reduce influencing factors. Child's reaction was recorded before, during, and at the end of dental procedure. SO2 as well as Pulse rate were recorded as the most critical vital signs. Collected data were then analyzed using analysis of variance (ANOVA) and paired t-test.

RESULTS

Patients' mean age was 3.5 years with 43% being male. Only 10% of the Ketamine/Midazolam group showed considerable amount of change in their behavior with a statistical significant difference being presented (P=0.029).

CONCLUSION

Under the current circumstances, Ketamine/Midazolam combination provided sufficient sedative effect in lower doses. However, Midazolam/Promethazine combination did not produce similar results.

Comparison of dexmedetomidine and three different doses of midazolam in preoperative sedation

Background:

This study was conducted to compare the efficacy and effects of dexmedetomidine and midazolam in preoperative sedation.

Materials and Methods:

A total of 125 patients in American Society of Anaesthesiologists (ASA) I-II were divided into three groups: Group I (n = 40) for controls, Group II (n = 40) for Dexmedetomidine (1 μg/kg), and group III was the midazolam group (n = 45). Group III was further divided into three subgroups according to the doses of midazolam: Group IIIA (n = 15) received 0.02 mg/kg, group IIIB (n = 15) received 0.04 mg/kg, and group IIIC (n = 15) received 0.06 mg/kg of midazolam. Drugs were infused over a 10-minute period with appropriate monitoring. Ramsay and visual analog scores, for sedation and anxiety, respectively, and mean arterial pressure, heart rate, and SpO₂ measurement, including respiratory rates were recorded, every 5 minutes for 30 minutes following infusion.

Results:

There was marked sedation and a decrease in anxiety in groups II and IIIC (P < 0.01). Mean arterial pressure (MAP) and heart rate (HR) decreased significantly in group II (P < 0.01 and P < 0.05, respectively), but there was no associated hypotension (MAP <60 mm Hg) or bradycardia (HR <50 bpm) (P < 0.05). Respiratory rates and SpO₂ values decreased in groups II, IIIA, IIIB, and IIIC. The differences in respiratory rates were not significant (P > 0.05); however, decrease in SpO₂ was significant in group IIIC (P < 0.01).

Conclusions:

Dexmedetomidine was as effective as higher doses of midazolam in sedation. The hemodynamic and respiratory effects were minimal. Although dexmedetomidine caused significant decrease in the blood pressure and heart rate, it probably just normalized increased levels caused by preoperative stress.

The discriminative stimulus effects of midazolam are resistant to modulation by morphine, amphetamine, dizocilpine, and γ-butyrolactone in rhesus monkeys

RATIONALE

Although abuse of benzodiazepines alone is uncommon, it is high in polydrug abusers, including those who primarily use opioids or stimulants.

OBJECTIVES

This study investigated whether drugs that are abused (e.g., amphetamine) or drugs that have mechanisms of action similar to abused drugs (e.g., morphine) alter the discriminative stimulus effects of the benzodiazepine midazolam.

METHODS

Three rhesus monkeys discriminated 0.56 mg/kg of midazolam while responding under a fixed-ratio 10 schedule of food presentation. Dose-effect curves were determined for midazolam alone and in the presence of morphine (opioid receptor agonist), amphetamine (dopamine receptor indirect agonist), dizocilpine (N-methyl-D: -aspartic acid receptor antagonist), or γ-butyrolactone (prodrug of γ-hydroxybutyrate, which acts primarily at GABA(B) receptors).

RESULTS

Doses of midazolam larger than 0.32 mg/kg produced ≥80% midazolam-lever responding. When administered alone, morphine, amphetamine, dizocilpine, and γ-butyrolactone did not produce midazolam-lever responding, although large doses of each drug eliminated responding; when administered in combination with midazolam, they did not alter the discriminative stimulus effects of midazolam up to doses that markedly decreased response rates.

CONCLUSIONS

The current study demonstrates a lack of modulation of the discriminative stimulus effects of midazolam by morphine, amphetamine, dizocilpine, and γ-butyrolactone. Other effects of benzodiazepines, such as their reinforcing effects, might be altered by these other drugs, or benzodiazepines might modulate the discriminative stimulus or reinforcing effects of the other drugs, which might contribute to the relatively high incidence of benzodiazepine abuse among polydrug abusers.

The effect of propranolol and midazolam on the reconsolidation of a morphine place preference in chronically treated rats

A stable memory can be disrupted if amnestic treatment is applied in conjunction with memory reactivation. Recent findings in the conditioned place preference (CPP) model suggest that blocking reconsolidation attenuates the ability of environmental cues to induce craving and relapse in drug addicts, but the impact of prior physical dependence has not been described. We examined the effect of post-reactivation amnestic treatment on reconsolidation of a CPP for morphine, in animals naïve to morphine, under chronic morphine experience or abstinent. Chronic morphine experience was induced by escalating doses of morphine from 10 mg/kg/day (s.c.), and maintained on 30 mg/kg/day during the course of conditioning and reactivation procedures, or conditioning alone. Naïve and morphine-experienced animals were trained in a three-compartment apparatus by four morphine (5 mg/kg, s.c.) and four saline experiences paired with either of two large conditioning compartments. The memory was then reactivated by a CPP test, and immediately afterward animals received an injection of the beta-adrenergic antagonist propranolol (10 mg/kg, s.c.), the GABAa agonist midazolam (1 mg/kg, i.p.), or saline. Morphine-naïve rats received only a single reconsolidation-blocking treatment (Experiment 1), while chronic morphine rats were given eight reactivation sessions each followed by amnestic treatment, either before (Experiment 2) or after 10 days of withdrawal (Experiment 3). Propranolol and midazolam disrupted reconsolidation in morphine-naïve rats, but failed to disrupt the CPP when rats were trained under chronic morphine treatment, even if they were recovered from chronic opiate exposure before reactivation. In fact, propranolol increased the preference for the drug-paired context in animals trained while maintained on chronic morphine. Midazolam had little effect. Morphine experience may produce neurochemical changes which alter memory storage processes and reduce the impact of amnestic treatments on reconsolidation.

A novel elevated plus-maze procedure to avoid the one-trial tolerance problem

The elevated plus-maze (EPM) test is one of the most commonly used behavioral assays to evaluate anxiety-related behavior in rodents. It is an economic test (5 min duration) without prior conditioning of the animals. The critical measure for anxiety is the time spent in the open arms of the maze. A confounding problem of the EPM is the so called one-trial tolerance (OTT), characterized by a marked decrease of open arm exploration in spite of treatment with anxiolytic acting benzodiazepines upon re-exposure to the EPM. This consistent finding is often raised as an evidence for the inappropriateness to re-test rodents in the EPM. However, a reliable re-test paradigm would broaden the usability and effectiveness of this test. Therefore, we tested how an extension of the inter-trial interval to 28 days (instead of the usual 24 h), and an additional change of the testing room would affect the open arm time and other behaviors on the EPM. In two experiments, drug-naive Wistar rats were exposed to the EPM on trial 1, and treated intraperitoneally with either vehicle or midazolam (0.25 mg/kg) 30 min before trial 2. Then, trial 2 (28 days after trial 1) was carried out in either the same testing room (Experiment 1) or in another unfamiliar room (Experiment 2). Twenty-eight days after trial 1 the open arm time of the rats in the vehicle treated control rats of both experimental groups was comparable to that of the first trial, independent of the testing room. Most importantly, we found that the treatment with the benzodiazepine midazolam had a significantly anxiolytic-like (i.e., increase of open arm time) effect in trial 2 only when conducted in the previously unfamiliar testing room (Experiment 2). We suggest that in order to reliably re-test the EPM and to prevent confounding effects due to the OTT, an inter-trial interval of 28 days and a change in testing rooms reinstates anxiolytic-like actions of benzodiazepines.

Drug interaction leading to prolonged sedation in a postoperative high risk coronary bypass surgery patient

Use of midazolam infusion in mechanically ventilated patient is an established practice in critical care. In our case, the use of erythromycin as a prokinetic agent for better tolerance of enteral feeding and paralytic ileus led to an interaction between midazolam and erythromycin, which resulted in prolonged and deeply sedated patient. In a critically ill patient, there is always a possibility of multiple drug interactions. It is important to understand them and they should be considered before starting new medication.

Status epilepticus

Status epilepticus (SE) is a medical emergency associated with significant morbidity and mortality. SE is defined as a continuous seizure lasting more than 30 min, or two or more seizures without full recovery of consciousness between any of them. Based on recent understanding of the pathophysiology, it is now considered that any seizure that lasts more than 5 min probably needs to be treated as SE. GABAergic mechanisms play a crucial role in terminating seizures. When the seizure persists, GABA-mediated mechanisms become ineffective and several other putative mechanisms of seizure suppression have been recognized. Early treatment of SE with benzodiazepines, followed if necessary by fosphenytoin administration, is the most widely followed strategy. About a third of patients with SE may have persistent seizures refractory to the first-line medications. They require aggressive management with second-line medications such as barbiturates, propofol, or other agents. In developing countries where facilities for assisted ventilation are not readily available, it may be helpful to use nonsedating antiepileptic drugs (such as sodium valproate, levetiracetam, or topiramate) at this stage. It is important to recognize SE and institute treatment as early as possible in order to avoid a refractory state. It is equally important to attend to the general condition of the patient and to ensure that the patient is hemodynamically stable. This article reviews current knowledge regarding the management of convulsive SE in adults.

Sevoflurane-emergence agitation: Effect of supplementary low-dose oral ketamine premedication in preschool children undergoing dental surgery

BACKGROUND AND OBJECTIVES

The use of sevoflurane in pediatric anesthesia, which could enable a more rapid emergence and recovery, is complicated by the frequent occurrence of post-anesthesia agitation. This study aims to test the efficacy of adding a low dose of ketamine orally, as a supplement to the midazolam-based oral premedication for reducing sevoflurane-related emergence agitation.

MATERIALS AND METHODS

Ninety-two preschool children, aged between two and six years, with an American Society of Anesthesiologists physical status I or II, scheduled for elective dental filling and extractions under general anesthesia were included. The patients were allocated into two groups: Group M (46 patients) received oral midazolam 0.5 mg/kg, mixed with ibuprofen 10 mg/kg, while group KM (46 patients) received a similar premedication mixture, in addition to ketamine 2 mg/kg. The acceptance of the drug mixture, the onset of action, and the occurrence of vomiting were monitored over the next 30 minutes. Induction of anesthesia was carried out using sevoflurane 8 Vol% in 100% oxygen via face mask. Anesthesia was maintained with sevoflurane 1.5-2 Vol% in an oxygen-nitrous oxide mixture. After extubation, the standard scoring scale was used for assessing the quality of emergence. Agitation parameters were measured using a five-point scale. Agitated children were managed by giving intravenous increments of fentanyl 1 mug/ kg. The time of hospital discharge allowance was recorded.

RESULTS

Drug palatability, vomiting, and onset of action of premedication; showed no significant differences between both groups. Time of eye opening after discontinuation of sevoflurane showed no significant differences between both groups. Postoperative agitation score and rescue fentanyl consumption were higher in group M than in group KM on admission to the PACU (P < 0.01). The time of hospital discharge allowance in group M was longer than in group KM (P < 0.05).

CONCLUSION

Adding a low dose of oral ketamine to midazolam-based oral premedication in preschool children undergoing dental surgery reduced sevoflurane-related emergence agitation without delaying discharge.

Commonly used intravenous anesthetics decrease bladder contractility: An in vitro study of the effects of propofol, ketamine, and midazolam on the rat bladder

Aim:

This study was designed to test the hypothesis that propofol, ketamine, and midazolam could alter the contractile activity of detrusor smooth muscle.

Materials and Methods:

Four detrusor muscle strips isolated from each rat bladder (n = 12) were placed in 4 tissue baths containing Krebs-Henseleit solution. The carbachol (10 ⁻⁸to 10⁻⁴mol/L)-induced contractile responses as well as 5, 10, 20, 30, 40, 50 Hz electrical field stimulation (EFS)-evoked contractile responses of the detrusor muscles were recorded using isometric contraction measurements. After obtaining basal responses, the in vitro effects of propofol, ketamine, midazolam (10⁻⁵ to 10⁻³ mol/L), and saline on the contractile responses of the detrusor muscle strips were recorded and evaluated.

Results:

All the 3 drugs reduced the carbachol-induced and/or EFS-evoked contractile responses of rat detrusor smooth muscles in different degrees. Midazolam (10⁻⁴ to 10⁻³ mol/L) caused a significant decrease in the contractile responses elicited by either EFS or carbachol (P=0.000−0.013). Propofol (10⁻³mol/L) caused a decrease only in EFS-evoked contractile responses (P=0.001−0.004) and ketamine (10⁻³mol/L) caused a decrease only in carbachol-induced contractile responses (P=0.001−0.034).

Conclusion:

We evaluated the effects of the 3 different intravenous anesthetics on detrusor contractile responses in vitro and found that there are possible interactions between anesthetic agents and detrusor contractile activity. The depressant effects of midazolam on the contractile activity were found to be more significant than ketamine and propofol. Despite the necessity of further studies, it could be a piece of wise advice to clinicians to keep the probable alterations due to intravenous anesthetics in mind, while evaluating the results of urodynamic studies in children under sedation.

Comparing the discriminative stimuli produced by either the neuroactive steroid pregnanolone or the benzodiazepine midazolam in rats

RATIONALE

Neuroactive steroids might be therapeutic alternatives for benzodiazepines because they have similar anxiolytic, sedative, and anticonvulsant effects, and their actions at different modulatory sites on γ-aminobutyric acid(A) (GABA(A)) receptors might confer differences in adverse effects.

OBJECTIVES

This study used drug discrimination to compare discriminative stimuli produced by positive GABA(A) modulators that vary in their site of action on GABA(A) receptors.

METHODS

Two groups of rats discriminated either 3.2 mg/kg of pregnanolone or 0.56 mg/kg of midazolam from vehicle while responding under a fixed ratio 10 schedule of food presentation.

RESULTS

Pregnanolone, midazolam, and flunitrazepam produced ≥ 80% drug-lever responding in both groups; each drug was more potent in rats discriminating pregnanolone. Pentobarbital produced ≥ 80% drug-lever responding in all rats discriminating pregnanolone, and in 1/3 of the rats discriminating midazolam with larger doses decreasing response rates to <20% of control. Morphine and ketamine produced predominantly saline-lever responding in both groups. Flumazenil antagonized midazolam and flunitrazepam in both groups; slopes of Schild plots were not different from unity, and pA (2) values for flumazenil ranged from 5.86 to 6.09. Flumazenil did not attenuate the discriminative stimulus effects of pregnanolone.

CONCLUSIONS

The midazolam and pregnanolone discriminative stimuli were qualitatively similar, although the effects of pentobarbital were not identical in the two groups. Although acute effects of midazolam and pregnanolone are similar, suggesting that neuroactive steroids might retain the therapeutic effects of benzodiazepines, differences emerge during chronic treatment, indicating that neuroactive steroids might produce fewer adverse effects than benzodiazepines.

Comparison of the effects of propofol and midazolam on inflammation and oxidase stress in children with congenital heart disease undergoing cardiac surgery

PURPOSE

To investigate and compare the effects of propofol and midazolam on inflammation and oxidase stress in children with congenital heart disease undergoing cardiac surgery.

MATERIALS AND METHODS

Thirty-two ASA class I-II children with congenital heart disease undergoing cardiac surgery were randomly divided into two groups: propofol combined with low dose fentanyl (PF group, n = 16) and midazolam combined with low dose fentanyl (MF group, n = 16). Tracheal extubation time and length of Intensive Care Unit (ICU) stay were recorded. Blood samples were taken before operation (T₀), at 2 h after release of the aorta cross-clamp (T₃) and at 24 h after operation (T₄) to measure interleukin 6 (IL-6), IL-8, superoxide dismutase (SOD) and malondialdehyde (MDA) levels. Myocardium samples were collected at 10-20 min after aorta cross-clamp (T₁) and at 10-20 min after the release of the aorta cross-clamp (T₂) to detect heme oxygenase-1 (HO-1) expression.

RESULTS

Tracheal extubation time and length of ICU stay in PF group were significantly shorter than those of the MF group (p < 0.05, respectively). After cardiopulmonary bypass, IL-6, IL-8 and MDA levels were significantly increased, and the SOD level was significantly reduced in both two groups, but PF group exhibited lower IL-6, IL-8 and MDA levels and higher SOD levels than the MF group (p < 0.05, respectively). The HO-1 expression in the PF group was significantly higher than that in MF group at the corresponding time points (p < 0.05, respectively).

CONCLUSION

Propofol is superior to midazolam in reducing inflammation and oxidase stress and in improving post-operation recovery in children with congenital heart disease undergoing cardiac surgery.

Is premedication with midazolam more effective by the sublingual than the oral route?

Background:

In this study, we compared the sedative effects of sublingual midazolam solution with the oral tablet as premedication. Sixty pediatric patients of ASA physical status I and II were randomly selected to receive either 0.5 mg/kg of tablet or 0.5 mg/kg of sublingual solution of midazolam as premedication, about 45 min before elective surgery.

Materials and Methods:

There were 30 patients in each group. In Group I, the patients received premedication in the form of oral midazolam tablet 0.5 mg/kg. In Group II, the patients received midazolam solution 0.5 mg/kg. The degree of sedation and ease of separation was assessed according to the Niall C. Wilton scale and the procedure of Davis Peter, respectively. The time for complete drug dissolution was noted in both the groups. Then, the patients were interviewed regarding their acceptance of taste.

Results:

The sedation scores in the sublingual group were higher than in the oral group at 30 and 45 min after drug administration (P=0.0134 and P=0.0157). 66.6% of the patients in the sublingual group found it satisfactory as compared to 53.3% in the case of group receiving tablet.

Conclusion:

Thus, from the present study, it is concluded that premedication with midazolam is more effective by the sublingual than the oral route in children.

Antiemetic effects of midazolam added to fentanyl-ropivacaine patient-controlled epidural analgesia after subtotal gastrectomy: A prospective, randomized, double-blind, controlled trial

BACKGROUND

Nausea and vomiting are frequent adverse effects of patient-controlled epidural analgesia (PCEA) with opioids.

OBJECTIVE

This study was designed to assess the antiemetic effect of midazolam added to fentanyl-ropivacaine PCEA.

METHODS

In a prospective, randomized, double-blind, controlled trial, smoking patients with gastric cancer undergoing elective subtotal gastrectomy were evenly allocated to 1 of 2 treatment groups to manage postoperative pain: 0.2% ropivacaine mixed with fentanyl 4 μg/mL and midazolam 0.2 mg/mL (test group) or 0.2% ropivacaine mixed with fentanyl 4 μg/mL (control group). The PCEA infusion was set to deliver 4 μL/h of the study solution, with a bolus of 2 mL per demand and a 15-minute lockout time. The incidence of postoperative nausea and vomiting (PONV), pain intensity, sedation score, usage of rescue analgesia and rescue antiemetic, respiratory depression, urinary retention, and pruritus were recorded at 2, 6, 12, 24, 48, and 72 hours after surgery. Total infused volume of PCEA at 72 hours after surgery was measured.

RESULTS

A total of 60 patients were approached and randomized to treatment. No patients were excluded by exclusion criteria and all enrolled patients completed this study. Incidence of nausea (7% vs 33%; P = 0.02) in the test group was significantly lower than in the control group. The overall frequency of PONV in the test group was significantly less than that of the control group (7% vs 40%; P = 0.006). In addition, the mean (SD) infused volume of PCEA in the test group was significantly lower than that in the control group (392.3 [68.9] vs 351.2 [49.8] mL; P = 0.01). However, there were no significant differences in pain intensity, usage of rescue antiemetics and rescue analgesics, and mild pruritus between groups. No patient reported moderate or severe sedation, respiratory depression, or hypoxemia. In addition, there were no severe adverse events.

CONCLUSIONS

Midazolam added to fentanyl-ropivacaine PCEA was associated with a significant reduction in the incidence of PONV compared with fentanyl-ropivacaine alone, and a significant decrease in the amount of PCEA administered without a significant increase in adverse events in these patients who underwent subtotal gastrectomy.

Neural inhibition enables selection during language processing

Whether grocery shopping or choosing words to express a thought, selecting between options can be challenging, especially for people with anxiety. We investigate the neural mechanisms supporting selection during language processing and its breakdown in anxiety. Our neural network simulations demonstrate a critical role for competitive, inhibitory dynamics supported by GABAergic interneurons. As predicted by our model, we find that anxiety (associated with reduced neural inhibition) impairs selection among options and associated prefrontal cortical activity, even in a simple, nonaffective verb-generation task, and the GABA agonist midazolam (which increases neural inhibition) improves selection, whereas retrieval from semantic memory is unaffected when selection demands are low. Neural inhibition is key to choosing our words.

Previous stress attenuates the susceptibility to Midazolam's disruptive effect on fear memory reconsolidation: influence of pre-reactivation D-cycloserine administration

It is well known that, under certain boundary conditions, the retrieval of a stable consolidated memory results into a labile one. During this unstable phase, memory can be vulnerable to interference by a number of pharmacological agents, including benzodiazepines. One of the goals of this study was to evaluate the vulnerability to midazolam (MDZ) after reactivation of recent and remote contextual fear memories in animals that experienced a stressful situation before learning. Animals were subjected to a restraint session and trained in a contextual fear paradigm the following day; consolidated memories were reactivated at different times after learning and different MDZ doses (1.5, 3.0 mg/kg) were administered to rats after reactivation. Our results show that MDZ did not affect memory reconsolidation in older-than-one-day memories of stressed animals, even after the administration of a higher MDZ dose and a longer reactivation session (5 min). In contrast, MDZ was effective in blocking reconsolidation at all memory ages in unstressed animals. In addition, the current research investigated whether activating NMDA sites before reactivation promotes the destabilization of resistant memories such as those of stressed animals. We tested the influence of pre-reactivation D-cycloserine (DCS), a partial NMDA agonist, on MDZ's effect on fear memory reconsolidation in stressed animals. Our findings indicate that DCS before reactivation promotes retrieval-induced lability in resistant memory traces, as MDZ-induced memory impairment in stressed rats became evident with pre-reactivation DCS but not after pre-reactivation sterile isotonic saline.

Interactions between Delta(9)-tetrahydrocannabinol and mu opioid receptor agonists in rhesus monkeys: discrimination and antinociception

RATIONALE

Opioid receptor agonists can enhance some effects of cannabinoid receptor agonists, and cannabinoid receptor agonists can enhance some effects of opioid receptor agonists; however, the generality of these interactions is not established.

OBJECTIVE

This study examined interactions between the discriminative stimulus and antinociceptive effects of mu opioid receptor agonists and Delta(9)-tetrahydrocannabinol (THC) in rhesus monkeys.

RESULTS

Neither heroin nor morphine (intravenous (i.v.) or subcutaneous (s.c.)) altered the discriminative stimulus effects of THC in monkeys (n = 5) discriminating 0.1 mg/kg THC i.v. In contrast, THC (s.c.) markedly attenuated the discriminative stimulus effect of morphine and heroin in nondependent monkeys (n = 4) discriminating 1.78 mg/kg morphine s.c. Doses of THC that attenuated the discriminative stimulus effects of morphine in nondependent monkeys failed to modify the discriminative stimulus effects of morphine in morphine-dependent (5.6 mg/kg/12 h) monkeys (n = 4) discriminating 0.0178 mg/kg naltrexone s.c. THC also failed to modify the discriminative stimulus effects of naltrexone in morphine-dependent monkeys or the effects of midazolam in monkeys (n = 4) discriminating 0.32 mg/kg midazolam s.c. Doses of THC (s.c.) that attenuated the discriminative stimulus effects of morphine in nondependent monkeys enhanced the antinociceptive effects of morphine (s.c.) in nondependent monkeys. While mu receptor agonists did not alter the discriminative stimulus effects of THC, THC altered the effects of mu receptor agonists in a context-dependent manner.

CONCLUSION

That the same doses of THC enhance, attenuate, or do not affect morphine, depending on the condition, suggests that attenuation of morphine by THC can result from perceptual masking rather than common pharmacodynamic mechanisms or pharmacokinetic interactions.

Preoperative warming combined with intraoperative skin-surface warming does not avoid hypothermia caused by spinal anesthesia in patients with midazolam premedication

CONTEXT AND OBJECTIVE

Inadvertent perioperative hypothermia is common during spinal anesthesia and after midazolam administration. The aim of this study was to evaluate the effects of intraoperative skin-surface warming with and without 45 minutes of preoperative warming in preventing intraoperative and postoperative hypothermia caused by spinal anesthesia in patients with midazolam premedication.

DESIGN AND SETTING

Prospective and randomized study at Hospital das Clínicas, Universidade Estadual Paulista, Botucatu.

METHODS

Thirty patients presenting American Society of Anesthesiologists (ASA) physical status I and II who were scheduled for elective lower abdominal surgery were utilized. The patients received midazolam premedication (7.5 mg by intramuscular injection) and standard spinal anesthesia. Ten patients (Gcontrol) received preoperative and intraoperative passive thermal insulation. Ten patients (Gpre+intra) underwent preoperative and intraoperative active warming. Ten patients (Gintra) were only warmed intraoperatively.

RESULTS

After 45 min of preoperative warming, the patients in Gpre+intra had significantly higher core temperatures than did the patients in the unwarmed groups (Gcontrol and Gintra) before the anesthesia (p < 0.05) but not at the beginning of surgery (p > 0.05). The patients who were warmed intraoperatively had significantly higher core temperatures than did the patients in Gcontrol at the end of surgery (p < 0.05). All the patients were hypothermic at admission to the recovery room (T CORE < 36 degrees C).

CONCLUSIONS

Forty-five minutes of preoperative warming combined with intraoperative skin-surface warming does not avoid but minimizes hypothermia caused by spinal anesthesia in patients with midazolam premedication.

Dissociative anesthesia in an office-based plastic surgery practice

In 1974, the author began to use ketamine in association with diazepam for cosmetic and reconstructive procedures. Since then, through courses in the United States and abroad, well over a thousand plastic surgeons have been taught the technique. Ketamine, by itself, ablates sensory input of pain at the thalamic level but has been associated with hallucinations, bad dreams, and other untoward effects. These can be prevented by the use of benzodiazepines, which "bracket" the use of ketamine. If the patient is sedated and awakens under the influence of these agents, there is no adverse ketamine effect. Specific techniques and adjunct agents are described.

Lack of a pharmacokinetic interaction between steady-state roflumilast and single-dose midazolam in healthy subjects

AIMS

The aim of this study was to investigate the effects of roflumilast, an investigational PDE4 inhibitor for the treatment of COPD and asthma, on the pharmacokinetics of the CYP3A probe drug midazolam and its major metabolites.

METHODS

In an open, randomized (for midazolam treatment sequence) study, 18 healthy male subjects received single doses of midazolam (2 mg oral and 1 mg i.v., 1 day apart) alone, repeated doses of roflumilast (500 microg once daily for 14 days) alone, and repeated doses of roflumilast together with single doses of midazolam (2 mg oral and 1 mg i.v., 1 day apart).

RESULTS

A comparison of clearance and peak and systemic exposure to midazolam following administration of roflumilast indicated no effect of roflumilast dosed to steady state on the pharmacokinetics of midazolam. Point estimates (90% CI) were 0.97 (0.84, 1.13) for the AUC of i.v. midazolam and 0.98 (0.82, 1.17) for that of oral midazolam with and without roflumilast.

CONCLUSIONS

Therapeutic steady state concentrations of roflumilast and its N-oxide do not alter the disposition of the CYP3A substrate midazolam in healthy subjects. This finding suggests that roflumilast is unlikely to alter the clearance of drugs that are metabolized by CYP3A4.

Midazolam does not inhibit association formation, just its storage and strengthening

RATIONALE

Although there have been many studies examining the effects of benzodiazepines on memory performance, their effects on working memory are equivocal and little is known about whether they affect the efficacy of practice of already learned material.

OBJECTIVES

The objectives in two experiments were to examine (a) whether midazolam impairs performance on a working memory task designed to minimize mnemonic strategies such as rehearsal or chunking of information to be recalled and (b) the effect of midazolam on repeated practice of paired associates that were learned before drug administration.

MATERIALS AND METHODS

Both experiments involved subcutaneous administration of 0.03 mg of saline or midazolam per kilogram of bodyweight in within-subject, placebo-controlled designs, involving 23 subjects in (a) and 31 in (b).

RESULTS

The drug had no effect on the ability to recall the digits in serial order even though the encoding task prevented the digits from being rehearsed or maintained in an articulatory buffer. Paired associates that were learned before the injection showed a benefit of subsequent practice under saline but not under midazolam.

CONCLUSIONS

The results suggest that (a) midazolam does not affect the formation of new associations in short-term memory provided that the presentation rate is not too fast to form these associations when sedated, despite the evidence that the drug blocks long-term memory (LTM) retention of associations; and (b) the potential for over-learning with practice of learned associations in LTM is adversely affected by midazolam such that repeated exposures do not strengthen new learning.

Prediction of drug disposition in infants and children by means of physiologically based pharmacokinetic (PBPK) modelling: theophylline and midazolam as model drugs

AIMS

To create a general physiologically based pharmacokinetic (PBPK) model for drug disposition in infants and children, covering the age range from birth to adulthood, and to evaluate it with theophylline and midazolam as model drugs.

METHODS

Physiological data for neonates, 0.5-, 1-, 2-, 5-, 10- and 15-year-old children, and adults, of both sexes were compiled from the literature. The data comprised body weight and surface area, organ weights, vascular and interstitial spaces, extracellular body water, organ blood flows, cardiac output and glomerular filtration rate. Tissue: plasma partition coefficients were calculated from rat data and unbound fraction (f u) of the drug in human plasma, and age-related changes in unbound intrinsic hepatic clearance were estimated from CYP1A2 and CYP2E1 (theophylline) and CYP3A4 (midazolam) activities in vitro. Volume of distribution (V dss), total and renal clearance (CL and CL R) and elimination half-life (t(1/2)) were estimated by PBPK modelling, as functions of age, and compared with literature data.

RESULTS

The predicted V dss of theophylline was 0.4-0.6 l kg(-1) and showed only a modest change with age. The median prediction error (MPE) compared with literature data was 3.4%. Predicted total CL demonstrated the time-course generally reported in the literature. It was 20 ml h(-1) kg(-1) in the neonate, rising to 73 ml h(-1) kg(-1) at 5 years and then decreasing to 48 ml h(-1) kg(-1) in the adult. Overall, the MPE was - 4.0%. Predicted t(1/2) was 18 h in the neonate, dropping rapidly to 4.6-7.2 h from 6 months onwards, and the MPE was 24%. The predictions for midazolam were also in good agreement with literature data. V dss ranged between 1.0 and 1.7 l kg(-1) and showed only modest change with age. CL was 124 ml h(-1) kg(-1) in the neonate and peaked at 664 ml h(-1) kg(-1) at 5 years before decreasing to 425 ml h(-1) kg(-1) in the adult. Predicted t(1/2) was 6.9 h in the neonate and attained 'adult' values of 2.5-3.5 h from 1 year onwards.

CONCLUSIONS

A general PBPK model for the prediction of drug disposition over the age range neonate to young adult is presented. A reference source of physiological data was compiled and validated as far as possible. Since studies of pharmacokinetics in children present obvious practical and ethical difficulties, one aim of the work was to utilize maximally already available data. Prediction of the disposition of theophylline and midazolam, two model drugs with dissimilar physicochemical and pharmacokinetic characteristics, yielded results that generally tallied with literature data. Future use of the model may demonstrate further its strengths and weaknesses.

Differentiating midazolam over-sedation from neurological damage in the intensive care unit

INTRODUCTION

Midazolam is used routinely to sedate patients in the intensive care unit (ICU). We suspected that midazolam over-sedation was occurring in the ICU of the Guy's and St. Thomas' Trust and that it could be difficult to differentiate this from underlying neurological damage. A sensitive assay for detecting midazolam and 1-hydroxymidazolam glucuronide (1-OHMG) in serum was developed and applied in the clinical setting.

METHODS

In the present study we evaluated a series of cases managed in a mixed medical, surgical and trauma ICU. Serum was collected from 26 patients who received midazolam, were 'slow to wake' and in whom there was suspicion of neurological damage. Patient outcome was followed in terms of mortality, neurological recovery and neurological damage on discharge.

RESULTS

Out of 26 patients, 13 had detectable serum levels of midazolam and/or 1-OHMG after a median of 67 hours (range 36-146 hours) from midazolam cessation. Of these 13 patients in whom midazolam/1-OHMG was detectable, 10 made a full neurological recovery. Of the remaining 13 patients with no detectable midazolam/1-OHMG, three made a full neurological recovery; 10 patients were subsequently found to have suffered neurological damage (P < 0.002), eight of whom died and two were discharged from the ICU with profound neurological damage.

CONCLUSION

These findings confirm that prolonged sedation after midazolam therapy should be considered in the differential diagnosis of neurological damage in the ICU. This can be reliably detected by the assay method described. The effects of midazolam/1-OHMG persist days after administration of midazolam has ceased. After prolonged sedation has been excluded in this patient group, it is highly likely that neurological damage has occurred.

Midazolam premedication in children: a pilot study comparing intramuscular and intranasal administration

The purpose of this study was to compare the effectiveness of intramuscular and intranasal midazolam used as a premedication before intravenous conscious sedation. Twenty-three children who were scheduled to receive dental treatment under intravenous sedation participated. The patients ranged in age from 2 to 9 years (mean age, 5.13 years) and were randomly assigned to receive a dose of 0.2 mg/kg of midazolam premedication via either intramuscular or intranasal administration. All patients received 50% nitrous oxide and 50% oxygen inhalation sedation and local anesthetic (0.2 mL of 4% prilocaine hydrochloride) before venipuncture. The sedation level, movement, and crying were evaluated at the following time points: 10 minutes after drug administration and at the times of parental separation, passive papoose board restraint, nitrous oxide nasal hood placement, local anesthetic administration, and initial venipuncture attempt. Mean ratings for the behavioral parameters of sedation level, degree of movement, and degree of crying were consistently higher but not significant in the intramuscular midazolam group at all 6 assessment points. Intramuscular midazolam was found to be statistically more effective in providing a better sedation level and less movement at the time of venipuncture than intranasal administration. Our findings indicate a tendency for intramuscular midazolam to be more effective as a premedication before intravenous sedation.

Chronic NGF treatment of rat nociceptive DRG neurons in culture facilitates desensitization and deactivation of GABAA receptor-mediated currents

1 The present study tested the hypothesis that nerve growth factor (NGF) could affect presynaptic inhibition mediated by GABAA (GABA-sensitive ionotropic receptors) receptors on the afferents of nociceptive dorsal root ganglia (DRG) neurons, thus reducing the filtering of central nociceptive signals. 2 To investigate this issue, small-diameter, nociceptive DRG neurons were cultured for 48-72 h either in the normal medium or in the presence of NGF (50 ng ml(-1)). After 15 min washout, cells were patch clamped with Cs+ containing electrodes to block GABAB (GABA-sensitive metabotropic receptors) receptor-activated currents. 3 Chronically treated DRG neurons showed no difference in the peak amplitude of GABA-induced currents. However, NGF-treated cells exhibited increased fading of the response to continuous GABA application, with faster desensitization onset, decreased residual current at the end of agonist application and slower recovery from desensitization. Moreover, the deactivation phase after brief agonist pulses was also accelerated. 4 Unlike responses to GABA, chronic NGF treatment had no effect on the desensitization process to the excitatory transmitter ATP, as no difference in peak amplitude, fast and slow time constants of current decay was found. 5 Experimental tests indicated that the observed effects on GABA currents were not a reactive process triggered by washing out NGF after its long application. Acutely applied NGF did not change GABAA receptor-mediated responses. 6 NGF-treated neurons showed decreased sensitivity to the antagonist picrotoxin. The action of pentobarbitone, midazolam, bicuculline or gabazine was, however, unchanged. 7 These observations suggest that the modulation of GABAA receptor function of DRG nociceptors by NGF may contribute to the algogenic action of this neurotrophin.