Randomized clinical trial of the effects of a combination of acepromazine with morphine and midazolam on sedation, cardiovascular variables and the propofol dose requirements for induction of anesthesia in dogs

Dose-dependent changes in orientation amplitude maps in the cat visual cortex after propofol bolus injections

A general intravenous anesthetic propofol (2,6-diisopropylphenol) is widely used in clinical, veterinary practice and animal experiments. It activates gamma- aminobutyric acid (GABAa) receptors. Though the cerebral cortex is one of the major targets of propofol action, no study of dose dependency of propofol action on cat visual cortex was performed yet. Also, no such investigation was done until now using intrinsic signal optical imaging. Here, we report for the first time on the dependency of optical signal in the visual cortex (area 17/area 18) on the propofol dose. Optical imaging of intrinsic responses to visual stimuli was performed in cats before and after propofol bolus injections at different doses on the background of continuous propofol infusion. Orientation amplitude maps were recorded. We found that amplitude of optical signal significantly decreased after a bolus dose of propofol. The effect was dose- and time-dependent producing stronger suppression of optical signal under the highest bolus propofol doses and short time interval after injection. In each hemisphere, amplitude at cardinal and oblique orientations decreased almost equally. However, surprisingly, amplitude at cardinal orientations in the ipsilateral hemisphere was depressed stronger than in contralateral cortex at most time intervals. As the magnitude of optical signal represents the strength of orientation tuned component, these our data give new insights on the mechanisms of generation of orientation selectivity. Our results also provide new data toward understanding brain dynamics under anesthesia and suggest a recommendation for conducting intrinsic signal optical imaging experiments on cortical functioning under propofol anesthesia.

Effect of Classical Music on Depth of Sedation and Induction Propofol Requirements in Dogs

The main objective of this prospective, randomized, blind, cross-over experimental study was to evaluate the effect of classical music on the depth of sedation and propofol requirements for the induction of anaesthesia in dogs. Twenty dogs were involved, and each was subjected to three different treatments with a 3-month gap: Chopin music, Mozart music, and no music, via loudspeakers. The dogs were premedicated with acepromazine and butorphanol by intramuscular injection, and anaesthesia was induced using propofol intravenously. To compare the depth of sedation and propofol requirements for the induction of anaesthesia among the different treatments, we utilized non-parametric tests (Kruskal-Wallis test) for the depth of sedation due to a slight deviation from the normal distribution and parametric (ANOVA) for propofol requirements. When exposed to music (Chopin or Mozart), dogs exhibited deeper sedation and required less propofol for their intubation compared to the no-music treatment (p < 0.05). Exposure to classical music had a positive impact on the level of sedation, and more profound central nervous system depression seemed to contribute to approximately 20% lower propofol dose requirements for tracheal intubation. Therefore, classical music during the preoperative period appeared to exert a beneficial effect, at least when applying the specific pre-anaesthetic medications used in the present study.

DEXMEDETOMIDINE ALONE OR COMBINED WITH MORPHINE FOR EPIDURAL ANESTHESIA IN BITCHES UNDERGOING ELECTIVE OVARIOHYSTERECTOMY

The purpose of this study was to assess perioperative analgesia provided by the combination of epidural dexmedetomidine and morphine in bitches undergoing elective ovariohysterectomy. Twenty-four bitches were included in the study and allocated into three groups: GM, morphine 0.1 mg/kg; GD, dexmedetomidine 2 µg/kg; and GDM, dexmedetomidine and morphine at the same doses. All solutions were diluted in saline to a total of 0.36 mL/kg. Heart rate (HR), respiratory rate (FR) and systolic blood pressure (SAP) were recorded prior to epidural analgesia (TB), immediately following epidural analgesia (TEA), at surgical incision (TSI), at the first ovarian pedicle clamping (TOP1), at the second pedicle clamping (TOP2), at uterine stump clamping (TUC), at the start of abdominal cavity closure (TSC) and at the end of skin closure (TEC). Rescue analgesia with fentanyl was administered at 2 µg/kg IV if nociception corresponding to a 20% increase of any cardiorespiratory variables was noted. Postoperative pain assessment was performed using a modified composite Glasgow pain scale along the first 6 hours following the end of surgery. Numeric data were compared using ANOVA for repeated measures followed by Tukey test and ovarian ligament relaxation was analyzed using chi-square test under 5% significance. No differences were found on FR among times or groups, although HR showed significant differences between GM and GD at TSI, TOP1, TOP2, TSC and TEC and between GM and GDM at TEA and TSI (significantly lower HR values recorded in dexmedetomidine groups). Differences among time points were found on HR between TB and TEA in GD and on PAS between TOP1 and TSC in GM and between TOP1 and TUC in GDM (p<0.05). Ovarian ligament relaxation was significantly more present in groups using dexmedetomidine, although the number of rescue analgesia administrations did not differ among groups. Kaplan-Meyer analysis failed to show significant differences on time of rescue analgesia administration among groups (p>0.05). In conclusion, the combination of epidural dexmedetomidine and morphine is a more interesting choice for elective ovariohysterectomy in bitches for producing analgesia comparable to that of each drug alone, with noticeable relaxation of ovarian ligaments and lesser cardiovascular consequences.

Echocardiographic Assessment of Healthy Midazolam/Butorphanol or Midazolam/Morphine-Sedated Dogs

The purpose of this study was to assess the effects of midazolam combined with morphine or butorphanol on echocardiographic variables of healthy dogs. Twenty-four dogs of various breeds aged 34.33 ± 23.41 months and weighing 8.1 ± 4.7 kg were enrolled in the study. Subjects were randomly allocated in one of two experimental groups of sedation with intramuscular midazolam (0.3 mg/kg) combined with butorphanol (0.2 mg/kg) (G_B, n = 12) or morphine (0.3 mg/kg) (G_M, n = 12). Transthoracic echocardiographic examinations comprised B-Mode, M-Mode, spectral Doppler and pulsed tissue Doppler assessment. Data were recorded before sedation (T_B) and 20 minutes following intramuscular administration of either sedation protocol (T_S). Data were analyzed using repeated measures ANOVA followed by Tukey's posthoc test. Shortening fraction, ejection fraction, left ventricular diameter and volume did not differ among groups and time points. The A and E' waves were decreased in G_M at T_S compared to T_B. Isovolumic relaxation time, Ae/Ao ratio, aortic and pulmonary flows and S' wave did not differ among time points and groups. These sedation protocols did not cause clinically relevant changes in echocardiographic variables, therefore can be used for sedation of uncooperative dogs during echocardiographic evaluation.

Quetiapine and other antipsychotics combined with opioids in legal autopsy cases: A random finding or cause of fatal outcome?

Opioid poisoning is a frequent cause of death in drug addicts and occurs with opioid treatment. Quetiapine is often found in forensic autopsies and may increase the risk of fatal opioid poisoning by enhancing sedation, respiratory depression, hypotension and QT prolongation. We systematically searched for studies of acute toxicity of quetiapine or other antipsychotics combined with morphine or methadone. Case reports describing toxicity of quetiapine combined with morphine or methadone were also included. We retrieved one human study that observed pharmacokinetic interaction between quetiapine and methadone, and 16 other human studies. Fourteen investigated the combination of droperidol and morphine in treatment doses, and some indicated an additive sedative effect. Five animal studies with acepromazine in combination with morphine or methadone were located and indicated an additive effect on sedation and hypotension. Six forensic case reports in which death could have been caused solely by quetiapine, the opioid, or other drugs were found. Thus, acute toxicity of quetiapine combined with morphine or methadone has not been studied. Because of quetiapine's effects on alpha-adrenoceptors, muscarinic and histamine receptors, human ether-a-go-go-channels and methadone kinetics, we suggest further research to clarify if the indicated additive effects of opioids and droperidol or acepromazine are also true for quetiapine.

Oral Transmucosal or Intramuscular Administration of Dexmedetomidine-Methadone Combination in Dogs: Sedative and Physiological Effects

Simple Summary

During the last decade, new alternative non-invasive administration routes for drug delivery have gained interest in veterinary medicine. The administration of drugs via the oral transmucosal route is non-invasive, painless, easy to perform, and generally well tolerated. Furthermore, it avoids gastric acid degradation typical of oral administration. All these characteristics contribute to make this administration route very attractive, especially for veterinary patients who are difficult to inject, fearful, or anxious. In contrast, intramuscular injection is associated with pain and requires more invasive restraint, potentially incrementing patients’ discomfort. The aim of this study was to assess and compare the sedative and clinical effects of a dexmedetomidine–methadone combination following either oral transmucosal and intramuscular administration in healthy dogs and to record any possible adverse effects following each administration route. The present study suggests that oral transmucosal administration of dexmedetomidine and methadone combination provided a satisfactory level of sedation, allowing safe handling of the patients with less pronounced cardiorespiratory effects. Indeed, thanks to the lesser impact on the cardiac function, it could be considered as a useful option for those patients difficult to restrain in which cardiovascular stability should be preserved.

Abstract

The aim of this study was to compare the sedative and physiological effects following either oral transmucosal (OTM) or intramuscular administration of dexmedetomidine–methadone combination in healthy dogs. Thirty dogs were randomly assigned to receive a dexmedetomidine–methadone combination either by the OTM (n = 15) or intramuscular (n = 15) route. Sedation was scored 10, 20, and 30 min after drugs administration. Heart rate (HR), non-invasive blood pressure (NIBP), respiratory rate (f_R), and body rectal temperature were recorded before drugs administration and then every 10 min for 30 min. Propofol dose required for orotracheal intubation was recorded. Sedation scores increased over time within both groups with higher values in intramuscular group (p < 0.05). Within each group, HR decreased significantly compared with baseline (p < 0.001) and was significantly lower in intramuscular group compared with the OTM group (p < 0.001). In both groups, NIBP increased significantly compared with baseline (p < 0.05). In the intramuscular group, f_R was lower compared with the OTM group at all the observational time points (p < 0.001). Propofol dose was lower in the intramuscular group (p < 0.05). Compared to intramuscular dexmedetomidine–methadone, OTM combination produced lower but effective sedation in healthy dogs.

Effects of 2% lidocaine hydrochloride solution as a coinduction agent with propofol on cardiopulmonary variables and administered propofol doses in healthy dogs premedicated with hydromorphone hydrochloride and acepromazine maleate

OBJECTIVE

To evaluate the effects of lidocaine as a coinduction agent with propofol on cardiopulmonary variables and administered propofol doses in healthy dogs premedicated with hydromorphone hydrochloride and acepromazine maleate and anesthetized with isoflurane.

ANIMALS

40 client-owned dogs (American Society of Anesthesiologists physical status classification I or II and age ≥ 6 months) scheduled to undergo anesthesia for elective procedures.

PROCEDURES

In a randomized, blinded, controlled clinical trial, dogs received 2% lidocaine hydrochloride solution (2.0 mg/kg [0.9 mg/lb], IV; n = 20) or buffered crystalloid solution (0.1 mL/kg [0.05 mL/lb], IV; 20; control treatment) after premedication with acepromazine (0.005 mg/kg [0.002 mg/lb], IM) and hydromorphone (0.1 mg/kg, IM). Anesthesia was induced with propofol (1 mg/kg [0.45 mg/lb], IV, with additional doses administered as needed) and maintained with isoflurane. Sedation was assessed, and anesthetic and cardiopulmonary variables were measured at various points; values were compared between treatment groups.

RESULTS

Propofol doses, total sedation scores, and anesthetic and most cardiopulmonary measurements did not differ significantly between treatment groups over the monitoring period; only oxygen saturation as measured by pulse oximetry differed significantly (lower in the lidocaine group). Mean ± SD propofol dose required for endotracheal intubation was 1.30 ± 0.68 mg/kg (0.59 ± 0.31 mg/lb) and 1.41 ± 0.40 mg/kg (0.64 ± 0.18 mg/lb) for the lidocaine and control groups, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

No propofol-sparing effect was observed with administration of lidocaine as a coinduction agent for the premedicated dogs of this study. Mean propofol doses required for endotracheal intubation were considerably lower than currently recommended doses for premedicated dogs. (J Am Vet Med Assoc 2020;256:93-101).

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.