Etomidate and telazol

Behavioural Aversion and Cortisol Level Assessment When Adult Zebrafish Are Exposed to Different Anaesthetics

Simple Summary

The increased popularity of zebrafish as a research model calls for appropriate refinement of procedures, such as finding the best anaesthetic protocol to use in adult zebrafish in a laboratory setting. The scarce literature available regarding aversion described the most used anaesthetic (MS222) as aversive to adult zebrafish; therefore, the study of alternatives is urgent. Thus, we studied the impact of three anaesthetic alternatives (a combination of propofol with lidocaine, clove oil, and etomidate), and the standard anaesthetic (MS222) on zebrafish aversion and on cortisol levels. Contrary to what was expected, MS222 did not result in clear signs of aversion, while only etomidate generated a similar profile to the aversive substance (hydrochloric acid). Our results suggested that all the anaesthetic protocols except for etomidate were valid candidates for use in a laboratory setting, although none were innocuous.

Abstract

The use of zebrafish (Danio rerio) as an animal model is growing and occurs in a wide range of scientific areas. Therefore, researchers need better and more appropriate anaesthetics for stressful and/or painful procedures to prevent unpleasant experiences. Thus, we aimed to study if adult zebrafish displayed aversion-associated behaviours (conditioned place aversion) and alterations in cortisol levels when exposed to equipotent concentrations of MS222, propofol/lidocaine, clove oil, or etomidate. Adult AB zebrafish (mixed-sex, N = 177) were randomly assigned to MS222 (150 mg/L), Propofol/Lidocaine (5 mg/L propofol + 150 mg/L lidocaine), Clove Oil (45 mg/L), or Etomidate (2 mg/L) groups. The conditioned place aversion test was used to assess behavioural aversion. Only etomidate resulted in a similar aversion to the positive control group (HCl; pH = 3). Cortisol levels were measured 5 and 15 min after loss of equilibrium. Etomidate induced low levels of cortisol by impairing its synthesis, whereas all the other groups had similar cortisol levels. Based on our data, etomidate was ruled out as an alternative to MS222, as it showed an aversive profile. The remaining protocols were not innocuous, displaying a weak aversive profile when compared to the positive control. In conclusion, a combination of propofol with lidocaine, clove oil, and MS222 were valid candidates for use as anaesthetic protocols.

Comparison of intratesticular and intramuscular administration of zolazepam-tiletamine combination on sedation, induction, and recovery qualities and vital variables in cats undergoing castration: a prospective, randomized, clinical study

This study was aimed to compare the effects of intratesticular (IT) and intramuscular (IM) administration of the zolazepam-tiletamine (ZT) combination on sedation, induction, and recovery qualities and vital variables in cats undergoing castration. Fourteen clinically client-owned healthy cats were randomly assigned to receive 10 mg/kg ZT by either IT or IM routes. Temperament score, injection reaction score, induction time, intubation time, surgical length, anesthesia time, recovery time, and full recovery time were evaluated. Sedation score, heart rate (HR), respiratory frequency (f_R), peripheral hemoglobin oxygen saturation (SpO₂), mean arterial pressure (MAP), and rectal temperature (RT) variables were assessed at baseline (T0), T5, T10, T15, and T30. Median temperament score and injection reaction score were not different between groups. Induction time was significantly (p = 0.0244) shorter for the IT group (142.6 ± 29.9) than IM (290 ± 48.7 seconds). Length of anesthesia was longer in the IM group (median 290; ranged 120-540 minutes) than the IT group (median 140; ranged 98-180 minutes) (p = 0.0279). Time to standing and time to full recovery were significantly shorter in IT than IM. A recovery quality score did not significantly differ between groups (p = 0.2268). No statistically significant differences were detected between IT and IM administration regarding sedation score, HR, SpO₂, MAP, and RT. The IT administration of 10 mg/kg ZT induces shorter onset of sedation and recovery time than IM administration, thereby it can be suggested for cats undergoing castration. Both administration routes produce effective sedation with limited physiological changes in anesthesia variables.

Recovery characteristics of dogs following anesthesia induced with tiletamine-zolazepam, alfaxalone, ketamine-diazepam, or propofol and maintained with isoflurane

OBJECTIVE To compare characteristics of recovery from isoflurane anesthesia in healthy nonpremedicated dogs after anesthetic induction by IV administration of tiletamine-zolazepam with those observed after induction by IV administration of alfaxalone, ketamine-diazepam, or propofol. DESIGN Prospective, randomized crossover study. ANIMALS 6 healthy adult hounds. PROCEDURES Each dog underwent the 4 treatments in random order with a ≥ 7-day washout period between anesthetic episodes. Anesthesia was induced by IV administration of the assigned induction drug or combination (each to effect in 25% increments of calculated dose) and maintained with isoflurane in oxygen for 60 minutes. Cardiorespiratory variables and end-tidal isoflurane concentration (ET_ISO) were measured just before isoflurane administration was discontinued. Dogs were observed and video recorded during recovery. Recovery characteristics were retrospectively scored from recordings by 3 raters. Interrater and intrarater reliability of scoring was assessed by intraclass correlation coefficient calculation. Linear and mixed ANOVAs were used to compare extubation times, recovery scores, and body temperature among treatments. RESULTS Most cardiorespiratory variables, body temperature, ET_ISO, and time to extubation did not differ between tiletamine-zolazepam and other induction treatments. Recovery scores were lower (indicating better recovery characteristics) with propofol or alfaxalone than with tiletamine-zolazepam but did not differ between tiletamine-zolazepam and ketamine-diazepam treatments. Anesthetic episode number and ET_ISO had no effect on extubation time or recovery score. Intrarater and interrater correlations for recovery scores were excellent. CONCLUSIONS AND CLINICAL RELEVANCE Recovery of healthy dogs from anesthesia with isoflurane after induction with tiletamine-zolazepam was uncomplicated and had characteristics comparable to those observed following induction with ketamine-diazepam. However, recovery characteristics were improved when anesthesia was induced with propofol or alfaxalone.

Clinical and haematological responses of feline blood donors anaesthetised with a tiletamine and zolazepam combination

This prospective study investigated the effect on clinical and haematological variables of the anaesthetic combination of tiletamine and zolazepam in feline blood donors. Blood (10 ml/kg bodyweight to a maximum volume of 60 ml) was collected from the jugular vein of 31 owned healthy cats anaesthetised with 2.5 mg/kg of tiletamine and 2.5 mg/kg of zolazepam intramuscularly. Rectal temperature (RT), systolic arterial pressure (SAP), mean arterial pressure (MAP), diastolic arterial pressure (DAP), heart rate (HR) and complete blood count (including red blood cells [RBC], haemoglobin [HB], haematocrit [HT], platelet [PLT] count, white blood cells [WBC], lymphocytes, neutrophils, eosinophils, monocytes and basophils) were evaluated pre- and postdonation. RT decreased significantly (P <0.01) after blood donation (mean change in RT -0.7°C). Significant increases in SAP (P = 0.03), MAP (P <0.01) and DAP (P <0.01) occurred after blood donation (mean increase 13 mmHg, 12 mmHg and 11 mmHg, respectively). Although RBC, HT, HB, WBC, PLT, neutrophil and monocyte counts decreased, and HR, and lymphocyte, eosinophil and basophil counts increased after blood donation this change was not statistically significant. Mean time from pre- to postdonation evaluation was 39 ± 11 mins (range 24-76 mins). None of the cats had evidence of pallor or collapse after recovery from anaesthesia. The collection of blood at 10 ml/kg bodyweight to a maximum volume of 60 ml in healthy cats using a low dose tiletamine and zolazepam anaesthetic appears to be well tolerated by feline blood donors.

Efeitos da infusão contínua de propofol ou etomidato sobre variáveis intracranianas em cães

Avaliaram-se os efeitos da infusão contínua de propofol ou de etomidato sobre as variáveis intracranianas em cães nomocapneicos. Foram utilizados 20 cães adultos distribuídos aleatoriamente em dois grupos: grupo propofol (GP) e grupo etomidato (GE). Para o GP, os animais foram induzidos à anestesia com propofol (10mg/kg) e, ato contínuo, iniciaram-se a infusão do fármaco (0,6mg/kg/min) e a ventilação controlada. No GE, o etomidato foi usado para indução (5mg/kg) e manutenção empregando-se a dose de 0,5mg/kg/min nos 10 minutos iniciais e, em seguida, de 0,2mg/kg/min. Após 30 minutos da implantação do cateter de fibra óptica do monitor de pressão intracraniana (PIC) na superfície do córtex cerebral direito, realizaram-se as primeiras mensurações (M1) da PIC, da pressão de perfusão cerebral (PPC), da temperatura intracraniana (TIC), de temperatura corpórea (TC), da pressão arterial média (PAM) e da frequência cardíaca (FC). As demais mensurações ocorreram em intervalos de 20 minutos (M2, M3 e M4). O propofol e o etomidato não ocasionaram alterações significativas nas variáveis estudadas com exceção da TC e TIC. Concluiu-se que a infusão contínua desses fármacos em cães mantém a perfusão cerebral e a autorregulação cerebral. Cães anestesiados com etomidato apresentam efeitos adversos intensos e redução gradativa da temperatura corpórea e intracraniana.

A comparison of the effects of propofol and etomidate on the induction of anesthesia and on cardiopulmonary parameters in dogs

OBJECTIVE

To determine the effects of propofol or etomidate on induction quality, arterial blood pressure, blood gases, and recovery quality in normal dogs.

STUDY DESIGN

Randomized, blinded trial.

ANIMALS

Eighteen purpose-bred adult Beagles.

METHODS

Dogs were randomly assigned to receive propofol at 8 mg kg(-1) or etomidate at 4 mg kg(-1) intravenously (IV) administered to effect. Midazolam was administered at 0.3 mg kg(-1) IV as pre-medication at least 1 minute prior to induction. Direct arterial blood pressure, arterial blood gases, and heart rate were obtained at baseline, before induction, after induction, and for every 5 minutes afterwards until the dog began to swallow and the trachea was extubated. The dogs were allowed to breathe room air with the endotracheal tube in place.

RESULTS

The systolic arterial pressure (SAP) was higher in the etomidate group compared with the propofol group after induction. The SAP and mean arterial pressure (MAP) were higher in the etomidate group compared with the propofol group at 5 minutes. The recovery quality and ataxia score were worse in the etomidate group compared with the propofol group. Time from extubation to sternal recumbency and sternal recumbency to standing was longer in the etomidate group compared with the propofol group. The heart rate, PaCO(2), and HCO(3) were higher in the propofol group compared with the etomidate group after induction. The PaO(2) and SaO(2) were lower in the propofol group compared with the etomidate group after induction. The SAP and MAP were lower in the propofol group at 5 minutes compared with baseline.

CONCLUSION AND CLINICAL RELEVANCE

Propofol caused a decrease in SAP and MAP which was not observed with etomidate. Etomidate caused longer and poorer recoveries than propofol.

The effects on maternal and fetal cardiovascular and acid–base variables after the administration of etomidate in the pregnant ewe

Etomidate is an intravenous (IV) hypnotic agent characterised by its cardiovascular stability. Although etomidate has been satisfactorily used in veterinary and human obstetrics, little is known about its effects on the fetus. This study determined the cardiovascular and acid-base effects of etomidate administration in the pregnant ewe and her fetus. The effects of etomidate were evaluated in two separate studies. In the first study, etomidate was administered as a 1mg/kg IV bolus; in the second, the drug was administered as a continuous infusion of 100 microg/kg/min for 1h, preceded by a 1mg/kg IV bolus. Etomidate administration did not depress cardiovascular function in the pregnant ewe or fetus. When administered as a continuous infusion, maternal heart rate and blood pressure increased during the second half of the infusion and the initial stages of recovery. Acid-base alterations led to transient but slight respiratory depression in both mother and fetus, probably reflecting the combined effects of etomidate on respiration and the positioning of the animal.

Placental transfer of etomidate in pregnant ewes after an intravenous bolus dose and continuous infusion

Etomidate (ETO) is a short-acting intravenous (IV) anaesthetic characterised by cardiopulmonary stability and favourable pharmacokinetics. Although ETO has been used satisfactorily in obstetrical anaesthesia, little is known about placental transfer and the drug's pharmacokinetics in the fetus. Placental transfer in pregnant ewes has been evaluated following the administration of an IV bolus of 1mg/kg ETO; and after a 1-h infusion of 100 microg/kg min(-1) ETO preceded by an IV bolus of 1mg/kg. In ewes, ETO concentration and AUC were higher than those found in fetuses. After the ETO bolus dose, the fetus:ewe AUC ratio was 0.45+/-0.32, and the mean residence time (MRT) was 20+/-7 min for dams and 22+/-3 min for the fetuses. After ETO infusion, the AUC ratio was 0.37+/-0.08, and MRT was 46+/-12 min for ewes and 46+/-22 min for fetuses. Although ETO crosses the placenta very rapidly and reaches the fetus in high amounts, a certain placental barrier effect limits its transfer. There is no evidence of cumulative effects of the drug in the fetus as fetal ETO elimination was as rapid as in the dam.

Balloon Valvuloplasty of Valvular Pulmonic Stenosis in the Dog

Balloon valvuloplasty has become the accepted method of therapy for the majority of dogs with valvular pulmonic stenosis. Success rate of balloon valvuloplasty is excellent but the procedure can have a steep learning curve. An understanding of the equipment used and specifics of the procedure is important to maximize success and minimize risk. This paper will review criteria for choosing candidates for balloon valvuloplasty, discuss the equipment used, discuss the procedure in detail, and finally discuss assessment of success and possible complications.

Blood gas and acid–base status during tiletamine/zolazepam anaesthesia in dogs

OBJECTIVE

To evaluate the effect of the tiletamine/zolazepam (TZ) combination (Zoletil 100; Virbac, Carros, France) with and without atropine on blood gas values and acid-base status in dogs.

STUDY DESIGN

Randomized cross-over experimental study.

ANIMALS

Six healthy adult cross-bred dogs, weighing 11.0-18.5 kg.

MATERIALS AND METHODS

Each dog received four different drug treatments at intervals of at least 15 days: (i) 5 mg kg(-1) intravenous (IV) TZ (TZ.IV); (ii) 10 mg kg(-1) intramuscular (IM) TZ (TZ.IM); (iii) atropine, 20 microg kg(-1) IV, followed 5 minutes later by 5 mg kg(-1) TZ IV (A.TZ.IV); and (IV) atropine (same dose) given 5 minutes before 10 mg kg(-1) TZ IM (A.TZ.IM). Arterial blood samples were collected from each dog before drug administration (baseline) at induction of anaesthesia (time 0) and 2, 5, 10 and 30 minutes thereafter.

RESULTS

Transient hypoxaemia and respiratory acidosis were observed just after induction. PaO(2) and SaO(2) dropped, while H(+) concentration and PaCO(2) rose significantly above baseline values. In groups TZ.IV and A.TZ.IV, PaO(2) values as low as 6.0-6.4 kPa (45-48 mm Hg) were recorded. However, there was no significant difference in blood gas variables among the groups encountered during the evaluation period. The overall change in [HCO(3) (-)] and base excess (BE) was not significant among groups. Atropine did not affect the above variables.

CONCLUSIONS AND CLINICAL RELEVANCE

Tiletamine/zolazepam injection may induce transient hypoxaemia and respiratory acidosis, but acid-base status changes are clinically unimportant. Particularly, close observation of dogs is recommended during the first 5-10 minutes after induction with TZ, especially in animals with cardiopulmonary disease. TZ should perhaps not be used in animals intolerant of tachycardia.

The Effect of Tiletamine/Zolazepam (Zoletile) Combination with Xylazine or Medetomidine on Electroencephalograms in Dogs

The effects of xylazine or medetomidine on tiletamine/zolazepam (Zoletile) anesthesia were evaluated by changes in the canine electroencephalogram (EEG). Experimental groups were three: the group treated with 10 mg/kg of Zoletile intravenously (TZ), the group treated with 1.1 mg/kg of xylazine intramuscularly and 10 mg/kg of Zoletile intravenously (XTZ), and the group treated with 30 microg/kg of medetomidine intramuscularly and 10 mg/kg of Zoletile intravenously (MTZ). EEG recording electrode was positioned at Cz, which was applied to International 10-20 system. For all recording times, the powers of each band (band 1: 1-2.5 Hz, band 2: 2.5-4.5 Hz, band 3: 4.5-8 Hz, band 4: 8-13 Hz, band 5: 13-20 Hz, band 6: 20-30 Hz, band 7: 30-50 Hz, band 8: 1-50 Hz) were calculated. In TZ, at 10 min after Zoletile injection, the powers of bands 3, 4, 5 and 8 significantly decreased. At 20 min after Zoletile injection, the powers of band 1 and 8 were significantly decreased. After Zoletile injection, there were significant decreases in bands 1, 4, 5, 6, 7 and 8 in XTZ, and in bands 1, 3, 4, 5, 6, 7 and 8 in MTZ. These significant changes disappeared in all band powers in TZ and MTZ in the last 1 min just prior to the dogs showing head-up movement. But, in XTZ, all band powers, except band 2, were significantly reduced. EEG power spectral analysis revealed the differences in band powers on awakening, even though the same kind of drugs were used. We thought that was a useful method to compare the effect of xylazine and medetomidine on Zoletile-induced anesthesia in dogs.

Anesthesia for the acute abdomen patient

Patients with acute abdomen often have marked physiologic and pathologic changes, making anesthesia both challenging and potentially hazardous for the patient. A thorough understanding of the pathophysiologic mechanisms of cardiovascular function under anesthesia and selection of appropriate anesthetic protocols are critical to a successful anesthetic outcome. The goal is to produce anesthesia while minimizing depression of the cardiovascular system. Monitoring and management of acid-base and cardiovascular function serve to ensure appropriate oxygen delivery to the tissues during anesthesia. Postoperative management can significantly influence patient outcome following anesthesic recovery, and must therefore be considered in the anesthetic plan. Finally, pain management in all patients is an important aspect of case management, and should not be overlooked. This article serves to educate the clinician in the above-described areas in regard to the acute abdomen patient.

Cardiopulmonary effects of three different anaesthesia protocols in cats

To develop an alternative anaesthetic regimen for cats with cardiomyopathy, the cardiopulmonary effects of three different premedication-induction protocols, followed by one hour maintenance with isoflurane in oxygen: air were evaluated in six cats. Group I: acepromazine (10 microg/kg) + buprenorphine (10 microg/kg) IM, etomidate (1-2 mg/kg) IV induction. Group II: midazolam (1 mg/kg) + ketamine (10 mg/kg) IM induction. Group III: medetomidine (1.5 mg/m2 body surface) IM, propofol (1-2 mg/kg) IV induction. Heart rate, arterial blood pressure, arterial blood gases, respiration rate, and temperature were recorded for the duration of the experiment. In group I the sedative effect after premedication was limited. In the other groups the level of sedation was sufficient. In all groups premedication resulted in a reduced blood pressure which decreased further immediately following induction. The reduction in mean arterial pressure (MAP) reached statistical significance in group I (142+/-22 to 81+/-14 mmHg) and group II (153+/-28 to 98+/-20 mmHg) but not in group III (165+/-24 to 134+/-29 mmHg). Despite the decrease in blood pressure, MAP was judged to have remained within an acceptable range in all groups. During maintenance of anaesthesia, heart rate decreased significantly in group III (from 165+/-24 to 125+/-10 b.p.m. at t=80 min). During anaesthesia the PCO2 and PO2 values increased significantly in all groups. On the basis of the results, the combination acepromazine-buprenorphine is preferred because heart rate, MAP, and respiration are acceptable, it has a limited sedative effect but recovery is smooth.