Assessment of ketamine and medetomidine anaesthesia in the domestic rabbit

Intranasal Atomization of Ketamine, Medetomidine and Butorphanol in Pet Rabbits Using a Mucosal Atomization Device

A non-invasive method of drug delivery, intranasal atomization, has shown positive results in human medicine and in some animal species. The objective of this study was to evaluate the effects of intranasal atomization, compared to intramuscular administration, of a mix of anesthetic drugs in pet rabbits. In total, 104 mixed-breed pet rabbits, undergoing various types of surgery, received a combination of ketamine, medetomidine, and butorphanol (20, 0.4, and 0.2 mg/kg) by intranasal atomization using a Mucosal Atomization Device (Group MAD) or intramuscular administration (Group IM). When required, isoflurane was dispensed through a face mask. At the end of the procedures, atipamezole was administered using the same routes in the respective Groups. There were no differences in time to loss of righting reflex between the groups, while differences were found for the need for isoflurane (higher in Group MAD) and recovery time, occurring earlier in Group MAD. The results suggest that intranasal atomization of a combination of ketamine, medetomidine, and butorphanol produces a lighter depth of anesthesia in pet rabbits, compared to intramuscular administration. Intranasal atomization can be performed to administer sedative and anesthetic drugs, avoiding the algic stimulus related to the intramuscular inoculation of drugs.

Comparison of two injectable anaesthetic protocols in Egyptian fruit bats (Rousettus aegyptiacus) undergoing gonadectomy

Egyptian fruit bats have gained increasing interest being a natural reservoir for emerging zoonotic viruses. Anaesthesia is often required to allow safe handling of bats. We aimed to compare the sedative and cardiopulmonary effects of two balanced anaesthetic protocols in bats undergoing gonadectomy. Group DK (n = 10) received intramuscular dexmedetomidine (40 µg/kg) and ketamine (7 mg/kg), whereas group DBM (n = 10) received intramuscular dexmedetomidine (40 µg/kg), butorphanol (0.3 mg/kg) and midazolam (0.3 mg/kg). Induction time and cardiopulmonary parameters were recorded. If anaesthetic plan was inadequate, isoflurane was titrated-to-effect. At the end of surgery venous blood gas analysis was performed and atipamezole or atipamezole-flumazenil was administered for timed and scored recovery. In DBM group heart rate and peripheral oxygen saturation were significantly higher (p = 0.001; p = 0.003 respectively), while respiratory rate was significantly lower (p = 0.001). All bats required isoflurane supplementation with no significant differences between groups. Induction and recovery times showed no significant differences. In group DK a better recovery was scored (p = 0.034). Sodium and chloride were significantly higher in DBM group (p = 0.001; p = 0.002 respectively). Both anaesthetic protocols were comparable and can be recommended for minor procedures in bats.

Does hemofiltration protect the brain after head trauma? An experimental study in rabbits

Background

Traumatic brain injury (TBI) is one of the most frequent and severe neurological diseases. In the last few decades, significant advances have been made in TBI pathophysiology and monitoring, however new treatments have not emerged. Although the central nervous system (CNS) has been historically defined as an immunologically privileged organ, recent studies show the increasingly predominant role of inflammatory and apoptotic phenomena in the pathogenesis of TBI. Inflammatory response mediators can be eliminated with continuous renal replacement therapies (CRRT). Our aim was to investigate whether hemofiltration protects the brain after head trauma in an experimental study in animals.

Methods and results

A model of TBI and CVVH was performed in anesthetized New Zealand white rabbits without acute renal failure. The experimental group TBI ( +)-CVVH ( +) was compared with a TBI ( +)-CVVH (−) and a TBI (−)-CVVH ( +) control groups. Rabbits were assessed immediately (NES1) and 24 h hours after (NES2) TBI and/or CVVH using a functional Neurological Evaluation Score (NES) and histology of the brains after sacrifice. There was evidence to support a difference of NES1 comparing with the TBI (−)-CVVH ( +), but not with TBI ( +)-CVVH (−) with only 15% of the rabbits treated with CVVH and TBI showing a favorable neurological course. The final neurological outcome (mortality at 24 h) was 0%, 22% and 53% in the TBI(−) + CVVH( +), TBI( +)-CVVH(−) and TBI( +)-CVVH( +) groups respectively. The use of hemofiltration before or after TBI did not make a difference in regards the outcome of the rabbits. There was evidence in the histology to support an increase of mild ischemia, hemorrhage and edema in the experimental group compared with the other two groups.

Conclusions

CVVH in rabbits without renal failure used with the intention to protect the brain may worsen the prognosis in TBI.

Continuous Rate Infusion of Ketamine Hydrochloride and Dexmedetomidine for Maintenance of Anesthesia during Laryngotracheal Surgery in New Zealand White Rabbits (Oryctolagus cuniculus)

New Zealand white rabbits (Oryctolagus cuniculus) are an established in vivo model for the study of structural and functional consequences of vocal-fold vibration. Research design requires invasive laryngotracheal procedures, and the presence of laryngospasms or pain responses (or both) hinder phonation-related data collection. Published anesthesia regimens report respiratory depression and muscle tone changes and have been unsuccessful in mitigating autonomic laryngeal responses in our protocol. Infusion of ketamine hydrochloride and dexmedetomidine hydrochloride in pediatric medicine provides effective analgesia and sedation for laryngotracheal procedures including intubation and bronchoscopy; however, data evaluating the use of ketamine-dexmedetomidine infusion in rabbits are unavailable. This study reports a new infusion regimen, which was used in 58 male New Zealand white rabbits that underwent a nonsurvival laryngotracheal procedure to induce phonotraumatic vocal-fold injury. Animals were sedated by using ketamine hydrochloride (20 mg/kg IM) and dexmedetomidine (0.125 mg/kg IM). Maintenance anesthesia was provided by using continuous rate intravenous infusion of ketamine hydrochloride (343 μg/kg/min) and dexmedetomidine (1.60 μg/kg/min). A stable plane of anesthesia with no autonomic laryngeal response (laryngospasm) was achieved in 32 of the 58 rabbits (55%). Laryngospasms occurred in 25 of 58 animals (43%) and were controlled in 20 cases (80%) by providing 0.33 mL 2% topical lidocaine, incremental increase in infusion rate, or both. Continuous rate infusion of ketamine hydrochloride-dexmedetomidine with prophylactic topical lidocaine provides a predictable and adjustable surgical plane of anesthesia, with minimal confounding respiratory and autonomic laryngeal responses, during extended-duration laryngotracheal surgery in rabbits. This regimen should be considered as an alternative to injection maintenance for prolonged, invasive procedures.

Pharmacokinetics, absolute bioavailability and tolerability of ketamine after intranasal administration to dexmedetomidine sedated dogs

Intranasal ketamine has recently gained interest in human medicine, not only for its sedative, anaesthetic or analgesic properties, but also in the management of treatment resistant depression, where it has been shown to be an effective, fast acting alternative treatment. Since several similarities are reported between human psychiatric disorders and canine anxiety disorders, intranasal ketamine could serve as an alternative treatment for anxiety disordered dogs. However, to the authors knowledge, intranasal administration of ketamine and its pharmacokinetics have never been described in dogs. Therefore, this study aimed to examine the pharmacokinetics, absolute bioavailability and tolerability of intranasal ketamine administration compared with intravenous administration. Seven healthy, adult laboratory Beagle dogs were included in this randomized crossover study. The dogs received 2 mg/kg body weight ketamine intravenously (IV) or intranasally (IN), with a two-week wash-out period. Prior to ketamine administration, dogs were sedated intramuscularly with dexmedetomidine. Venous blood samples were collected at fixed times until 480 min post-administration and ketamine plasma concentrations were determined by liquid chromatography-tandem mass spectrometry. Cardiovascular parameters and sedation scores were recorded at the same time points. Non-compartmental pharmacokinetic analysis revealed a rapid (Tmax = 0.25 ± 0.14 h) and complete IN bioavailability (F = 147.65 ± 49.97%). Elimination half-life was similar between both administration routes (T1/2el IV = 1.47 ± 0.24 h, T1/2el IN = 1.50 ± 0.97 h). Heart rate and sedation scores were significantly higher at 5 and 10 min following IV administration compared to IN administration, but not at the later time-points.

Anaesthetic and Perioperative Management of 14 Male New Zealand White Rabbits for Calvarial Bone Surgery

Simple Summary

Bone substitutes are commonly used when bone grafts are necessary in human craniofacial surgery. To study the properties and biologic behaviour of those substitutes, they can be implanted in experimental animals. A frequently used model involves the creation of critical-sized defects (defects that are too large to heal by themselves) in the rabbits calvaria (the top part of the skull). The procedure was initially described in 1989 and the authors considered and reported that post-operative analgesia was not necessary. In our experience, this procedure is invasive and can result in severe postoperative pain. The anaesthetic management of rabbits undergoing this procedure is challenging. Most of the recent publications using this model fail to provide sufficient information on perioperative animal management. With this report we have aimed to document a possible practical and simple anaesthetic and postoperative management of rabbits undergoing this procedure. Particular emphasis has been placed on postoperative pain assessment, duration and treatment.

Abstract

Calvarial bone surgery on rabbits is frequently performed. This report aims to document a simple and practical anaesthetic and perioperative management for this procedure. Fourteen male New Zealand white rabbits were included in the study. Subcutaneous (SC) dexmedetomidine, ketamine and buprenorphine ± isoflurane vaporized in oxygen administered through a supraglottic airway device (V-gel^®) provided clinically suitable anaesthesia. Supplemental oxygen was administered throughout recovery. Monitoring was clinical and instrumental (pulse-oximetry, capnography, invasive blood pressure, temperature, arterial blood gas analysis). Lidocaine was infiltrated at the surgical site and meloxicam was injected subcutaneously as perioperative analgesia. After surgery, pain was assessed five times daily (composite behavioural pain scale and grimace scale). Postoperative analgesia included SC meloxicam once daily for four days and buprenorphine every 8 h for three days (unless both pain scores were at the lowest possible levels). Rescue analgesia (buprenorphine) was administered in case of the score > 3/8 in the composite pain scale, >4/10 on the grimace scale or if determined necessary by the caregivers. Airway management with a V-gel^® was possible but resulted in respiratory obstruction during the surgery in two cases. Hypoventilation was observed in all rabbits. All rabbits experienced pain after the procedure. Monitoring, pain assessments and administration of postoperative analgesia were recommended for 48 h.

Peri-anaesthetic mortality and nonfatal gastrointestinal complications in pet rabbits: a retrospective study on 210 cases

OBJECTIVE

The aim of this study was to determine the incidence and the associated risk factors of peri-anaesthetic mortality and gastrointestinal complications in pet rabbits.

STUDY DESIGN

Retrospective cohort study.

ANIMALS

A total of 185 pet rabbits admitted to the Exotic Referal Service of Beaumont Sainsbury's Animal Hospital over the period 2009-2016.

METHODS

The clinical records of the rabbits were obtained from the database. To evaluate the incidence of peri-anaesthetic mortality, three possible outcomes were considered: alive, dead or euthanized within the 72 hours following the anaesthetic event. Food intake and stool production during the first 72 hours following the anaesthetic event were evaluated to investigate the occurrence of gastrointestinal complications. Thereafter, various hypothesized risk factors, including administration of alpha-2 agonists, body weight, American Society of Anaesthesiologists classification and endotracheal intubation were tested against peri-anaesthetic mortality and gastrointestinal complications, with both univariate and multivariate binary logistic regression.

RESULTS

Twenty-five out of 185 rabbits underwent two anaesthetic events; therefore, data from 210 cases were used. Of these 210 cases, six died during sedation or general anaesthesia and four (one of which euthanized) died during the first 72 postoperative hours, accounting for an actual mortality rate equal to 4.8% (95% confidence interval, 0.025-0.086). Peri-anaesthetic gastrointestinal complications developed in 77 (38%) out of the 204 anaesthetic events whose outcome was not intraoperative death (95% confidence interval, 0.314-0.446). Species-specific risk factors could not be identified for peri-anaesthetic mortality; however, the odds for post-anaesthetic gastrointestinal complications increased significantly with body weight (p = 0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings confirm that rabbits continue to have a higher incidence of peri-anaesthetic mortality than dogs and cats, and highlight a high risk for nonfatal peri-anaesthetic gastrointestinal complications in this species.

Rabbit Neutering in Primary-Care Education: Insights from a Surgical Clinic

Involvement in canine and feline surgical neutering clinics is generally considered to be a key element of primary-care veterinary education, yet opportunities for veterinary students to develop their surgical skills with rabbit patients are uncommon. This is despite the fact that rabbits are currently estimated to be the third most popular companion animal species and the fact that the British Small Animal Veterinary Association (BSAVA) recommends that all non-breeding rabbits be neutered soon after they attain sexual maturity. We describe a pilot rabbit-neutering clinic designed to provide high-quality care for rabbit patients while offering opportunities for undergraduate surgical and case-management skills development. We report on the clinical outcomes for patients. Rates of morbidity (n=18) and mortality (n=1) were low. Of complications reported, the majority (n=16) were considered minor. Challenges included ensuring that staff and students were trained in the specific features of rabbit anesthesia and recovery behavior. We conclude that rabbit surgical clinics offer excellent learning opportunities for undergraduate veterinary students. With prior training in handling and close individual supervision, it is possible to achieve good clinical outcomes and to have a positive impact on the welfare of companion animal populations.

Clinical evaluation of intranasal medetomidine-ketamine and medetomidine-S(+)-ketamine for induction of anaesthesia in rabbits in two centres with two different administration techniques

OBJECTIVE

The aim was to compare efficacy and side effects of induction with medetomidine-ketamine or medetomidine-S(+)-ketamine by intranasal (IN) instillation in rabbits and to evaluate both protocols during subsequent isoflurane anaesthesia.

STUDY DESIGN

Prospective, blinded, randomized experimental study in two centres.

ANIMALS

Eighty-three healthy New Zealand White rabbits undergoing tibial or ulnar osteotomy.

METHODS

Medetomidine (0.2 mg kg^-1) with 10 mg kg^-1 ketamine (MK) or 5 mg kg^-1 S(+)-ketamine (MS) was administered IN to each rabbit in a randomized fashion. In Centre 1 (n = 42) rabbits were held in sternal recumbency, and in Centre 2 (n = 41) in dorsal recumbency, during drug instillation. Adverse reactions were recorded. If a rabbit swallowed during endotracheal intubation, half of the initial IN dose was repeated and intubation was re-attempted after 5 minutes. Anaesthesia was maintained with isoflurane. Heart rate, blood pressure, endtidal carbon dioxide concentration and blood gases were recorded. Data were analysed using Student's t-test, Mann-Whitney test and Fisher's exact test.

RESULTS

In all, 39 animals were assigned to the MK group and 44 to the MS group. Two rabbits in the MS group held in dorsal recumbency died after instillation of the drug. Eight (MK) and 11 rabbits (MS) were insufficiently anaesthetized and received a second IN dose. One rabbit in MK and three in MS required an isoflurane mask induction after the second IN dose. There were no significant differences between treatments for induction, intraoperative data, blood gas values and recovery data.

CONCLUSION AND CLINICAL RELEVANCE

This study indicated that medetomidine-ketamine and medetomidine-S(+)-ketamine were effective shortly after IN delivery, but in dorsal recumbency IN administration of S(+)-ketamine led to two fatalities. Nasal haemorrhage was noted in both cases; however, the factors leading to death have not been fully elucidated.

Comparison of S(+)-ketamine and ketamine, with medetomidine, for field anaesthesia in the European brown hare (Lepus europaeus)

OBJECTIVE

To compare anaesthesia and recovery parameters of racemic ketamine or S(+)-ketamine in combination with medetomidine for intramuscular (IM) field anaesthesia in the European brown hare (EBH) (Lepus europaeus).

STUDY DESIGN

Randomized, prospective, blinded clinical trial.

ANIMALS

20 adult EBH (eight male, 12 female), mean ± SD weight 3360 341).

METHODS

Medetomidine (0.2 mg kg(-1) ) and ketamine (30 mg kg(-1) ) (K-M group) or S(+)-ketamine (15 mg kg(-1) ) (S-M group) were administered by IM injection. Time until first effect and loss of righting reflex were recorded. During sedation and anaesthesia heart rate, saturation of arterial haemoglobin, respiratory rate, side stream end tidal CO(2) (Pe'CO(2) ), non invasive blood pressure, body temperature, cardiorespiratory parameters, palpebral reflex, jaw tone and nociception were recorded every 5 minutes. Medetomidine was antagonized with IM atipamezole (1 mg kg(-1) ) 45 minutes after treatment injection. Time until first head lift, standing and total recovery time (T-Recov) were recorded. Incidences of falling and involuntary movements during recovery were counted. Recovery quality was scored by visual analogue scale. Descriptive statistics were used to visualize maintenance data. All other data were included in multiple linear regression models.

RESULTS

Surgical anesthesia was not produced reliably with either protocol. Hypoxaemia occurred in both groups (SpO(2) < 90%). During recovery, falling was noted significantly less often (p < 0.001) in the S-M group (13 ± 7) versus the K-M group (27 ± 13). T-Recov was long, lasting for more than 3 hours in individuals with no significant differences between groups.

CONCLUSION AND CLINICAL RELEVANCE

S(+)-ketamine showed only minor advantages over racemic ketamine. Surgical anaesthesia was not achieved reliably with either protocol. Oxygen supplementation should be considered to prevent hypoxaemia. Further research is needed to develop an injectable field protocol adequate for surgical procedures, but with a rapid smooth recovery.

Anaesthesia with a combination of ketamine and medetomidine in the rabbit: effect of premedication with buprenorphine

OBJECTIVE

To assess the effects of premedication with buprenorphine on the characteristics of anaesthesia induced with ketamine/medetomidine.

STUDY DESIGN

Prospective crossover laboratory study.

ANIMALS

Six female New Zealand White rabbits.

METHODS

Rabbits received, on occasions separated by 7 days, either buprenorphine (0.03 mg kg(-1)) or saline subcutaneously (SC) as premedication, followed 1 hour later by SC ketamine (15 mg kg(-1)) and medetomidine (0.25 mg kg(-1)) (K/M). At pre-determined time points reflex responses and cardiopulmonary parameters were recorded and arterial blood samples taken for analysis. Total sleep time was the duration of loss of the righting reflex. Duration of surgical anaesthesia was the time of suppression of the ear pinch and pedal withdrawal reflexes. Wilcoxon signed-ranks tests were used to compare data before (T(0)) and 10 minutes after (T(10)) injection with K/M.

RESULTS

All animals lost all three reflex responses within 10 minutes of injection of K/M. The duration of loss of these reflexes significantly increased in animals that received buprenorphine. At induction, animals that had received buprenorphine tended to have a lower respiration rate but there were no significant differences in arterial PCO(2), PO(2) or pH between treatments. Hypoxaemia [median PaO(2) < 6.0 kPa (45 mmHg)] developed in both treatments at T(10) but there was no significant difference between treatments. Mean arterial pressure (MAP) was lower at T(10) in animals that had received buprenorphine.

CONCLUSION AND CLINICAL RELEVANCE

Premedication with buprenorphine significantly increased the duration of anaesthesia induced by K/M, with no significant depression of respiration further to the control treatment within the first 10 minutes of anaesthesia. The MAP decreased but this was not reflected in a difference in other physiological parameters. These data show that premedication with buprenorphine, before K/M anaesthesia in the rabbit, has few negative effects and may provide beneficial analgesia.

Atipamezole changes the antinociceptive effects of butorphanol after medetomidine-ketamine anaesthesia in rats

OBJECTIVE

To investigate the effects of atipamezole administered before butorphanol, on tail-flick latency (TFL) and also following medetomidine-ketamine anaesthesia in rats.

STUDY DESIGN

Prospective, randomized experimental study.

ANIMALS

Thirty-four adult male Sprague-Dawley rats weighing 260-390 g.

METHODS

TFL in 50 degrees C water was used to measure antinociception. In the first experiment, rats received saline (n = 5) or atipamezole (n = 5) followed by butorphanol treatments. In the second experiment, three groups of rats received saline (n = 8), atipamezole (n = 8) or atimpamezole (n = 8) followed by butorphanol 60 minutes after medetomidine-ketamine administration.

RESULTS

In the first experiment, butorphanol significantly increased TFL compared to baseline. Atipamezole significantly decreased this effect. In the second experiment, TFL was significantly increased after recovery from medetomidine-ketamine anaesthesia compared to baseline. This was almost completely blocked by atipamezole. Atipamezole with butorphanol after recovery from the anaesthesia significantly reduced TFL compared to saline but still significantly increased TFL compared to the baseline.

CONCLUSION AND CLINICAL RELEVANCE

Atipamezole attenuated the analgesic effects of butorphanol. When postoperative atipamezole is used to hasten recovery from anaesthesia in rats, it may interfere with the postoperative analgesic effect of butorphanol.

Cardiovascular physiology and diseases of the rabbit

This article reviews what is known about the diagnosis and management of cardiovascular diseases in the pet rabbit. Current knowledge is based on anecdotal reports, derived from research data using the rabbit as an animal model of human cardiovascular diseases, but most importantly canine and feline cardiology. It is likely that, as cardiovascular diseases are more often recognized, more specific information will soon become available for the treatment of the pet rabbit with cardiac disease.

A comparison of ketamine-midazolam and ketamine-medetomidine combinations for induction of anaesthesia in rabbits

OBJECTIVE

To compare ketamine-midazolam (KMZ) and ketamine-medetomidine (KMT) anaesthesia in rabbits using anaesthetic induction, maintenance and recovery data.

STUDY DESIGN

Randomized, prospective, blinded clinical trial.

ANIMALS

Fifty rabbits (25 male, 25 female) of different breeds undergoing ovariohysterectomy or castration. Rabbits were 12.7 +/- 9.8 months old with body mass 2.24 +/- 0.61 kg.

STUDY DESIGN

Randomized, prospective, blinded clinical trial.

METHODS

Ketamine (15 mg kg(-1)) and midazolam (3 mg kg(-1)) or medetomidine (0.25 mg kg(-1)) were administered by intramuscular (IM) injection. Ten minutes after IM injection, blind intubation of the trachea was attempted. The time taken, the number of attempts and a subjective score of the ease of intubation were recorded. Isoflurane (range 0-3.6%) in 100% oxygen was delivered via a Jackson Rees modification of an Ayre's T-piece non-rebreathing system. Carprofen (3 mg kg(-1)) and dextrose saline (5 mL kg(-1) hour(-1)) were administered intravenously (IV). During surgery heart rate (HR), respiratory rate (RR) and arterial oxygen saturation of haemoglobin (SpO(2)) were monitored. Times to extubation and first head lift were recorded. Group KMT received atipamezole (0.5 mg kg(-1)) IM 30 minutes after discontinuation of isoflurane. Activity was scored at 30, 60 and 120 minutes after volatile agent discontinuation. Mean time to loss of righting reflex (LRR), body mass, RR and vaporizer setting were compared using a two-tailed t-test. Median values for all other data were compared using a Mann-Whitney test.

RESULTS

Mean time to LRR (+/-SD) was significantly shorter with KMT (1.64 +/- 0.55 minutes) compared with KMZ (2.28 +/- 0.66 minutes). Intubation was not possible in seven rabbits (three with KMT, four with KMZ) and three with KMT developed laryngospasm. Mean HR, SpO(2) and vaporizer settings were all significantly lower in group KMT.

CONCLUSION AND CLINICAL RELEVANCE

KMT has a faster onset of action and a greater isoflurane-sparing effect when compared with KMZ. Rabbits with KMT were more prone to laryngospasm and had significantly lower HR.

Peri-operative body temperatures in isoflurane-anaesthetized rabbits following ketamine-midazolam or ketamine-medetomidine

OBJECTIVE

To investigate alterations in peri-operative body temperatures and oesophageal-skin temperatures in isoflurane-anaesthetized rabbits following either ketamine-midazolam or ketamine-medetomidine induction of anaesthesia.

ANIMAL POPULATION

Fifty client-owned rabbits, (25 male, 25 female) of different breeds anaesthetized for elective neutering (age range: 3-42 months; mass range: 1.15-4.3 kg).

STUDY DESIGN

Randomized, blinded clinical study.

METHODS

Pre-anaesthetic rectal temperature was measured. A 24 SWG catheter was placed in a marginal ear vein after local anaesthesia. Ketamine (15 mg kg(-1)) with medetomidine (0.25 mg kg(-1)) (group KMT) or with midazolam (3 mg kg(-1)) (group KMZ) was injected intramuscularly (IM). Following endotracheal intubation anaesthesia was maintained with isoflurane in oxygen. Carprofen (3 mg kg(-1)) and glucose saline (5 mL kg(-1) hour(-1)) were administered through the intravenous catheter. Room temperature and humidity, skin temperature (from tip of pinna) and oesophageal temperature were measured during anaesthesia. Ovariohysterectomy or castration was performed. Rectal temperature was taken when isoflurane was discontinued (time zero) and 30, 60 and 120 minutes thereafter. Atipamezole (0.5 mg kg(-1)) was administered IM to rabbits in group KMT at zero plus 30 minutes. Mass, averaged room temperature and duration of anaesthesia data were compared using a two-tailed t-test. Age, averaged room humidity, rectal temperature decrease, oesophageal temperature decrease and oesophageal-skin difference data were compared using a Kruskal-Wallis test. p < 0.05 was considered significant.

RESULTS

The averaged oesophageal-skin temperature difference was significantly greater in group KMT [median 9.85 degrees C (range 6.42-13.85 degrees C)] than in group KMZ [4.38 degrees C (2.83-10.43 degrees C)]. Rectal temperature decreased over the anaesthetic period was not significantly different between the two groups; however, oesophageal temperature decrease was significantly less in group KMT [1.1 degrees C (-0.1-+2.7 degrees C)] than in group KMZ [1.4 degrees C (0.6-3.1 degrees C)].

CONCLUSIONS

Oesophageal-skin temperature difference is larger in rabbits anaesthetized with ketamine-medetomidine combination than ketamine-midazolam.

CLINICAL RELEVANCE

The oesophageal temperature in rabbits anaesthetized with ketamine-medetomidine and isoflurane decreases significantly less than in animals anaesthetized with ketamine-midazolam and isoflurane, during anaesthesia.