A comparative study of medetomidine/ketamine and xylazine/ketamine anaesthesia in dogs

The anaesthetic and physiological effects of a combination of 40 micrograms medetomidine with 2.5 ketamine, 5.0 or 7.5 mg/kg administered intramuscularly were compared with the effects of a combination of 1 mg/kg xylazine and 15 mg/kg ketamine. All the combinations rapidly induced an anaesthetic state that permitted endotracheal intubation, with the absence of the pedal reflex and with good muscle relaxation, and induced bradycardia that was less pronounced as the dose of ketamine was increased. All the combinations produced a decrease in respiratory rate. Increasing the dose of ketamine combined with medetomidine resulted in a very significant prolongation of the duration of anaesthesia, the duration of muscle relaxation and the arousal time. The duration of the anaesthetic effects of 40 micrograms/kg medetomidine with 5 mg/kg ketamine was comparable to that provided by the recommended xylazine/ketamine combination but the period of muscle relaxation was significantly longer. The recovery from medetomidine/ketamine took longer than recovery from xylazine/ketamine but there were fewer side effects.     

An evaluation of medetomidine/ketamine and other drug combinations for anaesthesia in cats

The anaesthesia induced by cyclohexylamine derivatives in cats was studied by comparing the effects induced by four pairs of agents: acepromazine/ketamine, xylazine/ketamine, zolazepam/tiletamine and medetomidine/ketamine. Acepromazine/ketamine was free of undesirable side effects but provided inadequate anaesthetic cover. The other combinations differed only in the dosage, the quality of the anaesthesia and the importance of the side effects. Medetomidine/ketamine was the best combination; it induced a good degree of anaesthesia with small doses and was free of major side effects.     

Antagonistic activities of atipamezole, 4-aminopyridine and yohimbine against medetomidine/ketamine-induced anaesthesia in cats

The objectives of this trial were to determine the ability of atipamezole, 4-aminopyridine and yohimbine to reverse the anaesthetic effects of a combination of medetomidine and ketamine in cats. Forty healthy cats were anaesthetised with 80 micrograms/kg medetomidine combined with 5 mg/kg ketamine. Thirty minutes later atipamezole (200 or 500 micrograms/kg), 4-aminopyridine (500 or 1000 micrograms/kg) or yohimbine (250 or 500 micrograms/kg) were injected intramuscularly. The doses of antagonists were randomised, so that each dose was administered to five cats, and 10 cats were injected only with physiological saline. Atipamezole clearly reversed the anaesthesia and bradycardia induced by medetomidine and ketamine. The mean (+/- sd) arousal times were 28 (+/- 4.7), 5.8 (+/- 1.8) and 7 (+/- 2.1) minutes in the placebo group, and the groups receiving 200 and 500 micrograms/kg atipamezole, respectively. The heart rates of the cats receiving 200 micrograms/kg atipamezole rapidly returned to values close to the initial ones, but 15 minutes after the injection of 500 micrograms/kg atipamezole a significant tachycardia was observed. All the cats showed moderate signs of ataxia during the recovery period. A dose of 500 micrograms/kg yohimbine also clearly reversed the anaesthetic effects of medetomidine/ketamine but 250 micrograms/kg was not effective. The dose of 500 micrograms/kg allowed a smooth recovery with no particular side effects except for some signs of incomplete antagonism of the ketamine effects, ie, ataxia and muscular incoordination. With 4-aminopyridine there were no statistically significant effects on the recovery, or the heart and respiratory rates of the cats anaesthetised with medetomidine/ketamine.     

Anaesthesia with midazolam/medetomidine/fentanyl in chinchillas (Chinchilla lanigera) compared to anaesthesia with xylazine/ketamine and medetomidine/ketamine

We studied four different drug regimes for anaesthetic management in chinchillas and evaluated and compared their cardiovascular and respiratory effects. In this randomized, cross-over experimental study, seven adult chinchillas, five females, two males [515 +/- 70 (SD) g] were randomly assigned to one of the following groups: group 1 [midazolam, medetomidine and fentanyl (MMF), flumazenil, atipamezole and naloxone (FAN); MMF-FAN] received 1.0 mg/kg midazolam, 0.05 mg/kg medetomidine and 0.02 mg/kg fentanyl i.m., and for reversal 0.1 mg/kg flumazenil, 0.5 mg/kg atipamezole and 0.05 mg/kg naloxone s.c. after 45 min; group 2 (MMF) 1.0 mg/kg midazolam, 0.05 mg/kg medetomidine and 0.02 mg/kg fentanyl i.m.; group 3 [xylazine/ketamine (X/K)] 2.0 mg/kg xylazine and 40.0 mg/kg ketamine i.m.; and group 4 [medetomidine/ketamine (M/K)] 0.06 mg/kg medetomidine and 5.0 mg/kg ketamine i.m. Reflexes were judged to determine anaesthetic stages and planes. Anaesthesia with X/K and M/K was associated with a prolonged surgical tolerance and recovery period. By reversing MMF, recovery period was significantly shortened (5 +/- 1.3 min versus 40 +/- 10.3 min in MMF without FAN, 73 +/- 15.0 min in X/K, and 31 +/- 8.5 min in M/K). Without reversal, MMF produced anaesthesia lasting 109 +/- 16.3 min. All combinations decreased respiratory and heart rate but compared with X/K and M/K, respiratory and cardiovascular complications were less in the MMF groups. Focussing on the clinical relevance of the tested combinations, completely reversible anaesthesia showed two major advantages: anaesthesia can be antagonized in case of emergency and routinely shortens recovery. In small animals particularly these advantages lead to less complications and discomfort and thus often can be lifesaving. As all analgesic components (medetomidine and fentanyl) are reversed, postoperative analgesia should be provided before reversal of anaesthesia.     

Sedative effects of medetomidine in pigs.

Sedative effects of medetomidine, a potent selective and specific alpha 2-adrenoceptor agonist, were evaluated in pigs using 5 different doses (30, 50, 80, 100 and 150 micrograms/kg of body weight) and compared with those of xylazine (2 mg/kg). Atropine (25 micrograms/kg) was mixed with both drugs to prevent severe bradycardia. All drugs were administered intramuscularly. Medetomidine at a dosage of 30 micrograms/kg produced more potent sedation than xylazine. The depth of sedation induced by medetomidine was dose dependent within the range from 30 to 80 micrograms/kg. At 100 or 150 micrograms/kg, the depth of sedation was mostly the similar level to that at 80 micrograms/kg but the duration was prolonged. The degree of muscle relaxation produced by medetomidine also seemed to be dose dependent from 30 to 80 micrograms/kg and was stronger than that produced by xylazine. An increase in the duration of muscle relaxation was dose dependent up to 150 micrograms/kg. No analgesic effect was produced by xylazine, however moderate analgesia was obtained by medetomidine. There were no marked changes in heart rate and respiratory rate during the observation period in pigs of any groups, however mild hypothermia after the administration of both drugs was observed. From these results, medetomidine has a significant and dose-dependent sedative effects which are much more potent than that of xylazine, and a combination of 80 micrograms/kg of medetomidine and 25 micrograms/kg of atropine is suitable for sedation with lateral recumbency and moderate muscle relaxation without notable side effects in pigs.     

Clinical evaluation of medetomidine, a novel sedative and analgesic drug for dogs and cats

Medetomidine, a potent alpha 2-adrenoceptor agonist, was investigated in open, multicenter clinical trials with patients of various canine and feline breeds (1736 dogs and 678 cats). The purpose of the study was to find an optimal dose of medetomidine for sedation and analgesia in clinical practice and to study how well the intended procedure could be performed under the influence of the drug. The mean dose (i.m.) of medetomidine used for examinations, clinical procedures and minor surgical interventions was 40 micrograms/kg, and for radiography 30 micrograms/kg. In cats the dose was 80-110 micrograms/kg. On the doses chosen, almost all animals were recumbent and 72% of the dogs and 85% of the cats were in a slight anaesthetic stage, unable to rise. The evaluation of the overall suitability of medetomidine (% of cases) in different indications was "very satisfactory" or "satisfactory" in 95% of dogs and 81-96% of cats. Side effects reported were limited almost exclusively to vomiting and muscle jerking in dogs (12% and 0.5% of the cases) and to vomiting in cats (65%). Medetomidine seems to suffice for pharmacological restraint of dogs and cats. The concomitant use of medetomidine (80-100 micrograms/kg) and ketamine (7 mg/kg) in cats (n = 295) provided a good anaesthesia (20-40 min). The recovery was smooth. The present study shows that medetomidine provides an effective level of sedation and analgesia for clinical use.     

Total intravenous anaesthesia with propofol or propofol/ketamine in spontaneously breathing dogs premedicated with medetomidine

The cardiorespiratory parameters, the depth of anaesthesia and the quality of recovery were evaluated in six spontaneously breathing dogs that had been premedicated with medetomidine (40 microg/kg, supplemented with 20 microg/kg an hour later), administered with either propofol (1 mg/kg followed by 0.15 mg/kg/minute, intravenously), or with ketamine (1 mg/kg followed by 2 mg/kg/hour, intravenously) and propofol (0.5 mg/kg followed by 0.075 mg/kg/minute, intravenously). The dogs' heart rate and mean arterial blood pressure were higher and their minute volume of respiration and temperature were lower when they were anaesthetised with propofol plus ketamine, and a progressive hypercapnia leading to respiratory acidosis was more pronounced. When the dogs were anaesthetised with propofol/ketamine they recovered more quickly, but suffered some unwanted side effects. When the dogs were anaesthetised with propofol alone they recovered more slowly but uneventfully.     

Clinicophysiological Effects of Spinally Administered Ketamine and Its Combination with Xylazine and Medetomidine in Healthy Goats

The study was conducted in 9 healthy adult goats of either sex, weighing 15–20 kg, to evaluate and compare the clinicophysiological effects of spinally administered ketamine alone and in combination with xylazine and medetomidine. Nine trials each of the three treatments were conducted randomly by injecting ketamine (2.5 mg/kg) (n = 9), ketamine and xylazine (2.5 mg/kg and 0.05 mg/kg) (n = 9) and ketamine and medetomidine (2.5 mg/kg and 10 μg/kg) (n = 9). The drugs were administered at the lumbosacral subarachnoid space under strict aseptic conditions. The treatments were evaluated on the basis of clinicophysiological, haematological, biochemical and haemodynamic observations. Ketamine produced mild to moderate analgesia of the hindquarters. Its combination with either xylazine or medetomidine produced complete analgesia of the hindquarters for 45–60 min. Ataxia was moderate in the ketamine group, whereas animals attained sternal recumbency in the combination groups. A moderate degree of sedation was recorded in the combination groups. Heart rate and respiratory rate depression in the combination groups and heart rate and respiratory rate stimulation in ketamine group were recorded. Haematological parameters decreased in all the groups. Increase in serum glucose, creatinine and urea nitrogen was recorded in all the groups. Serum electrolytes did not show any significant change. The results showed that the combination of ketamine with xylazine or medetomidine at these dose rates produced a comparable degrees of analgesia of hindquarters with transient and minimal cardiopulmonary side effects.     

Xylazine and ketamine anaesthesia in the dromedary camel under field conditions

The effects of either xylazine (0.25 mg/kg) intramuscularly, ketamine (5.5 mg/kg) intramuscularly, or a mixture of xylazine (0.15 mg/kg) and ketamine (2.5 mg/kg) intramuscularly on sedation, analgesia, cardiac and respiratory rates, body temperature and muscle relaxation were studied in the domesticated dromedary camel. Either drug used separately was suitable for sedation and analgesia in the camel. However, the mixture of xylazine and ketamine was superior to either drug used alone. Camels which received the combination of xylazine and ketamine had fewer effects on cardiac and respiratory rates and better analgesia. In addition, they showed better muscle relaxation, less central nervous system irritability and shorter recovery times than camels sedated with ketamine alone.     

Anaesthetic and cardiopulmonary effects of intramuscular morphine, medetomidine and ketamine administered to telemetered cats

The quality and duration of anaesthesia, cardiorespiratory effects and recovery characteristics of a morphine, medetomidine, ketamine (MMK) drug combination were determined in cats. Six healthy, adult female cats were administered 0.2 mg/kg morphine sulphate, 60 microg/kg medetomidine hydrochloride, and 5 mg/kg ketamine hydrochloride intramuscularly. Atipamezole was administered intramuscularly at 120 min after MMK administration. Time to lateral recumbency, intubation, extubation and sternal recumbency were recorded. Cardiorespiratory variables and response to a noxious stimulus were recorded before and at 3 min and 10 min increments after drug administration until sternal recumbency. The time to lateral recumbency and intubation were 1.9+/-1.2 and 4.3+/-1.2 min, respectively. Body temperature and haemoglobin saturation with oxygen remained unchanged compared to baseline values throughout anaesthesia. Respiratory rate, tidal volume, minute volume, heart rate, and blood pressure were significantly decreased during anaesthesia compared to baseline values. One cat met criteria for hypotension (systolic blood pressure <90 mmHg). End tidal carbon dioxide increased during anaesthesia compared to baseline values. All but one cat remained non-responsive to noxious stimuli from 3 to 120 min. Time to extubation and sternal recumbency following atipamezole were 2.9+/-1.1 and 4.7+/-1.0 min, respectively. MMK drug combination produced excellent short-term anaesthesia and analgesia with minimal cardiopulmonary depression. Anaesthesia lasted for at least 120 min in all but one cat and was effectively reversed by atipamezole.     

USE OF MEDETOMIDINE AS A PREANAESTHETIC IN BIRDS

Medetomidine, an α₂-adrenoceptor agonist, was used to balance ketamine anaesthesia in birds. Twenty zebra doves weighing 40 to 60 g were equally divided into 2 groups. Group 1 was used to evaluate the effects of 100 mg/kg of 5% ketamine and of 0.1 mg/kg of 0.005% medetomidine in combination with 100 mg/kg of 5% ketamine. Group 2 was used to study the effects of 200 mg/kg of 5% ketamine and of 30 mg/kg of 1% pentobarbital. All injections were made intramuscularly. Medetomidine-ketamine combination provided better analgesia, deeper anaesthesia, and smoother recovery with less wing flapping than with ketamine alone. The anaesthetic effect of the combination was comparable to that of pentobarbital but recovery was smoother. The selection of preanesthetic and anaesthetic medications is one of the problems associated with avian surgery. Medetomidine is a new sedative compound whose effect is mediated via the stimulation of the central α₂-adrenoceptors. It provides analgesic and sedative or anaesthetic effects in dogs and cats (Vähä, 1989) and sedative effect in zebra doves (Cherdchanpipat et al., 1989). This study was designed to evaluate the effect of medetomidine in combination with ketamine, the anaesthetic of choice for a number of avian species. The combination effect was compared with the effect of ketamine given alone, and with the effect of pentobarbital, the anaesthetic used successfully for decades by a number of practitioners.     

Anesthesia of wood bison with medetomidine-zolazepam/tiletamine and xylazine-zolazepam/tiletamine combinations

This study was designed to evaluate 2 combinations for immobilization of bison. Seven wood bison received 1.5 mg/kg body weight (BW) of xylazine HCl + 1.5 mg/kg BW of zolazepam HCl and 1.5 mg/kg BW of tiletamine HCl on one occasion. The bison received 60 micrograms/kg BW of medetomidine HCl + 0.6 mg/kg BW of zolazepam HCl and 0.6 mg/kg BW of tiletamine HCL on another occasion. Xylazine was antagonized with 3 mg/kg BW of tolazoline HCl and medetomidine HCl was antagonized with 180 micrograms/kg (BW) of atipamezole HCl. Temporal characteristics of immobilization and physiological effects (acid-base status, thermoregulatory, cardiovascular, and respiratory effects) of the drug combinations were compared. Induction was significantly faster with xylazine HCl-zolazepam HCl/tiletamine HCl. Recovery following antagonist administration was significantly faster with medetomidine HCl-zolazepam HCl/tiletamine HCl. The average drug volumes required were 7.00 mL of xylazine HCl-zolazepam HCl/tiletamine HCL and 2.78 mL of medetomidine HCl-zolazepam HCl/tiletamine HCl. Hypoxemia, hypercarbia, and rumenal tympany were the major adverse effects with both drug combinations.     

Comparison of quality of induction of anaesthesia between intramuscularly administered ketamine, intravenously administered ketamine and intravenously administered propofol in xylazine premedicated cats

The quality of induction of general anesthesia produced by ketamine and propofol, 2 of the most commonly used anaesthetic agents in cats, was assessed. Eighteen cats admitted for elective procedures were randomly assigned to 3 groups and then premedicated with xylazine 0.75 mg/kg intramuscularly before anaesthesia was induced with ketamine 15 mg/kg intramuscularly (KetIM group), ketamine 10 mg/kg intravenously (KetIV group) or propofol 4 mg/kg intravenously (PropIV group). Quality of induction of general anaesthesia was determined by scoring ease of intubation, degree of struggling, and vocalisation during the induction period. The quality of induction of anaesthesia of intramuscularly administered ketamine was inferior to that of intravenously administered ketamine, while intravenously administered propofol showed little difference in quality of induction from ketamine administered by both the intramuscular and intravenous routes. There were no significant differences between groups in the ease of intubation scores, while vocalisation and struggling were more common in cats that received ketamine intramuscularly than in those that received intravenously administered ketamine or propofol for induction of anaesthesia. Laryngospasms occurred in 2 cats that received propofol. The heart rates and respiratory rates decreased after xylazine premedication and either remained the same or decreased further after induction for all 3 groups, but remained within normal acceptable limits. This study indicates that the 3 regimens are associated with acceptable induction characteristics, but administration of ketamine intravenously is superior to its administration intramuscularly and laryngeal desensitisation is recommended to avoid laryngospasms.     

Anaesthesia of roan antelope (Hippotragus equinus) with a combination of A3080, medetomidine and ketamine

A dose range was determined for anaesthesia of 20 recently boma-captured roan antelope (Hippotragus equinus) with the synthetic opiate A3080 combined with medetomidine and ketamine. A dose of 10-30 micro/kg A3080 (x = 20+/-8 microg/kg) combined with 5-21 microg/kg medetomidine (x = 13+/-7 microg/kg) plus 0.29-1.11 mg/kg ketamine (x = 0.71+/-0.24 mg/kg) was found to be safe and effective for the field conditions in this study. The anaesthesia produced by this drug combination was predictable and characterised by a short induction time, good muscle relaxation, and acceptable physiological parameters for anaesthesia periods ranging from 49-103 min (x = 64+/-19 min). The wide range (3-4-fold) of doses with acceptable results is also an indication that this drug combination has a wide margin of safety in roan antelope, making it desirable for field use. When 2 dose levels (2-3-fold dif ference) were retrospectively evaluated, no statistical difference was found in induction times, and no observable clinical differences in the anaesthetic episodes were seen. Based on this study, the recommended dose range in roan antelope for this combination is 10-13 microg/kg A3080, 5-6 microg/kg medetomidine and 0.3-0.6 mg/kg ketamine. The anaesthesia produced by this combination was rapidly and completely reversed by i.m. or i.v. injections of naltrexone at 30 times the A3080 dose (x = 0.60+/-0.25 mg/kg) and atipamezole at 3 times the medetomidine dose (x = 38+/-20 microg/kg). No residual effects from ketamine were noted following reversal of A3080 and medetomidine. No mortality was associated with this protocol.     

Cardiopulmonary effects of romifidine/ketamine or xylazine/ketamine when used for short duration anesthesia in the horse

The cardiovascular changes associated with anesthesia induced and maintained with romifidine/ketamine versus xylazine/ ketamine were compared using 6 horses in a cross over design. Anesthesia was induced and maintained with romifidine (100 microg/kg, IV)/ketamine (2.0 mg/kg, IV) and ketamine (0.1 mg/kg/min, IV), respectively, in horses assigned to the romifidine/ ketamine group. Horses assigned to the xylazine/ketamine group had anesthesia induced and maintained with xylazine (1.0 mg/kg, IV)/ketamine (2.0 mg/kg, IV) and a combination of xylazine (0.05 mg/kg/min, IV) and ketamine (0.1 mg/kg/min, IV), respectively. Cardiopulmonary variables were measured at intervals up to 40 min after induction. All horses showed effective sedation following intravenous romifidine or xylazine and achieved recumbency after ketamine administration. There were no significant differences between groups in heart rate, arterial oxygen partial pressures, arterial carbon dioxide partial pressures, cardiac index, stroke index, oxygen delivery, oxygen utilization, systemic vascular resistance, left ventricular work, or any of the measured systemic arterial blood pressures. Cardiac index and left ventricular work fell significantly from baseline while systemic vascular resistance increased from baseline in both groups. The oxygen utilization ratio was higher in the xylazine group at 5 and 15 min after induction. In conclusion, the combination of romifidine/ketamine results in similar cardiopulmonary alterations as a xylazine/ketamine regime, and is a suitable alternative for clinical anesthesia of the horse from a cardiopulmonary viewpoint.     

Comparative study of three intramuscular anaesthetic combinations (medetomidine/ketamine, medetomidine/fentanyl/midazolam and xylazine/ketamine) in rabbits

OBJECTIVE: To compare the quality of surgical anaesthesia and cardiorespiratory effects of three intramuscular (IM) anaesthetic combinations in rabbits. STUDY DESIGN: Prospective randomized cross-over experimental study. ANIMALS: Nineteen adult female chinchilla mixed-bred rabbits weighing 3.9 +/- 0.8 kg. METHODS: Rabbits were given one of three IM anaesthetic combinations: 0.25 mg kg(-1) medetomidine and 35.0 mg kg(-1) ketamine (M-K), 0.20 mg kg(-1) medetomidine and 0.02 mg kg(-1) fentanyl and 1.0 mg kg(-1) midazolam (M-F-Mz) and 4.0 mg kg(-1) xylazine and 50 mg kg(-1) ketamine (X-K). The effects of anaesthesia on nociceptive reflexes, circulatory and respiratory function were recorded. Statistical analyses involved repeated measures anova with paired Student's t-test applied post hoc. P-values <0.05 were considered as significant. RESULTS: Reflex loss was most rapid and complete in M-K recipients, whereas animals receiving M-F-Mz showed the longest tolerance of endotracheal intubation (78.1 +/- 36.5 minutes). Loss of righting reflex was significantly most rapid (p < 0.05) in the X-K group (114.7 +/- 24.0 minutes). Surgical anaesthesia was achieved in 16 of 19 animals receiving M-K, in 14 animals receiving M-F-Mz, and in seven animals with X-K, but only for a short period (7.1 +/- 11.6 minutes). This was significantly (p < 0.001) shorter than with M-K (38.7 +/- 30.0 minutes) and M-F-Mz (31.6 +/- 26.6 minutes). Heart rates were greatest in X-K recipients; lowest HR were seen in animals receiving M-F-Mz. Mean arterial blood pressure was significantly higher (about 88 mmHg) during the first hour in the M-K group. During recovery, the greatest hypotension was encountered in the X-K group; minimum values were 53 +/- 12 mmHg. Six of 19 animals in the M-F-Mz group showed a short period of apnoea (30 seconds) immediately after endotracheal intubation. Respiratory frequency was significantly lower in this group (p < 0.001). Highest values for arterial carbon dioxide partial pressures (PaCO(2)) (6.90 +/- 0.87 kPa; 52.5 +/- 6.5 mmHg) occurred after induction of anaesthesia in group M-F-Mz animals. There was a marked decrease in PaO(2) in all three groups (the minimum value 5.28 +/- 0.65 kPa [39.7 +/- 4.9 mmHg] was observed with M-K immediately after injection). Arterial PO(2) was between 26.0 and 43.0 kPa (196 and 324 mmHg) in all groups during O(2) delivery and decreased - but not <7.98 kPa - on its withdrawal. Immediately after drug injection, pH(a) values fell in all groups, with lowest values after 30 minutes (7.23 +/- 0.03 with M-K, 7.28 +/- 0.05 with M-F-Mz, and 7.36 +/- 0.04 with X-K). The X-K animals showed significantly (p < 0.001) higher pH values than medetomidine recipients. During 1 hour of anaesthesia pH values in the medetomidine groups remained below those of the X-K group. CONCLUSIONS: Surgical anaesthesia was induced in most animals receiving medetomidine-based combinations. Arterial blood pressure was maintained at baseline values for about 1 hour after M-K. Transient apnoea occurred with M-F-Mz and mandates respiratory function monitoring. Oxygen enrichment of inspired gases is necessary with all three combinations. Endotracheal intubation is essential in rabbits receiving M-F-Mz. CLINICAL RELEVANCE: The quality of surgical anaesthesia was greatest with M-K. All combinations allowed recoveries of similar duration. It is theoretically possible to antagonize each component of the M-F-Mz combination.     

Anaesthetic and cardiorespiratory effects of romifidine/ketamine combinations in cats

ObjectiveTo study the anaesthetic and cardiorespiratory effects of intramuscular (IM) administration of different combinations of romifidine and ketamine in cats.Study designProspective, randomized, cross-over experiment.AnimalsSeven healthy adult cats weighing (mean ± SD) 3.4 ± 0.7 kg and aged 4.6 ± 3.2 years.MethodsAnimals received romifidine 100 μg kg^?1 with ketamine 7.5 (R100/K7.5) and 10 mg kg^?1 (R100/K10), romifidine 200 μg kg^?1 with ketamine 5 (R200/K5), 7.5 (R200/K7.5) and 10 mg kg^?1 (R200/K10) by IM injection. The time required to perform orotracheal intubation (IT) was measured and the ease of intubation assessed. The onset of anaesthesia (OA), duration of anaesthesia (DA) and anaesthesia recovery times (AR) were measured. Analgesia and muscle relaxation scores were recorded every 5 minutes for 60 minutes after OA. Heart rate, systolic arterial pressure, arterial haemoglobin saturation, respiratory rate, end-tidal carbon dioxide and oesophageal temperature were also measured.ResultsThe IT, OA and DA were not significantly different between the treatments. The analgesia and muscle relaxation scores were similar between all treatments at most time points. The cardiorespiratory variables were not significantly different between the treatments in most cases. The adverse effects were dose dependent and similar to those previously described for other combinations of α₂-agonists and ketamine.Conclusions and clinical relevanceAnaesthesia produced by the studied combinations of romifidine and ketamine may only be reliable when conducting brief and noninvasive procedures in cats. The OA times were slower and the DA shorter than those reported for other alpha-2 agonists combined with ketamine. A dose-related increase in the intensity of the anaesthetic effects could not be demonstrated in this study.     

Anesthesia in the Richardson's ground squirrel: comparison of ketamine, ketamine and xylazine, droperidol and fentanyl, and sodium pentobarbital

A combination of ketamine and xylazine (88.9 mg of ketamine/ml and 11.1 mg of xylazine/ml) given IM (85.5 +/- 3.4 mg of ketamine/kg of body weight and 10.6 +/- 0.5 mg of xylazine/kg) or subcutaneously (85.6 +/- 4.0 mg of ketamine/kg and 10.7 +/- 0.7 mg of xylazine/kg) induced effective surgical anesthesia for 20 to 30 minutes in Richardson's ground squirrels. Use of ketamine alone (86 +/- 7 mg/kg, IM), a droperidol and fentanyl combination (2.6 +/- 0.4 mg of droperidol/kg and 52 +/- 8 micrograms of fentanyl/kg, IM), or sodium pentobarbital (50 +/- 2 mg/kg, intraperitoneally) did not induce surgical anesthesia, but did induce depressed respiratory rates in the squirrels.     

Effect of yohimbine on xylazine-ketamine anesthesia in cats

Xylazine and ketamine are an anesthetic combination used in feline practice for routine surgical procedures. In a controlled study, we evaluated the effects of yohimbine, an antagonist of xylazine, on the anesthesia induced by this anesthetic combination in cats. Two intramuscular doses of xylazine and ketamine (2.2 mg of xylazine/kg plus 6.6 mg of ketamine/kg and 4.4 mg of xylazine/kg plus 6.6 mg of ketamine/kg) caused approximately 60 and 100 minutes of anesthesia, respectively, in control cats. When yohimbine (0.1 mg/kg) was given intravenously 45 minutes after ketamine administration, the cats regained consciousness within 3 minutes. They were ambulatory 1 to 2 minutes after regaining consciousness. Yohimbine also reversed the bradycardia and respiratory depression elicited by xylazine-ketamine. The results indicated that yohimbine may be useful for controlling the duration of xylazine-ketamine anesthesia in cats.     

Clinical evaluation of three medetomidine--midazolam--ketamine combinations for neutering of ferrets (Mustela putorius furo)

33 ferrets (Mustela putorius furo, 11 females, 22 males, ASA I-II) were neutered in a combination anaesthesia with medetomidine, midazolam and ketamine. The animals were randomized into 3 groups. All animals received 20 microg/kg BW medetomidine and 0.5 mg/kg BW midazolam. The three groups differed regarding dosis and way of application of ketamine (IM10 = 10 mg/kg BW intramuscularly; IM07 = 7 mg/kg BW intramuscularly; SC10 = 10 mg/kg BW subcutaneously). After 30 minutes anaesthesia was partially antagonised with 100 microg/kg BW atipamezole i.m.. Sedation, muscle relaxation, analgesia, and overall anaesthetic impression were compared by a scoring protocol. Reactions to painful stimuli of clamping the spermatic cord or the ovarial ligament including the A. ovarica were judged, too. All animals lost their righting reflex and could be placed in dorsal recumbency. Induction and recovery time were significantly the shortest in study group IM10 with 1.73 +/- 0.3 and 9.73 +/- 4.6 min respectively. Recovery was significantly prolonged in group SC10 with 30.27 +/- 15.6 min. The MMK-anaesthesia with 10 mg/kg ketamine i.m. is very useful for neutering ferrets. Respiratory depression and bradycardia typically for medetomidine were seen in all three combinations, but quickly reversed after partial antagonisation. Induction and intubation, followed by inhalation anaesthesia, were possible with all three regimes.