The use of intraoperative fentanyl in spontaneously breathing dogs undergoing orthopaedic surgery

Nineteen dogs were assigned randomly to one of three groups. Animals in Group 1 were pre-medicated with acepromazine, 50 μg/kg bodyweight (bwt) intramuscularly (im) and received 10 ml of 0.9 per cent saline intravenously (iv) at the time of skin incision. Dogs in Group 2 were pre-medicated with acepromazine, 50 μg/kg bwt im, and received fentanyl 2 μg/kg bwt iv at skin incision. Dogs in Group 3 were pre-medicated with acepromazine, 50 μg/kg bwt and atropine, 30 to 40 μg/kg bwt, im and received fentanyl, 2 μg/kg bwt iv at skin incision. Pulse rate, mean arterial blood pressure, respiratory rate and end tidal carbon dioxide were measured before and after fentanyl or saline injection. Fentanyl caused a short-lived fall in arterial blood pressure that was significant in dogs premedicated with acepromazine, but not in dogs pre-medicated with acepromazine and atropine. A significant bradycardia was evident for 5 mins in both fentanyl treated groups. The effect on respiratory rate was most pronounced in Group 3, in which four of seven dogs required intermittent positive pressure ventilation (IPPV) for up to 14 mins. Two of six dogs in Group 2 required IPPV, whereas respiratory rate remained unaltered in the saline controls. The quality of anaesthesia was excellent in the fentanyl treated groups; however, caution is urged with the use of even low doses of fentanyl in spontaneously breathing dogs under halothane-nitrous oxide anaesthesia.     

Prolonging dissociative anaesthesia in horses with a repeated bolus injection

The effects of prolonging romifidine/ketamine anaesthesia in horses with a second injection of ketamine alone or both romifidine/ketamine compared with only induction injection of romifidine and tiletamine/zolazepam were studied in 6 horses anaesthetised in lateral recumbency on 3 random occasions. All horses were sedated with romifidine 0.1 mg/kg bwt iv and, on 2 occasions, anaesthesia was induced by iv injection of ketamine 2.2 mg/kg bwt. To prolong the ketamine-induced anaesthesia, either ketamine (I.1 mg/kg bwt iv) or ketamine and romifidine (I.1 mg/kg bwt and 0.04 mg/kg bwt iv, respectively) were given 18–20 min after the start of the ketamine injection for induction. On the third occasion, anaesthesia was induced by iv injection of 1.4 mg/kg bwt Zoletil (0.7 mg/kg bwt tiletamhe + 0.7 mg/kg bwt zolazepam). No statistically significant differences in the measured cardiorespiratory function were found between the 3 groups. Heart rate was decreased significantly after sedation but increased during anaesthesia. Arterial blood pressure increased after sedation and remained high during anaesthesia. A significant decrease in arterial oxygen tension was observed in all groups during anaesthesia. The muscle relaxation induced by romifidine was, in most cases, not sufficient to abolish the catalepsy following a repeated injection of ketamine alone. Zoletil or a repeated injection of ketaminehornifidine resulted in smoother anaesthesia. When additional time is required to complete surgery during field anaesthesia, it is advisable to prolong romifidine/ketamine anaesthesia with an injection of both romifidine and ketamine in healthy horses. When a longer procedure is anticipated from the start Zoletil is an alternative for induction of anaesthesia. The mean time to response to noxious stimuli and mean time spent in lateral recumbency was 28 and 38 min for the anaesthesia prolonged with ketamine, 3.5 and 43 rnin for the anaesthesia prolonged with ketaminehornifidine and 33 and 45 min for the anaesthesia with Zoletil. All horses reached a standing position at the first attempt.     

Total intravenous anaesthesia in the horse with propofol

The use of propofol, solubilised in a non-ionic emulsifying agent, for the induction and maintenance of anaesthesia in experimental ponies was assessed. Pilot studies revealed that premedication with xylazine (0.5 mg/kg bodyweight [bwt]) intravenously (iv) followed by propofol (2.0 mg/kg bwt) iv provided a satisfactory smooth induction. Two infusion rates (0.15 mg/kg bwt/min and 0.2 mg/kg bwt/min) were compared for maintenance of anaesthesia. An infusion rate of 0.2 mg/kg/min produced adequate anaesthesia in these ponies. Cardiovascular changes included a decrease in arterial pressure and cardiac output during maintenance. Respiratory depression was manifested by a decrease in rate and an increase in arterial carbon dioxide tension. Recovery after 1 h anaesthesia was rapid and smooth. In conclusion, induction and maintenance of anaesthesia with propofol in premedicated ponies proved a satisfactory technique.     

Propofol infusion anaesthesia in dogs pre-medicated with medetomidine

Ten laboratory beagles pre-medicated with medetomidine (40 μg/kg bodyweight [bwt]) were anaesthetised using a rapid injection of propofol, followed by propofol infusion. A loading dose of 4 mg/kg bwt of propofol was administered intravenously (iv) as a bolus and, immediately after, a 60 min iv propofol infusion (150 μg/kg bwt/min) was initiated. After a transient increase, mean arterial blood pressure decreased significantly below the pre-propofol level. However, the lowest values recorded (115 ± 11 mmHg) remained within the physiological limits. Heart rate increased significantly (from 41 ± 7.3 to 58 ± 11 beats/min) after initiation of the propofol infusion. No significant changes were seen in respiratory frequency; pO₂ decreased transiently; minimum values (10 ± 2.3 kPa) recorded 5 mins after initiation of the propofol infusion differed significantly from the starting level. pCO₂ increased significantly and the highest values recorded were 6.1 ± 0.35 kPa. Accordingly, pH decreased reaching the lowest level (pH 7.29) 15 mins after initiation of the propofol infusion. The analgesic effect of the present combination was not studied, but the absence of the palpebral and pedal reflexes suggested a surgical stage of anaesthesia. Therefore, propofol infusion in beagles pre-medicated with medetomidine proved to be a promising anaesthetic regimen but, if used clinically, oxygen-enriched inspired air should be used.     

Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects

REASONS FOR PERFORMING STUDY: To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia. OBJECTIVES: To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies. METHODS: Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals. RESULTS: Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts. CONCLUSIONS: In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa. POTENTIAL RELEVANCE: The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.     

Preliminary study on the pharmacokinetics of phenobarbital in the neonatal foal

Pharmacokinetic characteristics of the anticonvulsant phenobarbital were studied in seven pony and two Thoroughbred foals aged between four and 10 days. A single, 20 mg/kg bodyweight (bwt) dose of phenobarbital was given intravenously over 25 mins and the serum concentrations of the drug were measured using an EMIT AED assay (coefficient of variation 1.37 per cent at 30 micrograms/ml, n = 7). Phenobarbital elimination was found to follow first order kinetics. The mean (+/- sd) peak phenobarbital serum concentration was 18.6 +/- 2.1 micrograms/ml at 1 h after initiation of infusion with a mean (+/- se) half-life of 12.8 +/- 2.1 h. The mean (+/- se) volume of distribution was 0.86 +/- 0.026 litres/kg bwt and mean (+/- se) total body clearance was 0.0564 +/- 0.0065 litres/kg bwt/h. Sedation was noticed 15 to 20 mins after the beginning of infusion and lasted for up to 8 h. All foals could be aroused and could walk although they were ataxic for the first 1 to 2 h. A degree of delayed hyperexcitability occurred 3 to 8 h after infusion. In equine neonatal seizure disorders it is recommended to use a loading dose of 20 mg/kg bwt of phenobarbital, followed by maintenance doses of 9 mg/kg bwt at 8 h. With this regimen, average steady state serum phenobarbital concentrations should range between approximately 11.6 and 53 micrograms/ml. Phenobarbital serum concentrations should be monitored following the loading dose and 24 h after initiating the maintenance doses to check that levels remain within the suggested (human) therapeutic range of 15 to 40 micrograms/ml.     

Clinical comparison of preanaesthetic intramuscular medetomidine and dexmedetomidine in domestic sheep.

Medetomidine and its active d-enantiomer, dexmedetomidine, are highly selective alpha-2 agonists with potent sedative, anaesthetic-sparing and analgesic effects. These properties make them an ideal pre-anaesthetic medication for noxious surgical procedures. However, sheep can develop adverse hypoxaemic effects after intravenous alpha-2 agonists. Objective of the present study was to compare intramuscular injection of medetomidine or dexmedetomidine at equipotent doses as preanaesthetic medication prior to isoflurane anaesthesia in sheep. Nineteen healthy, adult, non-pregnant, female sheep of various breeds were used. The study was carried out as a randomised, blind trial. Group A received 15 micrograms/kg bwt dexmedetomidine and group B received 30 micrograms/kg bwt medetomidine intramuscularly (i.m.) 30 minutes prior to induction of anaesthesia. Anaesthesia was induced with ketamine (2.0 mg/kg bwt i.v.) and maintained with isoflurane in 100% oxygen. End expired anaesthetic concentration (FEiso), respiratory frequency (fR), direct arterial blood pressures and heart rates (HR) were measured. Arterial blood samples were taken at intervals. Data were averaged over time (sum of measurements/number of measurements) and tested for differences between groups by independent t-tests, and ANOVA for repeated measures followed by Bonferroni corrected t-tests. There were no differences in demographic data between the groups. Duration of anaesthesia [A: 170 (42) minutes, B: 144 (33) minutes] and duration of surgery [A: 92 (32) minutes, B: 85 (31) minutes] were similar in both groups. Average FEiso concentrations required to maintain a surgical plane of anaesthesia were not significantly different between groups [A: 0.82 (0.14)%; B: 1.00 (0.25)%]. Mean average fR, did not differ between groups [A: 31 (14), B: 37 (15)]. Heart rates were significantly lower in group B over the course of the anaesthesia. Mean arterial blood pressures (MAP) were not significantly different between the groups. The PaO2 was less variable in group A than in group B. Individual minimum values were 19.1 kPa and 7.9 kPa in group A and B, respectively. There were no significant differences in PaCO2 and paH between the groups and over time. In conclusion, intramuscular application of dexmedetomidine at 15 micrograms/kg bwt and medetomidine at 30 micrograms/kg bwt prior to isoflurane anaesthesia induced similar changes in clinically monitored cardiorespiratory parameters. The observed differences (heart rates, PaO2) between dexmedetomidine and medetomidine at the chosen dose relationship can be considered clinically not significant. At the chosen dose rates individual animals responded with a transient drop in blood oxygenation, therefore careful monitoring is required. In addition, in compromised sheep medetomidine and dexmedetomidine should be used carefully.     

Changes in heart rate, mean arterial pressure, blood biochemistry, plasma glucose, plasma lactate and some plasma enzymes during sufentanil/halothane anaesthesia in horses

Nine horses were each anaesthetised for 40 min using SufentaniVhalothane. No surgery was performed. After premedication (detomidine 5 pgkg bwt iv) induction of anaesthesia was achieved by a combination of guaiphenesinlthiopentone. Anaesthesia was maintained by inhalation of halothane (0.8%) in oxygen. Six horses (Group 1) received 1 pgkg bwt sufentanil followed by a second injection (1 pg/kg bwt) after 20 min. Three horses (Group 2) received 2 pg/kg bwt sufentanil also followed by a second injection (2 pg/kg bwt) after 20 min. Each sufentanil injection produced a slight decrease in mean arterial blood pressure with a gradual return to the initial pressure. Bradycardia was also observed. Sufentanil injection induced apnoea needing artificial ventilation. Arterial blood was sampled for analysis during the anaesthetic procedure. At the end of anaesthesia, 1 h and 24 h after rising, venous blood was sampled to determine concentrations of lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and creatine phosphokinase (CPK). Values obtained were compared with values in blood taken before premedication. Plasma glucose and lactate concentrations just before sufentanil administration, at the end of anaesthesia and 1 h after rising were compared to control values. Plasma glucose concentration increased significantly during anaesthesia but returned to normal values 1 h after rising. All other parameters stayed within physiological ranges. In both groups spontaneous respiration returned 20–25 min after the second sufentanil injection. Recovery was uneventful.     

Effect of a constant rate infusion of lidocaine on the quality of recovery from sevoflurane or isoflurane general anaesthesia in horses

REASONS FOR PERFORMING STUDY: Lidocaine constant rate infusions (CRIs) are common as an intraoperative adjunct to general anaesthesia, but their influence on quality of recovery has not been thoroughly determined. OBJECTIVES: To determine the effects of an intraoperative i.v. CRI of lidocaine on the quality of recovery from isoflurane or sevoflurane anaesthesia in horses undergoing various surgical procedures, using a modified recovery score system. HYPOTHESIS: The administration of intraoperative lidocaine CRI decreases the quality of recovery in horses. METHODS: Lidocaine (2 mg/kg bwt bolus followed by 50 microg/kg bwt/min) or saline was administered for the duration of surgery or until 30 mins before the end of surgery under isoflurane (n = 27) and sevoflurane (n = 27). RESULTS: Horses receiving lidocaine until the end of surgery had a significantly higher degree of ataxia and a tendency towards significance for a lower quality of recovery. There was no correlation between lidocaine plasma concentrations at recovery and the quality of recovery. CONCLUSIONS: Intraoperative CRI of lidocaine affects the degree of ataxia and may decrease the quality of recovery. POTENTIAL RELEVANCE: Discontinuing lidocaine CRI 30 mins before the end of surgery is recommended to reduce ataxia during the recovery period.     

Sedative and cardiovascular effects of romifidine, alone and in combination with butorphanol, in the horse

The behavioural and sedative effects of intravenous (iv) romifidine (40 and 80 μg/kg bodyweight [bwt]) alone or in combination with iv butorphanol (50 μg/kg bwt) were investigated in four ponies and one Thoroughbred horse. Apparent sedation, as judged by the lowering of the head, and by the response to imposed touch, visual and sound stimuli was assessed. The combination with butorphanol reduced the animals' response to imposed stimuli when compared with the effect of the same dose of romifidine alone. Following the administration of romifidine/butorphanol combinations muzzle tremor was noted and some animals attempted to walk forward. In a separate series, the cardiopulmonary effects of iv romifidine (80 μg/kg bwt) alone, or in combination with butorphanol (50 μg/kg bwt) were investigated. Romifidine and the romifidine/butorphanol combination caused similar cardiovascular changes, these being bradycardia with heart block, and hypertension followed by hypotension. Romifidine caused a transient decrease in arterial oxygen tensions and arterial carbon dioxide tensions had increased significantly by the end of the 90 min recording period. Romifidine/butorphanol combinations produced significantly higher arterial carbon dioxide tensions during the first 15 mins after drug administration than did romifidine alone. Butorphanol at 50 μg/kg bwt iv reduced the response to imposed stimuli in horses sedated with romifidine. The combination produced no cardiovascular changes beyond those induced by romifidine alone, but did increase the degree of respiratory depression.     

Atropine reduces dobutamine-induced side effects in ponies undergoing a pharmacological stress protocol

REASONS FOR PERFORMING STUDY: High-dose dobutamine stress echocardiography has been shown to be cardiotoxic and arrhythmogenic in horses. However, the test may have benefit in practice as a pharmacological challenge of exercise without the treadmill being required. OBJECTIVES: To investigate the effect of low-dose dobutamine on cardiac performance in ponies previously treated with atropine, in order to develop a pharmacological protocol that allows examination of the equine heart under stimulation. METHODS: In 13 healthy Shetland ponies, heart rate (HR), stroke index (SI) and cardiac index (CI) were calculated from pulsed-wave Doppler ultrasound measurements performed at rest and during incremental steps of dobutamine infusion. Group 1 (n = 7) received dobutamine infusion at 2 microg/kg bwt/min for 5 mins followed by incremental rates of 5 microg/kg bwt/min every 5 mins, from 5 to 40 microg/kg bwt/min. Group 2 (n = 6) received dobutamine infusion in incremental rates of 1 microg/kg bwt/min, every 5 mins, from 2 microg/kg bwt/min to 5 microg/kg bwt/min, after premedication with 2 injections of 25 microg/kg bwt of atropine 5 mins apart. RESULTS: The increase in CI during the pharmacological challenge was higher in Group 2 and reached about 2.5 times the resting value. This increase in CI was mediated by a significant increase in HR in both groups, while SI significantly decreased in Group 1 and did not change significantly in Group 2. Ponies of Group 1, but not those of Group 2, showed excessive restlessness and cardiac arrhythmias during the pharmacological challenge and a high intragroup variability in cardiac response. CONCLUSIONS: The results of this study suggest that a low dose of dobutamine in ponies previously given atropine could be a helpful pharmacological protocol to perform stress echocardiography in equids. POTENTIAL RELEVANCE: Further studies should evaluate left ventricular wall motion in horses undergoing low-dose dobutamine protocol after pretreatment with atropine.     

Physiological stimuli of thirst and drinking patterns in ponies

The stimuli that elicit thirst were studied in four ponies. Nineteen hours of water deprivation produced an increase in plasma protein from 67 +/- 0.1 g/litre to 72 +/- 2 g/litre, a mean (+/- se) increase in plasma sodium from 139 +/- 3 to 145 +/- 2 mmol/litre and an increase in plasma osmolality from 297 +/- 1 to 306 +/- 2 mosmol/litre. Undeprived ponies drank 1.5 +/- 0.9 kg/30 mins; 19 h deprived ponies drank 10.2 +/- 2.5 kg/30 mins and corrected the deficits in plasma protein, plasma sodium and plasma osmolality as well as compensating for the water they would have drunk during the deprivation period. In order to determine if an increase in plasma osmolality would stimulate thirst, 250 ml of 15 per cent sodium chloride was infused intravenously. The ponies drank when osmolality increased 3 per cent and when plasma sodium rose from 136 +/- 3 mmol/litre to 143 +/- 3 mmol/litre. Ponies infused with 15 per cent sodium chloride drank 2.9 +/- 0.7 kg; those infused with 0.9 per cent sodium chloride drank 0.7 +/- 0.5 kg. In order to determine if a decrease in plasma volume would stimulate thirst, ponies were injected with 1 or 2 mg/kg bodyweight (bwt) frusemide. Plasma protein rose from 68 +/- 2 g/litre pre-injection to 75 +/- 2 g/litre 1 h after 1 mg/kg bwt frusemide and to 81 +/- 1 g/litre 1 h after 2 mg/kg bwt frusemide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gentamicin dosage in foals aged one month and three months

The absorption and disposition kinetics of gentamicin were compared at two dosage levels (2 and 4 mg/kg bodyweight [bwt]) in one- and three-month-old foals. Following intramuscular (im) injection of single 2 mg/kg bwt doses, the drug was absorbed rapidly and produced peak serum concentration (18.2 mu 5.3 +/- g/ml, n = 8) at 30 mins. Much wider variations were associated with the amount of drug absorbed and the serum gentamicin concentrations after administration at the higher dosage level. The half-life of gentamicin was similar in the one-month-old (3.7 +/- 1.7 h, n = 8) and three-month-old (3.3 +/- 0.8 h, n = 8) foals, and was independent of the dose. One-month-old foals did not appear to have a deficiency in renal excretion of gentamicin. The minimum inhibitory concentration of gentamicin for Corynebacterium equi and certain other equine bacterial isolates was less than 0.195 microgram/ml. It was concluded that 2 mg/kg bwt administered by im injection at 8 to 12 h intervals, depending on the severity of the infection, could be recommended as the dose rate for treatment of systemic infections caused by microorganisms that are susceptible to gentamicin.     

Medetomidine/ketamine sedation in calves and its reversal with atipamezole

Atipamezole was used to reverse the sedation induced in calves by medetomidine/ketamine. Thirteen claves subjected to umbilical surgery received medetomidine 20 μg/kg bodyweight (bwt) and ketamine 0.5 mg/kg bwt intravenously (iv) from a mixture of the drugs in one syringe. Atipamezole was given at doses of 20 to 60 μg/kg iv and intramuscularly (im) to the calves at the end of the operation. Following the administration of medetomidine and ketamine, PaCO₂ increased whereas pH, PaO₂ and heart rate decreased. Reversing the effects of medetomidine with atipamezole did not cause undesirable effects; recovery was rapid and smooth, most of the animals reached a standing position within 1 to 3 mins after the atipamezole injection.     

Interactions between chloramphenicol, acepromazine, phenylbutazone, rifampin and thiamylal in the horse

The potential for interactions between chloramphenicol, phenylbutazone, acepromazine and thiamylal and chloramphenicol, rifampin, and phenylbutazone were evaluated in two groups of experiments. In the first, five horses were given thiamylal intravenously (iv) (6.6 mg/kg) after pretreatment with acepromazine, and the time of recumbency was determined. Administration of chloramphenicol iv (25 mg/kg) 1 h prior to anaesthesia significantly lengthened the recumbency time from 21.8 +/- 4.8 mins to 36.0 +/- 8.3 mins. There was an apparent but not statistically significant decrease in recumbency time when phenylbutazone (4.4 mg/kg) was administered iv daily for 4 days prior to anaesthesia. In the second series of experiments, phenylbutazone (4.4 mg/kg), chloramphenicol (25 mg/kg) and rifampin (10 mg/kg) were administered in various sequences to five different horses. Chloramphenicol pretreatment produced a significant decrease in the elimination rate and rifampin a significant increase in the elimination rate of phenylbutazone. The half-life of elimination of phenylbutazone alone was about 4 h. Following four days pretreatment with rifampin it was approximately 2.7 h, it was approximately 5.6 h and 9.5 h, respectively, when chloramphenicol was administered in one dose 1 h before or two doses 12 h and 1 h before phenylbutazone.     

Anaesthetic and cardiorespiratory effects of propofol at 10% for induction and 1% for maintenance of anaesthesia in horses

Reasons for performing study: Studies have demonstrated the clinical usefulness of propofol for anaesthesia in horses but the use of a concentrated solution requires further investigation. Objectives: To determine the anaesthetic and cardiorespiratory responses to a bolus injection of 10% propofol solution in mature horses. Methods: Three randomised crossover experimental trials were completed. Trial 1: 6 horses were selected randomly to receive 10% propofol (2, 4 or 8 mg/kg bwt i.v.). Trial 2: 6 horses received 1.1 mg/kg bwt i.v. xylazine before being assigned at random to receive one of 5 different doses (1–5 mg/kg bwt) of 10% propofol. Trial 3: 6 horses were sedated with xylazine (0.5 mg/kg bwt, i.v.) and assigned randomly to receive 10% propofol (3, 4 or 5 mg/kg bwt, i.v.); anaesthesia was maintained for 60 min using an infusion of 1% propofol (0.2‐0.4 mg/kg bwt/min). Cardiorespiratory data, the quality of anaesthesia, and times for induction, maintenance and recovery from anaesthesia and the number of attempts to stand were recorded. Results: Trial 1 was terminated after 2 horses had received each dose of 10% propofol. The quality of induction, anaesthesia and recovery from anaesthesia was judged to be unsatisfactory. Trial 2: 3 horses administered 1 mg/kg bwt and one administered 2 mg/kg bwt were not considered to be anaesthetised. Horses administered 3–5 mg/kg bwt i.v. propofol were anaesthetised for periods ranging from approximately 10–25 min. The PaO₂ was significantly decreased in horses administered 3–5 mg/kg bwt i.v. propofol. Trial 3: The quality of induction and recovery from anaesthesia were judged to be acceptable in all horses. Heart rate and rhythm, and arterial blood pressure were unchanged or decreased slightly during propofol infusion period. Conclusions: Anaesthesia can be induced with a 10% propofol solution and maintained with a 1% propofol solution in horses administered xylazine as preanaesthetic medication. Hypoventilation and hypoxaemia may occur following administration to mature horses. Potential relevance: Adequate preanaesthetic sedation and oxygen supplementation are required in horses anaesthetised with propofol.     

The cardiorespiratory effects of morphine and butorphanol in horses anaesthetised under clinical conditions

Twenty-five horses admitted for minor orthopaedic or soft tissue surgery were anaesthetised with detomidine, ketamine and halothane. Heart rate, arterial blood pressure, respiratory rate, tidal volume, minute volume, blood gases and occlusion pressures were measured before and for 30 mins after intravenous (iv) injection of saline, butorphanol 0.05 mg/kg bodyweight (bwt) or morphine 0.02 or 0.05 mg/kg bwt. Drug or saline treatment induced no significant changes from pre-treatment values within a group for arterial blood pressure, heart rate, respiratory rate, arterial carbon dioxide tension, arterial oxygen tension and occlusion pressure. In conclusion, both morphine and butorphanol at the stated doses cause no adverse effects on the cardiovascular and respiratory systems of anaesthetised horses.     

The effect of guaiphenesin on romifidine/ketamine anaesthesia in ponies

The purpose of this study was to investigate the effect of a single dose (50 mg/kg) of guaiphenesin on recumbency time, surgical conditions and the ‘quality’ of anaesthesia in ponies anaesthetised for castration. Sixteen ponies were sedated with romifidine 100 μg/kg and anaesthetised with ketamine (2.2 mg/kg). Ponies allocated to Group A received no treatment and those in Group B were given 50 mg/kg of a 15% guaiphenesin solution. Guaiphenesin was given as a rapid iv injection immediately after induction of anaesthesia. All ponies were subsequently castrated. The mean (± se) time of recumbency in Group A was 20.9 ± 1.37 min and in Group B 27.2 ± 2.1 min to (P<0.05). Subjective assessment scores for the quality of surgical conditions and anaesthesia itself were significantly greater (indicating better conditions) in ponies receiving guaiphenesin, although there was no difference between groups in the quality of recovery.     

Xylazine, diazepam and midazolam premedicated ketamine anaesthesia in white Leghorn cockerels for typhlectomy

Thee different combinations of ketamine hydrochloride were used to induce general anaesthesia for surgical operations (typhlectomy) in 30 adult, single-comb White Leghorn cockerels. They were randomly divided into three groups, each comprising 10 birds. Birds in Group I received xylazine-ketamine combinations at the dose rate of 2 mg xylazine and 10 mg ketamine per kg i.v., whereas birds of Group II received diazepam (2.5 mg/kg i.v.) and 5 min later ketamine (75 mg/kg i.m.). In the Group III, midazolam (2 mg/kg i.m.) and 5 min later ketamine (50 mg/kg i.v.) was administered. The onset of sedation/anaesthesia was shortest (1.60 +/- 0.27 min) in Group I, followed by Group II (8.40 +/- 0.83 min) and Group III (17.10 +/- 1.71 min). Recovery period was shortest in the Group I (65-75 min) followed by Group II (80-85 min) and Group III (92-105 min). Sedation, muscle relaxation and surgical anaesthesia was optimal and excellent in Group I compared with the other two groups. Torticollis, salivation and dyspnoea were observed in Group III. Short-term limb contractions were present in all birds in Groups II and III, up to 20 min of observation. Recovery from anaesthesia was smooth in all three groups. A Surgical procedure (typhlectomy) was performed on all birds. Hypothermia was observed in Group II, whereas heart and respiratory depression was recorded in Group I. Blood sugar level did not vary significantly in any anaesthetic regime. The reduction of haemoglobin was maximum in Group II compared with Groups I and III. Hypoxaemia and hypercapnaea were elevated in all birds in Groups II and III. Blood electrolytes did not vary significantly from the baseline values among the three groups of birds during the period of observation (120 min). The xylazineketamine combination was found to be the best anaesthesia for surgical intervention in chickens.     

An investigation into the use of propofol (Rapinovet®) in long-tailed macaques (Macaca fascicularis)

Propofol, an intravenous (iv) anaesthetic agent, was given to 12 long-tailed macaque monkeys (Macaca fascicularis) that were initially chemically restrained using ketamine hydrochloride. Anaesthesia was induced and maintained using incremental iv injections of propofol at various dose rates. Physiological parameters were monitored during anaesthesia. Five animals were allowed to recover from anaesthesia and their recovery was usually uneventful. At the dose levels investigated there was good muscle relaxation and analgesia and cardiovascular and respiratory functions were adequately maintained. A dose of 10 mg/kg bodyweight gave moderate surgical anaesthesia for between 20 and 40 mins.