Determination of the minimum infusion rate of alfaxalone during its co-administration with midazolam in goats.

INTRODUCTION: The minimum infusion rate (MIR) of alfaxalone when co-administered with midazolam in goats was evaluated. MATERIALS AND METHODS: Eight goats (four does and four wethers) were anaesthetised, on separate occasions, with alfaxalone at an initial dose of 9.6 mg/kg/hour combined with one of three midazolam treatments: a bolus of 0.1 mg/kg followed by constant rate infusion (CRI) of 0.1 mg/kg/hour (treatment LMID), 0.3 mg/kg followed by CRI of 0.3 mg/kg/hour (MMID), 0.9 mg/kg followed by CRI of 0.9 mg/kg/hour (HMID), intravenously. Responses to stimulation (clamping on the proximal part of one digit of the hoof with Vulsellum forceps for 60 seconds) were tested every 30 minutes. In the absence or presence of a response to stimulation, the infusion rate was reduced or increased by 1.9 mg/kg/hour. Alfaxalone MIR was calculated as the mean of the infusion rates that allowed and abolished movement. Cardiopulmonary parameters were measured. RESULTS: Alfaxalone MIR was 6.7 (6.7-8.6) mg/kg/hour, 6.7 (4.8-6.7) mg/kg/hour and 2.9 (1.0-4.8) mg/kg/hour for LMID, MMID and HMID respectively. Cardiopulmonary function was minimally affected, with hypoxaemia observed two minutes into anaesthesia during all treatments. Recovery from anaesthesia was excitement-free. CONCLUSIONS: Midazolam causes a dose-dependent reduction of alfaxalone MIR in goats. Oxygen supplementation is recommended during anaesthesia with alfaxalone and midazolam in goats.

Effects of fentanyl on isoflurane minimum alveolar concentration and cardiovascular function in mechanically ventilated goats.

The effects of fentanyl on the minimum alveolar concentration (MAC) of isoflurane and cardiovascular function in mechanically ventilated goats were evaluated using six healthy goats (three does and three wethers). Following induction of general anaesthesia with isoflurane delivered via a mask, endotracheal intubation was performed and anaesthesia was maintained with isoflurane. The baseline MAC of isoflurane (that is, the lowest alveolar concentration required to prevent gross purposeful movement) in response to clamping a claw with a vulsellum forceps was determined. Immediately after baseline isoflurane MAC determination, the goats received, on separate occasions, one of three fentanyl treatments, administered intravenously: a bolus of 0.005 mg/kg followed by constant rate infusion (CRI) of 0.005 mg/kg/hour (treatment LFENT), a bolus of 0.015 mg/kg followed by CRI of 0.015 mg/kg/hour (treatment MFENT) or a bolus of 0.03 mg/kg followed by CRI of 0.03 mg/kg/hour (treatment HFENT). Isoflurane MAC was redetermined during the fentanyl CRI treatments. Cardiopulmonary parameters were monitored. A four-week washout period was allowed between treatments. The observed baseline isoflurane MAC was 1.32 (1.29 to 1.36) per cent. Isoflurane MAC decreased to 0.98 (0.92 to 1.01) per cent, 0.75 (0.69 to 0.79) per cent and 0.58 (0.51 to 0.65) per cent following LFENT, MFENT and HFENT respectively. Cardiovascular function was not adversely affected. The quality of recovery from general anaesthesia was good, although exaggerated tail-wagging was observed in some goats following MFENT and HFENT.

Sedative and cardiopulmonary effects of acepromazine, midazolam, butorphanol, acepromazine-butorphanol and midazolam-butorphanol on propofol anaesthesia in goats.

UNLABELLED: The sedative, propofol-sparing and cardiopulmonary effects of acepromazine, midazolam, butorphanol and combinations of butorphanol with acepromazine or midazolam in goats were evaluated. Six healthy Boer - Indigenous African crossbreed goats were by randomised cross-over designated to 6 groups: Group SAL that received saline, Group ACE that received acepromazine, Group MID that received midazolam, Group BUT that received butorphanol, Group ACEBUT that received acepromazine and butorphanol and Group MIDBUT that received midazolam and butorphanol as premedication agents intramuscularly on different occasions at least 3 weeks apart. The degree of sedation was assessed 20 minutes after administration of the premedication agents. Thirty minutes after premedication, the dose of propofol required for induction of anaesthesia adequate to allow placement of an endotracheal tube was determined. Cardiovascular, respiratory and arterial blood-gas parameters were assessed up to 30 minutes after induction of general anaesthesia. Acepromazine and midazolam produced significant sedation when administered alone, but premedication regimens incorporating butorphanol produced inconsistent results. The dose of propofol required for induction of anaesthesia was significantly reduced in goats that received midazolam alone, or midazolam combined with either acepromazine or butorphanol. The quality of induction of anaesthesia was good in all groups, including the control group. Cardiovascular, respiratory and blood-gas parameters were within normal limits in all groups and not significantly different between or within all groups. IN CONCLUSION: sedation with midazolam alone, or midazolam combined with either acepromazine or butorphanol significantly reduces the induction dose of propofol with minimal cardiopulmonary effects in goats.

Limb fracture during recovery from general anaesthesia: an often tragic complication of equine anaesthesia.

A 10-year-old Thoroughbred mare was presented for lameness of the left hindlimb as a result of an apical fracture of the lateral proximal sesamoid bone. The mare was ultimately euthanased after suffering catastrophic fractures of the 3rd and 4th metatarsal bones of the contra-lateral hindlimb during an uncoordinated attempt to rise during recovery from general anaesthesia after undergoing arthroscopic surgery. The case report focuses mostly on horse anaesthesia-related mortality, anaesthetic procedure in the horse, possible causes of fractures in horses during recovery and ways in which rate of occurrence of these fractures can be minimised.

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.

Comparison of morphine and carprofen administered alone or in combination for analgesia in dogs undergoing ovariohysterectomy.

In this study the analgesic efficacy of the pure agonistic opioid morphine and the cyclo-oxygenase type-2-selective carprofen were compared since there is no previous specific comparative study for these two common analgesics. Forty-five bitches undergoing elective ovariohysterectomy were randomly assigned to one of three groups; receiving morphine 0.4 mg/kg bodyweight pre-operatively and 0.2 mg/kg every 4-6 hours thereafter (Morphine group), receiving a once-off carprofen 4 mg/kg injection (Carprofen group) or receiving both morphine and carprofen (MorphCarp group). The dogs were premedicated with acepromazine 0.01 mg/kg and induced with either thiopentone 5-10 mg/kg or propofol 4-6 mg/kg. General anaesthesia was maintained with halothane in oxygen. The degree of pain was assessed over a 24-hour period under blinded conditions using a pain scale modified from the University of Melbourne pain scale and the Glasgow composite pain tool. Physiological parameters such as respiratory rate, pulse rate and body temperature were also assessed over the same time period. There was no significant difference in pain-scores and thus analgesia offered by the three analgesia protocols at any assessment point across the three groups, but there were differences within groups across time points. Baseline total pain-scores were lower than scores at all post-operative points within all three groups. Both morphine and carprofen provided good analgesia without any obvious adverse effects. This study indicates that at the dosages indicated above, carprofen administered on its own produces analgesia equal to that produced by morphine and that the two drugs administered together do not produce better analgesia than either drug administered on its own.

Effects of intravenous lidocaine on isoflurane concentration, physiological parameters, metabolic parameters and stress-related hormones in horses undergoing surgery.

Physiological parameters, metabolic parameters and stress-related hormones are evaluated in horses anaesthetized with isoflurane in oxygen combined with lidocaine intravenously. Two groups of horses anaesthetized with isoflurane (six horses in each group) were studied: a lidocaine group (IL), which received intravenous lidocaine and a control group (C), which received intravenous saline. Horses in both groups were premedicated with detomidine (i.v.), and anaesthesia was induced with midazolam-ketamine (i.v.). The lidocaine group received intravenous lidocaine as a loading dose of 2.5 mg kg(-1) at 15 min after induction of anaesthesia directly followed by a maintenance dosage of 50 microg kg(-1) min(-1), while the control group received saline (i.v.) following the same regime. End-tidal isoflurane and standard physiological parameters were measured. Blood was sampled for measurement of lidocaine, stress hormones and metabolic parameters. The end-tidal isoflurane concentration in the lidocaine group was 0.96 +/- 0.06% versus 1.28 +/- 0.06% (mean +/- SD) in the control group, a significant (P < 0.05) reduction of 25%. No significant differences were found regarding stress-related hormones, metabolic and physiological parameters. This study suggests that the use of lidocaine to decrease the concentration of isoflurane to obtain a sufficient surgical anaesthesia has no subsequent effects on physiological and metabolic parameters or stress-related hormones.