title: A comparison of two different ketamine and diazepam combinations with an alphaxalone and medetomidine combination for induction of anaesthesia in sheep.
abstract: OBJECTIVE
  To investigate the perceived adverse effects of a particular batch of ketamine during induction of anaesthesia in sheep and to assess if any adverse effects would make intubation more difficult for the veterinary students.
  
  
  METHODS
  Thirty adult sheep (mean bodyweight 74.5 (SD 9.4) kg) were randomly assigned to one of six groups of five sheep. Sheep in Groups A and B received I/V 0.5 mg/kg diazepam and 10 mg/kg ketamine (Ketamine Injection; Parnell Laboratories NZ Ltd, of the suspect batch); those in Groups C and D received I/V 0.5 mg/kg diazepam and 10 mg/kg ketamine (Ketalar; Hospira NZ Ltd.), and those in Groups E and F received I/V 2 μg/kg medetomidine and 2 mg/kg alphaxalone. In Groups A, C and E, intubation was by an experienced anaesthetist, and in Groups B, D and F intubation was by a veterinary student. Time from injection to successful intubation, the ease of intubation, saturation of haemoglobin with oxygen (SpO₂) and partial pressure of oxygen in arterial blood (PaO₂) were measured before the sheep were connected to an anaesthetic machine and allowed to breath oxygen. Times to extubation, holding its head up and standing, maximum and minimum heart rates, respiratory rates, maximal end tidal CO₂, and the quality of recovery were then recorded.
  
  
  RESULTS
  There were no measurable differences in outcomes between sheep in Groups A and B compared with C and D. Time to intubation was slightly shorter for the experienced anaesthetist than the student, but the difference was not significant. The sheep in Groups E and F took less time to recover than those in Groups A-D (p<0.05), but there were no significant differences between the groups in either the ease of induction or quality of recovery. Most sheep in Groups E and F showed minor excitatory effects, mainly at induction, which did not interfere with induction. Respiratory rates were lower in Groups E and F than Groups A-D (p<0.01), but SpO₂ was higher in Groups E and F than A and B (p<0.05).
  
  
  CONCLUSIONS
  The clinical impression that the batch of Parnell ketamine produced unexpected effects was shown to be incorrect. All the combinations produced anaesthesia that allowed intubation by the veterinary student.
  
  
  CONCLUSIONS
  All the drug combinations produced satisfactory anaesthesia in sheep, but the alphaxaloneand medetomidine combination resulted in faster recovery.
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors.forename: V P
authors.initials: VP
authors.lastname: Walsh
authors.forename: M
authors.initials: M
authors.lastname: Gieseg
authors.forename: P M
authors.initials: PM
authors.lastname: Singh
authors.forename: S L
authors.initials: SL
authors.lastname: Mitchinson
authors.forename: J P
authors.initials: JP
authors.lastname: Chambers
mesh_terms: D000762:Anesthesia Recovery Period; D000768:Anesthesia, General / Q000662:veterinary; D000778:Anesthetics, Dissociative / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology; D000818:Animals; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology*; D004359:Drug Therapy, Combination; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology; D007649:Ketamine / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D020926:Medetomidine / Q000008:administration & dosage / Q000494:pharmacology*; D011277:Pregnanediones / Q000008:administration & dosage / Q000494:pharmacology*; D012756:Sheep
chemical_list: D000778:Anesthetics, Dissociative; D006993:Hypnotics and Sedatives; D011277:Pregnanediones; D007649:Ketamine; C006477:alphaxalone; D020926:Medetomidine; D003975:Diazepam