Comparison of two thiopental infusion rates for the induction of anaesthesia in dogs.
To compare the induction dose requirements of thiopental using two different infusion rates for induction of anaesthesia in dogs.



Prospective, randomized study.



Fifty, healthy (ASA I or II) client-owned dogs with a mean age of 4.1 years and a mean mass of 20.4 kg undergoing elective surgery.



Animals were randomly assigned to receive an infusion of 2.5% thiopental at a rate of either 0.1 ml kg(-1) minute(-1) or 0.4 ml kg(-1)minute(-1), 30-40 minutes after pre-anaesthetic medication with intramuscular acepromazine (0.025 mg kg(-1)) and pethidine (3.5 mg kg(-1)). Thiopental administration was controlled by a precision syringe driver. Statistical analyses of the results, using the outcome 'mg kg(-1) required for induction' (log-transformed) included unpaired t-tests for all categorical data (thiopental infusion rate, breed, sex, obesity, sedation quality) and univariable linear regression for continuous variables (mass, age). All variables were then considered in a multivariable linear regression model. The quality of induction with the two different infusion rates was also assessed.



After controlling for quality of sedation, the thiopental induction dose requirement was significantly less (p < 0.001) with the slower infusion rate (median = 7.5 mg kg(-1); range 4.9-13.7) compared with the faster infusion rate (median =11.0 mg kg(-1); range 6.6-18.0). The quality of sedation also affected the dose required (p = 0.03). The slower infusion rate was associated with a significantly poorer induction quality (p = 0.03) [corrected]



Slow thiopental infusion (0.1 ml kg(-1) minute(-1)) for anaesthesia induction after acepromazine/pethidine pre-anaesthetic medication reduced the induction dose requirement, although the quality of induction was inferior.



The induction dose of thiopental was reduced with a slower administration rate and so slow administration is recommended in thiopental-sensitive animals.
Dugdale
Alexandra H A
AH
Department of Anaesthesia, University of Liverpool, Liverpool, UK. alexd@liv.ac.uk
Pinchbeck
Gina L
GL
Jones
Ronald S
RS
Adams
Wendy A
WA
D000758:Anesthesia / Q000379:methods / Q000662:veterinary*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000818:Animals; D004285:Dogs / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007262:Infusions, Intravenous / Q000662:veterinary; D016014:Linear Models; D008297:Male; D011446:Prospective Studies; D013874:Thiopental / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013997:Time Factors
D018686:Anesthetics, Intravenous; D013874:Thiopental