Comparison of isoflurane and sevoflurane for short-term anesthesia in piglets.

Objectives: To compare isoflurane (ISO) and sevoflurane (SEVO) short-term anesthesia in piglets during castration.

Study Design: Prospective, randomized study.

Animals: A total of 114 male piglets aged 6-10 days, body weight 1.3-5.0 kg.

Methods: Piglets were randomly selected from multiple litters and randomly assigned to being anesthetized with ISO or SEVO prior to castration. To calculate appropriate doses for induction and maintenance of anesthesia, a square root of time model was used, with calculations based on metabolic size and attainment of 1.3x minimum alveolar concentration. The equipotent target alveolar concentration of ISO was 1.82% and for SEVO 4.03%. After doses were calculated, a table listing piglet weights and agent requirements was produced. Anesthetics were delivered via liquid anesthetic injection into a previously developed rebreathing inhaler that was filled with oxygen prior to use. Piglets were anesthetized, castrated and allowed to recover prior to return to the sow. Times for induction, recovery and total time to standing were recorded, and end-tidal carbon dioxide (Pe'CO2) tensions were measured by capnography immediately after mask removal. Each response variable was analyzed in sas using the Proc Mixed procedure, with piglet weight and days of age as covariates. Castration problems and mortality were assessed relative to unanesthetized littermates.

Results: There were no statistically significant differences in age, weight or total anesthetic time between the anesthetics. Induction time was shorter, recovery time longer, and Pe'CO2 lower with ISO. No morbidity or mortality was associated with either group.

Conclusion And Clinical Relevance: Isoflurane and SEVO, delivered in a novel inhaler, provided economical, safe, rapid anesthetic induction and maintenance. Optimal conditions were provided for castration and recoveries were brief and smooth. Statistically significant differences in times would be of minor clinical importance. The cost of anesthesia was much less with ISO than with SEVO.