Induction and Recovery Characteristics of Isoflurane and Sevoflurane Anaesthesia for Ovariohysterectomy in Dogs

Abstract

A study was carried out to evaluate induction and recovery characteristics of isoflurane and sevoflurane inhalant anaesthesia for ovariohysterectomy in young and healthy female dogs. All the animals were premedicated with Atropine sulphate and Diazepam. Induction of anaesthesia was achieved by using Isoflurane (5%) in group A and Sevoflurane (5%) in group B along with oxygen (1.5L/min) using close fitting face mask with rubber diaphragm. Anaesthesia was maintained in group A and B by using Isoflurane and Sevoflurane respectively by endotracheal intubation till effect using small animal anaesthesia machines of rebreathing or circle system with vaporizer outside the circuit. Quantitative parameters like average induction time, average dose volume of maintenance and average time of reappearance of various reflexes during recovery were recorded. Quality of induction was compared by assessing subjective parameters like degree of various reflexes and scored accordingly during surgical plane. Also qualitative parameters during recovery phase were assessed based on video recordings obtained during the recovery phase and were scored using simple descriptive scale (SDS) and visual analog scale (VAS). Results indicated that Sevoflurane (group B) animals were having significantly faster induction and recovery rates than Isoflurane (group A) which may be attributed to its least blood gas solubility of Sevoflurane. Mean ± SE values for average maintenance dose volume (Vol %) were 3.16 ± 0.16 for group A and 2.04 ± 0.16 for group B. There was no significant difference in quality of induction and qualitative parameters of recovery between the groups. There was no significant difference in SDS and VAS scales between the groups and the values were within acceptable levels. Thus the quality of recovery and analgesia in both the groups was satisfactory. We do not conclude both the agents have significant analgesic effects though best results can be achieved with opiod analgesic pre medication. It was concluded though induction and recovery characteristics of sevoflurane anaesthesia are faster than isoflurane, both isoflurane and sevoflurane are advantageous inhalant anaesthetics in terms of ease of administration, excellent maintenance quality and rapid and smooth recovery with minimal adverse effects on healthy female dogs subjected for ovariohysterectomy procedure. Although sevoflurane is associated with faster induction and recovery there is no clinical significance in usage with this finding except sevoflurane having low pungency and airway irritation.