Effects of alpha-2 adrenoceptor agonists during recovery from isoflurane anaesthesia in horses.

Abstract

Recovery from inhalant anaesthesia in the horse is a critical and difficult period to manage; however, several factors could help to obtain a calm recovery period including choice of anaesthetic and analgesic procedure used and the conditions under which anaesthetic maintenance and recovery occur. The objective of this study was to evaluate and compare the quality of recovery in horses administered saline, xylazine, detomidine or romifidine during recovery from isoflurane anaesthesia. Six mature and healthy horses were premedicated with i.v. xylazine and butorphanol, and anaesthesia induced using ketamine. After 2 h of inhalant anaesthesia with isoflurane vaporised in oxygen, saline solution, xylazine (0.1 mg/kg bwt), detomidine (2 microg/kg bwt) or romifidine (8 pg/kg bwt) were administered. The quality of recovery of each horse and the degree of sedation and ataxia were evaluated. Cardiovascular and respiratory parameters were recorded, and arterial blood samples obtained and analysed for pH, PO2 and PCO2 during recovery. Quality of recovery was better in groups treated with alpha-2 adrenergic receptors agonists, showing less ataxia. Degree of sedation was greater in the romifidine group. We concluded that the administration of alpha-2 adrenoceptor agonists during recovery from isoflurane anaesthesia in horses prolonged and improved the quality of recovery without producing significant cardiorespiratory effects. Administration of alpha-2 adrenoceptor agonists after inhalent anaesthesia could prevent complications during the recovery period.