Francisco J. Tendillo

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

REASONS FOR PERFORMING STUDY 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. OBJECTIVES 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. METHODS 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. RESULTS 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. CONCLUSIONS 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. POTENTIAL CLINICAL RELEVANCE Administration of alpha-2 adrenoceptor agonists after inhalent anaesthesia could prevent complications during the recovery period.

Optical aggregometry versus the PFA–100™: experimental studies in pigs treated with propofol

An experimental study of platelet aggregation was performed in 22 male Landrace 2 Large-White crossbred pigs treated with propofol at different doses, to compare the results of optical aggregometry with those of the PFA-100™ (Dade Int., Miami, FL, USA), a new platelet function analyzer. Platelet aggregation was analyzed in basal blood samples by both methods, after which the pigs were divided into three groups: G1, anaesthetic induction with propofol (2 mg/kg intravenously (i.v.)); G2, anaesthetic induction with propofol (2 mg/kg i.v.), followed by a second dose of 1.5 mg/kg; and G3, anaesthetic induction with propofol (2 mg/kg i.v.), followed by 1 h of continuous i.v. infusion at 13 mg/kg/h. Four minutes after propofol injection, blood samples were again taken from each group and studied by both methods. In groups G2 and G3, both methods showed reduced platelet aggregation, while in group G1 neither evidenced an anti-aggregating effect of propofol. Under our experimental conditions: (1) the propofol effect on platelet aggregation depends on the plasma concentration; (2) the results obtained with the two methods are comparable; (3) PFA-100™ may provide an alternative to optical aggregometry for detecting the effects of anaesthetic agents ex vivo .

Aspirin synergistically potentiates isoflurane minimum alveolar concentration reduction produced by morphine in the rat.

Background The combination of opioids and nonsteroidal antiinflammatory drugs is more analgesic than the summed effect of each drug administered separately. This synergism has been used to obtain analgesia in the postoperative period at doses at which side effects are minimal. The aim of this study is to evaluate the analgesic interaction between aspirin and morphine in the rat during isoflurane anesthesia. The reduction in minimum alveolar concentration of isoflurane (MACISO) was used as an objective measure of the analgesic potency of individual drugs and their use in combination. Methods Thirty‐seven male Wistar rats were anesthetized with isoflurane in oxygen, and the MACISO was determined before and after the intravenous administration of aspirin and morphine. Rats were administered morphine alone (1, 3, and 10 mg/kg) or morphine (1 and 3 mg/kg) and aspirin (30 mg/kg). The MACISO was determined from alveolar gas samples at the time of tail clamp. The duration of MACISO reduction was recorded. Results Aspirin did not have an effect on MACISO, (average, 1.35 +/− 0.1%), whereas the combination of morphine (1 and 3 mg/kg) and aspirin (30 mg/kg) produced a reduction in the dose of morphine needed to produce the same degree of MACISO reduction. Actual MACISO+drug data were as follows: 1 mg/kg morphine, 1.17 +/− 0.14%; 3 mg/kg morphine, 0.98 +/− 0.15%; 1 mg/kg morphine plus aspirin, 0.90 +/− 0.04%; 10 mg/kg morphine, 0.63 +/− 0.13%; and 3 mg/kg morphine plus aspirin, 0.64 +/− 0.06%. Conclusions The synergistic effects of aspirin and morphine allow a clinically significant reduction in the requirements of isoflurane and isoflurane plus morphine, and these drug combinations may decrease the side effects associated with the use of single higher, equianalgesic doses of these drugs.