Cardiopulmonary function during 5 hours of constant‐dose isoflurane in laterally recumbent, spontaneously breathing horses

Abstract

Hemodynamic and respiratory effects of 5 h of unvarying 1.57%, end-tidal (1.2 MAC) isoflurane in O2 anesthesia were characterized in ten left laterally recumbent horses. Compared to base line values at 30 min of constant dose isoflurane, cardiac output, hematocrit, total plasma solids, PaCO2, and peak inspired gas flow progressively and significantly (P less than 0.05) increased over the course of study. Arterial blood pressure increased (P less than 0.05) during the first 2 h of constant dose of isoflurane then decreased and remained near base line values. Inspiratory time progressively decreased with time of anesthesia. All horses recovered from anesthesia uneventfully within 1 h of termination of isoflurane.

Interactions of morphine and isoflurane in horses

“…Allowing for the influence of anesthetic dose and time of measurement and the fact that broad comparisons were made of differently summarized data, results of HR and arterial blood pressure measurements during only ISO anesthesia in the study reported here are comparable to results of other studies 18,19,21 of ISO by our laboratory group. Values within a variable grouping before injection of saline solution or MOR did not differ in this study.…”

“…18,19,21 Following injection of saline solution or the low dose of MOR, PaO 2 and PaCO 2 did not change significantly with time. Lack of change in PaCO 2 with time following injection of saline solution differs from results of other studies 21,27 of ISO anesthesia in which there were time-related effects in the form of a temporal increase in PaCO 2 . The difference between results of the study reported here and those of other studies is likely a result of differences in methods used.…”

“…The calculated base balance was initially within the reference range 18,19,21 and did not change with time during the study. Accordingly, for simplicity, pH a and data for base balance were not included here.…”

“…We used techniques that have been described elsewhere for our laboratory group. 19,21 Briefly, a base-apex lead ECG a was used to monitor heart rate (HR) and rhythm. An 18-gauge 2-inch catheter was inserted percutaneously into the right carotid artery, which had been surgically elevated to a position just beneath the skin during the months preceding the study.…”

Time-Related Changes of the Cardiovascular System during Maintenance Anesthesia with Sevoflurane and Isoflurane in Horses.

“…Sev-anesthesia is considered to be more useful especially for orthopedic surgery than halothane or isoflurane (Iso)-anesthesia because it provides excellent recoveries in horses [5]. Halothane and Iso have been well examined for effects on the time-related changes of cardiovascular system in horses [6,17]. If the surgeries are prolonged, it should be necessary for the anesthetists to know the time-related effects of cardiovascular system with anesthetics.…”