Effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and clinicopathologic variables in horses

Abstract

Results indicate that desflurane, like other inhalation anesthetics, causes profound hypoventilation in horses. The magnitude of cardiovascular depression is related to dose and mode of ventilation; cardiovascular depression is less severe at doses of 1X to 1.5X MAC, compared with known effects of other inhalation anesthetics under similar conditions. Desflurane is not metabolized to an important degree and does not appear to prominently influence renal function or hepatic cellular integrity or function.

Use of Propofol–Xylazine and the Anderson Sling Suspension System for Recovery of Horses from Desflurane Anesthesia

“…Anesthesia was maintained with desflurane in oxygen (6 L/min) through a large animal circle anesthetic delivery circuit. One hour after ketamine administration, the alveolar (end tidal; ET) desflurane concentration was reduced and maintained at 9.7% (equivalent to 1.2 MAC as determined previously for the horse in this laboratory 5 ) for the remainder of the 4‐hour‐anesthesia period (i.e., 3 hours of constant dose desflurane).…”

Inhaled Anesthetics in Horses

“…Isoflurane doses ranging between 1-to-2 times MAC linearly decrease respiratory rate, 73 but sevoflurane and desflurane concentrations above 1.5 times MAC may be associated with a high incidence of apnea due to greater respiratory depression. 74,75 Tidal volume also decreases with dose, and this response is most steep above 1.5 times MAC. Temporal increases in respiratory depression during the first 2 hours of anesthesia parallels reductions in respiratory rate.…”

“…Although the modern ether-type anesthetics are potent vasodilators, reductions in blood pressure above 1 MAC are largely due to dose-dependent decreases in stroke volume and cardiac output. 73–75 When ventilated to maintain isocapnea, cardiac output is much better preserved between 1.0-to-1.5 times MAC with desflurane and sevoflurane than with isoflurane. However, at concentrations above 1.5 times MAC, cardiac output is significantly higher with desflurane than with either isoflurane or sevoflurane.…”

“…However, at concentrations above 1.5 times MAC, cardiac output is significantly higher with desflurane than with either isoflurane or sevoflurane. 73–75 Desflurane is associated with increased sympathetic tone, particularly following large concentration changes, 78 which might mask some of the hypotension observed with other agents. During the first 2 hours of anesthesia, at least with isoflurane in horses, there are also time-dependent increases in stroke volume, cardiac output, and blood pressure that may be the result of endogenous β-adrenergic receptor activation.…”

“…15,74,75,77,94,95 The Meyer-Overton hypothesis states that as lipid solubility increases (as reflected by an increased λ oil:ga ), the anesthetic potency also increases (as reflected by a decreased MAC).…”