Temporal and concentration effects of isoflurane anaesthesia on intestinal tissue oxygenation and perfusion in horses

Effects of positive end‐expiratory pressure titration on intestinal oxygenation and perfusion in isoflurane anaesthetised horses

“…Therefore it can be speculated that there may be a different regulation for the intestinal blood flow in horses compared with other species. In a previous study in isoflurane anaesthetised horses autoregulation of the intestinal perfusion was preserved until a blood pressure of 60 mmHg or CI of 48 ml/kg/min induced by increasing isoflurane concentrations was reached . The pharmacologic negative inotropic and vasodilatory effect of high isoflurane concentrations in contrast to a constant plane of anaesthesia in the current study could explain the earlier decompensation of autoregulation.…”

Effects of controlled hypoxemia or hypovolemia on global and intestinal oxygenation and perfusion in isoflurane anesthetized horses receiving an alpha-2-agonist infusion

“…Further the time of hypoxemia was probably too short to cause severe myocardial changes. The fact that we had no changes in either CI or MAP further might explain the lack in changes in gastrointestinal perfusion during hypoxemia in this study [ 6 ]. We cannot exclude that longer or more severe periods of hypoxemia may affect the gastrointestinal perfusion in horses.…”

“…In dogs, pigs and rats it has been shown that in a hypovolemic situation the perfusion of the skin, the skeletal muscles and the gastrointestinal tract is not a priority and is disproportionally reduced compared to the muscle tissue [ 34 – 36 ]. In contrast a study with nine healthy horses under isoflurane anesthesia showed that gastrointestinal perfusion was preserved until a threshold blood pressure of about 60 mmHg or cardiac output lower 50 mL/kg /min were reached [ 6 ]. These authors assumed that differences in the regulation of large and small vessel tone [ 37 ].…”

“…Although there is clear evidence that hemodynamic parameters are stable and time-independent during isoflurane anesthesia in horses [ 5 , 6 ], it is possible that the hypovolemia experiment was effect first by the long duration of anesthesia and second by the hypoxemia experiment. Due to ethical reasons, we decided to use these horses for multiple experiments as euthanasia was necessary in these animals for tissue sampling of an associated surgical study.…”

“…Dose-dependent cardiovascular depression by isoflurane has been well described and decreased cardiac index (CI) is a direct effect of isoflurane on myocardial contractility, leading to a reduction in stroke volume and consequent, in combination with its vasodilatory effects, to a reduction in mean arterial blood pressures (MAP) [ 5 ]. In horses it has been shown, that states of low blood pressure and low cardiac output will lead to impaired intestinal perfusion [ 6 ]. However, information on the influence of acute blood loss on gastrointestinal microperfusion is limited in this species.…”