Effects of inhalational anesthesia on blood gases and pH in California sea lions

Abstract

Despite the widespread use of inhalational anesthesia with spontaneous ventilation in many studies of otariid pinnipeds, the effects and risks of anesthetic‐induced respiratory depression on blood gas and pH regulation are unknown in these animals. During such anesthesia in California sea lions ( Zalophus californianus ), blood gas and pH analyses of opportunistic blood samples revealed routine hypercarbia (highest P CO 2 = 128 mm Hg [17.1 kP a]), but adequate arterial oxygenation ( P O 2 > 100 mm Hg [13.3 kP a] on 100% inspiratory oxygen). Respiratory acidosis (lowest pH = 7.05) was limited by the increased buffering capacity of sea lion blood. A markedly widened alveolar‐to‐arterial P O 2 difference was indicative of atelectasis and ventilation‐perfusion mismatch in the lung secondary to hypoventilation during anesthesia. Despite the generally safe track record of this anesthetic regimen in the past, these findings demonstrate the value of high inspiratory O 2 concentrations and the necessity of constant vigilance and caution. In order to avoid hypoxemia, we emphasize the importance of late extubation or at least maintenance of mask ventilation on O 2 until anesthetic‐induced respiratory depression is resolved. In this regard, whether for planned or emergency application, we also describe a simple, easily employed intubation technique with the Casper “zalophoscope” for sea lions.

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