The influence of mechanical ventilation on physiological parameters in ball pythons (Python regius)

Abstract

Mechanical ventilation is widely recommended for reptiles during anesthesia, and while it is well-known that their low ectothermic metabolism requires much lower ventilation than in mammals, very little is known about the influence of ventilation protocol on the recovery from anesthesia. Here, 15 ball pythons (Python regius) were induced and maintained with isoflurane for 60min at one of three ventilation protocols (30, 125, or 250mlmin^-1kg^-1 body mass) while an arterial catheter was inserted, and ventilation was then continued on 100% oxygen at the specified rate until voluntary extubation. Mean arterial blood pressure and heart rate (HR) were measured, and arterial blood samples collected at 60, 80, 180min and 12 and 24h after intubation. In all three groups, there was evidence of a metabolic acidosis, and snakes maintained at 30mlmin^-1kg^-1 experienced an additional respiratory acidosis, while the two other ventilation protocols resulted in normal or low arterial PCO₂. In general, normal acid-base status was restored within 12h in all three protocols. HR increased by 143±64% during anesthesia with high mechanical ventilation (250mlmin^-1kg^-1) in comparison with recovered values. Recovery times after mechanical ventilation at 30, 125, or 250mlmin^-1kg^-1 were 289±70, 126±16, and 68±7min, respectively. Mild overventilation may result in a faster recovery, and the associated lowering of arterial PCO₂ normalised arterial pH in the face of metabolic acidosis.

Keywords: Acid-base balance; Anesthesia; Isoflurane; Python regius; Reptile; Ventilation.