Effect of Intermittent Positive Pressure Ventilation (IPPV) on Acid-Base Balance and Plasma Electrolytes during Isoflurane Anaesthesia in Sulphur-Crested Cockatoos (Cacatua galerita galerita)

The objective of the study was to investigate the effect of Intermittent Positive Pressure Ventilation (IPPV) on acid-base balance and plasma electrolytes during isoflurane anaesthesia in sulphur-crested cockatoos (Cacatua galerita galerita). Anaesthesia was induced in six birds by mask using a T-piece with 3.0% isoflurane. Blood gases, plasma electrolytes, PCV and Total Protein (TP) were monitored for one hour during Spontaneous Ventilation (SV) and IPPV. IPPV was instituted by engaging the pop-off valve (IPPVa) of the circle absorber or by squeezing the breathing bag (IPPVb). Results showed that during SV, pCO2, pO2, [HCO3], BE, C+CO2 and PO4 increased significantly, while [Na], [K] and [Ca] did not change significantly. During IPPV, pCO2 and pO2 decreased, while C+CO2 increased during the initial 30 min. [HCO3] increased during IPPVa only in the first 30 min. BE increased only in the first 30 min of IPPV. There was a marginal increase and decrease in PO4 during SV and IPPV, respectively. [Na], [K] and [Ca] remained stable during both SV and IPPV. Subtle decreases were noted for [Cl], TP and PCV during SV. It was concluded that mixed metabolic and respiratory acidosis occurs during SV in isoflurane-anaesthetised cockatoos. Metabolic acidosis that develops during isoflurane anaesthesia in spontaneously ventilating birds is reversible to some extent by IPPV, possibly through a mixed acidosis-alkalosis, respiratory alkalosis and a non-respiratory contribution to alkalosis mechanism. Reversal of Bohr Effect occurs during IPPV in isoflurane-anaesthetised cockatoos. Studies are indicated to understand the causes of decreased oxygen saturation in apparently alkalotic birds.