Haemodynamic and blood gas changes in buffaloes (Bubalus bubalis) in the supine position following thiopentone anaesthesia with premedication.

Studies were undertaken on seven adult female buffaloes (Bubalus bubalis) premedicated with triflupromazine hydrochloride (0.3 mg/kg) and chloral hydrate (30 mg/kg). Anaesthesia was induced with thiopentone sodium (10 mg/kg) and animals were kept under intermittent positive pressure ventilation. Measurements were made for 30 min in the lateral position, for 20 min in the supine position and subsequently for 40 min again in the lateral position. Regurgitation during anaesthesia was avoided by evacuation of the rumen by rumenotomy two days prior to the experiment. When animals were in the lateral position there were minimal changes in arterial pressure and heart rate but central venous pressure rose. These changes were related to intermittent positive pressure ventilation. In the supine position, increase in heart rate (28%) was associated with profound hypotension (56%) and decrease in central venous pressure (171%) in these animals. There was a fall in venous oxygen tension and a marked increase (91%) in oxygen extraction ratio. Restoration to the lateral position ameliorated all these changes rapidly. It was suggested that a 'low pressure-low flow' circulatory state exists in anaesthetised adult buffaloes in the supine position.