Some physiological and biochemical effects of intravenous fluid administration during halothane anaesthesia in the dog

Six dogs with previously implanted arterial, central venous, pulmonary arterial and left atrial catheters received halothane anaesthesia, and halothane anaesthesia plus administration of a balanced electrolyte solution given over one hour, in a cross-over experiment. Parameters measured included temperature, heart rate (HR), respiratory rate (f), arterial and mixed venous blood-gases and acid-base parameters, mean arterial pressure ( AP ), mean pulmonary artery pressure ( PAP ), mean left atrial pressure ( LAP ), mean central venous pressure ( CVP ), packed cell volume (PCV), total plasma protein (TPP), plasma sodium, potassium and chloride concentrations, and urinary sodium and potassium concentrations.
During halothane anaesthesia there were significant decreases in AP , PCV, TPP, f, and significant increases in arterial and mixed venous oxygen, and glucose concentrations, when compared with conscious control values. When intravenous fluid was administered during anaesthesia, there were significant decreases in temperature, AP , PCV and TPP, with significant increases in PAP , CVP and f, when compared with values during anaesthesia alone. After one hour recovery period from anaesthesia, dogs receiving intravenous fluids had significantly decreased PaO₂ values and significantly increased pH when compared with anaesthesia alone. There was an average urinary excretion of 7 mmol of sodium and 5 mmol of potassium during anaesthesia, and 36 mmol of sodium and 8 mmol potassium during fluid administration.