Enflurane anaesthesia for removal of aldosterone producing adenoma

In a 31-year old woman with a six year history of headache and hypertension a diagnosis of primary aldosteronism was made on the basis of urine samples containing 45 mug/day of aldosterone. The preoperative systemic blood pressure was 240 mm Hg systolic and 120 mm Hg diastolic. The serum potassium level was 2.6 mEq/L and other laboratory findings were within normal limits. The patient was to undergo operation. Pre-medication consisted of oral pentobarbitone, intramuscular pethidine and atropine. For induction of anaesthesia, enflurane 2.0-2.5% maximum was given with O2 (21/min) and N2O (61/min); no intravenous agents were used. Suxamethonium chloride 40 mg was administered to facilitate endotracheal intubation. Anaesthesia was maintained with enflurane 1.5-2.0% with 50% N2O and O2. Tubocurarine 27 mg was given for muscle relaxation. When the tumour was manipulated, systemic arterial blood pressure was elevated again to 190 mm Hg systolic and 120 mm Hg diastolic. After removal of the tumour, the arterial pressure and heart rate were stable and recovery from anaesthesia was without circulatory or respiratory complications. Plasma aldosterone levels reached a maximum when the tumour was manipulated and fell to normal levels on the second post-operative day. Cortisol levels were not altered markedly even when the tumour was handled. These data imply that adrenocortical response to enflurane anaesthesia as jadged by plasma aldosterone levels would be different from that as estimated by plasma cortisol levels.