Anaesthetic hazards of aortocaval fistula. A 66-yr-old man was anaesthetized for repair of a suspected ruptured aortic aneurysm. He became deeply cyanosed and suffered two episodes of asystole as the surgeons entered the abdomen. After the aorta was cross-clamped his condition improved markedly and no further problems ensued. Surgical exploration demonstrated intact aneurysms of the aorta and left iliac artery, the former containing a 3-4 cm long aortocaval fistula. The aneurysms and fistula were repaired and his further course was uncomplicated. Potential causes for the cyanosis and cardiac arrest in this patient are discussed. 