1. Surgical and Respiratory Intensive Care Units, Departments of Anaesthesia and Medicine and Surgery, University of Cape Town and Groote Schuur Hospital, Cape Town, South Africa
2. Division of Clinical Pharmacology, Johns Hopkins School of Medicine, Baltimore, U.S.A.
3. Departments of Anaesthesia and Medicine and Surgery, University of Cape Town and Groote Schuur Hospital, Cape Town, South Africa.