QJM Advance Access originally published online on July 22, 2006
QJM 2006 99(8):513-522; doi:10.1093/qjmed/hcl065
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Respiratory failure in acute organophosphorus pesticide self-poisoning
From the 1Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK, 2South Asian Clinical Toxicology Research Collaboration (www.sactrc.org), 3Ox-Col Collaboration, Department of Clinical Medicine, University of Colombo, Sri Lanka, 4Department of Intensive Care, St Thomas's Hospital, London, UK, 5Walther Straub Institute of Pharmacology and Toxicology, Ludwig Maximilian's University, Munich, 6Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany, and 7Department of Clinical Pharmacology & Toxicology, Canberra Clinical School, Canberra, Australia
Address correspondence to Dr M. Eddleston, Scottish Poisons Information Bureau, Royal Infirmary, Little France, Edinburgh EH16 4SA. email: eddlestonm{at}eureka.lk
Received 17 January 2006 and in revised form 4 April 2006
Background: Acute organophosphorus (OP) pesticide poisoning is a major clinical problem in the developing world. Textbooks ascribe most deaths to respiratory failure occurring in one of two distinct clinical syndromes: acute cholinergic respiratory failure or the intermediate syndrome. Delayed failure appears to be due to respiratory muscle weakness, but its pathophysiology is unclear.
Aim: To describe the clinical patterns of OP-induced respiratory failure, and to determine whether the two syndromes are clinically distinct.
Design: Prospective study of 376 patients with confirmed OP poisoning.
Methods: Patients were observed throughout their admission to three Sri Lankan hospitals. Exposure was confirmed by butyrylcholinesterase and blood OP assays.
Results: Ninety of 376 patients (24%) required intubation: 52 (58%) within 2 h of admission while unconscious with cholinergic features. Twenty-nine (32%) were well on admission but then required intubation after 24 h while conscious and without cholinergic features. These two syndromes were not clinically distinct and had much overlap. In particular, some patients who required intubation on arrival subsequently recovered consciousness but could not be extubated, requiring ventilation for up to 6 days.
Discussion: Respiratory failure did not occur as two discrete clinical syndromes within distinct time frames. Instead, the pattern of failure was variable and overlapped in some patients. There seemed to be two underlying mechanisms (an early acute mixed central and peripheral respiratory failure, and a late peripheral respiratory failure) rather than two distinct clinical syndromes.