Hyperbaric Oxygen (HBO) for Carbon Monoxide Poisoning ===================================================== þ Seems to work: - 3 treatments make a small but significant difference in neuropsych testing. [Weaver KL, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. N Engl J Med 2002;347(14):1057-67.] - One limited Australian study showed no efficacy, but significantly clouded by many methodological limitations. [Scheinkestel CD, et al. Hyperbaric or normobaric oxygen for acute carbon monoxide poisoning: a randomised controlled clinical trial. Med J Austral 1999;170:203-210.] þ Excerpts from a talk by John J. Kelly, DO, FACEP Associate Chairman Department of Emergency Medicine Albert Einstein Medical Center, Philadelphia and Dr. Thom at the PaACEP 1998 Conference: þ Evidence that HBO works - There are multiple anecdotal reports describing a favorable outcome with HBO2 treatment. Conversely, there are reports of patients with acute CO poisoning treated without HBO2 which also demonstrate a favorable outcome. [Weaver LK, Hopkins RO, Larson -Lohr V. Neuropsychologic and functional recovery in severe CO poisoning without HBO2. Ann Emerg Med 1996;27(6):736-740.] [Weaver LK. Randomized clinical trial in CO poisoning needed. (Letter). Am J Emerg Med 1994;12(6):685.] - Without the information from a double-blind, controlled randomized clinical trial, the main role of HBO2 in acute CO poisoning will remain enigmatic. [Gabb G, Robin ED. Hyperbaric Oxygen - A therapy in search of diseases. Chest 1987; 92(6):1074-1082.] [Tibbles PM, Perrotta PL. Treatment of CO poisoning: A critical review of human outcome studies comparing nomobaric oxygen with hyperbaric oxygen. Ann Emerg Med 1994;24 :269-276.] [Segers D, Welch L. Carbon Monoxide controversies: Neuro-psychological testing, mechanism of toxicity, and hyperbaric oxygen. Ann Emerg Med 1994; 24: 242-248.] þ HBO has risks: - [Sloan EP, Murphy DG, Hart R, et al. Complications and protocol consideration in CO poisoned patients who require HBO2: Report from a ten-year experience. Ann Emerg Med 1989; 18. 629-634.] [Hampson NB, Simonson SG, Kramer CC, Piantidosi CA. Central nervous system oxygen toxicity during hyperbaric treatment of acute CO poisoning: Comparison of treatment pressures. (Abstract) Undersea and Hyperbaric Med 1994;21 (Suppl):13.] [Gabb G, Robin ED. Hyperbaric Oxygen - A therapy in search of diseases. Chest 1987; 92(6):1074-1082.] - HBO may increase risk of seizures in CO poisoning - Other known risks of HBO2 include barotrauma (ears, sinuses, middle ear hemorrhage, deafness), oxygen toxicity (brain, lung), decompression sickness (pneumothorax, nitrogen emboli), fire hazard. þ Evidence that HBO _doesn't_ help - [Hopkins RO, Weaver LK: Does late repetitive HBO2 improve delayed neurologic sequellae associated with CO poisoning? (Abstract) Undersea Biomed Res 1991; 18(Suppl):34.] 86 consecutive CO poisoned patients: 5.8% developed DNS and 2.7% developed persistent neurologic sequellae. - [Hopkins RO, Weaver LK: Long-term outcome in subjects with CO poisoning. (Abstract) Undersea and Hyperbaric Med 1994; 21(Suppl):17.] [Min SK. A brain syndrome associated with delayed neuro-psychiatric sequellae following acute CO intoxication. Acta Psychiatr Scand 1986;73: 80-86.] HBO2 does not seem to alter the incidence of delayed neurologic sequellae. - Animal studies show that HBO must be started within 90 minutes to help: [Thom SR: Antagonism of carbon monoxide-mediated brain lipid peroxidation by hyperbaric oxygen. Toxicol Appl Pharmacol 1990;105:340-344.] [Thom SR: Functional inhibition of leukocyte B2 integrins by hyperbaric oxygen in carbon monoxide-mediated brain injury in rats. Toxicol Appl Pharmacol 1993;123:248-256.] þ Patient sensitivity to CO may have a big role in long-term outcome: - [Weaver LK, Hopkins RO, Larson-Lohr V. Neuropsychologic and functional recovery in severe CO poisoning without HBO2. Ann Emerg Med 1996;27(6):736-740.] [Weaver LK. Randomized clinical trial in CO poisoning needed. (Letter). Ann J Emerg Med 1994;12(6):685.] - [Hopkins RO, Weaver LK: Does late repetitive hyperbaric oxygen improve delayed neurologic sequellae associated with carbon monoxide poisoning? (Abstract) Undersea Biomed Res 1991;18 (Supplement):34.] - [Hopkins RO, Weaver LK: Long-term outcome in subjects with carbon monoxide poisoning. (Abstract) Undersea and Hyperbaric Med 1994;21 (Supplement):17.] þ Acute mortality from CO is cardiac: - [J A P 39:482, 1975] þ Neurological injury is caused by vascular problems [J Neuroradiol 15: 381, 1988] [Am J Neuroradiol 14: 169, 1993] [Eur Neurol 31: 380, 1991] [J Nucl Med 33: 1696, 1992] [Und Hy Med 22: 9, 1995] [Physiol Rev 58: 656, 1978] [J Neurol 240: 430, 1993] þ Evidence that HBO _does_ help CO poisoning - Mortality: 30.1% -> 13.5 % [Ann Med Interne 120: 335, 1969] [Acta Anesth Scand 32: 276, 1988] - Morbidity: ~20% -> <4% [Arch Neurol 40: 433, 1983] [Ann Emerg Med 14:1163, 1985] [Clin Toxicol 23: 315, 1985] [Ann Emerg Med 14:1168, 1985] þ Prospective Trials - Raphael, 1989: 34-45% Sequelae, + or - HBO but Only 2 ATA, tx >6 h - Thom, et al. Ann. Emerg. Med. 25: 474-480, 1995: 23% w/o, 0% with HBO, not blinded, mild-moderate poisoning, n=60 - Ducasse, et al. Undersea & Hyperbaric Medicine 22: 9, 1996: Prospective, randomized trial patients with temporary loc, COHb ~ 23% TX within 2 hrs of poisoning 13 ambient (NBO), 13 hyperbaric oxygen (HBO) follow-up at 3 weeks- abnormal EEG: 8/10 NBO; 0/8 HBO impaired cerebral vasodilation with NBO 80% w/o, 0% with HBO, not blinded, n=26 - Scheinskestel, et al., Undersea & Hyperbaric Med. 23 (suppl): 7,'96: Prospective, randomized, blinded 145 patients with severe co poisoning no difference nbO vs 2.8 ATA X 60 min, 42% follow-up, mean delay to tx: 9.3 h 62-71% sequelae, + or - HBO BUT 1 in 3 false +, 42%, no f/u - Mathieu, 1996: 15% w/o 9.5 % with HBO 575 patients, mild-moderate poisoning. þ Lab Tests: - CO levels - Lactate: may be useful - [J. Trauma 22: 311, 1982] [Arch. Neurol. 40: 433, 1983] [Arch. Toxicol. 57: 196, 1985]