Hyperbaric Oxygen Therapy and Carbon Monoxide Poisoning
Hyperbaric Oxygen Therapy and Carbon Monoxide Poisoning
Question
Is hyperbaric oxygen therapy still the standard of care for carbon monoxide poisoning?
Hyperbaric oxygen therapy (HBO) for the treatment of carbon monoxide (CO) poisoning was first discussed by Haldane in the 1890s and was first used in the 1960s. At the time, CO toxicity was thought to result entirely from the relative anemia and hypoxia imposed by the formation of carboxyhemoglobin (CO-Hgb). We now know that the pathophysiology of CO poisoning is much more complex and involves direct toxicity at the cellular level. Mechanisms and potential treatments for CO poisoning are an area of active basic science and animal research. Clinically intriguing is a syndrome of apparent recovery followed approximately 2 weeks later by behavioral and/or neurologic deterioration. This is known as Delayed Neurologic Sequelae (DNS) and it may be debilitating and permanent. The exact cause and incidence of DNS remains elusive as does a precise definition.
Clinical trials evaluating the use of HBO for CO poisoning have yielded conflicting results. In addition, because of significant variations in study design (population studied and outcomes measured) it is difficult to draw firm conclusions based on the evidence. A Cochrane review concluded that HBO for CO poisoning is not proven to reduce the incidence of adverse neurologic outcomes. A recent American College Emergency Physicians clinical policy concluded that HBO is a "therapeutic option" for CO poisoning but that its use "cannot be mandated" at this point given the current data. Not all experts agree with these conclusions, which contributes to the controversy surrounding this issue.
The standard of care regarding HBO for CO poisoning varies from institution to institution based on expert opinion. In general, most would agree that HBO may be considered for patients with loss of consciousness, persistent neurologic abnormalities, cardiac dysfunction, or in pregnant patients with elevated CO-Hbg levels (typically ≥ 15%). Some practitioners use neuropsychometric testing, absolute CO-Hgb levels (typically ≥ 25%) and metabolic acidosis to guide treatment decisions. Logistical considerations regarding patient transfer may also arise. In addition, HBO itself is not risk-free. Given the debate as well as the active ongoing discovery regarding CO poisoning and the role of HBO, the emergency physician would be prudent to seek the advice of the local toxicologist, poison center, or physician specializing in hyperbaric medicine for guidance when considering HBO for a patient poisoned by CO.
Question
Is hyperbaric oxygen therapy still the standard of care for carbon monoxide poisoning?
Response From the Expert
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Louise Kao, MD
Assistant Professor of Clinical Emergency Medicine, Director of Medical Toxicology Fellowship Program, Indiana University School of Medicine, Indianapolis; Physician, Methodist Hospital, Indiana Poison Center, Indianapolis, Indiana |
Hyperbaric oxygen therapy (HBO) for the treatment of carbon monoxide (CO) poisoning was first discussed by Haldane in the 1890s and was first used in the 1960s. At the time, CO toxicity was thought to result entirely from the relative anemia and hypoxia imposed by the formation of carboxyhemoglobin (CO-Hgb). We now know that the pathophysiology of CO poisoning is much more complex and involves direct toxicity at the cellular level. Mechanisms and potential treatments for CO poisoning are an area of active basic science and animal research. Clinically intriguing is a syndrome of apparent recovery followed approximately 2 weeks later by behavioral and/or neurologic deterioration. This is known as Delayed Neurologic Sequelae (DNS) and it may be debilitating and permanent. The exact cause and incidence of DNS remains elusive as does a precise definition.
Clinical trials evaluating the use of HBO for CO poisoning have yielded conflicting results. In addition, because of significant variations in study design (population studied and outcomes measured) it is difficult to draw firm conclusions based on the evidence. A Cochrane review concluded that HBO for CO poisoning is not proven to reduce the incidence of adverse neurologic outcomes. A recent American College Emergency Physicians clinical policy concluded that HBO is a "therapeutic option" for CO poisoning but that its use "cannot be mandated" at this point given the current data. Not all experts agree with these conclusions, which contributes to the controversy surrounding this issue.
The standard of care regarding HBO for CO poisoning varies from institution to institution based on expert opinion. In general, most would agree that HBO may be considered for patients with loss of consciousness, persistent neurologic abnormalities, cardiac dysfunction, or in pregnant patients with elevated CO-Hbg levels (typically ≥ 15%). Some practitioners use neuropsychometric testing, absolute CO-Hgb levels (typically ≥ 25%) and metabolic acidosis to guide treatment decisions. Logistical considerations regarding patient transfer may also arise. In addition, HBO itself is not risk-free. Given the debate as well as the active ongoing discovery regarding CO poisoning and the role of HBO, the emergency physician would be prudent to seek the advice of the local toxicologist, poison center, or physician specializing in hyperbaric medicine for guidance when considering HBO for a patient poisoned by CO.