Neil B. Hampson

Carbon monoxide poisoning — a public health perspective

Carbon monoxide (CO) may be the cause of more than one-half of the fatal poisonings reported in many countries; fatal cases also are grossly under-reported or misdiagnosed by medical professionals. Therefore, the precise number of individuals who have suffered from CO intoxication is not known. The health effects associated with exposure to CO range from the more subtle cardiovascular and neurobehavioral effects at low concentrations to unconsciousness and death after acute or chronic exposure to higher concentrations of CO. The morbidity and mortality resulting from the latter exposures are described briefly to complete the picture of CO exposure in present-day society. The symptoms, signs, and prognosis of acute CO poisoning correlate poorly with the level of carboxyhemoglobin (COHb) measured at the time of hospital admission; however, because CO poisoning is a diagnosis frequently overlooked, the importance of measuring COHb in suspicious settings cannot be overstated. The early symptoms (headache, dizziness, weakness, nausea, confusion, disorientation, and visual disturbances) also have to be emphasized, especially if they recur with a regular periodicity or in the same environment. Complications occur frequently in CO poisoning. Immediate death is most likely cardiac in origin because myocardial tissues are most sensitive to the hypoxic effects of CO. Severe poisoning results in marked hypotension, lethal arrhythmias, and electrocardiographic changes. Pulmonary edema may occur. Neurological manifestation of acute CO poisoning includes disorientation, confusion, and coma. Perhaps the most insidious effect of CO poisoning is the development of delayed neuropsychiatric impairment within 2-28 days after poisoning and the slow resolution of neurobehavioral consequences. Carbon monoxide poisoning during pregnancy results in high risk for the mother by increasing the short-term complication rate and for the fetus by causing fetal death, developmental disorders, and chronic cerebral lesions. In conclusion, CO poisoning occurs frequently; has severe consequences, including immediate death; involves complications and late sequelae; and often is overlooked. Efforts in prevention and in public and medical education should be encouraged.

Practice Recommendations in the Diagnosis, Management, and Prevention of Carbon Monoxide Poisoning

Carbon monoxide (CO) poisoning is common in modern society, resulting in significant morbidity and mortality in the United States annually. Over the past two decades, sufficient information has been published about carbon monoxide poisoning in the medical literature to draw firm conclusions about many aspects of the pathophysiology, diagnosis, and clinical management of the syndrome, along with evidence-based recommendations for optimal clinical practice. This article provides clinical practice guidance to the pulmonary and critical care community regarding the diagnosis, management, and prevention of acute CO poisoning. The article represents the consensus opinion of four recognized content experts in the field. Supporting data were drawn from the published, peer-reviewed literature on CO poisoning, placing emphasis on selecting studies that most closely mirror clinical practice.

Carboxyhemoglobin levels in carbon monoxide poisoning: do they correlate with the clinical picture? ☆

OBJECTIVE It is commonly written that carboxyhemoglobin (COHb) measurements correlate with the clinical presentation of patients poisoned with carbon monoxide (CO). However, the evidence supporting this concept is scanty. The present study was performed to analyze COHb measurements in a large population of patients with CO poisoning to determine whether clinically significant correlates exist. METHODS Records of all patients treated with hyperbaric oxygen for acute CO poisoning at a single private academic medical center from 1978 to 2005 were reviewed. The COHb measurements were analyzed with regard to sex, age, source of CO, loss of consciousness, endotracheal intubation, arterial pH, and death. RESULTS Data from 1603 CO-poisoned patients were reviewed, and 1407 were included in the final analysis. Statistically higher COHb measurements were associated with male sex (24.2% +/- 11.2% vs 21.5% +/- 11.6), adult age range (24.0% +/- 11.0% vs 19.5% +/- 10.3%), poisoning by CO from fires (25.7% +/- 12.1%) or motor vehicles (22.7% +/- 24.7%), loss of consciousness (24.3% +/- 12.2% vs 22.3% +/- 9.4%), lower arterial pH, and death (32.1% +/- 12.8% vs 23.1% +/- 0.9%). CONCLUSIONS Despite the fact that statistically significant differences in average COHb measurements were seen with regard to a number of variables, the clinical significance of these differences appeared to be minimal. Moreover, the utility of COHb measurements as predictors of clinical status in CO poisoning was not apparent. At least in part, this likely relates to delay and interval oxygen administration before obtaining COHb measurements.

Emergency department visits for carbon monoxide poisoning in the Pacific Northwest

This study was conducted to determine the annual number of emergency department (ED) visits and rate of hyperbaric oxygen (HBO2) treatment for carbon monoxide (CO) poisoning in Washington, Idaho, and Montana. All hospital emergency departments and hyperbaric treatment facilities in the region were surveyed by mail and telephone regarding their patient treatment experience for calendar year 1994. Results demonstrated that there were approximately 2.51 million total ED visits in 1994 in the three states studied. Among these, an estimated 1,325 individuals were seen with carbon monoxide poisoning (52.9 CO cases per 100,000 ED visits; 18.1 CO cases per 100,000 population). A total of 91 patients were treated with HBO2, yielding an HBO2 treatment rate of 6.9% of those evaluated in EDs. Extrapolating these figures to the US population suggests that the number of individuals seeking emergency medical care for CO poisoning is much greater than is commonly quoted. Even after correcting for the known increased rate of CO poisoning in the Pacific Northwest, the incidence of nonfatal poisoning appears to be significantly higher than may be appreciated from previous reports.

Selection criteria utilized for hyperbaric oxygen treatment of carbon monoxide poisoning

Medical directors of North American hyperbaric oxygen (HBO) facilities were surveyed to assess selection criteria applied for treatment of acute carbon monoxide (CO) poisoning within the hyperbaric medicine community. Responses were received from 85% of the 208 facilities in the United States and Canada. Among responders, 89 monoplace and 58 multiplace chamber facilities treat acute CO poisoning, managing a total of 2,636 patients in 1992. A significant majority of facilities treat CO-exposed patients with coma (98%), transient loss of consciousness (LOC) (77%), ischemic changes on electrocardiogram (91%), focal neurologic deficits (94%), or abnormal psychometric testing (91%), regardless of carboxyhemoglobin (COHb) level. Although 92% would use HBO for a patient presenting with headache, nausea, and COHb 40%, only 62% of facilities utilize a specified minimum COHb level as the sole criterion for HBO therapy of an asymptomatic patient. When COHb is used as an independent criterion to determine HBO treatment, the level utilized varies widely between institutions. Half of responding facilities place limits on the delay to treatment for patients with only transient LOC. Time limits are applied less often in cases with persistent neurologic deficits. While variability exists, majority opinions can be derived for many patient selection criteria regarding the use of HBO in acute CO poisoning.

Risk factors for short-term mortality from carbon monoxide poisoning treated with hyperbaric oxygen*

Objective:Carbon monoxide (CO) poisoning is common in the United States, accounting for approximately 2,700 deaths annually. Few publications have described the mortality rate of CO-poisoned patients who survive to reach a hospital and die despite maximal medical care. Further, while risk factors for cognitive sequelae in survivors of CO poisoning have become clearer recently, factors associated with death are less well defined. This study was conducted to 1) determine the short-term mortality risk for patients treated with hyperbaric oxygen for CO poisoning, and 2) determine whether any factors related to the poisoning episode are predictive of mortality. Design/Setting/Patients:A departmental database and medical records of 1,505 consecutive patients treated with hyperbaric oxygen at a single institution from 1978 to 2005 were reviewed. Measurements:Demographic and clinical data were extracted for analysis. Mortality data, including cause of death, were obtained through a search of the National Death Index of the National Center for Health Statistics. Main Results:A total of 38 patients experienced short-term mortality from their episode of CO poisoning, yielding a death rate of 2.6% in medically treated patients. Characteristics significantly associated with mortality included fire as a source of CO, loss of consciousness, carboxyhemoglobin level, arterial pH, and presence of endotracheal intubation during hyperbaric treatment. Conclusions:The mortality rate for medically treated CO-poisoned patients in this series was 2.6%, similar to the limited combined experience previously reported in the literature. Factors most strongly associated with mortality were severe metabolic acidosis and need for endotracheal intubation. LEARNING OBJECTIVESOn completion of this article, the reader should be able to: List the causes of carbon monoxide poisoning. Describe factors influencing mortality after carbon monoxide poisoning. Use this information in a clinical setting. The authors have disclosed that they have no financial relationships with or interests in any commercial companies pertaining to this educational activity. All faculty and staff in a position to control the content of this CME activity have disclosed that they have no financial relationship with, or financial interests in, any commercial companies pertaining to this educational activity. Lippincott CME Institute, Inc., has identified and resolved all faculty conflicts of interest regarding this educational activity. Visit the Critical Care Medicine Web Site (www.ccmjournal.org) for information on obtaining continuing medical education credit.

Epidemic carbon monoxide poisoning following a winter storm

Hospital emergency departments were surveyed to estimate the number of patients treated for carbon monoxide (CO) poisoning after a severe winter storm disrupted electrical service in western Washington State. At least 81 persons were treated. The two main sources of CO were charcoal briquettes (54% of cases) and gasoline-powered electrical generators (40% of cases). Of the 44 persons affected by CO from burning charcoal, 40 (91%) were members of ethnic minority groups; 27 did not speak English. All persons affected by CO from generators were non-Hispanic Whites. This was the largest epidemic of storm-related CO poisoning reported in the United States. This epidemic demonstrated the need to anticipate CO poisoning as a possible consequence of winter storms in cold climates and to make preventive messages understandable to the entire population at risk, including those persons who do not understand written or spoken English.

Hyperbaric Oxygen Therapy for Radiation-Induced Hemorrhagic Cystitis

From May 1988 through May 1991, 14 patients with radiation-induced hemorrhagic cystitis confirmed by cystoscopy and biopsy, who had failed all other attempts at management and who had no evidence of infection or recurrent malignancy, were treated with hyperbaric oxygen therapy. During followup ranging from 10 to 42 months 8 patients (57%) had complete resolution of symptoms and 2 (14%) had marked improvement, for a total of 10 patients (71%) with a positive outcome. Of 4 patients (29%) with a poor outcome 3 had limited improvement and were later diagnosed as having recurrent malignancy that was not present on biopsy before hyperbaric treatment. One patient was withdrawn from hyperbaric treatment due to illness. The average cost per patient was

Prospective assessment of outcomes in 411 patients treated with hyperbaric oxygen for chronic radiation tissue injury

10,000 to

Characteristics of Headache Associated With Acute Carbon Monoxide Poisoning

15,000, comparing favorably to the cost of multiple conservative treatments to control symptoms. Hyperbaric oxygen therapy for radiation-induced hemorrhagic cystitis appears to be an efficacious treatment modality for patients who have failed other forms of management.