Fire and ice: diagnosis of carbon monoxide poisoning in a remote environment.

Following an explosion on board a British Navy submarine operating under the Polar ice cap, a 33-year-old sailor fought a fire without protective breathing apparatus. He was found confused, with soot about his nares. A suspected diagnosis of carbon monoxide (CO) poisoning was rapidly confirmed on site using a new non-invasive pulse CO-oximeter. Initial carboxyhaemoglobin (COHb) level was 28%. He was treated with high-flow oxygen and evacuated to a medical facility with hyperbaric oxygen treatment capability. Fifteen other crew members potentially exposed to smoke in the enclosed space were screened in less than 10 min and had normal COHb levels of 1-2%. This is the first case demonstrating the utility of pulse CO oximetry for diagnosing CO poisoning in remote environments. The information obtained allowed immediate delivery of appropriate on-site treatment and directed subsequent triage. The device was also shown to be effective for the rapid screening of numerous individuals. Not only does it have the potential to provide information that would otherwise be unobtainable in such a situation, but it could play an important role in mass casualty screening.

Rate of delivery of hyperbaric oxygen treatments does not affect response in soft tissue radionecrosis.

BACKGROUND: Soft tissue radiation necrosis (STRN) is effectively treated with hyperbaric oxygen (HBO,), believed to result from stimulation ofangiogenesis in radiation-injured tissue. Thirty to forty HBO2 treatments are usually recommended for STRN. For various reasons, different hyperbaric facilities offer these treatments once or twice daily and from 5-7 days weekly. It is not known whether the clinical response differs as a result of the rate of administration of HBO2 treatments. METHODS: Details of hyperbaric treatment courses of patients treated for radiation enteritis/proctitis (n = 65) and cystitis (n = 94) at a single institution were reviewed. Outcomes were compared with the total number of HBO2 treatments administered and also rate of treatment administration. RESULTS: Responses were similar for both forms of STRN whether the patient averaged fewer or greater than 5 treatments per week, or even < or = 3 versus > or = 7 treatments weekly. Outcome did differ, however, dependant on the total number of treatments administered. Response was better in patients receiving 30 or more total treatments, as compared with fewer. CONCLUSIONS: Soft tissue radionecrosis of the gastrointestinal tract or bladder is (1) effectively treated with hyperbaric oxygen, (2) has a higher response rate if at least 30 treatments are administered, and (3) is equally responsive to rates of hyperbaric treatment ranging from 3 or fewer to 7 or more treatments per week.

Carbon monoxide poisoning: a new incidence for an old disease.

PURPOSE: While carbon monoxide (CO) poisoning is common in the USA, its incidence is uncertain. Fatal poisonings are counted with relative accuracy from death certificate data, but estimates of the more common nonfatal poisonings are either old or limited. This study was performed to estimate the number of emergency department (ED) visits annually in the USA for carbon monoxide poisoning. BASIC PROCEDURES: ED visit rates in five states (Idaho, Maine, Montana, Utah, and Washington) from three prior studies, each using different methodology, were used to extrapolate independent estimates of national ED visits. MAIN FINDINGS: After correcting for regional differences in CO poisoning incidence, estimates of national ED visits per year ranging from 32,413 to 56,037 were obtained. Excluding the estimate derived from the Maine rate because it did not include intentional and fire-related poisonings, the national average is 50,558 +/- 4,843 visits per year. CONCLUSIONS: There are approximately 50,000 ED visits for CO poisoning in the USA annually, 3-5 times the numbers previously estimated. As this disease can result in significant long-term morbidity even when treated, enhanced prevention efforts are warranted.

Treatment of gastrointestinal radiation injury with hyperbaric oxygen.

BACKGROUND: Chronic radiation enteritis develops in 5-20% of patients following abdominal and pelvic radiation. Current treatments are largely ineffective. OBJECTIVE: To assess the effectiveness of hyperbaric oxygen therapy (HBO2) as a treatment for chronic radiation enteritis and evaluate the relative effectiveness in treatment of the proximal and distal gastrointestinal tract. DESIGN: Case series of 65 consecutive patients with chronic radiation enteritis treated between July 1991 and June 2003 with HBO2. SETTING: A tertiary referral academic medical center. PATIENTS: 65 patients (37 male, 28 female; mean age 65 years) were treated with HBO2 for radiation damage to the alimentary tract. INTERVENTIONS: Patients were treated with an initial series of 30 daily treatments, each administering 90 minutes of 100% oxygen at 2.36 atmospheres absolute pressure. Thirty-two patients with partial symptom response or endoscopic evidence of healing received an additional 6 to 30 treatments. RESULTS: The primary indication for HBO2 was bleeding (n = 54) with 16 patients requiring transfusions. Additional indications were pain, diarrhea, weight loss, fistulas and obstruction. Follow-up ranged from 1 to 60 months (mean = 23 months). The main outcome measures were effects on bleeding, pain, diarrhea, weight loss, fistulas and obstruction. Endoscopic documentation of healing was used when available. The response rate was 68%, with a complete and partial response rate of 43 and 25%, respectively. The response rate for rectal disease was 65% and for proximal sites was 73%. The response rate for bleeding was 70% and for other symptoms was 58%. CONCLUSION: This series represents the largest clinical series reported using HBO2 for treatment of radiation injury to the GI tract. The findings suggest that HBO2 results in healing or clinically significant improvement in two thirds of patients with chronic radiation enteritis.

Storm-related carbon monoxide poisoning: lessons learned from recent epidemics.

Over the past 15 years, a number of epidemics of carbon monoxide (CO) poisoning related to various storms have been reported. While the geographical location of these outbreaks and the types of storms involved has been diverse, review of the events reveals a number of common factors and themes. This paper summarizes the details of 9 published reports describing CO poisoning associated with 11 different storms. When common patterns were examined, five "lessons to be learned" from the experience were derived. They are (1) loss of electrical power can lead indirectly to carbon monoxide poisoning, (2) campaigns to educate the public about risks for CO exposure should be timed regionally to coincide with the peak risk for typical storms, (3) significant opportunities exist for prevention of generator-related CO poisoning, (4) there is a window of time for effective communications regarding the dangers of CO poisoning even after a storm strikes, and (5) the major sources of CO responsible for poisonings can be related to the type of storm and are predictable. It is hoped that each of these lessons are used to develop public programs designed to prevent storm-associated CO poisoning in the future.

A prospective, randomized clinical trial comparing two hyperbaric treatment protocols for carbon monoxide poisoning.

INTRODUCTION: The optimal hyperbaric oxygen (HBO2) treatment protocol for acute carbon monoxide (CO) poisoning is unknown. This is indicated by one study that found 18 different protocols to treat CO poisoning by North American multiplace hyperbaric facilities. A pilot study was conducted to evaluate the feasibility of randomizing patients to different protocols and to determine whether any large differences in clinical outcome were present between the two most common protocols. METHODS: Adult patients with accidental CO poisoning resulting in transient loss of consciousness, presentation to the emergency department within 12 hours, primary language English, high school education, and residence within 100 miles of the hyperbaric facility were recruited. Enrolled patients were randomized to one HBO2 treatment at 2.4 atmospheres absolute (atm abs) pressure with 90 minutes of 100% oxygen breathing vs. treatment by the US Air Force CO protocol (3.0 atm abs maximum pressure). A neurocognitive screening test was performed immediately after hyperbaric treatment and repeated 14-21 days later. RESULTS: From 1995 to 2002, 30 patients age 21 to 88 years were randomized, 18 to treatment at 2.4 atm abs and 12 to 3.0 atm abs. Average carboxyhemoglobin level for the population was 24.8 +/- 8.8% (mean +/- SD). Delay to hyperbaric treatment averaged 313 +/- 129 minutes. Neither variable was different between treatment groups. Six patients had abnormal neurocognitive testing immediately following hyperbaric treatment, 4 in the 2.4 atm abs group (22%) and 2 in the 3.0 atm abs group (17%) (P=0.71). One patient in each group demonstrated abnormality on delayed testing (p=0.75). One in each group did not return for follow-up. CONCLUSIONS: It is feasible to randomize CO-poisoned patients to different hyperbaric treatment protocols. Determination of differences in efficacy between treatment protocols will require a large multicenter trial with the use of detailed neurocognitive testing.

Epidemiology of severe carbon monoxide poisoning in children.

OBJECTIVE: To describe the characteristics of severe pediatric CO poisoning cases treated with hyperbaric oxygen (HBO2) to determine key features that might aid prevention efforts. DESIGN: Using data on 250 consecutive children treated with HBO2 for CO poisoning at Virginia Mason Medical Center in Seattle, we calculated descriptive statistics and used Fisher's Exact test to determine differences in case frequency of CO sources with respect to race/ethnicity. RESULTS: There were 236 (94%) unintentional and 14 (6%) intentional poisonings. Loss of consciousness occurred in 50%. The average initial carboxyhemoglobin level was 19.0 +/- 10.3% (mean +/- SD; range 0.3% to 57.6%). Months with the highest proportion of incidents were November (15%), December (12%) and January (14%). Children 0-2 years old were most often poisoned by charcoal briquettes (40%), in contrast to older children who were most often poisoned by motor vehicle. Females were most often poisoned by charcoal briquettes (28%), in contrast to males in which motor vehicle exhaust predominated (41%). Minorities were disproportionately affected by CO poisoning compared with non-Latino whites (P < 0.001). Overall, motor vehicle exhaust predominated for Non-Latino whites (33%), while Non-Latino blacks (55%) and Latinos (71%) had significantly higher proportions of poisonings by charcoal briquettes (P < 0.001). All intentional cases occurred in adolescents aged 15 to 17 years, 71% of these in males, mostly by motor vehicle exhaust (79%). CONCLUSIONS: Severe pediatric CO poisoning demonstrates a seasonal pattern with key sources of exposure varying by gender, age, and race/ethnicity. Minorities are at increased risk for severe CO poisoning. Intentional CO poisoning occurs primarily among adolescent males and by motor vehicle exhaust. Prevention efforts should take these factors into consideration.

Hyperbaric treatment of patients with carbon monoxide poisoning in the United States.

INTRODUCTION: Hyperbaric oxygen (HBO2) is effective therapy for carbon monoxide (CO) poisoning. In recent years, many hyperbaric physicians in the US have felt that numbers of patients referred for treatment of CO poisoning have decreased. Further, since the 2002 Weaver et al study (5), there has been discussion regarding the best treatment protocol. This study was conducted to determine numbers of patients treated with HBO2 annually over the past decade in the US and whether there is a consensus about the number of treatments per patient. MATERIALS AND METHODS: A survey was mailed to all US facilities listed in the 2001 UHMS Chamber Directory. Two subsequent mailings were sent to survey nonresponders, followed by telephone contacts. RESULTS: Of the 320 facilities listed in the directory, 10 were nonresponders, 26 had closed since publication and 80 do not treat CO poisoning, leaving 204 facilities. From 1992-2002, a total of 16,367 patients were treated with HBO2 for CO poisoning, an average of 1,488 +/- 121 patients/year (mean < or = SD). While the total number of patients treated annually did not decrease during the period studied, the number treated per facility did decline as a result of an increase in number of treating facilities. Only 46 facilities (23%) automatically give more than 1 hyperbaric treatment per CO-poisoned patient. Among those that do, 20 facilities (10%) give 3 treatments per patient. Conversely, 136 (67%) sometimes give more than one treatment and 12 facilities (8%) never retreat. CONCLUSIONS: Approximately 1,500 CO-poisoned patients are treated with HBO2 in the US annually, a number that has remained relatively constant since 1992. The majority of facilities does not routinely give more than one hyperbaric treatment, but will give repetitive treatment in certain situations.

Hyperbaric oxygen treatment protocols for mandibular osteoradionecrosis.

To determine hyperbaric oxygen (HBO2) treatment practices for osteoradionecrosis (ORN) of the mandible in North America, we surveyed hyperbaric facilities listed in the 1998 UHMS Chamber Directory. A survey response rate of 99.7% was achieved. Among the 316 facilities listed, 280 treat or would treat mandibular ORN with HBO2. Twelve different hyperbaric treatment protocols for the condition were reported. Approximately three-quarters of facilities utilize a protocol administering 90 minutes of 100% oxygen breathing at a treatment pressure of 2.4-2.5 atmospheres absolute (atm abs). The remaining one-quarter of facilities apply alternate hyperbaric treatment protocols. In summary, mandibular ORN is commonly treated at North American hyperbaric facilities but there is a lack of uniformity with regard to the protocol utilized for hyperbaric oxygen administration. There are no clinical data to support that any one treatment protocol is superior in out come to any other.

A systematic review of the literature reporting the application of hyperbaric oxygen prevention and treatment of delayed radiation injuries: an evidence based approach.

The treatment of delayed radiation injuries (soft tissue and bony radiation necrosis) is one of thirteen conditions approved by the Hyperbaric Oxygen Therapy Committee of the Undersea and Hyperbaric Medical Society as appropriate indications for hyperbaric oxygen (HBO2). This paper provides a systematic review of the literature reporting the results of HBO2 therapy in the treatment and/or prophylaxis of delayed radiation injury. Since the introduction of the concept of evidence based medicine, the medical community in general has set out to apply more critical and stringent standards in evaluating published support for therapeutic interventions. Evidence based medicine is designed to discover the best evidence available and apply it in daily practice for treatment of the individual patient. The preferred level of evidence is the randomized controlled trial, however, other evidence has merit as well. In this review, seventy-four publications are represented reporting results of applying HBO2 in the treatment or prevention of radiation injuries. These are appraised in an evidence-based fashion by applying three established systems of evaluation. All but seven of these publications report a positive result when HBO2 is delivered as treatment for or prevention of delayed radiation injury. These results are particularly impressive in the context of alternative interventions. Without HBO2, treatment often requires radical surgical intervention, which is likely to result in complications. Other alternatives including drug therapies are rarely reported, and for the most part have not been the subject of randomized controlled trials. Based on this review, HBO2 is recommended for delayed radiation injuries for soft tissue and bony injuries of most sites. Of note, an increasing body of evidence supports HBO2 for radiation-induced necrosis of the brain. For other radiation-induced neurological injuries, additional study is required before recommendations for routine hyperbaric therapy can be made.

Diving methods and decompression sickness incidence of Miskito Indian underwater harvesters.

Diving conditions, dive profiles, and symptoms of decompression sickness (DCS) in a group of Miskito Indian underwater seafood harvesters are described. Dive profiles for 5 divers were recorded with dive computers, and DCS symptoms were assessed by neurological examination and interview. Divers averaged 10 dives a day over a 7-day period with a mean depth of 67 +/- 7 FSW (306 +/- 123 kPa) and average in-water time of 20.6 +/- 6.3 minutes. Limb pain was reported on 10 occasions during 35 man-days of diving. Symptoms were typically managed with analgesic medication rather than recompression. Indices of the decompression stress were estimated from the recorded profiles using a probabilistic model. We conclude that the dives were outside the limits of standard air decompression tables and that DCS symptoms were common. The high frequency of limb pain suggests the potential for dysbaric bone necrosis for these divers.

Outcome of patients experiencing cardiac arrest with carbon monoxide poisoning treated with hyperbaric oxygen.

STUDY OBJECTIVE: We sought to examine the outcome of a subgroup of patients with extreme carbon monoxide (CO) poisoning, specifically those discovered in cardiac arrest, resuscitated, and subsequently treated with hyperbaric oxygen (HBO(2)). Opinions of hyperbaric medicine physicians regarding the treatment of such patients were also sought. METHODS: Records of patients treated with HBO(2) for acute CO poisoning at Virginia Mason Medical Center in Seattle from September 1987 to August 2000 were reviewed. Those who were resuscitated from cardiac arrest in the field before HBO(2) treatment were selected for detailed analysis. Patient demographic data and information regarding circumstances of the poisoning, resuscitation, HBO(2) treatment, and subsequent course were extracted and collated. In addition, a postal survey of medical directors of North American HBO(2) treatment facilities regarding opinions about the management and outcome of such patients was performed. RESULTS: A total of 18 patients were treated with HBO(2) after resuscitation from CO-associated cardiac arrest. They included 10 female and 8 male patients ranging in age from 3 to 72 years. Sources of CO included house fires (10 patients) and automobile exhaust (8 patients). Patient carboxyhemoglobin levels averaged 31.7%+/-11.0% (mean+/-SD), and arterial pH averaged 7.14+/-0.19. Presenting cardiac rhythm was a bradydysrhythmia in 10 of 18 patients. HBO(2) treatment was administered an average of 4.3 hours after poisoning (< or = 3 hours in 10 patients and < or = 6 hours in 15 patients). Despite this, all 18 patients died during their hospitalizations. Medical directors of hyperbaric treatment facilities estimated a 74% likelihood of survival for a hypothetical patient with this presentation. CONCLUSION: In this consecutive case series, cardiac arrest complicating CO poisoning was uniformly fatal, despite administration of HBO(2) therapy after initial resuscitation. Survey results suggest that physician education regarding this subset of CO-poisoned patients is needed. The prognosis of this condition should be considered when making triage and treatment decisions for patients poisoned to this severity.

Carbon monoxide poisoning: interpretation of randomized clinical trials and unresolved treatment issues.

Since hyperbaric oxygen therapy (HBO2) appeared as a treatment for CO poisoning in 1960, whether and when to use it for CO poisoning have often been debated. HBO2 has been advocated to treat severe CO poisoning to limit delayed and permanent neurologic sequelae. Initially, inferences about efficacy were based on clinical experience and uncontrolled studies, but since1989, six prospective clinical trials have been reported comparing HBO2 and normobaric O2 administration to treat patients with acute CO poisoning. Of the six trials, four found better clinical outcomes among patients receiving HBO2 while two have shown no treatment effect. The most recent and best-designed randomized controlled clinical trial, performed in Salt Lake City, supports the efficacy of HBO2 in severe acute CO poisoning in accordance with scientific rationale and clinical experience. However, a number of important issues remain for future investigation, which could be addressed in a large multi-center trial. Such a trial should attempt to determine the optimal number of HBO2 treatments and the maximum treatment delay from CO poisoning for HBO2 to provide efficacy in patients with specific risk factors for a poor outcome.

Incidence of severe unintentional carbon monoxide poisoning differs across racial/ethnic categories.

OBJECTIVE: This study was conducted to test the hypothesis that the incidence of severe, acute, unintentional carbon monoxide (CO) poisoning differs across racial/ethnic categories. METHODS: The authors retrospectively reviewed medical records of all Washington State residents treated with hyperbaric oxygen for severe, acute, unintentional CO poisoning from December 1, 1987, through February 28, 1997. RESULTS: Among 586 Washington State residents treated with hyperbaric oxygen for severe, acute, unintentional CO poisoning, racial/ethnic designations could be determined from record review for 530 (90%). The black and Hispanic white populations of Washington State had higher relative risks for severe, acute, unintentional CO poisoning than the non-Hispanic white population. The most common sources of CO poisoning differed by racial/ethnic category. CONCLUSIONS: Members of certain groups in Washington State are at higher risk for severe, unintentional CO poisoning. Public education programs regarding CO exposure should be targeted to populations at risk.

Effects of weather on incidence of attempted suicide by carbon monoxide poisoning.

Depressive illness and related suicide attempts have been reported to have seasonal variation, possibly related to weather. This study sought to determine the effects of weather and time of year on suicide attempts by carbon monoxide (CO) poisoning. Cases of patients in western Washington State attempting suicide by CO poisoning and referred to a regional hyperbaric oxygen treatment center from 1981-1995 were reviewed retrospectively. Information from the National Climatic Data Center was used to compare date of treatment to local weather data on the day of attempted suicide and on each day of the preceding week. The study population consisted of 264 patients attempting suicide by CO poisoning on 251 days of the 15-yr period. Mean and total precipitation in the preceding 7 days strongly correlated with attempted suicide rate, with incident rate ratios ranging from 1.75 to 2.77 and 1.14 to 1.75, respectively (P values <0.05). A decrease in minimum daily temperature also correlated with attempted suicide rate. No other weather variables showed significant correlation with dates of CO suicide attempts. February, March, and October were seen to be separate factors related to a higher incidence of attempted suicide by CO poisoning. Precipitation in Seattle, change in minimum temperature, and month of the year correlated with the regional incidence of suicide attempts with CO poisoning.

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.