Another perspective on ACEP policy on critical issues in carbon monoxide poisoning: Invited commentary.

The American College of Emergency Physicians (ACEP) recently published its official policy on the evaluation and management of patients with acute carbon monoxide (CO) poisoning [1], an update of the policy previously published in 2008. Three questions regarding CO poisoning were posed to a 30-person ACEP subcommittee, which employed a comprehensive literature review to attempt to draw conclusions. While this is a major step forward, we feel that their conclusions warrant comment.

Comparison of normobaric vs. hyperbaric oxygen in the relief of carbon monoxide headache pain.

BACKGROUND: Headache is the most common symptom in carbon monoxide (CO) poisoning. While the mechanism of CO-induced headache is not well defined, it is felt that cerebral vasodilation plays a role. Clinical experience has demonstrated oxygen breathing is effective in resolving CO headache. However, the effectiveness of normobaric oxygen has never been compared to hyperbaric oxygen in this regard. METHODS: A 2016 paper by Ocak, et al. reported the response of CO headache pain severity to four hours of normobaric oxygen breathing in 82 patients using a 0-10 analog scale. The demographics, carboxyhemoglobin levels and response to therapy from that report were compared to data obtained by Hampson, et al. in an earlier study, but never published, using the same pain assessment method in 73 patients with CO headache and treated with hyperbaric oxygen. RESULTS: Comparing the normobaric and hyperbaric groups, neither average age nor presenting carboxyhemoglobin levels were significantly different. Baseline pain intensity scores were 6.5 ± 3.1 vs. 6.2 ± 2.6 (p=0.444) and post-treatment scores 1.5 ± 2.6 vs. 1.0 ± 1.5 (p=0.184) respectively on a 0-10 scale. CONCLUSIONS: In these two well-matched populations of patients with CO-induced headache pain, degree of resolution was not significantly different between normobaric and hyperbaric oxygen treatment.

Hyperbaric oxygen therapy for late radiation tissue injury.

BACKGROUND: Cancer is a significant global health problem. Radiotherapy is a treatment for many cancers and about 50% of people having radiotherapy will be long-term survivors. Some will experience late radiation tissue injury (LRTI) developing months or years later. Hyperbaric oxygen therapy (HBOT) has been suggested as a treatment for LRTI based upon the ability to improve the blood supply to these tissues. It is postulated that HBOT may result in both healing of tissues and the prevention of problems following surgery. OBJECTIVES: To assess the benefits and harms of HBOT for treating or preventing LRTI. SEARCH METHODS: We updated the searches of the Cochrane Central Register of Controlled Trials (CENTRAL; 2015, Issue 11), MEDLINE, EMBASE, DORCTIHM and reference lists of articles in December 2015. We also searched for ongoing trials at clinicaltrials.gov. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing the effect of HBOT versus no HBOT on LRTI prevention or healing. DATA COLLECTION AND ANALYSIS: Three review authors independently evaluated the quality of the relevant trials using the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions and extracted the data from the included trials. MAIN RESULTS: Fourteen trials contributed to this review (753 participants). There was some moderate quality evidence that HBOT was more likely to achieve mucosal coverage with osteoradionecrosis (ORN) (risk ratio (RR) 1.3; 95% confidence interval (CI) 1.1 to 1.6, P value = 0.003, number needed to treat for an additional beneficial outcome (NNTB) 5; 246 participants, 3 studies). There was also moderate quality evidence of a significantly improved chance of wound breakdown without HBOT following operative treatment for ORN (RR 4.2; 95% CI 1.1 to 16.8, P value = 0.04, NNTB 4; 264 participants, 2 studies). From single studies there was a significantly increased chance of improvement or cure following HBOT for radiation proctitis (RR 1.72; 95% CI 1.0 to 2.9, P value = 0.04, NNTB 5), and following both surgical flaps (RR 8.7; 95% CI 2.7 to 27.5, P value = 0.0002, NNTB 4) and hemimandibulectomy (RR 1.4; 95% CI 1.1 to 1.8, P value = 0.001, NNTB 5). There was also a significantly improved probability of healing irradiated tooth sockets following dental extraction (RR 1.4; 95% CI 1.1 to 1.7, P value = 0.009, NNTB 4).There was no evidence of benefit in clinical outcomes with established radiation injury to neural tissue, and no randomised data reported on the use of HBOT to treat other manifestations of LRTI. These trials did not report adverse events. AUTHORS' CONCLUSIONS: These small trials suggest that for people with LRTI affecting tissues of the head, neck, anus and rectum, HBOT is associated with improved outcome. HBOT also appears to reduce the chance of ORN following tooth extraction in an irradiated field. There was no such evidence of any important clinical effect on neurological tissues. The application of HBOT to selected participants and tissues may be justified. Further research is required to establish the optimum participant selection and timing of any therapy. An economic evaluation should be undertaken.

Suicidal carbon monoxide poisoning has decreased with controls on automobile emissions.

BACKGROUND: Highway vehicle CO emissions have decreased 85% since introduction of the catalytic converter in 1975. We sought to examine whether morbidity and mortality from intentional motor vehicle-related CO poisoning have also changed. METHODS: Vehicle CO emissions data from 1970-2013 were obtained from the U.S. Environmental Protection Agency. U.S. Centers for Disease Control and Prevention data were used for the suicide crude death rate (CDR) from CO poisoning from 1999-2010. Data on non-fatal intentional CO poisonings treated at a regional hyperbaric treatment center from 1981-2013 were analyzed with regard to numbers treated and presenting carboxyhemoglobin (COHb) levels. RESULTS: Since 1985, the CDR for suicidal motor vehicle-related CO poisoning has decreased in parallel with CO emissions (R2 = 0.985). Non-fatal motor vehicle-related intentional CO poisoning cases decreased 63% over 33 years (p = 0.0017). COHb levels decreased 35% in these patients (p < 0.0001). CONCLUSIONS: There has been a decrease in both fatal and non-fatal intentional CO poisoning from motor vehicle exhaust since the 1980s. This correlates with reductions in vehicle CO emissions and is a likely result of the U.S. Clean Air Act of 1970 and the application of catalytic converters since 1975.

Toxic CO-ingestions in intentional carbon monoxide poisoning.

BACKGROUND: Intentional carbon monoxide (CO) poisoning is responsible for two-thirds of the deaths from CO poisoning in this country and an estimated 15,000 Emergency Department visits annually. OBJECTIVES: In an attempt to optimize medical management of such patients, this study was conducted to examine the frequency and types of toxic co-ingestions that may accompany CO inhalation. METHODS: Records of all patients treated with hyperbaric oxygen for acute, intentional CO poisoning at a regional referral center for hyperbaric medicine in Seattle from 1980 to 2005 were reviewed. For those where co-ingestions were identified, information about type of poison(s) and results of toxicology screens was recorded and analyzed. RESULTS: Over the 25-year period examined, 433 patients were treated for intentional CO poisoning and records were available for 426. Of those, 188 (42%) had ingested one or more poisons in addition to CO. Ethanol was most common, but a wide variety of other drug classes were also identified. Toxicology screening studies of some type were performed in 49 patients. CONCLUSIONS: Toxic co-ingestions seem to be relatively common in patients treated for intentional CO poisoning. For this reason, providers should be vigilant and open to clinical signs that can't be explained with CO exposure alone, and ready to treat clinical issues that arise from co-ingestions.

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.

Partnering with a medical specialty society to perform online public health surveillance.

While accidental carbon monoxide (CO) poisoning is common, it is felt to be largely preventable through targeted public education. Development of effective education programs requires accurate epidemiologic information about the condition. Many acute, severe cases of CO poisoning are treated with hyperbaric oxygen (HBO2) at hospital-based facilities staffed by members of the Undersea and Hyperbaric Medical Society (UHMS). In 2008, the Centers for Disease Control and Prevention (CDC) began sponsoring a UHMS proposal to use online reporting by UHMS members of cases treated with HBO2. This report describes development and implementation of the internet-based surveillance system, as well as its first year of operation. From August 2008 to July 2009, a total of 740 cases were reported by the 82 hyperbaric facilities participating nationwide. Extensive epidemiologic information about CO poisoning in the United States has been collected, and the utility of partnering with a medical specialty society for disease-specific surveillance demonstrated.

Symptoms of carbon monoxide poisoning do not correlate with the initial carboxyhemoglobin level.

BACKGROUND: Symptoms in carbon monoxide (CO) poisoned patients have traditionally been described as being related to corresponding carboxyhemoglobin (COHb) levels without substantive support for the relationship. This study sought to determine whether prospectively collected symptoms correlate with specific COHB level ranges in a large population of CO-poisoned patients. METHODS: Data from patients reported in the initial two years of operation of the joint UHMS/CDC CO Poisoning Surveillance System were used to compare presenting COHb levels with symptoms collected with a standardized questionnaire. RESULTS: Data from 1,323 CO-poisoned patients referred for hyperbaric oxygen therapy from August 2008 to July 2010 were analyzed with regard to initial COHb level and symptoms. Of approximately 50 categories of symptoms reported, none was associated with a specific range of COHb levels. CONCLUSIONS: While symptoms are common in acute CO poisoning, none can be directly correlated to COHb levels, even in a population of more than 1,000 patients. The concept of a table relating specific symptoms to specific COHb levels is invalid. One such table that has often been published comes from a 1923 U.S. government publication and appears to be based at least in part upon the symptoms experienced by three men in a total of 10 low-level laboratory CO exposures.

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

BACKGROUND: Although hyperbaric oxygen is used to treat chronic radiation tissue injury, clinical evidence supporting its efficacy has been limited to date. The authors report prospectively collected patient outcomes from a single center's large experience using hyperbaric oxygen to treat chronic radiation injury. METHODS: Since 2002, patient outcomes at the conclusion of a course of hyperbaric oxygen treatment for chronic radiation tissue injury at Virginia Mason Medical Center in Seattle have been graded by a board-certified hyperbaric physician and prospectively recorded. From 2002 to 2010, a total of 525 patients received treatment for 1 of 6 forms of radionecrosis analyzed. After excluding 114 patients for incomplete records or treatment courses or for previous receipt of hyperbaric oxygen therapy, records of 411 patients were retrospectively reviewed in 2010, and outcomes were regraded by a second board-certified physician. A positive clinical response was defined as an outcome graded as either "resolved" (90%-100% improved) or "significantly improved" (50%-89% improved). RESULTS: A positive outcome from hyperbaric treatment occurred in 94% of patients with osteoradionecrosis of the jaw (n = 43), 76% of patients with cutaneous radionecrosis that caused open wounds (n = 58), 82% of patients with laryngeal radionecrosis (n = 27), 89% of patients with radiation cystitis (n = 44), 63% of patients with gastrointestinal radionecrosis (n = 73), and 100% of patients who were treated in conjunction with oral surgery in a previously irradiated jaw (n = 166). CONCLUSIONS: The outcomes of 411 patients collected prospectively over 8 years strongly supported the efficacy of hyperbaric oxygen treatment for the 6 conditions evaluated. The response rates previously reported in numerous small series were supported by the responses achieved in this large, single-center experience.

Recipients of hyperbaric oxygen treatment for carbon monoxide poisoning and exposure circumstances.

BACKGROUND: Unintentional carbon monoxide poisoning is preventable. Severe cases are often referred for hyperbaric oxygen treatment. To guide prevention efforts and treatment practices, this study provides some of the most detailed current information about patients with carbon monoxide poisoning who have been treated at hyperbaric facilities across the United States and the circumstances surrounding their exposures. This study can help improve efforts to prevent carbon monoxide poisoning and enhance treatment practices. METHODS: From August 2008 to January 2010, nonidentifiable, patient-level data were reported by 87 hyperbaric facilities in 39 states via an online reporting system. This reporting system was developed collaboratively by the Undersea and Hyperbaric Medical Society and the Centers for Disease Control and Prevention. RESULTS: Among the 864 patients reported to receive hyperbaric oxygen treatment for unintentional, non-fire-related, carbon monoxide poisoning, most of the patients were white men aged between 18 and 44 years. Only 10% of patients reported the presence of a carbon monoxide alarm at their exposure location, and 75% reported being part of a group exposure. Nineteen patients (2%) reported a prior carbon monoxide exposure. About half (55%) of the patients treated were discharged after treatment; 41% were hospitalized. CONCLUSIONS: The findings in this report expand the knowledge about patients with carbon monoxide poisoning. These results suggest that prevention efforts, such as educating the public about using carbon monoxide alarms and targeting the most at-risk populations, may help reduce the number of exposures, the number of persons with chronic cognitive sequelae, and the resulting burden on the health care system.

Increased long-term mortality among survivors of acute carbon monoxide poisoning.

OBJECTIVE: Recent data suggest that patients surviving acute carbon monoxide (CO) poisoning (COP) may have increased risk for long-term mortality. The objective of this study was to analyze long-term mortality of a large population of CO-poisoned patients treated at one medical center over three decades. DESIGN: Retrospective cohort study of patients treated with hyperbaric oxygen and surviving the acute poisoning episode. Long-term mortality was compared to a standard population. Comparison of mortality within the cohort by clinical indicators of poisoning severity was assessed using Cox proportional hazards regression analysis. SETTING: Regional referral center for hyperbaric treatment of COP. PATIENTS: One thousand seventy-three patients aged >or=18 years treated from 1978 to 2005. INTERVENTIONS: All patients received hyperbaric oxygen treatment. MEASUREMENTS AND MAIN RESULTS: During 11,741 person-years of follow-up, 162 subjects died. The expected number of deaths was 87 (standardized mortality ratio [SMR]), 1.9; 95% confidence interval [CI], 1.6-2.2). Most of the excess mortality was in the group treated initially for intentional COP (58 excess deaths; SMR, 3.7; 95% CI, 2.9-4.6) vs. those treated for accidental COP (17 excess deaths; SMR, 1.3; 95% CI, 1.01-1.6). For the entire cohort, the major causes of death with significantly raised mortality were mental and psychiatric disorders, injuries, and violence. More specific causes of death with significantly raised mortality were alcoholism, motor vehicle accidents with pedestrians, motor vehicle accidents of unspecified type, accidental poisonings, and intentional self-harm. Within cohort comparisons showed that no difference in survival was observed by measure of CO poisoning severity, after controlling for age at poisoning, sex, race, and intent of CO poisoning. CONCLUSIONS: Adult survivors of acute CO poisoning treated with hyperbaric oxygen were at increased risk for long-term mortality. Such patients should be followed closely after discharge with consideration given to psychiatric and/or neurocognitive evaluation, as appropriate.