A Silent Death

OBJECTIVES

• Review the incidence and sources of carbon monoxide poisoning, including increased risk following natural disasters
• Review the pathophysiology, symptoms and assessment of CO poisoning, including the use of newer monitors to measure carboxyhemoglobin in the field.
• Highlight steps to be taken to ensure rescuer safety.
• Discuss management strategies for victims of CO poisoning, including the use of hyperbaric oxygen.

 The death earlier this year of a Texas EMT student sleeping in an EMS station is a tragic reminder that carbon monoxide's nickname, "silent killer," is all too accurate. Carbon monoxide (CO) knows no racial, ethnic, gender or geographic boundaries, and rescuers and citizens alike are at risk.

   According to investigators, Casey Steenland and two coworkers became victims when a small generator onboard their ambulance was left running after the vehicle was parked inside the building.¹ Since the facility's heating, hot water and stove were all electric, a carbon monoxide detector had not been installed. Steenland's exposure was fatal; her two coworkers were later released from the hospital after hyperbaric oxygen treatments. A third EMT was also treated at the hospital for CO exposure during the rescue of the initial victims.

Incidence and Sources

   Carbon monoxide poisoning is one of the leading causes of accidental poisoning death in the United States. It contributes to a minimum of 40,000 emergency department visits and 500 unintentional deaths annually. There are an additional 4,500-5,000 intentional (suicide) carbon monoxide poisoning deaths each year.² As the symptoms are often vague and attributed to other ailments such as the flu, many experts believe that an additional 11,000 cases per year are undetected or misdiagnosed.

   Smoke inhalation in structure fires is the leading source of unintentional carbon monoxide exposures.² Likewise, CO poisoning is the leading cause of death of fire victims, not the thermal injuries many would suspect. Dangerous carbon monoxide sources include portable generators, automobiles, boats, furnaces, water heaters, household stoves, camping lanterns and stoves, snow blowers, floor buffers, pumps, power sprayers, lawn mowers and garden tractors. It is important for EMS professionals to consider these or look for potential CO sources as part of their scene assessment. The Centers for Disease Control and Prevention (CDC) and the Consumer Product Safety Commission (CPSC) both have in-depth information about spotting potential CO sources. (See https://www.cdc.gov/co and www.cpsc.gov/cpscpub/pubs/464.pdf.)

   Not unlike the mechanism of injury in trauma calls, EMTs and paramedics may be the only members of the healthcare team who have the opportunity to recognize these clues. The literature contains a number of case studies of patients who were seen in the ED for vague, flu-like symptoms, then discharged and unwittingly sent back to the source of the carbon monoxide. Sadly, these stories typically end with near-fatal or fatal exposures. An observant prehospital professional can help prevent that scenario.

Disasters

   One particular setting where EMS professionals have an opportunity to educate the public and prevent CO poisoning is in severe weather or natural disaster emergencies. There is a significant increase in CO cases when electrical service is disrupted after events like hurricanes, wind storms, blizzards and ice storms. One study of nine different storms over a 15-year period documented 930 CO poisonings with a total of 23 fatalities.³ An interesting variety of causes were noted. During a 1996 winter storm in the northeastern part of the U.S., 25 motorists suffered CO poisoning when their vehicles were stranded in deep snow. They kept their cars running, not realizing that the snow was obstructing the exhaust systems and returning dangerous fumes to the passenger compartment.

   The loss of electricity after a winter storm will lead people to use just about anything they can find to heat their homes. Storm victims use propane and kerosene heaters inside buildings without proper venting, and a surprising number have burned charcoal briquettes inside to stay warm or cook food. Victims have also been known to use gas stoves and open ovens as heat sources, not knowing that they too can produce CO, especially older or poorly functioning units.

   The common source of carbon monoxide after natural disasters is the portable generator. Storm victims need power for fans, air conditioning or heating devices, lights, computers, televisions and refrigerators. Unaware of the danger, storm victims have been observed running generators inside their homes, including in the basement or outside the building close to windows, doors, air conditioners or other vents that draw the fumes in. Attached garages, breezeways and decks are other common but equally unsafe locations for running generators.

Pathophysiology

   To help prevent carbon monoxide poisonings and treat them when they do occur, it is important to understand how CO acts as a poison. We have known for years that carbon monoxide creates a functional hypoxia in the bloodstream, where available binding spaces for the transport of oxygen to cells are not available. We know that the CO molecule has an affinity to hemoglobin (the molecule that carries oxygen in the bloodstream) of 230-270 times that of oxygen. Even when a small concentration of CO is in the air and inhaled into the lungs, it is quickly attached to the hemoglobin-forming carboxyhemoglobin. When this occurs, the oxygen molecules that are already bound to other sites on the hemoglobin become more tightly bound (leftward shift of the oxyhemoglobin dissociation curve). This contributes to the hypoxia, as the oxygen then cannot be "offloaded" at the tissue site. The organs most sensitive to oxygen flow, such as the brain and heart, are most susceptible.⁴

   Carbon monoxide also directly damages tissues at the cellular level. The toxin binds to cellular mitochondria and stimulates an inflammatory process whose severity often does not match the observed blood concentration of CO.⁵ The inflammation is also suspected to play a role in the neurologic decline commonly noticed weeks to months after exposure.⁶

   Carbon monoxide also has significant and long-term effects on the heart and the patient's subsequent mortality.

   It has a depressive effect on the myocardial tissue resulting in decreased cardiac output and a shock state, which further worsens systemic tissue hypoxia.⁴

   Dr. Birgul Yelken of Osmangazi University in Turkey demonstrated in 2009 that CO can lead to abnormal myocardial wall motion and a lowered ventricular fibrillation threshold, as well as other arrhythmias such as atrial flutter, atrial fibrillation, premature ventricular contractions and other conduction system disturbances.⁷ QT intervals (measurement of the time it takes for both ventricles to contract and repolarize) may also be prolonged with increasing carboxyhemoglobin (HgCO).⁷ All CO poisoning patients should be placed on an EKG monitor, and paramedics should avoid administering any medications that may prolong the QT interval such as haloperidol (Haldol), procainamide (Pronestyl), ziprasidone (Geodon) and ondansetron (Zofran).

   A study in 2006 showed that even patients with a previous low-risk profile for cardiovascular disease had a 37% chance of myocardial injury when they sustained a moderate to severe CO exposure. Thirty-eight percent of patients who had damage died within eight years.⁸ This is concerning information, highlighting the need to better screen for CO exposure in patients, rescuers and firefighters.

Signs and Symptoms

   One aspect of carbon monoxide poisoning that makes it a "silent killer" is that the symptoms are often vague and may be discounted as other illnesses like the flu. Many patients do not realize they are having symptoms or delay seeking help until it is too late. A common scenario is that patients go to bed thinking they have food poisoning or are coming down with a cold or flu, only to continue to be exposed to the toxic gas and die in their sleep.

   Evidence indicates that the brain is the organ most sensitive to changes in oxygenation. Accordingly, neurological symptoms such as headache, dizziness, lethargy and confusion are usually the first seen in patients exposed to low levels of CO. As the exposure continues or the concentration of gas is increased, patients will experience nausea, dyspnea, blurred vision, fatigue and agitation. The level of consciousness continues to decline, and patients eventually slip into a coma and then death. See Table I for a complete list of symptoms.

   There are no physical assessment signs of CO poisoning, although a thorough primary and secondary are certainly still needed to rule out any trauma or medical sources of the symptoms. Especially when the patient has confusion or lethargy, he/she cannot be trusted to report injuries or other symptoms. Although widely reported in stories and training scenarios, the cherry red skin color of carbon monoxide poisoning is rarely seen and is more likely only noted in fatalities.⁴

   Pulse oximetry in this setting should be used with caution. Standard pulse oximeters ignore hemoglobin containing CO, thus showing a normal to high SpO₂ percentage. Without an understanding of CO poisoning, the EMT would misinterpret this as the patient being well-oxygenated and delay or forego important CO poisoning treatment. Even when CO exposure is suspected, SpO₂ measurement should still be used to rule out conditions that might present with a low SpO₂.

Carboxyhemoglobin Assessment

   Specific devices are now available for measuring the level of carboxyhemoglobin in the blood. Hospital laboratories can measure HgCO by testing a sample of arterial or venous blood. Carboxyhemoglobin levels do not necessarily correlate with patients' conditions or their prognosis.⁹ Low levels of HgCO do not rule out a significant exposure, especially if the patient has already been receiving 100% oxygen by mask.

   Although exhaled breath analyzers have been available for several years, they are not popular in the EMS setting, as they typically require both a cooperative patient to follow the testing procedure and regular calibration. A newer device called a pulse CO-oximeter allows immediate HgCO measurement in the field. The Masimo RAD-57 is the only prehospital pulse CO-oximeter approved by the FDA at this time. The unit functions similarly to a standard pulse oximeter and gives an accurate estimate of the patient's HgCO.¹⁰ The CO-oximeter only requires placement of a sensor on the patient's finger. The same unit provides SpO₂ and CO, and can provide methemoglobin measurement if so configured.

   Emergency departments are beginning to use pulse CO-oximeters to screen all patients for carbon monoxide poisoning. After implementing the devices at an emergency department in Rhode Island, triage nurses identified several patients who might otherwise not have had CO poisoning pinpointed as the cause of their complaints.¹¹

   Recognizing the increased risk of CO poisoning to citizens and rescuers, the Federal Emergency Management Agency (FEMA) has added the RAD-57 to the required equipment lists of each of its Urban Search and Rescue (USAR) task forces.¹² USAR teams respond to a wide variety of natural and man-made disasters and often work in confined or poorly ventilated spaces. The hydrocarbon-powered tools they use to stabilize scenes and to locate and extricate victims create a risk of CO exposure. And, as described earlier, the patients rescue crews encounter may also be victims of CO. Early assessment of HgCO in these patients is very helpful in preventing ongoing poisoning, and in triage and management of limited medical resources.

   In 2003, the National Fire Protection Association (NFPA) issued recommendations for firefighter rehabilitation. NFPA 1584 became a standard in 2008, setting the stage for required and recommended aspects of rehab on fire scenes and during training.¹³ Assessment of carbon monoxide exposure is considered a recommended vital sign in the medical monitoring portion of the standard. To help their fire districts comply with the standard, the state of Delaware recently purchased 150 Masimo RAD-57 pulse CO-oximeters and deployed them to each fire department in the state.¹⁴ The units will be used to assess citizen victims, as well as to monitor firefighters and other responders.

   While the pulse CO-oximeter can provide an accurate reading of the patient's current HgCO, rescuers are reminded that there may be no correlation between the reading and patients' symptoms, much less their prognosis. Table 2 denotes an estimation of how symptoms progress as HgCO increases. Keeping in mind that smokers may have a baseline reading of 10%, any patient with an elevated HgCO reading should be transported to a hospital for a more thorough assessment.

Management and Rescuer Safety

   Management of suspected or confirmed CO poisoning begins with removal of the patient from the source. Immediate evacuation of the victim and all personnel from the area, especially if it is an enclosed space, is critical.

   A recent event in central Wisconsin highlights the importance of rescuer safety. Phillip is a paramedic with an ambulance service that does ALS intercepts with area BLS responders. One cool spring morning, Phillip and his partner were called to assist a BLS crew at the scene of a cardiac arrest. The young patient was found in bed at home in full arrest by someone who came to meet him that morning. After terminating the resuscitation on scene, a few of the EMTs and the person who found the cardiac arrest victim suddenly became ill. Two passed out briefly, while others complained of headache, dizziness and nausea. The home was immediately evacuated and oxygen treatment was started on those experiencing symptoms thought to be from acute carbon monoxide exposure. In all, six rescuers and one citizen were treated and transported to a local ED for assessment and definitive care. Luckily, no one required transport to a hyperbaric oxygen facility, but a few were hospitalized overnight. Phillip and his partner were monitored in the ED for a few hours while being kept on high-flow oxygen and having their HgCO levels rechecked. Assessment of the home revealed a faulty furnace producing high levels of CO throughout the dwelling.

   Many services now carry personal gas detectors that can alert rescuers to dangerous gases, such as carbon monoxide or hydrogen sulfide, or decreased levels of oxygen in the air. The devices are regularly used in the manufacturing industry, as well as hazmat operations, and can be configured to monitor one or multiple hazards. The units are clipped to jump bags or carried on the belt or pocket by EMS professionals.

   As in the central Wisconsin case, after evacuation, the next step in management is to apply oxygen via non-rebreather mask at 15 liters per minute. On room air, the half-life of carbon monoxide is four hours. In other words, it takes four hours to reduce the HgCO percentage by half. With 100% oxygen, the half-life is decreased to 90 minutes; if the patient is treated with hyperbaric oxygen, the time is reduced to 15 to 20 minutes.¹⁵

   While oxygen therapy is being administered, support the patient's ABCs as needed. If breathing support is required, ventilate at a normal rate and volume. Do not hyperventilate or hypoventilate, as this may change the pH of the blood and potentiate problems with oxygen loading and unloading. Provide supportive care and manage other signs or symptoms like seizures per local protocol.

   Before leaving any scene with a definite or suspected case of CO poisoning, EMS crews should ensure that the building is being evacuated of all humans and a fire crew has arrived at the scene, is fully briefed that carbon monoxide is suspected, and should be in position to evaluate the source of the gas.

Hyperbaric Oxygen

   The use of hyperbaric oxygen (HBO) for treatment of CO poisoning remains controversial. A PubMed literature search yields a long list of HBO studies both supporting and casting doubt on the use of this therapy. The American College of Emergency Physicians did a comprehensive review of the literature and in 2008 published a clinical policy for emergency physicians guiding their use of HBO.¹⁶ The policy lists HBO as a therapeutic option for CO-poisoned patients, but stops short of recommending its use. The group also attempted to define a subset of patients, signs, symptoms or HgCO levels that should lead a physician to consider HBO treatment, but were unable to find sufficient evidence from which to draw such a list. Accordingly, EMS providers are likely to see wide variation in the use of HBO and should not assume that any particular patient will or will not require HBO treatment. Be familiar with your protocols, especially if you have a hyperbaric chamber in your area. Contact online medical control if you are considering bypassing a closer hospital in favor of a hospital that provides HBO.

   When transporting by ground ambulance, consider traveling nonemergently if the patient's vital signs are stable. There is no evidence that the few minutes saved will make a difference in the patient's long-term outcome.

Documentation

   As with all EMS calls, an important part of the patient's care is documentation of the circumstances and events leading up to 9-1-1 being called. In the case of CO poisoning, it is helpful to note:

• Source of the CO
• Duration of exposure
• Location of the source
• Location of the patient and relation to the source
• That the source is being managed and further poisonings are being averted
• Ambient air CO readings, including whether any ventilation of the room or building has been done prior to reading.

   This information may be helpful in determining definitive treatment, as well as assisting agencies such as the CDC or CPSC to do research and work to prevent future poisonings.

Conclusion

   When the tragic and unnecessary death of EMT Steenland made headlines across the industry, did your service take a moment to make sure your facilities are monitored by CO detectors? Will you learn from the responders in Wisconsin and carry personal gas detectors? Both of these pieces of equipment are inexpensive, easy to use and critical for responder safety. Once on scene, be aware of potential sources of CO and the subtle symptoms with which a patient may present. Early detection will not only minimize the severity of the exposure, but it could save the patient's life, along with other family members and rescuers.

Public Education Opportunities

EMS providers have an important opportunity to educate the public on carbon monoxide poisoning prevention year-round, as well as during natural disaster emergencies. Important messages may include:

• Every home should have at least one functioning carbon monoxide detector. More may be necessary, depending on the size and layout of the home.
• If letting a vehicle idle to warm up in cold weather, make sure it is outside and the garage door is closed so CO does not flow back into the garage.
• Place generators a minimum of 15 to 25 feet from the home and away from windows, doors, vents and air conditioners. Never run a generator indoors.
• Do not use propane, kerosene or charcoal briquettes to cook or heat indoors, in tents or in campers.
• Do not leave stove-top burners on or oven doors open to heat a room.

The CDC and CPSC each have lines of educational materials available, including on CO awareness while boating, camping, in the home and during times of natural disaster. The availability of these materials, plus our close ties to the response to and care of CO poisoning victims, makes it a good opportunity for a public education project.

Public Education Opportunities

EMS providers have an important opportunity to educate the public on carbon monoxide poisoning prevention year-round, as well as during natural disaster emergencies. Important messages may include:

• Every home should have at least one functioning carbon monoxide detector. More may be necessary, depending on the size and layout of the home.
• If letting a vehicle idle to warm up in cold weather, make sure it is outside and the garage door is closed so CO does not flow back into the garage.
• Place generators a minimum of 15 to 25 feet from the home and away from windows, doors, vents and air conditioners. Never run a generator indoors.
• Do not use propane, kerosene or charcoal briquettes to cook or heat indoors, in tents or campers.
• Do not leave stove-top burners on or oven doors open to heat a room.
• The CDC and CPSC each have lines of educational materials available, including CO awareness while boating, camping, in the home and during times of natural disaster. The availability of these materials, plus our close ties to the response to and care of CO poisoning victims, makes it a good opportunity for a public education project.

REFERENCES

1. EMT identified in fatal Texas carbon monoxide exposure. The Associated Press/ El Paso Times (Texas). www.emsresponder.com/article/article.jsp?siteSection=1&id=14335.

2. Reinisch CE. Carbon monoxide poisoning: Implications for patient and family care in the emergency department. Clinical Scholars Review 1(1), 2008.

3. Hampson NB, Stock AL. Storm-related carbon monoxide poisoning: Lessons learned from recent epidemics. Undersea Hyperb Med 33(4):257-263, 2006.

4. Toxicity, Carbon Monoxide. https://emedicine.medscape.com/article/819987.

5. Balch C. Carbon monoxide poisoning: Too easily overlooked. Nursing 34(5), 32cc10-2, 2004.

6. Neubauer RA, Neubauer V, et al. Treatment of late neurologic sequelae of carbon monoxide poisoning with hyperbaric oxygenation: A case series. J Amer Phys Surg 11(2): Summer 2006.

7. Yelken B, Tanriverdi B, Cetinbas F, et al. The assessment of QT intervals in acute carbon monoxide poisoning. Anadolu Kardiyoloji Dergisi/Anatolian Journal of Cardiology 9(5):397-400, 2009.

8. Henry CR, Satran D, Lindgren B, et al. Myocardial injury and long-term mortality following moderate to severe carbon monoxide poisoning. JAMA 295:398-402, 2006.

9. Weaver L. Clinical practice. Carbon monoxide poisoning. N Engl J Med 360(12):1217-1225, 2009.

10. Coulange M, Barthelemy A, Hug F, et al. Reliability of new pulse CO-oximeter in victims of carbon monoxide poisoning. Undersea Hyperb Med 35(2):107-111, 2008.

11. Chee K, Nilson D, Partridge R, et al. Finding needles in a haystack: A case series of carbon monoxide poisoning detected using new technology in the emergency department. Clinical Toxicology 46(5):461-469, 2008.

12. FEMA Adds Masimo Rad-57 Pulse CO-Oximeter to Required Medical Equipment List. www.masimo.com/news/2009.htm#2776.

13. McEvoy M. The elephant on the fireground: Secrets of NFPA 1584-compliant rehab. www.fireengineering.com/index/articles/display.articles.fire-engineering.volume-161.issue-8.features.the-elephant-on-the-fireground-secrets-of-nfpa-1584-compliant-rehab.html.

14. Delaware Becomes the First to Equip Every Fire District in the State with Most Advanced Noninvasive Carbon Monoxide Screening Technology. www.masimo.com/news/index.cfm#3042

15. Pollack AN, FAAOS, Series Editor. Nancy Caroline's Emergency Care in the Streets, 6th Ed. Sudbury, MA: Jones and Bartlett, 2008.

16. Wolf SJ, Lavonas EJ, Sloan EP, Jagoda AS. American College of Emergency Physicians. Clinical policy: Critical issues in the management of adult patients presenting to the emergency department with acute carbon monoxide poisoning. Ann Emerg Med 51(2):138-152, Feb 2008.

This CE activity is approved by EMS World Magazine, an organization accredited by the Continuing Education Coordinating Board for Emergency Medical Services (CECBEMS), for 1.5 CEUs. To earn your credits, go to www.rapidce.com, or to print and mail a copy, download the test here.

   Michael Fraley, BS, NREMT-P, is coordinator of the North Central (Wisconsin) Regional Trauma Advisory Council, EMS coordinator for Portage County (Wisconsin) EMS and affiliate faculty for PHTLS. He has also worked as a flight paramedic, EMS service manager and assisted living facility owner/ administrator. E-mail fraleym@charter.net.