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Carbon Monoxide Poisoning
2019 Case Definition

NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

CSTE Position Statement(s)

  • 18-EH-01

Background

Carbon monoxide (CO) is a colorless, odorless, nonirritating gas that is produced through the incomplete combustion of carbon-containing substances. Sources of CO include: boilers: furnaces, cars and trucks, generators and other gasoline or diesel-powered engines, gas and propane heaters, woodstoves, gas stoves, fireplaces, tobacco smoke, forklifts, and fires. The most common location of exposures causing CO poisoning are in homes and less commonly in workplaces. CO poisoning occurs from breathing in elevated air levels of carbon monoxide. Unusual sources include exposure to methylene chloride, which is metabolized to CO and hemolysis, with increased metabolism of hemoglobin. Symptoms are generally non-specific and commonly include headache, dizziness, weakness, vomiting, chest pain and confusion. Large exposures can result in loss of consciousness, arrhythmias, seizures, or death. Unintentional, non-fire related CO poisoning is responsible for approximately 450 deaths and 21,000 emergency department (ED) visits each year.1,2,3 CO poisoning is a leading cause of unintentional poisoning deaths in the United States.2 Outbreaks of CO poisoning associated with equipment used during natural disasters have been well documented.4-8

For surveillance purposes, Tier 1 reporting refers to the process of healthcare providers or institutions (e.g., clinicians, clinical laboratories, hospitals, poison control centers) submitting basic information to governmental public health agencies about cases of carbon monoxide poisoning that meet certain reporting requirements or criteria. Cases of carbon monoxide poisoning may also be ascertained by the secondary analysis of administrative data or through syndromic surveillance algorithms where individual information is available for follow-up case investigation. Tier 2 surveillance for carbon monoxide poisoning is based upon secondary analysis of administrative data without access to personal identifiers.

Clinical Criteria

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

Presumptive clinical evidence:
  • Loss of consciousness OR
  • Death
Supportive clinical evidence:
  • A person with signs or symptoms consistent with carbon monoxide poisoning, which may include elevated pulse Carbon Monoxide (CO)-oximetry measurement and/or non-specific symptoms such as nausea, vomiting, confusion, shortness of breath, and chest pain.

Laboratory Criteria for Diagnosis

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

Confirmatory laboratory evidence:
A person who does not smoke, or a child (age < 14 years) whose smoking status is unknown, and has a carboxyhemoglobin (COHb) level of ≥ 5.0% as measured in a blood sample 9-11 OR

A person who smokes, or a person (age ≥ 14 years) whose smoking status is unknown, with a carboxyhemoglobin (COHb) level of > 12.0% as measured in a blood sample10-11

Presumptive laboratory evidence:
A person who smokes, or whose smoking status is unknown (age ≥ 14 years), and has a carboxyhemoglobin (COHb) level of ≥ 9.0% and ≤ 12.0% as measured in a blood sample

Supportive laboratory evidence:
A person who does not smoke, or a child (age < 14 years) whose smoking status is unknown, and has a carboxyhemoglobin (COHb) level of ≥ 2.5% and < 5.0% as measured in a blood sample12 OR

A person who smokes, or whose smoking status is unknown (age ≥ 14 years), and has a carboxyhemoglobin (COHb) level of ≥ 7.0% and < 9.0% as measured in a blood sample11

Epidemiologic Linkage

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

A person who was present and exposed in the same CO exposure event as that of a confirmed CO poisoning case.

Criteria to Distinguish a New Case from an Existing Case

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

A case should be categorized as a new (incident) case when there is either:
  • New exposure to CO from different exposure source
  • OR
  • Repeated exposure as defined by having the same exposure source as previous occurrence where the criteria used to designate a case has been resolved prior to repeat exposure

A case is categorized as a prevalent case when there are multiple reports for the same person for the same episode, such as when there are multiple COHb lab test results or when a patient receives multiple hyperbaric treatments following a single poisoning event.

Exposure

Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation):

Confirmatory exposure evidence*:
A person who had an exposure to an elevated level of CO based on a dedicated or multi-gas meter/instrument (e.g., fire department notation) for a known duration that is consistent with CO poisoning.

Possible exposure evidence*:

  • A person who was in a location where a CO detector's alarm sounded, OR
  • A person who had onset of CO-related symptoms associated physically and temporally with a CO-emitting source (e.g., gasoline-powered generator, power washer, malfunctioning furnace, and fire)

*Note: Exposure evidence that is provided by the patient is sufficient for meeting exposure evidence criteria.

Case Classification

Suspected

  • A person with supportive laboratory evidence OR
  • A person with supportive clinical criteria AND possible exposure evidence

Probable

  • A person with presumptive laboratory evidence* OR
  • A person with presumptive clinical evidence AND possible exposure evidence, OR
  • A person with presumptive or supportive clinical evidence AND epidemiologic linkage

*Other plausible clinical explanations should be considered, including chronic obstructive lung disease and hemolysis.

Confirmed

  • A person with confirmatory laboratory evidence* OR
  • A person with presumptive or supportive clinical evidence AND with confirmatory exposure evidence

* Other plausible clinical explanations should be considered, including chronic obstructive lung disease and hemolysis.

Other Criteria

Tier 2 (Using secondary analysis of administrative data without access to personal identifiers):

Suspected:

Poison Control Center Records:
A person whose poison control center record indicates an exposure to carbon monoxide AND a minor medical outcome (see Appendix 3 )

Workers compensation records:
A person whose workers compensation submitted claim contains a finding, problem, diagnosis, or other indication of exposure to carbon monoxide or carbon monoxide poisoning (see Appendix 4 ).

Healthcare records, including hospital discharge and emergency department records:

  • A person whose healthcare record contains a diagnosis that is inclusive of carbon monoxide poisoning by sources other than motor vehicle exhaust (see Appendix 2).
  • A person whose emergency department record mentions exposure to carbon monoxide in the chief complaint.

Death Certificates:
A person whose death certificate lists a cause of death that is inclusive of carbon monoxide poisoning, toxic effect of carbon monoxide, or carbon monoxide exposure as a cause of death or a significant condition contributing to death (see Appendix 5) .

Probable:

Healthcare records, including hospital discharge and emergency department records:
A person whose healthcare record contains a diagnosis of carbon monoxide poisoning by motor vehicle exhaust (see Appendix 2 )

Poison Control Center Records:
A person whose poison control center record indicates an exposure to carbon monoxide AND a moderate medical outcome, major medical outcome, or death (see Appendix 3 )

Workers compensation records:
A person whose workers compensation paid claim contains a finding, problem, diagnosis, or other indication of exposure to carbon monoxide or carbon monoxide poisoning (see Appendix 4 ).

Confirmed:

Healthcare records, including hospital discharge and emergency department records:
A person whose healthcare record contains an explicit diagnosis of carbon monoxide poisoning (see Appendix 2 )

Death Certificates:
A person whose death certificate explicitly lists carbon monoxide poisoning, toxic effect of carbon monoxide, or carbon monoxide exposure as a cause of death or a significant condition contributing to death (see Appendix 5 ).

Case Classification Comments

The Case Classification section above refers to Tier 1 (Criteria using clinical, laboratory, epidemiologic, and exposure data from traditional public health surveillance practice based on case identification and follow-up investigation).

Reference(s)

  1. Centers for Disease Control and Prevention (CDC). Nonfatal, unintentional, non--fire-related carbon monoxide exposures--United States, 2004-2006. MMWR Morb Mortal Wkly Rep. 2008 Aug 22;57(33):896-9.
  2. Centers for Disease Control and Prevention (CDC). Carbon monoxide--related deaths--United States, 1999-2004. MMWR Morb Mortal Wkly Rep. 2007 Dec 21;56(50):1309-12.
  3. Centers for Disease Control and Prevention (CDC). Carbon monoxide exposures--United States, 2000-2009. MMWR Morb Mortal Wkly Rep. 2011 Aug 5;60(30):1014-7.
  4. Centers for Disease Control and Prevention (CDC). Monitoring poison control center data to detect health hazards during hurricane season--Florida, 2003-2005. MMWR Morb Mortal Wkly Rep. 2006 Apr 21;55(15):426-8.
  5. Lutterloh EC, Iqbal S, Clower JH, Spiller HA, Riggs MA, Sugg TJ, Humbaugh KE, Cadwell BL, Thoroughman DA. Carbon monoxide poisoning after an ice storm in Kentucky, 2009. Public Health Rep. 2011 May-Jun;126 Suppl 1:108-15.
  6. Centers for Disease Control and Prevention (CDC). Carbon monoxide exposures after hurricane Ike - Texas, September 2008. MMWR Morb Mortal Wkly Rep. 2009 Aug 14;58(31):845-9.
  7. Centers for Disease Control and Prevention (CDC). Notes from the field: carbon monoxide exposures reported to poison centers and related to hurricane Sandy - Northeastern United States, 2012. MMWR Morb Mortal Wkly Rep. 2012 Nov 9;61(44):905.
  8. Schier JG. Poison Control Centers and Toxicosurveillance: Real-time National Surveillance for Outbreaks of Chemical-Associated Illness. Presented May 2008 to CDC Emergency Preparedness & Response COCA conference call.
  9. Hampson NB, Piantadosi CA, Thom SR, Weaver LK. Practice recommendations in the diagnosis, management, and prevention of carbon monoxide poisoning. Am J Respir Crit Care Med. 2012 Dec 1;186(11):1095-101.
  10. Belson MG, Schier JG, Patel MM; CDC. Case definitions for chemical poisoning. MMWR Recomm Rep. 2005 Jan 14;54(RR-1):1-24.
  11. Aker J. Carboxyhemoglobin levels in banked blood: A comparison of cigarette smokers and non-smokers. AANA Journal 1987; 55:421-426.
  12. Peterson JE, Stewart RD. Predicting the carboxyhemoglobin levels resulting from carbon monoxide exposures. J Appl Physiol. 1975 Oct;39(4):633-8.


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