Doctor123.org

Carbon Monoxide Poisoning, Emergency Medicine

Basics

Description

- Methylene chloride: - Found in some solvents for paint removal and furniture stripping - Converted in vivo to CO after exposure - Peak carboxyhemoglobin levels delayed after exposure - Half-life is ~2 times that of inhaled CO

- CNS: - Acute encephalopathy - Seizures - Coma

- Cardiovascular: - Tachycardia - Premature ventricular contractions - Dysrhythmias - Myocardial ischemia/infarction

- Respiratory: - Tachypnea - Noncardiogenic pulmonary edema

- Ophthalmologic: - Other: - Respiratory alkalosis - Rhabdomyolysis - Lactic acidosis

- History: - Maintain a high index of suspicion - Symptoms may be mild, nonspecific - Inquire about the following: - Similar symptoms in other household members - Malfunctioning furnaces - Use of space heaters, open ovens for supplemental heat - Ill pets

- Arterial blood gas: - Normal PaO2 - Normal calculated O2 saturation - Low measured O2 saturation - Metabolic acidosis in severe cases

- Chest radiography: - CT scan of the head: - To evaluate for intracranial causes of altered mental status when indicated - Bilateral globus pallidus low-density lesions may be clue to CO poisoning in unclear cases.

- Benefits: - May reduce delayed neurologic sequelae - Decreases half-life of carboxyhemoglobin

- Use of hyperbaric O2 remains controversial - Indications for consulting hyperbaracist: - Altered mental status/coma - Focal neurologic deficits - Seizures - Cardiovascular compromise (infarction, persistent dysrhythmia) - Persistent metabolic acidosis - Carboxyhemoglobin level >25% - Pregnancy with carboxyhemoglobin level >10%

  • Carbon monoxide (CO) is a colorless, odorless, nonirritating gas.
  • Binds to hemoglobin to form carboxyhemoglobin:Decreases O2-carrying capacity
  • Direct cellular toxin
  • Impairs cellular O2 utilization

Etiology

  • Endogenous:Result of normal metabolism
  • Incomplete combustion of carbonaceous fossil fuel:Internal combustion enginesNatural gasHeatersIndoor grillsFireplacesFurnacesAccidental firesTobacco smoke
  • Methylene chloride:Found in some solvents for paint removal and furniture strippingConverted in vivo to CO after exposurePeak carboxyhemoglobin levels delayed after exposureHalf-life is ~2 times that of inhaled CO

Diagnosis

Signs and Symptoms

History

  • CNS:HeadacheDizzinessAtaxiaConfusionSyncopeSeizures
  • GI:
  • Cardiovascular:
  • Respiratory:
  • Ophthalmologic:

Physical Exam

  • CNS:Acute encephalopathySeizuresComa
  • Cardiovascular:TachycardiaPremature ventricular contractionsDysrhythmiasMyocardial ischemia/infarction
  • Respiratory:TachypneaNoncardiogenic pulmonary edema
  • Ophthalmologic:
  • Other:Respiratory alkalosisRhabdomyolysisLactic acidosis

Essential Workup

  • History:Maintain a high index of suspicionSymptoms may be mild, nonspecificInquire about the following:Similar symptoms in other household membersMalfunctioning furnacesUse of space heaters, open ovens for supplemental heatIll pets
  • Arterial blood gas:Normal PaO2Normal calculated O2 saturationLow measured O2 saturationMetabolic acidosis in severe cases
  • Carboxyhemoglobin level:Measure as soon as possibleLevel may not reflect clinical severity:Patient may be critically ill despite unimpressive carboxyhemoglobin level.May be misleadingly low if significant time has passed since exposureNormal range is 0-3% (up to 10% in smokers).

Diagnosis Tests & Interpretation

Lab

  • Pulse oximetry:Falsely elevated SaO2 readingPulse oximeter cannot distinguish oxyhemoglobin from carboxyhemoglobin.
  • Electrolytes:Metabolic acidosis and elevated anion gap associated with increased clinical severity
  • Cardiac enzymes:When myocardial ischemia/infarction suspected
  • Pregnancy test
  • ECG:CO may precipitate myocardial ischemia/infarction.DysrhythmiasNonspecific ST-segment and T-wave abnormalities

Imaging

  • Chest radiography:
  • CT scan of the head:To evaluate for intracranial causes of altered mental status when indicatedBilateral globus pallidus low-density lesions may be clue to CO poisoning in unclear cases.

Differential Diagnosis

  • Viral illness/viral syndrome
  • Meningitis/encephalitis
  • Intracranial hemorrhage
  • Gastroenteritis
  • Migraine headache
  • Tension headache
  • Ethanol intoxication
  • Sedative-hypnotic overdose
  • Cyanide poisoning
  • Salicylate overdose
  • Toxic alcohol exposure

Treatment

Pre-Hospital

Administer 100% O2

Initial Stabilization/Therapy

  • ABCs
  • Establish IV access
  • 100% oxygen
  • Cardiac monitor

Ed Treatment/Procedures

  • Oxygen:Administer 100% normobaric O2:Via face mask or endotracheal tubeContinue O2 therapy until carboxyhemoglobin level <10%.Half-life of carboxyhemoglobin:~300 min in ambient air~90 min in 100% normobaric O2~20 min at 3 atm (hyperbaric O2)
  • Hyperbaric O2:Dose:100% O2 at 3 atmMay be repeatedBenefits:May reduce delayed neurologic sequelaeDecreases half-life of carboxyhemoglobinPotential adverse effects:Tympanic membrane rupturePneumothoraxSeizureDecompression sicknessPulmonary edemaUse of hyperbaric O2 remains controversialIndications for consulting hyperbaracist:Altered mental status/comaFocal neurologic deficitsSeizuresCardiovascular compromise (infarction, persistent dysrhythmia)Persistent metabolic acidosisCarboxyhemoglobin level >25%Pregnancy with carboxyhemoglobin level >10%
  • Fetal hemoglobin has higher affinity for CO than adult hemoglobin.
  • Fetal carboxyhemoglobin levels 10-15% higher than maternal levels
  • Delayed clearance of fetal carboxyhemoglobin compared with maternal

Follow-Up

Disposition

Admission Criteria

  • Persistent symptoms after 4 hr of treatment with 100% oxygen
  • Evidence of myocardial ischemia or cardiac instability
  • Seizures
  • Persistent metabolic acidosis
  • Syncope

Discharge Criteria

  • Asymptomatic after 4 hr of observation
  • Absence of aforementioned admission criteria
  • Psychiatric clearance if suicidal exposure

Issues for Referral

Need for hyperbaric oxygen therapy

Followup Recommendations

Contact local fire department in cases of CO home exposures.

Pearls and Pitfalls

  • Suspect CO poisoning in patients who present with headaches when home heaters are initiated.
  • Suspect CO poisoning when family members living in the same enclosed space have similar symptoms.
  • Administer 100% O2 and transfer to hyperbaric facility if the above-described criteria is met.

Additional Reading

  • Buckley NA, Juurlink DN, Isbister G, et al. Hyperbaric oxygen for carbon monoxide poisoning. Cochrane Database Syst Rev. 2011;13(4):CD002041.
  • Guzman JA. Carbon monoxide poisoning. Crit Care Clin. 2012;28(4):537-548.
  • Kao LW, Nanagas KA. Carbon monoxide poisoning. Emerg Med Clin North Am. 2004;22(4):985-1018.
  • Weaver LK. Carbon monoxide poisoning. N Engl J Med. 2009;360:1217-1225.

See Also (Topic, Algorithm, Electronic Media Element)

Hyperbaric Oxygen

Codes

ICD9

986 Toxic effect of carbon monoxide

ICD10

  • T58.11XA Toxic effect of carb monx from utility gas, acc, init
  • T58.91XA Toxic effect of carb monx from unsp source, acc, init
  • T58.92XA Toxic effect of carb monx from unsp source, self-harm, init
  • T58.94XA Toxic effect of carb monx from unsp source, undet, init
  • T58.8X1A Toxic effect of carb monx from oth source, accidental, init

SNOMED

  • 17383000 Toxic effect of carbon monoxide (disorder)
  • 95873000 carbon monoxide poisoning from faulty furnace AND/OR heater (disorder)
  • 420057003 Accidental poisoning by carbon monoxide
  • 242840004 Self poisoning by carbon monoxide (disorder)
  • 95872005 Carbon monoxide poisoning from motor vehicle exhaust