CC: Altered level of consciousness

HPI: 40 year old male presents by EMS after being found down at his home by a neighbor. The patient was last seen by his wife about 36 hours prior to presentation. The patient is unable to recall any events leading to his emergency department visit. His wife of 20 years states that they are having marital trouble, but the patient has no psychiatric history, no history of drug and alcohol abuse, and his only medical history is chronic back pain.

PE: Vital Signs – blood pressure 151/90, heart rate 108, respiratory rate 25, oxygen saturation 96% on a non-rebreather oxygen mask, temperature 37.8 degrees Celsius. Eyes – pupils briskly reactive bilaterally. Respiratory – lungs clear to auscultation with good respiratory effort. Cardiac – tachycardic, 2+ distal pulses throughout. Neuro – 4/5 strength of bilateral elbow flexion/extension, 4+/5 strength of bilateral hip flexion and knee flexion/extension. Psychiatric – alert and oriented to person/place/time, poor insight to current condition, normal affect.

Lab: CPK – >32,000. UDS – positive for barbiturates and TCAs. Negative for alcohol, acetaminophen, and aspirin. BUN/creatinine – 33/1.3.

Imaging: see the attached image.

Answer(s): 1) Bilateral globus pallidus hypodensities. 2) Carbon monoxide poisoning.

Discussion: This patient was thought to have attempted suicide. He was found to be minimally responsive in his garage with the vents taped closed and his head lying next to a gas powered generator. His carboxyhemoglobin was only 2.5% (1.5% is the upper limit of normal for a non-smoker). Although this is elevated, it is thought that the carboxyhemoglobin was significantly higher prior to presentation given that he had been down for a significant period of time, he had received oxygen therapy while in transport and he had bilateral globus pallidus lesions on CT.

The half life of carbon monoxide is 3-4 hours while breathing room air and 60 minutes while breathing 100% oxygen. The patient was on 100% oxygen for 4 hours prior to his carboxyhemoglobin level. This would estimate his carboxyhemoglobin at 20%. He was also down for an unknown period of time breathing room air which could implicate even higher levels of carboxyhemoglobin.

Basal ganglia lesions should be evident within 12 hours of carbon monoxide exposures that result in a loss of consciousness. These lesions are associated with poor outcomes.

Take Home Points • Carbon monoxide poisoning should be diagnosed by history, physical, and carboxyhemoglobin levels. • Neuroimaging can support the diagnosis of carbon monoxide poisoning and rule out other causes of altered mental status. • Initial treatment of carbon monoxide exposures should be 100% oxygen.

References Hoffman RS, et al. Goldfrank’s Manual of Toxicologic Emergencies, 8th ed. New York: McGraw-Hill; 2007. Tintinalli JE, Kelen GD, Stapczynski JS, Emergency Medicine: A Comprehensive Study Guide, 6th ed. New York: McGraw-Hill; 2004.