med 18

 

MEDICAL DECISION MAKING

CO poisoning presents similar to many other conditions,

including migraine headaches, influenza-like illnesses,

acute gastroenteritis, vasovagal syncope, and cerebrovascular accident. Question patients about any possible expo ­

sures. Start supplemental 02 while obtaining confirmatory

studies. Send co-oximetry to measure the COHb level in

patients with concerning presentations and those with an

unexplained high anion gap metabolic acidosis. Consider

concurrent cyanide toxicity in the unconscious and hypotensive patient who was rescued from a house or industrial

fire. Rapidly exclude pregnancy with bedside urine testing,

as this will significantly impact management. Use the absolute COHb in combination with the patient's symptoms

to dictate further care including possible hyperbaric

oxygen (HBO) therapy (Figure 58-2).

TREATMENT

Treat concomitant injuries such as smoke inhalation, trauma,

myocardial injury, seizures, or neurologic deficits as you

would in any other setting. Supportive care in the form of

airway management, oxygen therapy, and intravenous fluids

remains the most important intervention. Normobaric 0 2 via

a nonrebreather facemask should be administered until the

COHb level is <5% and the patient is clinically stable. The

circulating half-life of CO is approximately 4--6 hours in

patients breathing room air, 90 minutes for those on 100% 02,

and approximately 20 minutes for those undergoing HBO

therapy. The absolute indications for HBO therapy are debatable, but it is generally indicated for those patients with significant exposures (Table 58-1). The true benefit of treatment

with HBO is most likely to limit the prevalence of delayed

neurologic symptoms. The only absolute contraindication to

HBO is an untreated pneumothorax. Because most hospitals

do not have hyperbaric chambers, contacting your regional

poison control center can be very helpful in the management

and disposition of these patients.

Check COHb level

Neurologic abnormal ity, loss 02 therapy via nonrebreather, consult poison

control center and/or

transfer for HBO chamber

No neurologic abnormal ity

Discharge home after

oxygen therapy and

asymptomatic

of consciousness, coma,

cardiovascular dysfunction,

severe acidosis, pregnancy,

intermittent exposure > 24 H

• Figure 58-2. Carbon monoxide poisoning diag nostic algorithm.

CHAPTER 58

Table 58-1 . Ind ications for hyperbaric 02 treatment in acute co poisoning.

Definite Indication

AMS and/or abnormal neurologic examination (if patient has normal

evaluation while on supplemental 0

2