What is the best next step for a patient with a headache after working in a closed garage?

Immediate Supplemental Oxygen Administration

The best next step is immediate administration of supplemental oxygen, as this patient's clinical presentation—headache after working in a closed garage with mild confusion (GCS 14)—is highly suggestive of carbon monoxide poisoning, which requires urgent oxygen therapy to prevent serious morbidity and mortality.

Clinical Reasoning

Recognition of Carbon Monoxide Poisoning

• The history of working in a closed garage with gradual onset bitemporal headache and altered mental status (confusion, GCS 14) is pathognomonic for carbon monoxide (CO) exposure 1
• CO poisoning is a life-threatening emergency that can rapidly progress to severe neurological injury, cardiac complications, and death if not treated immediately 2
• The mild confusion already indicates significant CO toxicity affecting cerebral function, making this a time-critical intervention 1

Why Oxygen is the Priority

• High-flow supplemental oxygen (ideally 100% via non-rebreather mask) is the definitive initial treatment for CO poisoning, as it accelerates the elimination of CO from hemoglobin and tissues 3
• The half-life of carboxyhemoglobin is approximately 4-6 hours on room air but reduces to 40-80 minutes with 100% oxygen 3
• Oxygen should be administered immediately while awaiting confirmatory carboxyhemoglobin levels—treatment should never be delayed for diagnostic testing 3
• Current evidence supports titrating oxygen to maintain SpO2 >92%, though in suspected CO poisoning, maximal oxygen delivery is indicated regardless of pulse oximetry readings, as standard pulse oximeters cannot distinguish oxyhemoglobin from carboxyhemoglobin 3

Why Other Options Are Inappropriate

CT of the sinuses is not indicated as this patient has no signs of sinusitis (no facial pain, purulent discharge, or fever pattern consistent with sinus infection) and the exposure history clearly points to CO poisoning 1, 2

Lumbar puncture would be dangerous and inappropriate—there are no signs of meningitis (only mild fever at 99.4°F, no severe neck stiffness, no photophobia), and the exposure history explains the presentation without needing CSF analysis 1, 4

Sumatriptan administration would be a critical error—while this patient has a headache, the clinical context (closed garage, confusion) indicates a secondary headache from CO poisoning, not migraine 5, 2. Triptans are contraindicated in secondary headaches and could delay life-saving treatment 5

Critical Management Steps

Immediate Actions

• Administer 100% oxygen via non-rebreather mask at 15 L/min immediately 3
• Obtain carboxyhemoglobin level, complete blood count, metabolic panel, troponin, and ECG (CO can cause cardiac ischemia) 2
• Continue oxygen therapy for minimum 4-6 hours or until carboxyhemoglobin level <5% and symptoms resolve 3

Common Pitfalls to Avoid

• Do not rely on pulse oximetry alone—SpO2 may appear normal (as in this case at 98%) because standard pulse oximeters cannot differentiate carboxyhemoglobin from oxyhemoglobin 3
• Do not wait for confirmatory testing before initiating oxygen therapy—treatment must begin immediately based on clinical suspicion 3
• Do not treat as primary headache (migraine, tension-type) when exposure history suggests secondary cause 1, 2

Disposition Considerations

• Consider hyperbaric oxygen therapy if carboxyhemoglobin >25%, persistent neurological symptoms, cardiac ischemia, pregnancy, or loss of consciousness 3
• Admit for observation and serial neurological assessments, as delayed neuropsychiatric sequelae can occur in 10-30% of patients even after initial recovery 2