PC3062: Comfortably Hypoxic: A Surprise Diagnosis

Introduction: Hypoxia is a secondary symptom of an underlying primary condition. It can be straightforward to treat but makes most people uncomfortable when the etiology isn't clear cut. This case walks through diagnostic dead ends that can come about when faced with the comfortably hypoxic patient.

Case Description: 3 year old vaccinated male, previously term, with no chronic medical problems presented with hypoxia in the setting of 4 days of fever, cough, and congestion. Upon initial evaluation, patient's SPO2 was 85% on room air without distress. Exam benign with exception of clubbing noted on fingers and toes. Escalation of respiratory support did not elevated SPO2, including use of nasal cannula, non-rebreather, and high flow nasal cannula. Lab workup demonstrated an elevated carbon monoxide level. Attempted 100% FIO2 washout without success in reversing hypoxia. Viral panel positive for non-COVID-19 coronavirus. Despite later normalization of HbCO levels, comfortable hypoxia continued.

Ultimately, patient admitted to Pediatric ICU for hypoxic respiratory failure. Airway clearance was maximized and patient underwent septic workup with initiation of broad spectrum antibiotics. Chest xrays repeatedly were unrevealing. While patient continually needed increasing respiratory support, he lacked obvious signs of respiratory distress. Echocardiogram was performed and normal, thus ruling out cardiac shunt physiology. Pulmonary medicine recommended outpatient follow up as they believed imaging while acutely ill would not elucidate a chronic diagnosis. Soon thereafter, patient required BiPAP trial and then intubation with initiation of nitric oxide to achieve adequate saturations. CT angiogram of the chest performed after intubation and showed evidence of multiple pulmonary AVMs. Pulmonary AVMs were treated with embolization and coiling procedures and patient able to be weaned gradually off respiratory support.

Discussion: This case demonstrates the importance of history and physical exam, in addition to the mindset of "leaving no rock unturned." Clubbing noted on exam demonstrated a chronic underlying problem likely contributing to this patient's known acute viral infection. The history did not confirm the initial suspicion of carbon monoxide poisoning which placed this lower on the differential diagnoses, especially when HbCO normalized. When all typical measures had been taken to evaluate and treat, the CT angiogram of the chest revealed the underlying chronic condition that was signaled from the physical exam. The pulmonary AVMs acting like vascular shunts were the etiology of the unexplained comfortable hypoxia. This was later exacerbated by VQ mismatch in the setting of viral infection.

Conclusion: Patients will tell you with their history and physical where to start your investigation for what may seem like a simple symptom from a simple diagnosis. But learning that there is more than meets the eye for conditions such as hypoxia will allow providers to "leave no rock unturned" in these challenging presentations.