IS THE PULSE OXIMETRY LYING ON LYING (DOWN)?

Case Presentation: INTRODUCTION:Hepatopulmonary syndrome (HPS) is a complication seen in 4-7% of patients with chronic liver disease. The definitive treatment for HPS is liver transplantation (LT). A high index of suspicion is required to diagnose HPS. We present a perplexing case of HPS presenting with just hypoxia and orthodeoxia in the setting of liver disease.CASE REPORT:A 62-year-old female, nonsmoker with a history of alcoholic cirrhosis, (MELD score 15, Child Pugh’s Score 7), hemochromatosis, and idiopathic hypoxia for a year requiring 3 liters of nocturnal oxygen, presented with worsening dyspnea for two weeks. She endorsed orthostatic dizziness and baseline chronic productive cough. Nocturnal oximetry done a month earlier had revealed significant hypoxia to 95% of the time on room air.On presentation, she was hemodynamically stable. Her SpO2 was 80% on room air (RA) when sitting. While supine, it improved to 86% on RA and to 91% on high flow. The physical exam was unremarkable. A chest CT showed bibasilar atelectasis with patchy adjacent ground glass changes and mild splenomegaly. Labs revealed thrombocytopenia of 54,000, total bilirubin 2.1, direct bilirubin 0.9, AST 111. ABG on RA demonstrated PaO2 of 56 mm Hg with an A-a gradient of 44.She was admitted to the Pulmonary Care Unit, where she continued to desaturate, requiring high flow oxygen continuously. Urinalysis was negative. Vasculitis workup including.. was negative. A TTE with a bubble study was consistent with an extracardiac shunt. A 99mTc scan showed mild global uptake in both kidneys and brain consistent with a right to left shunt. An ABG with a shunt study showed a 27% shunt fraction. She was diagnosed with severe HPS and transferred for LT evaluation.

Discussion: Orthodeoxia refers to a decrease in PaO2 by more than 4 mmHg or SpO2 by more than 5% when the patient moves from a supine to an upright position.This is a common feature in HPS which improved when the patient returns to a recumbent position. Patients with severe HPS, as in our case, require long term oxygen therapy and transplant evaluation. Based on observational studies, LT has resulted in resolution of HPS in nearly 80% of patients within 6-12 months post-transplant. Patients with HPS awaiting LT had a mean PaO2 decline of 5.2 ∓ 2.3 mmHg/year. The 5-year survival in HPS patients associated with LT was 76% versus 23% for patients without transplantation. Based on these studies, transplant societies have recommended expedited referrals for LT and MELD score exceptions.

Conclusions: Orthodeoxia, detected by pulse oximetry, can result in the early diagnosis of HPS, thus aiding in reducing mortality associated with delayed transplant evaluation. Clinicians should have a high index of suspicion for this rare yet important sign.