Hepatopulmonary Syndrome (HPS)

Quantify the shunt before the case - Room-air ABG for PaO2 and A-a gradient. A pulse oximetry saturation under 96% is a positive screen (it corresponds to a PaO2 under 70 mmHg) and earns the ABG.

Know where the shunt sits - Contrast echocardiography with agitated saline is the gold standard. Bubbles reaching the left atrium at 4-6 cardiac cycles means intrapulmonary dilatation; arrival within 1-3 cycles means an intracardiac shunt such as a PFO or ASD. The two need different plans.

Oxygen only goes so far - A true anatomic shunt responds minimally to raising FiO2. If 100% barely moves the saturation, that is the shunt, not a ventilator problem — do not chase it with escalating airway pressures.

Position drives the saturation - Orthodeoxia is the signature finding: upright posture sends more flow to the dilated basal vessels and the saturation falls. Recheck the pulse oximeter after every position change, and especially after sitting the patient up for a neuraxial block.

Do not count on HPV - Dilated vessels have reduced tone and respond poorly to alveolar hypoxia, so hypoxic pulmonary vasoconstriction will not redistribute flow for you. That matters most in one-lung ventilation.

De-air every line - A right-to-left intrapulmonary shunt is exactly what lets agitated-saline microbubbles reach the left atrium. Bubbles in an IV line take the same route to the brain and coronaries.

Separate HPS from portopulmonary hypertension - HPS is a vasodilated, low-resistance lung; portopulmonary hypertension is vasoconstricted with elevated mean PA pressure and high PVR. Same cirrhotic patient, opposite hemodynamic plan — get the echo numbers before you commit.

Transplant is the only cure - Liver transplantation reverses the hypoxemia over 6-12 months, and HPS earns MELD exception points to get there. Perioperative mortality after transplant runs 8-16%, and a pretransplant PaO2 of 50 mmHg or less marks a substantially higher-risk patient.

Expect a low DLCO - Pulmonary function testing shows reduced diffusing capacity for carbon monoxide. It is a diffusion and shunt problem, not obstructive lung disease, and bronchodilators will not fix it.

The cirrhosis comes with it - INR, platelet count, varices, ascites, and encephalopathy all still apply. HPS is a complication of portal hypertension, not a substitute for the rest of the liver workup.

Hepatopulmonary syndrome (HPS) is the triad of liver disease or portal hypertension, an oxygenation defect (PaO2 under 80 mmHg, or an alveolar-arterial gradient of 15 mmHg or more on room air), and intrapulmonary vascular dilatation.

Endotoxemia and bacterial translocation from a congested splanchnic bed activate pulmonary macrophages, which release nitric oxide, carbon monoxide, TNF-alpha, and endothelin. Pulmonary capillaries dilate from a normal 8-15 micrometers to 15-500 micrometers. Blood transits too quickly and too far from alveolar gas to equilibrate, arteriovenous collaterals open, and the result is right-to-left shunt with V/Q mismatch. Hypoxic pulmonary vasoconstriction is blunted in these floppy vessels, so the lung cannot self-correct.

Dilatation is worst at the bases, which is why sitting up makes the patient worse. HPS is present in 5-32% of transplant candidates, and its severity does not track the severity of the liver disease.