Eisenmenger Syndrome (ES)

Protect the PVR:SVR balance - The overriding goal. A fall in systemic vascular resistance (SVR) increases right-to-left shunt and causes profound hypoxemia. Maintain SVR aggressively with phenylephrine or norepinephrine and treat hypotension the instant it appears.

Avoid raising PVR - Hypoxia, hypercarbia, acidosis, hypothermia, pain and sympathetic surges, and high airway pressures or PEEP all raise pulmonary vascular resistance and worsen shunting. Optimize oxygenation and ventilation and have a pulmonary vasodilator (inhaled nitric oxide or epoprostenol) available.

Meticulous de-airing - With a right-to-left shunt any IV air bubble crosses to the systemic, cerebral, and coronary circulation as a paradoxical embolus. Scrupulously de-air every line and use air filters on all IV access.

Hemodynamic monitoring and reserve - Place an arterial line for beat-to-beat pressure; preserve preload and avoid myocardial depression, as the pressure-overloaded right ventricle tolerates hypotension and depression poorly.

Cautious with neuraxial - A single-shot spinal is generally avoided because the abrupt sympathectomy drops SVR; a slowly titrated epidural with vigilant SVR support can be used. Balanced general anesthesia that maintains SVR is a common choice.

Hematologic paradox - Chronic hypoxemia drives secondary erythrocytosis with both bleeding (platelet and factor abnormalities) and thrombosis risk; avoid dehydration and hyperviscosity, and manage anticoagulation carefully.

Infection precautions - Endocarditis risk is high; use strict aseptic technique and appropriate antibiotic prophylaxis.

The end stage of a large, uncorrected congenital left-to-right shunt (ventricular septal defect, atrial septal defect, or patent ductus arteriosus). Chronic pulmonary overcirculation remodels the pulmonary vasculature into severe, fixed pulmonary arterial hypertension (PAH). Once pulmonary vascular resistance (PVR) exceeds systemic vascular resistance (SVR) the shunt reverses to right-to-left, producing cyanosis and secondary erythrocytosis. From then on the shunt fraction and the patient's oxygenation ride entirely on the PVR:SVR balance - anything that lowers SVR or raises PVR deepens right-to-left shunting and hypoxemia. Perioperative mortality is high, and this physiology is the reason for essentially every anesthetic decision.