What are the key considerations for post-Norwood surgery patient care?

Post-Norwood Surgery Monitoring and Management

Monitor for shunt patency, balanced systemic-to-pulmonary blood flow, adequate cardiac output, and early recognition of life-threatening complications including shunt thrombosis, coronary insufficiency, and ventricular dysfunction. 1, 2

Critical Hemodynamic Parameters to Monitor

Maintain meticulous surveillance of the following parameters to detect circulatory imbalance:

• Systolic, diastolic, and mean arterial blood pressure - essential for assessing systemic perfusion and shunt function 2
• Central venous pressure (CVP) - helps evaluate volume status and right ventricular function 2
• Oxygen saturation (SpO2) - target 75-85% to indicate balanced Qp:Qs ratio 2, 3
• Mixed venous oxygen saturation (SvO2) - reflects adequacy of systemic oxygen delivery 2
• Serum lactate levels - elevated lactate indicates inadequate tissue perfusion and impending shock 2
• Urine output - critical marker of end-organ perfusion; low urine output predicts mortality 2, 4

The pulmonary-to-systemic blood flow ratio (Qp:Qs) changes dynamically in the immediate versus stable postoperative periods, requiring continuous reassessment and adjustment of management 2.

Life-Threatening Complications Requiring Immediate Recognition

Shunt-Related Emergencies

• Shunt thrombosis - occurs in 9.3% of patients, with 20% occurring shortly after surgery; presents with acute desaturation and cardiovascular collapse 5
• Shunt stenosis - manifests as progressive cyanosis and decreased pulmonary blood flow 1
• Excessive pulmonary blood flow - presents with pulmonary overcirculation, systemic hypoperfusion, metabolic acidosis, and oliguria 1, 2

Cardiac Complications

• Coronary insufficiency - particularly concerning in HLHS due to coronary arteries arising from a small aortic root; monitor for ST-segment changes and ventricular dysfunction 6, 1
• Ventricular dysfunction - assess with serial echocardiography for contractility and ejection fraction 1
• Aortic arch obstruction - related to the PA-to-aorta anastomosis; presents with upper-to-lower extremity blood pressure gradient 6, 1
• Neoaortic dilation - requires serial imaging surveillance 6, 1

Systemic Complications

• Renal failure - carries the greatest mortality risk among all complications 7
• Cardiovascular collapse - second highest mortality risk 7
• Cardiac arrest - indication for ECMO in 79% of cases requiring mechanical support 4
• Low cardiac output state - indication for ECMO in 18% of cases 4

Physical Examination Findings

Assess for the following on daily examination:

• Continuous murmur - indicates patent shunt; absence suggests thrombosis 5
• Absent or diminished brachial pulse on the side of the shunt - expected finding 5
• Cyanosis and clubbing - baseline expected, but worsening indicates shunt dysfunction 5
• Signs of systemic hypoperfusion - cool extremities, delayed capillary refill, mottling 2

Postoperative Management Strategy

Immediate Postoperative Period (First 48 Hours)

Implement standardized protocols to reduce variability and improve outcomes:

• High-dose vasodilators - to reduce systemic vascular resistance and optimize Qp:Qs balance 3
• Inhaled nitric oxide - to reduce pulmonary vascular resistance and prevent pulmonary overcirculation 3
• Mechanical ventilation - aim for extubation by postoperative day 2 if hemodynamically stable; successful early extubation (by POD 2) increased from 41% to 67% with standardized protocols 8
• Avoid reintubation - reintubation within 72 hours decreased from 17% to 0% with guideline adherence 8

Medication Titration

Adjust vasoactive medications based on real-time hemodynamic parameters:

• Increase systemic vasodilators if systemic vascular resistance is elevated (high diastolic BP, low cardiac output) 2, 3
• Increase inotropic support if ventricular function is impaired (low SvO2, elevated lactate, oliguria) 2
• Adjust pulmonary vasodilators to maintain SpO2 75-85% 2, 3

Risk Stratification for Mortality

Identify high-risk patients requiring intensified monitoring:

• Weight < 2.5 kg - 1.6-fold increased risk of complications 7
• Preoperative shock - 1.5-fold increased risk 7
• Non-cardiac/genetic abnormality - 1.5-fold increased risk 7
• Preoperative mechanical ventilation - 1.3-fold increased risk 7
• Preoperative circulatory support - 4.0-fold increased risk 7
• Single right ventricle - 1.4-fold increased risk compared to single left ventricle 7

ECMO Considerations

Recognize indications and prognostic factors for ECMO support:

• ECMO is required in 28% of Norwood patients with overall survival of 33.3% in those requiring support 4
• Indications for ECMO: cardiac arrest (79%), low cardiac output state (18%), arrhythmia (3%) 4
• Duration of ECMO > 9 days is associated with 100% mortality 4
• Low urine output while on ECMO predicts worse survival 4
• Earlier ECMO initiation before multiorgan damage may improve outcomes 4

Complication Burden and Mortality

Understand that complications are common and cumulative:

• 75% of patients experience ≥1 complication with overall 22% mortality 7
• Mortality increases with number of complications: 1 complication (17%), 2 complications (21%), 3 complications (26%), 4 complications (33%), ≥5 complications (45%) 7
• Renal and cardiovascular complications carry the greatest mortality risk 7

Common Pitfalls to Avoid

• Failing to recognize shunt thrombosis early - absence of continuous murmur with acute desaturation requires emergent intervention 5
• Inadequate monitoring of Qp:Qs balance - both pulmonary overcirculation and undercirculation are life-threatening 2, 3
• Delayed ECMO initiation - waiting until multiorgan failure develops worsens outcomes 4
• Prolonged ECMO support beyond 9 days - associated with 100% mortality; consider transplant evaluation earlier 4
• Ignoring low urine output - strong predictor of mortality and indicator for escalation of care 2, 4