What are the key monitoring parameters and potential complications in a pediatric patient post Sano (Systemic to Pulmonary Artery) Norwood procedure?

Post-Sano Norwood Monitoring: Critical Parameters and Complications

In a pediatric patient following the Sano modification of the Norwood procedure, you must vigilantly monitor for shunt patency, balanced systemic-to-pulmonary blood flow, and early signs of life-threatening complications including shunt thrombosis, coronary insufficiency, and ventricular dysfunction, as these directly impact survival. 1

Immediate Life-Threatening Complications Requiring Recognition

Shunt Thrombosis and Stenosis

• Shunt thrombosis occurs in 9.3% of patients, with 20% occurring shortly after surgery 1
• Presents with acute desaturation and cardiovascular collapse 1
• The absence of a continuous murmur with acute desaturation indicates shunt thrombosis and requires emergent intervention 1
• Progressive cyanosis and decreased pulmonary blood flow suggest shunt stenosis 1
• Catheter-based stent implantation can effectively treat Sano shunt obstruction, with oxygen saturation increasing from median 58% to 80% post-intervention 2

Dynamic Proximal Shunt Stenosis

• A dynamic proximal stenosis of the RV-to-PA conduit can cause persistent cyanosis 3
• Beta-blockers (propranolol) reduce the gradient in the synthetic conduit, increase arterial oxygen saturation, decrease heart rate, and increase blood pressure 3
• This intervention results in clinical improvement when dynamic obstruction is present 3

Coronary Insufficiency

• Particularly concerning in hypoplastic left heart syndrome (HLHS) due to coronary arteries arising from a small aortic root 1
• Monitor for ST-segment changes on continuous ECG 1
• Serial echocardiography should assess for ventricular dysfunction 1

Excessive Pulmonary Blood Flow

• Presents with pulmonary overcirculation, systemic hypoperfusion, metabolic acidosis, and oliguria 1
• Requires immediate adjustment of pulmonary-to-systemic blood flow balance 1

Aortic Arch Obstruction

• Related to the PA-to-aorta anastomosis 1
• Presents with upper-to-lower extremity blood pressure gradient 1
• Requires serial imaging surveillance 1

Essential Monitoring Parameters

Continuous Monitoring

• Continuous cardiac telemetry, pulse oximetry, capnography, and temperature monitoring are essential 4
• Arterial catheter for continuous intra-arterial pressure monitoring to identify and treat hypotension 4
• Central venous catheter to monitor central venous oxygen saturation (SvO2) and provide medication access 4

Cerebral Oxygenation Monitoring

• Mean cerebral oxygen saturation (cSaO2) by near-infrared spectroscopy (NIRS) below 56% over the first 48 hours post-operatively predicts adverse outcomes with 75% sensitivity and 79.4% specificity 5
• Low cerebral NIRS has strong association with subsequent adverse events including prolonged ICU stay, need for ECMO, or death 5
• Target cerebral saturation above 56% in the first 48 hours 5

Hemodynamic Parameters and Their Limitations

• Routine clinical parameters (heart rate, systolic arterial pressure, arterial oxygen saturation) do not accurately reflect oxygen transport after Norwood procedure 6
• Higher heart rate and systolic arterial pressure correlate with worse oxygen transport balance 6
• SvO2 is the most reliable clinical parameter, positively correlating with cardiac output, systemic blood flow, and oxygen delivery 6
• SvO2 should be maintained to ensure adequate oxygen delivery 6

Laboratory Monitoring

• Arterial lactate and central venous oxygen saturation assess adequacy of tissue oxygen delivery 4
• Venous or arterial blood gases, serum electrolytes, glucose, and calcium concentration 4
• Hemoglobin concentration, renal function, and coagulation function 4
• Assessment for signs of inflammation and infection 4

Imaging

• Chest x-ray to evaluate endotracheal tube position, heart size, and pulmonary status 4
• Serial echocardiography to assess ventricular contractility, ejection fraction, and identify myocardial dysfunction 4, 1
• Echocardiography is beneficial for identifying congenital and acquired cardiac abnormalities 4

Physical Examination Findings

Expected Findings

• A continuous murmur indicates patent shunt; absence suggests thrombosis 1
• Absent or diminished brachial pulse on the side of the shunt is expected 1
• Baseline cyanosis and clubbing are expected 1

Concerning Findings

• Worsening cyanosis indicates shunt dysfunction 1
• Signs of respiratory distress including accessory muscle use, tracheal tug, sternal/subcostal/intercostal retractions, agitation, or restlessness 7
• SpO2 < 90%, bradycardia, or inability to feed 7

Home Monitoring Program for Interstage Period

Daily Documentation

• Families should document oxygen saturation, heart rate, weight, and feedings daily 8
• Nurse practitioners should call each family at least weekly 8
• Action plans determined based on symptom severity when issues arise 8

Impact on Outcomes

• Home monitoring programs reduce interstage mortality from 7% to 0% 8
• 41% of patients require interstage admission 8
• 37% require interstage interventions (17% major interventions including conduit stenting, aortic arch balloon angioplasty, emergent shunt, or early Glenn surgery) 8
• Home monitoring allows timely interventions and comprehensive care coordination 8

Neurological Monitoring

Continuous Assessment

• Serial neurological examinations to identify evolving hypoxic-ischemic brain injury 4
• Electroencephalogram (EEG) monitoring given high incidence of electrographic seizures after cardiac surgery 4
• Neuroimaging can identify cerebral causes and presence of severe brain injury 4

Critical Pitfalls to Avoid

• Failing to recognize shunt thrombosis early (absence of continuous murmur with acute desaturation) requires emergent intervention 1
• Relying solely on arterial oxygen saturation without monitoring SvO2 and cerebral NIRS 6, 5
• Interpreting higher heart rate and blood pressure as reassuring when they actually correlate with worse oxygen transport 6
• Inadequate frequency of monitoring during the critical first 48 hours post-operatively 5
• Delaying intervention when cerebral saturation falls below 56% 5