Pediatric cardiac surgeons at Children’s National Health System in Washington, D.C., perform the Stage 1 Norwood surgery to correct the hearts of infants born with congenital defects.1 They find postoperative management after Stage 1 Norwood surgery particularly challenging because of the lack of real-time monitoring or data about systemic and pulmonary blood flow.
Now, novel Transonic miniaturized transit-time ultrasound Flowprobes have given these surgeons new post-op management options by measuring direct volume blood flow on a valved femoral vein homograft for Sano shunts used in the procedure.
Under Internal Review Board (IRB) approval, the surgeons measured continuous blood flow after Norwood Stage 1 surgery in three 4- to 6-month-old neonates weighing 2 to 3.4 kgs. The Flowprobe was placed around the femoral vein extension of a 5mm ePTFE graft and remained in place until the infants’ chests were closed several days after surgery.
From the flow data, the surgeons learned that all three patients had balanced circulations. They, therefore, assumed that pulmonary blood flow reflected systemic cardiac output. Compared to flows ascertained upon admission to the ICU, there was a progressive decline in pulmonary blood flow to less than 2L/min/m2 in all patients. The lowest point was eight hours after surgery. This low flow state continued for another 40-45 hours and then flow gradually returned to baseline. The second period of low flow of <2L/min/m2 corresponded to aggressive diuresis to allow delayed closure of the chest. No conventionally monitored parameters reflected similar flow changes.
The Transonic flow measurements showed significant, prolonged low pulmonary blood flow after Norwood Stage 1 surgery in these infants. The surgeons, therefore, concluded that continuous measurement of pulmonary blood flow is not only feasible with modification to the shunt after Stage 1 Norwood surgery, but allows for improved management of low flow conditions and fine-tuning of postoperative diuretic therapy, delayed sternal closure and other therapies.
1Reference: Sinha L, Yerebakan C, Jonas R, Pranava Sinha P, “Use of Ultrasonic Flow Probe for Realtime Pulmonary Blood Flow Monitoring after Norwood Stage 1 Operation,” Department of Cardiovascular Surgery, Children’s National Health System, Washington, D.C.