Non-cardiac surgery in a child after palliative surgical repair of tetralogy of Fallot

Abstract

Citation: Sharma A, Swami A, Chawla M. Non-cardiac surgery in a child after palliative surgical repair of tetralogy of Fallot (Correspondence). Anaesth Pain & Intensive Care 2014;18(4):467-68

Sir,

A child underwent a modified Blalock Tausig (left subclavian to pulmonary artery anastomosis) procedure at the age of 6 months for a tetralogy of Fallot. He was now 3 year old weighing 10 kilograms and awaiting a definitive surgical correction. He presented with a huge abscess on the right side of neck, was planned for incision and drainage under general anesthesia. The child had been doing reasonably well after the palliative surgery, he had picked up weight. Clinical examination was grossly apart from a soft continuous murmur in the right subclavicular area and the blood chemistry was within normal limits. Presence of any other co-existing anomaly was ruled out. He was premedicated with Syrup Midazolam 0.7 mg/kg given orally an hour prior to the surgery. He was brought in the operating room asleep under monitoring by the anesthetist. Anesthesia was induced with 3% sevoflurane and Fentanyl 30 mcg IV. Inj Cefotaxime 300 milligrams was given intravenously after a test dose. Anesthesia was maintained with 2% sevoflurane on spontaneous ventilation with face mask and modified Jackson-Rees circuit. His heart rate was 90-110/min and SpO₂ 86-90%. Sevoflurane was switched off at the time of dressing of the wound and patient was woken up on oxygen:air mixture. Inj. paracetamol 200 mg was given at the same time. Once the child was completely awake he was shifted to the post-operative recovery room. After four hours he was discharged to the ward and he went home on the second post-operative day.

Tetralogy of Fallot occurs with a frequency of 3.6% in the normal population with an incidence of 1:3600 live births. The cause is unknown but there is an association with a chromosomal anomaly. The main clinical features are reduced pulmonary blood flow and cyanosis, and are variable in severity, depending on the degree of obstruction of the RVOT. After closure of PDA, decrease in pulmonary blood flow leads to deterioration in SpO₂. To prevent this deterioration in neonates PGE1 in the dose of 0.05-0.2 µg/kg/min is recommended to keep PDA patent to buy the time for surgical correction. Palliative surgery is done to divert systemic blood to lungs. Complete correction involves repair of VSD and widening pulmonic valvular area.

These patients tend to have lower body weight, poor vascular access after surgeries and lower pulse volume and pressures on the side of subclavian artery used for anastomosis.

The goal of the anesthetic management is to maintain intravascular volume and SVR, and low PVR. In general the room air saturation in non operated patients is around 70-80%, after palliative surgery 80-90% and after complete correction close to 100%. Hematocrit should be maintained between 35-45%, maintain cardiac output with or without inotropes e.g Dopamine, and keep oxygen consumption low by adequate sedation/anesthesia and muscle relaxation if necessary. The most important consideration or the concern is that of shunt blockage and the anesthetist managing the case should always be vigilant. The cardiac output should always be maintained. If an intravenous cannula is in situ anesthesia can be induced with ketamine 3-5 mg/kg along with glycopyrrolate and midazolam. For inhalational induction and maintenance, Sevoflurane is preferred gas as it is sweet smelling, causes lesser myocardial depression than halothane and has minimal effect on SVR or PVR at MAC 1-1.5. Its important to keep in mind that PaCO₂– EtCO₂ difference is more (10-15mmHg) due to increased physiological dead space. Its mandatory to always be ready to tackle with hypercyanotic spell with 100% O₂, compression of abdominal and/or femoral arteries, phenylephrine 5-10 µg/kg or 2-5 µg/kg/min, morphine 0.05-0.1 mg/kg, bolus of IV fluids 15-30 ml, sodium bicarbonate 1-2 mEq/kg prophylactically if ABG facility is not there, esmolol 0.5 mg/kg followed by 50-300 µg/kg/min or propranolol 0.1 mg/kg and finally ECMO in refractory cases. These patients should be looked after well in the postoperative period and shifted only after being completely recovered.

Reference

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