Anaesthetic management of an infant posted for ventricular septal defect closure with right-sided eventration of diaphragm.

Eventration of the diaphragm is a rare entity, characterised by abnormal elevation of a dome of diaphragm. In this condition, the diaphragm is composed of fibrous tissue with few or no interspersed muscle fibres. Eventration can be congenital or acquired. Congenital eventration results from inadequate development of muscles or absence of phrenic nerve. The common cause of acquired eventration is injury to the phrenic nerve from traumatic birth injury or surgery for heart disease. The perioperative anaesthetic management of diaphragmatic eventration along with ventricular septal defect with severe pulmonary hypertension makes this case both challenging and unique.

INTRODUCTION

Eventration of the diaphragm is a rare congenital anomaly, consisting of failure of muscular development of one or both hemidiaphragm. There is an abnormal elevation of one leaf of intact diaphragm. The unbroken continuity differentiates it from diaphragmatic hernia. It is a rare anomaly occurring 1 in 10,000 live births with male sex and left hemidiaphragm preponderance (5:1). We report a case of a 3-month-old female child, posted for ventricular septal defect (VSD) closure with right-sided eventration of the diaphragm, which is an extremely rare entity.[1]

CASE REPORT

A 3-month-old female baby weighing 3.5 kg was posted for VSD closure. On pre-anaesthetic evaluation, the history revealed repeated episodes of lower respiratory tract infection since birth. There was no history of feeding difficulty or cyanotic spells. Auscultation revealed decreased breath sound in the right infraaxillary and inframammary areas. Chest X-ray [Figure 1] showed homogenous opacity in the right lower zone.

Figure 1

Chest X-ray showing eventration of diaphragm on the right side

Computed tomography (CT) scan of chest confirmed the diagnosis of eventration as it revealed raised right hemidiaphragm with protrusion of liver with a smooth contour. Echocardiography revealed large malaligned VSD with severe pulmonary hypertension (PH) having pulmonary artery systolic pressure of 55mmHg. Laboratory investigations were within normal limits. Heart rate was 140/min and respiratory rate was 50/min. SpO2 was 96% in room air. Arterial blood gas revealed a pH 7.4, PO274 mmHg and PCO240 mmHg. The plan was VSD closure with plication of eventration of diaphragm. In the operating room, monitoring was done with electrocardiogram, non-invasive blood pressure and pulse oximetry. Her baseline heart rate was 140/min and blood pressure was 80/50 mmHg. General anaesthesia was induced with injection fentanyl 10 μg, injection midazolam 0.25 mg, injection ketamine 10 mg, injection vecuronium 0.5 mg and intubated with cuffed endotracheal tube 3.5 mm, fixed at 9 cm. Central venous catheter was inserted in the right internal jugular vein and arterial line was inserted in the right femoral artery. Isoflurane 0.6% to 0.8% was used along with an air-oxygen mixture and an FiO2 of 0.6. Ventilator parameters were set to deliver a low tidal volume of 6 ml/kg and care was taken to keep airway pressures below 25 mmHg. VSD closure was done under cardiopulmonary bypass (CPB). The patient was weaned off from CPB with injection adrenaline 0.05 μg/kg/min and injection milrinone 0.66 μg/kg/min. During surgery, a thin hypoplastic right hemidiaphragm was found with eventration. The diaphragm was plicated with a non-absorbable suture, while the liver and gut were freed and placed back into the abdominal cavity. The patient was haemodynamically stable and shifted to recovery. A trial of extubation was given on the 1st post-operative day as, pre-operatively, the SpO2 was normal with minimal O2 support and after fulfilment of extubation criteria. Nasogastric feeding was started in the 2nd post-operative day and the baby was discharged on the 6th post-operative day.

DISCUSSION

Anaesthetic challenges associated with VSD and eventration of diaphragm are unique. In eventration, the hemidiaphragm is floppy and thinned out. Any event which increases intraabdominal pressure, such as coughing, straining during light anaesthesia or extubation may cause rupture of the weakened diaphragm.[23] Following rupture, mass effect of the abdominal viscera may cause mediastinal shift and direct compression of the heart, vena cava and pulmonary veins with catastrophic reductions in venous return and cardiac output.[45] Thus, an adequate depth of anaesthesia is essential in these patients. Nitrous oxide is avoided as bowel distension can further aggravate compression and impair the circulation and respiration.[46] The other most important challenge in our case was the presence of a large VSD with severe PH. There is a great interplay of systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) in VSD. The shunt flows left-to-right during systole and preferentially to PA with generation of great pressure leading to PH. At times, the PH may exceed aortic outflow pressure leading to a right –to-left shunt with consequent desaturation, hypoxia and cyanosis.[7] In the present scenario, there was a possibility of worsening of PH and shunt reversal in the presence of already existent pulmonary hypoplasia and systemic hypotension due to mediastinal shift which eventually could lead to hypoxaemia. Hence, measures were taken to prevent high flows and high inflation pressures which would aggravate this precarious situation. The lungs were ventilated with a tidal volume of 5–6 ml/kg and low inflation pressures (<25 mmHg) with careful monitoring of SpO2, EtCO2 and airway pressures. At the same time, anaesthetic goals of managing VSD such as optimisation of preload, avoidance of hypovolaemia, maintaining normal SVR and preventing acute increases in PVR due to hypoxia, hypercarbia, acidosis and sympathetic stimulation were adhered to.[7] As there was a probability of right ventricular dysfunction in the presence of severe PH, inotropic supports such as adrenaline and milrinone were used during weaning from cardiopulmonary bypass. In diaphragmatic eventration, use of inhalation agents is controversial as it may inhibit hypoxic pulmonary vasoconstriction and worsen V/Q mismatch so, isoflurane was used, as it inhibits HPV least.[8] In eventration, the collapsed lung is prone to recurrent infection, so to improve lung function, plication of diaphragm should be instituted early and in all cases. The degree of pulmonary hypoplasia and associated anomalies are predictive of survival of baby. Measures to prevent lung collapse and effective physiotherapy play a major role in the post-operative period. Furthermore, to avoid barotrauma of the hypoplastic lungs, ventilation with low tidal volume and low inflation pressures with careful monitoring of SpO2, EtCO2 and airway pressures is imperative both in the intraoperative and post-operative period.[9] It is indeed, a challenge to extubate these children. In case of severe lung hypoplasia and PH where PaCO2 is >50 mmHg at a FiO2 of one, extracorporeal membrane oxygenation (ECMO) can be instituted to prevent lung injury.[610]

CONCLUSION

Early antenatal diagnosis, avoiding high airway pressure during ventilation and haemodynamic stability leads to better outcome in diaphragmatic eventration. In case of severe lung hypoplasia and PH, ECMO can be instituted early to prevent lung injury. The concept of permissive hypercapnia and gentle ventilation may have significant impact on survival of neonates.

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Conflicts of interest

There are no conflicts of interest.