Patent ductus arteriosus ligation: Do not take it easy.

Sir,

Ligation of patent ductus arteriosus (PDA) is one of the simplest cardiac surgery performed with negligible incidence of complications.[1] We describe a case of severe laryngospasm followed by acute ventricular dysfunction during the immediate post-operative periodinan 8-month-old infant who underwent PDA ligation.

An 8-month old infant weighing 5 kg was diagnosed to have a large PDA of 5 mm size with left to right shunting and gradient of 18/2 mm Hg on 2D transthoracic echocardiography as the sole cardiac problem. A plan for direct ligation of the PDA through the left thoracotomy was made. Pre-operatively, the only abnormal finding was a continuous murmur on his left second intercostals space. Anesthesia management was as per the standard protocol in our institute. His airway was secured with an uncuffed 4.5 size endotracheal tube. The procedure went uneventful and the blood pressures were maintained between systolic 85-90 Hg and diastolic of 50-60 mmHg. Arterial blood gas was normal except for an increase in PaCO2(45 mmHg), which was managed by adjusting the ventilator settings and endotracheal suctioning. Trachea was extubated at 1st post-operative hour and he had a normal arterial blood gas at 30 min post-extubation. At 2nd h post-extubation, he developed severe laryngospasm. At this time, arterial blood gas showed PaCO2 of 65 mmHg. His airway was secured immediately and the child was mechanically ventilated. Chest- X ray revealed gross cardiomegaly, which was not present in the pre-operative and immediate post-operative period. [Figures 1 and 2] A 2-D transthoracic echocardiogram revealed the presence of ventricular dilation and dysfunction. An additional arterial line was inserted in the right radial artery to rule out any possibilities of missed coarctation of the aorta. Injection dobutamine was started at a rate of 5 mickg/min to maintain hemodynamic. The child was gradually weaned off from the ventilator after 24 h and extubated after obtaining a normal blood gas analysis. Injection dobutamine was tapered after 2 days. A repeat 2D echocardiography revealed an improvement of ventricular dysfunction. A repeat chest X-ray showed a decrease in cardiomegaly [Figure 3] and the child maintained stable hemodynamic without inotropic support. He was discharged on the 5th post-operative day.

Figure 1

Post-operative chest X-ray

Figure 2

Pre-operative chest X-ray

Figure 3

Repeat postoperative chest X-ray

PDA ligation is a common closed heart surgery performed in neonates and infants and complications are minimal. In our case, the child developed laryngospasm and ventricular dysfunction during the immediate post-operative period. Mc Namara et al. analyzed echocardiography findings before and after PDA ligation in premature infants and found PDA ligation is associated with impaired left ventricular systolic performance attributable to altered loading conditions.[2] In our case, the ventricular dysfunction occurred after extubation and there was no abnormal finding in the pre-operative echocardiography. Galal et al. studied left ventricular dimensions and performance in 43 patients after surgical ligation of PDA based on ductal diameter and concluded that closure of large ductus arteriosus in children can lead to significant immediate deterioration of left ventricular performance.[3] In our case, the ductus arteriosus was large 5-6 mm size and could have been the cause of immediate ventricular dysfunction. This dysfunction was attributable to the regression of left ventricular end diastolic diameter and decrease in ejection fraction.

Laryngospasm and respiratory distress usually are found in infants under going PDA ligation due to iatrogenic vocal cord paralysis. Zabar et al. reported six cases of vocal cord paralysis who underwent PDA ligation and he noted that premature neonates were at greater risk.[4] In our case, the child developed immediate laryngospasm after extubation, but subsequently was normal after weaning off from the ventilator on next post-operative day, which rules out any vocal cord paralysis.

Valletta et al. reported the event of acute myocardial dysfunction following acute airway obstruction in a10-year-old girl. They attributed acute hypoxia as a causative agent.[5] The above literature studies have shown that PDA ligation is associated with complications such as laryngospasm and ventricular dysfunction. In our case, whether the ventricular dysfunction was a separate entity or it is related to the laryngospasm could not be determined. We believe that, even the incidence of this complication is extremely low it should not be ignored because of its grave prognosis.