INTRODUCTION
Patent ductus arteriosus (PDA) is common among preterm babies (preemies) with incidence of 10 to 15% in very low birth weight infants.[1] Spontaneous closure of PDA occurs in 24% patients, 50-75% respond to pharmacological treatment with only 15% needing surgery.[2] PDA ligation in preterm neonates is usually uneventful despite the technical challenges it poses. However care should be taken to avoid inclusion of adjacent structures in the clip used for ligation. Reports of left pulmonary artery having been erroneously ligated instead of the PDA are many.[3] We present an unusual case where the left main bronchus (LMB) was occluded along with the PDA within the same ligaclip.
CASE REPORT
A baby girl weighing 780 g was born at 25 weeks of gestation. At 10 days of age, her PDA measuring 5-6 millimeters remained patent despite a course of oral ibuprofen, and intravenous indomethacin. As it was difficult to wean her from continuous positive airway pressure (CPAP) ventilation, a decision to ligate the PDA was made. Echocardiography showed normal intracardiac anatomy and a volume loaded left heart.
The operation was performed in the neonatal intensive care unit (NICU). EKG, pulse oximetry, non-invasive blood pressure in the lower limb and end tidal carbon dioxide levels were monitored. Our anesthesia protocol in such situations consists of administering 5 mcg/kg bolus of fentanyl followed by an infusion at 10 micrograms/kg/h and 100 mcg/kg bolus of Midazolam. Vecuronium 100 mcg/kg was administered for muscle relaxation. Left hemithorax was accessed through a third space posterolateral thoracotomy and the PDA was carefully dissected. A medium-large ligaclip® (Ethicon Endo-Surgery LLC, USA) was used to occlude the PDA.
Soon after PDA closure the oxygen saturations dropped to the mid-80s and left lung was found to be partially collapsed. At this point it was assumed that either the endotracheal tube (ETT) had dislodged into the right main stem bronchus or a mucus plug had occluded the left main bronchus causing the left lung to collapse. Repositioning of the ETT was attempted under the drapes but it did not help in getting the collapsed lung to expand. Fearing accidental extubation we decided to look for the cause after completion of the procedure.
Postoperative chest radiograph revealed complete collapse of left lung [Figure 1a]. Position of the endotracheal tube was checked and found acceptable. The collapsed lung did not respond to conservative management. The baby was extubated to non-invasive nasal CPAP 4 days later. Chest X-ray post-extubation showed persistent left lung collapse. Bronchoscopy 5 days after surgery showed occlusion of the LMB with inability to visualize the distal left bronchial tree. Spiral computed tomography of the chest revealed collapse of the left lung. It also showed that the ligaclip was located at the level of left main bronchus passing across it [Figure 1b].
Figure 1.
(a) Chest X-ray immediately after PDA ligation: Completely collapsed left lung and the ligaclip. (b) CT Scan: Ligaclip applied across the left main bronchus, with a collapsed left lung and a hyperinflated right lung. (c): Chest X-ray following repair of the left main bronchus: Well inflated left lung. The ligaclip has been removed
Help was sought from a surgeon with expertise in pediatric pulmonary surgery. At re-exploration the ligaclip was found to be applied across the ductus arteriosus and included the left main bronchus as well. Careful dissection was done and the clip was removed. The left main bronchus was then repaired. Under-water testing of the anastomosis showed no air leak. A post-operative bronchogram showed successful repair of the LMB with minimal narrowing at the anastomotic site. Chest X-ray done postoperatively showed a fully expanded left lung [Figure 1c]. The baby was scheduled for check bronchoscopy and a bronchogram in 12 weeks time. Unfortunately, the baby developed overwhelming candida sepsis 2 weeks after surgery, and despite promptly being started on antifungal agents the child succumbed to the infection.
DISCUSSION
Commonest major complication reported in the literature during PDA ligation surgeries is ligation of left pulmonary artery instead of PDA because in premature babies a large PDA can be confused with the aortic arch and the distal left pulmonary artery has been dissected underneath it and ligated.[3] While searching the literature, we came across only one published case where the LMB was partially occluded in a preemie PDA.[4] The rarity of such a complication prevented us from looking specifically for an occluded left main bronchus by the clip. Acceptable blood gases enabled extubation of the trachea, but the need for non-invasive ventilation persisted, which necessitated a bronchoscopy.
In neonates the left main bronchus forms a close inferior relation to PDA[5] [Figure 2]. Experts emphasize that the ligaclip should be applied well beyond the PDA to ensure complete occlusion and do not mention left main bronchial injury as a possible complication.[6]
Figure 2.
Anatomical relationship between the left main bronchus and the PDA in a neonate. (From: Anatomy of the Neonate: An Atlas: By Edward Crelin; With permission Yale University Press)
In larger babies the relatively bigger size of the bronchus may prevent such a dissection plane from developing. Minimal dissection in ligating preemie PDAs is encouraged because of potential risk of damage to very friable ductal tissue with possibility for catastrophic haemorrhage.[7]
CONCLUSION
Ligation of a large PDA in premature babies carries a risk of LMB injury. At the end of the procedure the presence of a collapsed left lung should raise the suspicion of bronchial occlusion. If in doubt about the exact nature of the injury, a bronchoscopy and/or a CT scan should be performed prior to undertaking surgical re-exploration.
ACKNOWLEDGMENT
Authors would like to thank Mr. Mohammed Abdul Samad for his help with the images.
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