Physiological marker and surgical ligation of patent ductus arteriosus in neonates

Background: In preterm infants, immediate complications of surgical closure of a patent ductus arteriosus (PDA) are often serious and due to haemorrhage or ligation of incorrect structures. The aim of this study was to measure blood pressure (BP) changes during ligation and hence introduce a novel physiological marker to alert surgeons to the ligation of incorrect structures. Materials and Methods: This study included 146 preterm babies (≤35 weeks of gestation) who underwent surgical PDA closure of a left-to-right unidirectional PDA between June 2006 and December 2015. The median weight was 920 g (range, from 520 to 2200 g). In all cases, the PDA was test cross-clamped, and the lower limb or umbilical artery BP was recorded before ligation. Results: Based on preoperative echocardiography, the PDA diameter range was 2-4 mm in 135 cases and 5-6 mm in 11 cases. During test clamping of the PDA, a 20-60% rise in mean BP was recorded. The lower figure was observed with smaller PDAs. Conclusion: It is estimated that the mean BP should rise by 10% for every mm of PDA diameter during test clamping and ligation of the PDA, irrespective of weight or age. The absence of this expected rise in mean BP indicates that an incorrect structure might have been clamped.