Which babies "sink" after PDA ligation?

30% of preemies who are over 32 weeks GA, and 60% who are under 28 weeks GA have a PDA.

Ligating a symptomatic PDA in a fragile premature infant can have substantial (but usually transient) unwanted hemodynamic consequences. The sudden ligation of the PDA causes an instantaneous rise in afterload, resulting from the obliteration of the the pop-off circuit into the low resistance pulmonary circulation, and an associated drop in preload. This sudden change may not be tolerated well by preemies, most likely due to underlying cardiac dysfunction. So how can we predict which infant is going to fare worse after ligation?

Moin et al, in a study that evaluated 100 premature infants who underwent PDA ligation, noted that 32% of preemies required vasopressor support (either starting pressors or increasing the dose of preexisting pressor support) within 72 hours of PDA ligation. Risk factors associated with need for vasopressor support were a lower gestational age (25 vs 26 weeks), lower birth weight (714 vs 870 grams), and relatively high ventilatory support (RIS>6).

Additionally, those infants who required pressor support after ligation had an increased risk of death before 36 week adjusted gestational age.

The authors cautioned that the study had several limitations by virtue of it's design and that further studies are needed to confirm their observations.

References:

Moin F et al. Risk factors predicting vasopressor use after patent ductus arteriosus ligation. American Journal of Perinatology;20(6)2003:313-320

Laparoscopic inguinal hernia repair in children. Why?

Inguinal hernia repair with high ligation of the hernia sac through an inguinal approach is one of the most commonly performed operations in the pediatric population. The laparoscopic approach to IH repair in children is certainly an attractive option, given that it entails no manipulation of cord structures, allows for the repair of recurrent hernias (initially repaired by an inguinal approach) through fresh tissue, and allows for the inspection of the contralateral internal ring (whatever implications that my have!). However, the fact that an intact hernia sac is left behind within the inguinal canal when hernias are repaired laparosocopically makes me wonder about recurrence.

Two main techniques for the closure of the internal ring from a peritoneal approach are described; the lap assisted/percutaneous closure (SEAL) and the totally laparoscopic approach. Both entail closing the internal ring (using a "purse string" or "N"-shaped type of suture) while avoiding the vas and vessels.

A recent series out of Mainz, Germany looked at over 500 patients who underwent a totally laparoscopic repair with a suture used in an "N"-shaped fashion. After a median follow up of 40 months, the recurrence rate was 4%. This dropped to 2% with the last 100 patients; an improvement that the author attributed to a refinement of the technique of internal ring closure.

Understandably, the concept of laparoscopic repair is very attractive, particularly in the setting of recurrent hernias. However, one must keep in mind that even in the most experienced hands, the recurrence rate of laparoscopic hernia repair is still 4 times higher than the classic repair.


References

Harrison et al. The subcutaneous endoscopically assisted ligation (SEAL) of the internal ring for repair of inguinal hernias in children: a novel technique. Journal of Pediatric Surgery (2005) 1177-1180

Schier F. Laparoscopic inguinal hernia repair-a prospective personal series of 542 children. Journal of Pediatric Surgery (2006) 41, 1081-84