Permissive hypercapnia in extremely low-birthweight infants: how far should we go?

Abstract

Commentary on: Thome UH, Genzel-Boroviczeny O, Bohnhorst B, Schmid M, Fuchs H, Rohde O, Avenarius S, Topf H-G, Zimmermann A, Faas D, Timme K, Kleinlein B, Buxmann H, Schenk W, Prof Segerer H, Teig N, Gebauer C, Hentschel R, Heckmann M, Schlosser R, Peters J, Rossi R, Rascher W, Bttger R, Seidenberg J, Hansen G, Zernickel M, Alzen G, Dreyhaupt J, Muche R, Hummler HD, for the PHELBI Study Group. Permissive hypercapnia in extremely low birthweight infants (PHELBI): a randomised controlled multicentre trial. Lancet Respir Med 2015; 3: 534–43. PMID26088180. Permissive hypercapnia is a strategy used to reduce ventilator-induced lung injury, by employing low tidal volumes and accepting PaCO2 levels above ‘normal’ to decrease volutrauma 1. The PHELBI study did not show that higher PaCO2 targets reduce death or moderate to severe BPD associated, despite using lower ventilator pressures. Moreover, higher PaCO2 targets were associated with an increased incidence in the combined outcome of BPD/death and NEC in infants with severe lung disease. Another three small RCTs 2-4 demonstrated heterogeneous results in this regard. Moreover, this study has demonstrated that hypercapnia did not increase IVH and ROP. Previous studies showed conflicting results regarding the effect of hypercapnia on the incidence of IVH in preterm infants; a retrospective study of 849 infants weighing ≤1250 g revealed that severe hypocapnia, severe hypercapnia and wide fluctuations in PaCO2 were associated with an increased risk of IVH 5; Mariani et al. 2 reported a nonsignificant increase in IVH in hypercapnic compared with normocapnic infants, Carlo et al. 3 observed a nonsignificant increase in IVH in infants managed with lower targeted PaCO2 <48 mmHg (6.4 KPa) vs. >55 mmHg (7.3 KPa) and secondary analysis of the SUPPORT trial revealed that higher PaCO2 in the first two weeks of life was an independent predictor of severe IVH/death, BPD/death and NDI/death 6. Where do we go from here? Should the ELBW infant require mechanical ventilation, while it is difficult to define the optimal target range of PaCO2, normocapnic or mildly hypercapnic PaCO2 targets as used in the control group of the PHELBI study seem to be safe, whereas higher PaCO2 targets do not lead to further benefits and may even be harmful. Further studies are required to define the optimal target for PaCO2 in mechanically ventilated ELBW infants. https://ebneo.org/2015/11/permissive-hypercapnia-in-extremely-low-birthweight-infants-how-far-should-we-go/ None. None.