We congratulate Sehgal and colleagues for their study (1) that found prophylactic surfactant causes major haemo-dynamic changes in preterm babies. This publication follows close on the heels of a study in the NEJM that found that prophylactic surfactant was no better than continuous positive airway pressure (CPAP)ventilation (2). It is significant that both these papers (1,2) quote a Cochrane meta-analysis in there introduction to suggest that prophylactic surfactant reduces mortality (3). This is a misinterpretation of the Cochrane report. The meta-analysis had found that there was no difference in the in-hospital deaths, after use of surfactant (Risk Ratio: 0.70, 95% C.I. 0.47 - 1.06). It however found that surfactant reduces incidence of deaths in the first 30 days of life and this was then reported as a reduction in neonatal mortality (Risk Ratio: 0.80, C.I. 0.72 - 0.88). The Cochrane meta-analysis was revised recently (4) but this misleading statement in the abstract has survived into the new version also. The fact that leading researchers working with surfactant carry this wrong impression from the Cochrane report suggests that the report needs to be revised for clarity. We hope that this letter will in a small way, add to the results of newer studies on surfactant(1,2), to clarify the issue that prophylactic surfactant is not useful in reducing mortality.

References

1. Haemodynamic changes after delivery room surfactant administration to very low birth weight infants Arvind Sehgal, Wendy Mak, Michael Dunn, Edmond Kelly, Hilary Whyte, B McCrindle, Patrick J McNamara Arch. Dis. Child. Fetal Neonatal Ed. published 10 June 2010, 10.1136/adc.2009.173724

2. SUPPORT Study Group of the Eunice Kennedy Shriver NICHD Neonatal Research Network. Early CPAP versus Surfactant in Extremely Preterm Infants. N Engl J Med. 2010 May 16. [Epub ahead of print] PMID: 20472939

3. Soll RF. Prophylactic natural surfactant extract for preventing morbidity and mortality in preterm infants. Cochrane Database Syst Rev 2000;2:CD000511.

4. Soll R, Ozek E. Prophylactic animal derived surfactant extract for preventing morbidity and mortality in preterm infants. Cochrane Database of Systematic Reviews 1997, Issue 4. Art. No.: CD000511. DOI: 10.1002/14651858.CD000511

Conflict of Interest:

None declared

Dear editor,

With great interest we read the article by Sehgal et al describing the hemodynamics of surfactant administration in the delivery room. The authors found a low RVO, low LVO, low to normal SVC flow and an increasing RVO:LVO ratio in the first 60 minutes after surfactant administration. Surprisingly, SVC flow is responsible for 62% of RVO in the pre-surfactant measurement and up to 79% of LVO at 1 hour after surfactant. This combined with a large duct and exclusive left-to-right shunting would mean there is very little blood flow to the lower body. However, this was not reflected by the arterial pH. The authors provide hemodynamic explanations, but do not discuss methodological issues surrounding Doppler-derived cardiac output measurements. Delivery room hemodynamics are not extensively studied, but some information is available for healthy term newborns. Agata et al. measured 34 healthy term infants at 1 hour of age and found a LVO of 327 /- 66 ml/kg/min, followed by a decrease.1 Walther et al. showed comparable findings in a group of 32 term infants starting at 30 minutes after birth.2 We re-analysed a previously published cohort of preterm infants who were studied during lung recruitment.3 There were 9 infants who were measured within 1 hour after birth immediately after the change to high frequency ventilation. In this group the median (range) RVO and SVC flow was 325 (251-541) and 74 (48-126) ml/kg/min respectively. The ductal diameter was 2.9 (1.7-3.6) mm with total ductal shunting always left-to-right. We suggest that differences in methodology may explain the differences in findings. Detailed information on where LVO and RVO diameters were determined was not provided. The Pa Vmax is suggestive of an expected RVO of 150-300 ml/kg/min 4 so it is possible that a reduced diameter measurement could explain the low RVO and LVO compared to values found using other referenced methodology.5 Further investigations into whether the low-normal SVC flow is caused by the early surfactant administration and if this coincides with low peripheral blood flow will be required to establish the full picture and potential consequences of these observations.

1. Agata Y, Hiraishi S, Oguchi K, Misawa H, Horiguchi Y, Fujino N, Yashiro K, Shimada N. Changes in left ventricular output from fetal to early neonatal life. J Pediatr. 1991;119(3):441-5

2. Walther FJ, Benders MJ, Leighton JO. Early changes in the neonatal circulatory transition. J Pediatr. 1993;123(4):625-32

3. de Waal K, Evans N, van der Lee J, van Kaam A. Effect of lung recruitment on pulmonary, systemic, and ductal blood flow in preterm infants. J Pediatr. 2009;154(5):651-5

4. Evans N. Support of the preterm circulation: keynote address to the Fifth Evidence vs Experience Conference, Chicago, June 2008. J Perinatol. 2009;29 Suppl 2:S50-7

5. Evans N, Kluckow M. Early determinants of right and left ventricular output in ventilated preterm infants. Arch Dis Child Fetal Neonatal Ed. 1996;74(2):F88-94

Conflict of Interest:

None declared