1 Division of Neonatal Biology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington
The interesting paper by Graven, et al. on changes in serum lactate with activity in neonates1 is confusing in one respect. The authors indicate that measurements of pCO2 and pH were performed on the umbilical venous blood samples and yet no data are presented. This is of more than passing interest because it has been shown that blood lactate may rise quite rapidly as a consequence of hyperventilation.2 Furthermore, we have shown that the response to arousal as measured by changes' in oxygen tension in the descending aorta below the ductus arteriosus is quite variable and must be due to a varying response of ventilation as well as to changes in shunting through the foramen ovale or the ductus arteriosus.3