Efficacy and neurologic outcome of profound hypocapneic alkalosis for the treatment of persistent pulmonary hypertension in infancy Twenty-three newborn infants with severe bilateral pulmonary disease and persistent pulmonary hypertension received mechanical ventilation to pH >7.55 and Paco2 <25 torr. Response, as defined by attainment of a Paoe >100 torr, occurred in 87% of patients. Analysis of sequential arterial pH determinations revealed a linear increase in the number of infants responding as arterial pH increased. However, individual patients varied greatly in the optimal pH necessary to correct hypoxemia (range pH 7.50 to 7.75). Sixteen patients who had received mechanical hyperventilation were observed for 11.1 +- 2.3 months. Virtually all had normal growth and development on follow-up physical and neurologic examinations, often despite profound or prolonged alkalosis and hypocarbia. In l I infants at a corrected gestational age of I year, Bayley Scales of Infant Development revealed normal mental developmental indices (mean 106.2 +_ 15.4) and normal, but significantly lower, psychomotor developmental indices (93.2 + 11.7) (P < 0.005). Although response and short-term outcome of neonatal hyperventilation appear favorable, this technique should be reserved for critically ill infants, because its long-term effects on the central nervous system are unknown. (J PEDIATR 105:457, 1984) Bruce Ferrara, M.D., Dana E. Johnson, M.D., Ph.D., Pi-Nian Chang, Ph.D., and Theodore R. Thompson, M.D. Minneapolis, Minnesota ELEVATED PULMONARY VASCULAR RESISTANCE, causing systemic hypoxemia from right-to-left shunting at the level of the ductus arteriosus or foramen ovale, occurs in newborn infants with a variety of underlying pulmonary diseases? -9 Therapy for this syndrome of PPH has been directed at decreasing the ratio of pulmonary to systemic vascular resistance, thereby decreasing the amount of right-to-left shunting. Recently, several groups have dem- onstrated that hypocarbic alkalosis induced by mechanical ventilation is an effective mode of therapy for decreasing pulmonary artery resistance in affected newborn infants~ thereby improving systemic oxygenation. 5-8 Hypocarbia, however, has also been shown in laboratory animals and in From the Department of Pediatrics, Division of Neonatology, University of Minnesota Medical School. Submitted for publication Dec. 14, 1983,"accepted for publication Feb. 4, 1984. Reprint requests: Bruce Ferrara, M.D., University of Minnesota Hospitals, Box 213 Mayo Memorial Building, 420 Delaware St. S.E., Minneapolis, MN 55455. adults to cause cerebrovascular vasoconstriction with decreased cerebral blood flow. 1~ As decreased CBF has been implicated as a factor for the development of cerebral atrophy in the newborn period, ~5 concern exists that induced hypocarbic alkalosis might predispose newborn 'infants to neurologic handicaps secondary to cerebral atrophy? 6 CBF Cerebral blood flow PPH persistent pulmonary hypertension We report the response to mechanical hyperventilation (nra 7 7.~, Pco2 <25 torr) in a series of newborn infants with PPH and systemic hypoxemia despite administration of 100% oxygen by mechanical ventilation. The clinical response and follow-up data in these patients demonstrate that a therapeutic response in a given infant may not occur until an extreme degree of alkalosis is attained, but that this profound alteration in the normal physiologic state is not associated with major neurologic sequelae at 1 year of age. The Journal of P E D I A T R l C S 457