Satyan Lakshminrusimha

Characteristics of pulmonary hypertension in preterm neonates

Objective:Characteristics of preterm infants who develop pulmonary hypertension (PHT) and their response to inhaled nitric oxide (iNO) are not well described. Our objective was to identify risk factors for PHT in infants <37 weeks gestational age (GA) and to evaluate their response to iNO.Study design:A retrospective chart review was conducted in infants <37 weeks GA born from July/2000 to October/2005 who had an echocardiographic diagnosis of PHT in the first 4 weeks of life. A comparison non-PHT group was generated matched for GA and birth date. Data on prenatal and postnatal characteristics, response to iNO and mortality were collected.Results:Low Apgar scores, preterm premature rupture of membranes, oligohydramnios, pulmonary hypoplasia and sepsis were independently predictive of PHT. Mortality was significantly higher in the PHT group (26.2% versus 4.1%; P<0.0001) compared to the control group. Low birth weight, severe intraventricular hemorrhage and male sex were significantly associated with death in infants with PHT. Thirty-seven percent (23/61) of infants with PHT were treated with inhaled NO. Infants <29-week GA had poor response to iNO and the response to iNO increased with GA (P<0.02).Conclusions:Low Apgar scores, oligohydramnios and pulmonary hypoplasia are associated with the development of PHT in premature infants. The percentage of infants responding to iNO increases with advancing GA.

Methemoglobin to cumulative nitric oxide ratio and response to inhaled nitric oxide in PPHN

Background:One-third of infants with persistent pulmonary hypertension of the newborn (PPHN) do not respond to inhaled nitric oxide (iNO). If iNO is not delivered to the pulmonary vasculature because of parenchymal lung disease, it cannot interact with hemoglobin to form methemoglobin (MHb).Objective:To study the correlation between oxygenation response to iNO in infants with PPHN secondary to parenchymal lung disease and initial MHb% to cumulative NO exposure (ppm × hours) ratio (MHb/ΣNO).Study Design:Retrospective chart review of neonates with PPHN secondary to parenchymal lung disease treated with iNO comparing non-responders (PaO2/FiO2 ratio<10 change with iNO) with responders (⩾10 change).Result:Non-responders (n=16) had a PaO2/FiO2 of 83±48 (mean±s.d.) and decreased to 74±44 after iNO. PaO2/FiO2 increased from 70±48 to 151±63 with iNO among responders (n=36). The MHb/ΣNO ratio was low (0.024±0.012) among non-responders compared with responders (0.07±0.053, P<0.005).Conclusion:Inadequate oxygenation response to iNO is associated with lower MHb/ΣNO, suggesting suboptimal delivery of iNO to the pulmonary vasculature.

White blood cell left shift in a neonate: a case of mistaken identity

We present a full-term male infant who presented with tachypnea and an increased band count on his complete blood count (CBC) with an immature to total neutrophil (I:T) ratio of 0.6 raising suspicion of early onset sepsis. A blood culture was drawn and he was started on appropriate antibiotics. The patients clinical condition rapidly improved; however, the white cell count ‘left shift’ persisted. When a detailed family history was obtained, it was discovered that the father, paternal uncle and the grandfather had been diagnosed with Pelger-Huet anomaly (PHA). As the urine, blood and CSF cultures were all negative in this now well-appearing infant, the left shift on the CBC was believed to be due to inheritance of the PHA. We present this case to emphasize that even in this age of sophisticated laboratory evaluation, a good clinical history, including family history, and clinical evaluation, are essential for accurate diagnosis.