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The Effect of Arterial pH on Oxygenation Persists Even in Infants Treated with Inhaled Nitric Oxide
Aimee M Barton1, M Kabir Abubakar, Jennifer Berg
1Department of Pediatrics, Georgetown University Hospital, 3800 Reservoir Road NW, M3400, Washington, DC 20007, USA.
Insights
Optimizing pH is crucial for inhaled nitric oxide (iNO) effectiveness in infants with persistent pulmonary hypertension of the newborn (PPHN). This study found that infants unresponsive to iNO often had suboptimal pH levels.
Area of Science:
- Neonatal Medicine
- Pediatric Pulmonology
- Critical Care
Background:
- Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator used in neonates.
- The effectiveness of iNO can be influenced by various physiological factors.
- The impact of acid-base balance, specifically pH, on iNO response requires further investigation.
Purpose of the Study:
- To validate the clinical observation that pH significantly affects oxygenation in infants treated with iNO.
- To determine the correlation between pH levels and the efficacy of iNO therapy.
Main Methods:
- Retrospective chart review of 51 infants receiving iNO.
- Data collected included demographics, ventilator settings, arterial blood gases (ABG), and interventions.
- Analysis involved linear regression to assess the relationship between pH and the arterial/alveolar (a/A) ratio, the primary outcome measure.
Main Results:
- Thirty-one out of 51 infants (61%) showed a clear responsiveness to pH.
- Mean airway pressure (MAP) and mean blood pressure (MBP) did not correlate with the a/A ratio.
- Infants requiring extracorporeal membrane oxygenation (ECMO) were less likely to exhibit pH responsiveness.
Conclusions:
- Failure to optimize pH may explain unresponsiveness to iNO in some infants.
- Maintaining a pH above 7.5 through hyperventilation is not advised due to potential risks.
Abstract:
Objective. To validate the empiric observation that pH has an important effect on oxygenation in infants receiving iNO. Study Design. Demographics, ventilator settings, arterial blood gases (ABG), and interventions for up to 96 hours of life were extracted from the charts of 51 infants receiving iNO. Need for ECMO and survival to discharge were noted. Mean blood pressure (MBP) and mean airway pressure (MAP) were recorded. The arterial/alveolar (a/A) ratio was used as the primary outcome. Analysis was by simple linear regression and multiple linear regression analyses and Fisher's exact test. pH responsiveness was arbitrarily defined as a correlation coefficient (CC) of >0.40 with P < 0.05. Results. Mean gestational age was 38.8 weeks and mean birth weight was 3300 g. All patients had clinical diagnosis of PPHN. Clear responsiveness to pH was found in 31/51 infants. MAP and MBP did not correlate with a/A ratio. Three responders had a critical pH > 7.55. Of 11 patients requiring ECMO, only 3 exhibited responsiveness at any time in their course. Three responders required ECMO. Conclusion. This small study suggests that failure or inability to optimize pH may account for observed unresponsiveness to iNO. Maintaining a pH > 7.5 using hyperventilation is not recommended.
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