169 - Progression of Blood Gas pH During the First hour of Life in Term and Near term Infant with Cord Gas pH ≤ 7.0

Blood gas pH is an important factor in determining eligibility for therapeutic hyperthermia. Among other criteria, a cord pH of ≤ 7.0 is used to guide the decision to initiate hypothermia. In the absence of cord blood pH, suggested algorithms would use a 1st hour gas pH ≤ 7.0 or use a 1st hour gas pH between 7.01-7.15 with additional criteria including 10 min Apgar ≤ 5, acute perinatal event, or findings of moderate to severe encephalopathy on physical exam.

During the first hour of life, a significant improvement on the blood gas pH may develop that may affect the eligibility and the decision to initiate therapeutic hypothermia. We hypothesized that in term and near-term infants with a cord pH of ≤ 7, a substantial number of these infants will have a significant improvement in their 1st hour gas pH from their cord pH enough to be misleading and make them ineligible for therapeutic hypothermia.

Objective:

To describe changes in gas pH between cord arterial sample and first hour infant arterial blood gas.

Design/Methods:

A 10-year retrospective chart review of infants with gestational age ≥35 weeks and cord gas < 7.0 and an admission 1^st hour arterial blood gas were included. Hypocarbia was defined as PaCo2 ≤35. A normal blood gas defined with pH >7.3 and PaCO2 >35.

Results:

102 infants had a cord pH < 7.0 with a mean gestational age of 38.8 ±1.9 and median 5-minute Apgar score of 6 (5,8). As a group 92/102 infants had 1^st hour pH >7.0 and 78/102 >7.15. A significant number of infants had hypocarbia, table 1. This did not differ with age of blood draw. Only 5/102 of blood gas met the definition of normal blood gas

Conclusion(s):

Conclusion: In infants with cord pH < 7.0, a significant number of 1^st hour blood gas pH was already above 7.0 and 7.15. A 1^st hour blood gas pH >  7.0 or 7.15 may miss a significant number of infants with initially low cord blood gas pH. These limits should be used with caution in deciding on the need for therapeutic hypothermia. However, a 1^st hour blood gas with pH >7.3 and PaCo2 >35 may reflect an absence of cord gas pH of 7.0. Similarly, this should be factored in when deciding on initiating therapeutic hypothermia.  Hypocarbia on 1^st hour blood gas is common and leads to an improved pH. This needs to be also factored in when deciding on initiating therapeutic hypothermia.