Initial Paco₂ Values at One Hour in Very Low-Birthweight Infants(VLBW)< 1000g and Oxygen Requirement at 28 days: Are Delivery Room Events Important? † 1122

Recent observational studies suggest a relationship between low Paco2 values in the mechanically ventilated VLBW infants and neonatal morbidity, i.e., chronic lung disease. Permissive hypercapnia has been advocated as one approach to minimize such lung injury. However, the time of initiating such a strategy and factor (s) that influence postnatal Paco₂ values are not well characterized. The study objective was to determine the effect of delivery room resuscitation on early Paco₂ levels and the relation to O₂ requirement at 28 days in VLBW infants<1000g. Between Jan 95- June 97, the medical records of 102 infants of BW 803±126g, GA 26.6± 1.56W were reviewed. Exclusion criteria included early deaths(n=7), congenital anomalies (n=2). Associated perinatal events included any antenatal steroids (AS) (n=33), multiple gestation (n=11), pregnancy-induced hypertension (n=9), abruption (n=3). Mode of delivery was vaginal (n=37), C/S(n=46), emergent C/S (n=10). Delivery room interventions included bag and mask ventilation and intubation (n=87), bag and mask ventilation and CPAP (n=6), CPR (n=6); 74% were readily intubated, 26% required multiple attempts. The 5 minute Apgar <5 (n=6), cord PH <7.00 (n=3). The initial Paco₂ obtained at ≈1hr after birth (always prior to surfactant administration) was <30 (n=19, 20%) (m=24±3.7mmHg), <35 (n=33, 35%)(m=27.7±4.7mmHg), >40 (n=42, 43%) (m=46.8±6.3mmHg), ≥45(n=23, 24%) (m=50.6±6.4mmHg). 19 patients (20%) had Paco₂ <35 mmHg (m=28±4mmHg) at ≈3hrs of life. Forty-five infants received surfactant and 62 infants required O₂ at 28 days. Initial Paco₂ levels were not related to AS, mode of delivery, Apgar scores, intubation attempts, cord parameters, BW, GA, initial ventilatory support or subsequent surfactant therapy. Initial Paco₂ values for AS vs non steroid singleton infants were 39±9 vs 39±7.4mmHg (P>0.05) respectively. The lowest Paco₂ values were following abruption(m=23±7mmHg) and multiple gestation (m=32±12mmHg). Of infants with Paco₂<35mmHg at one hour, 25/33 (76%) vs 10/23 (44%) of infants with Paco₂≥45 group required O₂ at 28 days(p<0.03). At 3 hours of age 16/19 (84%) infants with Paco₂<35mmHg vs 14/27 (52%) with Paco₂≥45mmHg required O₂ at 28 days(p<0.01). These data indicate that approximately one-third of VLBW have low Paco₂ values upon NICU admission. Infants with a low Paco₂ within the first hour of life are more likely to require O₂ at 28 days compared to infants with relatively higher initial Paco₂ values. Delivery room resuscitative events likely contribute to the low Paco₂, although the specific mechanism (s) are not clear from this observational study. Any strategy designed to promote permissive hypercapnia should include optimizing delivery room resuscitation.