We hypothesized that enteral doxapram would effectively treat apnea of prematurity without the appearance of major side effects. Of 16 infants, 10 (BW 1,520 ± 102 g) received doxapram alone and 6 (BW 1,020 ± 35 g) received doxapram plus theophylline. Apneas decreased from 16.7 ± 1.9 to 2.1 ± 0.6 in infants receiving doxapram alone, and from 38.2 ± 4.4 to 7.9 ± 2.2 apneas/24 h in those receiving doxapram plus theophylline. This was associated with an increase in alveolar ventilation, a shift of the ventilatory response to CO₂ to the left, and no change in the immediate ventilatory response to 100% oxygen. Side effects included premature teeth buds corresponding to the lower central incisors, prevalence of occult blood in stool and necrotizing enterocolitis. The findings suggest that doxapram effectively controls apnea when given enterally, but should be used cautiously because of potentially harmful side effects.

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Intravenous lipid infusion has been previously reported to be associated with hypoxemia. Different mechanisms have been proposed, but none have explored the decrease in respiratory quotient (RQ) following lipid administration as a possible factor. Ten neonates without respiratory problems, breathing room air and on total parenteral nutrition were studied. Arterialized capillary blood gases, transcutaneous PO(2) (TcPO(2)) measurements and expired gas concentrations were obtained, prior to and 1 g/kg of 10% lipid emulsion was infused over 6 h. Following lipid infusion, the TCPO(2) decreased from 72 ± 8 to 65 ± 8 mm Hg and the RQ decreased from 0.94 ± 0.08 to 0.86 ± 0.5 (p < 0.05), while the pH, PaCO(2) and the alveolar-arterial oxygen tension difference did not change. The decrease in TcPO(2) significantly correlated with the decrease in alveolar oxygen tension. Seven of the 10 infants had a significant decrease in TCPO(2) with a significant decrease in RQ from 0.98 ± 0.05 to 0.85 ± 0.06 (p < 0.01). In 3 patients with no significant change in TcPO(2) following intralipid administration, the RQ was initially significantly lower than the rest of the group (0.85 ± 0.04; p < 0.05) and did not change at the end of the infusion (0.88 ± 0.03). These data suggest that the changes in PaCO(2) following lipid infusion in neonates without lung disease and breathing room air, are related to the decrease in alveolar oxygen tension secondary to the change in RQ.