Recovery from bradycardia and desaturation events at 32 weeks corrected age and NICU length of stay: an indicator of physiologic resilience?

Abstract

Background: Preterm very low birth weight (VLBW) infants experience physiologic maturation and transitions off therapies from 32 to 35 weeks postmenstrual age (PMA), which may impact episodic bradycardia and oxygen desaturation. We sought to characterize bradycardias and desaturations from 32 to 35 weeks PMA and test whether events at 32 weeks PMA are associated with NICU length of stay.

Methods: For 265 VLBW infants from 32 to 35 weeks PMA, we quantified the number and duration of bradycardias (HR <100 for ≥4 s) and desaturations (SpO₂ <80% for ≥10 s) and compared events around discontinuation of CPAP, caffeine, and supplemental oxygen. We modeled associations between clinical variables, bradycardias and desaturations at 32 weeks PMA, and discharge PMA.

Results: Desaturations decreased from 60 to 41 per day at 32 and 35 weeks, respectively (p < 0.01). Duration of desaturations and number and duration of bradycardias decreased to a smaller extent (p < 0.05), and there was a non-significant trend toward increased desaturations after stopping CPAP and caffeine. Controlling for clinical variables, longer duration of bradycardias and desaturations at 32 weeks PMA was associated with later discharge PMA.

Conclusion: Delayed recovery from bradycardias and desaturations at 32 weeks PMA, perhaps reflecting less physiologic resilience, is associated with prolonged NICU stay for VLBW infants.

Figure 1:. Number and duration of bradycardia and desaturation events at 32 and 35 weeks PMA by sex.

Median daily number and duration of desaturations at 32 weeks PMA (32 0/7 to 32 6/7) and 35 weeks PMA (35 0/7 to 35 6/7) are shown as filled symbols (panels A and B); triangles for males, squares for females. Bradycardia number and duration at 32 and 35 weeks PMA are shown as open symbols (panels C and D). Error bars indicate interquartile range.

Figure 2:. Trends in bradycardia and desaturation events after CPAP, caffeine, and supplemental oxygen discontinuation.

Median number of bradycardias (solid lines) and desaturations (dashed lines) are shown from 3 days before until 13 days after discontinuation of CPAP (panel A), caffeine (panel B), and supplemental oxygen (panel C).

Figure 3:. Association between duration of bradycardia and desaturation events at 32 weeks and discharge PMA.

Scatter plot, with one point for each of the 265 infants, demonstrating a positive linear relationship between PMA at discharge and average duration of desaturations (panel A) and bradycardias (panel B) at 32 weeks PMA. The solid line indicates the fitted linear model and grey shading indicates the 95% confidence interval around the trend.