Chapter 20 - Heart Rate and Cardiorespiratory Analysis for Sepsis and Necrotizing Enterocolitis Prediction

Abstract

The goal of predictive monitoring is to predict or detect adverse events far enough in advance of conventional detection methods to allow for earlier treatment and improved outcomes. The first example of a commercially available predictive monitoring system for neonatal intensive care unit patients is the heart rate characteristics (HRC) index monitor, which analyzes heart rate patterns for signs of incipient illness. The three HRC identified in preterm infants with sepsis and incorporated into the HRC index algorithm are decreased variability, increased sample asymmetry toward more decelerations and fewer accelerations, and decreased sample entropy, a measure of signal complexity. In real time, the monitor runs the algorithm on the prior 4096 heartbeats, and then averages 12 hours of data to calculate and display a score that was validated to be the fold-increased risk of clinical deterioration from sepsis in the next 24 hours. In a large randomized clinical trial of 3003 very low birth weight infants, those with the score displayed to clinicians (with no mandate about when to start antibiotics) had significantly lower all-cause and sepsis-associated mortality compared with control infants. A limitation of the HRC index is that an elevated score is not specific for sepsis and may occur in other conditions associated with nonspecific inflammation such as respiratory failure and brain injury. Also, since it was developed as fold-increased risk and since the risk of sepsis diagnosis on any particular day is low, the positive predictive value of a high score for imminent diagnosis of sepsis is low. Nonetheless, this continuous physiomarker can be a useful tool for identifying some infants in the early stages of sepsis or necrotizing enterocolitis. Whether adding respiratory analysis or laboratory tests improves the diagnostic utility of HRC monitoring is a subject of current and future research.