Infection and other clinical correlates of abnormal heart rate characteristics in preterm infants

Abstract

Objective: To identify clinical conditions associated with a large increase (spike) in the heart rate characteristics index in very low birth weight (VLBW) infants.

Study design: Retrospective medical record review within a day of all large heart rate characteristics index spikes (increase of ≥3 from the previous 5-day average) in VLBW infants at a single center enrolled from 2007 to 2010 in a multicenter trial of heart rate characteristics monitoring. In the trial, infants were randomized to having their heart rate characteristics index displayed to clinicians or not displayed.

Results: Of 274 eligible infants, 224 large heart rate characteristics spikes occurred in 105 infants. Thirty-three spikes were associated with surgery or procedures requiring anesthetic or anticholinergic medications, and infection-related conditions were the most common clinical association with the other spikes. Of the first spikes in 47 infants randomized to conventional monitoring (heart rate characteristics index not displayed to clinicians), 53% were associated with suspected or proven infection. Respiratory deterioration without suspected infection occurred with 34%, and no association was identified in 13%. Infants randomized to having their heart rate characteristics index displayed were more likely to have antibiotics initiated around the time of a large heart rate characteristics index spike.

Conclusions: Sepsis, other infectious or systemic inflammatory conditions, respiratory deterioration, and surgical procedures are the most common clinical associations with a large increase in the heart rate characteristics index in VLBW infants. This information may improve use of heart rate characteristics monitors in patients in the neonatal intensive care unit.

Trial registration: ClinicalTrials.gov NCT00307333.

Conflict of interest statement

The other authors declare no conflicts of interest.

Copyright © 2014 Mosby, Inc. All rights reserved.

Figures

Figure 1. heart rate characteristics index monitor showing normal and abnormal heart rate characteristics

The heart rate characteristics monitor analyzes electrocardiogram signals from bedside monitors for abnormal heart rate characteristics of decreased variability and transient decelerations and presents a number which is the fold increased risk an infant will experience a clinical deterioration consistent with sepsis in the next 24 hours. The monitor displays the last 5 days of the heart rate characteristics index (top, orange) and the last 30 minutes of heart rate (bottom, green, beats per minute). A) Normal heart rate characteristics reflected by a low heart rate characteristics index. The current index, 0.88, is shown in the top right panel, and the 5-day trend is generally

Figure 2. Clinical correlations of the first non-surgical heart rate characteristics index spike in non-display infants

Forty-seven very low birth weight infants with the heart rate characteristics index continuously monitored but not displayed to clinicians had at least one large heart rate characteristics index spike of 3 over the prior 5 day average that was not associated with a surgical procedure. Clinical associations with the first spike were blood culture positive sepsis, sepsis suspected but ruled out (negative cultures, 5 days antibiotics), urinary tract infection, necrotizing enterocolitis, and respiratory deterioration without antibiotics initiated. In 13% of cases, the cause of the spike could not be identified