Hypothermia Makes Cerebral Resistance Index a Poor Prognostic Tool in Encephalopathic Newborns

Abstract

Background: Severe neonatal encephalopathy (NE) of hypoxic-ischaemic origin may cause death or life-long disability. Acute encephalopathy may also affect cerebrovascular control. Pourcelot's cerebrovascular resistance index (RI) ≤0.55 was predictive of poor outcome in normothermic NE infants. Recent studies have questioned its predictive power during therapeutic hypothermia (HT). Objective: To assess the predictive power of RI during HT and after rewarming. Methods: 45 infants with NE treated with HT for 72 h had their RI calculated during early (median 11 h) and late (median 62 h) cooling and after rewarming (median 89 h). Poor outcome was defined as death or abnormalities on day 10 magnetic resonance imaging shown to predict severe neuromotor disability. Results: RI ≤0.55 during cooling did not differentiate between good and poor outcome (late cooling, p = 0.08), but was powerful after rewarming (p = 0.004). RI ≤0.55 predicted true poor outcome in 43% (95% confidence interval (CI): 12, 80) during late cooling and in 100% (95% CI: 31, 100) after rewarming. RI >0.55 predicted good outcome in 86% (95% CI: 69, 95) during late cooling and in 89% (95% CI: 74, 96) after rewarming. Conclusions: Low RI is not predictive of poor outcome during HT in NE infants, but regains the predictive power seen in normothermic infants after rewarming.

Head Ultrasound in Neonatal Hypoxic-Ischemic Injury and Its Mimickers for Clinicians: A Review of the Patterns of Injury and the Evolution of Findings Over Time

“…If an RI is performed early enough after admission and before or simultaneous with the onset of TH, a low RI value may retain some of its prognostic value [30]. Its predictive value returns once the infant is rewarmed [31]. The reason for a loss of the predictive value of a low RI during TH is not well understood.…”

Reference Ranges for Neonatal Basal Ganglia Perfusion as Measured by Fractional Moving Blood Volume

“…There are a number of clinical circumstances where an assessment of regional perfusion could add to our understanding of pathophysiological changes in blood flow that put infants at risk of neurological injury [6,7]. Assessing changes in perfusion over time, such as during the transitional period after birth, or in circumstances when abnormal perfusion might be expected, such as after an ischaemic insult, requires a reference range for comparison.…”

Evaluating a Targeted Bedside Measure of Cerebral Perfusion in a Nonhuman Primate Model of Neonatal Hypoxic‐Ischemic Encephalopathy

“…The second hypothesis is that the hypothermia itself has a larger effect on perfusion of the thalamus than the anterior cerebral artery, and the change in the RI difference on day 4 was due to a return to normothermia at that time. Previous studies demonstrated decreased positive predictive values of the anterior cerebral artery RI for predicting death or severe disability when infants are undergoing hypothermia versus measurements obtained during normothermia . Because all 3 neonates in the hypothermia group developed our primary outcome of death or CP, we were unable to differentiate between these hypotheses in this study.…”