Evolution of early cerebralNIRSin hypoxic ischaemic encephalopathy

Abstract

Aim: To describe early cerebral oxygenation (cSO 2 ) and fractional tissue oxygen extraction (FTOE) values and their evolution over the first days of life in infants with all grades of hypoxic-ischaemic encephalopathy (HIE) and to determine whether cSO 2 and FTOE measured early (6 and 12 h) can predict short-term outcome.Methods: Prospective, observational study of cerebral near-infrared spectroscopy (NIRS) in infants >36 weeks' gestation with HIE. Ten one-hour epochs of cSO 2 and FTOE were extracted for each infant over the first 84 h. Infants with moderate and severe HIE received therapeutic hypothermia (TH). Abnormal outcome was defined as abnormal magnetic resonance imaging (MRI) and/or death.Results: Fifty-eight infants were included (28 mild, 24 moderate, 6 severe). Median gestational age was 39.9 weeks (IQR 38.1-40.7) and birthweight was 3.35 kgs . cSO 2 increased and FTOE decreased over the first 24 h in all grades of HIE. Compared to the moderate group, infants with mild HIE had significantly higher cSO 2 at 6 h (p = 0.003), 9 h (p = 0.009) and 12 h (p = 0.032) and lower FTOE at 6 h (p = 0.016) and 9 h (0.029). cSO 2 and FTOE at 6 and 12 h did not predict abnormal outcome. Conclusion:Infants with mild HIE have higher cSO 2 and lower FTOE than those with moderate or severe HIE in the first 12 h of life. cSO 2 increased in all grades of HIE over the first 24 h regardless of TH status.

The Use of Cerebral Near-Infrared Spectroscopy in Neonatal Hypoxic-Ischemic Encephalopathy

“…This study concluded that a rate of rise between 0.5% and 0.7% per hour is associated with moderate to severe brain injury on MRI at 14 days of life 20. This is further supported by research by Garvey et al,19 who also observed a correlation between rScO 2 and the grade of HIE 19. Infants with moderate HIE had a steeper rate of rise than infants with mild HIE, but a slower rate of rise than infants with severe HIE 19.…”

“…20 This is further supported by research by Garvey et al, 19 who also observed a correlation between rScO 2 and the grade of HIE. 19 Infants with moderate HIE had a steeper rate of rise than infants with mild HIE, but a slower rate of rise than infants with severe HIE. 19 Additionally, it was noted that infants with severe HIE exhibit a rate of rise that is almost linear.…”

“…It was observed that rScO 2 increased in the first 20 hours for all infants, regardless of HIE grade 19. This initial rise may be attributed to the impact encephalopathy has on cerebral perfusion, regardless of if the infant receives TH 19. Unique patterns in rScO 2 trends were observed in each grade of HIE.…”

“…19 Infants with moderate to severe HIE demonstrated rScO 2 values trending above those of healthy term newborns. 19 The rate of rise of rScO 2 may be another indication to differentiate HIE grades. Jain et al 20 observed patterns of rScO 2 trends that differed greatly between severity of brain injury as later detected by MRI; rScO 2 increased by 0.20% per hour for normal or mildly abnormal outcomes, by 0.48% per hour for moderately abnormal outcomes, and by 0.68% per hour for severely abnormal outcomes (P = .05).…”

Optimal neuromonitoring techniques in neonates with hypoxic ischemic encephalopathy

“…As a surrogate for cerebral blood flow, the chronologic evolution of rScO2 may be an important bedside measure and further serve as a prognostic tool ( 40 ). While therapeutic hypothermia itself contributes to vasoconstriction and decreased cerebral blood flow, this effect is mitigated by a larger decrease in metabolic demand, subsequently resulting in higher rScO2 and lower fTOE ( 41 , 42 ) ( Figure 5 ). After initiation of cooling, a modest increase in rScO2 is typically seen due to these effects.…”