Lactate, glucose and the neonatal brain: it's time to challenge the paradigm

Glucose-to-lactate ratio and neurodevelopment in infants with hypoxic-ischemic encephalopathy: an observational study

We aimed to assess the glucose and lactate kinetics during therapeutic hypothermia (TH) in infants with hypoxic-ischemic encephalopathy and its relationship with longitudinal neurodevelopment. We measured glucose and lactate concentrations before TH and on days 2 and 3 in infants with mild, moderate, and severe hypoxic-ischemic encephalopathy (HIE). Neurodevelopment was assessed at 2 years. Participants were grouped according to the neurodevelopmental outcome into favorable (FO) or unfavorable (UFO). Eighty-eight infants were evaluated at follow-up, 34 for the FO and 54 for the UFO group. Severe hypo- (< 2.6 mmol/L) and hyperglycemia (> 10 mmol/L) occurred in 18% and 36% from the FO and UFO groups, respectively. Glucose-to-lactate ratio on day 1 was the strongest predictor of unfavorable metabolic outcome (OR 3.27 [Formula: see text] 1.81, p = 0.032) when adjusted for other clinical and metabolic variables, including Sarnat score.

CONCLUSION

Glucose-to-lactate ratio on day 1 may represent a new risk marker for infants with HIE undergoing TH.

WHAT IS KNOWN

• Glucose and lactate are key metabolic fuels during neonatal hypoglycemia. This suggests that their concentrations may influence the neurodevelopmental outcome of neonates experiencing hypoxic-hischemic encephalopathy (HIE).

WHAT IS NEW

• We describe the relative availbility of glucose and lactate before and during theraputic hypothermia in neonates with HIE.

Cerebral Lactate Concentration in Neonatal Hypoxic-Ischemic Encephalopathy: In Relation to Time, Characteristic of Injury, and Serum Lactate Concentration

Background

Cerebral lactate concentration can remain detectable in neonatal hypoxic-ischemic encephalopathy (HIE) after hemodynamic stability. The temporal resolution of regional cerebral lactate concentration in relation to the severity or area of injury is unclear. Furthermore, the interplay between serum and cerebral lactate in neonatal HIE has not been well defined. The study aims to describe cerebral lactate concentration in neonatal HIE in relation to time, injury, and serum lactate.

Design/methods

Fifty-two newborns with HIE undergoing therapeutic hypothermia (TH) were enrolled. Magnetic resonance imaging and spectroscopy (MRI + MR spectroscopy) were performed during and after TH at 54.6 ± 15.0 and 156 ± 57.6 h of life, respectively. Severity and predominant pattern of injury was scored radiographically. Single-voxel ¹H MR spectra were acquired using short-echo (35 ms) PRESS sequence localized to the basal ganglia (BG), thalamus (Thal), gray matter (GM), and white matter. Cerebral lactate concentration was quantified by LCModel software. Serum and cerebral lactate concentrations were plotted based on age at time of measurement. Multiple comparisons of regional cerebral lactate concentration based on severity and predominant pattern of injury were performed. Spearman's Rho was computed to determine correlation between serum lactate and cerebral lactate concentration at the respective regions of interest.

Results

Overall, serum lactate concentration decreased over time. Cerebral lactate concentration remained low for less severe injury and decreased over time for more severe injury. Cerebral lactate remained detectable even after TH. During TH, there was a significant higher concentration of cerebral lactate at the areas of injury and also when injury was more severe. However, these differences were no longer observed after TH. There was a weak correlation between serum lactate and cerebral lactate concentration at the BG (r_s = 0.3, p = 0.04) and Thal (r_s = 0.35, p = 0.02). However, in infants with moderate-severe brain injury, a very strong correlation exists between serum lactate and cerebral lactate concentration at the BG (r_s = 0.7, p = 0.03), Thal (r_s = 0.9 p = 0.001), and GM (r_s = 0.6, p = 0.04) regions.

Conclusion

Cerebral lactate is most significantly different between regions and severity of injury during TH. There is a moderate correlation between serum and cerebral lactate concentration measured in the deep gray nuclei during TH. Differences in injury and altered regional cerebral metabolism may account for these differences.