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Variability of cerebral hemoglobin concentration in very preterm infants during the first 6 hours of life
Insights
Cerebral hemoglobin concentration (cHbc) in preterm infants varies significantly. Physiological factors like birth weight and gestational age, not just measurement methods, explain most of this early-life variability.
Area of Science:
- Neonatal physiology
- Cerebral hemodynamics
- Medical instrumentation
Background:
- Cerebral hemoglobin concentration (cHbc) is crucial for brain oxygen transport.
- Significant variability in cHbc exists in neonates, influenced by multiple factors.
- Understanding cHbc variability is vital for managing preterm infants.
Purpose of the Study:
- To quantify the contributions of physiological and methodological factors to cHbc variability in very preterm infants.
- To assess the role of near-infrared spectrophotometry (NIRS) in monitoring early cHbc.
Main Methods:
- Near-infrared spectrophotometry (NIRS) was used to continuously monitor cHbc in 28 very preterm infants.
- A stepwise regression model analyzed 13 independent variables against cHbc.
- The study focused on the first 6 hours of postnatal life.
Main Results:
- The total cHbc variability was +/- 14.1 micromol/l.
- Methodological factors accounted for only 26% (3.7 micromol/l) of the variability.
- Physiological variables (birth weight, gestational age, blood glucose, transcutaneous CO2) explained 66% (9.3 micromol/l) of the variability.
Conclusions:
- Near-infrared spectrophotometry (NIRS) is a valid method for measuring cHbc in very preterm infants.
- Early cHbc variability is predominantly driven by physiological factors rather than measurement methodology.
- Continuous NIRS monitoring aids in understanding cerebral oxygenation in neonates.
Abstract:
Cerebral hemoglobin concentration (cHbc), a major determinant of oxygen transport capacity in the brain, shows a considerable variability due to physiological and methodological factors. In order to determine the (relative) contribution of these factors, the cHbc variability within the first 6 hours of life was studied in 28 very preterm infants using near infrared spectrophotometry (NIRS). Mean cHbc values were 46.4 +/- 14.1 micromol/l (2.75 +/- 0.84 ml/100 g). Is the variability in cHbc related to the methodology of cHbc measurements or to physiological variables? A statistical model of stepwise regression (backward selection) with 13 independent variables and with cHbc as a dependent variable showed that, from the total variability of +/- 14.1 micromol/l, only 3.7 micromol/l (26%) were of methodological origin, while the major portion, 9.3 micromol/l (66%) were related to four physiological variables: birth weight, gestational age, blood glucose and transcutaneous carbon dioxide tension. The remaining 1.1 micromol/l (7.8%) were unexplained. We conclude that NIRS, which allows continuous monitoring of cerebral oxygenation and metabolism even in the first hours of postnatal life, is a valid technique to measure cHbc in very preterm infants. The major portion of the large variability of early cHbc registrations can be attributed to physiological factors.
