Impact of Intraoperative Hypotension and Blood Loss on Brain Damage Biomarkers in Metopic Craniosynostosis Surgery

Surgical correction of infant skull deformities often involves significant physiological stress and potential neurological risks. Prior research has shown that levels of the brain injury biomarkers glial fibrillary acidic protein (GFAP) and neurofilament light (NfL) are elevated postoperatively in infants undergoing surgery for craniosynostosis. These proteins serve as indicators of astrocytic damage and axonal injury, respectively, within the central nervous system. While their elevation suggests some degree of neuronal impact, the specific intraoperative triggers for these increases remain poorly defined in current pediatric literature. Clinicians suspect that hemodynamic instability, such as prolonged periods of low perfusion, or excessive hemorrhage might contribute to these biochemical changes. Understanding these relationships is vital because metopic synostosis repair requires extensive remodeling of the frontal bone and orbital rims. This absence of evidence motivated the current investigation into how surgical variables influence neural integrity markers.

This investigation sought to determine the correlation between intraoperative hypotension, surgical blood loss, and fluctuations in neural injury indicators. Researchers focused on identifying whether specific mean arterial blood pressure (MAP) thresholds predicted the release of Glial Fibrillary Acidic Protein (GFAP). The team also examined if the volume of blood lost during metopic synostosis repair influenced Neurofilament Light (NfL) concentrations. By analyzing these relationships, the study aimed to isolate hemodynamic factors from other potential causes of postoperative biomarker spikes. Establishing these links would help refine anesthetic management protocols for pediatric patients undergoing complex cranial vault procedures. The work specifically targeted the metopic synostosis population to ensure cohort homogeneity and reduce confounding variables from different suture involvements. Ultimately, the study intended to clarify if maintaining higher blood pressure targets could mitigate potential brain injury during these invasive reconstructions.

Investigators conducted a retrospective analysis of twenty consecutive patients who underwent open cranial vault procedures between January 2019 and September 2020. The clinical team extracted high-resolution data regarding heart rate and intraoperative blood pressure directly from electronic medical records. Hypotension was quantified using the area under the curve (AUC) for Mean Arterial Blood Pressure (MAP) at four distinct thresholds: 35, 40, 45, and 50 mm Hg. Laboratory personnel measured pre- and postoperative plasma concentrations of GFAP and NfL using stored blood samples from a previous trial. Statistical analysis utilized Spearman’s rank correlation (rs) to evaluate the strength of associations between hemodynamic variables and biomarker changes. The researchers normalized intraoperative blood loss by patient weight, expressing the values in milliliters per kilogram (mL/kg). This methodological approach allowed for a precise assessment of how the duration and depth of hypotension impacted the biochemical markers of neural health.

The study found no significant association between plasma NfL or GFAP levels and any of the tested Mean Arterial Blood Pressure (MAP) thresholds. Specifically, the correlation coefficients for NfL at MAP thresholds of 40, 45, and 50 mm Hg were 0.08, 0.15, and 0.30, respectively. Similarly, GFAP showed negligible correlations with these pressure limits, yielding values of -0.17 at 40 mm Hg and -0.06 at 50 mm Hg. Intraoperative blood loss averaged 27±11 mL/kg across the cohort but did not correlate with biomarker elevation (NfL rs=0.26, GFAP rs=-0.15). The average age of the included infants was 190±65 days, with a mean weight of 8.0±1.0 kg. These data points indicate that neither low blood pressure nor blood volume depletion directly caused the observed neural marker increases. The lack of statistical significance across all four AUC thresholds suggests that the brain injury markers respond to different physiological or mechanical stimuli.

The findings suggest that factors other than hemodynamic instability likely drive the elevation of brain injury biomarkers in this surgical context. Mechanical manipulation of the skull or underlying neural tissues during the open cranial vault procedure may represent a more significant contributor to protein release. Future research should explore the impact of direct surgical trauma or intracranial pressure changes on GFAP and NfL levels. Although the current results are limited by a small sample size, they provide a foundation for optimizing pediatric neurosurgical care. Clinicians should continue to monitor these markers while considering a broader range of intraoperative stressors beyond simple blood pressure management. Refining the understanding of these biomarkers will eventually lead to safer surgical techniques for infants with metopic synostosis. Long-term neurodevelopmental follow-up is necessary to determine if these transient biomarker elevations correlate with functional outcomes in children.