Fig. 5: Comparison of blood-based neurologic biomarkers taken before WLST and during the dying process.

a, Blood-based neurologic biomarkers were taken from the radial artery and internal jugular vein to allow for arteriovenous gradient analysis across the cerebral circulation. Timing data are presented as medians (Q1, Q3) for the IQR. b, Biospecimens were collected before WLST (pre) and from when SBP was <60 mm Hg (post). Biomarkers were analyzed for common markers of astrocyte, axonal and neuron cell body injury. c–r, Arterial (c, g, k and o), jugular venous (d, h, l and p) and cerebral arteriovenous (AV) gradients (e, i, m and q) were pairwise compared using two-way Wilcoxon signed-ranks tests and Wilcoxon effect sizes. These data are presented on a log₁₀ scale (c–e, g–i, k–m and o–q). The box plots are presented as the five-number summary (minima, Q1, median, Q3 and maxima) with the white diamond on top of each box plot representing each group mean. Only arterial Nf-L was elevated following ischemia of the dying process (g). Subsequent postmortem analysis of the brain confirmed presence of astrocyte (f), axonal (j and n) and neuron cell body (r) injury. Scale bars, 20 µm. Many brain autopsies had substantial amounts of neurons with eosinophilic cytoplasm and shrunken nuclei typical of cases with ischemic brain injury (r). s, Arterial plasma proteomics for the critically ill patient cohort and healthy controls were assessed for normality by Shapiro–Wilkes tests then compared using either two-way unpaired t-tests (normal distribution) or two-way Mann–Whitney U tests (non-normal distribution) then corrected for the false discovery rate. Arterial plasma proteomic analysis indicated severe central nervous system injury in the critically ill patient cohort compared with healthy controls before WLST. t, Arterial plasma biomarker changes from pre to post in the critically ill patient group were assessed for normality by Shapiro–Wilkes tests then compared using either two-way paired t-tests (normal distribution) or two-way Wilcoxon signed-rank tests. Arterial plasma biomarkers were relatively unchanged throughout the dying process in the critically ill patient cohort. The effect size was calculated as either Cohen’s d (normal distribution) or Wilcoxon (non-normal distribution) effect sizes (s and t). AV, arterial-venous; GFAP, glial fibrillary acidic protein; Nf-L/NEFL, neurofilament light chain; PEA, pulseless electrical activity; UCH-L1, ubiquitin carboxyl-terminal hydrolase L1. Panels a and b created with BioRender.com.

Source data.