Cerebrospinal fluid and plasma ascorbate concentrations following subarachnoid haemorrhage

Background: Ascorbate, the biologically active form of vitamin C, is the primary neural anti-oxidant. Ascorbate concentrations have never been quantified following aneurysmal subarachnoid haemor-rhage (aSAH).Objective: To quantify plasma and cerebrospinal fluid (CSF) ascorbate concentrations in patients following SAH.Design, Setting,Participants, Main Outcome Measures: Cohort study in which plasma and CSF ascor-bate concentrations were measured longitudinally in 12 aSAH patients admitted to a quaternary referral intensive care unit and compared to one-off samples obtained from 20 pregnant women prior to delivery in a co-located obstetric hospital. Data are median [interquartile range] or median (95 % confidence intervals).Results: Forty-eight plasma samples were obtained from the 12 aSAH patients (eight females, age 62 [53-68] years). Eight participants with extra-ventricular drains provided 31 paired CSF-plasma samples. Single plasma and CSF samples were obtained from 20 pregnant women (age 35 [31-37] years). Initial plasma and CSF ascorbate concentrations post aSAH were less than half those in pregnant controls (plasma: aSAH: 31 [25-39] mu mol/L vs. comparator: 64 [59-77] mu mol/L; P < 0.001 and CSF: 116 [80-142] mu mol/L vs. 252 [240-288] mu mol/L; P < 0.001). Post aSAH there was a gradual reduction in the CSF:plasma ascorbate ratio from-4:1 to-1:1. Six (50 %) patients developed vasospasm and CSF ascorbate concen-trations were lower in these patients (vasospasm: 61 (25, 97) vs. no vasospasm: 110 (96, 125) mu mol/L; P 1/4 0.01).Conclusion: Post aSAH there is a marked reduction in CSF ascorbate concentration that is most prom-inent in those who develop vasospasm.(c) 2023 The Authors. Published by Elsevier B.V. on behalf of College of Intensive Care Medicine of Australia and New Zealand. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).