Amount and Burden of Brain Tissue Hypoxia to Determine Clinical Efficacy of Secondary Decompressive Craniectomy After Moderate/Severe Traumatic Brain Injury

BACKGROUND AND OBJECTIVES: Optimal timing and patient selection for secondary decompressive craniectomy (DC) in traumatic brain injury (TBI) with refractory intracranial hypertension remain uncertain. Surgical indication is primarily based on intracranial pressure (ICP), without routinely incorporating brain tissue oxygen tension (PbtO2). Whether the severity and duration of cerebral hypoxia improve prognostic stratification for DC is unclear. We aimed to determine whether hypoxic burden and composite ischemic metrics integrating ICP and PbtO2 are associated with 6-month neurological outcome in patients with TBI undergoing secondary DC. METHODS: This retrospective study included 45 adults with isolated moderate-to-severe TBI who underwent DC for refractory intracranial hypertension (ICP >25 mm Hg for >60 minutes despite second-tier therapy) at 2 neurocritical care units. Continuous ICP and PbtO2 monitoring was performed. Hypoxic burden was defined as the duration and percentage of time spent with PbtO2 <15 mm Hg. Ischemic burden was calculated as pre-DC ICP × % time with PbtO2 <15 mm Hg. Outcome at 6 months was assessed using the Glasgow Outcome Scale (favorable 4-5 vs unfavorable 1-3). RESULTS: Thirty patients (67%) achieved a favorable outcome. Favorable outcome was associated with higher admission PbtO2, shorter hypoxia duration (7.5 vs 15 hours, P = .017), and lower hypoxic burden (12.8% vs 70%, P < .001). Ischemic burden demonstrated good discrimination (area under the curve 0.831). In multivariable analysis using Firth penalized-likelihood logistic regression, greater change in PbtO2 (postadmission) independently predicted a favorable outcome (odds ratio 1.30 per mm Hg, P < .001), whereas higher ischemic burden was strongly associated with worse outcome (odds ratio 0.15 per 1-SD, P < .001). CONCLUSION: Severity and duration of cerebral hypoxia, particularly when integrated with ICP into an ischemic burden metric, are strongly associated with outcome after DC and may improve patient selection and timing for secondary decompression.