Monitoring treatment of delayed cerebral ischaemia in unconscious patients after aneurysmal subarachnoid haemorrhage: a prospective multimodal neuromonitoring study

Background: Aneurysmal subarachnoid haemorrhage (SAH) is a life-threatening condition with high morbidity. Delayed cerebral ischaemia (DCI) significantly contributes to secondary injury and poor outcomes. While perfusion CT (CTP) aids DCI detection, multimodal neuromonitoring-including brain tissue oxygenation (PtiO2) and cerebral microdialysis-offers superior temporal resolution. Its value in guiding treatment remains underexplored. Methods: This prospective cohort study included SAH patients monitored with multimodal neuromonitoring at RWTH Aachen University Hospital (2014-2020). DCI was diagnosed with neuromonitoring abnormalities and confirmed by CTP. First-line treatment involved induced hypertension, with endovascular rescue treatment for refractory cases. Physiological data were time-aligned to treatment onset and aggregated into hourly summaries. Binomial logistic regression identified predictors of favourable 1-year outcome (modified Rankin Scale 0-3). Results: Of 56 patients with confirmed DCI, correctly placed probes and available outcome data, 22 (39.3%) achieved favourable outcome. These patients showed greater post-treatment reductions in pressure reactivity index (PRx) and lactate-to-pyruvate ratio (LPR). In multivariable analysis, greater PRx reduction was significantly associated with favourable outcome (OR 0.023, 95% CI 0.001 to 0.394, p=0.009), translating to a 46.5% increase in odds per 0.1-unit decrease. Greater LPR reductions were also predictive (OR 0.950, 95% CI 0.904 to 0.998, p=0.042), with a 5-unit drop linked to a 29.3% increase in odds. Although PtiO2₂ improved post-treatment, it was not associated with outcome. Conclusion: PRx and LPR reflect meaningful physiological responses to DCI treatment and are associated with 1-year outcomes. Multimodal neuromonitoring may support not only diagnosis but also treatment monitoring and decision-making in unconscious SAH patients.