Intraoperative continuous cerebral microcirculation measurement in patients with aneurysmal subarachnoid hemorrhage: preliminary data on the early administration of magnesium sulfate

BACKGROUND: In patients with subarachnoid hemorrhage (SAH), vasospasm remains one of the major complications. The application of intravenous magnesium sulfate (MgSO(4)) has been under discussion to prevent cerebral ischemia. Our aim was to examine the impact of early MgSO(4) administration on local cerebral microcirculation during microsurgical clipping of SAH-related aneurysms. METHODS: The non-invasive laser-Doppler spectrophotometry system “Oxygen-to-See (O2C)” was used in 14 consecutive patients (11 female, 3 male, median age 56.5±9.7 yrs) with aneurysmatic SAH. A subdural probe measured capillary venous oxygenation (SO2), relative hemoglobin content (rHb), blood cell velocity (velo) and blood flow (flow) in 7 mm tissue depth. Data samples were recorded as baseline immediately before intraoperative application of MgSO(4) 10% 50 mg/kg body weight and 10 min thereafter. The continuous MgSO(4) infusion rate depended on blood pressure (mean arterial pressure > 60-65 mmHg) and lasted a maximum of 60 min. RESULTS: MgSO(4) was administered 2.8 (min. 1.6, max. 15.5) hours after onset of symptoms. Median flow increased significantly by 20.8% (5–68%, p = 0.001). Velo increased 4.9% (1–17%), rHb decreased 1.5% (3–34%) and SO2 decreased 9.4% (8–38%) by trend compared to the baseline values. FiO(2) correlated positively with velo (r(s) = 0.712, p = 0.004), whereas arterial HCO(3) correlated negatively with SO2 (r(s) = −0.599, p = 0.024). Of 14 patients, 2 had symptomatic vasospasm. CONCLUSIONS: Our data suggest an increased cerebral blood flow after early intraoperative administration of MgSO(4) in patients with SAH. Using a non-invasive laser-Doppler spectrophotometry system, this technique is feasible for continuous real-time monitoring of cerebral microcirculation. TRIAL REGISTRATION: DRKS (German Clinical Trial Registry), DRKS00013047, retrospectively registered on September 21(st), 2017.