Simultaneous bedside assessment of global cerebral blood flow and effective cerebral perfusion pressure in patients with intracranial hypertension.

BACKGROUND: We examined a bedside technique transcerebral double-indicator dilution (TCID) for global cerebral blood flow (CBF) as well as the concept of effective cerebral perfusion pressure (CPP(eff)) during different treatment options for intracranial hypertension, and compared global CBF and CPP(eff) with simultaneously obtained conventional parameters. METHODS: Twenty-six patients developing intracranial hypertension in the course of traumatic brain injury or subarachnoid hemorrhage were prospectively analyzed using a combined assessment during elevated ventilation (n = 15) or osmotherapy (hypertonic saline or mannitol). For calculation of global CBF, injections of ice-cold indocyanine green boluses were performed and temperature and dye concentration changes were monitored in the thoracic aorta and the jugular bulb. CBF was then calculated according to the mean transit time principle. Estimation of CCP, the arterial pressure at which cerebral blood flow becomes zero, was performed by synchronized registration of corresponding values of blood flow velocity in the middle cerebral artery and arterial pressure and extrapolation to zero-flow velocity. CPP(eff) was calculated as mean arterial pressure minus critical closing pressure (CPP(eff) = MAP(c) - CCP). RESULTS: Elevated ventilation causes a decrease in both ICP (P < 0.001) and CBF (P < 0.001). While CPP(conv) increased (P < 0.001), CPP(eff) decreased during this observation (P = 0.002). Administration of osmotherapeutic agents resulted in a decrease of ICP (P < 0.001) and a temporary increase of CBF (P = 0.052). CPP(conv) and CPP(eff) showed no striking difference under osmotherapy. CONCLUSION: TCID allows repeated measurements of global CBF at the bedside. Elevated ventilation lowered and osmotherapy temporarily raised global CBF. In situations of increased vasotonus, CPP(eff) is a better indicator of blood flow changes than conventional CPP.

Arterial spin labeling shows cortical collateral flow in the endovascular treatment of vasospasm after post-traumatic subarachnoid hemorrhage.

We report here on the case of a patient who, 10 days prior to his admission to hospital, had suffered a bicycle accident. He presented with signs of minor dysphasia. A brain CT-scan revealed slight subarachnoid hemorrhage (SAH) in the left sylvian fissure as well as narrowing of the distal M1 segment of the left middle cerebral artery (MCA) on CT-angiography. MRI showed diffusion abnormalities and hypoperfusion in the left MCA territory with cortical hyperperfusion on arterial spin labeling (ASL). Arteriography confirmed the vasospasm, but showed no sign of aneurysm. Angioplasty of the narrowed MCA was successful, and follow-up MRI showed reperfusion of the MCA territory.