Hypercapnia to Prevent Secondary Ischemia in SAH

Overview

Delayed cerebral vasospasm and secondary ischemic infarction are feared complications after aneurysmal subarachnoid hemorrhage (aSAH). To date, there is no effective therapy to prevent these ischemic complications. The arterial partial pressure of carbon dioxide (PaCO2) is one of the main determinants of cerebral blood flow (CBF) in healthy subjects. It is yet largely unknown, if and to what extent modulations of PaCO2 can influence CBF in patients after aSAH. The trial is a phase 1 study in which the feasibility of hypercapnia in SAH patients is tested. PaCO2 is gradually raised to 60 mmHg in 10 mechanically ventilated aSAH patients. Cerebral oxygen saturation measured by NIRS and CBF determined by an intracerebral thermodilution probe are the primary end points. If the feasibility is confirmed, this trial will be followed by a phase 2 dose finding study.

The course of aneurysmal subarachnoid hemorrhage (aSAH) is determined by the sequence of several ischemic episodes. Immediately after aSAH, an increase of ICP causes an increase of CBF. It is followed by an acute vasoconstriction over the next hours and days. Typically between day 4 and 10 after aSAH, delayed arterial narrowing and a decrease of CBF occurs in approximately 50 % of aSAH patients and may result in cerebral ischemia and infarction. After the failure of the CONSCIOUS-trial to improve outcome after aSAH, there is no specific treatment in sight to effectively prevent cerebral ischemic events after aSAH. Under physiological conditions, the arterial partial pressure of carbon dioxide (PaCO2) is one of the main determinants of cerebral blood flow (CBF). An elevation of PaCO2 may also be a useful treatment on aSAH patients. This trial is designed as a phase 1 study to test the feasibility of controlled hypercapnia in mechanically ventilated aSAH patients with poor-grade SAH. Monitoring is performed by an external ventricular drainage (ICP), near infrared spectroscopy (tissue oxygenation) and a thermodilution probe (CBF). The latter monitoring tools represent the primary end points of this study. In case of affirmed feasibility, a dose finding study will be launched as a next step.