Volatile isoflurane sedation in cerebrovascular intensive care patients using AnaConDaA®: effects on cerebral oxygenation, circulation, and pressure

The anesthetic-conserving device AnaConDa(A (R)), a miniature vaporizer, allows volatile sedation in the intensive care unit (ICU). We investigated the effects of isoflurane sedation on cerebral and systemic physiology parameters in neuromonitored ICU stroke patients. Included in the study were 19 consecutive ventilated patients with intracerebral hemorrhage (12), subarachnoid hemorrhage (4), and ischemic stroke (3) who were switched from intravenous propofol or midazolam to inhalative isoflurane sedation for an average of 3.5 days. During the sedation transition, the following parameters were assessed: mean arterial pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), middle cerebral artery mean flow velocity (MFV) and cerebral fractional tissue oxygen extraction (FTOE), as well as systemic cardiopulmonary parameters and administered drugs. After the first hour, mean ICP showed an increase of 2.1 mmHg that was not clinically relevant. Likewise, MFV did not change. MAP and CPP, however, decreased by 6.5 and 6.3 mmHg, respectively. FTOE was reduced slightly from 0.24 to 0.21 (p = 0.03). Over an observation period of 12 h, ICP remained stable, while MAP and thus CPP showed distinct decreases (CPP: -10 mmHg at 6 h, p < 0.001; -7.5 mmHg at 12 h, p = 0.005, when compared to preswitch levels) despite a 1.5-fold increase in vasopressor administration. We suggest that that it is possible to reach sufficient sedation levels in cerebrovascular ICU patients by applying volatile isoflurane long-term without a relevant increase in ICP, if baseline ICP values are low or only moderately elevated. However, caution should be exercised in view of isoflurane's decreasing effect on MAP and CPP. Multimodal neuromonitoring is strongly recommended when applying this off-label sedation method.