Awake craniotomy with intraoperative MRI: Description of a sedation technique using remifentanil and dexmedetomidine

Abstract

We describe the anaesthetic management of a patient requiring intra-operative MRI and awake neurological testing during neurosurgical resection of a frontal tumour. This tumour involved her motor and speech areas. The anaesthetic drugs administered during awake craniotomy should be safe and allow appropriate changes in the level of sedation, so that the patient is adequately sedated during periods of intense surgical stimulus, yet awake, comfortable and cooperative during functional testing and tumour resection. We report the novel and successful use of a sedative - dexmedetomidine in combination with a narcotic, remifentanil. There has not been much experience with this combination locally. Dexmedetomidine, a selective alpha-2 agonist with sedative, analgesic and anaesthetic-sparing effect does not suppress ventilation. Patients are sedated, but can be easily roused verbally. Remifentanil is a useful choice in this surgery as it can be rapidly titrated according to level of surgical intensity and has a reliable context sensitive half life. Potential problems associated with awake craniotomy such as impaired ventilation during sedation, nausea, vomiting and seizures are discussed. These anaesthetic challenges are compounded by the challenges posed by the iMRI environment. Emphasis is placed on patient selection and preparation peri-operatively. This is crucial to the success of the operation.