Awake Craniotomy for Excision of Tumor with Speech Mapping using dexmedetomidine

General: Patients may be symptomatic or asymptomatic. Symptoms may be due to location of tumor or due to increased ICP. You should know the location (mainly left-sided), kind (if known) and size of the tumor(s), any preop neurological deficits and symptoms and if the patient is at risk for increased ICP.
Preop: Start an IV on ipsilatral hand to the tumor. Tape IV(s) well. Premedicate with up to 2 mg of midazolam depending on patient’s mental status. None if altered mental status (prevent further increase in ICP).
Monitors: Routine monitors. Arterial (ipsilateral to tumor) and Foley catheters inserted after beginning of sedation. 
Anesthesia: Goals are to have an awake, cooperative patient during speech mapping but comfortably sedated at other times. NEVER have the patient over sedated (respiratory depression/apnea). Patients typically receive 1-2 g of Cefazolin, and 4 mg of decadron before skin incision, and if indicated up to 1 g/kg of mannitol on skin incision (verify all with surgeon). Sedation before mapping is achieved with propofol (up to 100 μg/kg/min) and remifentanil (0.05 μg/kg/min and higher) and communication/rapport (a lot) with the patient. Administer up to 100 μg of fentanyl in divided doses in the beginning. After arrival to operating room, apply monitors, and nasal cannula O2 taped to cheeks. Propofol boluses for foley insertion. Then have patient alert and cooperative for positioning. Propofol boluses again for lidocaine infiltration (by surgeons) for Mayfield pin application. Then adjust propofol/remifentanil infusions for patient comfort. Analgesia will be provided by local anesthesia (by surgeons). Drapes will be positioned so that patient can see a video screen during speech mapping. May need to use the anesthesia machine circuit to blow oxygen/air toward patients face to prevent rebreathing of CO2. Remind the patient of the loud noise before drilling of bone. Once bone flap has been removed, discontinue sedatives so that the patient can hyperventilate when asked, before opening of dura. If the dura is too sensitive, the surgeons can apply lidocaine to the nervous innervation of the dura. No sedatives will be administered during mapping. Have propofol (10 mg/ml) in a 10 ml syringe attached to the IV in case of seizures. If necessary, administer 1 mg/kg propofol for seizure suppression (communicate with surgeon). After mapping, sedation is achieved with dexmedetomidine (up to 1.5 μg/kg/hr) and remifentanil (0.025 μg/kg/min and higher). Use a 0.7 μg/kg dexmedetomidine loading dose over 10 min, and start with a 0.7 μg/kg/hr dexmedetomidine infusion. Sedative effect develops over 15 min. Titrate dexmedetomidine in 0.2 μg/kg/hr increments (0.3 – 1.5 μg/kg/hr range) to keep the patient comfortable, but also arousable. In case of upper airway obstruction, consider using a nasal airway.
Potential complications: Apnea, respiratory depression, high pCO2, agitation, N/V, propofol associated agitation.
Recovery: Discontinue sedative infusions. Use a hemodynamic monitor and supplemental oxygen during patient transport to ICU. Prevent postoperative hypertension to avoid intracranial bleeding (labetalol).