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LETTER TO THE EDITOR

Anesthesia for Craniotomy with Intraoperative Awakening: How to Avoid Respiratory Depression and Hypertension?

Department of Anesthesiology, Hospital Geral de Santo António, Porto, Portugal, xlanesth{at}mail.telepac.pt

To the Editor:

We read with interest the article by Keifer et al. (1). However, we have some concerns about their anesthetic technique for craniotomy with intraoperative awakening. The authors managed the airway with a nasal cannula, facemask, or nasal trumpets. Patients breathed spontaneously. They observed respiratory depression in 69 of 96 patients (defined as an episode of apnea lasting at least 30 s) and hypercarbia (Paco₂ >50 mm Hg) in almost one third of the patients. The authors used mannitol and furosemide in all patients and did not report cases of "tight brain."

We believe that a laryngeal mask airway might have offered advantages by providing a more secure airway and allowing controlled ventilation, as described by Sarang and Dinsmore (2). This technique might avoid the ventilatory depression and hypercarbia observed by Keifer et al., as well as the need to administer mannitol and furosemide. Diuretics may cause dehydration, hypotension, and electrolyte disturbance, and routine administration of diuretics might be avoided if CO₂ were not allowed to increase.

The use of laryngeal mask and controlled ventilation would require larger doses of propofol and remifentanil, possibly delaying emergence for brain mapping. The use of target-controlled infusion devices (or pharmacokinetic simulations) has been shown to decrease time for awakening during craniotomies and provide hemodynamic stability (3,4). This technique may be a useful alternative for craniotomies requiring intraoperative awakening.

The authors also reported the occurrence of hypertensive episodes during Mayfield holder placement and suggested the use of short-acting vasodilators to avoid those episodes. Such episodes might be avoided by administering a bolus of remifentanil. Vasodilators may cause cerebral vasodilatation and increase intracranial pressure, whereas remifentanil would have a limited effect on intracranial pressure. Hypertensive episodes related with intraoperative emergence can be avoided by continuing a small-dose infusion of remifentanil and propofol (3,4).

References

1. Keifer JC, Dentchev D, Little K, et al. A retrospective analysis of a remifentanil/propofol general anesthetic for craniotomy before awake functional brain mapping. Anesth Analg 2005;101:502–8.[Abstract/Free Full Text]
2. Sarang A, Dinsmore J. Anaesthesia for awake craniotomy: evolution of a technique that facilitates awake neurological testing. Br J Anaesth 2003;90:161–5.[Abstract/Free Full Text]
3. Hans P, Bonhomme V, Born JD, et al. Target-controlled infusion of propofol and remifentanil combined with bispectral index monitoring for awake craniotomy. Anaesthesia 2000;55:255–9.[Web of Science][Medline]
4. Johnson K, Egan T. Remifentanil and propofol combination for awake craniotomy: case report with pharmacokinetic simulations. J Neurosurg Anesthesiol 1998;10:25–9.[Web of Science][Medline]

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