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awake_craniotomy

Awake craniotomy

General information

Usually employed for brain mapping, especially for speech areas. Numerous techniques and protocols have been described. Typically, the patient is temporarily anesthetized with short-acting agents (inhalational and/or injectable). This is supplemented with local anesthesia. The craniotomy is then performed and the patient is allowed to wake up while the brain is exposed to permit neurophysiologic testing during surgery. If (short-acting) paralytics are used, it is critical to reverse these agents 15–30 minutes prior to applying the electrical stimulation and that a train-of-four muscle twitch can be elicited.


An awake craniotomy is a safe neurosurgical procedure that minimizes the risk of brain injury. During the course of this surgery, the patient is asked to perform motor or cognitive tasks, but some patients exhibit severe sleepiness.

For neurosurgery with an awake craniotomy, the critical issue is to set aside enough time to identify eloquent cortices by electrocortical stimulation (ECS). High gamma activity (HGA) ranging between 80 and 120 Hz on electrocorticogram (ECoG) is assumed to reflect localized cortical processing.

In recent years, there have been a number of reports on interventions in conscious patients with other neurosurgical pathologies, which may be regarded as a new emerging tendency in neurosurgery and neuroanesthesiology. Neurosurgery in conscious patients provides a special advantage because it enables highly functional neuromonitoring without use of complex devices 1).

Indications

Awake craniotomy indications.

Cost effectiveness

Retrospective analysis of a cohort of 17 patients with perirolandic gliomas who underwent an AC with DCS were case-control matched with 23 patients with perirolandic gliomas who underwent surgery under GA with neuromonitoring (ie, motor-evoked potentials, somatosensory-evoked potentials, phase reversal). Inpatient costs, quality-adjusted life years (QALY), extent of resection, and neurological outcome were compared between the groups.

Total inpatient expense per patient was ${\$}$ 34 804 in the AC group and ${\$}$ 46 798 in the GA group ( P = .046). QALY score for the AC group was 0.97 and 0.47 for the GA group ( P = .041). The incremental cost per QALY for the AC group was ${\$}$ 82 720 less than the GA group. Postoperative Karnofsky performance status was 91.8 in the AC group and 81.3 in the GA group (P = .047). Length of hospitalization was 4.12 days in the AC group and 7.61 days in the GA group ( P = .049).

The total inpatient costs for awake craniotomies were lower than surgery under GA. This study suggests better cost effectiveness and neurological outcome with awake craniotomies for perirolandic gliomas 2).

Typical sequence for anesthesia

1. in the pre-op holding area, load with Precedex® (dexmedetomidine) 0.5 mcg/kg IV over 20 minutes followed by intra-op infusion at 0.4–1.0 mcg/kg/hr

2. induction of anesthesia utilizes propofol 3 mg/kg IV followed by laryngeal mask airway (LMA) placement

3. skull block: injection of local anesthetic (e.g. 30 ml of 0.5% bupivacaine) to permit the skin incision and also rigid head fixation with pins (as required for image navigation devices, and situations where no head movement can be tolerated during surgery) without pain at the time of the wake-up. Injection at 4 regions on each side

❶ supraorbital & supratrochlear nerves: 2 ml injected 1.5 cm above the supraorbital foramen above the medial third of the orbit. NB: if you are going to use surface matching to register the patient for image guidance (e.g. BrainLab or Stealth), injecting here may deform the skin and affect the registration accuracy. Consider injecting a lower volume of higher concentration agent (e.g. 2% lidocaine)

❷ auriculotemporal nerve: 5 ml injected 1.5 cm anterior to the tragus. ✖ Caution: to avoid anesthetizing the facial nerve, inject just deep to the subcutaneous tissue

❸ postauricular branches of the greater auricular nerve: 2 ml 1.5 cm posterior to the antitragus

❹ greater, lesser & third occipital nerves: inject 5 ml with a 22 gauge spinal needle at the mastoid process and proceed along the nuchal ridge until the midline is reached

4. start inhalational anesthesia with 0.5 MAC desflurane with the patient breathing spontaneously while the scalp incision, craniotomy, and dural opening are performed (the dura is pain sensitive, the brain is not)

5. as the dural opening is begun, the desflurane is turned off and a remifentanil infusion of 0.1–0.2 mcg/kg/min IV is started

6. by the time the dural opening is completed, the desflurane has usually worn off and the LMA can be removed

7. remifentanil is then titrated for pain control

8. neurophysiologic testing can usually be performed at this time

9. the operation may often be carried to completion with the patient awake, although once the intracranial part of the operation is completed, more pain relief may be desired and general anesthesia may be needed for pain control or agitation (LMA may suffice here)

Case series

see Awake surgery case series.

1)
Lubnin AY. [Neurosurgery in conscious patients: forward to the past]. Zh Vopr Neirokhir Im N N Burdenko. 2018;82(1):93-101. doi: 10.17116/neiro201882193-101. Russian. PubMed PMID: 29543221.
2)
Eseonu CI, Rincon-Torroella J, ReFaey K, Quiñones-Hinojosa A. The Cost of Brain Surgery: Awake vs Asleep Craniotomy for Perirolandic Region Tumors. Neurosurgery. 2017 Mar 15. doi: 10.1093/neuros/nyx022. [Epub ahead of print] PubMed PMID: 28327904.
awake_craniotomy.txt · Last modified: 2020/02/20 17:27 by administrador