Anaesthesia Management for Awake Craniotomy: Systematic Review and Meta-Analysis

Background Awake craniotomy (AC) renders an expanded role in functional neurosurgery. Yet, evidence for optimal anaesthesia management remains limited. We aimed to summarise the latest clinical evidence of AC anaesthesia management and explore the relationship of AC failures on the used anaesthesia techniques. Methods Two authors performed independently a systematic search of English articles in PubMed and EMBASE database 1/2007-12/2015. Search included randomised controlled trials (RCTs), observational trials, and case reports (n>4 cases), which reported anaesthetic approach for AC and at least one of our pre-specified outcomes: intraoperative seizures, hypoxia, arterial hypertension, nausea and vomiting, neurological dysfunction, conversion into general anaesthesia and failure of AC. Random effects meta-analysis was used to estimate event rates for four outcomes. Relationship with anaesthesia technique was explored using logistic meta-regression, calculating the odds ratios (OR) and 95% confidence intervals [95%CI]. Results We have included forty-seven studies. Eighteen reported asleep-awake-asleep technique (SAS), twenty-seven monitored anaesthesia care (MAC), one reported both and one used the awake-awake-awake technique (AAA). Proportions of AC failures, intraoperative seizures, new neurological dysfunction and conversion into general anaesthesia (GA) were 2% [95%CI:1–3], 8% [95%CI:6–11], 17% [95%CI:12–23] and 2% [95%CI:2–3], respectively. Meta-regression of SAS and MAC technique did not reveal any relevant differences between outcomes explained by the technique, except for conversion into GA. Estimated OR comparing SAS to MAC for AC failures was 0.98 [95%CI:0.36–2.69], 1.01 [95%CI:0.52–1.88] for seizures, 1.66 [95%CI:1.35–3.70] for new neurological dysfunction and 2.17 [95%CI:1.22–3.85] for conversion into GA. The latter result has to be interpreted cautiously. It is based on one retrospective high-risk of bias study and significance was abolished in a sensitivity analysis of only prospectively conducted studies. Conclusion SAS and MAC techniques were feasible and safe, whereas data for AAA technique are limited. Large RCTs are required to prove superiority of one anaesthetic regime for AC.

X Clinical detection of postoperative facial nerve palsy was predefined, and has to be seen as a valid measure.
Nossek 2013 [42] X Recruiting was subjective, but comparison groups were retrospectively built, therefore the risk for selection bias for the comparison groups can be seen negligibly. Valid and reliable: pre-and postoperative MRI scans. Clinical identification of intraoperative seizures can be assumed to be a valid measurement as it is a common procedure. The assessment of patient outcomes after surgery is not described in detail, but neurological testing and assessment of postoperative complications in the clinical postoperative routine should be seen as valid and reliable measurements.
Nossek 2013 [43] X Recruiting was subjective, but comparison groups were retrospectively built, therefore the risk for selection bias for the comparison groups can be seen negligibly. Clinical identification of intraoperative seizures and postoperative neurological outcomes can be assumed to be valid measurements as they are common procedures.

Sanus 2015
[53] X Valid and reliable: preoperative and postoperative imaging to localise the brain tumours/ resection rate. Intraoperative measurement of haemodynamic and respiratory data.

Clinical identification of intraoperative seizures and postoperative neurological outcomes
can be assumed to be valid measurements as they are common procedures. Nossek 2013 [42] X All reported.
Ouyang 2013 [45] X It would have been favourable that the study had reported some neurological outcomes.
But the aim of this study was solely to answer the question for PONV and postoperative pain after AC in specific patients.
Ouyang 2013 [46] X It would have been favourable that the study had reported some neurological outcomes.
But the aim of this study was solely to answer the question for PONV and postoperative pain after AC in specific patients.

X
It is mentioned that their results are restricted to the Chinese population.

X
The general limitation of a retrospective study is mentioned. The learning curve effect of all involved persons during the study period (including recruitment decisions, anaesthesia procedure and surgery) id mentioned.

X
The general limitation of a retrospective study and the experience gained over the years are mentioned. X They discuss the generalisability of the used questionnaires to all neurosurgical patients, as they could not be validated in this study. Furthermore, it was a German questionnaire. The study group was heterogeneous and small. The assignment of the patients to the AC or GA technique was probably biased, but objectiveness was achieved by a interdisciplinary decision board.
Zhang 2008 [62] X Study limitations are not mentioned.
Confounding Q12: Any attempt to balance the allocation between the groups or match groups (e.g., through stratification, matching, propensity scores). Nossek 2013

X (No)
The sizes of the study groups differed. No attempt was made to match the groups.

X (No)
The sizes of the study groups differed. No attempt was made to match the groups.

X (No)
The sizes of the study groups differed. No attempt was made to match the groups.

X (No)
The sizes of the study groups differed. No attempt was made to match the groups.

X (No)
No attempt was made to match the groups.