Anaesthesia with injectable versus gaseous anaesthetic agents for rapid awakening following surgery for brain tumour

Review question: We reviewed and compared evidence on the usefulness of injectable and gaseous techniques for rapid awakening from anaesthesia in people undergoing surgery for brain tumour.

Background: Brain tumour surgery is carried out most often with the patient asleep and with the use of injectable agents or gases. Injectable agents are delivered to the patient through the veins, whereas gases are delivered to the lungs through a tube placed in the windpipe. Advantages of one over the other approach remain questionable. Smooth and quick awakening after surgery is important for these patients so that their mental status may be assessed easily. We aimed to discover whether injectable techniques were better or worse than gaseous techniques.

Study characteristics: The evidence is current to June 2014. We included studies with participants from all age groups except neonates (infants less than 28 days old) who received injectable or gas techniques of anaesthesia during surgery for brain tumour. We reran the searches for all databases in March 2016 and found two studies that are awaiting classification. We will deal with them when we update this review.

Key results: We found 15 eligible studies with 1833 participants. These studies compared one injectable drug (propofol) with two gaseous drugs (sevoflurane and isoflurane). Although isoflurane was associated with slower awakening (about three and a half minutes) compared with propofol, researchers found no important differences between propofol and sevoflurane. In terms of adverse effects, propofol was less likely to cause nausea and vomiting than either gas anaesthetic (about half as likely) but was more likely to be associated with changes in blood pressure. Overall, we found that isoflurane is associated with slower awakening, but we have found no evidence of important differences between sevoflurane and propofol.

Quality of evidence

We found evidence of low quality for our main outcome of quick wakefulness, and the effect of injectable anaesthetic technique in people undergoing brain tumour surgery is uncertain. Further research and well-designed studies are needed.

Authors' conclusions: 

The finding of our review is that the intravenous technique is comparable with the inhalational technique of using sevoflurane to provide early emergence from anaesthesia. Adverse events with both techniques are also comparable. However, we derived evidence of low quality from a limited number of studies. Use of isoflurane delays emergence from anaesthesia. These results should be interpreted with caution. Randomized controlled trials based on uniform and standard methods are needed. Researchers should follow proper methods of randomization and blinding, and trials should be adequately powered.

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Background: 

Brain tumour surgery usually is carried out with the patient under general anaesthesia. Over past years, both intravenous and inhalational anaesthetic agents have been used, but the superiority of one agent over the other is a topic of ongoing debate. Early and rapid emergence from anaesthesia is desirable for most neurosurgical patients. With the availability of newer intravenous and inhalational anaesthetic agents, all of which have inherent advantages and disadvantages, we remain uncertain as to which technique may result in more rapid early recovery from anaesthesia.

Objectives: 

To assess the effects of intravenous versus inhalational techniques for rapid emergence from anaesthesia in patients undergoing brain tumour surgery.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 6) in The Cochrane Library, MEDLINE via Ovid SP (1966 to June 2014) and Embase via Ovid SP (1980 to June 2014). We also searched specific websites, such as www.indmed.nic.in, www.cochrane-sadcct.org and www.Clinicaltrials.gov (October 2014). We reran the searches for all databases in March 2016, and when we update the review, we will deal with the two studies of interest found through this search that are awaiting classification.

Selection criteria: 

We included randomized controlled trials (RCTs) that compared the use of intravenous anaesthetic agents such as propofol and thiopentone with inhalational anaesthetic agents such as isoflurane and sevoflurane for maintenance of general anaesthesia during brain tumour surgery. Primary outcomes were emergence from anaesthesia (assessed by time to follow verbal commands, in minutes) and adverse events during emergence, such as haemodynamic changes, agitation, desaturation, muscle weakness, nausea and vomiting, shivering and pain. Secondary outcomes were time to eye opening, recovery from anaesthesia using the Aldrete or Modified Aldrete score (i.e. time to attain score ≥ 9, in minutes), opioid consumption, brain relaxation (as assessed by the surgeon on a 4- or 5-point scale) and complications of anaesthetic techniques, such as intraoperative haemodynamic instability in terms of hypotension or hypertension (mmHg), increased or decreased heart rate (beats/min) and brain swelling.

Data collection and analysis: 

We used standardized methods in conducting the systematic review, as described by the Cochrane Handbook for Systematic Reviews of Interventions. Two review authors independently extracted details of trial methods and outcome data from reports of all trials considered eligible for inclusion. We performed all analyses on an intention-to-treat basis. We used a fixed-effect model when we found no evidence of significant heterogeneity between studies, and a random-effects model when heterogeneity was likely. For assessments of the overall quality of evidence for each outcome that included pooled data from RCTs only, we downgraded the evidence from 'high quality' by one level for serious (or by two levels for very serious) study limitations (risk of bias), indirectness of evidence, serious inconsistency, imprecision of effect or potential publication bias.

Main results: 

We included 15 RCTs with 1833 participants. We determined that none of the RCTs were of high methodological quality. For our primary outcomes, pooled results from two trials suggest that time to emergence from anaesthesia, that is, time needed to follow verbal commands, was longer with isoflurane than with propofol (mean difference (MD) -3.29 minutes, 95% confidence interval (CI) -5.41 to -1.18, low-quality evidence), and time to emergence from anaesthesia was not different with sevoflurane compared with propofol (MD 0.28 minutes slower with sevoflurane, 95% CI -0.56 to 1.12, four studies, low-quality evidence). Pooled analyses for adverse events suggest lower risk of nausea and vomiting with propofol than with sevoflurane (risk ratio (RR) 0.68, 95% CI 0.51 to 0.91, low-quality evidence) or isoflurane (RR 0.45, 95% CI 0.26 to 0.78) and greater risk of haemodynamic changes with propofol than with sevoflurane (RR 1.85, 95% CI 1.07 to 3.17), but no differences in the risk of shivering or pain. Pooled analyses for brain relaxation suggest lower risk of tense brain with propofol than with isoflurane (RR 0.88, 95% CI 0.67 to 1.17, low-quality evidence), but no difference when propofol is compared with sevoflurane.

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