Anaesthesiological strategies in elective craniotomy: randomized, equivalence, open trial--the NeuroMorfeo trial

Intravenous versus inhalational techniques for rapid emergence from anaesthesia in patients undergoing brain tumour surgery

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 METHODS

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.

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.

The inflammatory response of two different kinds of anesthetics on vascular cognitive impairment rats and the effect on long term cognitive function

Vascular cognitive impairment, caused by vascular injury and inflammation, affects brain function. Present treatment for vascular injury primarily relies on combination therapy of surgery with anesthesia. In this study, we sought to determine the effects of anesthetics, sevoflurane and fentanyl, on long-term cognitive function in brain tissue of rats, and potential correlations with inflammatory factors such as VEGF, IL-1β, TNF-α. We used shuttle box and water maze tests to study the cognitive function of Wistar rats. The results demonstrated that rats treated with sevoflurane or fentanyl performed less shock times and more active escape times compared with rats model undergoing vascular cognitive impairment. Treatment of anesthetics also shortened the periods of learning and memory incubation, suggesting a protective role in cognitive function. In addition, our results unraveled a reducing expression of TNF-α and IL-1β but an increasing level of VEGF in head tissues of rats implemented with anesthetics. These findings underscore the improving role of sevoflurane and fentanyl in the recovery of vascular cognitive impairment rats as well as the cognitive function in rats, by regulating the expression of inflammatory factors.

Effects of Anesthetic Management on Early Postoperative Recovery, Hemodynamics and Pain After Supratentorial Craniotomy

Various clinical trials have assessed how intraoperative anesthetics can affect early recovery, hemodynamics and nociception after supratentorial craniotomy. Whether or not the difference in recovery pattern differs in a meaningful way with anesthetic choice is controversial. This review examines and compares different anesthetics with respect to wake-up time, hemodynamics, respiration, cognitive recovery, pain, nausea and vomiting, and shivering. When comparing inhalational anesthetics to intravenous anesthetics, either regimen produces similar recovery results. Newer shorter acting agents accelerate the process of emergence and extubation. A balanced inhalational/intravenous anesthetic could be desirable for patients with normal intracranial pressure, while total intravenous anesthesia could be beneficial for patients with elevated intracranial pressure. Comparison of inhalational anesthetics shows all appropriate for rapid emergence, decreasing time to extubation, and cognitive recovery. Comparison of opioids demonstrates similar awakening and extubation time if the infusion of longer acting opioids was ended at the appropriate time. Administration of local anesthetics into the skin, and addition of corticosteroids, NSAIDs, COX-2 inhibitors, and PCA therapy postoperatively provided superior analgesia. It is also important to emphasize the possibility of long-term effects of anesthetics on cognitive function. More research is warranted to develop best practices strategies for the future that are evidence-based.

Univariate and bivariate symbolic analyses of cardiovascular variability differentiate general anesthesia procedures

General anesthesia attenuates autonomic function and baroreflex control. This side effect should be prevented as much as possible because it limits the subject's ability in responding to physiological challenges during surgery (e.g. arterial pressure and ventricular contractility drops). This study is designed to rank two of the most commonly exploited general anesthesia treatments, i.e. intravenous anesthesia (IA) based on a propofol-opioid combination and volatile anesthesia (VA) based on a sevoflurane-opioid combination, according to their ability to maintain autonomic nervous system activity and baroreflex control. Univariate and bivariate symbolic techniques were applied to spontaneous heart period (HP) and systolic arterial pressure (SAP) variability series recorded during IA and VA procedures in 19 and 18 patients undergoing elective intracranial neurosurgery. Traditional linear univariate and bivariate frequency domain markers of the autonomic nervous system state and baroreflex control were evaluated as well. We found that: (i) univariate symbolic analysis of HP series suggests a better preservation of vagal modulation in VA than in IA; (ii) bivariate symbolic markers assessing the degree of HP-SAP association differentiate IA from VA, while baroreflex sensitivity and squared coherence function cannot; (iii) bivariate symbolic analysis indicates a better preservation of the HP-SAP association at slow frequencies in IA than in VA, thus suggesting a more active baroreflex control in IA. We conclude that symbolic indexes can be fruitfully exploited to rank general anesthesia treatments, and their performance appears to be superior to that of more traditional linear markers.

Model-based causal closed-loop approach to the estimate of baroreflex sensitivity during propofol anesthesia in patients undergoing coronary artery bypass graft

Cardiac baroreflex is a fundamental component of the cardiovascular control. The continuous assessment of baroreflex sensitivity (BRS) from spontaneous heart period (HP) and systolic arterial pressure (SAP) variations during general anesthesia provides relevant information about cardiovascular regulation in physiological conditions. Unfortunately, several difficulties including unknown HP-SAP causal relations, negligible SAP changes, small BRS values, and confounding influences due to mechanical ventilation prevent BRS monitoring from HP and SAP variabilities during general anesthesia. We applied a model-based causal closed-loop approach aiming at BRS assessment during propofol anesthesia in 34 patients undergoing coronary artery bypass graft (CABG) surgery. We found the following: 1) traditional time and frequency domain approaches (i.e., baroreflex sequence, cross-correlation, spectral, and transfer function techniques) exhibited irremediable methodological limitations preventing the assessment of the BRS decrease during propofol anesthesia; 2) Granger causality approach proved that the methodological caveats were linked to the decreased presence of bidirectional closed-loop HP-SAP interactions and to the increased incidence of the HP-SAP uncoupling; 3) our model-based closed-loop approach detected the significant BRS decrease during propofol anesthesia as a likely result of accounting for the influences of mechanical ventilation and causal HP-SAP interactions; and 4) the model-based closed-loop approach found also a diminished gain of the relation from HP to SAP linked to vasodilatation and reduced ventricular contractility during propofol anesthesia. The proposed model-based causal closed-loop approach is more effective than traditional approaches in monitoring cardiovascular control during propofol anesthesia and indicates an overall depression of the HP-SAP closed-loop regulation.

Coherence analysis overestimates the role of baroreflex in governing the interactions between heart period and systolic arterial pressure variabilities during general anesthesia

During general anesthesia positive pressure mechanical ventilation (MV) profoundly affects intrathoracic pressure and venous return, thus soliciting cardiopulmonary reflexes and modifying stroke volume. As a consequence heart period, approximated as the temporal distance between two consecutive R peaks on the ECG (RR), and systolic arterial pressure (SAP) variability series are usually highly correlated at the MV frequency (MVF) and this significant correlation is commonly taken as an indication of an active baroreflex. In this study the involvement of baroreflex was tested according to a time-domain linear Granger causality approach accounting explicitly for MV in two experimental protocols. In the first protocol volatile (VA) or intravenous (IA) anesthetic was administered in humans during pressure controlled MV (PCMV). In the second protocol IA was administered in pigs during PCMV or pressure support MV (PSMV). Causality analysis was contrasted with RR-SAP squared coherence. Significant coherence values at MVF were always found in both protocols. On the contrary, a significant causal link from SAP to RR was less frequently found in humans independently of the anesthesiological strategy and in animals during PCMV. PSMV was superior to PCMV in animals because it was able to better preserve a link from SAP to RR. During general anesthesia the involvement of baroreflex in governing RR-SAP variability interactions is largely overestimated by RR-SAP squared coherence and causality analysis can be exploited to rank anesthesiological strategies and MV modes according to the ability of preserving a working baroreflex.

A multicentre, randomised, open-label, controlled trial evaluating equivalence of inhalational and intravenous anaesthesia during elective craniotomy

CONTEXT

A clear preference for intravenous or inhalational anaesthesia has not been established for craniotomy in patients without signs of cerebral hypertension.

OBJECTIVES

The NeuroMorfeo trial was designed to test equivalence of inhalational and intravenous anaesthesia maintenance techniques in the postoperative recovery of patients undergoing elective supratentorial surgery.

DESIGN

This trial is a multicentre, randomised, open-label, equivalence design. A balanced stratified randomisation scheme was maintained using a centralised randomisation service. Equivalence was tested using the two one-sided tests procedure.

SETTING

Fourteen Italian neuroanaesthesia centres participated in the study from December 2007 to March 2009.

PATIENTS

Adults, 18 to 75 years old, scheduled for elective supratentorial intracranial surgery under general anaesthesia were eligible for enrolment if they had a normal preoperative level of consciousness and no clinical signs of intracranial hypertension.

INTERVENTIONS

Patients were randomised to one of three anaesthesia maintenance protocols to determine if sevoflurane-remifentanil or sevoflurane-fentanyl were equivalent to propofol-remifentanil.

MAIN OUTCOME MEASURES

The primary outcome was the time to achieve an Aldrete postanaesthesia score of at least 9 after tracheal extubation. Secondary endpoints included haemodynamic parameters, quality of the surgical field, perioperative neuroendocrine stress responses and routine postoperative assessments.

RESULTS

Four hundred and eleven patients [51% men, mean age 54.8 (SD 13.3) years] were enrolled. Primary outcome data were available for 380. Median (interquartiles) times to reach an Aldrete score of at least 9 were 3.48 (2.02 to 7.56), 3.25 (1.21 to 6.45) and 3.32  min (1.40 to 8.33) for sevoflurane-fentanyl, sevoflurane-remifentanil and propofol-remifentanil anaesthesia respectively, which confirmed equivalence using the two one-sided tests approach. Between-treatment differences in haemodynamic variables were small and not clinically relevant. Urinary catecholamine and cortisol responses had significantly lower activation with propofol-remifentanil. Postoperative pain and analgesic requirements were significantly higher in the remifentanil groups.

CONCLUSION

Equivalence was shown for inhalational and intravenous maintenance anaesthesia in times to reach an Aldrete score of at least 9 after tracheal extubation. Haemodynamic variables, the quality of surgical field and postoperative assessments were also similar. Perioperative endocrine stress responses were significantly blunted with propofol-remifentanil and higher analgesic requirements were recorded in the remifentanil groups.

TRIAL REGISTRATION

Eudract 2007-005279-32.

Testing the involvement of baroreflex during general anesthesia through Granger causality approach

Baroreflex sensitivity (BRS) is commonly assessed from spontaneous fluctuations of heart period (HP) and systolic arterial pressure (SAP) during general anesthesia. Unfortunately, general anesthesia depresses autonomic function and, consequently, spontaneous SAP variations could not be capable to drive HP changes, thus preventing the use of spontaneous variability to infer BRS. We applied two Granger causality approaches (F-test and Wald test) during two anesthesiological strategies (i.e. sevoflurane plus remifentanil or propofol plus remifentanil). We found a significant Granger-causality from SAP to HP independently of the anesthesiological strategy; thus suggesting that techniques estimating BRS from spontaneous variability can be utilized during general anesthesia.