Abstract: We included 28 RCTs with 4507 randomized participants undergoing different types of surgery (predominantly cardiovascular, laparoscopic, abdominal, orthopaedic and ophthalmic procedures). We found no quasi-randomized trials. Four studies are awaiting classification because we had insufficient information to assess eligibility. All studies compared maintenance with propofol-based TIVA versus inhalational maintenance of anaesthesia. Six studies were multi-arm and included additional TIVA groups, additional inhalational maintenance or both. Inhalational maintenance agents included sevoflurane (19 studies), isoflurane (eight studies), and desflurane (three studies), and was not specified in one study (reported as an abstract). Some studies also reported use of epidural analgesia/anaesthesia, fentanyl and remifentanil. We found insufficient reporting of randomization methods in many studies and all studies were at high risk of performance bias because it was not feasible to blind anaesthetists to study groups. Thirteen studies described blinding of outcome assessors. Three studies had a high of risk of attrition bias, and we noted differences in the use of analgesics between groups in six studies, and differences in baseline characteristics in five studies. Few studies reported clinical trials registration, which prevented assessment of risk of selective reporting bias. We found no evidence of a difference in incidences of postoperative delirium according to type of anaesthetic maintenance agents (odds ratio (OR) 0.59, 95% confidence interval (CI) 0.15 to 2.26; 321 participants; five studies; very low-certainty evidence); we noted during sensitivity analysis that using different time points in one study may influence direction of this result. Thirteen studies (3215 participants) reported POCD, and of these, six studies reported data that could not be pooled; we noted no difference in scores of POCD in four of these and in one study, data were at a time point incomparable to other studies. We excluded one large study from meta-analysis because study investigators had used non-standard anaesthetic management and this study was not methodologically comparable to other studies. We combined data for seven studies and found low-certainty evidence that TIVA may reduce POCD (OR 0.52, 95% CI 0.31 to 0.87; 869 participants). We found no evidence of a difference in mortality at 30 days (OR 1.21, 95% CI 0.33 to 4.45; 271 participants; three studies; very low-certainty evidence). Twelve studies reported intraoperative hypotension. We did not perform meta-analysis for 11 studies for this outcome. We noted visual inconsistencies in these data, which may be explained by possible variation in clinical management and medication used to manage hypotension in each study (downgraded to low-certainty evidence); one study reported data in a format that could not be combined and we noted little or no difference between groups in intraoperative hypotension for this study. Eight studies reported length of stay in the PACU, and we did not perform meta-analysis for seven studies. We noted visual inconsistencies in these data, which may be explained by possible differences in definition of time points for this outcome (downgraded to very low-certainty evidence); data were unclearly reported in one study. We found no evidence of a difference in length of hospital stay according to type of anaesthetic maintenance agent (mean difference (MD) 0 days, 95% CI -1.32 to 1.32; 175 participants; four studies; very low-certainty evidence). We used the GRADE approach to downgrade the certainty of the evidence for each outcome. Reasons for downgrading included: study limitations, because some included studies insufficiently reported randomization methods, had high attrition bias, or high risk of selective reporting bias; imprecision, because we found few studies; inconsistency, because we noted heterogeneity across studies. We are uncertain whether maintenance with propofol-based TIVA or with inhalational agents affect incidences of postoperative delirium, mortality, or length of hospital stay because certainty of the evidence was very low. We found low-certainty evidence that maintenance with propofol-based TIVA may reduce POCD. We were unable to perform meta-analysis for intraoperative hypotension or length of stay in the PACU because of heterogeneity between studies. We identified 11 ongoing studies from clinical trials register searches; inclusion of these studies in future review updates may provide more certainty for the review outcomes.

Plain-language summary: The evidence is current to November 2017. We included 28 randomized studies with 4507 participants in the review. We are awaiting sufficient information for the classification of four studies. All studies included elderly people undergoing non-cardiac surgery and compared use of propofol-based TIVA versus inhalational agents during maintenance of general anaesthesia. We found little or no difference in postoperative delirium according to the type of anaesthetic maintenance agents from five studies (321 participants). We found that fewer people experienced postoperative cognitive dysfunction when TIVA with propofol was used in seven studies (869 participants). We excluded one study from analysis of this outcome because study authors had used methods to anaesthetize people which were not standard. We found little or no difference in the number of deaths from three studies (271 participants). We did not combine data for low blood pressure during the operation or length of stay in the PACU because we noted differences in studies, which may be explained by differences in patient management (for low blood pressure), and differences in how length of stay in the PACU is defined in each study . We found little or no difference in length of hospital stay from four studies (175 participants). Many studies did not report randomization methods adequately and all studies were at high risk of bias from anaesthetists, who needed to be aware of which anaesthetic agent they used. Outcome assessors in some studies were aware of which study group participants were in. We noted a large loss of participants in three studies, and some studies had differences between groups in the types of drugs used for pain, the types of monitors used to assess how deeply-unconscious the patients were, and participant characteristics at the start of the studies; these factors may have influenced the results. Few studies had reported clinical trials registration. We found few studies for two outcomes (mortality and length of hospital stay), which made the results less precise. We judged evidence for postoperative delirium, number of deaths, length of stay in the PACU, and length of hospital stay to be very low certainty, and evidence for postoperative cognitive dysfunction, and low blood pressure during the operation to be low certainty. TIVA with propofol may reduce postoperative cognitive dysfunction. We are uncertain whether the choice of anaesthetic agents (TIVA with propofol, or inhalational agents) affects postoperative delirium, mortality and length of hospital stay. We found 11 ongoing studies in database and clinical trials register searches. Inclusion of these studies in future review updates will provide more certainty for the review outcomes.