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Background: Previous animal and clinical studies showed that nitrous oxide may produce long-term analgesia. The aim of this study was to evaluate the effect of nitrous oxide in preventing chronic postsurgical pain. We also explored whether methylenetetrahydrofolate reductase gene polymorphisms (1298A>C, 667C>T) would enhance nitrous oxide analgesia.Methods: We conducted a telephone interview at 12 months after surgery on 2924 (41.1%) patients enrolled in the Evaluation of Nitrous Oxide in the Gas Mixture for Anaesthesia-II trial. Pain at the wound site was recorded using the modified brief pain inventory and the neuropathic pain questionnaire. General health status was measured using the EQ-5D questionnaire. Genotyping was performed in a subset of 674 Asian patients in Hong Kong.Results: At 12 months after surgery, 356 (12.2%) patients reported chronic postsurgical pain at the wound site and 112 (3.8%) patients had severe pain and required regular analgesic interventions. Nitrous oxide did not affect the rate of chronic postsurgical pain (11.8% nitrous oxide group; 12.5% no nitrous oxide group), relative risk (95% confidence intervals): 0.94 (0.75-1.17), P=0.57. However, in a planned subgroup analysis, nitrous oxide reduced the risk of chronic postsurgical pain in Asian patients, relative risk (95% confidence intervals): 0.70 (0.50-0.98), P=0.031. Patients who were homozygous for either gene polymorphism and who received nitrous oxide during surgery were less likely to report chronic postsurgical pain.Conclusions: Nitrous oxide administration had no impact on chronic postsurgical pain, but benefits may still be possible in Asian patients and patients with variants in methylenetetrahydrofolate reductase gene.Clinical Trial Registration: NCT00430989. [ABSTRACT FROM AUTHOR]

There is no high-level evidence supporting an optimal top-up solution to convert labour epidural analgesia to surgical anaesthesia for Caesarean section. The aim of this meta-analysis was to identify the best epidural solutions for emergency Caesarean section anaesthesia, with respect to rapid onset and low supplementation of intraoperative block. Eleven randomized controlled trials, involving 779 parturients, were identified for inclusion after a systematic literature search and risk of bias assessment. ‘Top-up’ boluses were classified into three groups: 0.5% bupivacaine or levobupivacaine (Bup/Levo); lidocaine and epinephrine, with or without fentanyl (LE±F); and 0.75% ropivacaine (Ropi). Pooled analysis using the fixed-effects method was used to calculate the mean difference (MD) for continuous outcomes and risk ratio (RR) for dichotomous outcomes. Lidocaine and epinephrine, with or without fentanyl, resulted in a significantly faster onset of sensory block [MD −4.51 min, 95% confidence interval (CI) −5.89 to −3.13 min, P<0.00001]. Bup/Levo was associated with a significantly increased risk of intraoperative supplementation compared with the other groups (RR 2.03; 95% CI 1.22–3.39; P=0.007), especially compared with Ropi (RR 3.24, 95% CI 1.26–8.33, P=0.01). Adding fentanyl to a local anaesthetic resulted in a significantly faster onset but did not affect the need for intraoperative supplementation. Bupivacaine or levobupivacaine 0.5% was the least effective solution. If the speed of onset is important, then a lidocaine and epinephrine solution, with or without fentanyl, appears optimal. If the quality of epidural block is paramount, then 0.75% ropivacaine is suggested. [ABSTRACT FROM PUBLISHER]

Background: Arousal after total i.v. anaesthesia (TIVA) has been reported to be detectable by monitoring the number of fluctuations per second (NFSC), a parameter of skin conductance (SC). However, compared with monitoring of the bispectral index (BIS), the predictive probability of NFSC was significantly lower. The aim of this study was to determine the value of the two new, not yet published parameters of SC, area under the curve (AUC) methods A and B, for monitoring emergence from TIVA compared with monitoring of NFSC and BIS.Methods: Twenty-five patients undergoing surgery were investigated. NFSC, AUC A, AUC B, BIS, and haemodynamic parameters (mean arterial pressure and heart rate) were recorded simultaneously. The performance of the monitoring devices in distinguishing between the clinical states 'steady-state anaesthesia', 'first clinical reaction', and 'extubation' were compared using the method of prediction probability (Pk) calculation.Results: BIS showed the best performance in distinguishing between 'steady-state anaesthesia' vs 'first reaction' (Pk BIS 0.95; NFSC 0.73; AUC A 0.54; AUC B 0.62) and 'steady-state anaesthesia' vs 'extubation' (Pk BIS 0.99; NFSC 0.73; AUC A 0.71; AUC B 0.67). However, the time from first BIS>60/SC>0 to a first clinical reaction was significantly shorter for BIS (median BIS((R)) 180 s; NFSC 780 s; AUC A 750 s; AUC B 690 s; P < 0.001).Conclusions: AUC A and AUC B did not improve accuracy of SC monitoring in patients waking after TIVA. [ABSTRACT FROM AUTHOR]