Summary Concise guidelines are presented that relate abnormalities of coagulation, whether the result of the administration of drugs or that of pathological processes, to the consequent haemorrhagic risks associated with neuraxial and peripheral nerve blocks. The advice presented is based on published guidelines and on the known properties of anticoagulant drugs. Four separate Tables address risks associated with anticoagulant drugs, neuraxial and peripheral nerve blocks, obstetric anaesthesia and special circumstances such as trauma, sepsis and massive transfusion.

SummaryEpidural mixtures containing lidocaine with or without additives are commonly used to convert epidural analgesia in labour to anaesthesia for emergency Caesarean section, but direct comparisons with alternative, single agents in this situation are few. In a prospective double-blinded trial, we compared a freshly prepared lidocaine-bicarbonate-adrenaline mixture (final concentrations 1.8%, 0.76% and 1 : 200,000, respectively) with our standard agent, levobupivacaine 0.5%, for extending epidural blockade for emergency Caesarean section. Using a sequential analysis technique, with data analysed in blocks of 40, women receiving epidural analgesia in labour who required top-up for Caesarean section were randomly assigned to receive 20 ml of epidural solution over 3 min. The first analysis (n = 40) indicated that the study should be stopped, as significant differences were found in our primary outcome data. Median (IQR [range]) times to reach a block to touch to T5 and cold to T4 were, respectively, 7 (6-9 [5-17]) min and 7 (5-8 [4-17]) min for lidocainebicarbonate-adrenaline, and 14 (10 )17 [9-31]) min and 11 (9-14 [6-30]) min for levobupivacaine (p = 0.00004 and 0.001, respectively). Pre-and intra-operative supplementation ⁄ pain, maternal side-effects and neonatal outcomes (excluding five women who underwent instrumental delivery) were similar between the groups. Intra-operative maternal sedation (scored by the mother on a 10-point scale) was greater with lidocaine-bicarbonate-adrenaline (4.5 (3-8 [1-9])) than with levobupivacaine (3 (1-4 [1-7])), but not significantly so (p = 0.07). We conclude that epidural lidocaine-bicarbonate-adrenaline halves the onset time when extending epidural analgesia for Caesarean section although there is a possibility of increased maternal sedation. When extending epidural analgesia in labour for emergency Caesarean section, the most appropriate choice of local anaesthetic for achieving rapid and reliable epidural anaesthesia remains unclear. A recent survey of leading UK obstetric anaesthetists [1] found that 13 combinations of local anaesthetics and adjuncts are used in this situation, with 2% lidocaine (alone or in combination) used by 40% of respondents and 0.5% levobupivacaine or bupivacaine used by 72% of respondents (some respondents using more than one in their practice). In our unit, levobupivacaine is the standard agent used in this situation and was adopted as a result of previous studies that showed no consistent advantage of alternatives [2][3][4], and because of the superior safety profile of levobupivacaine compared with bupivacaine [5,6]. Use of levobupivacaine has recently been recommended as best practice when extending epidural analgesia for emergency Caesarean section [7].We have found that trainees rotating to our unit often report the use of a lidocaine-bicarbonate-adrenaline mixture in other units when a faster onset of block is required, for example when there is fetal compromise.

SummaryWomen in labour receiving epidural analgesia with 15 ml bupivacaine 0.1% and 2 lg.ml )1 fentanyl followed by 10-15-ml top-ups as required, who needed Caesarean section, were randomly allocated to receive 20 ml levobupivacaine 0.5% over 3 min with either 75 lg fentanyl (1.5 ml) or 1.5 ml saline. Further top-ups or inhaled or intravenous supplementation were given for breakthrough pain. Time to onset (loss of cold sensation to T4 and touch sensation to T5 bilaterally), quality of analgesia and side-effects were recorded. The study was stopped after 112 patients had been randomly assigned, due to a unit protocol change, from midwife-administered top-ups to patient-controlled epidural analgesia. Data from 51 patients given fentanyl and 54 given saline were available for analysis. There were no significant differences in onset times or supplementation between the groups, but there was more intra-operative nausea ⁄ vomiting with fentanyl (53%) than with saline (18%; p = 0.004). We found no advantage of adding fentanyl to epidural levobupivacaine when extending epidural analgesia in women already receiving epidural fentanyl during labour and there was an increased incidence of intra-operative nausea and vomiting. Power analysis suggested the same conclusion even had the study proceeded to completion.

It is not clear how converting epidural analgesia for labour to epidural anaesthesia for emergency caesarean section affects either cutaneous vasomotor tone or mean body temperature. We hypothesised that topping up a labour epidural blocks active cutaneous vasodilation (cutaneous heat loss and skin blood flow decrease), and that as a result mean body temperature increases. Twenty women in established labour had body temperature, cutaneous heat loss and skin blood flow recorded before and after epidural top-up for emergency caesarean section. Changes over time were analysed with repeated measures ANOVA. Mean (SD) mean body temperature was 36.8 (0.5)°C at epidural top-up and 36.9 (0.6)°C at delivery. Between epidural top-up and delivery, the mean (SD) rate of increase in mean body temperature was 0.5 (0.5)°C.h À1 . Following epidural topup, chest (p < 0.001) and forearm (p = 0.004) heat loss decreased, but head (p = 0.05), thigh (p = 0.79) and calf (p = 1.00) heat loss did not change. The mean (SD) decrease in heat loss was 15 (19) % (p < 0.001). Neither arm (p = 0.06) nor thigh (p = 0.10) skin blood flow changed following epidural top-up. Despite the lack of change in skin blood flow, the most plausible explanation for the reduction in heat loss and the increase in mean body temperature is blockade of active cutaneous vasodilation. It is possible that a similar mechanism is responsible for the hyperthermia associated with labour epidural analgesia.

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