Continuous epidural infusion of 0.075% bupivacaine for pain relief in labour

Seventy-three women who requested epidural analgesia during labour were randomly allocated in a prospective study to receive either a continuous epidural infusion of 0.075% bupivacaine at a rate of 12-18 ml/hour (38 mothers) or intermittent top-ups of 0.5% bupivacaine (35 mothers). Both groups received an initial dose of 6-8 ml bupivacaine 0.5%. Patients were asked to score their pain using a 10-cm linear scale prior to insertion of the epidural, 30 minutes after its insertion and hourly thereafter. The quality of analgesia in the continuous infusion group was significantly better than in the intermittent top-up group (p less than 0.025). There was no significant difference in the total dose of bupivacaine given to the two groups.     

Effect of intravenous cimetidine on lignocaine disposition during extradural Caesarean section

We studied whether an intravenous bolus of cimetidine altered the disposition of extradurally administered lignocaine in the parturient. Mothers who requested extradural analgesia for elective Caesarean section were randomly pretreated with either cimetidine 200 mg intravenously (n = 5) or no H2-receptor antagonist (n = 5). No difference was found between peak plasma lignocaine levels or area under the plasma concentration/time curve between the two groups after administration of 6 mg/kg lignocaine 2% with adrenaline 1:200,000. There was no evidence for an effect of a single intravenous dose of cimetidine on lignocaine disposition in the obstetric patient. In addition, the extradural administration of 6 mg/kg lignocaine produces plasma levels well below toxic levels.     

Parturient-controlled epidural analgesia during labour: bupivacaine vs. ropivacaine

In this randomised, controlled study, we compared the hourly dose requirement of ropivacaine 0.125% (group R, n = 16) with bupivacaine 0.125% (group B, n = 16) provided by demand-only (bolus 5 ml, lockout 10 min) parturient-controlled epidural analgesia during labour. The hourly dose requirement was comparable although group R had a lower successful to total demands ratio (p < 0.05). We also found that both groups were clinically indistinguishable in terms of pain relief and side-effects. No difference in maternal or fetal outcome was detected. We conclude that, at a concentration of 0.125%, ropivacaine and bupivacaine were equally effective when self-administered using this patient-controlled regimen.     

Plasma concentrations of bupivacaine during extradural anaesthesia for Caesarean section

The clinical effects and plasma levels associated with the use of 0.5% bupivacaine with and without the addition of 1:200,000 adrenaline (5 micrograms/ml) were studied in 30 patients who underwent extradural anaesthesia for elective Caesarean section. The addition of adrenaline to bupivacaine prolongs analgesia, reduces the degree of hypotension and delays its onset. Plasma bupivacaine levels were consistently lower when adrenaline was added, but this difference was significant only at 10 minutes after the initial dose. Prolonging the interval between increments seems to be a more reliable way to reduce plasma concentration than the addition of the catecholamine.     

A rare complication of extradural analgesia

A case is reported of probable subdural injection of bupivacaine during attempted extradural analgesia for an operative obstetric procedure.     

Continuous infusion epidural analgesia in obstetrics

The effects of 0.08% (Group A) and 0.25% (Group B) solutions of bupivacaine were compared in a random manner, to assess continuous pump infusion epidural analgesia in labour. Both solutions were infused at a dose rate of 20 mg bupivacaine/hour. The results in all the mothers who had received infusions lasting more than 4 hours were studied. There were 25 in Group A and 28 in Group B. Any treatment during the infusion epidural for inadequate analgesia, hypotension, etc., was recorded as an intervention. The mean of the intervention-free intervals was significantly greater in Group A than in Group B, and significantly fewer top-up injections were required in Group A. The results show that the administration of a 0.08% solution of bupivacaine into the epidural space by continuous pump infusion is more labour saving than the infusion of a 0.25% solution. The concept that a greater volume infusion rate maintains a more extended liquid sleeve of local anaesthetic in the epidural space is supported.     

Venous levels of lignocaine and bupivacaine after peribulbar block

Twenty-five patients undergoing elective cataract day surgery were studied after receiving a dual-injection peribulbar block with a mixture consisting of equal volumes of 2% lignocaine and 0.75% bupivacaine with hyaluronidase. A maximum of 10ml of solution was used for the initial block; supplementary injections of up to 10 ml were given to five patients. Venous blood was taken prior to the block and then 1, 10, 20, 30, 60 and 90 min after the block. The peak mean concentrations of lignocaine (0.722 μg. ml⁻¹) and bupivacaine (0.353 μg. ml⁻¹)were found at 10–20 min after injection when no top-up was given and at 10 min after the top-up injection when required. All measured serum concentrations of lignocaine and bupivacaine were below the accepted toxic levels of the two drugs. However, the highest individual toxicity score after a top-up was 0.915 which was very close to the toxicity threshold (= 1) when a scoring system was used to assess the combined levels.     

Comparison of 0.75% levobupivacaine with 0.75% racemic bupivacaine for peribulbar anaesthesia

In a single centre, randomised, double-blind study 50 patients scheduled for intra-ocular surgery received 0.75% levobupivacaine or 0.75% racemic bupivacaine for peribulbar anaesthesia. There were no significant differences in the mean (SD) volume of levobupivacaine (11 (2.7) ml) or racemic bupivacaine (10 (2.6) ml) required, time to satisfactory block (levobupivacaine-13 (5.6) min; racemic bupivacaine-11 (4.4) min), peri-operative pain scores or frequency of adverse events between levobupivacaine and racemic bupivacaine. The safer side-effect profile of levobupivacaine may offer significant advantages in the elderly population undergoing cataract extraction in whom intercurrent disease is common.     

Comparison of extradural and intravenous diamorphine as a supplement to extradural bupivacaine

The influence of route of administration (extradural as compared with intravenous) of diamorphine 0.5 mg/hour as a supplement to extradural bupivacaine (0.125% at 15 ml/hour) was investigated in two groups of 20 patients who underwent major abdominal gynaecological surgery. Significantly more patients in the intravenous group withdrew because of inadequate analgesia (p less than 0.05). Those in the extradural group were significantly more drowsy throughout the study (p less than 0.01), but no major side effects were encountered.     

Plasma bupivacaine levels associated with extradural anaesthesia for Caesarean section

Plasma bupivacaine levels were measured in 47 women undergoing extradural Caesarean delivery. They were divided into four groups according to the following dose regimens using 0.5% bupivacaine. Group A were given a bolus of 20 ml with increment after 20 minutes. Groups B and C were given 10 ml initially with further increments if required at 10 minutes (group B) and 20 minutes (group C); Group D consisted of patients who had an extradural block extended for emergency Caesarean delivery. In the elective groups the highest and most rapidly achieved values were associated with group A and the lowest levels found in group C. The highest levels of all were found in the emergency group. The investigation indicates that slow controlled induction of extradural anaesthesia for Caesarean section greatly reduces the risk of local anaesthetic toxicity.     

Subarachnoid block with hyperbaric lignocaine

A double-blind study was carried out in 20 patients to compare 5% hyperbaric lignocaine and 0.5% hyperbaric bupivacaine for subarachnoid block. The injections were made in the lateral position and the patients turned supine immediately. The onset, extent and duration of sensory and motor blockade, the quality of anaesthesia, cardiovascular effects and the frequency of side effects were studied. Cephalad spread of analgesia was high (T4-5) with both solutions. Bupivacaine produced a longer duration of action in the lumbar and sacral segments but the duration in the thoracic segments was similar. There was a considerable degree of hypotension in both groups but this responded readily to ephedrine. Hyperbaric lignocaine is an alternative to hyperbaric bupivacaine and its shorter duration of action in the lumbar and sacral segments is advantageous when a fast recovery is desirable.     

Continuous blockade of the lumbar plexus after knee surgery—postoperative analgesia and bupivacaine plasma concentrations

In a double blind, randomised, controlled investigation the analgesic effect of a continuous block of the lumbar plexus with bupivacaine compared with sodium chloride was examined in 20 patients with postoperative pain after knee-joint surgery. The infusion was given through a catheter inserted in the neurovascular fascial sheath of the femoral nerve, according to the three-in-one block technique. The patients treated with bupivacaine had significantly lower pain scores and a significantly lower demand for morphine. Side effects related to the catheters or the infusions of bupivacaine were not observed.     

Home-readiness after spinal anaesthesia with small doses of hyperbaric 0.5% bupivacaine

Fifty-four patients were studied prospectively to evaluate home-readiness after a small dose (1 or 2 ml) of subarachnoid hyperbaric 0.5% bupivacaine. The block regressed significantly earlier in the 1 ml group than in the 2 ml group (p < 0.05). The patients were also able to walk significantly earlier in the 1 ml group (median 161 min and 231 min in the 1 ml and 2 ml groups, respectively) (p < 0.05). However, there were no significant differences between the groups in time of ability to void. We conclude that adequate surgical anaesthesia can be achieved with small doses of hyperbaric bupivacaine used for spinal anaesthesia. Although the sensory and motor block after 1 or 2 ml hyperbaric bupivacaine recovered within a reasonable time for day-case surgery, in some patients recovery of the ability to void was delayed to an undesirable extent.