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.     

The loading dose for continuous infusion epidural analgesia

The effects of 0.08% and 0.5% bupivacaine, given in equal volumes as the loading dose prior to continuous infusion epidural analgesia, were compared. The incidence of hypotension, as well as the height of sensory blockade, was markedly lowered by reducing the loading dose of bupivacaine. However, the efficacy of the epidural analgesia was maintained by using the same volume for the loading dose. The mean onset of analgesia was delayed from 9.1 to 13.6 minutes. There were fewer calls for intervention consequent upon the reduction in adverse effects. The use of 8 ml 0.08% bupivacaine for the loading dose or for subsequent top-ups is recommended. The concept of a liquid sleeve of local anaesthetic in the epidural space is further supported.     

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.     

Alkalinisation of bupivacaine for sciatic nerve blockade

This double-blind study investigates the effect of pH adjustment of bupivacaine 0.5% with adrenaline 1:200,000 on block latency, duration of analgesia and systemic absorption of local anaesthetic after sciatic nerve blockade. Twenty-four adult patients were randomly allocated into one of two groups: Group A (n = 12) received bupivacaine with adrenaline 1:200,000 (pH 3.9) 2 mg/kg, while Group B (n = 12) received alkalinised bupivacaine with adrenaline 1:200,000 (pH 6.4) 2 mg/kg. Increasing the pH of the local anaesthetic solution significantly reduced block latency from 25 minutes in Group A to 12.5 minutes in Group B (p less than 0.001) and prolonged the duration of useful analgesia from 14.1 hours to 18.3 hours (p less than 0.001). There was no significant difference in plasma bupivacaine levels between the two groups. The results indicate that alkalinisation of bupivacaine reduces time to onset and prolongs the duration of useful analgesia when used for sciatic nerve blockade, without significantly increasing systemic absorption.     

A single dose epidural technique for Caesarean section

An epidural technique based on a fractionated injection through a Tuohy needle of 20 ml over 10 minutes, was investigated in 40 mothers who underwent elective caesarean section. Mothers were randomized to receive either 0.5% bupivacaine plain or 0.5% bupivacaine with adrenaline 1:200,000. After a 2-ml test dose, the remaining 18 ml was injected over 5 minutes. The use of adrenaline did not significantly alter the onset or duration, but improved the efficacy of the epidural block. Mean time to onset of adequate surgical anaesthesia was 20 minutes. Only 10 patients required more than the initial 100 mg of bupivacaine. Epidural anaesthesia was supplemented in eight patients with nitrous oxide and/or intravenous opioids.     

A comparison of the antibacterial activity of levobupivacaine vs. bupivacaine: an in vitro study with bacteria implicated in epidural infection

The purpose of the study was to compare the antibacterial activity of bupivacaine with levobupivacaine against a range of bacteria implicated in epidural infection to determine whether any differences existed between the two drugs. Concentrations of 0.125%, 0.25% and 0.5% bupivacaine and levobupivacaine were inoculated with suspensions of either Staphylococcus epidermidis, Staphylococcus aureus or Enterococcus faecalis. After incubation, the mixtures were plated onto blood agar and colony counts were recorded after a further period of incubation. The minimum bactericidal concentration of local anaesthetic against the three bacteria studied was found to be 0.25% for bupivacaine and 0.5% for levobupivacaine showing racemic bupivacaine to have a more potent antibacterial action than levobupivacaine. This finding suggests that the dextrobupivacaine isomer of racemic bupivacaine has a more potent antibacterial action than the levobupivacaine isomer.     

Stellate ganglion block with bupivacaine

Sympathetic blockade after stellate ganglion block with bupivacaine was assessed by liquid crystal thermography. The minimum concentration of bupivacaine required for successful block was between 325 and 406 mumol/litre. Further study of bupivacaine in a solution that contained potassium 5 mmol/litre showed that this reduced the minimum concentration of bupivacaine required for successful block to between 81 and 162 mumol/litre. We conclude that potassium has a major effect on the minimum concentration of bupivacaine required for sympathetic blockade.     

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.     

The alkalinisation of bupivacaine for intercostal nerve blockade

A double-blind randomised study was performed to investigate the effect of pH adjustment of bupivacaine, with adrenaline 1:200,000, on the duration of block and pain relief after intercostal nerve blockade following thoracotomy. One group (n = 10) received bupivacaine with adrenaline 1:200,000 (pH = 4.1) and the other (n = 10) received alkalinised bupivacaine with adrenaline 1:200,000 (pH = 6.9). There was no significant difference in block duration (mean 23.9 and 26.4 hours respectively) visual analogue pain scores or morphine usage. Patients were more likely to have a block during the first 12 hours if they received alkalinised bupivacaine (p less than 0.01, Chi-squared test). A progressive regression of block, not previously described, was observed, explicable by means of spread of local anaesthesia to adjacent intercostal nerves. Alkalinisation of bupivacaine with adrenaline for intercostal nerve blockade has little clinical benefit.     

Exaggerated epidural blockade resulting from unusual spread of bupivacaine in a patient with low back pain

A 75-year-old woman with chronic low back pain was given bupivacaine and methylprednisolone epidurally through a catheter in the L1-L2 interspace. An unusual spread of bupivacaine resulted in a block from the C4 to the L1 dermatome with no relief of back pain. Injection of a radiopaque dye and subsequent X rays showed a similar spread. The possible causes are discussed.     

Side-effects of epidural infusions of opioid bupivacaine mixtures

The incidence of side-effects occurring with epidural diamorphine (0.05 mg.ml-1), fentanyl (2.0 micrograms.ml-1), methadone (0.1 mg.ml-1), morphine (0.05 mg.ml-1) and pethidine (1.0 mg.ml-1) used by infusion in combination with bupivacaine has been compared. One hundred and sixty patients were studied, 32 receiving each opioid. The incidence of nausea and vomiting was significantly greater with morphine than fentanyl (p = 0.0097) and pethidine (p = 0.0021). The incidence of pruritis was significantly greater with morphine and diamorphine than with methadone (p = 0.012) and pethidine (p = 0.027). Morphine was also associated with a significantly greater incidence of urinary retention than pethidine (p = 0.012) and methadone (p = 0.025).     

Continuous thoracic epidural fentanyl for post-thoracotomy pain relief: with or without bupivacaine?

Twenty-five ASA 1 or 2 patients undergoing thoracotomy were entered into a prospective, randomised, double-blind study comparing thoracic epidural fentanyl alone and thoracic epidural fentanyl combined with 0.2% bupivacaine. Pain relief, pulmonary function and cardiovascular stability were assessed. Pain relief was superior in the bupivacaine series (p less than 0.05) during the first day after operation and this was accompanied by better oxygenation (p less than 0.05); the difference did not persist into the second day. Forced expiratory variables were reduced in both series to 50-60% of the values before operation throughout the study (p less than 0.05) and differences did not occur between the groups. The incidence of side effects attributable to epidural fentanyl was high, but hypotension did not occur. Small doses of bupivacaine administered together with fentanyl into the thoracic epidural space improve analgesia without causing hypotension.     

Cardiovascular effects of epidural local anaesthetics

The cardiovascular effects of 20 ml 0.75% bupivacaine with adrenaline 5 micrograms/ml injected epidurally were compared with those of 20 ml 0.75% ropivacaine with adrenaline. Cardiovascular measurements were performed with a transthoracic electrical bioimpedance monitor. The maximum mean arterial blood pressure decreased significantly from baseline values after both solutions, but the decrease after 20 minutes was more pronounced with bupivacaine (21%) than with ropivacaine (9.6%). Stroke volume increased significantly in both groups (52% for bupivacaine and 29% for ropivacaine). Cardiac output increased significantly from baseline values 2 minutes after epidural administration; the mean of the maximum increase was 64% for bupivacaine and 53% for ropivacaine (NS). The mean of the maximum increase of the ejection fraction was 13% in the bupivacaine group and 9% in the ropivacaine group, but was only significantly different from baseline values following bupivacaine. There was no difference in the onset time or height of the sensory block between the groups. The cardiovascular changes can be ascribed to sympathetic blockade and to systemic absorption of the local anaesthetics and adrenaline.