Complications of regional anaesthesia Incidence and prevention.

The complications of failure, neural injury and local anaesthetic toxicity are common to all regional anaesthesia techniques, and individual techniques are associated with specific complications. All potential candidates for regional anaesthesia should be thoroughly evaluated and informed of potential complications. If there is significant risk of injury, then these techniques should be avoided. Central neural blockade (CNB) still accounts for more than 70% of regional anaesthesia procedures. Permanent neurological injury is rare (0.02 to 0.07%); however, transient injuries do occur and are more common (0.01 to 0.8%). Pain on injection and paraesthesiae while performing regional anaesthesia are danger signals of potential injury and must not be ignored. The incidence of systemic toxicity to local anaesthetics has significantly reduced in the past 30 years, from 0.2 to 0.01%. Peripheral nerve blocks are associated with the highest incidence of systemic toxicity (7.5 per 10000) and the lowest incidence of serious neural injury (1.9 per 10000). Intravenous regional anaesthesia is one of the safest and most reliable forms of regional anaesthesia for short procedures on the upper extremity. Brachial plexus anaesthesia is one of the most challenging procedures. Axillary blocks are performed most frequently and are safer than supraclavicular approaches. Ophthalmic surgery is particularly suited to regional anaesthesia. Serious risks include retrobulbar haemorrhage, brain stem anaesthesia and globe perforation, but are uncommon with skilled practitioners. Postdural puncture headache remains a common complication of epidural and spinal anaesthesia; however, the incidence has decreased significantly in the past 2 to 3 decades from 37 to approximately 1%, largely because of advances in needle design. Backache is frequently linked with CNB; however, other causes should also be considered. Duration of surgery, irrespective of the anaesthetic technique, seems to be the most important factor. The syndrome of transient neurological symptoms is a form of backache that is associated with patient position and use of lidocaine (lignocaine). Disturbances of micturition are a common accompaniment of CNB, especially in elderly males. Hypotension is the most common cardiovascular disturbance associated with CNB. Severe bradycardia and even cardiac arrest have been reported in healthy patients following neuraxial anaesthesia, with a reported incidence of cardiac arrest of 6.4 per 10 000 associated with spinal anaesthesia. Prompt diagnosis, immediate cardiopulmonary resuscitation and aggressive vasopressor therapy with epinephrine (adrenaline) are required. New complications of regional anaesthesia emerge occasionally, e.g. cauda equina syndrome with chloroprocaine, microspinal catheters and 5% hyperbaric lidocaine, and epidural haematoma formation in association with low molecular weight heparin. Even so, after 100 years of experience, most discerning physicians appreciate the benefits of regional anaesthesia.

Comparison of 0.25% S(-)-bupivacaine with 0.25% RS-bupivacaine for epidural analgesia in labour.

We have compared the efficacy of 0.25% S(-)-bupivacaine with 0.25% RS-bupivacaine in providing epidural analgesia for labour in a randomized, multicentre, double-blind study. Analgesia was initiated with 10 ml of the study solution and maintained with 10-ml top-ups. We studied 137 women and treatments were found to be equivalent for onset, duration and quality of block. Median onset of pain relief was 12 min for both drugs and median duration was 49 (range 3-129) min and 51 (7-157) min for S(-)-bupivacaine and RS bupivacaine, respectively. The estimated treatment difference for duration of pain relief was -4 (90% CI -13, 6) min. Thirty patients failed to achieve pain relief after the first injection (20 patients after S(-)-bupivacaine and 10 after RS-bupivacaine; P = 0.039). However, median duration of pain relief from the first top-up was 82 (range 3-164) min for S(-)-bupivacaine and 76 (22-221) min for RS-bupivacaine. There were no significant differences in the quality of analgesia, as assessed by the investigators. There were no significant differences in the extent of sensory block, percentage of patients with motor block or incidence of adverse events.

Extradural S(-)-bupivacaine: comparison with racemic RS-bupivacaine.

Bupivacaine has a chiral centre and is currently available as a racemic mixture of its two enantiomers: R(+)-bupivacaine and S(-)-bupivacaine. Preclinical studies have demonstrated that there is enantiomer selectivity of action with the bulk of central nervous system and cardiovascular toxicity residing with the R(+) isomer. The aim of this study was to compare the clinical efficacy and safety of S(-)-bupivacaine with racemic RS-bupivacaine for extradural anaesthesia. We studied 88 patients undergoing elective lower limb surgery under lumbar extradural anaesthesia who received 15 ml of 0.5% or 0.75% S(-)-bupivacaine, or 0.5% RS-bupivacaine in a randomized, double-blind study. There was no difference in onset time, maximum spread of sensory block or intensity of motor block between the three groups. Duration of sensory block was significantly longer for 0.75% S(-)-bupivacaine. We conclude that S(-)-bupivacaine has similar local anaesthetic characteristics to RS-bupivacaine when used for extradural anaesthesia.

Transient radicular irritation with intrathecal plain lignocaine.

BACKGROUND: The aetiology of the syndrome known as transient radicular irritation (TRI) has generated much interest. METHOD: A 50-year-old woman had right knee arthroscopy performed under spinal anaesthesia with 1% plain lignocaine. RESULT: At home, on the night of the procedure, she was woken by severe, bilateral cramp-like pain in both buttocks radiating to her thighs. Neurological examination of her lower limbs, the next morning, was entirely normal. The pain lasted for 36 h and a full recovery was made. CONCLUSION: This case of transient radicular irritation occurred in a patient given 40 mg of subarachnoid lignocaine (the lowest dose of isobaric preservative-free lignocaine reported thus far that has been associated with these symptoms). Her operation was performed in the supine position. The lack of confounding factors (hyperbaricity, high concentration solution, preservatives, lithotomy position) suggests lignocaine as a possible cause, yet current theories do not fully explain the aetiology of transient radicular irritation. Results from large-scale epidemiological studies will hopefully provide insight into the cause of this problem.

Does pre-incisional thoracic extradural block combined with diclofenac reduce postoperative pain after abdominal hysterectomy?

In a double-blind, randomized study, we investigated 40 patients undergoing abdominal hysterectomy; patients received 0.5% plain bupivacaine 20 ml via a low thoracic extradural catheter and a diclofenac suppository (100 mg), either 30 min before incision (group 1) or 30 min after incision (group 2). All patients received a standard general anaesthetic and no opioid was used before or during operation. Postoperative analgesic requirements were measured using a patient-controlled analgesia (PCA) system. Pain was assessed using a visual analogue scale (VAS) and a verbal pain score (VPS) on movement up to 48 h after operation. There was no significant difference in the time to first request for morphine but consumption of morphine was significantly greater in group 1 at all times except 24 h. There were no significant differences in VAS and VPS pain scores, although both scores were consistently higher in group 1. Patient satisfaction with the quality of analgesia, at 24 h, demonstrated no significant difference between the two groups. The combination of extradural block and diclofenac suppository given before operation did not appear to produce a clinically effective pre-emptive analgesic effect.