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.