Adverse effects of regional anaesthesia in children.

True complications of regional block procedures pertain to the performance of the block technique and the local anaesthetic. Such complications include lesions caused by the device used, and many of these complications can be avoided by using specifically designed devices.Complications related to the local anaesthetic solution mainly consist of local and systemic complications. Local toxicity has mainly been reported in adults following spinal administration of 5% lidocaine (lignocaine), a drug that is not usually used in children. Systemic toxicity consists of CNS and cardiovascular complications, methaemoglobinaemia and allergic reactions. Systemic toxicity has special features in children, especially in those <1 year old. Infants have a much higher free serum concentration of local anaesthetics than older children and adults, and are more prone to the deleterious effects of local anaesthetics. Additionally, as regional blocks are usually performed under general anaesthesia in children, signs of CNS toxicity may be concealed. Because of their higher heart rate, newborns and infants are thought to be more prone to the phasic block produced by tertiary amine agents such as bupivacaine than are adults. Serum concentrations at which bupivacaine (and etidocaine) exert cardiac toxicity seem to be similar to those producing CNS toxicity. As there is an increased threshold for CNS toxicity in infants plus an increased (or equal) sensitivity to bupivacaine cardiotoxicity, cardiac signs may not be preceded by any sign of CNS toxicity. Cardiac complications include: (i) arrhythmias with high degree conduction block, major QRS widening, torsade de pointes, and ventricular tachycardia related to re-entry phenomena; and (ii) major vascular collapse favoured by a concomitant decrease in the myocardial contractile force. Other complications of regional block procedures result from poor selection of agent, and inadequate safety precautions and monitoring of the patient, especially during the postoperative period. There are 2 other groups of disorders often reported as complications of regional anaesthetics: (i) effects that were not anticipated by the anaesthetist because of a lack of knowledge of all the consequences of the technique used; and (ii) complications attributed to a concomitant regional block procedure but with no established, sometimes even improbable, causal link with the regional technique. The overall morbidity of regional anaesthesia in children is low. Sound selection of local anaesthetics, insertion routes and block procedures, together with appropriate and careful monitoring, should prevent any major undesirable effects and enable regional anaesthesia to be a well tolerated and effective tool to overcome pain associated with minimal morbidity.