Adverse Effects and Drug Interactions Associated with Local and Regional Anaesthesia

Abstract

Systemic and localised adverse effects of local anaesthetic drugs usually occur because of excessive dosage, rapid absorption or inadvertent intravascular injection. Small children are more prone than adults to methaemoglobinaemia, and the combination of sulfonamides and prilocaine, even when correctly administered, should be avoided in this age group. The incidence of true allergy to local anaesthetics is rare. All local anaesthetics can cause CNS toxicity and cardiovascular toxicity if their plasma concentrations are increased by accidental intravenous injection or an absolute overdose. Excitation of the CNS may be manifested by numbness of the tongue and perioral area, and restlessness, which may progress to seizures, respiratory failure and coma. Bupivacaine is the local anaesthetic most frequently associated with seizures. Treatment of CNS toxicity includes maintaining adequate ventilation and oxygenation, and controlling seizures with the administration of thiopental sodium or benzodiazepines. Cardiovascular toxicity generally begins after signs of CNS toxicity have occurred. Bupivacaine and etidocaine appear to be more cardiotoxic than most other commonly used local anaesthetics. Sudden onset of profound bradycardia and asystole during neuraxial blockade is of great concern and the mechanism(s) remains largely unknown. Treatment of cardiovascular toxicity depends on the severity of effects. Cardiac arrest caused by local anaesthetics should be treated with cardiopulmonary resuscitation procedures, but bupivacaine-induced dysrhythmias may be refractory to treatment. Many recent reports of permanent neurological complications involved patients who had received continuous spinal anaesthesia through a microcatheter. Injection of local anaesthetic through microcatheters and possibly small-gauge spinal needles results in poor CSF mixing and accumulation of high concentrations of local anaesthetic in the areas of the lumbosacral nerve roots. In contrast to bupivacaine, the hyperbaric lidocaine (lignocaine) formulation carries a substantial risk of neurotoxicity when given intrathecally. Drugs altering plasma cholinesterase activity have the potential to decrease hydrolysis of ester-type local anaesthetics. Drugs inhibiting hepatic microsomal enzymes, such as cimetidine, may allow the accumulation of unexpectedly high (possibly toxic) blood concentrations of lidocaine. Reduction of hepatic blood flow by drugs or hypotension will decrease the hepatic clearance of amide local anaesthetics. Special caution must be exercised in patients taking digoxin, calcium antagonists and/or beta-blockers.

Neuropathic pain: Early spontaneous afferent activity is the trigger

“…Although previous studies reported that the injected soluble form of bupivacaine can cause cardiotoxicity (Covino, 1986;Graf, 2001;Mather and Chang, 2001) and neurotoxicity (Barsa et al, 1982;Li et al, 1985;Naguib et al, 1998;Sakura and Hashimoto, 1997), in our studies no animal showed cardiac problems. In addition, there was no significant change in the histology of sciatic nerve blocked with bupivacaine OH compared with normal sciatic nerve.…”

Fatal bupivacaine overdose through intrathecally positioned epidural catheter

“…Bupivacaine is more cardiotoxic than other commonly used local anaesthetics [12], with a narrow gap between convulsant and lethal doses in experimental studies [13]. The cardiotoxic effects may be due to direct effect on the myocardium or mediated through the central nervous system [14].…”

Beta-bloqueadores em anestesiologia: aspectos farmacológicos e clínicos

“…20 Os beta-bloqueadores também podem modificar o metabolismo de outros medicamentos, por diminuírem o débito hepático e/ou o metabolismo oxidativo. Por exemplo, o propranolol diminui a depuração da lidocaína em 30% 21 e do diazepam em 17% 22 . O propranolol também reduz a depuração pulmonar de fentanila 23 .…”

“…Beta-blockers may also change the metabolism of other drugs by decreasing liver output and/or oxidative metabolism. As an example, propranolol decreases lidocaine clearance in 30% 21 and diazepam in 17% 22 . Propranolol also decreases lung fentanyl clearance 23 .…”