Anaesthesia awareness

Sandin R H et al 2000 Awareness during anaesthesia Whiteside J B, Wildsmith JAW 2001 Developments in... 

The nerve poisons, or neurotoxins, are wonderfully well designed to act quickly to immobilise the snake s prey or attacker. They inhibit the formation or conduction of nerve impulses and so prevent movement. This is a particularly sinister approach to securing prey, because the unfortunate animal is immobilised while not being killed. Indeed, it is likely that in some cases the prey is conscious and aware, but simply unable to move because the venom acts as a motor nerve block (a similar approach is used in anaesthesia to facilitate muscle relaxation, particularly in abdominal surgery and one hears of horror stories of immobilised, helpless patients being subjected to surgery while not properly anaesthetised — this is how the snake s prey might feel ). 

B. Several studies suggest that beta blockers, such as atenolol and esmolol, given before induction reduce the anaesthetic dose requirement and may potentiate hypnosis. However, there are concerns that reducing the dose of anaesthetic may increase the risk of intra-operative awareness and it has been suggested that the use of BIS to predict the depth of anaesthesia in the presence ofbeta blockers may not be valid.There is a possibility that acute as well as chronic administration ofbeta blockers may prevent perioperative cardiac complications, but more study is needed on this. ... 

Information is fairly sparse, but these interactions appear normally to be of relatively minor importance. Be aware that changes in neuromuscular blockade (increases or decreases) can occur if beta blockers are used, but they seem to be unpredictable, and then often only modest in extent. The possible combined cardiac depressant effects of beta blockade and anaesthesia are well known (see Anaesthetics, general + Beta blockers, p.97). These effects may not be prevented when a neuromuscular blocker is used that has little or no effect on the vagus (such as atracurium or vecuronium). 

One case of anaphylactic shock (27 ) and one of generalized exfoliative dermatitis (28 ) after the use of lidocaine as a local anaesthetic have been described. The intravenous administration of lidocaine in patients with myocardial infarction sometimes also leads to undesirable side effects, of which hypotension is the best known. The problem is mainly one for the cardiologist, but since inadvertent intravenous injection during local anaesthesia may occur, the anaesthetist must be aware of it. A case of sinusbradycar-dia after a bolus injection of 50 mg (29 -) and an atrioventricular block after 800 mg, given in the course of 12 hours (30 ) have been described. Two fatalities, one due to ventricular fibrillation after 50 mg and one to sinus arrest after 100 mg, have been re-... 

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