Adverse effects of intravenously administered drugs used in anaesthetic practice.

Adverse effects of intravenous anaesthetic drugs may be divided into local and general effects. The former include venous sequelae ranging from soreness on palpation on the day after the injection to thrombosis of the whole venous system of the arm. Frequency of venous sequelae for water-soluble anaesthetics 5 to 10%; drugs sparingly soluble in water are similar in this regard when solubilised in 'Cremophor EL'. Diazepam or etomidate dissolved in propylene glycol can produce venous reactions in about 25% of patients on the 3rd day and more by the 15th day if given directly into the vein, and are really only acceptable when injected in an infusion. The general adverse effects of anaesthetic agents include excitatory effects, as well as those on the cardiovascular and respiratory systems which are almost unavoidable. Excitatory effects are diminished by suitable premedication, and the cardiovascular and respiratory effects can be minimised by low dosage and slow administration. Cardiovascular effects of the muscle relaxants are also unavoidable with the drugs presently available, but further research should provide drugs with greater selectivity. More troublesome are the hypersensitivity reactions which occur with both the induction agents and the neuromuscular blocking drugs. These range in frequency from about 1 in 30,000 with the barbiturates to about 1 in 1000 with the 'Cremophor'-containing solutions of propanidid and alphaxalone/alphadolone. However, it appears that the barbiturate reactions are more severe and prolonged. The frequency of hypersensitivity reactions following muscle relaxants is difficult to assess because marked flushing is very common following tubocurarine and bronchospasm can frequently be due to passage of an endotracheal tube. In spite of the alarm created by these reactions, provided the patient is treated in the standard manner, the mortality should be low.