[Curare and burns]

Abstract

Burns of more than 15% of the body surface area result in major physiological changes with an alteration of cardiovascular, pulmonary, hepatic and renal functions, as well as modifications in the pharmacokinetics and the pharmacodynamics of many drugs. Among these, a major change in the activity of muscle relaxants occurs which can be specific to this pathology. Succinylcholine is contra-indicated during recovery from a burn trauma because of a possible hyperkaliemic response, directly related to the dose, the post-burn delay and the area of burned body surface. The kaliemic response and the related cardiac complications remain unpredictable. The height of twich depression with small doses of succinylcholine such as 0.1 to 0.2 mg.kg-1, demonstrates the hypersensitivity to this agent and does cause neither metabolic disturbances nor cardiac arrest. Nevertheless, the administration of succinylcholine is contra-indicated for from the 5th day on at least two years after the burn injury. Conversely, the action of non-depolarizing muscle relaxants is characterized by a resistance, which is correlated to both the post-traumatic delay and the extent of the burned area. It starts on about the seventh day, reaches peak intensity between day 15 and day 40 and can persist up two years after the thermal injury. In the course of a burn, the so-called "immature" acetylcholine receptors, characterized by the substitution of the sub-unit epsilon by a protein gamma, increase at the level of the end plate areas and the extra-synaptic muscle membrane. These receptors explain both the hyperkaliemic response and the hypersensitivity to succinlycholine.(ABSTRACT TRUNCATED AT 250 WORDS)