Modification of aspects of the endocrine response to tracheal intubation by lignocaine, halothane and thiopentone.

The effects of two different concentrations of halothane (0.5 or 1.5%) and two different doses of thiopentone (4.5 or 10 mg kg-1) on the plasma concentrations of cortisol, growth hormone (GH) and prolactin (PRL) were studied in response to the stress of tracheal intubation. Additionally, the effect of the intratracheal administration of 4% lignocaine spray 2 ml was investigated. The study group included 48 healthy women. During a "light" level of halothane and thiopentone anaesthesia, the plasma concentration of cortisol increased in response to tracheal intubation in the patients who did not receive intratracheal analgesia. Topical analgesia with lignocaine prevented the increase in cortisol concentration and this would seem to indicate that the increase was caused by the stress of laryngoscopy and intubation. At a deeper level of halothane anaesthesia, and in association with the larger dose of thiopentone the increase in cortisol concentration was suppressed. GH did not change from the preanaesthetic value in any group and there were no differences between the control group and the study groups. PRL increased significantly in all groups. Increasing the dose of thiopentone caused a further increase in PRL concentration which indicated a direct stimulatory action of thiopentone on PRL release.