INFLUENCE OF ANESTHESIA AND MUSCLE-RELAXATION ON INTUBATING CONDITIONS AND SYMPATHOADRENAL RESPONSE TO TRACHEAL INTUBATION

Background: The study aimed to assess the relative influence of anaest hesia and muscle relaxation on intubating conditions and the haemodyna mic and catecholamine responses to tracheal intubation. Methods: Sixty ASA 1 or 2 patients were randomly assigned to one of four groups (15 patients each) that differed in the depth of anaesthesia (thiopentone plus fentanyl 2.5 mu g.kg(-2) or thiopentone alone) and the degree of vecuronium-induced neuromuscular block (100% or greater than or equal to 65%) at intubation. Muscle relaxation was measured at 0.1. Hz by me ans of mechanomyography, Heart rate (HR) and mean arterial blood press ure (MAP) were measured before and after induction of anaesthesia, and 1 min and 5 min following intubation, while adrenaline (A) and noradr enaline concentrations (NA) were determined from arterial blood sample s. Results: Intubating conditions were improved primarily by providing complete muscle relaxation at the adductor pollicis muscle (P<0.001) and to a lesser extent by adding fentanyl to thiopentone (P=0.04). The response of HR and MAP to tracheal intubation was attenuated mainly b y fentanyl (P<0.001). Complete muscle relaxation further diminished th e response of MAP to intubation (P=0.03). Changes in A and NA were dep endent on the depth of anaesthesia only (P less than or equal to 0.01) . Conclusion: The results of the study demonstrate that the sympathoad renal response to intubation is attenuated by adding fentanyl (2.5.kg( -1)) to an induction regimen with thiopentone, whereas provision of co mplete muscle relaxation at the adductor pollicis muscle is necessary to attain smooth intubating conditions.