INTRODUCTION: Tracheal intubation is accompanied by an increased blood pressure and heart rate. The aim of this study was to find the most important source of this haemodynamic response, namely laryngoscopy or intubation.
METHOD: A standard induction technique was used for all patients. Eighty patients were randomly allocated to one of two groups, one group to undergo laryngoscopy followed by intubation (Group I), and the other laryngoscopy only of duration similar to intubation (Group L). Blood pressure and heart rate were recorded in the ward, before induction of anaesthesia and one, two, three, and four minutes after instrumentation.
RESULTS: The instrumentation times did not differ significantly (p = 0.20). Over time mean arterial pressures were significantly higher in Group I than in Group L (p = 0.038). Over time the ratios of mean blood pressure and heart rate relative to the preoperative heart rate were significantly greater in Group I than in Group L (p < 0.01).
CONCLUSION: Blood pressures and heart rates were significantly greater after laryngoscopy followed by intubation than after laryngoscopy of the same duration not followed by intubation. The induction technique, consisting of lignocaine, alfentanil, and propofol, may have attenuated expected increases in blood pressure but not increases in heart rate after intubation.