Timing of peak pressor response following endotracheal intubation

The study was designed to measure the timing of the peak cardiovascular response following laryngoscopy and endotracheal intubation. Thirty patients ASA 1 or 2 were studied, with arterial pressure being continuously monitored using the Ohmeda 2300 Finapres. Patients were randomised to receive either propofol 2.5 mg.kg-1 (Group A) or thiopentone 4.5 mg.kg-1 (Group B). The mean time to complete laryngoscopy and intubation was 26 s in Group A and 20 s in Group B. The peak response occurred on average 31 s after the start of the stimulus in Group A and after 32 s in Group B. In 8 out of the 30 cases the peak response occurred during the period of stimulation. Systolic pressure fell on average by 2.6 kPa (20 mmHg) (range 0 to 5.9 (45 mmHg)) from its peak value to the value measured at the 1-min time mark in the propofol group, and by 2.3 kPa (17 mmHg) (range 0.4 (3 mmHg) to 3.8 (29 mmHg)) in the thiopentone group. We conclude that the use of slow arm-cuff-based arterial pressure measurement techniques may miss important hypertensive episodes during laryngoscopy and endotracheal intubation. The effectiveness of agents in obtunding the pressor response may thus be misinterpreted.