Hemodynamic impact of increasing time between fentanyl and propofol administration during anesthesia induction: a randomised, clinical trial

Anesthesia induction can produce severe propofol dose-dependent hypotension. Fentanyl coadministration reduces the catecholaminergic response to orotracheal intubation allowing propofol dose reduction. The aim of this study is to determine whether the hemodynamic response is improved by increasing the time between fentanyl and propofol administration and reducing the dose of the latter without increasing the time to achieve optimal hypnosis. After approval by the Research Ethics Committee, patients undergoing non-cardiac surgery with endotracheal intubation were randomized by a computer-generated table into six time-dose groups (1 or 2 minutes/1, 1.5, or 2 mg.kg-1 of propofol). Patients with high bronchoaspiration risk, a difficult airway, hemodynamic instability, or anesthetic allergies were excluded. After giving intravenous fentanyl (2 μg.kg-1), each group received different doses of propofol after 1 or 2 minutes. Noninvasive blood pressure (BP) and heart rate (HR) were measured at pre-induction, pre-intubation, and post-intubation. Time to hypnosis (bispectral index < 60) was also recorded. Of the 192 recruited patients, 186 completed the study (1 min group n = 94; 2 min group n = 92). It was observed that HR and BP decreased after propofol administration and increased after intubation in all groups (p < 0.0001). In patients over 55 years, the 2 min – 2 mg.kg-1 group showed the greatest systolic BP reduction (36 ± 12%) at pre-intubation, while the 1 min – 1.5 mg.kg-1 group showed the least hemodynamic alteration between pre- and post-intubation (-4 ± 13%). No significant differences were found in younger patients or in the time to reach hypnosis between the six groups. While no cases of severe bradycardia were recorded, 5,4% of the sample required vasopressors. Increasing the time between the administration of fentanyl and propofol by up to two minutes results in greater hypotension in patients over 55 years.