"Haemodynamic Stability During Induction of General Anesthesia With Propofol and Remifentanil: A Randomized, Controlled, Double-blind Study Comparing Equipotent Prophylactic Doses of Ephedrine, Phenylephrine, Norepinephrine vs Placebo."

The LiDCOplus monitoring system (Lithium Dilutional Cardiac Output (LiDCO) Ltd., Cambridge, United Kingdom) is a minimally invasive monitor for measuring stroke volume (SV) using two different algorithms. The PulseCO (PulseCO ™, Cambridge, United Kingdom) is based on analyses of the the arterial pressure wave giving nominal values. The LiDCO uses lithium-dilution for calibration to give absolute values. In this trial, the investigators will use the PulseCO looking at relative changes in uncalibrated hemodynamic variables. Continual changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), heart rate (HR), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) will be measured.

Earlier studies have shown that propofol 2.5 mg/kg induction without opioid reduces CO (-15%), SV (-5 %), MAP (-33%) and SVR (-11%) and a slight reduction i HR. High-dose remifentanil anesthesia (2 microg/kg/min), in coronary patients reduced cardiac index (-25%), SV (-14%) and MAP (-39%) in a similar manner as propofol/remifentanil (propofol target 2 microg/ml and remifentanil 0.5 microg/kg/min), but systemic vascular resistance index decreased (-14%) in propofol/remifentanil combination.

Several procedures have been proposed to minimize the negative hemodynamic changes during induction. Administration of a crystalloid or a colloid did not prevent the decrease in MAP after induction of general anesthesia with propofol and fentanyl.

The hemodynamic effects in propofol-fentanyl anesthesia of preoperative ephedrine 0.07-0.15 mg/kg vs phenylephrine 1.5 microg/kg in valve surgery and concludes that ephedrine 0.07-0.1 mg/kg is safe and effective in counteracting hypotension. A dose of 0.15 mg/kg ephedrine is suggested for preventing hypotension during anesthesia induction with propofol 2.5 mg/kg and remifentanil 3 microg/kg.