Effect of Norepinephrine Infusion on Hepatic Blood Flow During Goal-directed Haemodynamic Therapy.

Overview

Maintaining adequate blood pressure is important for survival of organs. Recent studies have demonstrated that higher blood pressures were necessary for prevention of acute kidney injury and myocardial injury after non-cardiac surgery. Hypotension after induction and maintenance of anesthesia is common. For maintaining adequate blood pressure in a euvolemic patient, vasopressor therapy is required. Norepinephrine (NOR) is commonly used to treat anesthesia-related hypotension. The hepatic circulation has a large number of alpha and beta adrenergic receptors and is very sensitive for adrenergic stimulation such as norepinephrine infusion. Animal studies (Hiltebrand et al.) suggest that NOR has only minimal effect on hepatic blood flow however the effect of NOR on hepatic blood flow in clinical surgical patients remains unclear. The aim of the study is to evaluate the effect of NOR on hepatic blood flow during. goal directed haemodynamic therapy.

All patients receive standardized anesthesia care for pancreas surgery according to the existing departmental protocol for these interventions. All patients receive individualized goal-directed haemodynamic therapy based on the transpulmonary thermodilution technique. At designated times, hemodynamic variables will be recorded. These include: * Heart rate (bpm) * Central venous pressure (mmHg) * Mean arterial pressure (mmHg) * Cardiac index (L/min/m2) * Pulse pressure variation (PPV) Blood flow and pressure measurements performed by the surgeon : * Hepatic flow : hepatic artery (HAF) and portal vein (PVF) * Pressure measurements in portal vein (PPorta) and caval vein (PCava) Both flow and pressure will be simultaneously recorded. To minimize the effect of ventilation on pressure, these measurements will be obtained during apnea. Between each flow measurement there will be a minimum of 5 minutes. NOR will be started at 0,1 mcg/kg/min and titrated according to its haemodynamic effect. After baseline MAP (which is \> 60 mmHg), NOR is targeted according baseline MAP. At T2, MAP is between 10 - 20 % above baseline (T1), at T3 MAP is between 20 - 30 % above baseline (T1).