Changes in Measured Plasma Volume, Glycocalyx and Atrial Natriuretic Peptide During Anaesthesia

Changes in Measured Plasma Volume, Glycocalyx and Atrial Natriuretic Peptide During Anaesthesia, a Randomised Clinical Trial

The arterial blood pressure is thought to affect the ratio between filtration and reabsorption of fluids in the circulating blood volume and thereby the plasma volume. During induction of anesthesia blood pressure, hemoglobin level and hematocrits decreases and the plasma volume increases. The aim of the study is to evaluate weather a maintained blood pressure with norepinephrine during anesthesia induction reduces the increase in 125 iodine-labeled human serum albumine (125I-HSA) measured plasma volume.

24 patients scheduled for coronary artery bypass surgery will be included and randomized to receive either norepinephrine in the dose needed to maintain pre-anesthesia blood pressure or to a control group and receive norepinephrine only if mean arterial pressure decreases below 60 mmHg. Equal anesthesia in both groups will be monitored. No fluids will be infused.

Changes in vascular resistance and cardiac output will be measured with thermodilution and changes in plasma volume will be measured with 125I-HSA.

Endothelial cell function will be evaluated by measuring leakage of 125I-HSA and the plasma concentration of endothelial cell markers. Hormonal effects will be evaluated by measuring the plasma concentration of atrial natriuretic peptide (ANP). Shedding of glycocalyx will be evaluated by measuring heparan sulphate. The level of fibrinogen and platelet function will be evaluated by thromboelastography/multiplate.

Inclusion Criteria:

• Elective coronary artery surgery patients

Exclusion Criteria:

• Age under 40 years
• Untreated hypertension
• A reduced left ventricular systolic ejection fraction of 45% or less
• Diabetes mellitus
• Former stroke and/or a known carotid artery stenosis