The Effect of Crystalloids and Colloids on Visceral Blood Flow

Patients often require fluid replacement during and after an operation. This is usually given through veins in the arm using an intravenous cannula and doctors have traditionally used fluid containing sodium chloride (saline). However accumulating evidence suggests that large infusions of saline are associated with adverse physiological effects including acidification of the blood and a rise in potassium and chloride levels. Studies in animals have shown that high levels of chloride in the blood and excess saline can cause blood vessels in the kidney to constrict leading possibly to a decrease in kidney function. Improvement in acid-base balance and kidney function may be observed with balanced solutions containing constituents that are more closely matched to the body's own fluid composition. However, little is known about the physiological effects of these solutions as they have only recently been developed. Magnetic resonance imaging (MRI) is a radiological modality which can now assess blood flow and supply of the kidney noninvasively without the need for the injection of radiological dyes known as contrast agents. This is now of major importance due to the possible adverse effects of MRI contrast agents leading to Nephrogenic Systemic Fibrosis (NSF), a progressive disease which has been observed in some kidney patients after receiving 'gadolinium based' contrast agents. This has therefore led to increased interest and demand for noncontrast based imaging methods. In this study we aim to compare the effects of balanced versus unbalanced fluid infusions in healthy human volunteers: We will aim to measure: 1. Blood biochemical composition and acidity 2. Kidney function and supply as measured by dynamic MRI