Nitric oxide and endothelin concentrations during intravenous infusion of urological irrigating fluid

To study the possible role of two vasoactive mediators, nitric oxide (NO) and endothelin, in the hemodynamic alterations following absorption of irrigating fluid.

Twelve male volunteers received an intravenous administration of 1.5% glycine, given at a rate of 0.5 ml/kg/min for 30 min. Infusions of 3% mannitol served as controls. Blood pressure, heart rate and the plasma levels of endothelin and nitrite/nitrate (an index of NO activity) were measured before, during and after the infusions.

The endothelin concentration at baseline correlated inversely with the systolic arterial pressure (p<0.01). No qualitative differences were found between the two fluids with respect to the NO and endothelin responses, but the observed variations indicated the role of the two fluids during volume loading. In general, an elevation of blood pressure during the infusions was associated with an increase in the endothelin concentration, while a sustained elevation 30 min later was accompanied by a decrease in the NO activity. Reductions in the blood pressure and heart rate were associated with decreased NO concentrations.

The endothelin/NO axis may increase blood pressure in response to volume loading; it also acts to stabilize the circulation at baseline and probably also when the blood pressure decreases.