The negative effect of artificial ventilation with positive pressure on renal function, expresses itself as a decrease of water and sodium excretion, being directly related with the raise of intrathoracic pressure. Factors participating in this process are: lowering in cardiac output, arousal of sympathic nervous system, increase in vasopressin action, activation of renin-angiotensin-aldosterone system and decrease of atrial natriuretic peptide release. This disorder of hydromineral metabolism produces: Impairment of hemodynamic equilibrium, favors the increase of hypoxia and renal failure. The effects of mechanical ventilation on renal function can be attenuated with the adoption of the following measures: a) techniques (use of low levels of PEEP and early disconnection of respirator); b) therapeutic (dopamine 2-3 mcg/kg/min, rational use of diuretics and fluids); y c) monitoring of renal function and hydro-mineral equilibrium.