Effects of mechanical ventilation on the kidney

Abstract

Mechanical ventilation with positive airway pressure has an inhibitory effect on the kidney, which results in a decrease of renal water and sodium excretion. Physical, hormonal, and nervous factors are involved in this process. The increase of intrathoracic pressure results in a decrease of atrial transmural pressures, cardiac output, and mean arterial pressure. Low-pressure and high-pressure baroreceptors are unloaded, and plasma vasopressin concentrations and sympathetic activity increase. The decrease of renal perfusion and the increase of renal nerve sympathetic activity stimulate the renin-angiotensin system. Angiotensin II formation stimulates aldosterone production. Whether a decrease of atrial natriuretic peptide plays a major role is not yet clear. The resulting (physiologic) reaction of the kidney is an increased reabsorption of water and sodium. The effects are directly related to the increase of intrathoracic pressure (which also depends on the level of positive end-expiratory pressure). They can be partially attenuated by extracellular volume loading.