Glomerular filtration is reduced by high tidal volume ventilation in an in vivo healthy rat model

Mechanical ventilation has been associated with organ failure in patients with acute respiratory distress syndrome. The present study examines the effects of tidal volume (V T) on renal function using two V T values (8 and 27 mL/kg) in anesthetized, paralyzed and mechanically ventilated male Wistar rats. Animals were randomized into two groups of 6 rats each: V T8 (V T, 8 mL/kg; 61.50 ± 0.92 breaths/min; positive end-expiratory pressure, 3.0 cmH2O; peak airway pressure (PAW), 11.8 ± 2.0 cmH2O), and V T27 (V T, 27 mL/kg; 33.60 ± 1.56 breaths/min; positive end-expiratory pressure, none, and PAW, 22.7 ± 4.0 cmH2O). Throughout the experiment, mean PAW remained comparable between the two groups (6.33 ± 0.21 vs 6.50 ± 0.22 cmH2O). For rats in the V T27 group, inulin clearance (mL·min-1·body weight-1) decreased acutely after 60 min of mechanical ventilation and even more significantly after 90 min, compared with baseline values (0.60 ± 0.05 and 0.45 ± 0.05 vs 0.95 ± 0.07; P < 0.001), although there were no differences between groups in mean arterial pressure or gasometric variables. In the V T8 group, inulin clearance at 120 min of mechanical ventilation remained unchanged in relation to baseline values (0.72 ± 0.03 vs 0.80 ± 0.05). The V T8 and V T27 groups did not differ in terms of serum thiobarbituric acid reactive substances (3.97 ± 0.27 vs 4.02 ± 0.45 nmol/mL) or endothelial nitric oxide synthase expression (94.25 ± 2.75 vs 96.25 ± 2.39 percent). Our results show that glomerular filtration is acutely affected by high tidal volume ventilation but do not provide information about the mechanism.

Efeito do furosemide e aminofilina na insuficiencia renal aguda pos-isquemica experimental. / Effects of furosemide and aminophylline in experimental post-ischemic acute renal failure

O efeito do furosemide e da aminofilina sobre a recuperacao da insuficiencia renal aguda foi estudado em ratos submetidos a isquemia renal por clampeamento da aorta,abaixo e acima da arteria renal esquerda, permanecendo o rim direito como controle. A administracao de altas doses de furosemide (100 mg/kg peso), antes de se proceder a isquemia renal,nao impediu a queda de filtracao glomerular e o efeito oligurico. O furosemide injetado em outros oito animais, apos a inducao da isquemia renal, nao alterou a taxa de filtracao glomerular (0,24 +/- 0,04 ml/min para 0,23 +/- 0,04 ml/min), produzindo apenas aumento da diurese e natriurese em seis dos animais estudados. A administracao de aminofilina, inibidor da adenosina, substancia vasoconstritora renal, cuja producao aumenta durante a isquemia renal, tambem nao aumentou a taxa de filtracao glomerular do rim pos-isquemico (0,09 +/- 0,04 ml/min para 0,10 +/- 0,02 ml/ min) e nem alterou a excrecao de agua e soluto. Estes dados permitem concluir que nem o furosemide e nem a aminofilina produzem uma recuperacao mais rapida da filtracao glomerular na insuficiencia renal aguda experimental e que apenas o furosemide pode transformar uma insuficiencia renal aguda oligurica em poliurica