Effect of Dehydration on Renal Blood Flow in Dog

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Abstract
The effect of dehydration on intrarenal blood flow was investigated in 11 dogs, using polarographic determination of H2-gas desaturation for measuring local blood flow in inner cortex (ICF) and outer cortex (OCF). Dehydration was induced by 48 h water deprivation + 2-300 mg ethacrynic acid (EA) orally the day before the experiment. Compared to a control group (n = 9) ICF was markedly reduced to 2.40 .+-. 0.47 ml/min .times. g (control 3.23 .+-. 0.64); OCF 3.29 .+-. 0.80 ml/min .times. g was nearly unchanged (control 3.59 .+-. 0.85). The ratio OCF/ICF was increased to 1.37 (1.11). Further dehydration by hypertonic peritoneal dialysis for 3 h increased Hct [hematocrit] to 60 .+-. 4 and further reduced OCF and ICF, without significant change of the OCF/ICF-ratio. At Hct above 55 sudden and intermittent changes in local cortical blood flow were recorded randomly at individual electrode sites, showing ischemic periods lasting for 1-60 min. Such flow changes were not accompanied by changes in RBF. Moderate dehydration causes a greater reduction of ICF than of OCF. Severe dehydration also gives rise to patchy, intermittent ischemia in both cortical layers.