Effect of Dehydration on Renal Blood Flow in Dog

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) per os the day before the experiment. Compared to a control group (n = 9) ICF was markedly reduced to 2.40 ± 0.47 ml/min×g (control 3.23 ± 0.64) whereas OCF 3.29 ± 0.80 ml/min×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 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 to 60 min. Such flow changes were observed in 13 of 14 expts. and were not accompanied by changes in RBF. It is concluded that moderate dehydration causes a greater reduction of ICF than of OCF. Severe dehydration gives in addition rise to patchy, intermittent ischemia in both cortical layers.