Renal Function in the Dog During Increased Blood Viscosity Produced by Simulated Altitude Exposure

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Abstract
Inter-mittent exposure to progressively lowered barometric pressure approx. doubled the relative viscosity of the systemic blood when measured in capillary tubes. Effective renal plasma flow (PAH) rose slightly in 3 dogs and changed little in the 4th. Since the plasma fraction of the blood was decreased (high hematocrit value) the calculated whole blood flow through the kidneys was approx. doubled. This was accomplished by vasodilatation which predominated in the afferent arterioles as shown by a greater increase in glomerular filtration (creatinine) than in effective renal blood flow so that the filtration fraction rose. Indirect evidence seems to indicate that the changes depend solely on blood viscosity and not on renal tissue changes after adaptation has become adequate.