In a group of normal subjects a relative respiratory acidosis in the cerebrospinal fluid (CSF) as compared with arterial blood was found. There was no significant gradient for bicarbonate concentrations between the two compartments. In normal subjects under high-altitude adaptation, arterial and CSF respiratory alkalotic shifts were similar. A concomitant fall in bicarbonate levels was slightly less in CSF than in arterial blood. In a group of patients with uremic acidosis the arterial-cerebrospinal H ion gradient was reversed, as bicarbonate was significantly less reduced in CSF relative to arterial blood. Hemodialysis led to restitution of the relative respiratory acidosis in CSF. These findings seem to indicate fast diffusion of CO2 across the cerebrospinal-arterial barrier. In contrast, diffusion of bicarbonate and/or H ion appears to be delayed and incomplete. CSF acid-base components are not likely to correlate with stimulation of the respiratory centers under these conditions. Submitted on March 12, 1962

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A Bs T R A C T The mechanism responsible for the anuria in acute renal failure after shock is still controversial.Suppressed glomerular filtration and/or tubular backdiffusion of the filtrate are major possible causes. In the present investigation, seven patients with acute anuria, three of these seven again in the polyuric phase, six patients with moderate renal impairment, four patients with chronic renal failure, and eight subjects with normal renal function were studied by a multiple indicatordilution method in which the total renal blood flow and renal distribution volumes of indocyanine green, ['Cr]-EDTA, and 'Na were determined. In normal subjects the average values for one kidney were 582 ml/min, 42 ml, 92 ml, and 139 ml, respectively. The measurements in the patients with moderate renal impairment were similar to those in the normal subjects, but were decreased in chronic renal failure. In acute anuria, the average values were 269 ml/min, 40 ml, 101 ml, and 114 ml and the kidney volume, estimated radiographically, was increased by 40%. When expressed as milliliters per milliliters kidney, the average distribution volume of 'Na was decreased from 0.64 to 0.38. This decrease is consistent with the hypothesis that suppressed filtration is largely responsible for the anuria and that back-diffusion is, at most, a contributory factor. The apparent contradiction between the relatively well-preserved total blood flow and the suppressed filtration may be due to a combination of afferent vasoconstriction and efferent vasodilatation. This view is supported by the observation that low filtration fractions were found in clearance measurements performed during the polyuric phase.

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