Hypertension in terminal renal failure. Observations pre and post bilateral nephrectomy

Hormonal responses to acute volume changes in anephric subjects

The response of plasma aldosterone and cortisol concentrations to acute volume depletion was studied in 18 chronically anephric subjects and four recently nephrectomized subjects. Volume-depleting hemodialysis and hemodialysis without volume depletion produced insignificant changes in plasma aldosterone concentrations in chronically anephric subjects. Failure of volume depletion to increase plasma aldosterone concentrations in these subjects could not be attributed to reductions in plasma potassium concentrations and was in marked contrast to the effect on plasma cortisol concentrations, which increased significantly during volume depletion. Changes in plasma cortisol concentrations exhibited a negative correlation with changes in diastolic blood pressure (r = -0.712, P less than 0.001) and were shown to correspond to similar changes in plasma ACTH concentrations. Comparable increases in plasma cortisol and ACTH concentrations were also demonstrated in the studies on recently nephrectomized subjects, who, in contrast to chronically anephric subjects, exhibited increases in plasma aldosterone concentrations which were concordant with the changes in plasma cortisol and ACTH concentrations. These findings suggest that plasma aldosterone concentrations are regulated by a volume-sensitive mechanism in recently nephrectomized subjects but not in chronically anephric subjects. We interpret these data as evidence of aldosterone responsiveness to ACTH that persists for a limited time only after removal of the stimulus provided by the renin-angiotensin system. Volume-related changes in plasma cortisol and ACTH concentrations occur in the absence of stimulation by a functioning renin-angiotensin system.

Sequential hemodynamic changes in end-stage renal disease and the anephric state during volume expansion

The sequence of hemodynamic events during periods of salt- and water-loading was studied in anephric patients and those with end-stage kidney disease. The 10 patients studied showed four different sequential hemodynamic patterns: 1) no significant increase in blood pressure (BP) in two patients; 2) increase in BP associated with an increase in cardiac output and without change in total peripheral resistance in two patients; 3) increase in BP associated with an increase in total peripheral resistance from the beginning without an increase in cardiac output in five patients; and 4) increase in BP associated with an initial increase in cardiac output followed by an increase in total peripheral resistance in one patient. There was a significant positive correlation between BP and blood volume and between BP and total exchangeable sodium in the patients in whom salt- and water-loading increased the BP. It is concluded that during salt- and water-loading an initial rise in cardiac output is not necessary to increase BP and that a sustained rise in cardiac output does not always increase the total peripheral resistance. Mechanisms other than whole-body autoregulation play a role in increasing BP during salt- and water-loading in patients deprived of renal excretory function.

Hemodiafiltration

Four patients have been studied with maintenance hemodiafiltration. The predominant finding to date has been better control of blood pressure. The mechanism(s) for this improved blood pressure control are under study.

Treatment of uncontrolled hypertension by therapeutic renal infarction

Certain hemodialysis patients need to be made anephric, either surgically or physiologically. Bilateral renal infarction with shredded absorbable gelatin sponge (Gelfoam) was performed on a woman with malignant hypertension being maintained on chronic center dialysis who was too great a surgical risk for bilateral nephrectomy. Peripheral embolization complicated the procedure resulting in a forefoot amputation for dry gangrene two months later. Her postinfarction peripheral plasma renins remained elevated, and she remained hypertensive but was more easily managed with fewer drugs. This technique has been successfully used by others in 1 patient with chronic renal failure and heavy proteinuria and another with hypertension and a solitary kidney. If, as in our case, postinfarction plasma renins remain elevated and hypertension persists, bilateral nephrectomy could be performed at a later date or infarction could be repeated.

The present status of bilateral nephrectomy in transplant recipients

Routine use of bilateral nephrectomy in renal transplant patients has been replaced by a careful evaluation of the indications for the procedure and the increasing appreciation of the contributions of non-excretory kidneys. These contributions are identified and the indications are discussed. When bilateral nephrectomy is required the clear superiority of the bilateral simultaneous posterior approach over other techniques is documented.

Hemodynamic lesions in hypertension

Essential hypertension is increasingly recognized as a nonhomogenous disorder by various methods of study. The hemodynamic approach, coupled with clinical determination of the range and lability of blood pressure, has resulted in the description of several subgroups: labile hypertension with normal or elevated cardiac output, fixed or established hypertension with varying cardiac output and advanced hypertension with normal or low cardiac output. There is a tendency to postulate that these categories are stages of one disorder, but this remains to be proved. Still other patients have been described who may be further set off by exceptionally labile or hyperkinetic features. In some hypertensive patients, the peripheral resistance is normal; however, regardless of its numerical value, it is now considered to be increased if it fails to decrease normally in the presence of elevated cardiac output. Because an elevated cardiac output is the hemodynamic function that differentiates these groups, and renovascular hypertension as well, it is the focus of much current work. New interest in the central blood volume, the peripheral veins, and the portal veins and splanchnic circulation is focused on their connection with cardiac out-put. Newly appreciated, too, is the existence of parasympathetic inhibition in hypertension, which not only contributes to elevations of heart rate, cardiac output and possibly renin secretion, but also depresses baroreflex responses. Thus far, hemodynamic and endocrine mechanisms of hypertension have not been studied together, except possibly through the blood volume, which remains a highly controversial topic. In this paper, some recent work in the above areas is reviewed and emphasis is given to studies in man.