Morton H. Maxwell

Renovascular Hypertension: Does the Renal Vein Renin Ratio Predict Operative Results?

Renal vein renin ratios from 56 hypertensive patients who were operated upon for unilateral stenosis of a main renal artery were compared to blood pressure response to a corrective operation. In patients with renal vein renin ratios greater then 2.0, the upper limits of normal for essential hypertension (95 per cent confidence limits), the cure/improvement rate approximated 90 per cent. However, in patients operated upon despite lesser ratios the cure/improvement rate was also high--83 per cent in our series and 57 per cent in collected reports from the literature. Thus, the test may be falsely negative in a high percentage of patients. Renal vein renin ratios would appear to be most useful in confirming but not necessarily in denying the functional significance of a renal artery stenosis.

A new automatic coil dialyzer system for ‘daily’ dialysis

Within the past decade, maintenance dialysis, with the passive-flow artificial kidney, has progressed from once a week 20 to 24 hour continuous dialysis (Hegstrom et al, 1961) to a twice a week dialysis schedule of 10 to 16 hours in an effort to curtail progressive neuropathy (Hegstrom et al, 1962). With the introduction of dialysis in the home, treatment was increased to three times weekly for about 8 hours per dialysis with the 2 layer Kiil dialyzer (Curtis et al, 1965). Sophisticated automatic equipment was developed to allow the patient to sleep overnight while on haemodialysis (Eschbach et al, 1966), and the length of dialysis remained 8 to 10 hours thrice weekly because peripheral neuropathy and difficulty in controlling hypertension in several patients occurred when less dialysis time per week was used (Eschbach et al, 1967). The total number of hours of dialysis per week at home was similar to the less frequent dialytic treatment, but the pre-dialysis BUN and serum creatinine values were generally lower with three times weekly dialysis than with twice weekly dialysis, and the patients were able to eat a more liberal diet in protein and sodium (Eschbach et al, 1967). This experience indicated that more frequent dialyses of the same total time per week was more effective clinically. Additionally, Bell and his associates (1965) in an analogue simulation of dialysis length and frequency concluded that daily short dialyses were very effective in lowering the average concentration of substances which rapidly equilibrate between the intracellular and extracellular fluid compartments. The present study was performed using initially an automatic fluid delivery system with 2 layer Kiil dialyzer to clinically evaluate the concepts and effectiveness of frequent short dialyses with this system and secondly an automatic patient operated fluid delivery system for coil type dialyzer was built to permit frequent short coil dialyses and, as a necessary economy measure, to re-use the coil dialyzer in a similar manner as that for the Kiil (Pollard et al, 1967) but modified so that dialysis ‘startup’ and ‘clean-up’ times would be minimized.

Role of the Renin-Angiotensin-Aldosterone System in the Regulation of Plasma Potassium in Chronic Renal Disease

The relationship between plasma potassium concentration and the renin-angiotensin-aldosterone system was evaluated in ten patients with chronic renal failure (creatinine clearance 10-56 ml/min). Under basal conditions and following various stimulation maneuvers, normokalemic patients demonstrated normal plasma renin and aldosterone levels. Five of six patients with hyperkalemia had diminished function of the renin-angiotensin-aldosterone system; their ability to conserve sodium during salt depletion was less than that of normokalemic patients. The data suggest that the maintenance of plasma potassium levels in these patients is dependent of the presence of a normally functioning renin-angiotensin-aldosterone system; aldosterone activity may be an important determinant of sodium conservation in patients with renal failure.

Extended hemodialysis in children with chronic renal failure

Five adolescents from 12 to 15 years of age with end-stage renal disease weredialyzed intermittently for periods of 1 to 6 months, using a low-resistance, pumpless, no-prime dialyzer (single layer of a standard two-layer Kiil). Minimal difficulties were observed with the silastic-teflon arteriovenous cannula. A relatively unrestricted diet was permitted with limitation of fluids to 1 L. and no added salt. Hypertension responded to removal of fluid by ultrafiltration. In adolescents weighing 28 to 52 kilograms, extended hemodialysis 2 to 3 times weekly for periods of 16 to 21 hours was found to be simple, without serious complications, and adequate to control the symptoms of uremia. This method of intermittent hemodialysis is recommended for children in preparation for live or cadaveric renal homotransplantation.

Cations and Hypertension: Sodium, Potassium, Calcium, and Magnesium

The association between sodium intake and hypertension has been studied for almost a century. More recently, it has been suggested that abnormalities in dietary intake of potassium, calcium, and magnesium may play a major role in the pathogenesis of hypertension. A critical analysis of selected data from animal and human studies is discussed.

Detection of Renovascular Hypertension: Saralasin Test Versus Renin Determinations

Angiotensin blockade was established in hypertensive patients with the competitive inhibitor saralasin and the blood pressure response was compared to prior renin determinations. Two patients with subsequently confirmed renovascular hypertension had normal peripheral renin and non-lateralizing renal vein renin ratios, yet both showed a clear-cut lowering of blood pressure after administration of the blocking agent, indicating the presence of renin-mediated hypertension. Thus, direct in vivo testing with saralasin appears to offer certain advantages over renin determinations.

Sorbent Regeneration of Peritoneal Dialysate: an Approach to Ambulatory Dialysis

Sorbent regeneration of peritoneal dialysate has been shown to be feasible in experimental and preliminary clinical studies and provides a realistic basis for the optimization of dialysis therapy and the potential development of an ambulatory dialysis system. Peritoneal dialysis efficiency can be significantly enhanced by continuous dialysate flow techniques and the mass transfer of uremic solutes can be theoretically augmented by the increased dialysis time made possible by a wearable design. Further optimization of end stage renal failure therapy may be achieved by the combined use of various methods for blood purification.

The diagnostic and therapeutic uses of saralasin in renal transplant hypertension.

Saralasin was used as a functional test of the renin-angiotensin axis in 4 renal transplant patients with hypertension. Blood pressure was recorded by an automatic recording device and plasma renin activity was measured by radioimmunoassay of angiotensin I. A positive saralasin test suggested renin-mediated hypertension despite normal peripheral renin levels in a 40-year-old man whose original kidney disease was nephrosclerosis. Since the blood pressure was refractory to intravenous sodium nitroprusside saralasin was used for 14 hours to control blood pressure before and after arteriography in the patient. Removal of the native kidneys markedly ameliorated the hypertension. A 35-year-old woman with transplant hypertension was responsive to angiotensin blockade only during a period of abrupt worsening of blood pressure associated with an acute rejection episode. Finally, 2 patients with advanced chronic rejection responded to saralasin administration. These studies confirm that 1) angiotensin blockade is a useful tool in the diagnosis of renin-dependent hypertension even when plasma renin levels are not elevated, 2) saralasin can be used to control renin-dependent forms of hypertension that are refractory to intravenous sodium nitroprusside therapy and 3) transplant hypertension associated with acute and chronic rejection appears to be renin-dependent.

Cations in essential hypertension

Sodium intake has been linked to the development and perpetuation of hypertension for almost a century. Nevertheless, considerable controversy over this relationship remain. More recently, the other major body cations, potassium, calcium and magnesium, have also been implicated. The evidence relating dietary sodium, potassium, calcium and magnesium intake to hypertension is summarized, and the present evidence for dietary modification of cation intake in the treatment of mild essential hypertension is evaluated.

Current Status of Dialysate Regeneration for the Treatment of Chronic Uremia

The removal of uremic solutes from dialysate by chemical compounds with adsorptive capacity provides a methodology for achieving a major reduction in the volume of dialysate necessary for conducting effective dialysis. Sorbent regeneration of dialysate permits a system with a small volume of recirculating dialysate to maintain maximal blood to dialysate concentration gradients and to potentially achieve mass transfer efficiency equal to that of a large volume recirculating or single pass dialysate flow system. Activated carbon, by virtue of its ability to adsorb organic nitrogenous compounds has served as the basic component of virtually all sorbent systems applied to the treatment of uremia. Yatzidis(1) demonstrated that activated carbon could adsorb creatinine, uric acid, phenols, indolic compounds, guanidines and organic acids. The adsorption of endogenous uremic metabolites of middle molecular weight configuration has also been demonstrated and there is presumptive clinical evidence derived from patients treated with sorbent systems that activated carbon probably adsorbs all organic uremic metabolites, known or as yet unidentified, which are of toxic significance(2–4). Unfortunately, there is one exception to this remarkable affinity of carbon for nitrogenous uremic metabolites.