John F. Maher

Prediction of Glomerular Filtration Rate by Serum Creatinine and β2-Microglobulin

The reciprocal of serum creatinine concentration (1/Cr) is often used to predict glomerular filtration rate (GFR). Serum creatinine also varies with age, size, and muscle mass, and so it may inaccurately estimate GFR. The reciprocal of serum beta 2-microglobulin (1/beta 2mu) has been proposed as an alternative estimator of GFR. This study compares 1/Cr and 1/beta 2mu as predictors of GFR as measured by 125I-iothalamate clearance (CIOT) and creatinine clearance (CCr) in 29 subjects with a wide range of age, size and kidney function, and including 12 chronic hemodialysis patients. 1/beta 2mu was a better predictor of CIOT (r=0.90) and CCr (r=0.87) than 1/Cr (r=0.50 and 0.78) was. In fact, in the nondialysis population, 1/beta 2mu predicted CIOT (r=0.86) about as well as CCr predicted CIOT (r=0.87). Beta 2mu was less dependent on body size than Cr and unlike Cr, was not influenced by dialysis and did increase as GFR decreased with age. Beta 2mu can be useful as an alternative clinical estimate of GFR, particularly when Cr is considerably influenced by factors other than renal function.

Therapy of Iron Deficiency Anemia in Patients on Maintenance Dialysis

A controlled, prospective study compared the effectiveness of oral ferrous sulfate to intravenous iron dextran, each with and without concurrent intramuscular androgen for therapy of iron deficiency anemia in patients with chronic renal failure treated with maintenance hemodialysis. During the 12-week period of therapy, the patients who received oral ferrous sulfate and androgens showed an increment in their mean hematocrit of 16.3% and those who received oral ferrous sulfate alone had an increase of 8.3%. Patients treated with intravenous iron dextran androgens showed an increment in their mean hematocrit of 9.4% and those given iron dextran alone showed an increase of 3.5%. Serum ferritin levels increased with iron repletion but correlated inversely with the erythropoietic response. The serum ferritin assay provides a simple and reliable method to demonstrate iron repletion, and oral ferrous sulfate is the preferred method of iron repletion in compliant patients.

Augmented Peritoneal Mass Transport with Intraperitoneal Nitroprusside

Lightly restrained, alert New Zealand white rabbits underwent peritoneal dialysis by percutaneous instillation of standard dialysis solution with or without intraperitoneal nitroprusside. Corrected to a mean intraperitoneal dwell time of 36 minutes, mean clearances of creatinine and urea were 0.74 and 0.90 ml/kg/min in six rabbits. With intraperitoneal nitroprusside, 1.13 mg/kg clearances increased to 1.13 and 1.30 ml/kg/min (p less than 0.01) respectively. The 53% increment in creatinine clearance maintained the ratio clearance larger/smaller solute suggesting increased peritoneal permeability and/or area. Lower nitroprusside doses were less effective and not significantly above control. Nitroprusside also increased clearances during hypertonic peritoneal dialysis, but had no effect on osmotically induced water flux. Lavage studies demonstrated a persistent effect of nitroprusside after a single exposure and a sustained effect with repeated use.

Isoproterenol enhancement of peritoneal permeability.

As peritoneal dialysis is inefficient enouth to be time-consuming and sometimes clinically ineffective, we have evaluated pharmacologic enhancement of peritoneal permeability. Peritoneal dialyses were performed in New Zealand white rabbits by instillation of 50 ml/Kg of isotonic dialysis solution of standard composition. Mean peritoneal clearance of creatinine was 0.60 ml/Kg/min and urea was 0.80 ml/Kg/min, each decreasing as intraperitoneal dwell was prolonged (by .011 ml/Kg/min or less). With 0.04 micrometer/Kg of isoproterenol administered intraperitoneally, clearances increased to 0.91 and 1.30 ml/Kg/min (p less than 0.01). When isoproterenol was added to the dialysis solution one hour or more before instillation, the increment in clearances was less. Instillation of dialysis solution 24 hours after addition of a higher dose of isoproterenol (0.2 micrometer/Kg) did not increase clearances above control. No effect of isoproterenol on bulk flow of water, associated with the osmotic effect of dextrose, was demonstrated. As peritoneal clearances increased, the ratio creatinine clearance: urea clearance did not decrease, consistent with increased peritoneal permeability as well as blood flow.

Peritoneal Dialysis in Rabbits

Since vasodilators can restore toward normal the decreased peritoneal clearances associated with vascular disease, the influence of aminophylline on peritoneal solute transport was studied in unanesth

When Should Maintenance Dialysis Be Initiated

The present trend towared the use of maintenance dialysis in earlier stages of chronic renal failure, and more frequently in association with other morbid illness, raises the question of how well we understand the natural history and prognosis of chronic renal failure prior to total loss of renal function. Survival after serum creatinine exceeds 10 mg/dl is not necessarily very brief and is influenced by many variables. Morbidity and rehabilitation are poorly defined terms that should be approached as objectively and quantitatively as possible if the benefits of dialysis are to be assessed meaningfully.

Interrelation of Hemoperfusion, Plasma Clearance and Half Life

One goal of therapy of acute poisoning is to achieve a maximal rate of elimination. In the past two decades, forced diuresis and hemodialysis have been used for this purpose most successfully in the management of water soluble intoxicants (1). Lipid soluble poisons are removed only minimally, in part because of low clearances and large distribution spaces (2). Hemoperfusion, however, achieves higher clearances, even of lipid soluble toxins (3,4,5).