Amphotericin selectively increases peritoneal ultrafiltration

Because amphotericin B is known to affect transport rates across biologic membranes, the effects of this agent on transport parameters in an animal model of peritoneal dialysis were investigated. When amphotericin B in doses ranging from 0.5 to 25 mg/kg was instilled intraperitoneally with commercial dialysis solution, diffusive clearances of phosphate and urea did not differ from control values measured in the same animals, and only a modest increase in potassium clearance was detected. Ultrafiltration due to the osmotic gradient induced by the dextrose content of the dialysis solution increased significantly to 0.31 mL/kg/min with amphotericin B, compared with control values of 0.18 mL/kg/min. The drug did not affect dextrose transport and the osmotic gradient did not differ in the two groups. Hence, the ultrafiltration coefficient was higher with amphotericin B (14 microL/kg/min/mosm), than during control dialyses (6 microL/kg/min/mosm). Increased water flux was detected at the lowest dose and there was no dose relationship over the range studied. Amphotericin B may be the type of agent that will be clinically useful in patients with reduced peritoneal ultrafiltration capacity, and safer analogues should be explored.

Acceleration of peritoneal solute transport by cytochalasin D

Because cytochalasin D affects intercellular junctions the effect of this agent on peritoneal transport was investigated in normal rabbits. Using commercially available dialysis solution, short-term control peritoneal dialyses were compared in the same animals to dialyses in which cytochalasin D was added intraperitoneally. A dose (325-920 micrograms/kg) dependent increase in peritoneal clearances of urea (49% increment at high dose) and of creatinine (67% increment) occurred when cytochalasin D was added. When solute transport was highest at the maximal dose, osmotically induced ultrafiltration decreased significantly to 33% of control values. Cytochalasin D induces aberrations in solute transport that resemble those accompanying and occasionally following peritonitis.

Mesangial proliferative glomerulonephritis with IgM deposits. Clinicopathologic analysis and evidence for morphologic transitions

To determine the natural history of mesangial proliferative glomerulonephritis (MesPGN) with IgM deposits and its relationship to minimal change disease (MC) and focal segmental glomerulosclerosis (FGS), we studied the clinical characteristics and outcome in 20 patients with MesPGN, 8 with MC, and 10 with FGS. IgM deposits were present in glomeruli of all MesPGN patients. Progression to FGS was documented in 2 patients with MesPGN, 1 of whom developed renal failure. Transition from MC to MesPGN occurred in 1 patient. 2 MC patients developed FGS, with decline in renal function in 1 of them. These data suggest the possibility of histologic transition from MC to FGS directly or through the stage of MesPGN.

Glycosylated hemoglobin in patients treated by chronic dialysis

A glycosylated hemoglobin (HbA1) test was used to evaluate the role of dialysate glucose in the development of carbohydrate intolerance and hyperlipidemia in chronic hemodialysis patients and chronic peritoneal dialysis patients. HbA1 levels were significantly elevated in all groups of patients. HbA1 levels were not ameliorated with 8 weeks of glucose-free hemodialysis. There was no correlation between HbA1 and serum glucose, triglycerides, or cholesterol. Thus, HbA1 elevation cannot be explained solely by glucose reabsorption from dialysate. This test is helpful in the detection of carbohydrate intolerance, but its usefulness in evaluation of hyperlipidemia of dialysis patients is uncertain.

Peritoneal dialysis in the treatment of severe hypercalcemia

A 56-year-old man with multiple myeloma and compromised renal function underwent peritoneal dialysis for the treatment of severe hypercalcemia. During dialysis, peritoneal clearances of total calcium, unbound calcium, urea, and creatinine were assessed. Clearances of total calcium (4.8 +/- 0.4 ml/min) and unbound calcium (7.8 +/- 0.5 ml/min) were shown to vary directly with the clearances of urea (15.5 +/- 1.3 ml/min) and creatinine (8.5 +/- 0.8 ml/min). Despite relatively low clearances of all these solutes, during the period of 42 hours, 1,638 mg of calcium was removed in the dialysate and total serum calcium decreased from 17.6 mg/dl to 10.2 mg/dl. Our data indicates that peritoneal dialysis is an effective adjunct in controlling severe hypercalcemia and should be considered when other forms of therapy are inadequate.

Augmentation of peritoneal mass transport by dopamine: comparison with norepinephrine and evaluation of pharmacologic mechanisms

The effect of catecholamines on transport during peritoneal dialysis was studied in unanesthetized rabbits. Intravenous I-norepinephrine consistently decreased peritoneal clearances of urea and creatinine to 84% of control values or less but did not affect osmotically induced water flux. Comparable pressor doses of dopamine increased clearances of urea and creatinine to 145% of control values, whereas osmotic fluid flux increased only slightly. Dopamine also increased urea transport when administered intraperitoneally. The augmentation of solute transport by dopamine was unaffected by simultaneous administration of propranalol, was decreased by phentolamine, and was abolished by haloperidol. Dopamine may be preferable toI-norepinephrine when vasopressor therapy is required during peritoneal dialysis. The augmented transport with dopamine appears to depend on the action of dopamine receptors causing mesenteric vasodilation and in part on alpha-adrenergic receptors simultaneously increasing blood pressure while mesenteric blood flow is maintained.

Prediction of solute transport during peritoneal dialysis

Solute transport, predominantly diffusion, across the peritoneum correlates inversely with molecular weight. Provided that the solute is water soluble, not protein bound, not of unusual density, not ionized, does not have a large hydration shell, and is transported from plasma to dialysate, the peritoneal clearance is predictable over the molecular weight range from 60 to 11,000 daltons. Transport reates that deviate from the predicted can be explained by known physical properties of particular solutes.

Effects of gastrointestinal hormones on transport by peritoneal dialysis

Because the gastrointestinal hormones are known to dilate the splanchnic vasculature, their effects on transport of water and solutes during peritoneal dialysis were studied in an experimental model, the rabbit. In unanesthetized rabbits, dialysate volume was calculated by isotope dilution, and clearances were estimated by dialysate/plasma concentration ratio factored by minute volume. With isotonic dialysis solution, the mean increment in dialysate volume per minute of intraperitoneal dwell was 0.19 ml/kg/min, and mean clearances of creatinine and urea were 0.71 and 0.90 ml/kg/min, respectively. When administered intravenously, secretin significantly augmented osmotically induced water flux, but not when given intraperitoneally. Neither glucagon nor cholecystokinin affected dialysate volume. Intravenously, but not intraperitoneally, glucagon increased peritoneal clearances of creatinine and urea to more than 150% of control values. Neither cholecystokinin nor secretin augmented significantly peritoneal mass transport when given by either route. The data suggest that the site of acton is the endothelial surface of the membrane, that the mechanisms of augmenting transport involve increased permeability and/or surface area, and that agents which combine an increase in mass transport and capillary filtration coefficient may be clinically useful.

Divergent effects of catecholamines on peritoneal mass transport

In rabbits, intravenous vasopressor doses of dopamine augmented peritoneal clearances of creatinine and urea, suggesting increased mesenteric blood flow and possibly augmented permeability. Intraperitoneal dopamine also accelerated peritoneal transport of urea. Solute transport across the peritoneum was decreased by intravenous infusion of 1-norepinephrine. Intraperitoneal administration of the alpha-adrenergic antagonist phentolamine partially abolished the augmentation of peritoneal clearances induced by intravenous dopamine. The results suggest that in patients undergoing peritoneal dialysis who require vasopressor therapy, dopamine should be preferred to norepinephrine.

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.

Uremic autonomic neuropathy: evaluation of ephedrine sulphate therapy for hemodialysis-induced hypotension

The hemodynamic response to ephedrine sulphate were studied in a patient on maintenance hemodialysis therapy with chronic renal failure due to renal amyloidosis. The evaluation (including cardiac catheterization studies) and estimation of responses to Valsalva maneuvers before and after ephedrine administration documented the diagnosis of autonomic insufficiency. Oral ephedrine failed to influence the episodes of severe dialysis-induced hypotension. Also the patient did not benefit from the infusion of Aramine. These studies suggest that catecholamine stores of adrenergic nerves may be depleted in uremic patients with clinical signs of autonomic neuropathy.

Peritoneal clearances in scleroderma and diabetes mellitus: effects of intraperitioneal isoproterenol

Reduced peritoneal clearances of creatinine and urate were demonstrated repeatedly in a patient with scleroderma and a patient with diabetes mellitus. Urea clearances were not significantly different from usual values. The findings suggest decreased peritoneal membrane permeability and/or area (if urea clearance is flow limited). Clearances increased to usual values with intraperitioneal isoproterenol in the patient with diabetes. There was no effect of isoproterenol in the patient with scleroderma.

Effect of hemodialysis on factors influencing oxygen transport

Ten patients underwent 4 study hemodialyses, one with standard dialysis conditions, one with an isophosphate dialysate, one with simultaneous ammonium chloride loading, and other, after pretreatment, with sodium bicarbonate. Measurement of hemoglobin oxygen affinity (P-50), erythrocyte 2,3-DPG, blood-gasses, and serum chemistries revealed biochemically effective hemodialyses and slight changes in oxygen transport parameters. The P-50 (in vivo) values decreased slightly but significantly (p greater than 0.05) with dialysis. When corrected to pH 7.4, eliminating the Bohr effect, P-50 increased (p greater than 0.05). With unmodified dialysis elevated values of 2,3-DPG (in comparison to normal) decreased, a change that did not correlate with delta-p-50, delta-serum phosphate, or delta-serum creatinine. With standard and isophosphate dialyses Po-2 decreased significantly. The decrease correlated with delta-hydrogen ion concentration and did not occur with dialyses designed to maintain pH constant. Thus, hemodialysis influences many factors that affect oxygen transport in different and counterbalancing directions. These changes are not totally explained by alterations in 2,3-DPG, pH or serum phosphate. Maintenance of acidosis or hyperphosphatemia during dialysis is not recommended.

Influence of peritoneal dialysis on factors affecting oxygen transport

To determine the effect of changing concentrations of uremic metabolites on factors affecting oxygen transport, without the effects of extracorporeal blood pumping, we studied five patients before, during and after peritoneal dialysis. Significant decreases in serum urea, creatinine and phosphate and increase in serum bicarbonate were not associated with changes in P50, a reflection of hemoglobin-oxygen affinity. High erythrocyte 2,3-DPG concentrations decreased only slightly. Arterial pO2 increased slightly as negative fluid balance was achieved. The slight changes in oxygen transport parameters with dialysis suggest an interplay of compensatory factors and do not warrant modifying dialysis to limit the correction on acidosis or hyperphosphatemia. Effects on hemoglobin and pO2 resulting from fluid loss can be the dominant influence of peritoneal dialysis on tissue oxygenation.