Vascular access: past, present, and future.

Vascular access is the Achilles' heel of hemodialysis. Current vascular access approaches for hemodialysis include arteriovenous (AV) fistula, AV graft, and central venous catheter. Strengths and weaknesses of each access type are described. New technology and procedures in introducing an access, monitoring access function, and salvaging a non-functioning access are also described.

High-intensity hemodialysis: the wave of the future?

Various modalities of high-intensity hemodialysis are gathering increasing popularity. Some of the advantages of these new dialysis regimens are presented. Time and the increasing use of these novel approaches will ultimately determine their role in the overall management of patients with endstage renal disease.

Serum potassium and acid-base parameters in severe dialysis-associated hyperglycemia treated with insulin therapy.

We analyzed the changes in serum potassium concentration ([K]) and acid-base parameters in 43 episodes of dialysis-associated hyperglycemia (serum glucose level > 33.3 mmol/L), 22 of which were characterized as diabetic ketoacidosis (DKA) and the remaining 21 as nonketotic hyperglycemia (NKH). All episodes were treated with insulin therapy only. Age, gender, initial and final serum values of glucose, sodium, chloride, tonicity and osmolality did not differ between DKA and NKH. At presentation, serum values of [K] (DKA 6.2 +/- 1.3 mmol/L; NKH 5.2 +/- 1.5 mmol/L) and anion gap [AG] (DKA 27.2 +/- 6.4 mEq/L; NKH 15.4 +/- 3.5 mEq/L) were higher in DKA, whereas serum total carbon dioxide content [TCO2 ] (DKA 12.0 +/- 4.6 mmol/L; NKH 22.5 +/- 3.1 mmol/L), arterial blood pH (DKA 7.15 +/- 0.09; NKH 7.43 +/- 0.07) and arterial blood PaCO2 (DKA 26.2 +/- 12.3 mm Hg; NKH 34.5 +/- 6.7 mm Hg) were higher in NKH. At the end of insulin treatment, serum values of [K] (DKA 4.0 +/- 0.7 mmol/L, NKH 4.0 +/- 0.5 mmol/L), [AG] (DKA 16.3 +/- 5.4 mEq/L, NKH 14.9 +/- 3.0 mEq/L), [TCO2 ] (DKA 23.5 +/- 5.0 mmol/L, NKH 24.1 +/- 4.2 mmol/L), arterial blood pH (DKA 7.42 +/- 0.09, NKH 7.51 +/- 0.14) and arterial blood PaCO2 (DKA 31.8 +/- 6.7 mm Hg, NKH 34.2 +/- 8.3 mm Hg) did not differ between the two groups. Linear regression of the decrease in serum [K] value during treatment, (Delta[K]), on the presenting serum [K] concentration,([K]2 ), was: DKA, Delta[K] = 2.78 - 0.81 x [K]2 , r = -0.85, p < 0.001; NKH, Delta[K] = 2.44 - 0.71 x [K]2 , r = -0.90, p < 0.001. The slopes of the regressions were not significantly different. Stepwise logistic regression including both DKA and NKH cases identified the presenting serum [K] level and the change in serum [TCO2 ] value during treatment as the predictors of Delta[K] (R2 = 0.81). Hyperkalemia is a feature of severe hyperglycemia (DKA or NKH) occurring in patients on dialysis. Insulin administration brings about correction of DKA and return of serum [K] concentration to the normal range in the majority of the hyperglycemic episodes without the need for other measures. The initial serum [K] value and the change in serum [TCO2 ] level during treatment influence the decrease in serum [K] value during treatment of dialysis-associated hyperglycemia with insulin.

Phosphorus-enriched hemodialysis for the treatment of patients with severe methanol intoxication.

Severe methanol poisoning requires treatment with prolonged and intensive hemodialytic therapy. Such treatment can engender either the de novo development of hypophosphatemia or the worsening of pre-existing hypophosphatemia. Phosphorus-enriched hemodialysis therapy can prevent the occurrence of this complication. We report three patients with severe methanol poisoning who were treated with phosphorus-enriched hemodialysis. Prevention or treatment of hypophosphatemia was successfully achieved with this dialytic technique.

Serum tonicity, extracellular volume and clinical manifestations in symptomatic dialysis-associated hyperglycemia treated only with insulin.

The absence of osmotic diuresis modifies the effects of hyperglycemia on body fluids in patients with advanced renal failure. To determine the relationship between clinical manifestations and abnormalities in tonicity and extracellular volume in such patients, we analyzed 43 episodes of severe dialysis-associated hyperglycemia (serum glucose exceeding 600 mg/dL) treated only with insulin. The main manifestations were dyspnea in 22 cases (pulmonary edema in 19), nausea and vomiting in 15, coma in 13 and seizures in 3, while 5 patients had no symptoms. Treatment with insulin resulted in a decrease in serum glucose value from 913 +/- 197 mg/dL to 170 +/- 78 mg/dL, an increase in serum sodium level from 125 +/- 5 to 136 +/- 5 mmol/L, and a fall in calculated serum tonicity value from 300 +/- 13 to 282 +/- 11 mmol/kg (all at p < 0.001). The ratio of the change in serum sodium level over change in serum glucose concentration was -1.50 +/- 0.22 mmol/L per 100 mg/dL. The percent increase in extracellular volume secondary to hyperglycemia developing from the prior euglycemic state and calculated from changes in serum sodium and chloride concentrations, was 10.9% +/- 4.6% (1.5% +/- 0.6% per 100 mg/dL increase in serum glucose level). All clinical manifestations dissipated after correction of hyperglycemia in 42 patients. One woman developed during treatment a fatal myocardial infarction. Dialysis patients with severe hyperglycemia may develop symptoms as a result of hypertonicity and extracellular expansion. Insulin alone may be sufficient treatment for these symptoms. The changes in serum tonicity and electrolytes during treatment are consistent with theoretical predictions.

Transjugular renal biopsy in patients with liver disease.

Although transjugular renal biopsy has been used extensively in Europe, experience with its use in the United States has been limited. We report 25 patients who underwent both transjugular liver and renal biopsies in the same sitting and 4 patients who underwent only a transjugular renal biopsy. All 29 patients had both liver disease and renal abnormalities. Each patient was also believed to have a relative or absolute contraindication to a percutaneous renal biopsy (usually in the form of a bleeding abnormality). Transjugular renal biopsy yielded a quantity of tissue sufficient for diagnosis in all but 1 patient. The mean number of glomeruli obtained per biopsy was 19.4 +/- 12.2 (SD). Pathological diagnoses found were tubular injury in 5 patients, membranoproliferative glomerulonephritis in 5 patients, nephrosclerosis in 3 patients, diabetic nephropathy in 2 patients, immunoglobulin A (IgA) nephropathy in 2 patients, minimal change disease in 2 patients, end-stage renal disease in 2 patients, nonspecific changes in 1 patient, early glomerulosclerosis in 1 patient, tubular atrophy only in 1 patient, and normal renal histological characteristics in 4 patients. One patient with suspected IgA nephropathy had no histological diagnosis established because of a lack of glomeruli in the biopsy specimen. There were no instances of major bleeding from the perirenal area; however, a small perirenal hematoma was identified in 3 patients by postbiopsy computed tomography or sonography. Thus, based on our experience, transjugular renal biopsy appears to be a safe and effective procedure for establishing a histological diagnosis and is an attractive alternative biopsy method for patients with advanced liver disease and contraindications to conventional percutaneous renal biopsy.

Metabolic alkalosis in a hemodialysis patient after ingestion of a large amount of an antacid medication.

A maintenance hemodialysis patient developed metabolic alkalosis in the absence of vomiting or nasogastric suction. The cause of the metabolic alkalosis was ingestion of an exogenous alkali in the form of Bromoseltzer. The metabolic alkalosis improved with hemodialysis using a low-bicarbonate bath.

Adjunctive antibiotic/anticoagulant lock therapy in the treatment of bacteremia associated with the use of a subcutaneously implanted hemodialysis access device.

To improve vascular access for hemodialysis, a new device (Dialock Hemodialysis Access System, Biolink Corporation, Middleboro, MA) has been developed. Implanted subcutaneously, the device is accessed by percutaneous puncture. Attached to the device are two catheters that are implanted into the superior vena cava or right atrium. Clinical results thus far have been promising. However, use of this device is not free from infectious complications. In the present pilot study, 25 maintenance hemodialysis patients were implanted with 26 Dialock devices. The incidence of bacteremia was 2.9/1,000 catheter days. In 14 episodes of bacteremia in 8 patients the infection was successfully treated with a combination of systemic antibiotic treatment and adjunctive antibiotic/anticoagulant lock therapy. The lock therapy entailed the instillation of both an antibiotic and an anticoagulant into the device. We believe that the antibiotic/anticoagulant lock technique is an effective, adjunctive therapeutic modality in the treatment of infections related to the use of indwelling vascular access devices.

Management of hypophosphatemia induced by high-flux hemodiafiltration for the treatment of vancomycin toxicity: intravenous phosphorus therapy versus use of a phosphorus-enriched dialysate.

Intensive high-flux hemodiafiltration is often used in the management of vancomycin toxicity. We describe two patients who developed hypophosphatemia as a consequence of this form of therapy. The first patient was treated with an intravenous phosphorus infusion. For the second patient, hypophosphatemia was corrected, during hemodiafiltration, with the use of a phosphorus-enriched dialysate. The latter dialysate was prepared by adding sodium phosphate salts to the "base concentrate" of a dual-concentrate, bicarbonate-based dialysate delivery system. This simple method was more efficient than intravenous therapy in ameliorating the hypophosphatemia secondary to aggressive hemodiafiltration treatment.

Stability of urea and creatinine in spent hemodialysate.

Urea and creatinine levels in spent hemodialysates showed only small declines in spite of incubation at 37 degrees C for 36 hours. In the determination of dialysate-side solute removal, it would seem prudent to keep spent dialysate cold during collection to retard bacterial breakdown of these waste products.

Removal of Foscarnet by hemodialysis using dialysate-side values.

Foscarnet is an antiviral agent widely used in the treatment of cytomegalovirus (CMV) infection. We describe a cardiac transplant patient, who while being maintained with hemodialysis because of tobramycin-induced acute renal failure, was given Foscarnet for disseminated CMV infection. Using dialysate-side clearance methodology, we found the dialyzer clearance of Foscarnet to be in the order of 89 ml/min.

Saline-induced dilutional acidosis in a maintenance hemodialysis patient.

A patient with end-stage renal disease developed severe hyperchloremic acidosis (venous serum total CO2 level of 10 mmol/L) after treatment with 16 L of isotonic saline. Analysis of this case and published literature indicates that dilutional acidosis may result when very large volumes of isotonic saline are administered intravenously, especially in patients with impaired or absent renal function.

Laboratory monitoring of pentasaccharide in a dog model of hemodialysis.

Varying dosages of pentasaccharide (400-800 nmol/kg) were compared to a 250-U/kg single bolus dosage of unfractionated heparin (UFH) in a dog model of hemodialysis. Several laboratory assays were used to monitor the effects of pentasaccharide and UFH. The pentasaccharide did not produce any anticoagulant effects as measured by the activated partial thromboplastin time. However, in the anti-Xa chromogenic assay and the Heptest assays, there was a dose-dependent prolongation after pentasaccharide administration. In the group of dogs administered 800 nmol/kg of pentasaccharide, there was a 50% decrease in the thrombin antithrombin (TAT) complex level after 60 minutes on dialysis. In the UFH-treated dogs, wide variations in assays were observed. There was a marked elevation in the activated partial thromboplastin time and Heptest assays up to 6 hours after UFH administration. Both anti-Xa and anti-IIa activity was measured up to 4 hours. In the TAT assay, UFH was found to have a stronger effect in suppressing the formation of TAT in comparison to the pentasaccharide. These results suggest that pentasaccharide can be used as a replacement for UFH in a dog model of hemodialysis to keep the dialysis circuit patent. In addition, the anti-Xa-based assays such as the Heptest and the chromogenic anti-Xa assays can be used to monitor the effects of pentasaccharide in this model.

Hemodialysis as a treatment of severe ethanol poisoning.

A 64-year-old woman presented with coma and shock due to severe ethanol intoxication. Her initial, markedly elevated blood alcohol level of 136.5 mM fell only by 16% after a 4-hour period of conservative treatment consisting of mechanical respiration and the administration of intravenous fluids, vasopressors and inotropics. Subsequent hemodialysis rapidly reduced her blood ethanol concentrations to less threatening levels, with prompt restoration of her consciousness. Hemodialysis may be life-saving and should be considered in patients with severe ethanol intoxication.