Initial results of a new access device for hemodialysis technical note

BACKGROUND

A new subcutaneous device (DIALOCKtrade mark) provides vascular access to patients who currently require hemodialysis (HD). The device consists of a port-like valve, implanted subcutaneously below the clavicle, which provides a linear flow passage to two catheters placed in the right atrium via the internal or external jugular vein. The valve is accessed percutaneously with needle-cannulas that functionally convert the device to twin catheters for connecting the patient to the HD lines.

METHODS

The device was implanted in 10 outpatients under local anesthesia. Patients used the device during dialysis 3 times/week, and data were collected on blood flow, pressures, adverse events and patient and nurse satisfaction.

RESULTS

The device was used for HD almost immediately (median 3 days after implantation) and functioned successfully for more than nine months (mean +/- SD 7.3 +/- 1.5) in all but one patient who died of unrelated causes after one month; there were >800 dialysis sessions total. Blood flows over 300 ml/min were consistently achieved (average 326 +/- 40) with venous and arterial pressures of 200 +/- 44 and -246 +/- 29 mm Hg, respectively. After 66 patient-months, condition of the needle puncture sites remained satisfactory. Five systemic infections occurred in four patients, producing 2.3 bacteremic episodes per 1000 patient-days. All resolved without the need for device removal. There were no infections at the puncture sites. Two patients required fibrin sheath stripping of their catheters, one whose heparin lock was not changed for 23 days (for reasons unrelated to the device). Patient and nurse acceptance was excellent.

CONCLUSION

The device represents a positive improvement in the area of HD access.

New access device for hemodialysis

A new subcutaneous device (Dialock; Biolink Corp., Middleboro, MA) provides vascular access to patients who currently require hemodialysis (HD). The device consists of a port-like valve, implanted subcutaneously below the clavicle, which provides a linear flow passage to two catheters placed in the right atrium via the jugular vein. The valve is accessed percutaneously with needle-cannulas that functionally convert the device to twin catheters for connecting the patient to the HD lines. Interdialytic patency is maintained using a standard heparin lock. The device has been implanted in 10 outpatients under local anesthesia, with almost immediate use for HD (median, 3 days) and has functioned successfully for more than 6 months (mean +/- SD, 4.0 +/- 1.7; > 400 dialysis sessions). Blood flows over 300 ml/min were consistently achieved (average, 320 +/- 50) with venous and arterial pressures of 197 +/- 42 mmHg and -241 +/- 31 mmHg, respectively. After 40 patient-months, condition of the needle puncture sites remains satisfactory. Four systemic infections have occurred in three patients; all have resolved without the need for device removal. There have been no infections at the puncture sites. One patient whose heparin lock was not changed for 23 days (for reasons unrelated to the device) required fibrin sheath stripping of his catheters. Patient and nurse acceptance has been excellent. The device may offer substantial improvement over conventional devices for HD access.

The use of heated citric acid for dialyzer reprocessing

Dialyzer reprocessing with heated water (100 to 105 degrees C) for 20 h can be used safely in lieu of chemical methods for disinfection. All infective agents including spores are destroyed and depyrogenation may occur. However, these temperatures may result in structural damage to the dialyzer, limiting reuse. Dialyzer reprocessing by using 1.5% citric acid heated to 95 degrees C for 20 h is an alternative method that produces equivalent microbiologic effects. Citric acid is well known as a disinfecting agent used for dialysis equipment. Because there is little structural damage to dialyzer components at 95 degrees C, reuse statistics are improved (mean reuse increased to 12.8). Both small and large molecule clearances and the sieving coefficient for protein are insignificantly altered by the process. Whereas the procedure is relatively simple, quality-assurance indicators are essential. The method has appeal because it avoids the use of chemical germicides. However, at present it has only been tested thoroughly in polysulfone dialyzers with heat-resistant polycarbonate casings and polyurethane resin. The clinical experience is favorable.

Intradialytic parenteral nutrition: a practical approach

Intradialytic parenteral nutrition (IDPN) therapy is becoming more prevalent in the malnourished patient undergoing maintenance hemodialysis. This is of particular concern to the nephrology nurse in that additional time is required to administer the solution, monitor the patient, and document the process. The IDPN monitoring flowsheet described in this article was developed to promote continuity of care from treatment to treatment, especially during initiation of IDPN, and to assist the nephrology nurse in administering and monitoring the therapy.

On the Extrusion in Superplastic Conditions

In this paper the range within which the slab method is accurate enough to calculate the extrusion pressure in superplastic condition has been determined. A realistic velocity field, supported by experimental evidence, has been adopted. A strain rate field has been evaluated and an appropriate constitutive equation has been introduced. The slab method and the upper bound approach, here developed, have then been used to study the superplastic extrusion through a conical die. A comparison of the two solutions thus obtained has been carried out. It has been found that in any case the curves obtained using the slab method run higher than those obtained using the upper-bound approach. The analysis developed may be used to determine the range within the slab method is accurate enough for engineering purposes.