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Biomedical subjects

S R Ash

Publications and source records attributed to S R Ash.

At least 55 records · Page 3Linked to original sources
PubMed1984

Assessment of biomaterials as components of a reciprocating dialyser during canine dialysis.

A recently reported device, the sorbent suspension reciprocating dialyser (SSRD), was investigated for use as a test system for biocompatibility of dialyser components. The device is easy to assemble and operate, and allows minimal blood contact with foreign material outside of dialyser components. Its constant pressure/variable flow rate operation allows quantification of degree of clotting of dialyser versus time. The effect of heparinization of the blood distribution gaskets (BDG) of the device on performance and dialyser lifetime was investigated. Heparin was bound to the surface of polyethylene gaskets by immersion in a solution of tridodecylmethylammonium chloride (TDMAC)--heparin complex for several hours. Gaskets were then assembled in an SSRD which was then used for experimental dialysis in dogs with AV shunts. Dialysers assembled using non-heparinized gaskets were used as controls. Blood coagulation tendency was quantified by the activated clotting time (ACT) and partial thromboplastin time (PTT), and these values correlated with the rate of clotting of the device. Heparinization of the gaskets resulted in the prevention of clotting in the dialyser until the final minutes of dialysis in all cases, in contrast to the constant decay of blood fill volume and evidence of clotting in the non-heparinized cases. However, dialyser lifetime was not significantly increased by gasket heparinization. At normal initial values of ACT (80-95 s) dialyser clotting occurred in 10-15 min. In tests with non-heparinized gaskets and systemically heparinized dogs, values obtained in the ACT test were observed to decrease during dialysis, indicating the disappearance of heparin from the blood. Both ACT and PTT tests show promise as predictors of dialyser lifetime.

Animals↗
PubMed1984

Doppler ultrasonic detection of particulate release during hemodialysis with cellulose hollow-fiber and sorbent suspension reciprocating dialyzers.

Doppler ultrasound is a noninvasive technique for monitoring moving objects such as flowing blood while ignoring stationary objects such as shunt tubing. A Doppler system was investigated to determine its sensitivity in detecting particulate release in blood during hemodialysis. Seven hemodialysis procedures with dogs and six trials with humans were done using a sorbent suspension reciprocating dialyzer ( SSRD ). Two additional trials were done with humans using a cellulose acetate hollow-fiber dialyzer (HFD). A large increase (approximately twofold) was found in the reflected Doppler signal in outflowing blood from the SSRD and HFD in both dogs and humans. Numerous additional studies to characterize the nature of the particulate matter showed platelet aggregates in the dogs and fibrinogen-fibrin degradation products in the humans to be present in the outflowing blood. In vitro studies suggested microscopic air bubbles (less than 25 micron in diameter) may have contributed to the particulate matter detected during hemodialysis by this sensitive monitoring system.

Animals↗
PubMed1984

Intravenous transcutaneous vascular access device.

The indwelling transcutaneous vascular access device is easily implantable with little more skill or time required than is typically used in placement of standard intravenous needles or catheters. With routine maintenance of the device site, the infection rate in our studies are negligible. Biocompatibilty, assessed by the lack of destruction of blood components and by the paucity of signs of initimal or systemic disease, was good. Over the period of 10 to 21 days, all but one unit maintained adequate flow rates. The device is stable. There was no blood leakage from the area around the limbs in the chronic flow studies or the hemodialysis studies. The one episode of malpositioning occurred after a sudden strong tug on the tubing. A second dacron retaining cuff will be placed on the distal limb. This will be sutured into place and should increase unit stability. There was little evidence of pain or irritation from the device. No thrombotic tendencies were noted at the access site or systemically. The dogs were on Ascriptin and also the model (canine) is not prone to thromboembolic events. Further improvements on the device will include using smoother, more compatible materials: carbon-coated steel, brushed titanium, or covering the steel with PTFE or ceramic rather than the silastic-dacron cuff. Other future changes include the improvement of the device-tubing connection to one in which no blood will be lost when the device is attached to the dialyzer.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Support of an anephric dog for 54 days with ambulatory peritoneal dialysis and a newly designed peritoneal catheter.

A bilaterally nephrectomized dog was successfully supported with peritoneal dialysis for 54 days, using a radically new design of access catheter and a human dialysis schedule designated as continuous ambulatory peritoneal dialysis. The dog remained active and alert with a stabilized blood urea nitrogen of 30 to 40 mg/dl and a serum creatinine concentration of 4 to 6.5 mg/dl. Problems encountered with the peritoneal dialysis included the propensity for developing peritonitis, anorexia, and a significant plasma protein loss in the dialysate fluid as result of leakage across the peritoneum. Protein loss coupled with anorexia produced a catabolic state, and the animal was euthanatized because of this, at postnephrectomy day 54. The development of a new catheter design alleviated the drainage problems of the straight tube Tenckhoff catheter. Its use coupled with the continuous ambulatory peritoneal dialysis schedule and detailed management techniques allowed using the anephric dog as a model of uremia. In addition, peritoneal dialysis could be a viable treatment for animals presenting with acute reversible anuric or oliguric renal failure where conservative medical management with fluids and diuretics has failed to give clinical improvement.

Animals↗
PubMed1983

The Computerized Notation System (CNS). A microcomputer system for rapid entry of notes by physicians and nurses.

A computerized notation system has been developed to produce a digital medical data base. Use of a separate physical record for every 1-4 patients allows several years of accumulated data to be easily accessible for patient "summaries" or admission "histories and physicals." To facilitate entry of data in the system, the physician is provided with a portable, complete computer system (HP-85, or Epson HX-20), a user-defined two-letter dictionary, and a program that produces all elements of the manual paper charting system. "Overview" and research data bases are developed from the digital medical data base records. In this paper, we report the efficiency of use of this computerized notation system in private outpatient and inpatient practice.

Computers↗
PubMed1982

A reciprocating, single-needle hemodialyzer with bidirectional flow of sorbent suspension.

Previous theoretical analysis has indicated that adequate mass transfer is possible in a dialyzer with reciprocating membrane motion provided that the dialysate concentration of uremic substances is kept low. Earlier models have utilized a collection of sorbents (charcoal, urease, and a cation exchanger) constrained next to the dialyzer membranes. We have designed a new dialyzer with a sorbent suspension having free access from a reservoir to the spaces between membrane packages. At a treatment rate of 150 ml/min/m2, the in vitro creatinine clearance is 75 ml/min/m2, which agrees within experimental accuracy with the theoretical prediction. The creatinine clearance, flow resistance, and compliance of the dialyzer are constant during four to six hours of testing. In vivo tests have been performed during urea and creatinine infusion in a normal dog and in a dog with 3/4 nephrectomy. The in vivo creatinine clearance agrees within 10% with the in vitro clearance. Sodium, potassium, calcium, and bicarbonate fluxes are acceptable for patients in renal failure. The new design allows a higher capacity for urea and creatinine, since larger amounts of sorbent may be used.

Absorption↗
PubMed1982

Dialytic support of dogs with clinically occurring renal failure: a realistic model of acute renal failure in man.

In canine veterinary medicine, both acute and chronic renal failure occur relatively frequently, from a variety of causes similar to those in man. However, the normal dog has a very high protein catabolic rate and high endogenous kidney function, and, therefore, requires frequent and highly efficient dialysis, for maintenance during renal failure. We have developed techniques to support the uremic dog with hemodialysis. An experimentally anephric dog, and two dogs with clinically occurring acute renal failure (caused by ethylene glycol intoxication and heat stroke) have been supported with frequent use of hollow fiber dialyzers, using a carotid artery to jugular vein shunt. Patency of shunts was maintained by administration of oral aspirin. A very high urea and creatinine generation rate necessitated daily dialysis during much of the clinical course of renal failure. The experimentally anuric animal was supported for 35 days. The ethylene glycol-induced renal failure animal was euthanized on the 21st day, and the heat stress-induced renal failure animal recovered sufficient intrinsic renal function after 16 days of dialysis for maintenance of life without dialysis.

Acute Kidney Injury↗
PubMed1982

Case study of a diabetic dog with chronic membranous glomerulopathy treated with continuous intraperitoneal insulin infusion.

The purpose of this study was to determine the use of continuous intraperitoneal insulin infusion over an extended period (in maintaining metabolic control) and to evaluate the benefits of this treatment in reversing the kidney pathology of a chronic diabetic dog with membranous glomerulopathy. Hyperglycemia was eliminated, but reevaluations of the insulin infusion pattern were necessary. An initial kidney biopsy revealed fusion of the foot processes, thickening of the basement membrane, and subendothelial deposition. After 5 months of infusion, there was less fusion of the foot processes and a decrease in the subendothelial deposition. Urinary protein loss decreased from 17.3 g/day to 625 mg/day after 2 months of infusion. The dog gained weight, muscle wasting was reversed, and his stamina returned while on continuous insulin infusion. The reduction of a life-threatening urinary protein loss to a tolerable level and the improvement in the microscopic kidney lesions observed indicate that this treatment with insulin infusion may be beneficial in the management of long-term diabetic dogs, affected with advanced kidney lesions secondary to diabetes.

Alloxan↗