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Biomedical subjects

Stephen R Ash

Publications and source records attributed to Stephen R Ash.

18 recordsLinked to original sources
PubMed2006

Sorbent suspensions vs. sorbent columns for extracorporeal detoxification in hepatic failure.

Hepatic failure is a significant medical problem which has been unsuccessfully treated by hemodialysis. However, similar therapies using recirculated dialysate regenerated by sorbents in place of single-pass dialysate have been beneficial in treating acute-on-chronic liver failure. The advantages of sorbent-based treatments include some selectivity of toxin removal and improved removal of protein-bound toxins. Activated carbon has been extensively used in detoxification systems, but has often had insufficient toxin capacity. Powdered activated carbon, because of its large surface area, can provide greater binding capacity for bilirubin and other toxins than granular carbon commonly used in detoxifying columns. Methods of using powdered carbon in extracorporeal blood treatment devices are reviewed in the present paper, including liver dialysis and a new sorbent suspension reactor (SSR); and the abilities and limitations of the SSR and columns to process protein solutions are discussed.

Carbon↗
PubMed2006

Catheter related bacteremia in rats: A preliminary report on the effect of methylene blue coated catheter.

The safety and efficacy of methylene blue (MB) coated indwelling jugular vein/cranial vena cava catheter made up of polyurethane material was tested in a rat model, receiving bacterial culture suspension of Pseudomonas aeruginosa, and Staphylococcus aureus. Daily blood samples were collected from the catheter and peripheral vein for bacterial culture. The clinical parameters (rectal temperature, respiratory rate, total white blood cell count, and loss in body weight) were not different between the groups. All the rats became bacteremic with similar changes in the number of colony forming units in the catheter and peripheral samples. Histopathological lesions were not different between the groups. The findings suggest that rats receiving MB coated catheters behaved similar to non-coated catheters. Based on the results it can be concluded that for this type of gross contamination, catheter coating alone may not eliminate infection/bacteremia.

Animals↗
PubMed2005

Use of continuous-flow peritoneal dialysis for the treatment of acute renal failure in an adult horse.

A 15-year-old Paso Fino gelding was evaluated because of acute renal failure following an episode of exertional rhabdomyolysis. The horse was azotemic and treated conservatively at another referral practice with no improvement in the azotemia. With conservative treatment and intermittent peritoneal dialysis, the horse had minimal improvement. Continuous-flow peritoneal dialysis (CFPD) was instituted on day 7 and continued for 3 consecutive days. Dramatic changes in the horse's attitude and serum creatinine concentration were detected within the first 24 hours of CFPD treatment. The horse remained hospitalized for 23 days; within 3 months of discharge, serum BUN and creatinine concentrations had returned to within the reference ranges and the horse had resumed normal activity. In adult horses, it appears that CFPD can be used to successfully treat acute renal failure that is refractory to conventional treatments.

Acute Kidney Injury↗
PubMed2003

Utilization of in vivo ultrafiltration in biomedical research and clinical applications.

Ultrafiltration (UF) is a filtrate selection method with a wide range of biomedical and clinical applications, including detoxification of blood in hemodialysis and peritoneal dialysis. New is, however, the use of UF as a convenient in vivo sampling method that, for example, has been used in diabetics. Ultrafiltration avoids complicated and time-consuming recovery calculations that are necessary when using in vivo microdialysis, as recoveries of low molecular weight molecules are near 100%. The subcutaneously or intravenously placed UF probes have been studied for off-line sample analysis and for continuous on-line monitoring, in a wide variety of species, including dogs, rats, pigs and humans. This review discusses the potential of in vivo UF as a continuous tissue sampling technique in clinical research areas, and in several major biomedical applications including glucose and lactate monitoring and drug kinetic studies.

Animals↗
PubMed2002

Treatment of severe tricyclic antidepressant overdose with extracorporeal sorbent detoxification.

Tricyclic overdose can be a medical emergency, and therapy with intravenous bicarbonate is not always successful in preventing cardiac toxicity or coma. Mortality in patients developing these complications is from 1% to 15%. Extracorporeal detoxification with sorbents has been used in treatment of patients with very high drug levels and declining clinical condition. Ten patients with serious drug overdose caused by tricyclics failed to respond quickly to standard therapy and were in stage 3-4 encephalopathy. Nine of these patients were on respirator support, 5 had hypotension, and 6 had QRS widening. Average level was 1,423 microg/L at presentation. Enteral activated charcoal and intravenous (IV) bicarbonate were initiated in the emergency room. The patients were treated for 3 to 4 hours with the Liver Dialysis Unit, a hemodiabsorption device using a cellulosic plate dialyzer and sorbent suspension as dialysate. Inflow and outflow blood levels indicated that the hemodetoxifier removed modest amounts of the tricyclics, metabolites, and other consumed drugs. The clinical improvement of the patients was dramatic, with patients reaching stage 0 or 1 encephalopathy during the treatment. Ventilator support was removed at the end of treatment for 3 patients who had not already developed pneumonia, and for others was prolonged up to 48 hours because of pneumonia, rather than mental status. Average length of stay in the intensive care unit (ICU) was 4.8 days (range 1 to 7 days). None of the patients died despite their high risk for ventricular arrhythmias, seizures, and death. Clinical improvement may have been attributable to removal of free drug from the blood or to removal of drug metabolites.

Antidepressive Agents, Tricyclic↗
PubMed2002

Treatment of acetaminophen-induced hepatitis and fulminant hepatic failure with extracorporeal sorbent-based devices.

When a patient with acetaminophen overdose arrives in the emergency room more than 14 hours after ingestion, the value of N-acetylcysteine is unproven and patient mortality is at least 10%. Anecdotal case reports have indicated benefit of extracorporeal detoxification of these late-arriving patients with acetaminophen overdose. We identified 10 patients with serious acetaminophen overdose, 8 that arrived in the emergency room 16 to 44 hours after acetaminophen overdose with plasma levels predicting severe hepatic toxicity, and 2 that arrived in the emergency room 8 to 12 hours after overdose but with exceedingly high levels. All patients developed severe hepatitis (mean peak alanine aminotransferase, 4,052; mean peak protime, 25 seconds). At 16 to 68 hours after overdose, the patients were treated for 4 to 6 hours with the Liver Dialysis System (Hemocleanse Inc, W. Lafayette, IN), a single-access hemodiabsorption system indicated for treatment of serious drug overdose and for treatment of hepatic encephalopathy. Acetaminophen levels fell an average of 73% during treatment. Treatment was repeated 24 or 48 hours later if acetaminophen was still measurable in plasma. All 10 patients recovered intrinsic liver function and general health, with liver enzymes starting to normalize 24 hours after treatment, and were discharged 3 to 7 days after overdose. No patient required liver transplant. Because market introduction of Liver Dialysis, there have been 40 more patients with acetaminophen-induced hepatotoxicity treated with Liver Dialysis. All have recovered liver function without long-term sequelae. Though most of these patients with already established hepatic toxicity from acetaminophen would recover without extracorporeal blood therapy, treatment with the Liver Dialysis System should assure recovery from acute hepatic failure, and may shorten the clinical course of the illness.

Acetaminophen↗
PubMed2002

Extracorporeal blood detoxification by sorbents in treatment of hepatic encephalopathy.

Extracorporeal blood detoxification by sorbent therapy long has been applied in treatment of hepatic failure and encephalopathy, starting with hemoperfusion columns and more recently with the currently marketed Liver Dialysis Unit. Liver Dialysis employs hemodiabsorption (dialysis of blood against powdered sorbents including charcoal and cation exchanger) to remove selectively numerous small-molecular-weight toxins of hepatic failure. Liver Dialysis is used in treatment of acute hepatic encephalopathy (AHE) because of decompensation of chronic liver disease (A-on-C) or fulminant hepatic failure (FHF). Controlled, prospective and randomized studies of daily 6-hour Liver Dialysis have shown physiologic and neurologic improvement of patients with AHE, regardless of etiology. Liver dialysis significantly improved the incidence of positive outcomes (recovery of hepatic function or improvement for transplant) of A-on-C patients versus controls (71.5% treated, and 35.7% control, P =.036), but had an insignificant improvement in outcome of patients with FHF as compared with the control group. Other extracorporeal sorbent devices are now in clinical testing phase. The molecular adsorbent regenerating system (MARS) device employs a polysulfone high-permeability dialyzer with albumin on the dialysate side to aid transfer of protein-bound toxins such as bilirubin and bile acids across the membranes. Sorbent columns of charcoal and an anion exchanger remove hepatic toxins from the albumin dialysate, and a second dialyzer removes water-soluble toxins, such as ammonium. Clinical results of daily MARS treatments of patients with hepatic failure are similar to that of Liver Dialysis, with neurologic and physical improvement occurs in most patients with AHE, and improved outcome for patients with A-on-C. The system extends the life of patients with hepatorenal syndrome. PF-Liver Dialysis is an experimental device combining hemodiabsorption with push-pull sorbent-based pheresis with powdered sorbent surrounding plasmafilters. PF-Liver Dialysis (Hemocleanse, Inc, W. Lafayette, IN) has been tested in a few patients with hepatic failure, grade 3-4 encephalopathy, and respiratory and kidney insufficiency. Treatments appeared to be safe and resulted in marked decreases in plasma levels of bilirubin, aromatic amino acids, ammonium, creatinine, and interleukin-1beta (IL-1beta). The PF add-on module adds the capability to Liver Dialysis to remove bilirubin, bile acids, and other strongly protein-bound toxins from treated patients and may be of clinical benefit in management of patients with the most severe hepatic failure and encephalopathy, including patients with FHF or concomitant sepsis.

Hemodiafiltration↗
PubMed2002

Clinical trials of the T-fluted (Ash Advantage) peritoneal dialysis catheter.

The Ash Advantage is a T-shaped peritoneal catheter with a single transabdominal tube joining to a tube lying against the parietal peritoneum. Segments with long flutes (grooves) serve as fluid ports rather than 1-mm diameter holes. The folded catheter is placed through the expandable Y-TEC Quill positioned peritoneoscopically, similar to the procedure for a conventional Tenckhoff catheter. In a clinical study, we placed 18 Ash Advantage ("Advantage") catheters, 8 in patients with prior hydraulic or infectious complications of Tenckhoff catheters and 10 in patients initiating peritoneal dialysis. Mean follow-up has been 8.4 months. Outflow rate for the Advantage catheters is uniformly higher than for Tenckhoff catheters at 220 +/- 100 mL/min for the first 5 minutes and 145 +/- 72 mL/min for the next 5 minutes, with outflow completed in 6 to 15 minutes. Variation of outflow volumes for similar exchanges in the same patient is +/- 3% to 5%, much less than with Tenckhoff catheters. Four catheters failed after placement, each for a different reason including outflow failure because of preexisting intraperitoneal adhesions, preexisting peritonitis failing to clear, tubing kink during placement, and catheter break after a freak accident. Life-table analysis of the production version of the catheter in study patients and 12 additional unselected patients indicates a 90% survival at 12 months. In long-term use, the fixed position of the cuffs of this catheter may avoid catheter extrusion, pericatheter hernias, and pericatheter leaks. Multiple fluted ports appear to diminish omental attachment. The catheter may be a useful alternative to conventional Tenckhoff catheters in patients at high risk of catheter failure or in standard peritoneal dialysis patients.

Catheters, Indwelling↗
PubMed2002

Chronic peritoneal dialysis catheters: procedures for placement, maintenance, and removal.

Peritoneal dialysis (PD) is an integral part of the practice of most nephrologists, and a life-sustaining therapy for many of our patients. As in hemodialysis, the success of PD is often determined by the success of the access device. For the nephrologist placing and removing PD catheters, or for the nephrologist advising surgeons in this role, this article provides a review of the types of PD catheters and differences in function and complications, methods of insertion of PD catheters and relation to catheter outcomes, techniques for burying the external portion of the PD catheter and benefits of this technique, and techniques for removing PD catheters.

Catheterization↗
PubMedDate not supplied

Chronic peritoneal dialysis catheters: overview of design, placement, and removal procedures.

The success of chronic peritoneal dialysis (PD) depends to a large extent on the success of the chronic PD access device. For the nephrologist placing and removing PD catheters, or for the nephrologist advising surgeons in this role, this article provides a review of designs of PD catheters and differences in function and complications, methods of insertion of PD catheters and relation to catheter outcomes, techniques for "burying" the external portion of the PD catheter and benefits of this technique, and techniques for removing PD catheters. As nephrologists become more closely involved in the creation, monitoring, and maintenance of access devices for end-stage renal disease (ESRD) patients, the successful function of these devices will increase. Nephrologists should make the critical decisions regarding the choice of access devices and methods for placement as they do for the choice to remove such access devices.

Catheters, Indwelling↗
PubMedDate not supplied

Predicting dialysate sodium composition in sorbent dialysis using single point and multiple-dilution conductivity measurement.

This research establishes the ability to predict the sodium composition in dialysate from a single conductivity measurement over the wide range of concentrations of chloride, bicarbonate, and acetate that occur during sorbent dialysis. The ranges explored in mEq/L were sodium 100-180, chloride 76-143, bicarbonate 16-31, and acetate 4-11. Through mathematical optimization using a pattern search method, a single point measurement technique was shown to predict the total sodium concentration within approximately +/- 4.2 mEq/L in solutions with varying relative concentrations of chloride, bicarbonate, and acetate. The data analysis showed that the total sodium concentration can be predicted within +/- 2.1 mEq/L in most cases. Another potential approach to determining sodium concentration, a multiple-dilution measurement method, was tested and is also described. It is based on the varying relationship of activity to concentration for each of the sodium-anion pairs. This technique has practical limitations because of interactions between the various ions in solution at normal concentrations of dialysis along with the complexities involved in creating high dilutions of dialysate for on-line assays during dialysis.

Biometry↗
PubMedDate not supplied

The Allient dialysis system.

The Allient is a dialysis system that combines various technologies to allow dialysis to be performed at sites outside of dialysis units (intensive care unit [ICU] or home) with ease and safety. A sorbent column regenerates dialysate, removing toxins and providing ultrapure dialysate from only 6 liters of tap water. The use of the sorbent column eliminates the need for costly and complex water purification systems. The Pulsar Blood Movement System provides blood flow at constant negative or positive pressure through single-lumen or dual-lumen accesses, maximizing blood flow rate while eliminating bothersome pressure alarms. Ultrasonic flow monitors control the operation of the pump and ensure adequate blood flow during each dialysis treatment. A completely disposable blood tubing and dialysate circuit eliminates the need for sterilization of the machine. The Allient should make dialysis in the ICU or home setting much more practical, reducing training requirements and increasing safety.

Equipment Design↗