Papers by ROBERT HOOTKINS
Treatment of hyperphosphatemia in hemodialysis patients: The Calcium Acetate Renagel Evaluation (... more Treatment of hyperphosphatemia in hemodialysis patients: The Calcium Acetate Renagel Evaluation (CARE Study). Background. Hyperphosphatemia underlies development of hyperparathyroidism, osteodystrophy, extraosseous calcification, and is associated with increased mortality in hemodialysis patients. Methods. To determine whether calcium acetate or sevelamer hydrochloride best achieves recently recommended treatment goals of phosphorus ≤5.5 mg/dL and Ca × P product ≤55 mg 2 /dL 2 , we conducted an 8-week randomized, double-blind study in 100 hemodialysis patients. Results. Comparisons of time-averaged concentrations (weeks 1 to 8) demonstrated that calcium acetate recipients had lower serum phosphorus (1.08 mg/dL difference, P = 0.0006), higher serum calcium (0.63 mg/dL difference, P < 0.0001), and lower Ca × P (6.1 mg 2 /dL 2 difference, P = 0.022) than sevelamer recipients. At each week, calcium acetate recipients were 20% to 24% more likely to attain goal phosphorus [odds ratio (OR) 2.37, 95% CI 1.28-4.37, P = 0.0058], and 15% to 20% more likely to attain goal Ca × P (OR 2.16, 95% CI 1.20-3.86, P = 0.0097). Transient hypercalcemia occurred in 8 of 48 (16.7%) calcium acetate recipients, all of whom received concomitant intravenous vitamin D. By regression analysis hypercalcemia was more likely with calcium acetate (OR 6.1, 95% CI 2.8-13.3, P < 0.0001). Week 8 intact PTH levels were not significantly different. Serum bicarbonate levels were significantly lower with sevelamer hydrochloride treatment (P < 0.0001). Conclusion. Calcium acetate controls serum phosphorus and calcium-phosphate product more effectively than sevelamer hydrochloride. Cost-benefit analysis indicates that in the absence of hypercalcemia, calcium acetate should remain the treatment of choice for hyperphosphatemia in hemodialysis patients. Hyperphosphatemia is associated with increased mortality in hemodialysis patients and plays a key role in the
PubMed, Jul 1, 1991
It is known that convective transport (ultrafiltration, QF) augments diffusive transport. This au... more It is known that convective transport (ultrafiltration, QF) augments diffusive transport. This augmentation achieves great importance as solute molecular weight increases. Previous mathematical treatments of dialysance (D) have provided the relationship between D and blood flow rate (QB), dialysate flow rate (QD), and dialyzer membrane surface area permeability product (KoA), in the limit of QF = 0. The authors derived the relationship between D (defined as D') and QB, QD, and KoA for the general case of QF greater than or equal to 0: D' = X-Y/In X/Y . [(1-ó) QF + KoA] for X = X(D', QF, QD) = 1 - [D'/QD + QF] Y = Y(D', QF, QB) = D'-QB/QF-QB ó = the Staverman reflection coefficient. This equation demonstrates an approximate linear increase in D' as QF increases. Experimental verification is provided by in vivo studies of dialysis patients in which the dialysance of vancomycin doubles as QF is increased from 0 to 50. Because D' varies linearly with QF, this allows for the determination of KoA and ó. Using the Cobe 500HG Hemophan membrane, KoA for vancomycin was determined to be 6.54 and ó = 0.88.
Seminars in Dialysis, Oct 1, 2007
Dialysis & Transplantation, Sep 1, 2011
Seminars in Dialysis, Oct 1, 2007
Issues of optimal hemodialysis and dialysis adequacy have recently received considerable attentio... more Issues of optimal hemodialysis and dialysis adequacy have recently received considerable attention. One potentially important aspect of an “optimal” dialysis treatment is the dialysis treatment duration (Td). Td must be long enough to minimize the clinical effects of rapid ultrafiltration and to provide adequate solute clearance to prevent uremia. Although choice of dialyzer size, blood flow rate (QJ, and dialysate flow rate (Qd) affect solute clearance, the most influential prescription parameter that affects the “dose” of dialysis is Td. Recently, there have been increasing pressures to shorten Td. Reasons cited include cost effectiveness, patiendstaff convenience, and improved technology. The central assumption about shortening dialysis is that any reduction in Td can be equivalently offset by increasing the prescribed clearance. This “timeprescribed clearance equivalence” (i.e., T X K = constant) has not been validated and is likely erroneous as shown below. Prior to publication of the initial results of the National Cooperative Dialysis Study (NCDS) in 1981, and its more complete evaluation in 1983, the predominant basis for dialysis prescription was the “middle molecule” hypothesis, a derivative of the “square-meter-hour” hypothesis. The latter was based on early observations that increasing blood or dialysate flow didn’t seem to improve patient wellbeing. Improvements in therapeutic outcome were only achieved by increasing the dialyzer surface area or by increasing dialysis duration. This observation was consistent with previous fiFdings that urea and other small molecular weight solutes that accumulate in patients with renal failure have little demonstrated toxicity. Larger molecular weight substances, yet to be discovered, were considered to be the real toxins removed by the dialyzer. The clearance of these less diffusible compounds was considered “membrane limited”, that is, insensitive to blood and dialysate flow but proportional to the size of the dialyzer. Total clearance could be increased by a proportionate increase in dialysis time. The NCDS was designed to test the middle molecule hypothesis. Unknown at the time was the fact that acetate
Journal of The American Society of Nephrology, Dec 1, 1990
Hemodialysis and hemoperfusion have been evaluated, and both are effective in removing theophylli... more Hemodialysis and hemoperfusion have been evaluated, and both are effective in removing theophylline. We report two consecutive cases of theophylline intoxication in which the sequential treatment of charcoal hemoperfusion and hemodialysis is contrasted to the simultaneous 'in series" treatment of hemodialysis and charcoal hemoperfusion.
Biochimica Et Biophysica Acta - Bioenergetics, Apr 1, 1983
Photosynthetic membrane fragments separated from whole cells of the green alga Dunaliella papa, w... more Photosynthetic membrane fragments separated from whole cells of the green alga Dunaliella papa, were oriented by incorporation into multilayers on thin Mylar films. These partially dehydrated films were then examined by EPR spectroscopy for evidence of orientation of paramagnetic components. Five previously identified paramagnetic components, the reduced states of iron-sulfur clusters A and B, the intermediate acceptor X-, the reduced Rieske iron-sulfur cluster, and oxidized cytochrome b-559, displayed EPR signals showing orientation. In addition, several previously unknown paramagnetic components were also observed to be oriented. Four components, previously characterized in spinach chloroplast preparations, the iron-sulfur clusters A and B, the intermediate acceptor X-, and cytochrome b-559, were shown to be similar in the green alga, D. parva. The orientations of iron-sulfur clusters A and B, however, were determined unambiguously in this preparation; this was not possible in previous work with spinach. The heme plane orientation of cytochrome b-559 was found to be perpendicular to the membrane plane in agreement with the results in spinach preparations. A new photoinduced EPR signal with g values of 1.88, 1.97 and 2.12 was seen only in the oriented preparations and was indicative of a reduced iron-sulfur cluster with an orientation different from that of iron-sulfur cluster A or B. This suggests the existence of a previously unidentified acceptor in Photosystem I of green plants. These studies clearly show that the orientation of these components in bioenergetic membranes are conserved over a large span of evolutionary development and are, therefore, an important aspect of the mechanism of electron transfer.
Baylor University Medical Center Proceedings, 1990
Poisoning from most common intoxicants does not result in significant morbidity or mortality and ... more Poisoning from most common intoxicants does not result in significant morbidity or mortality and is best treated with supportive care. For particular ingestions, decontamination with the oral administration of activated charcoal or the enhancement of urinary excretion can be beneficial. For intoxications with selected drugs (Le.,those that have a low volume of distribution or a low affinity for tissue binding), or for patients with impaired normal excretory routes of drug elimination, hemodialysis and hemoperfusion are important adjunctive techniques for drug removal. Criteria are discussed concerning when to involve the nephrologist in implementing these procedures to treat intoxication from methanol, isopropanol, ethylene glycol, theophylline, lithium, and salicylates. Epidemiology of Poisoning A staggering number of poisoning episodes occur annually in the United States, with a great deal of time expended in their treatment and management. In 1987, according to the American Association of Poison Control Centers (AAPCC), more than one million cases ofpoisoning led to 397 deaths and 3,631 "major events" (1). The 63 centers that report to the AAPCC cover a population base of 137.5 million; extrapolation to the current estimated U.S. population of243.4 million suggests that the reported poisoning incidents represent only 57% of the total episodes during 1987. Of these reported poisonings, 89% were accidental, 9% were suicidal, and 1.6% were adverse reactions. Interestingly, 74.8% were managed in nonhealth care facilities (mostly at home).
Baylor University Medical Center Proceedings, Oct 17, 2019
This study examined the safety and efficacy of the intravenous administration of 20 mEq potassium... more This study examined the safety and efficacy of the intravenous administration of 20 mEq potassium chloride (KCl) dissolved in a 100 cc 5% dextrose in sterile water bolus over 1 hour through a subclavian central vein catheter in critical care unit patients for the treatment of low and low to normal serum potassium concentrations. We studied seven patients with morning serum potassium between 2.4 and 3.6 mEq/L who had intravenous KCl boluses ordered by their treating physician. Intracardiac and peripheral venous potassium levels were obtained before, during, and after infusion. Holter and electrocardiogram assessment of rhythm, supraventricular and ventricular ectopy, and electrical intervals were recorded before, during, and after the intravenous KCl bolus. The cardiac rhythm, heart rates, and electrocardiographic intervals remained unchanged throughout the infusion and postinfusion phases. In six of the seven patients, there was no new or worsening supraventricular or ventricular ectopy temporally related to the infusion. Postinfusion potassium levels increased in all patients, with an average peripheral vein serum potassium increase of 0.4 mEq/L. In conclusion, within the limitations of our sample size, our study demonstrated the safety and efficacy of the central venous infusion of 20 mEq KCl in 100 cc 5% dextrose in sterile water administered over 1 hour.
Seminars in Dialysis, Oct 1, 2007
Seminars in Dialysis, Oct 1, 2007
Increasing dialysate flow rate from 500 mL/min to 800 or 1000 mL/min has been recommended to incr... more Increasing dialysate flow rate from 500 mL/min to 800 or 1000 mL/min has been recommended to increase the eflciency of dialysis and allow shorter
Clinical Journal of The American Society of Nephrology, May 19, 2016
Hyperammonemia is an important cause of cerebral edema in both adults with liver failure and chil... more Hyperammonemia is an important cause of cerebral edema in both adults with liver failure and children with inborn errors of metabolism. There are few studies that have analyzed the role of extracorporeal dialysis in reducing blood ammonia levels in the adult population. Furthermore, there are no firm guidelines about when to implement RRT, because many of the conditions that are characterized by hyperammonemia are extremely rare. In this review of existing literature on RRT, we present the body's own mechanisms for clearing ammonia as well as the dialytic properties of ammonia. We review the available literature on the use of continuous venovenous hemofiltration, peritoneal dialysis, and hemodialysis in neonates and adults with conditions characterized by hyperammonemia and discuss some of the controversies that exist over selecting one modality over another.
Gastroenterology, Mar 1, 1995
Background~Aims: The treatment of hyperkalemia in patients with renal insufficiency often include... more Background~Aims: The treatment of hyperkalemia in patients with renal insufficiency often includes the ingestion of sorbitol and a cation exchange resin. Sorbitol alone may be used to remove sodium and water from overloaded patients. The efficacy of these regimens has never been compared with other laxative or laxative-resin combinations. The aim of the study was to compare the relative effect of three laxatives with different mechanisms of action, alone and in combination with resin, on fecal sodium and potassium excretion. Methods: Sodium, potassium, and water excretion in 12-hour stool collections were analyzed after various laxative-resin combinations in normal subjects. Results: Correctol (yellow phenolphthalein) (Schering Plough Health Care Products, Memphis, TN) was more effective than sorbitol or sodium sulfate in causing fecal sodium and potassium loss. Resin recovery in stool was much greater with phenolphthalein than with other laxatives, and more potassium was excreted in stool with phenolphthalein-resin than with phenolphthalein alone or other laxative-resin combinations. Sorbitol caused more undesirable gastrointestinal symptoms than did sodium sulfate or phenolphthalein. Conclusions: In normal people, phenolphthalein (1) is preferable to other laxatives in causing fecal sodium and potassium excretion, (2) hastens resin transit through the intestine compared with other laxatives, and (3) produces greater fecal potassium excretion when combined with resin than phenolphthalein alone or other laxative-resin combinations.
Seminars in Dialysis, Feb 1, 1999
Kidney International, May 1, 2004
Treatment of hyperphosphatemia in hemodialysis patients: The Calcium Acetate Renagel Evaluation (... more Treatment of hyperphosphatemia in hemodialysis patients: The Calcium Acetate Renagel Evaluation (CARE Study). Background. Hyperphosphatemia underlies development of hyperparathyroidism, osteodystrophy, extraosseous calcification, and is associated with increased mortality in hemodialysis patients. Methods. To determine whether calcium acetate or sevelamer hydrochloride best achieves recently recommended treatment goals of phosphorus ≤5.5 mg/dL and Ca × P product ≤55 mg 2 /dL 2 , we conducted an 8-week randomized, double-blind study in 100 hemodialysis patients. Results. Comparisons of time-averaged concentrations (weeks 1 to 8) demonstrated that calcium acetate recipients had lower serum phosphorus (1.08 mg/dL difference, P = 0.0006), higher serum calcium (0.63 mg/dL difference, P < 0.0001), and lower Ca × P (6.1 mg 2 /dL 2 difference, P = 0.022) than sevelamer recipients. At each week, calcium acetate recipients were 20% to 24% more likely to attain goal phosphorus [odds ratio (OR) 2.37, 95% CI 1.28-4.37, P = 0.0058], and 15% to 20% more likely to attain goal Ca × P (OR 2.16, 95% CI 1.20-3.86, P = 0.0097). Transient hypercalcemia occurred in 8 of 48 (16.7%) calcium acetate recipients, all of whom received concomitant intravenous vitamin D. By regression analysis hypercalcemia was more likely with calcium acetate (OR 6.1, 95% CI 2.8-13.3, P < 0.0001). Week 8 intact PTH levels were not significantly different. Serum bicarbonate levels were significantly lower with sevelamer hydrochloride treatment (P < 0.0001). Conclusion. Calcium acetate controls serum phosphorus and calcium-phosphate product more effectively than sevelamer hydrochloride. Cost-benefit analysis indicates that in the absence of hypercalcemia, calcium acetate should remain the treatment of choice for hyperphosphatemia in hemodialysis patients. Hyperphosphatemia is associated with increased mortality in hemodialysis patients and plays a key role in the
Dialysis & Transplantation, Sep 1, 2011
ASAIO transactions / American Society for Artificial Internal Organs
It is known that convective transport (ultrafiltration, QF) augments diffusive transport. This au... more It is known that convective transport (ultrafiltration, QF) augments diffusive transport. This augmentation achieves great importance as solute molecular weight increases. Previous mathematical treatments of dialysance (D) have provided the relationship between D and blood flow rate (QB), dialysate flow rate (QD), and dialyzer membrane surface area permeability product (KoA), in the limit of QF = 0. The authors derived the relationship between D (defined as D') and QB, QD, and KoA for the general case of QF greater than or equal to 0: D' = X-Y/In X/Y . [(1-ó) QF + KoA] for X = X(D', QF, QD) = 1 - [D'/QD + QF] Y = Y(D', QF, QB) = D'-QB/QF-QB ó = the Staverman reflection coefficient. This equation demonstrates an approximate linear increase in D' as QF increases. Experimental verification is provided by in vivo studies of dialysis patients in which the dialysance of vancomycin doubles as QF is increased from 0 to 50. Because D' varies linearly with QF, ...
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Papers by ROBERT HOOTKINS