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Biomedical subjects

M H Sigler

Publications and source records attributed to M H Sigler.

At least 19 recordsLinked to original sources
PubMed1998

Continuous renal replacement therapies: an update.

Continuous renal replacement modalities have found widespread use and acceptance over the last decade. The various modalities differ in the kind of access (arteriovenous v venovenous); in the application of convective clearance (continuous hemofiltration), diffusive clearance (continuous hemodialysis), or a combination of both (continuous hemodiafiltration); and in the location where the replacement fluid enters the circuit (predilution v postdilution). Continuous therapies incorporate several advantages, such as improved hemodynamic stability, the possibility for unlimited alimentation, optimal fluid balance, and gradual urea removal without fluctuations. However, it has not yet been shown whether these advantages have a significant impact on outcome and prognosis, the ultimate measure of treatment efficiency. Major disadvantages of continuous therapies are the ongoing necessity for continuous anticoagulation, immobilization of the patient, and possible side effects from lactate-containing replacement fluid or dialysate. Continuous renal replacement procedures have certainly made the management of critically ill patients easier. In particular, oligoanuric patients with diuretic resistant volume overload and hemodynamically unstable patients with acute renal failure and concomitant sepsis or multiorgan failure appear to benefit most from continuous treatment. The role of continuous hemofiltration as a method of removing serum cytokines in septic patients without renal failure is still controversial and needs further clinical assessment. Due to slow efficacy, continuous renal replacement is indicated only in rare circumstances for intoxication; this therapy also is of rather limited use in severe hyperkalemia or acidosis. Noncritically ill patients with uncomplicated renal failure (eg, due to the use of dye or antibiotics) should be treated with intermittent hemodialysis or peritoneal dialysis. Furthermore, intermittent hemodialysis is preferable in patients with hemorrhagic diathesis because it can be easily performed without anticoagulants.

Anticoagulants↗
PubMed1997

Transport characteristics of the slow therapies: implications for achieving adequacy of dialysis in acute renal failure.

Slow continuous renal replacement therapy is used primarily to treat critically ill patients with acute renal failure. Knowledge of the small solute transport characteristics in continuous renal replacement therapy (CRRT) provides a rational basis for the manipulation of operating conditions to achieve desired clearances and, hence, desired metabolic control. These manipulations simply involve varying the dialysate inflow rate, the ultrafiltration rate, and the substitution fluid replacement rate. For the diffusion-based therapies, the condition of dialysate saturation, ie, exiting dialysis fluid urea nitrogen (FUN) approximating inflowing plasma water urea nitrogen (BUN, ie, the FUN/BUN ratio approximately 1), simplifies these manipulations. Examples of the calculations required to compute urea generation rate, protein catabolic rate, and the desired clearances are given. However, all of these calculations leave unanswered the question of "what is adequate dialysis" in the critically ill patient with acute renal failure. In the absence of the data that are required to answer this question, one can only say that if dialysis makes a difference, the persistently high mortality rate in intensive care unit acute renal failure suggests that patients are not receiving enough Kt/V. The reasons why CRRT is inherently more efficient than intermittant hemodialysis are explored. The usual reasons why prescribed therapy is less than delivered therapy with respect to slow continuous therapy are also discussed.

Acute Kidney Injury↗
PubMed1997

Plasma glucose turnover and oxidation during hemodialysis: nutritional effect of dialysis fluid.

Mass transfer of glucose from dialysis fluid into patients is a source of energy and a form of nutrition during hemodialysis. The effect of glucose mass transfer on endogenous glucose metabolism and the overall nutritional importance of glucose transfer is not known. Rates of plasma glucose turnover and oxidation were determined by radioisotope-dilution techniques in patients with chronic renal failure (CRF) in the basal state, during hemodialysis, and during the infusion of glucose at a rate similar to the mass transfer rate (Mt: 6.6 +/- 0.7 mumol.min-1.kg-1). Rates of plasma glucose turnover (11.8 +/- 0.8 mumol.min-1.kg-1) and oxidation (4.0 +/- 0.4 mumol.min-1.kg-1) and contribution of glucose oxidation to the metabolic rate were similar to those of control subjects both in the basal state and during glucose infusion. During hemodialysis with acetate and glucose, the plasma glucose turnover rate was similar to that in the basal state, but the energy from glucose oxidation was less (P < or = 0.02) even though energy expenditure was increased by 21%. Immediate oxidation of plasma glucose and acetate accounted for 65% of the patients' energy expenditure. Energy (1172 kJ) from acetate Mt and glucose Mt surpassed the patients' energy requirements, offsetting the utilization of endogenous fuels, a sparing effect equivalent to 31 g fat or 70 g carbohydrate. Rates of plasma glucose turnover and oxidation during bicarbonate-glucose and glucose-free acetate hemodialysis were similar to that during acetate-glucose hemodialysis. However, without glucose or acetate in the bath fluid, a deficit as much as 669 kJ must be met by the oxidation of endogenous fuels. Addition of organic nutrients that supply energy to dialysis fluids may over time be a beneficial supplemental treatment for the malnutrition and body wasting commonly observed in CRF.

Acetates↗
PubMed1991

Suppression of renal vein renin profiles by mannitol prophylaxis: implications in the evaluation of renovascular hypertension.

Renal arteriography with concomitant renal vein renin profiling remains the diagnostic standard for evaluating the anatomic and physiologic significance of stenotic renal artery lesions in hypertensive patients. False-negative renal vein renin profiles with failure of lateralization in patients with anatomically apparent high-grade stenosis complicate the diagnostic process. Mannitol is frequently administered prophylactically to minimize the risk of dye nephropathy in these patients. Yet, the potential effects of mannitol on renal vein renin profiling in man have not been previously reported. Seven patients with renovascular hypertension were studied prospectively to determine changes in renal vein renin profiles before and after mannitol prophylaxis. Despite captopril stimulation, all patients demonstrated significant renin suppression leading to the loss of renin lateralization in patients with unilateral renovascular hypertension. In 60% of the patients, renal vein renin ratios fell to below the standard 1.5 to 1 ratio after mannitol infusion. In patients with bilateral renovascular disease, the least stenotic side suppressed completely, while the more stenotic side suppressed partially. Percent suppression analysis showed a mean suppression of 56.8% on the stenotic side versus 8.2% on the noninvolved side (P less than 0.002). In every study, suppression equaled or exceeded 32% on the involved side and was less than this on the noninvolved side. Thus, the degree of renin suppression following mannitol infusion may prove to be an important tool in the diagnosis of clinically significant stenotic lesions. The mechanism of mannitol-induced suppression remains undefined, but appears independent of volume expansions or dilutional effects. The inhibitory effects of mannitol on renin profiles can obscure the diagnosis of underlying renovascular hypertension.

Adult↗
PubMed1990

Urea kinetic analysis and clinical outcome on CAPD. A five year longitudinal study.

The present study, along with some recent studies, suggests that there is an organic link between the amount of dialysis a patient receives and his/her nutritional status. The latter, as reflected by serum albumin, is predictive of survival on CAPD. It is clear, therefore, that urea kinetic analysis is a powerful tool for prescribing and monitoring therapy in CAPD patients.

Blood Urea Nitrogen↗
PubMed1989

Successful treatment of postparathyroidectomy hypocalcemia using continuous ambulatory intraperitoneal calcium (CAIC) therapy.

Severe, recalcitrant hypocalcemia and hungry bone syndrome can complicate parathyroidectomy in end-stage renal disease patients. Treatment with prolonged and massive doses of intravenous calcium, with calcitriol supplementation, is often necessary, but potentially dangerous and may prolong hospitalization. Three CAPD patients (including 1 with malabsorption) were safely treated by adding 1 to 3 ampules (10-30 mL) of 10% calcium gluconate solution to each bag of dialysate for up to 29 months. Continuous ambulatory intraperitoneal calcium (CAIC) therapy was initiated postoperatively and continued on an outpatient basis until the patients' hungry bone syndrome resolved and serum calcium normalized. Complications such as visible dialysate precipitation or an increased rate of peritonitis were not observed. Mean total calcium uptake was approximately 137 to 226 mg/exchange. We conclude that CAIC therapy is a safe, effective treatment both for CAPD patients with postparathyroidectomy hypocalcemia with hungry bone syndrome, as well as in patients with hypocalcemia secondary to malabsorption.

Calcium Gluconate↗
PubMed1987

Solute transport in continuous hemodialysis: a new treatment for acute renal failure.

A pumpless dialysis technique which combines continuous convection and diffusion was studied in 15 critically ill acute renal failure patients. Fluid identical in composition and purity to that used in peritoneal dialysis was continuously circulated (single-pass) at 16.6 cc/min through the dialysis compartment of a 0.43 m2 flat plate PAN membrane dialyzer. Whole blood clearances for urea, creatinine and phosphate averaged 25.3 +/- 4.4 cc/min, 24.1 +/- 5.5 cc/min and 21.3 +/- 5.6 cc/min, respectively. Over the range of blood flows studied (50 to 190 cc/min) clearances of these solutes were independent of blood flow rate but rather were determined by both dialysate flow rate and ultrafiltration rate. In contrast net fluxes of calcium and sodium were correlated only with ultrafiltration rate. Bicarbonate loss was 0.52 +/- 0.11 mEq/min; K+ balance varied with dialysate K+; glucose uptake from dialysate was 107 +/- 24.0 mg/min. In fresh non-clotting dialyzers, mean ultrafiltration rate was 8.1 cc/min. At QBi of 70 to 190 cc/min, dialysate and blood solute equilibrate yielding a total clearance equal to the dialysate outflow, or 25 cc/min, that is, the sum of dialysate flow rate plus ultrafiltration rate. In comparison to currently used continuous arteriovenous hemofiltration (CAVH), the exceptionally-high solute clearances obtained with continuous hemodialysis constitute a significant improvement in continuous renal replacement therapy.

Acute Kidney Injury↗
PubMed1983

Contribution of dialysate acetate to energy metabolism: metabolic implications.

During hemodialysis large amounts of acetate enter the bloodstream. Generally, it is assumed that this exogenous acetate load is oxidized immediately to carbon dioxide and water; however, the rate of plasma acetate oxidation and the effect of acetate oxidation on energy metabolism during hemodialysis has not been determined previously. The rates of plasma acetate turnover and oxidation were determined during hemodialysis in seven chronic renal failure patients by the primed continuous infusion of [1-14C] acetate. The plasma acetate turnover rate (57.2 +/- 2.9 mumoles/min X kg) agreed closely with the mass transfer rate of dialysate acetate into the bloodstream (55.3 +/- 3.2 mumoles/min X kg). Of the acetate entering the bloodstream, 54.5 +/- 5.2% or 31.6 +/- 3.77 mumoles/min X kg was oxidized immediately accounting for 40.3 +/- 4.8% of the patient's caloric expenditure. Although the oxidation of acetate during dialysis supplied a major portion of the patient's caloric need, a significant quantity of acetate was eliminated by pathways other than direct oxidation. An average overall respiratory quotient (RQ) of 1.0 +/- 0.02 indicated that fat oxidation was spared to maintain energy homeostasis during hemodialysis. The calculated non-protein RQ exceeded unity suggesting that net fat synthesis actually occurred.

Acetates↗
PubMed1983

Acetate and energy metabolism during hemodialysis.

The oxidation of acetate infused in acetate infused in large quantities during acetate dialysis should provide considerable energy for the hemodialysis patient. Previous attempts to measure acetate oxidation rate and thus energy yield by measuring bicarbonate generation rate are flawed because bicarbonate generation occurs by equimolar proton consumption when acetate is activated to acetyl Co-A but before acetyl Co-A has entered the Krebs cycle. Besides the Krebs cycle, acetyl Co-A could enter many other nonoxidative pathways. By using the primed continuous infusion radioisotope (1-14C acetate) dilution technique of Steele, in conjunction with indirect calorimetry, we obtained direct measurements of acetate turnover and immediate oxidation rates and energy yield in 7 stable hemodialysis patients. Commercial dialysate contained glucose (12.4 mmoles/liter), acetate (38 mmoles/liter), plus routine electrolytes. Acetate turnover was 57.2 +/- 2.9 mumoles/min X kg. Of the acetate entering the body, 31.6 +/- 3.8 mumoles/min X kg were immediately oxidized to carbon dioxide and water, which accounted for 54.4 +/- 5.2% of the turnover rate. The amount that entered the blood was 869 mmoles, and 472 mmoles (54.4%) were oxidized; 138 mmoles (15.8%) made up the steady-state pool, and 258 mmoles were directed into nonoxidative pathways (29.7%). During dialysis, 40.3 +/- 4.8% of the carbon dioxide output or metabolic rate was accounted for by acetate oxidation. Thus, acetate emerged as the major contributor to energy production, supplying up to 65% of the total caloric needs during dialysis. The RQ calculated from the lung carbon dioxide excretion was 0.74 +/- 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1980

Acid-base balance in continuous ambulatory peritoneal dialysis.

Metabolic acidosis was demonstrated in a group of anuric CAPD patients. Dialysate HCO3- loss was the major determinant of a negative base balance of 26.4 +/- 23.5 mMol/day. Bicarbonate supplementation corrected the acidosis. A primary respiratory alkalosis was also present in several patients.

3-Hydroxybutyric Acid↗
PubMed1978

Plasma pyridoxal-5'-phosphate levels and clinical correlations in chronic hemodialysis patients.

Plasma pyridoxal-5'-phosphate (PLP) was measured by a specific method in 45 stable, chronic hemodialysis patients and 13 normal adults. Despite oral pyridoxine supplements (1 to 5 mg/day) a majority (64%) of patients had low levels. The difference between normals (8.5 +/- 3.7 ng/ml) and dialysis patients (3.6 +/- 3.6 ng/ml) was significant at P less than 0.01. Plasma PLP appeared to decrease with increasing duration of time on dialysis therapy. In vivo clearance studies as well as pre- and postdialysis plasma levels indicated that PLP was not removed by the dialyzer. Mean plasma PLP levels were normal in patients with stable motor nerve conduction velocity and a low transfusion requirement and low in those with decreasing motor nerve conduction velocity or a high transfusion requirement but the difference between the means in each group was not statistically significant. High oral doses of pyridoxine (100 to 200 mg/day) but not low doses (1 to 5 mg/day) restored PLP levels to normal in a majority of patients after 2 weeks.

Adult↗
PubMed1975

The mechanism of the natriuresis of fasting.

This study tests the hypothesis than obligatory cation coverage of metabolicaly generated anions is the mechanism for the sodium diuresis of fasting. Nine obese female subjects were equilibrated on a constant sodium and caloric intake and then fasted while sodium intake was maintianed. Particular activity schedule during fasting as during control. Consecutive 3-h increases in urinary sodium , ammonium, and potassium excretion during fasting were matched against simultaneously determined increases in organic acid anions (OAS) and H2PO4 minus, which would exist in combination with the cations. The changes were significantly correlated (r equals 0.891, P less than 0.001) in the relationship y equals 0.73x plus 19 where y equals increases in organic acid salts plus H2POJ minus and x equals increases in cations. As ammonium excretion rose, sodium conservation occurred with ammonium replacing sodium at the major urinary cation. Corollaries to the hypothesis were also found to be true. They were: (a) Increases in ammonium excretion lagged considerably behind increases in OAS plus H2PO4 minus during the diuretic phase making sodium coverage necessary. (b) Sodium loss was much greater than chloride although chloride balance was minimally negative. (c) After refeeding with glucose, sodium excretion promptly decreased and appeared best correlated with simultaneous decreases in OAS. Ammonium excretion also fell but much less than sodium. The data support the hypothesis that obligatory cation coverage of metabolically generated aniuns is a major mechanism responsible for the sodium diuresis of fasting.

Activities of Daily Living↗