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Biomedical subjects

A M Kaufman

Publications and source records attributed to A M Kaufman.

28 records · Page 2Linked to original sources
PubMed1985

Role of citrate excretion in acid-base balance in diuretic-induced alkalosis in the rat.

Studies were performed to assess the role of changes in the excretion of citrate, a metabolic precursor of bicarbonate, in acid-base balance in diuretic-induced metabolic alkalosis. Rats on a low-chloride diet with sodium sulfate added were studied during a base-line period, 3 days of furosemide administration, and 4 days post-furosemide. During the period of furosemide administration, net acid excretion and plasma bicarbonate concentration increased. In the post-furosemide period, net acid excretion remained higher than base line but plasma bicarbonate concentration did not increase further. Citrate excretion was significantly higher in the post-furosemide period than in base line. Studies substituting sodium neutral phosphate or sodium bicarbonate for dietary sodium sulfate demonstrated greater increases in net acid excretion post-furosemide and, again, no increase in plasma bicarbonate concentration during this period. Citrate excretion was greater than in the sulfate group. The increment in citrate excretion was proportional to the base "load," defined with respect to changes in net acid excretion and/or dietary bicarbonate. Thus, in these studies alterations of base excretion in the form of citrate play an important role in acid-base balance during diuretic-induced metabolic alkalosis.

Acid-Base Equilibrium↗
PubMed1983

Response to repeated frusemide administration on low chloride and low sodium intake in the rat.

In animals on a normal NaCl intake despite the repeated administration of a diuretic Cl and Na excretion return to baseline values after initial Cl and Na loss. In order to delineate whether this apparent resistance is consequent primarily on a decreased effect of the diuretic, or compensatory Cl and Na reabsorption when the diuretic is not acting, rats were injected with frusemide (1.5 mg twice a day intraperitoneally for 4 days) while on diets differing in Cl and Na content. On a normal NaCl diet Cl and Na excretion increased on day 1 and subsequently returned to baseline. On a low NaCl diet Cl and Na excretion remained above baseline on all 4 days, thereby demonstrating that frusemide continues to promote daily Cl and Na loss. On a low Cl-normal Na intake Na excretion returned to baseline after day 1, while Cl excretion remained above baseline on all 4 days. The increase in K and net acid excretion was highest in these studies. On a low Na-normal Cl intake Cl excretion returned to baseline after day 2, while Na excretion exceeded baseline on all 4 days. Daily K excretion increased least and net acid excretion decreased in these studies. Hourly data on all four diets indicate that frusemide always has an acute effect to promote both Cl and Na excretion. In the recovery period Cl or Na reabsorption is enhanced when the respective ion is available. The apparent resistance to daily frusemide administration on a normal NaCl intake is primarily consequent on enhanced reabsorption balancing the chloriuretic and natriuretic effects. Daily changes in K and net acid excretion are also determined, in part, by these opposing effects.

Aldosterone↗
PubMedDate not supplied

Variation in energy expenditure among black-legged kittiwakes: effects of activity-specific metabolic rates and activity budgets.

We sought to determine the effect of variation in time-activity budgets (TABs) and foraging behavior on energy expenditure rates of parent black-legged kittiwakes (Rissa tridactyla). We quantified TABs using direct observations of radio-tagged adults and simultaneously measured field metabolic rates (FMR) of these same individuals (n=20) using the doubly labeled water technique. Estimated metabolic rates of kittiwakes attending their brood at the nest or loafing near the colony were similar (ca. 1.3 x basal metabolic rate [BMR]), although loafing during foraging trips was more costly (2.9 x BMR). Metabolic rates during commuting flight (7.3 x BMR) and prey-searching flight (6.2 x BMR) were similar, while metabolic rates during plunge diving were much higher (ca. 47 x BMR). The proportion of the measurement interval spent foraging had a positive effect on FMR (R2=0.68), while the combined proportion of time engaged in nest attendance and loafing near the colony had a negative effect on FMR (R2=0.72). Thus, more than two-thirds of the variation in kittiwake FMR could be explained by the allocation of time among various activities. The high energetic cost of plunge diving relative to straight flight and searching flight suggests that kittiwakes can optimize their foraging strategy under conditions of low food availability by commuting long distances to feed in areas where gross foraging efficiency is high.

Alaska↗
PubMedDate not supplied

Cardiopulmonary recirculation in dialysis. An underrecognized phenomenon.

Access recirculation can be determined by measuring blood temperature or blood water concentration in the dialyzer inlet after injecting a bolus of cold saline into the venous line. In patients with access recirculation, some of the cooled venous blood re-enters the blood inlet line soon after injection, resulting in a sharp transient drop in its temperature. There is also a prompt increase in blood water concentration at the dialyzer blood inlet caused by the dilution effect of the recirculated saline. In this study, data are reported on four patients studied under conditions where no access recirculation could occur because blood was returned to a second access or into a central vein. In these patients, transient cooling of the blood in the dialyzer inlet and a transient hemodilution after venous line injection of cold saline was still observed. These observations can be explained by passage of the injected saline through the heart and pulmonary blood vessels and return of a portion of the cooled blood to the vascular access, bypassing the systemic capillary microcirculation. This "cardiopulmonary recirculation" can cause dilution of urea in dialyzer inlet blood, with resulting errors in urea kinetic modeling and in computing access recirculation.

Arteriovenous Shunt, Surgical↗
PubMedDate not supplied

Clinical experience with heat sterilization for reprocessing dialyzers.

Use of heat sterilization for dialysis reprocessing offers significant advantages over chemical germicides. Polysulfone dialyzers (Fresenius 60M or 80M) can be sterilized by heating to 105 degrees C for 20 hr, thus permitting clinical trials of this method. One hundred eighty patients received 9,000 treatments. Pyrogenic reactions, sepsis, and subjective symptoms have not occurred. In vitro clearances (Qb 500 ml/min, Qd 800 ml/min) at baseline and after 2-8 uses did not differ (340 +/- 29 vs. 352 +/- 4 ml/min, respectively). KoA determined in vivo did not decrease (baseline 709 +/- 131 vs. 7th use 632 +/- 50 ml/min). Kt/V for urea was not different in 18 patients treated with heat sterilized dialyzers over 6 months when compared with a baseline period with formaldehyde sterilized dialyzers (1.37 +/- 0.12 vs. 1.32 +/- 0.11 at similar time and blood flows). Mean use number was 7.4 (dialyzers limited to 11 uses). Of discarded dialyzers, 44% failed a bedside integrity test (blood side pressurized at > 400 mmHg for 1 min), 36% failed automated fiber bundle or pressure holding tests, 8% had a blood leak, and 12% reached 11 uses. Clinical blood leaks occur in < 0.5% of treatments. Heat sterilization is a safe and effective method of dialysis reprocessing, but quality control of the process is essential. Based on initial clinical experience, heat sterilization of dialyzers for reuse is a promising alternative to chemical disinfection.

Blood Urea Nitrogen↗
PubMedDate not supplied

Relative underestimation of fluid removal during hemodialysis hypotension measured by whole body bioimpedance.

Whole body bioimpedance is considered helpful in monitoring the removal of excess body water by ultrafiltration in hemodialysis patients. In this study, the cumulative, estimated decrease in extracellular volume (V(est)) modeled from whole body bioimpedance data was compared with measured volume (Vmeas) removed by ultrafiltration (UFR = 1.01 +/- 0.31 L/hr) in 12 patients during 36 high efficiency hemodialysis treatments. In the mean, estimated (V(est) = 3.0 +/- 1.4 L) and measured volumes (Vmeas = 3.4 +/- 1.1 L) correlated linearly: V(est) = 1.05 x Vmeas - 0.60, r2 = 0.68. Patients developed hypotension in half the treatments. Except for a larger decrease in systolic blood pressures in hypotensive (34 +/- 24 mmHg) vs. stable (14 +/- 15 mmHg) treatments, patient and treatment characteristics were not different between groups. However, at the end of hemodialysis, the difference V(est) - Vmeas was -0.8 +/- 0.9 L in hypotensive, and only 0.1 +/- 0.4 L in stable patients (p < 0.05). The difference between V(est) and Vmeas can be explained by a predominant removal of excess body water from central body compartments such as the trunk and the central blood volume during hypotension. These compartments are not adequately measured by whole body bioimpedance techniques. However, this information could be helpful in identifying patients with delayed peripheral fluid removal that may occur when either target weight is too low or UFR rates are too high.

Adult↗
PubMedDate not supplied

In vivo verification of an automatic noninvasive system for real time Kt evaluation.

It is generally accepted that morbidity and mortality of hemodialysis patients is related to dialysis quantitation. Currently available methods for the quantitation of dialysis require blood sampling or a continuous measurement of changes in urea concentration during treatment. These maneuvers are time consuming and expensive, and are generally performed, at most, once per month. The authors introduce an on-line, automated method for measurement of dialyzer electrolyte clearance comparable to urea clearance by using dialysate conductivity sensors placed pre and post dialyzer, and measuring conductivity at three different pre dialyzer levels. Conditions that reduce clearance, such as recirculation or fiber clotting, are automatically taken into account so that the method measures effective clearance rather than dialyzer clearance. In vitro and in vivo studies validate the method. Results are immediately available and can be used to address problems such as improper needle placement and access recirculation. In addition, repetitive electrolyte clearance data can serve to enhance quality assurance programs with respect to verifying the function of reused or new dialyzers. Appropriate algorithms can be used to calculate delivered Kt/V.

Blood Urea Nitrogen↗