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Biomedical subjects

R D Leff

Publications and source records attributed to R D Leff.

At least 37 records · Page 2Linked to original sources
PubMed1988

Flow rate variability from selected syringe and mobile infusion pumps.

Alterations in response to pharmacological agents have been attributed to flow rate variation produced by intravenous infusion devices during drug delivery. A wide range of variation has been shown to occur with large-volume infusion devices. The intent of this investigation was to examine flow variation resulting from the use of selected small-volume syringe and mobile infusion devices and determine whether these devices have greater flow continuity than large-volume infusion pumps. Each syringe and mobile infusion device delivered iv fluid at three flow rates (1, 5, and 10 ml/h). The effusate was collected in a tared beaker and serial weights were measured every ten seconds using a computerized, gravimetric technique. Accuracy, continuity, and pattern of flow were determined for each of the syringe and mobile infusion devices. All of the devices produced accurate flow, within +/- 10 percent of the desired 5 and 10 ml/h rates. However, the actual iv flow rate ranged from 53 to 93 percent for the 1 ml/h rate. Continuity and pattern of flow resulting from each device were diverse. When compared with large-volume, microrate infusion devices, no significant differences could be observed. Therefore, no clear advantage to delivering drug solutions on a continuous basis can be expected from the use of small-volume devices. Specific infusion devices may be preferable for certain clinical applications; flow continuity data may be valuable when selecting an infusion device.

Evaluation Studies as Topic↗
PubMed1988

Enteral drug administration practices: report of a preliminary survey.

This study was initiated to determine whether there is sufficient variation in enteral drug administration practices in hospitalized pediatric patients to result in adverse therapeutic consequences. A survey was developed and administered to nurses from three pediatric and six general hospitals. A total of 317 pediatric nurses responded. Results of the survey confirmed that the primary responsibility for administering enteral medications resides with the nurse. It also documented that many elements in the administration of enteral medications vary significantly among nurses, although nursing personnel expressed confidence in the efficacy of their individual drug administration techniques. Further quantitative evaluations of the efficacy of practices of enteral drug administration must be performed before meaningful standardization of drug administration techniques can be accomplished.

Administration, Oral↗
PubMed1988

Accuracy, continuity, and pattern of flow from five macrorate infusion pumps.

The accuracy, continuity, and pattern of flow from five commercially available macrorate infusion pumps were evaluated in vitro. Intravenous fluid was run through each infusion device at 5, 10, and 50 mL/hr. The weight of the fluid was measured serially after flow periods of 5, 10, and 15 sec for each device at each flow rate using a computerized gravimetric technique. The influence of the type of pump, flow rate, and sample-collection time on flow continuity was determined. Flow continuity (variation in flow) was expressed as the coefficient of variance of the measured weights. All of the infusion devices had flow rates within 5% of the desired rates of 5, 10, and 50 mL/hr. Flow continuity was significantly affected by the type of pump used but not by either flow rate or sample-collection time. All five devices had unique flow patterns attributable to their respective pump-operating mechanisms. The method of drug delivery and, in particular, the pump-operating mechanism of a given infusion device may affect flow continuity; therefore, alterations in clinical response to a continuous drug infusion must not be attributed exclusively to the drug or the clinical condition of the patient. Further in vitro and in vivo evaluations are needed to define the clinical importance of these data.

Infusions, Intravenous↗
PubMed1987

The popliteal cyst.

Explore the source record for details and available documents.

Diagnosis, Differential↗
PubMed1987

A gravimetric technique for evaluating flow continuity from two infusion devices.

A computerized gravimetric technique for examining the flow continuity from infusion devices was developed, and two infusion devices with different mechanisms of pump operation were evaluated to illustrate this technique. A BASIC program that records serial weight measurements and calculates weight change from previous determinations was written for and interfaced with a gravimetric balance and IBM PC. A plot of effused weight (normalized weight change that reflects the difference between desired timed-sample interval and actual time) versus time (desired timed-sample interval) was constructed. The gravimetric technique was evaluated using both a peristaltic-type and a piston-type infusion pump. Intravenous solution (5% dextrose and 0.9% sodium chloride) was effused at 10 mL/hr and collected in a beaker. Weights were measured at 10-second intervals over a two-hour infusion period, and the weights of the effused solution were plotted versus time. Flow continuity differed between the two infusion devices. Actual effused weight decreased to 0.007 g/10 sec during the refill cycle of the piston-type pump; the mean (+/- S.D.) effused weight was 0.029 +/- 0.002 g/10 sec. The desired effusion rate was 0.028 g/10 sec. The peristaltic pump had greater flow continuity, with a mean effusion weight of 0.028 +/- 0.003 g/10 sec. The gravimetric technique described in this report can be used to quantitatively depict the effusion profiles of infusion devices. Further studies are needed to identify the degree of flow continuity that is clinically acceptable for infusion devices.

Infusion Pumps↗
PubMed1986

Phenytoin metabolism in infants following intravenous and oral administration.

The disposition of phenytoin was examined in 7 infants with a mean age of 22 days and a mean weight of 3,756 g. Multiple doses of phenytoin were administered intravenously and/or orally as a part of required medical care. Gas chromatography/mass spectrometry was employed for analyses of phenytoin and three metabolites - 5-(4-hydroxyphenyl)-5-phenylhydantoin, methylated 3,4-catechol, and 3,4-dihydrodiol - in blood, urine, and feces. Data from identical studies previously conducted in adults were utilized for comparison with the infants. The mean phenytoin dose (+/- SD) in infants was 8.1 +/- 4.4 mg/kg/day, and the mean serum concentration (+/- SD) was 4.8 +/- 4.6 micrograms/ml. In adults, the mean dose was 5.3 +/- 0.6 mg/kg/day, and the mean serum concentration was 12.0 +/- 1.9 micrograms/ml. No significant differences were found between infants and adults in the pattern of urinary metabolites or in the total recovery of phenytoin and metabolites in 24-hour urine samples. These results indicate that pathways for phenytoin metabolism are the same in infants and adults. Absorption of an oral dose of phenytoin in infants appeared to be completely based on recoveries of drug and metabolites in urine and on the fact that less than 3% of an oral dose could be found in stools. The results of these studies indicate that the low blood concentrations of phenytoin resulting from the relatively high daily dosage of phenytoin in infants, when compared to adults, cannot be explained on the basis of poor oral absorption of phenytoin. These age-related differences must be due to a relatively high metabolic clearance of the drug in infants.

Administration, Oral↗
PubMed1986

Postpericardiotomy syndrome.

Postpericardiotomy syndrome, a frequent complication of open-heart surgery, is characterized by fever, chest pain, and pericardial and pleural effusions. These signs may develop 1 to 12 weeks after intracardiac surgery in approximately 30 percent of patients. Although the etiology of the syndrome is unknown, evidence points to a viral and/or autoimmune cause. Postpericardiotomy syndrome is diagnosed after excluding other conditions such as endocarditis and pneumonia. In many cases, the syndrome is self-limiting and occurs only once, but in other cases the symptoms have recurred as many as eight times. When the symptoms recur, management is more difficult because optimal pharmacologic treatment is not known. Antiinflammatory agents, such as salicylates and steroids, represent the drugs most commonly used. Although analgesics with codeine or oxycodone are important for the patients' symptomatic relief, early recognition of the syndrome is the key to limiting the discomfort and possible complications associated with this condition.

Analgesics↗
PubMed1985

Evaluation of an extension set for intermittent intravenous drug delivery to infants.

An intravenous administration set designed for delivery of drug doses to pediatric patients was tested in vitro for the effect of fluid density and flow rate on drug delivery, and delivery of drug by this extension set was compared in vivo with delivery by other methods. Gentamicin (as the sulfate salt) and penicillin G potassium were used to represent low-density and high-density drugs, respectively; a 1-mL solution of each drug, labeled with carbon 14, was tested with each of two primary infusion solutions: 0.45% sodium chloride injection and 10% dextrose injection. The drug dose was injected via a port into a piston-containing chamber from which an equivalent amount of the primary fluid was displaced. Serial samples collected from the end of the filter-containing extension set were analyzed for drug concentration using a liquid scintillation technique. In 12 infants receiving i.v. gentamicin, this delivery method was compared in a randomized crossover trial with delivery by a syringe pump and by i.v. push. Each delivery system was used on one of three consecutive days, and serum gentamicin concentrations were measured by enzyme-multiplied immunoassay. The time required for in vitro delivery of the dose was dependent on flow rate. Density of the drug solution or the primary i.v. fluid did not significantly affect drug delivery. Serum gentamicin concentrations were not significantly different for the three delivery methods, but variability of drug delivery was greatest with the pediatric extension set. This pediatric extension set provides accurate and reliable drug delivery at primary infusion flow rates slower than 10 mL/hr when the drug dosage volume is 2-3 mL or less.

Evaluation Studies as Topic↗
PubMed1985

Factors affecting drug delivery from a syringe-pump infusion set.

In vitro testing of drug delivery via dual-lumen, small-volume i.v. extension tubing designed for use with a syringe pump was conducted. From a dual-lumen extension set with intraluminal diameters of 0.020 inch, effluent samples were collected at 5, 10, and 20 minutes after injection of a 1-mL volume of drug solution intended for delivery over 20 minutes by a syringe infusion pump. Variables were flow rate (5 or 25 mL/hr) of the primary infusion, tubing position (vertical or horizontal), and density of the drug solution (penicillin G potassium 250,000 units/mL and aminophylline 25 mg/mL represented high and low specific gravities, respectively). Each drug solution was labeled with radioactive carbon and the drug content of the effluent was analyzed by liquid scintillation. For each set of variables, samples were also tested after the tubing was flushed with 5% dextrose injection 0.2-0.6 mL. Similar procedures were followed to determine delivery of the labeled penicillin G potassium solution via a dual-lumen extension set with intraluminal diameters of 0.020 inch (for drug) and 0.060 inch (for the primary infusion); a 13-mm-diameter, 0.2 micron filter was attached to the smaller-lumen tubing. A primary infusion flow rate of 5 mL/hr and flush volumes of 0.3 and 0.6 mL were used in this study. To determine the influence of intraluminal diameter on the flush volume required for delivery of a dose of aminophylline (1-mL volume), single-lumen extension tubings with different diameters were tested. The final percentage of the drug dose delivered via the dual-lumen extension set with 0.020-inch lumens was affected only by flush volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Infusions, Parenteral↗
PubMed1984

Effects of intravenous delivery systems on infused red blood cells.

The effects of various intravenous delivery systems on the integrity of infused red blood cells (RBCs) were studied. Using a factorial design, whole blood and packed RBCs were infused through i.v. delivery systems employing various combinations of i.v. tubing diameter and length, needle gauge, infusion rate (5 and 50 ml/hr), type of infusion pump (piston, diaphragm, or peristaltic operation), and type of blood product. The age and temperature of the blood filter used were held constant. A 5-ml sample of the blood product obtained during each experimental run was analyzed for plasma free-hemoglobin to assess the degree of hemolysis. Osmotic fragility of the RBCs was evaluated by measuring the percentage of hemolysis in the blood products in various concentrations of sodium chloride solution. Type of blood product and i.v. pump were the only variables significantly influencing RBC hemolysis. In both blood products, a greater degree of hemolysis occurred with the peristaltic-type pump than with the other types of pumps. In packed RBCs, the diaphragm-type pump produced greater hemolysis than the piston-type pump, but hemolysis was similar in whole-blood samples. Regardless of the type of pump, more hemolysis occurred in whole blood at the 5-ml/hr infusion rate than at the 50-ml/hr rate, but the converse was true in packed RBCs. Samples of both blood products were less osmotically fragile than their respective controls at sodium chloride concentrations ranging from 0.30 to 0.50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Transfusion↗