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Biomedical subjects

C W Walter

Publications and source records attributed to C W Walter.

At least 37 records · Page 2Linked to original sources
PubMed1982

Effect of freezing and microwave thawing on the stability of six antibiotic admixtures in plastic bags.

The stability of six antibiotics in intravenous fluids in polyvinyl chloride containers after freezing and microwave-thawing is reported. Tobramycin sulfate 160 mg, amikacin sulfate 1 g, ticarcillin disodium 3 g, clindamycin phosphate 300 mg, nafcillin sodium 1 g, and ampicillin sodium was also diluted in plastic bags of 0.9% sodium chloride injection 50 ml. For each antibiotic except ampicillin sodium, three bags were prepared and assayed immediately for antibiotic content. Two of the bags were frozen at -20 degrees C for 30 days and then thawed, one by exposure to room-temperature air and the other by microwave radiation. Each was assayed immediately and after 8 and 24 hours storage at room temperature. The third bag was not frozen, but was stored at room temperature and assayed at 8 and 24 hours. Five bags of ampicillin sodium were prepared-three in 0.9% sodium chloride, which were frozen at -20, -30, and -70 degrees C, and two in 5% dextrose, which were frozen at -30 and -70 degrees C. All ampicillin solutions were stored 30 days, assayed, microwave-thawed, and assayed again. All antibiotics except ampicillin retained 90% or more potency when microwave-thawed after storage at -20 degrees C for 30 days, and after subsequent storage at room temperature for 24 hours. Ampicillin sodium was stable in 0.9% sodium chloride when stored at -30 or -70 degrees C, microwave-thawed, and stored up to eight hours at room temperature. Ampicillin sodium was stable in 5% dextrose when stored at -70 degrees C and microwaved-thawed, but its potency declined to 70.5% after eight hours storage at room temperature.

Anti-Bacterial Agents↗
PubMed1980

Detection of endotoxin on sterile catheters used for cardiac catheterization.

Pyrogen reactions during cardiac catheterization are an alarming complication that frightens patients and baffles many physicans. This report describes a simple, reproducible, precise technique for the measurement of endotoxin-like activity on the inner and outer surfaces of catheters intended for intravascular insertion. This technique is useful in documenting the cause of patient reactions. Quality control procedures should be instituted following the manufacture of angiographic catheters so that pyrogen-free products are availabe for patient use. Catheters processed in a hospital are easily contaminated with fever-producing lipopolysaccharides from tap water or from bacterial growth in residual moisture. Sterilization by steam or ethylene oxide does not destroy these lipopolysaccharides. Consequently, reprocessing reusable catheters must include concern for removing lipopolysaccharides as well as sterilization.

Cardiac Catheterization↗
PubMed1980

Potential hazards associated with microbial contamination of in-line filters during intravenous therapy.

The survival and multiplication of Enterobacter agglomerans, Klebsiella pneumoniae, Serratia marcescens, and Pseudomonas aeruginosa in 0.45- and 0.22-micrometer in-line filter sets during simulated infusions were studied to evaluate the ability of each filter type to prevent infusions of these bacteria into patients. Bacteria were found to proliferate in the upstream compartment of sets housing both filter porosities. None of the 0.22-micrometer in-line filters were penetrated by the test bacteria. In contrast, P. aeruginosa was observed to penetrate each 0.45-micrometer in-line filter examined within 12 h of continuous infusion. Tribe Klebsielleae organisms penetrated a proportion of the 0.45-micrometer filters usually between 48 and 72 h of infusion. In addition, the elution of endotoxin from gram-negative bacteria trapped in the filter set during infusion is reported. Collected infusion filtrate exhibited a trend of increasing endotoxin-like activity with an increasing duration of infusion. In the case of E. agglomerans, mean peak levels of approximately 65 pg of Escherichia coli endotoxin per ml were attained after 72 h. Other bacteria produced similar results, except mean peak levels ranged from 5 to 30 pg/ml. It was noted that endotoxin-like activity was not detected in filtrate eluted from contaminated filter sets during the initial 24 h of infusion. We conclude that to avoid potential hazards of bacterial penetration and endotoxin production during continuous use of in-line filter sets, the 0.22-micrometer filter type must be employed and replaced every 24 h.

Endotoxins↗
PubMed1980

The application of a freeze-microwave thaw technique to central admixture services.

The establishment of a centralized, intravenous solution/admixture drug program in a hospital enhances the quality of patient care. Costs for personnel, equipment, and space have constrained the growth of such a service in the past. A method of preparation for admixture units, which capitalizes on the economics of volume and employs personnel at levels of training consistent with need, is proposed. This technique, utilizing freezing, long-term storage at -20 degrees C, and thawing by exposure in a microwave oven minutes before intended use, surmounts the real and perceived difficulties in many planned or existing admixture programs. A strong element of prospective quality control can be introduced. Where demand is insufficient to justify a separate activity, cooperative arrangements among hospitals will bring all the advantages of central admixture to each. It appears that reductions can be made in the pharmacy hours devoted to admixture. Waste of any unused, reconstituted drugs or prepared units that were not administered may be diminished. Thus, there may be substantial savings for existing admixture programs, if the technique described is adopted. The ultimate form of implementation in each institution, as always, is dependent upon the special "personality" of the hospital.

Anti-Bacterial Agents↗
PubMed1980

Activity of antibiotic admixtures subjected to different freeze-thaw treatments.

The freezing of antibiotic admixtures has been proposed as a potentially useful method by which the efficiency of admixture services might be improved. The time involved in thawing, however, has discouraged the implementation of this practice. This study describes a technique of thawing frozen antibiotic admixtures contained in minibags in commercially available microwave ovens. A quantitative microbiological agar gel diffusion assay was employed to determine the effect of such treatment on the antibiotic activity of the admixture. Admixtures containing cephalothin sodium, cefazolin sodium, cefamandole nafate, cefoxitin sodium, penicillin G potassium, ampicillin sodium, oxacillin sodium, carbenicillin disodium, and gentamicin sulfate in dextrose 5% solution were frozen at -20 degrees C for 30 days. The admixtures were assayed immediately before freezing, and again after either thawing technique: that is, upon exposure of the minibags to room temperature air or to microwave radiation. Assays were also performed 8 and 24 hours after thawing in order to assess antibiotic stability following each freeze-thaw treatment. It was discovered that, with the exception of ampicillin sodium, each of the antibiotics studied could be frozen and thawed as described without significant loss of activity, and were stable for 24 hours after thawing. The application of a freeze microwave-thaw technique to central admixture services can be seen as a cost-effective method of circumventing many of the problems associated with existing programs.

Anti-Bacterial Agents↗