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Biomedical subjects

R D Jenkins

Publications and source records attributed to R D Jenkins.

28 records · Page 2Linked to original sources
PubMed1986

Early experience with continuous arteriovenous hemofiltration in critically ill pediatric patients.

The applicability of continuous arteriovenous hemofiltration (CAVH) for renal replacement therapy was evaluated in three infants and two young children with catastrophic medical and surgical illnesses. In the first four patients, CAVH was used in conjunction with either peritoneal or hemodialysis. In the fifth patient, CAVH was the sole renal replacement therapy employed; in this critically ill anuric infant, we were best able to evaluate the ability of CAVH to continuously control fluid, electrolyte, and acid-base balance, and allow the administration of adequate parenteral nutrition. The difficulties encountered were related to anticoagulation, establishment of adequate vascular access, and selection of an appropriate hemofilter for the performance of the technique. Despite the application of suction-assistance, we were unable to effectively employ a prototype pediatric hemofilter to attain a level of plasma ultrafiltration consistent with the objectives of therapy. However, we were able to effectively and safely employ an adult hemofilter for these purposes; modifications were made in the adult hemofilter system before its application in the smallest pediatric patients. Our experience suggests that, even in critically ill infants, CAVH can be successfully applied as an effective renal replacement therapy. However, further experience is required before its potential impact on patient survival can be assessed.

Acute Kidney Injury↗
PubMed1985

False susceptibility of enterococci to aminoglycosides with blood-enriched Mueller-Hinton agar for disk susceptibility testing.

Disk diffusion susceptibility tests for enterococci are frequently modified by adding 5% sheep blood (SB) to Mueller-Hinton agar; the performance standards from the National Committee for Clinical Laboratory Standards sanction this addition. Susceptibility testing of aminoglycoside antibiotics is not recommended for enterococci; in actual practice, however, some laboratories do include aminoglycoside antibiotics routinely, and others may test upon request or in selected situations. In examining 50 clinical isolates of enterococci, SB-enriched Mueller-Hinton agar frequently gave enlarged zone sizes that falsely indicated susceptibility (72% for gentamicin and tobramycin), with the average increase in zone size being 6.3 and 7.6 mm, respectively. Comparison agar dilution MICs demonstrated uniform resistance, with or without added SB. The effect was shown to be caused by heme in concentrations as low as 0.03 micrograms/ml, which, when combined with aminoglycoside antibiotics, caused a synergistic growth inhibition of the enterococci, resulting in larger aminoglycoside antibiotic zones. We postulate that the heme effect is related to a catalytic cleavage of intracellular H2O2 and resultant lipid peroxidation. No other organism or antimicrobial agent tested demonstrated a similar effect, although other investigators have shown a similar phenomenon with the broad-spectrum cephalosporins. Because enterococci grow well and give accurate susceptibility results on Mueller-Hinton agar without SB supplementation and because of the spectrum of definable problems with a number of antimicrobial agents, we recommend that enterococci routinely be tested without SB.

Aminoglycosides↗
PubMed1981

Rapid screening for bacteriuria by light scatter photometry (Autobac): a collaborative study.

A total of 2,720 urine specimens from three laboratories were evaluated by Autobac (Pfizer Diagnostics) and were compared with simultaneous colony counts for evidence of bacteriuria. Of 599 specimens with a colony count of greater than or equal to 10(5) colony-forming units per ml, 93.8% were detected within 6 h. This detection rate increased to 97% of 447 positive urine specimens when only specimens from patients not on antimicrobials were evaluated. The majority (77.9%) of positive specimens were detected as early as 3 h. Those specimens with greater than or equal to 10(5) colony-forming units per ml, which were negative by Autobac at 6 h, included organisms which are frequently considered to be contaminants (diphtheroids, lactobacilli, alpha and gamma streptococci, yeasts, and Staphylococcus epidermidis), or were from patients who were being treated with antimicrobial agents. Of 2,121 urine specimens with colony counts of less than 10(5), 98.1% were correctly determined to be negative by Autobac at 3 h. This percentage decreased to 86.0 at 6 h. The majority of these false-positive specimens were those with colony counts of 10(4) to 10(5) colony-forming units per ml. There appeared to be no major difference in results from the three laboratories or among the four lots of broth used in this study.

Anti-Bacterial Agents↗
PubMed1980

Rapid semiautomated screening and processing of urine specimens.

A rapid urine culture procedure was evaluated in which positive urines were detected by using light-scatter photometry (Autobac). Specimens were analyzed at 3, 5, and 6 h. Specimens detected as positive at 3 h were then further evaluated by a direct 3-h susceptibility procedure (Autobac) and by a 4-h identification procedure (Micro-ID). Of 949 specimens, 175 had >10(5) colony-forming units per ml by colony count. Of these latter specimens, 75.4% had been detected by 3 h, and 95.4% were detected by 6 h. Of specimens positive by Autobac at 3 h, 96% (95.7%) had >10(5) colony-forming units per ml. If pure by Gram stain, those positive specimens were inoculated to direct susceptibility and identification systems. When direct Autobac susceptibilities were compared with the standard Autobac method done from the plate the following day, discrepancy rates were 1.3% very major, 2.1% major, and 7.4% total. The direct identifications were 94% (94.2%) correct when using the Micro-ID manual and a collection of octal patterns unique to this system, in which urine/broth culture inoculum was employed instead of the usual organism colony suspension. Those urine specimens negative after screening at 3 h were evaluated at 5 and 6 h, and an additional 126 specimens were detected as positive. These were then processed by routine plate inoculation, due to the limitations of the work day. By 6 h, 95.4% of specimens with >10(5) colony-forming units per ml were detected. The 4.6% false-negative results consisted of patients on antibiotics, or slowly growing bacteria suspected of being distal urethral contaminants. Thus, 83.5% of the urine cultures received by 9:00 a.m. (10.6% 3-h positives and 72.9% negative at 6 h) could be evaluated and reported within one 8-h work day.

Anti-Bacterial Agents↗
PubMedDate not supplied

Clinical implications of catheter variability on neonatal continuous arteriovenous hemofiltration.

The clinical impact of catheter diameter variability on performance of neonatal continuous arteriovenous hemofiltration (CAVH) systems was shown by demonstration of the effect of catheter inner diameter on catheter and CAVH system blood flow. Diameter of 3.5 Fr and 5 Fr catheters was determined by experimental measurement of catheter flow-pressure drop relationship with known equations for fluid flow. Physical measurements verified the accuracy of the calculated diameters. These diameters were then used in a mathematical simulation to describe blood flow through an entire neonatal CAVH system and predict clinical performance. Catheters of 5 Fr caliber had a 39% variation in diameter among manufacturers, resulting in a 370% variation in blood flows; 3.5 Fr catheters had a 29% variation in internal diameter with a corresponding blood flow variation of 290%. Computer simulation of a neonatal CAVH system revealed a maximum blood flow of 0.8-3.0 ml/min with available 5 Fr catheters. This wide variation is probably responsible for the lack of consistent results in neonatal CAVH systems to date.

Catheterization, Peripheral↗
PubMedDate not supplied

Benefit of bicarbonate dialysis during CAVHD.

The effect of bicarbonate dialysate (BD) on acid-base status in six pediatric CAVHD patients was examined during seven episodes of metabolic acidosis. When metabolic acidosis was not corrected with CAVHD, a sterile BD was substituted for either acetate- or lactate-based dialysate. Pre- and post-BD substitution levels of lactate, HCO3, PCO2, anion gap, and pH were recorded, as well as dose of intravenous (i.v.) bicarbonate. Improvements in pH and serum HCO3 were seen in all seven cases. Anion gap decreased in all but one of the patients who were switched from lactate to bicarbonate dialysate, with improvement most marked in those patients with marked elevation of the anion gap. No adverse effect on PCO2 was noted. Lactate dialysate may be less effective when serum lactate levels are high, and may contribute to further elevation of lactate levels and anion gap. These data suggest that bicarbonate dialysate may be preferable to lactate or acetate dialysate in CAVHD patients with persistent metabolic acidosis.

Acid-Base Equilibrium↗
PubMedDate not supplied

Permeability decay in CAVH hemofilters.

Change in hydraulic permeability over time was measured in four types of continuous arteriovenous hemofiltration (CAVH) hemofilters in order to characterize permeability decay and demonstrate that permeability decay occurs without membrane protein exposure. Polyamide, polysulfone, and polyacrylonitrile membrane hemofilters were placed in a gravity-driven in vitro CAVH apparatus. Distilled and deionized water or saline was used to perfuse the hemofilters. A biphasic pattern of permeability decay was seen in all hemofilter types. A large exponential decline in permeability occurred over the first 1 to 6 hours, with a more gradual decay thereafter. Of all membranes studied, polysulfone hemofilters were the most permeable upon initiation of use but showed the most pronounced early and late permeability decay. Both polyamide and polyacrylonitrile hemofilters showed little permeability decay after a brief exponential decay. These data suggest that early membrane hydraulic permeability decay may not be primarily due to membrane protein coating. Initial high permeability may place some CAVH systems at risk for hemofilter plugging.

Acrylic Resins↗