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Biomedical subjects

R W Lewis

Publications and source records attributed to R W Lewis.

143 records · Page 8Linked to original sources
PubMedDate not supplied

A comparison of storage viability of nonmeshed and meshed skin at 4 degrees C.

Skin stored in nutrient medium at 4 degrees C produces acceptable short-term viability. This study compared the storage viability of nonmeshed v meshed skin stored at 4 degrees C in nutrient medium. Skin specimens from six human donors were stored for up to 35 days in RPMI 1640 tissue culture medium at 4 degrees C. Skin specimens (1 cm in diameter) were transplanted to surgically created defects on the thorax of nude mice at fixed intervals during the storage period. Gross and microscopic techniques were used to determine the graft viability at 10 days postgraft. Skin was divided into two storage groups as nonmeshed or meshed 1.5/1. The storage configuration was free-floating, 10 cm x 2 cm sheet grafts. The ratio of skin surface area to volume medium was 300 cm2/100 mL. There was no significant difference between the viability of the nonmeshed group compared to the meshed group. Prior meshing of human allograft does not adversely affect the viability of banked skin. Therefore, skin can be stored in a meshed configuration. This eliminates operating room time spent preparing allograft for application, which is cost-effective.

Animals↗
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Prospective randomized comparison of two types of pressure therapy garments.

A prospective randomized study was undertaken to compare compliance efficacy and cost of the elastic nylon pressure garment (Jobst Institute, Inc., Toledo, Ohio) with the cotton elastic pressure garment (Tubigrip, SePro Healthcare Inc., Montgomeryville, Penn.). Of 110 patients enrolled, 54 received Jobst pressure garments and 56 received Tubigrip pressure garments. Time spent in pressure-therapy garments was the same for both groups. Comparable clinical results were achieved with either Tubigrip or Jobst garments. A significantly greater percentage of patients were compliant with Tubigrip pressure-garment therapy than with Jobst pressure-garment therapy. The cost of the Tubigrip garments was significantly lower than that of Jobst garments. These data suggest that the use of elasticized cotton pressure garments results in significantly better patient compliance, a lower cost, and equal therapeutic efficacy when compared with the elasticized nylon pressure garments.

Adolescent↗
PubMedDate not supplied

A prospective safety study of femoral vein versus nonfemoral vein catheterization in patients with burns.

A prospective study was undertaken to determine the safety of femoral vein catheterization in patients with burns. Forty-two patients had a total of 275 catheterizations and were divided into two groups: group 1, femoral vein catheterization = 80 catheters and group 2, nonfemoral vein catheterization = 195 catheters (180 subclavian, 8 internal jugular, and 7 supraclavicular). All catheters were changed to new sites every 48 hours, and dressings were changed every 24 hours. Bacteriologic surveillance was accomplished by submitting the tip and subcutaneous segment of the catheter for semiquantitative cultures. Skin exit-site cultures were obtained, and blood was drawn through the catheters for fungal-isolator cultures before removal. Catheter colonization was defined as greater than or equal to 5 colony-forming units on either the subcutaneous segment or the catheter tip. Catheter-related sepsis was diagnosed when the same organism was recovered from the fungal isolator bottle and either part of the catheter and when there was no other identifiable source of sepsis. The rate of occurrence of colonized catheters was 7.5% (6 of 80) in the femoral vein catheterization group and 13.8% (27 of 195) in the nonfemoral vein catheterization group. Catheter-related sepsis occurred in 2.5% (2 of 80) of femoral and 1% (2 of 195) of nonfemoral catheters. None of these differences are statistically significant. There were no noninfectious complications from femoral vein catheterization. Two subclavian catheters had to be repositioned. This study suggests that central venous access in patients with burns can be safely employed with the use of the femoral vein.

Burns↗
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Carbon monoxide poisoning and myocardial ischemia in patients with burns.

Carbon monoxide poisoning is a well-known problem in patients with burns. A retrospective 11-year chart review was undertaken to determine the incidence of myocardial injury after carbon monoxide poisoning. Of the 1533 consecutive admissions from July 1, 1979 to June 30, 1990, 18 patients had carboxyhemoglobin levels of greater than or equal to 10% on admission. Five of these patients were found to have electrocardiographic changes that were indicative of myocardial injury. (Three also had elevated levels of creative kinase-MB). Four of five patients with electrocardiographic changes were operated on successfully with the use of perioperative invasive monitoring. None of the 18 patients had congestive heart failure or cardiac dysrhythmias during their hospital course. These data suggest that myocardial damage can result from acute carbon monoxide poisoning, and appropriate screening is indicated for the detection of such injuries.

Burns↗
PubMedDate not supplied

An experimental study to determine the effects of Dermagraft on skin graft viability in the presence of bacterial wound contamination.

Dermagrafts (Advanced Tissue Science, La Jolla, Calif.) is a possible dermal substitute currently in early stages of clinical trials. It consists of polyglycolic acid mesh impregnated with viable, human, neonatal fibroblasts. The randomized prospective study with the mouse model was undertaken to determine the effect of Dermagraft on skin graft viability in the presence of wound contamination with controlled concentrations of commonly encountered burn wound pathogens. Appropriate controlled series were run concurrently. Placement of Dermagraft, or polyglycolic acid mesh, had no significant effect on skin graft viability when compared with simple skin grafts. Controlled bacterial contamination of skin grafts with Dermagraft did not significantly change the occurrence of graft viability when compared with control groups of skin grafts with controlled bacterial contamination. These studies suggest that Dermagraft does not increase the occurrence of graft loss in the face of wound bed contamination.

Animals↗
PubMedDate not supplied

An effective method of educating junior high-aged children in fire and burn safety without disruption of the school curriculum.

A 2-hour educational seminar focusing on fire and burn safety issues was developed, presented, and evaluated by the fire department. The eighth-grade class at a local junior high school was selected for the pilot site for the seminar. A pretest and posttest were developed to measure the informational gain and retention of learned material to the students. Test results showed a statistically significant improvement in burn and fire safety scores of the tested children.

Adolescent↗
PubMedDate not supplied

Prospective, randomized study of the efficacy of pressure garment therapy in patients with burns.

A randomized, prospective study was undertaken to determine the efficacy of pressure garment therapy in patients with burns. Patients were randomly assigned to receive either pressure garment therapy or no pressure garment therapy. Patients were observed by use of the Vancouver Burn Scar Assessment Scale to assess the maturity of all involved areas. One hundred and twenty-two consecutive patients were enrolled in the study; 64 were assigned to pressure garment therapy and 58 to no pressure garment therapy. Eight of the patients receiving pressure garment therapy and nine receiving no pressure garment therapy were not involved in the follow-up. No significant differences were found between the two groups when age, body surface area burn, length of hospital stay, or time to wound maturation were compared.

Adult↗
PubMedDate not supplied

A study of functional viability and metabolic degeneration of human skin stored at 4 degrees C.

We sought to ascertain whether an in vitro assay could be as reliable as an in vivo assay in determining the viability of human skin stored at 4 degrees C. Allografts from six human donors were stored in RPMI 1640 tissue culture medium at 4 degrees C. At fixed intervals during the storage period, all skin specimens were tested concurrently by two different viability assays: (1) transplantation onto surgically created defects on nude mice, and (2) intracellular enzyme activity with use of a 4-hour semiquantitative micromethod system activity (API ZYM; Biomerieux Vitek Inc., Hazelwood, Mo.). Human graft survival on the nude mice was 100% for the first 15 days of storage, and then declined to 50% on storage day 30. The API ZYM assay showed a comparable progressive decrease in enzyme activity over skin storage time. The API ZYM assay is a simple, rapid system that produces reproducible results and is cost-effective when compared to the biologic model.

Animals↗
PubMedDate not supplied

A retrospective study of the incidence and prevalence of thermal corneal injury in patients with burns.

The clinical course of thermal corneal injuries is not well described. A review of 1750 burn admissions to a regional burn center between 1979 through 1993 was done to determine the clinical course of thermal corneal injuries. Twenty-five out of 1750 burn admissions (1%) presented with a thermal corneal injury. Corneal injuries were identified with use of a fluorescein dye and a Wood's lamp. Ophthalmologic consultation was obtained for those identified. Data were analyzed with the Fisher's exact test and the unpaired two-tailed Student's t test. Patients with thermal corneal injury did not differ demographically from other patients with burn injury. Open-flame burns were the most common cause of injury. Improvement of corneal injury occurred in all survivors who had an intact globe on initial examination. Initial visual acuity was not a good predictor of outcome, and long-term complications were uncommon.

Adolescent↗
PubMedDate not supplied

Our chemical burn experience: exposing the dangers of anhydrous ammonia.

Although chemical injuries account for only a small number of one burn unit's cases, the diversity, resulting complications, and sequelae of these burns pose special problems. We reviewed a 19-year period of the chemical burn experience of our burn unit. The population of patients with these types of burns consisted of young men (mean age: 29.8 years), the majority of whom were injured on the job. Unique to our series is the largest collection of injuries (30%) resulting from the common fertilizer anhydrous ammonia. Another population of concern, accounting for 14% of the injuries in our unit, is that of patients injured at home with routine household cleaners. Nearly one half of those patients injured at home incurred injuries that required grafting. The cornerstone of chemical burn prevention and treatment involves education regarding the caustic nature of chemicals, proper handling, adequate protection, and copious irrigation of the wound at the scene. From the analysis of our retrospective review, adequate education and treatment at the scene appear to be well implemented in the industrial and farming communities. The focus of our education efforts should be directed toward the public and emphasize the safe use of household chemicals. Finally our review illuminated the potential benefit of immediate excision and grafting for decreasing the length of stay, complications, and loss of productivity.

Adult↗
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Intraurethral and topical agents.

In early 1997, the FDA approved a transurethral delivery system for a urethral suppository containing alprostadil (PGE(1)), manufactured by Vivus and called the MUSE system. Pharmacokinetic studies showed rapid absorption from the urethra (80%) in the first 10 minutes after an intraurethral dose. 873 patients tried home use of alprostadil or blinded placebos. 64.9% of the patients on alprostadil reported intercourse compared to only 18.6% of the placebo group. Successful use of MUSE at home seemed to be equal in all categories of impotence. The consistency of response increased slightly over a period of 3 months. Penile pain occurred in 32.1% of patients receiving the active ingredient (10.8% of all applications). With the MUSE system, there was minor urethral trauma in 5.1% of the patients. A small subset of patients who used MUSE reported that previous intracavernosal injection therapy was not effective. Of these, 58% reported erections sufficient for intercourse after MUSE introduction. Recently, further efficacy studies were performed in a FDA trial of the combination of the MUSE system with the veno-occlusive band (Actis). Topical medications have been anecdotally reported and do not produce spectacular results. These include organic nitrates and nitrites, minoxidil, papaverine and PGE(1) or PGE2.

Journal Article↗
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Local microwave hyperthermia as a treatment alternative for benign prostatic hyperplasia.

It appears that the technology for local microwave application of heat to the prostate for the management of benign prostatic hyperplasia has arrived. There are a number of issues to be resolved in the coming years that will determine the role this modality will play in the overall management of men with benign prostatic hyperplasia. These issues include: transurethral versus transrectal route, hyperthermia (42 degrees C to 44 degrees C) versus thermotherapy (greater than 45 degrees C), and a proper assessment as to whether the technique is really efficacious, given the known placebo response in all studies currently available. The results with the transrectal route appear to improve patients' symptoms objectively and subjectively, without causing irreversible tissue effects. Thus, its action has been likened to alpha blockade. But, it appears that the transrectal approach is relatively inefficient because of a significant loss in microwave power with rectal cooling. A probe placed transurethrally can accurately and easily deliver the intended power to the center of the prostate, where theoretically it has its greatest effect on both the dynamic and static components of outlet obstruction. Currently, the transurethral devices described by Sapozink and Devonec will produce histologic necrosis. The theoretical value of combining urethral heating with cooling is that it will allow treatments of greater power deeper in the prostate adenoma, but the greatest advantage over transurethral heating without cooling may be in the ability to effect a response in a single session. Finally, the placebo response is a well known phenomenon seen in all drug trials conducted for the management of benign prostatic hyperplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
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A high efficiency membrane separator for donor plasmapheresis.

The shortfall in human plasma for therapeutic use can be met satisfactorily only by donor plasmapheresis. Membrane blood plasma separators of conventional design work poorly at low rates of blood flow, and performance decreases rapidly as the membrane becomes fouled. To overcome these problems, membrane separators have been developed that employ vortex mixing to prevent blood cells obstructing the membrane pores. These separators consist of a single blood channel 160 mm long by 62.5 mm wide. The two membranes that act as boundaries for the blood channel are thermoformed to provide a closely packed array of outward facing dimples. The membranes are seated on rigid support plates, and flexible diaphragms are attached to each end of the blood channel. The diaphragms were oscillated in antiphase at 3 to 6 Hz, with a stroke volume of 2.8 ml. In 24 clinical trials, mean plasma filtration rate was 18 ml/min at a blood inlet flow of 48 ml/min. In 10 experiments using bovine blood, mean plasma filtration rate was 35 ml/min at a blood inlet flow of 90 ml/min. Little reduction in performance was observed over 80 min. The membrane area was 200 sq cm, which gave a filtration velocity of 1.75 L/min/m2, higher by a factor of five than is reported for hollow fiber or flat plate designs.

Animals↗
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Separation of plasma from whole blood by membrane filtration in oscillatory flows.

This paper describes the performance of a microfiltration plasmapheresis unit operating with reversing oscillatory flows. The device consists of a flat channel duct between cellulose nitrate membranes and was used to extract plasma from anticoagulated fresh whole bovine blood. Measurements were made of plasma flux, haematocrit concentration, haemolysis and protein sieving coefficients. The effects on plasma flux are reported for alterations in the stroke and frequency of flow pulsations, transmembrane pressure, membrane properties and blood throughput. It was found that the imposition of oscillatory flows enhanced the plasma extraction rate by a factor of 3, producing about 0.9 litre/min/m2 membrane.

Animals↗
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Androgenic maintenance of the rat erectile response via a non-nitric-oxide-dependent pathway.

Prior studies have demonstrated that the erectile response in the rat penis is androgen dependent and is mediated by nitric oxide (NO), the neurotransmitter synthesized by the enzyme nitric oxide synthase (NOS). The present studies used L-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS, to determine if androgens also regulate alternative pathways leading to the erectile response but not mediated by NO. Castrated rats that were treated with L-NAME (L-NAME CASTRATE) exhibited little or no increase in intracavernosal pressure in response to stimulation of the major pelvic ganglion. This ganglion controls blood flow into the penis and, when stimulated, normally leads to erection. However, when castrated animals were treated with testosterone along with L-NAME (L-NAME TESTO), the animals responded to the ganglionic stimulation with increased intracavernosal pressure. This finding suggests that there are other androgen-dependent pathways that lead to penile erection but are not mediated by NO. Erection occurred in both L-NAME CASTRATE and L-NAME TESTO rats in response to intracavernosal injection of sodium nitroprusside (an NO donor drug), proving that the NO responsive mechanisms were unaffected by the inhibition of NOS activity. To investigate further the nature of this NO independent pathway, L-NAME CASTRATE and L-NAME TESTO rats were treated with either zaprinast (a specific phosphodiesterase 5 inhibitor), which would block the breakdown of cGMP to 5'GMP, or methylene blue (an inhibitor of guanylate cyclase) to prevent the synthesis of cGMP. Zaprinast treatment led to increased erectile response in L-NAME TESTO rats but not in L-NAME CASTRATE rats, demonstrating that androgen-sensitive alternative pathways increased guanylate cyclase activity. Methylene blue inhibited the erectile response in all treatment groups, showing that cyclic GMP is critical to the NO-independent pathway as well as the NO-dependent pathway. Taken together, these results support the hypothesis that androgens maintain the erectile response by alternate pathways, including one that is independent of NO but involves the synthesis of cyclic GMP.

Androgens↗
PubMedDate not supplied

The loss of alpha-adrenergic effect during the erectile response in the long-term diabetic rat.

The present study was designed to investigate the effect of long-term, streptozotocin-induced diabetes on the erectile response in the laboratory rat. Mean arterial blood pressure (MAP) and intracavernosal blood pressure within the erectile tissue (CCP) were continuously monitored during erection elicited by stimulation of the autonomic innervation of the penis. MAP and CCP were also measured during administration of two drugs: nitroglycerin, a nitric oxide donor drug and phenylephrine, an alpha-adrenergic agonist. The results of these studies show that during graded electrical stimulation of the ganglion, the overall magnitude of the erectile response was greater in the diabetic rats than in untreated control animals. Neither diabetic nor control animals responded significantly to infusion of nitroglycerin. However, diabetic rats and control rats responded very differently to administration of phenylephrine; in the control rats, this alpha agonist caused a sharp decline in CCP as the cavernosal vessels constricted in response to the drug. The same dose of phenylephrine had no discernible effect on CCP in the diabetic animals. This loss of alpha responsiveness may be confined to the penile circulation because MAP was elevated to approximately the same extent in both groups. Taken together, these results show that long-term diabetes leads to a failure of alpha-adrenergic responsiveness in the cavernosal circulation. The greater erectile response to ganglionic stimulation in the diabetic animals is likely due to the loss of response to endogenous norepinephrine.

Adrenergic alpha-Agonists↗