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.

Cadaver skin allografts and transmission of human cytomegalovirus to burn patients.

BACKGROUND: The potential role of cadaver skin as a vehicle for CMV transmission to burn patients has never been clearly defined. We sought to determine if a cytomegalovirus (CMV)-positive cadaver allograft transmits CMV infections to CMV-seronegative burn patients. STUDY DESIGN: All patients in this study were CMV seronegative on admission. They received CMV-seronegative blood products, and cadaver allografts for temporary wound closure and management without regard to the donor's CMV serum status (positive or negative). RESULTS: Of 493 patients admitted from 1989 to 1993, 22 were CMV seronegative on admission and required cadaver allografts for their burn wounds. Five (22.7 percent) of 22 patients seroconverted during hospitalization: one of five had CMV pneumonia develop, two had CMV viruria develop, and three had persistent fever, abnormal liver enzymes, and diarrhea not ascribable to bacterial or other viral agents. CONCLUSIONS: Cytomegalovirus infections result from using CMV-seropositive cadaver allografts on seronegative burn patients.

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.

Prospective comparison of two management strategies of central venous catheters in burn patients.

OBJECTIVE: Central venous catheters (CVCs) are associated with sepsis in burn patients. This study was undertaken to compare two strategies of CVC management in patients with major burn injuries. DESIGN: Forty-two burn patients with major burn injuries were randomly assigned to undergo site change every 48 hours of the CVC or to undergo wire guide exchange of the CVC every 48 hours at the same site. MATERIALS AND METHODS: Catheter insertion site, distance from the burn wound, cultures of catheter tips, and blood cultures were obtained from all patients in a prospective manner. MEASUREMENTS AND MAIN RESULTS: There was no difference in the incidence of CVC sepsis between the two groups studied. CVCs inserted less than 5 cm from the burn wound developed bacterial contamination at an earlier time than CVCs inserted more than 5 cm from the burn wound. CONCLUSIONS: There was no advantage to changing the CVC insertion site every 48 hours. Changing the CVC using the wire guide technique did not prevent, nor predict, CVC bacterial contamination.

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.

An in vitro model for studying the effect of the subcutaneous tunnel and the skin exit site on the accuracy of central venous catheter tip cultures.

The diagnosis of central venous catheter-related sepsis depends on a positive culture obtained from the distal intravascular portion of the catheter. The effects of the subcutaneous tunnel and the skin exit site on the accuracy of cultures obtained from the catheter are unknown. We have developed an in vitro model to study the effect of these variables. By inoculating polyethylene catheters embedded in agar with Pseudomonas aeruginosa, we were able to show that: (1) capillary action occurs along catheters in an agar tunnel, (2) organisms that are growing on the distal segment (tip) of the catheter can be dislodged from the surface of the catheter when it is pulled through the agar tunnel, and (3) pulling a catheter through a contaminated area results in distal contamination.

An in vitro model for studying the effects of slime and nonslime-forming Staphylococcus epidermidis contamination of intravenous catheters.

An in vitro model was developed to study the relationship between intravenous catheters, bacteria, and the subcutaneous tunnel. Studies of both slime-forming and nonslime-forming coagulase negative Staphylococcus epidermidis show that slime formation enhances capillary action of coagulase negative S. epidermidis. This offers a possible explanation of the increased virulence associated with slime-forming coagulase negative S. epidermidis in the clinical situation.

Value of the Candida antigen assay in diagnosis of systemic candidiasis in burn patients.

The Cand-tec latex agglutination test was used to analyze 2,575 serum samples from 47 consecutive burn patients at risk for systemic candidiasis and serum samples from 24 nonhospitalized control subjects. One burn patient had systemic candidiasis documented by culture of a deep biopsy specimen. In addition, blood culture produced positive results in one patient with no other evidence of systemic candidiasis. Wound, sputum, mucous membrane, or gastrointestinal tract specimens were cultured in 25 of 47 (53%) patients with no evidence of systemic candidiasis. Surveillance cultures were negative in 19 (40%) patients and there were no signs of systemic candidial infection. The sensitivity of the Candida antigen titer was 100% at titers of greater than or equal to 1:2, greater than or equal to 1:4, greater than or equal to 1:8, and greater than or equal to 1:16. Specificity was 77% at titers of greater than or equal to 1:4, 94% at titers of greater than or equal to 1:8, and 100% at titers of greater than or equal to 1:16. The positive predictive value ranged from 6.0% at greater than or equal to 1:4 to 100% at greater than or equal to 1:16. The negative predictive value was 100% for all titer values. The Cand-tec antigen test shows poor specificity and poor positive predictive value for the detection of systemic candidiasis in burn patients.

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.

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.

Skin preservation at 4 degrees C: a species comparison.

There are numerous experimental studies in the literature regarding skin storage and preservation. These studies are difficult to interpret due to the variety of storage techniques utilized and the number of different animal species used as skin donors. This study utilized a single cold storage protocol to test the effect of species variation on skin graft viability. Donor skin was obtained from five animal species and human surgical panniculectomy specimens. The skin was stored in modified Roswell Park Memorial Institute (RPMI) 1640 tissue culture media at 4 degrees C. Stored skin was transplanted to surgically created defects on athymic (nude) mice after specific storage intervals. Ten days after transplantation, the grafts were examined by gross and microscopic techniques. The viability of mouse, rat, and dog skin was significantly different from human skin, while stored rabbit and pig skin were similar to human skin. These results demonstrate the difficulty of applying the data of skin storage studies from nonhuman species to clinical practice. The data indicate that rabbit and pig skin may be used in laboratory studies of skin preservation at 4 degrees C with a strong likelihood that the results may be of clinical relevance in predicting the behavior of human skin under similar storage conditions.

Short-term skin preservation at 4 degrees C: skin storage configuration and tissue-to-volume medium ratio.

This study was designed to examine the effect of the storage configuration of skin and the ratio of tissue-to-storage medium on the viability of skin stored under refrigeration. Human skin specimens were stored in four physical configurations in RPMI 1640 tissue culture media at 4 degrees C. Skin was transferred to surgically created defects on nude mice after specific storage intervals. Grafts were examined grossly and microscopically after ten days. In the rolled configuration, on storage day 15, the viability of the outside of the roll was significantly better than the inside (P less than 0.01). The graft viability of the outside of the skin rolls was similar for both tissue-to-media ratios as well as for both free-floating configurations (P = 0.27). These findings suggest the optimum cold storage configuration is free floating, and 300 cm2/100 mL is an appropriate skin surface area to volume media ratio. This proportion of tissue to media is in agreement with the minimum ratio currently recommended by the Skin Council of the American Association of Tissue Banks.