Natural Craft Materials

Properties of natural autografts and some allografts include a decrease in the quantity of bacteria in the wetted surface of

FIG. 6. Repeating disaccharide of chondroitin 6-sulfate.

the wound, a decrease in the loss of fluids and proteins, a limiting effect upon wound contracture when the dermal layer is included in the graft, a decrease in pain in second-degree burns, and an increase in the neovascularization of the wound area.

Major disadvantages of natural graft materials include a lack of autograft in severely burned patients, difficulty with storage of allograft material (typically 7—10 days when stored at 4°C and longer at —70°C), antigenicity, leading to the need for eventual replacement, and the potential to transmit diseases. Donors are scarce and must be carefully screened for transmissible diseases (including hepatitis and AIDS) and neoplasms before transplantation. Fresh-frozen and lyophilized grafts (rapidly freeze-drying the samples) prolong the shelf life of the tissues. However, if the samples are thicker than 0.38 mm, there is a propensity for the epidermal and dermal layers to separate in the lyophilized samples. Both techniques offer a lower graft survival than fresh graft material, and are less able to suppress microbial invasion.

Xenografts, especially porcine-derived commercial preparations, are used as a temporary wound closure material. As with the frozen and lyophilized allografts, porcine grafts at best only adhere to the wound bed with a fibrinous interaction but this can temporarily close a wound. The grafting success rate is lower than with fresh allograft and sterility of the xenografts must be ensured to protect the already immunocompromised burn patients. The porcine grafts must be immobilized for several days to allow bonding of the graft to the wound bed by growth of fibroblasts into the dermal layer of the graft. As with any skin replacement procedure, the wound bed must be debrided thoroughly and be free of significant bacterial contamination. Because porcine grafts will ultimately be rejected, they must be removed and replaced with autograft material.

Amnion has been tried as a temporary natural wound dressing, but again the source must be carefully screened for disease. Amnion is freely available from the delivery of babies, and is relatively inexpensive to prepare. The adherence of amnion to the wound is less successful than with dermal wound dressings and it is likely that a true incorporation of the material into the wound bed never occurs. The amnion must also be covered with a secondary occlusive dressing to prevent sloughing. It has been reported that the amnion increases the granulation of the wound bed, which makes subsequent skin graft survival more likely but ultimately also results in more scarring.

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