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Biomedical subjects

J P Waymack

Publications and source records attributed to J P Waymack.

86 records · Page 5Linked to original sources
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Nutritional support of the burned patient.

Burn patients develop a number of physiologic alterations among which is a markedly increased metabolic rate. Other metabolic changes include an increased rate of glucose production and utilization, a decreased rate of lipid metabolism, and an increased rate of both protein catabolism and anabolism. These alterations can effect other physiologic parameters, including immune function. They necessitate administration of large quantities of calories and protein to achieve positive nitrogen balance. The physiologic derangements leading to the hypermetabolism and the methods for supplying the nutritional needs are discussed in this review.

Animals↗
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Failure of topical steroids and vitamin E to reduce postoperative scar formation following reconstructive surgery.

One hundred fifty-nine operative procedures for postburn contractures of interdigital webs (96), the axilla (46), or the neck (17) were prospectively randomized to be treated postoperatively for four months with a topical steroid (Aristocort A), topical vitamin E, or the base cream carrier for these drugs. The nature of the medication was blinded both to the patient and to the evaluator. Patients were followed for one year. Observations were made for range of motion, scar thickness, change in graft size, and ultimate cosmetic appearance. No beneficial effect of either vitamin E or topical steroid could be demonstrated. However, adverse reactions occurred in 16.4% of patients receiving active drug, compared to 5.9% treated only with base cream. Interestingly, the grafts initially contracted and subsequently grew to be a size larger (about 20%) than the original graft by one year. It is concluded that neither topical steroid nor topical vitamin E is effective in reducing scar formation after grafting procedures for reconstruction for postburn contractures.

Administration, Topical↗
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Immunomodulators for the prevention of infections in burned guinea pigs.

Patients with thermal injury suffer a high incidence of infectious complications secondary to impaired host resistance. Nonspecific immunostimulatory agents are being tested increasingly for their ability to correct the postburn immunosuppression. By means of a burned guinea pig model, three such drugs--indomethacin, cyclophosphamide, and cimetidine--were tested for their ability to correct immunosuppression and prevent lethal infectious complications. The burned animals were challenged with Pseudomonas aeruginosa 1244 on the third postburn day. Neither indomethacin nor cimetidine altered the animals' clinical course. However cyclophosphamide, at a dosage of 2 mg/kg body weight/day, improved survival from 30% to 57% and prolonged mean survival time from 5.72 to 7.77 days. Cyclophosphamide, at a dosage of 15 mg/kg body weight/day, decreased mean survival to 3.63 days and percent survival to 0. These data show that treatment with cyclophosphamide could be beneficial in severe burn injury patients, but further work is necessary due to the dose-dependent nature of the drug.

Animals↗
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A new model for studying the development of human hypertrophic burn scar formation.

Hypertrophic scar formation remains the major problem for severely burned patients who survive their injuries. This scarring can result in both cosmetic and functional deformities. One of the major problems in dealing with this complication is the lack of an adequate animal model with which to test various possible therapeutic modalities. We describe an animal model that uses human skin applied to the backs of nude mice to investigate the problem. Immunosuppression is not necessary in this model since the nude mouse lacks a thymus gland and is therefore not able to reject the skin. With this model we have been able to achieve contracture of meshed normal human skin grafts and hypertrophic scar formation in normal human skin that was burned a month after grafting to the mouse. We have also had success in grafting human hypertrophic scars, obtained from burn patients, to the mice. This model offers unique opportunities for investigation of the cause and treatment of burn scars in humans.

Animals↗
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An evaluation of cyclophosphamide as an immunomodulator in multiple septic animal models.

Cyclophosphamide has shown promise as an immunomodulator in early animal trials involving mice and guinea pigs. To test the effectiveness of this agent in a rat model, 268 adult Lewis rats were subjected to a 30% total body surface area burn and were challenged with Pseudomonas aeruginosa 1244 administered intraperitoneally on postburn day 1 or 4, or painted on the burn wounds on postburn day 1. The animals were then followed up to determine mean survival times and survival rate percentages. Cyclophosphamide was administered to the animals on postburn days 0, 2, and 4 at a dose of either 0.5, 1.0, 5.0, or 15.0 mg/kg. A final group received saline. None of the doses significantly prolonged survival in any of the septic models, and the 15 mg/kg dose significantly shortened it in all three models. Thus, the beneficial immunomodulatory effects previously seen in mouse and guinea pig models were not seen in the rat model. Further animal investigations would appear to be indicated before human studies are undertaken.

Animals↗
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Renal vein thrombosis in burned children.

Renal vein thrombosis was noted to occur in six burned children at our institution over the last 20 years. One patient was diagnosed at post-mortem and two were diagnosed within 24 hours prior to their deaths. Three were diagnosed and successfully treated by anticoagulation with heparin. Renal vein thrombosis is a complication occurring in severely burned children that can be successfully treated if diagnosed early.

Burns↗
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Evaluation of the effect of topical steroids on human scar contracture using a nude mouse model.

Adult nude mice had 1.5 to 1.0 meshed split-thickness human skin applied to an excised area of their back. The animals were then randomized into two groups, one of which had a steroid cream applied to their graft on alternate days. The other group had no ointment applied and served as a control. The wounds were measured on a weekly basis and the rate of wound contracture was found to be identical. Topical steroids would thus appear to offer no benefit in the prevention of scar contracture.

Animals↗
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Effect of prostaglandin E in multiple experimental models. III. Effect on response to septic challenge.

Severe thermal injuries result in significant physiologic alterations. These alterations have been attributed in part to the elevated prostaglandin E levels that follow traumatic injuries. We evaluated the physiologic sequelae of elevated prostaglandin E levels by administering a long-acting prostaglandin E2 derivative, 16,16-dimethyl-prostaglandin E2 (dPGE), to rats with septic burns. The dPGE was found to increase gut translocation of bacteria. Administration of dPGE had no significant effect on resting metabolic rate. In rats with nonseptic burns the administration of dPGE resulted in increased serum levels of acute-phase proteins. In conclusion prostaglandin E may have both detrimental and beneficial effects on traumatized persons.

16,16-Dimethylprostaglandin E2↗
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Effect of ibuprofen on the postburn hypermetabolic response: a case report.

Severely burned patients exhibit a postburn hypermetabolic response which, with the most severe burns, can double the patient's metabolic rate. We report on a 54-year-old man who was on long-term ibuprofen administration for treatment of arthritis before sustaining a 38% total body surface area burn. This patient failed to demonstrate the normal hypermetabolic response. The possibility that the ibuprofen administration prevented the hypermetabolic response is discussed.

Arthritis↗
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Lack of long-term durability of cultured keratinocyte burn-wound coverage: a case report.

Cultured epithelial autografts have been advocated for permanent closure of skin surfaces after massive thermal injuries. A 10-year-old boy sustained a nearly 100% total body surface area burn (98% full-thickness) in an explosion accident. Cultured epithelial autograft was used to cover 70% of the total body surface area on postburn day 26. In spite of early success of coverage, 60% of cultured epithelial autograft areas blistered and sloughed over the ensuing weeks. Electron microscopic examination of a biopsy specimen of the healed cultured epithelial autograft (80 days after placement) revealed a lack of dermal attachments of the anchoring fibrils. Additionally, blister fluid that was taken from the bullae of the cultured epithelial autograft revealed levels of 18 ng/ml thromboxane and 24 ng/ml prostaglandin E2. These levels are significantly higher than those seen in acute burn blister fluid and indicate an ongoing inflammatory process. Cultured keratinocytes, although they provide early wound closure, may not provide adequate long-term coverage for patients with massive burns.

Biopsy↗
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Effects of fish oil on postburn metabolism and immunity.

The metabolic effects and immune responses of different levels of fish oil in enteral formulas for postburn nutritional support were studied. Thirty-seven burned guinea pigs with previously placed gastrostomy feeding tubes were given diets containing 5, 15, 30, or 50% of nonprotein calories as fish oil. These diets were isonitrogenous, isocaloric, and contained identical amounts of vitamins and minerals. After 14 days of enteral feeding, there were no significant differences in resting metabolic expenditure, serum transferrin, and albumin levels. Weight loss was significantly greater in groups receiving 30 and 50% of fish oil compared to groups which received 5 and 15% of fish oil. Carcass weights and liver weights of animals in the two groups that received diets with higher lipid content were also significantly lower. Cell-mediated immunity, macrophage bactericidal indices, and opsonic indices were not different among the groups. This study confirms that diets containing lower levels of lipids are more effective for enteral nutritional support than those containing higher levels. In contrast to linoleic acid rich lipid sources, higher levels of fish oil did not show adverse effects on immunity possibly because it contained high concentrations of omega 3 fatty acids which are not precursors of immunosuppressive prostaglandin E2.

Animals↗