Abstracts 71

ANIMAL STUDIES Changes in body composition Direct measurements of body composition have been made in 80 rats with bums covering 25 per cent of the body surface. The observed losses in body weight were directly related to the animals energy deficit resulting from a combination of injury, food intake and rate of wound healing. Body fat was the most labile source of tissue energy, decreasing to a minimum of about 30 g per kg body weight. The relationships between water and fat and water and protein seen in normal animals were not significantly different in the burned animals.

Al Shamma G. A., Gall C. C., Baird T. B. et al. (1979) Changes in body composition after thermal injury in the rat. Br. J. Nutr. 42,367.

Topical chemotherapy of sepsis Rats with full-thickness bums covering 18-22 per cent of the body surface were used in a standardized model of wound sepsis. A regimen of once a day application of Silvadene has been found to be more effective than treatment with Sulphamylon or cerium Silvadene. Delaying treatment following infection resulted in decreased survival. Possible reasons for the altered mortality are the once-daily application of the anti- microbial cream, or perhaps a change in sensitivity between the drugs and the strain of Pseudomonas aeruginosa over time.

Salisbury R. E., Bevin A. G., Steinkraus G. E. et al. (I 980) Bum wound sepsis: effect of delayed treatment with topical chemotherapy on survival. J. Trauma 20, 120.

Smoke and pulmonary surfactant A standard dose of smoke from wood and kerosene was delivered at 37 “C to mongrel dogs to define the primary effects of acute smoke inhalation without the variables of infection, bums or fluid resuscitation. Measurements were made of blood gases, carboxy- haemoglobin, pulmonary and systemic haemodyna- mics, respiratory mechanics, surface tension area curves as an indication of surfactant activity and in vivo photomicroscopy. The FIo2 of the smoke was 17 volumes per cent and the carbon monoxide content I7 000 ppm.

Immediately following smoke exposure dense, non- segmental atelectasis developed. Haemodynamic changes were insignificant but the PaO, fell to 49 mmHg and the right to left shunt rose from 5 to 41 per cent. Surfactant reduction was significant enough to increase the minimum surface tension from 7 to 22 dynes per cm. This surfactant loss may explain the observed atelectasis and the marked instability of subpleural alveolar walls. As the clinical correlation between surfactant loss and smoke inhalation is good it may explain why victims of smoke inhalation are so vulnerable to fluid administration if they have bums as well.

Nieman G. F., Clark W. R., Wax S. D. et al. (I 980) The effect of smoke inhalation on pulmonary surfac- tant. Ann. Surg. 191, 171.

Healing of hot and cold burns Full-thickness skin loss injury was produced in rats by contact with a metal plate at 100 “C for 20 s or at - 196 “C for 30 s. Durina the nrocesses of healing. contraction did not occur in 3i) wounds caused by freezing, whereas 30 wounds caused by heat contracted to less than one-third of the original size by 2 1 d after injury. If the central tissue in a freeze-produced wound was excised contraction occurred and proceeded at the same rate as in an open wound. Histologically the degree of initial tissue destruction by the two types of injury was similar. The bum wound contained only half the amount of collagen found in the freeze- produced wound. There was a greater and more rapid replacement of collagen in the bum wounds. With both injuries the highest concentration of collagen was found on day 15, and had returned to normal by day 28.

The bum wound contained 3 times the amount of collagen found in normal skin, while the freeze- produced wound contained only 13 times the amount in normal skin. Contraction does not seem to occur in the healing of the freeze-injured tissue because the slow removal and replacement of the residual matrix prevents contraction.

Li A. K. C., Ehrlich H. P., Trelstad R. L. et al. C 1980) Differences in healine of skin wounds caused bv bum and freeze injuries. An;. Surg. 191,244. ’ Skin excision with an argon laser The haemostatic capabilities of argon laser light have been combined with the mechanical advantages of a sharpened quartz blade using fibre optics. Using this new laser-assisted scalpel, a series of symmetrical skin excisions have been made in 20-30 kg pigs and the results compared with contralateral excisions made using electrocautery. The laser scalpel was superior in its haemostatic properties and there was no statisti- cally significant difference in surgical speed. Take of split thickness skin grafts was 90 per cent in tissue beds excised with either the laser or the electrosurgical device. Histological sections showed less tissue damage with the laser-assisted scalpel than with electrocautery.

Heimbach D. M., Neal G. D., Doty J. L. et al. (I 980) The use of the argon-laser assisted quartz scalpel for bum wound excision to fascia. J. Trauma 20. 123.

Liquid propane cold injury Accidental contact with liquid propane without ignition produced a cold injury covering 36 per cent of the body surface. The cutaneous appearance was that of a flame bum but underlying deep tissue damage was also present. Acute vascular compromise and progres- sive wound sepsis were complications which required surgical intervention.

A liquid propane cold injury was induced in an animal model and it was shown that the skin tempera- ture fell to -60 ‘C within 5 s and that the muscle tissue temperature had fallen to -26 “C after 60 s exposure.

Hicks L. M., Hunt J. L. and Baxter C. R. (1979) Liquid propane cold injury: a clinicopathologic and experimental study. J. Trauma 19,701.