S. Randolph May

Skin Banking.: Part III. Cadaveric Allograft Skin Viability

The functional metabolic viability of cadaveric dermal allograft used for burn wound coverage was determined by means of the conversion of radiolabelled glucose into carbon dioxide. The viability of skin was unrelated to the age or sex of the donor, but was highly correlated with the postmortem refrigerated donor body storage time. Skin retained 55% of normal glucose metabolism after removal from donors stored for 24 hours, and 30% after 48 hours of storage. Skin maintained its postcollection functional viability above 80% of normal during the first 3 days of refrigerated storage in nutrient tissue culture medium, then steadily declined in viability to 47% by the sixth day. Skin packaged in a flat format, cryopreserved using a constant cooling rate of −1 C/min, stored in liquid nitrogen, and warmed at rates of 127 to 470 C/min retained 73.4% 3.8% of its original viability. Cryopreservation protected skin viability and allowed extended storage, while refrigeration caused skin to lose nearly two thirds of its viability in 1 week.

Skin banking methodology: An evaluation of package format, cooling and warming rates, and storage efficiency☆☆☆

The two major skin packaging formats for transplantable human skin, flat — folded and rolled — cylindrical, were evaluated with respect to the control of cooling rate, warming rate, and storage efficiency. Experiments were performed with six amounts of skin ranging from 7.6 × 20 cm (0.17 ft2) up to 7.6 × 120 cm (1.00 ft2). Contrary to previously published statements, when skin packaged in either of the two formats is cooled at an uncontrolled rate in a low temperature (−70 °C) mechanical refrigerator or dry-ice chest, the smaller skin dimensions cool too rapidly (up to −24 °C min−1), while the packets containing larger skin dimensions exhibit prolonged exothermic temperature plateaus (8–44 min), allowing the possibility of significant crystallization damage to the cells. On the other hand, controlled-rate cooling of −1 °C min−1 can be obtained using a temperature-feedback controlled-rate freezer along with a flat skin packet geometry. Much less control is obtained if a cylindrical skin packet geometry is used with a controlled-rate freezer. Skin processed in the flat format is capable of being warmed by water immersion about 10 times more quickly than equivalent amounts of skin processed in the rolled format. The longer warming times associated with the cylindrical package format (3.5–25 min, depending upon the amount of skin per packet) result from extended endothermic temperature plateaus in the subzero region, which have been shown to damage skin cells and reduce their subsequent viability. The short warming times (0.25–3.5 min) associated with the flat skin package format are devoid of such complications, since they are within the needed warming rate of 50 °C–70 °C min−1. Package geometry affects the storage requirements of transplantable skin. The flat format possesses a two- to threefold advantage in storage efficiency. Capital equipment and liquid nitrogen usage for storage is drastically decreased if a flat package format is chosen.

Development of a radiometric metabolic viability testing method for human and porcine skin.

A radiometric viability assay based upon the conversion of [14C]glucose into 14CO2 by the viable cells on the dermal side of whole skin has been developed. The assay proved to be sensitive, reproducible, and practical, and was based upon the use of a microbiological growth detection system commonly used in many hospitals and laboratories. Relatively small samples of skin (0.25–1.00 g) were used in the test, and it was found that microbiological contamination did not interfere with the assay under normal conditions. The linear proportionality of the assay with both time and amount of skin assayed precluded the difficulties of nonlinear proportionality in other systems, allowing direct comparisons to be made between skin samples of different sizes and different incubation times. The assay could also detect 14CO2 released from many radiolabeled substrates, including glucose, aspartate, glutamate, ornithine, orotic acid, and glycerol. Thus, the method could be used to test a number of cellular functions necessary for viability, including glycolysis, the functioning of the citric acid cycle and the pentose phosphate pathway, sugar and amino acid metabolism, pyrimidine biosynthesis, and cryopreservative agent metabolism. Since any of these tests could be performed in 4 hr, a viability assay based upon glycolysis alone, or in combination with any of the other tested substrates, could be carried out after allograft skin procurement before a decision needed to be made on skin cryopreservation.

Skin Banking Part I. Procurement of Transplantable Cadaveric Allograft Skin for Burn Wound Coverage

Analyses of 29.651 hospital deaths and medical examiner cases revealed that only 3.8% to 7% of cadavers were acceptable as potential skin donors. A consent rate of 32% yielded an actual skin donation rate of 1% to 2% of deaths. A survey of 20 skin procurement services and skin banks found that 868 d

Delirium in burn patients isolated in a plenum laminar air flow ventilation unit

The incidence of psychological morbidity associated with delirium was compared between burn patients isolated in a bed-size plenum laminar air flow ventilation unit (PLAFVU) and matched control burn patients treated in standard open cubicles. In patients with burn sizes of less than 60 per cent of body surface area, delirium developed in 40 per cent of the patients treated in the PLAFVU, but only in 7 per cent of the matched control patients (P = 0.04). Most of the patients with burn sizes of 60 per cent or greater exhibited delirium regardless of the method of treatment. The development of psychological morbidity was more strongly associated with treatment in the PLAFVU than with common causes such as hyponatraemia or septicaemia. The present study suggests that in the majority of burn patients, i.e. those with less than 60 per cent burns, the development of psychological morbidity may in fact be influenced by types of treatment which affect patient psychology, rather than being solely the result of physiological derangements.

Effects of early hypnosis on the cardiovascular and renal physiology of burn patients

Sixteen patients with body surface area (BSA) burns of 4 per cent to 83 per cent, with whom single hypnotherapeutic interventions were attempted 5.3 +/- 3.4 h post burn, were compared to 16 matched controls. Ten physiological parameters related to fluid volume and haemodynamics were recorded on the first two post burn days. The only significant difference discovered was elevated urine output 0-48 h postburn in successfully hypnotized patients (P = 0.01). This difference was inversely related (r = -0.94, P = 0.009) to burn size from a 10 per cent BSA burn (3.9 litres/48 h) to a 35 per cent BSA burn (1.6 litres/48 h). A statistically suggestive (P = 0.13) increase in urine output occurred in patients in whom hypnotic trance induction was unsuccessfully attempted. Patients with BSA burn sizes greater than or equal to 50 per cent, who presented with significant physiological stress and hypovolemia, were found not to be susceptible to hypnotic trance induction, and derived no physiological benefit. Attempted hypnotherapeutic intervention per se, with its psychotherapeutic component, may act only to reduce affective or psychological stress and anxiety. This psychological stress reduction apparently facilitates the loss of retained fluid in patients with small burns by a mechanism which is overwhelmed by the physiological stress of a major burn injury.

The Role of Sampling in Detection of Microbial Contamination on Cadaveric Allograft Skin used as a Biological Wound Dressing

The availability of cryopreservation and low temperature storage techniques for cadaveric allograft skin allows it to be preserved while microbial assessments are made before its use as a temporary biological dressing on burn wounds. In a 300-donor, 5-year prospective study, we tested ten skin samples from defined areas on each donor for microbiological contamination. Although the skin from 52.3 per cent of the donors possessed some detectable residual microbial contamination after surgical body preparation and skin removal, such contamination was limited to an average of 1.4 areas per body, leaving 86 per cent of all skin obtained free from detectable contamination and suitable for use as biological wound dressings. The number of skin samples tested per donor body determined the accuracy of detection of the presence of contamination. Testing one skin sample per donor body yielded a correct skin assessment 92 per cent of the time, while testing five skin samples increased the accuracy to 96 per cent, and testing ten skin samples yielded a 99.9 per cent accuracy in detection of skin contamination. Thus, it is within the ability of a skin bank to set the limits of microbiological risk to patients receiving processed cadaveric allograft skin.