SKIN BANK ORGANIZATION

Pousa Real F.

Serv. de Cirurgia Plastica, Hospital Juan Canalejo, La Coruna, Espaha

SUMMARY. A survey is made of the organizational considerations that have to be faced in the setting-up of a skin bank, 1 hesc concern equipment, personnel, records and quality control. The methods of acquiring, processing, preserving and storing the skin are Careful records must be kept of its origin and destination. Strict application of a predetermined protocol will ensure a regular supph oi'~ iable allograft for the plastic surgeon.

The Skin Bank is a service, not a product. It is necessary to leave the processing and banking in the hands of a physician. The methodology requires a close cooperative relationship with the person in Records charge of research. The Skin Bank is a central service, available to the Plastic Surgery Department and especially to the Burns Unit.

The first report on skin freezing was by Mider and Morton in 1939. In 1945 Strumia and Hodges published the first article on the freezing of rat skins. Medawar and Wilfingcr published the first article on cryopreservation, using 14% Gycerol as an anti-freeze. Lher in 1964 established the relationship between the speed of slow freezing and quick thawing. Randolf May and De Clement published a series of publications in which they carried out studies on the viability, contamination and methodology of cryopreservation.
Laboratory. The laboratory facilities should be independent or autonomous, having lammar flow, freezing control chamber, liquid nitrogen deposits, cold-resistant packets, computer registers.
Medical StafT (part-time or pretCral-)]\, full-time), nurses and laboratory assistants. Clinical records, death certificate, donation certificate, clinical study records.

Bacteriological control, viability control, cost control, etc.

Acquisition of tissue

1. Ethical/legal consideration (' existing laws in each country)
2. Selection criteria of human allograft donors

The following documentation was utilized when available to obtain information about the donor in order to apply selection criteria:

• Medical history and physical examination White blood cell count and dif Terential
• Test for treponemal antibody
• Tests for hepatitis B surface antigen and antibody
• HLA test
• Microbiology reports and cause of'death on the death certificate.

The potential donor was excluded front use if any of the following conditions were present:

• Sepsis or bacteraemia
• Dermatitis or other infection of the skin
• Pneumonia or other respiratory infection
• Addiction to controlled substances or ()v(7idt)se from a controlled substance (due to risk of hepatitis)
• Toxic or viral hepatitis
• Antibody HLA
• Treponemal antigen or antilbody
• Malignancy (including sarcoma, carcinoma, lymphoma and leukaemia)
• Recent carcinoma chemotherapy or radiation therapy
• Autolmmune disease affecting integrity of skin
• Collagen disease aftecting integrity of skin
• Homosexuality, or heterosexual donors who have been involved in prostitution.

Processing, preservation and storage

• Timely collection of skin
• Fluids
• Skin collection rooms
• Preparation of skin
• Collection of skin
• Residual microbiological flora
• Packaging and labelling
• Storage (freezing or refrigeration)
• Distribution

Skin allograft collection should be carried out as soon as possible after the death of the donor. The body should be cooled in the morgue refrigerator if collection is to be delayed for more than four hours. Skin should be collected within 10 hours after death.

The solutions used for collection, processing and storage of the skin should be sterile and isotonic (e.g. M.E.M. 80%, F.B.S. 10%, antibiotic solutions 2%, cryo-protector agents if storage for freezing: DMSO 15%, Glycerol).
All opened bottles of solutions that might support microbiological growth must be stored below 10 *C, and discarded after 24 hours.

When feasible, skin collection should be done in a room where environmental contamination can be minimized. Access to the area should be restricted during skin collection, and other activities -in the immediate area suspended to cut down on exogenous contamination.
The work area should be cleansed with disinfectant and appropriately draped, as outlined in each skin bank's procedure protocol.

The body surface is divided into independent areas for removal and preparation; surgical removal of skin was carried out on defined areas.
Each donor body area was subsequently prepared with a detergent surgical scrub.
It was then rinsed with sterile water.
Then it was tinted with povidone-iodine and again rinsed with sterile water.
This was wiped off with sterile 10 x 10 cm fine mesh gauge sponges and 70% isopropanol which was allowed to air-dry.
After this the donor body was surgically draped exposing only the single area from which skin was to be removed.
The skin, 0.38 mm thick, was removed in 6-7 mm wide strips at least 20 cm long using an electric compressed air-driven dermatome. The dermatome blades were changed and the dermatome itself cleaned with 70% isopropanol between removals of skin from different body sites.
The harvested skin from each body area was placed into separate sterile skin sterile screw-cap plastic containers covered with 4 'C transport medium consisting of Eagle's M.E.M. balanced salt solution with 10% F.B.S or pooled human sera and 2mM fresh L-glutamine and antibiotic solution 2 % Peni.Strep-fungizone. During processing for cryopreservation, the skin was placed in 4 'C transport medium to which had been added 15% DMSO or glycerol maintained in refrigerated box at 4 'C for 1-2 hours.

One 1 CM2 full-thickness biopsy from each of the body areas was minced, and homogenized in 2 ml Of sterile 0.9% NaCI for microbiological study in the bacteriological laboratory.
If these quality control tests are done by an outside testing laboratory, the Director should satisfy himself as to the adequacy of the service.

Final packaging should be done as soon as possible after collection of skin in a specifically designated "clean area" or a laminar-flow unit equipped with HEPA filters. Sterile instruments, aseptic procedures and low temperatures should be used during all stages of processing and packaging to minimize contamination by micro-organisms and to maintain skin viability. The packaging materials should be sterile, physically. suitable for the anticipated methods of storage (e.g. Gambro), inert under the customary conditions (- 186 *Q of use, and sufficiently scalable to exclude external contamination.
As soon as possible after filling, each sealed package of skin should be labelled with a unique identification number.
The following additional information should be either on this package or on a secondary outer container or on an information sheet which would accompany the skin upon distribution:

1 . The generic name of the product
2. Instructions for thawing and use
3. Donor blood type, if known
4. Cryoprotective fluid composition, including antibiotic and other supplements
5. Name and adress of the collecting skin bank
6. Dimensions of the skin strip contained
7. Required storage temperature
8. A space for recipient identification

The allograft should be treated with the cryoprotective agent for a sufficient length of time (I to 2 hours) before freezing to ensure adequate protection. Freezing of viable skin grafts should be carried out using a system (freezing chamber TRA-13, microprocessor 8050 PPC-21 and nitrogen container Carburos Metalicos S.A. Espana) which allows a freezing ratio of -1 or -2 'C per min until it reaches -100 V. The microprocessor maintains two registers of temperature, one of the chamber and the other of cryotube control (which is the temperature of the packets of skin). Applying the freezing programme, previously obtained experimentally, the skin is stored submerged under liquid nitrogen in a liquid nitrogen refrigerator (600 1. Carburos Metalicos S.A.) to -180 V.

Split-thickness skin graft may be stored at 1 'C to 10 'C for several days following acquisition. It is sterile, if appropriate antibiotics have been added to the medium at an effective concentration. The viability of skin not used after one week cannot be assured.

Request for information. The skin bank must request the following information before release of skin for patient use:

1. Recipient patient's name
2. Patient's hospital registration number or similar identification
3. Name of requesting physician
4. Anticipated time and date of use
5. Amount of skin required
6. Part of body to be covered

Distribution documents

1. Instructions for use
2. The length of time the transportation vessel will maintain the skin in a usable condition
3. Instructions for returning unused skin to the local dispensing bank
4. The supplementary package label, if one is used
5. A hazard warning concerning the handling of skin packages and the coolant in the transport container

The skin should be maintained at or below -70 'C during transportation. Skin should be thawed using procedures which maintain suitable viability. One such procedure is rapid thawing in isotonic solution maintained at 35 'C or 37 'C. After thawing, open packages of skin may be kept at between 1 'C and 10 'C for up to 24 hours.

Results and conclusion

1. The strict application of the protocol of extraction criteria with regards to the exclusion of donors and the following of pure cryopreservation techniques allow the availability of viable allograft in the hands of the plastic surgeon which permits temporary covering of anatomic structures in the case of traumatic avulsions, especially in the treatment of large bums.
2. The cost analysis with respect to imported biomaterials is favourable, and favours and stimulates research into new technioues.

Fig. 1 Tripsinization of the epidermis Fig, 2 Dyed with TRYPAN blue. The ones dyed blue are dead cells. The cells that are not dyed are viable and the % of live cells is calculated. Fig. 3 Another technique was developed as a variant by Dr Santiago Ramon y Cajal. The grafts are dyed with TRYPAN blue. This allows an accurate count of the number of viable cells. Fig. 4 Fig. 5 Packaging of skin in a specifically designated -clear area" or a laminar-flow unit with HEPA filters. Fig. 6 Selection Criteria of Human Allograft Donors.

RÉSUMÉ. Au moment de créer une banque de la peau il faut tenir compte d'une série de considérations organisationnelles qui concernent l'équipement, le personnel, la documentation et le contrôle de la qualité. Il y a une description des méthodes pour repérer, traiter, conserver et stocker la peau. Il faut documenter attentivement son origine et sa destination. L'observation absolue d'un protocole prédeterminé garantit au chirurgien plastique une provision régulière d'allogreffe viable.