Embedded Files
Aurora Navarro Martínez-Cantullera
Rafael I. Barraquer
THE DONATION OF ORGANS AND TISSUES
Beyond the histological composition of the cornea – actually multi-tissue, as it consists of epithelium, stroma and endothelium, corneal transplants are considered legal tissue transplantation. Except for rare cases of autografts or living donors (eyes enucleated for therapeutic reasons), corneal transplants require the altruistic gesture of a person or family, who make the decision to make the donation at the time of death. Although the general population better knows organ donation, a much larger number of donors and tissue transplants are produced. In particular, eye donation and corneal transplants are among the most frequent.
The donation of organs and tissues in the world
The differences in the rates of donation and transplantation of organs and tissues in the world are very marked. According to the Global Observatory on Donation and Transplantation (http://www.transplant-observatory.org), in the world more than 100,000 patients are transplanted with an organ each year, although this is only covering 10% of the needs. In some countries such as Spain, Croatia and Malta, the donation of organs of deceased persons exceeds 30 donors per million in the population (pmp), while in others such as Japan, Russia or Mexico it is almost non-existent (<5 pmp, Figure 1)1.
Figure 1: Frequencies of cadaver organ donation in the world during 2013. Available at: http: www.irodat.org.
Inadequate donations result in long waiting lists and many patients dying before they can be transplanted. Therefore, in 2011, the World Health Assembly approved Resolution WHA 63.22, which urges member states to strengthen authorities and/or national and multinational organizations to organize, supervise and coordinate the activities of donation and transplant, with special attention to maximize the donation from cadavers2.
The donation of tissues in Spain
Spain is a world leader in organ and tissue donation and transplants. During 2014 there were 2,799 eye donors in Spain, that is, 60.2 pmp. Of these, 5,575 corneas were obtained, and 3,539 transplants were performed (76.1 pmp). In the same year, the total donation of corpse organs was 35.9 pmp and 4,247 (90.2 pmp) were transplanted, including live donors (Figure 2)3. A certain ignorance of the importance of tissue transplants, may explain that the rate of family refusal to donate reaches 40% in Spain, while it is only 18% for organs.
Figure 2: Rates per million population of the total number of transplant patients in European countries in 2014 (including living and post-mortem donors) (1).
The Spanish donation model has made this a normal procedure, well accepted among the general population and by the health system. It consists of a series of coordinated actions that make this reality possible4:
- Systematic organization of the donation process at the national, regional and hospital levels.
- Development and strengthening of the figure of the transplant coordinator, a key professional for the success of donations.
- Quality control program in donations.
- Training and qualification of the personnel involved in the process.
- Communication of the process transparent and always available.
Types of tissue donors
A cadaver donor is defined as a deceased person, in brain death or asystole, who having not manifested in life his or her opposition, donates altruistically, tissues and cells destined for its application in the human beings5. There are two categories of tissue donors:
- Cornea donors: By donating only this tissue, the selection criteria are less strict, which results in a greater volume of donations. They are not exclusive, for example, a history of oncological disease (except malignancy in blood, lymph and retinoblastoma)6 or active general infection. There is also no absolute maximum age limit, since good results have been documented even with donors of very advanced ages7,8.
- Multi-tissue donors: Those who donate at least two types of tissues of different origin. The exclusion criteria are stricter (e.g., maximum age of 55 years for the donation of arteries), and no history of neoplasia or active infection at the time of death is accepted. This reduces the frequency of effective donations.
Tissue donation models
Tissue donation often occurs in the hospital setting, in the context of a multiple organ donation. In the case of the corneas, a part of the population has been affiliated to an Eye Bank, expressing in life their willingness to make the donation upon death. The detection of possible corneal donors also occurs in funeral homes, nursing homes and private homes. In any case, a trained and authorized medical or technical team, carries out the extraction.
Family consent to donation
The tissue will be obtained after certification of the death and eventual practice of judicial proceedings. According to Law 41/2002, the obtaining of tissues and cells of deceased persons may be carried out provided that they have not left an express record of their opposition, which may refer to all types of organs or only to some of them and will be respected.
The request for donation to family members is a critical moment. Professionals with sufficient training and experience should do them in general, the transplant coordinators. If the family does not know the express opposition of the deceased, once the donation has been accepted, the medical history should be reviewed, and a social risk survey carried out. For this it is preferable to resort to the relative or person closest to the donor capable of answering intimate questions such as drug use, travel and sexual relations, always making clear the confidentiality and the utility of the donation to achieve the good that is involved in carrying out the transplants.
EVALUATION OF THE POTENTIAL DONOR OF CORNEAS
All potential corneal donors must go through an evaluation and selection process that excludes possible contraindications or risks for the recipient, in particular the transmission of diseases. To ensure that these tasks are carried out systematically, work protocols and appropriate controls must be established.
Cause of death
It is the first step to exclude possible contraindications or risks of disease transmission to the recipient. The cause of death must be known at the time of extraction or at least organize the appropriate actions to clarify it later. This may require histopathological studies of some organs or tissues, or even an autopsy.
Medical history
The clinical history of the potential donor is a source of essential information. In the hospital environment, we must find out the reason for admission, clinical evolution, medication, and even review the annotations in the history, laboratory and imaging tests that have been done and if the patient has received any transfusions. For a better understanding of the history, it is advisable to talk with the doctor who has treated the patient. The following are considered absolute contraindications for tissue donation:
- HIV and hepatitis: Clinical, laboratory or history evidence of AIDS or HIV infection, of acute or chronic hepatitis B (except in persons with proven immunity), of hepatitis C and HLTV I/II, as well as risk of transmission or evidence of risk factors for these infections.
- Systemic infection not controlled at the time of donation (sepsis, rabies, meningitis): In the case of corneas, bacterial septicemia is not a contraindication, as they are an avascular tissue and because samples from the donor can be cultured during extraction and preservation before being released for transplantation9.
- Malignant diseases: The European Tissue and Cells Directive10 considers exclusion criteria for tissue donation to be the history or presence of neoplasms, except primary basal cell carcinoma, carcinoma in situ of the cervix and primary tumors of the central nervous system. This does not apply to corneal donors, except in the case of hematological malignancy (leukemia, lymphoma, multiple myeloma), retinoblastoma and malignant tumors or metastases in the anterior segment. However, the general contraindication does affect the use of vascularized ocular tissues such as the limbus or the sclera.
- Diseases caused by prions: This risk applies to patients diagnosed with Creutzfeldt-Jakob disease or with a family history of the disease (of a non-iatrogenic cause). Given a history of progressive dementia or rapid neurodegenerative disease, only cases with a well-known and non-transmittable primary cause such as dementia of vascular origin would be admissible. It is also recommended to exclude recipients of human pituitary gland extracts, dura mater, cornea or sclera transplants.
- Recipients of xenotransplantation: in case this includes living cells.
- Recent vaccination (<1 month) with live attenuated virus that can be transmitted (according to blood donation criteria).
- Toxic substances: Intake or exposure to substances (cyanide, lead, mercury, gold) that may affect tissue quality or be transmitted to the recipient at a dangerous dose.
- Subjects who have been excluded from blood donation due to an unknown cause.
Other relevant information that may or may not contraindicate the donation
- Autoimmune diseases: they can be contraindications for the donation of corneas if the disease damages the tissue to be extracted or if they are treated with immunosuppressants at high doses, since this can alter the results of serologies.
- History of infectious diseases such as babesiosis, bartonellosis, borreliosis, brucellosis, chlamydiosis, rheumatic fever, Q fever, leishmaniasis, leprosy, melioidosis, osteomyelitis, rickettsiosis, tuberculosis and trypanosomiasis, can be contraindications if there is no assurance that the donor is free from the disease, with the aforementioned caveats in the case of bacterial septicemia.
- Long hospital stay: assess the possibility of having acquired a nosocomial infection, especially after prolonged mechanical ventilation.
- Previous surgery that may affect the quality of the corneal tissue (see below).
Social history and assessment of risk attitudes
Social history should include the following issues that may or may not be a cause of contraindication:
- Use of drugs parenterally, in particular in recent months. In case of previous history, caution should be applied to allegations of abstinence.
- In the case of tattoos, piercings and/or acupuncture in the 4 months prior to death, their conditions of execution must be verified (single-use sterile materials, change of ink between clients, etc.).
- Sexually transmitted diseases in the previous 12 months or risk of having acquired them, including practices such as sexual promiscuity or prostitution, or having maintained intercourse with people carrying HIV or HTLV I/II viruses.
- Evaluate the risks of exposure to transmittable diseases for reasons of residence (living with an HBV or HCV carrier or having been in prison for the past 12 months) or trips to countries at risk (in particular malaria, yellow fever, Dengue, Chagas disease, tuberculosis, West Nile virus, Q fever and HIV-1 group O)11.
Specific contraindications to corneal donation
The age of the cornea donor is not in itself a contraindication to the donation, since the quality of the tissue is subjected to detailed study before releasing it11. Although the endothelial population in general decreases with age, its great variability among individuals explains that corneas of more than 100 years have been successfully transplanted. The corneas of infants (<1 year) have often been excluded because of their high elasticity, although the relevance of this may depend on the type of transplant. Specific contraindications to corneal donation include13:
- Active corneal infections, as well as a history of herpetic keratitis.
- Congenital or acquired corneal pathologies such as leukomas, keratoconus, etc., or previous corneal surgery (radial or photo-refractive keratotomy, LASIK) that impair the result of the graft. Since this will depend on the type of keratoplasty, some may be acceptable for certain grafts (e.g., endothelium).
- Active intraocular inflammation (uveitis, endophthalmitis) that negatively affects graft quality.
- Malignant tumors of the eye that may affect the graft, generally includes retinoblastoma and those of the anterior segment, whether primary or metastatic.
A history of cataract surgery, with or without intraocular lens implant, should not be considered a contraindication before studying the corneal endothelium. And in any case a poor endothelium does not preclude use in anterior lamellar keratoplasty.
PHYSICAL AND LABORATORY EXAMS
A physical examination of the donor should always be performed to detect any possible transmittable diseases and corroborate the medical history. This should be documented both in case of a finding and in its absence. First of all, it must be verified that the name of the donor in the consent coincides with his identification (label, bracelet, etc.).
Physical exploration
The donor's sex, race, weight and height, body hygiene, malnutrition or deformities must be checked. Discard genital lesions, large lymph nodes, tattoos or piercings, acupuncture or non-medical injection marks, white patches in the mouth, skin lesions suspected of malignancy, petechiae, scabs, ulcers, herpes, trauma, fractures, lacerations or abrasions, and jaundice. In the case of autopsy, it must be checked if it has been partial or complete or if it will be performed after the tissue donation.
Obtaining blood samples
According to the method to perform the serologies, plasma or serum may be used, in no case other bodily fluids. The quality of blood samples for serologies depends on several factors:
- Time after the asystole: as soon as possible to avoid hemolysis and false positive results14. In general, a maximum of 24 hours is allowed.
- Hemodilution: if the donor has received transfusions of blood, plasma, colloids and/or crystalloids, these can invalidate if hemodilution is >50%. In this case, pre-transfusion samples should be obtained, up to 7 days pre-mortem13.
- Conditions of preservation of the sample before performing the tests, such as centrifugation, refrigeration, etc.
Serological tests to be performed in the cornea donor
Serologic screening must be performed in accredited laboratories for the activities that the law determines and authorized by the competent authority. It is obligatory to keep a blood sample from the donor, facing an eventual need to repeat the tests, at least 10 years until the last tissue of the donor has been transplanted. The battery of tests required for corneal donors includes:
- Negativity of antibodies against human immunodeficiency virus (HIV1, HIV2), hepatitis C (anti-HCV), and hepatitis B virus surface antigen (HBsAg) should always be tested.
- If antibodies against hepatitis B 'core' (HB-cAc IgG and IgM) are positive in the presence of negative HBsAg, a re-evaluation of the risk and new tests should be carried out (table 1).
- Syphilis: a specific or non-specific treponemal test may be performed. If it is positive, a new risk analysis of the donor must be carried out.
- When the donor comes from areas of high prevalence of some transmittable diseases, additional tests may be necessary: antibodies HTLV I-II15, malaria, anti-Trypanosoma cruzii (Chagas disease) (Figure 3).
Figure 3: World distribution of Chagas disease in 2011. Estimation of infected population in 2009. Available at: http://thehealthcoach1.com/wp-content/ uploads / 2012/06 / MapChagasJun09_large.jpg
- The techniques to detect transmissibility markers currently have high sensitivity, specificity and predictive values. However, there is still the rare possibility of false negatives obtained in the window period. To minimize this risk, in addition to the study of medical and social histories, PCR techniques for HIV, hepatitis B and C are recommended.
- The usefulness of studying human leukocyte antigens (HLA) in corneal donors, in order to find the best compatibility with the recipient, remains a controversial issue19. The lower risk of rejection with lamellar transplant techniques further reduces the number of cases in which such a study could be useful18.
EXTRACTION OF THE CORNEAL TISSUE
Obtaining corneal tissue should be done as soon as possible, usually within 24 hours after death. This allows preventing post-mortem infections and preserving the characteristics of the cornea. It is important to keep the eyelids closed from asystole to extraction. A team of specialists in obtaining corneal tissue must form the extracting staff.
Place and materials for obtaining the cornea
The extraction of the tissues must take place in appropriate facilities, by means of procedures that minimize the possibility of contamination of the same. Unlike what is required for other tissues, the extraction of those of ocular origin does not require the asepsis levels of an operating room. In these cases (e.g., morgue, funerary home, home), it is necessary to create a space to limit possible environmental contamination. The clothing must be appropriate, with a mask, hat, gloves and sterile gown. The instruments must be sterile and of good quality or of a single use, validated to obtain corneas. All this must be recorded in the donor's documentation.
Types and phases of extraction
There are two types of obtaining: the extraction of the entire eyeball and that of an isolated corneoscleral segment or cap. The first may seem more cumbersome, but technically it is simpler since it does not require maneuvers near delicate tissues such as the corneal endothelium. In addition, keeping the eyeball intact makes internal contamination more difficult. Upon reaching the eye bank facility it is possible to perform controlled decontamination of the outside of the globe and the separation of the corneoscleral tissue in conditions of greater safety and sterility. In any case, there are a series of common steps:
1. Check the donor's identity and family consent.
2. Perform a macroscopic examination of the globe and cornea to rule out possible alterations.
3. In congestive donors it is advisable to elevate the head a little to avoid orbital bleeding.
4. Surgical hand washing.
5. Establish a sterile field to place the instruments.
6. Clean the extraction area with povidone iodine at 5% and work area with antiseptic solutions. Excess povidone should be irrigated, since it is toxic to the corneal endothelium and keratocytes16.
7. Instill a broad-spectrum antibiotic solution on the corneal surface.
8. Separate the eyelids with a speculum, taking care not to injure the epithelial surface.
9. Perform a 360° peritomy around the limbus, with a forceps and scissors. To dispose of limbal cells it is advisable to leave a certain margin of conjunctiva. Tractions that can cause creases in the cornea should be avoided.
The extraction of the eyeball is continued with (Figure 4):
Figure 4: Phases of the extraction technique of the ocular globe of the corpse.
1. Isolate with the strabismus hook the four straight and oblique muscles, and section them close to their insertion.
2. Insert the enucleation spoon into the orbit on the medial side while applying gentle upward pressure.
3. Insert the optic nerve scissors ajar on the side, behind the spoon.
4. Section the optic nerve trying to leave at least 5 mm of it attached to the eyeball.
5. At all times avoid globe compressions or damage of the corneal surface.
6. Place the globe in a moist chamber (sterile vial with a tight seal and gauze at the bottom) with the cornea facing up.
7. Instill a few drops of saline or antibiotic eyedrops. This will wet the gauze at the bottom and help keep the environment humid.
The extraction of the isolated corneoscleral segment is continued with:
1. Mark with a 17 mm trephine the circumference of the segment to be extracted.
2. Deepen the trephination with a scalpel until it penetrates at some point in the suprachoroidal space.
3. Complete the section of the sclera with scissors following the groove of the partial trepanation.
4. Gently lift the sclera until the root of the iris is progressively dislodged. Care must be taken that the iris never comes into contact with the endothelium.
5. Place the segment or corneoscleral cap in the preservation medium for transport.
Finally, we proceed, in both cases, to cosmetic reconstruction. In case of eyeball extraction, a plastic or cotton ball is used. If the extraction is only corneoscleral, a cap-shaped prosthesis is used. If necessary, the eyelids can be closed with suture or adhesive.
PACKAGING, CODING AND TRANSPORT OF THE TISSUE
In order for the eyeballs or corneoscleral segments to reach the EB or tissue bank in the best conditions, it is important that the transport be as fast as possible and with a temperature maintained between + 2°C and +8 °C. For this the packaging must be validated to maintain the adequate temperature in front of different meteorological situations.
The coding of the extracted tissue is important to allow donor-recipient traceability at all times. It must be done at the time of extraction, following the rules of the European Commission17. This includes a Unique European Code that must contain the information of the identification, donation and product sequences. Properly performing all the steps of obtaining the tissue is a fundamental aspect to ensure the success of corneal transplants.
BIBLIOGRAPHY
1. Newsletter transplant. International figures on donation and transplantation 2013. Vol. 19. Nº 1. Sep. 2014. Available at: http://www.ont.es/publicaciones/Documents/NEWSLETTER%202014.pdf.
2. Human organ and tissue transplantation. Sixty-third World Health Assembly. WHA63.22. Agenda item 11.21, 21 May 2010. Available at: http://apps.who.int/gb/ebwha/pdf_files/WHA63/A63_R22-en.pdf.
3. Newsletter transplant. International figures on donation and transplantation 2014. EDQM Vol. 20, 2015. Available at: http://www.ont.es/publicaciones/Documents/NEWSLETTER_2015_CE.pdf.
4. Matesanz R, Domínguez-Gil B, Coll E, de la Rosa G, Marazuela R. Spanish experience as a leading country: what kind of measures were taken? Organización Nacional de Trasplantes. Madrid. Spain. Transplant International ISSN 0934-0874.
5. Navarro A. Deceased donors of tissue. George Galea. Essentials of Tissue Banking. Edinburgh: Springer; 2010 I.p. 23-40.
6. López-Navidad A, Soler N, Caballero F, Lerma E, Gris O. Corneal transplantations from donors with cancer. Transplantation. 2007; 83: 1345-1350.
7. Eric Abdullayev, MD, MBA, CEBT Study. Corneas from older donors suitable for transplantation. VII World Cornea Congress. San Diego. 2015
8. Visby E, Hjortdal J, Nielsen K. Evaluation of grafted patients with donor corneas that today are more than 100 years old. Acta Ophthalmol. 2014; 92: 478-481.
9. Chapter 15, Page 159 (15.2.1.4. Infections) Guide to the quality and safety of tissues and cells for human application. Draft of the 2nd edition of the guide. Department of biological standardization, OMCL network healthcare (DBO). European Directorate for the quality of medicines and healthcare.
10. Directiva 2006/17/CE de la Comisión de 8 de febrero de 2006 por la que se aplica la Directiva 2004/23/CE del Parlamento Europeo y del Consejo en lo relativo a determinados requisitos técnicos para la donación, la obtención y la evaluación de células y tejidos humanos. Anexo I. Artículo 3 letra a.
11. Emerging and Vector-borne Diseases Programme. European Centre for Disease Prevention and Control. Available at: http://ecdc.europa.eu/en/activities/diseaseprogrammes/emerging_and_vector_borne_diseases/Pages/index.aspx.
12. Navarro A, Cabrer C, De Cabo FM, Paredes D, Escalada J, Costa J, Manyalich M. Importance of donor selection and corneal viability. Transplant Proc. 1999; 31: 2609.
13. Minimum medical standards of the European Eye Bank Association operative from 1/02/2015. Available at: http://www.eeba.eu/downloads/EEBA Minimum Medical Standards Rev 2 - 2015 Final.pdf.
14. Kitchen AD, Newham JA, Gillan HL. Effective serological and molecular screening of deceased tissue donors. Cell Tissue Bank. 2013; 14: 633-644.
15. Proietti et al., Global epidemiology of HTLV-I infection and associated diseases. Oncogene 2005; 24: 6058- 6068.
Report abuse