Pediatric Organ Procurement Surgery

Organ procurement is intimately tied to the history of organ transplantation and organ donation. To best understand the organ procurement process, reviewing the history of transplantation is helpful. Notable events have included the following:

• 1905: Eduard Zirm of Austria performed the first successful cornea transplantation.

• 1954: Joseph Murray, MD, at the Peter Bent Brigham Hospital in Boston, Massachusetts, performed the first successful living-related donor kidney transplantation.

• 1962: Murray performed the first cadaveric kidney transplantation.

• 1963: James Hardy, MD, at the University of Mississippi Medical Center in Jackson, Mississippi, performed the first lung transplantation.

• 1967: Thomas Starzl, MD, PhD, at the University of Colorado in Denver, Colorado, performed the first successful liver transplantation.

• 1967: Christiaan Bernard, MD, at Groote Shuur Hospital in Cape Town, South Africa, performed the first successful heart transplantation.

• 1972: The Uniform Anatomical Gift Act established the Uniform Organ Donor Card as a legal document in all 50 states, making it possible for all persons aged 18 years or older to legally donate their organs.

• 1972: The End-Stage Renal Disease Act enabled Medicare coverage of all kidney transplantations.

• 1981: Bruce Reitz, MD, PhD, and Norman Shumway, MD, PhD, at Stanford University Medical Center, Palo Alto, California, performed the first successful heart-lung transplantation.

• 1983: The US Food and Drug Administration (FDA) approved the use of cyclosporine in solid-organ transplantations.

• 1984: The National Organ Transplant Act established a nationwide computer registry operated by the United Network for Organ Sharing (UNOS), authorizing financial support for organ procurement organizations (OPOs). It also prohibited the sale of organs.

• 1988: The FDA approved the use of a universal aortic flush and cold storage solution (ViaSpan, or University of Wisconsin [UW] solution) to extend the preservation time for livers.

• 1989: FK506 (tacrolimus) was introduced clinically as a new antirejection drug.

• 1989: The first liver transplantation from a living-related donor was performed.

• 1990: The first lung transplantation from a living-related donor was performed.

• 1991: The first successful small intestinal transplantation was performed at the University of Pittsburgh.

Organ procurement was started as a local endeavor when facilities performing kidney transplantation recovered organs from donors in the same facility. As the need for organs increased and as the specialty expanded to include other solid organs (eg, heart, lung, liver, pancreas, small intestine), the need for improved sharing agreements and organ distribution was recognized.

In 1969, Dr David Hume of the Medical College of Virginia, in cooperation with Dr Bernard Amos of Duke University, organized the South-Eastern Regional Organ Procurement Program (SEROPP) after determining that tissue typing provided increased graft survival for kidney recipients. With success in these early sharing agreements, SEROPP was awarded a contract to develop an organ procurement and sharing network among 9 medical centers in a 4-state area extending from Baltimore, Maryland, to Atlanta, Georgia.

As SEROPP evolved, it was incorporated into a nonprofit organization in 1975 and renamed the South-Eastern Organ Procurement Foundation (SEOPF). The organization developed and refined the kidney-matching computer program. Crossmatch trays were developed, organ procurement costs were identified and defined, and educational programs were implemented. Procurement programs were begun in many areas of the region.

As the organization and the field of transplantation grew, organ sharing became a nationwide responsibility. SEOPF started a nationwide operation, and the board authorized the organization of UNOS in 1982. The country was divided into 9 geographic regions designed to include previous organ sharing patterns among transplant centers. In 1985, the board members of SEOPF unanimously accepted the recommendation of its committee to incorporate and organize UNOS.

In the early 1980s, the development of cyclosporine made the transplantation of all organs more feasible than before. This led individuals to appeal to the public through the media and their legislators for assistance in finding suitable organ donors. The demand for organs greatly exceeded the supply.

No centralized network was available to increase the use of donated organs, and no criteria were established to define how an individual could access transplantation. A growing concern was that wealthy foreign nationals were coming to the United States to access transplantation technology, to the detriment of terminally ill United States citizens who were also in need of these life-saving procedures.

These issues resulted in a public demand for a national system for organ sharing. The US Congress passed the National Transplant Act of 1984, which legislated the creation of a national task force to study issues regarding transplantation and the establishment of the Organ Procurement and Transplantation Network (OPTN). The OPTN includes all OPOs, transplant centers, and tissue-typing laboratories, as well as patients, their families, donor families, hospitals, voluntary health organizations, physicians, clergy, ethicists, attorneys, healthcare managers, and government officials. OPOs in the United States are not-for-profit organizations that assist in identifying potential organ and tissue donors. They are federally regulated agencies.

The principal purpose of the OPTN was to ensure that patients who were critically ill had access to organs and to improve organ procurement and efficiency. Another function of the OPTN was to assist the transplant community with the development and administration of transplant policy. The OPTN developed practice standards based on training and experience to regulate and ensure the quality of transplant programs. For example, an approved kidney transplant program should have a surgeon who has at least one year of training and one year of experience in kidney transplantation. In addition, centers approved for liver or pancreas transplantation should have a surgeon with training and experience in the transplantation of the specific organ being transplanted.

The National Transplant Act was passed in October of 1984. This act created a task force on organ transplantation that met over 18 months. The task force issued its report in April of 1986. The Department of Health and Human Services (DHHS) awarded a one-year contract for the development and implementation of the national network to UNOS on September 30, 1986.

All clinical transplant centers, OPOs, and tissue-typing laboratories in the United Stated belong to and participate in UNOS. UNOS members developed membership criteria based on the education, training, and experience of medical personnel, and they monitor their compliance with those standards to ensure high-quality and consistent patient care. The UNOS maintains a national list of all patients in the country waiting for solid-organ transplantation. UNOS operates a 24-hour-a-day organ placement center and computer system to ensure efficient and optimal matching of donors and recipients.

Over the years, organ sharing became increasingly complex as the demand for organs grew. A specific sharing system, based on severity of illness and transportability of the organ, has evolved for each organ.

The markedly restricted ischemic time for heart and lungs complicates the issue of sharing thoracic organs. The scoring system for a potential recipient is based on the severity of illness, time on the list, and distance from the donor hospital. The listing status includes 1A for patients in the hospital receiving life support or ventricular assist devices, 1B for patients who are receiving inotropic support but who are ambulatory, and 2 for patients in stable condition at home.

Allocation of livers is based on a numerical scale that quantifies the patient's risk of dying while waiting for a liver transplant, and scores are based on objective and verifiable medical data. ^[1] The system is called the model for end-stage liver disease (MELD) or pediatric end-stage liver disease (PELD). The MELD score is used for adult patients and is based on bilirubin levels, international normalized ratios (INRs), and creatinine values. ^[2] Liver transplant candidates younger than 18 years of age are assigned a PELD score. The PELD score is based on bilirubin levels, INRs, albumin values, growth failure, and age when listed for transplantation. See the MELD Score and PELD Score calculators.

Continuous Organ Distribution

In 2018, OPTN approved the development of a continuous distribution model framework for allocating deceased donor organs. This new framework will allow multiple factors that contribute to a successful transplant to be considered simultaneously as part of the organ offer process. Five goals have been established for continuous distribution ^[3] :

• Prioritize sickest candidates first to reduce waitlist deaths
• Improve long-term survival after transplant
• Increase transplant opportunities for patients who are medically harder to match
• Increase transplant opportunities for candidates with distinct characteristics, such as candidates under the age of 18 or prior living donors
• Promote the efficient management of organ placement

A separate framework will be developed for each organ type. The continuous distribution model for lung transplantation received approval in December 2021 and is expected to be fully implemented in early 2023. ^[4]   A framework for kidney and pancreas continuous distribution is expected before the end of 2022. Continuous distribution models for liver, intestine, heart and vascularized composite allograft will be developed over the next two to three years. ^[3]

 

To start the organ procurement process, a brain-dead donor must be identified. This identification usually occurs during an assessment by the attending physician. The criteria for brain death, although established in general terms, are generally state and hospital specific. The assessment for brain death is undertaken according to hospital policy and state law in a given environment. After the process is completed, the deceased patient is maintained on life support until the OPO responsible for the facility is contacted. In certain states, the law mandates that the OPO be contacted for all patients who are declared brain dead in the hospital. Otherwise, the physician or nursing staff of the unit contacts the OPO to approach the family to discuss organ and tissue donation. Data clearly indicate increased consent rates for organ and tissue donation if the OPO initially contacts the family.

After consent for donation is obtained, the OPO assumes responsibility for the donor patient's care in conjunction with the OPO managing physicians. At this point, the family of the donor incurs no further hospital or medical expense.

The donor then is evaluated for suitability for organ and tissue donation. The evaluation consists of a complete history and physical examination, a detailed family and social history, laboratory examination to detect exposure to infectious diseases or agents (ie, viruses, hepatitis, acquired immunodeficiency syndrome [AIDS]), laboratory examination to assess kidney and liver function, tests to assess lung function, and cardiac evaluation (which sometimes includes cardiac catheterization).

The donor's information is transmitted to the UNOS computer in Virginia, where the information is matched to potential recipients for the respective organs, and a list is printed for each organ being offered. Every potential organ recipient across the country is registered in the UNOS computer.

For kidney transplants, potential recipients for a given organ are determined on the basis of tissue typing and waiting time. For pancreas recipients, waiting time is the main criterion. For heart, lung, and liver transplants, determining factors include severity of illness, size, and distance from the donor hospital.

The list of potential recipients is transmitted to the OPO representing the donor. The OPO representative then calls the various centers where the recipients are registered, presents the donor's information, and receives acceptance or rejection of the prospective organs. As an example, the heart and liver from one donor in Queens, New York, may be offered to patients at 2 local centers (one lung may be offered to a center in Pennsylvania and the other to a center in Connecticut), the kidneys may be offered to 2 other states, and the pancreas may be offered to a patient at a center in South Carolina.

After all the acceptances are received, coordination is started to fly the respective surgical teams to the donor hospital, and the operation is scheduled.

The recovery process often involves the participation of several surgical teams from different areas of the country who are recovering organs from one donor. The abdominal-recovery surgeon often removes the liver, kidneys, and pancreas for other recipient institutions, which saves personnel hours and flight expenses. Thoracic teams still have not achieved that level of cooperation.

After the recovery teams arrive at the donor hospital, the donor is taken to the operating room. Although the patient has been declared brain dead, he or she is treated in the same manner as any patient undergoing surgical intervention. The donor is prepped and draped as for any general surgical operation. Removal of the organs requires meticulous dissection, ischemia of the organs must be minimized, and cardiovascular integrity must be preserved throughout the entire procedure. Blood lost early in the procurement must be replaced, and care must be taken to avoid hypothermia.

The abdominal and thoracic surgeons start the intervention. The technical details differ depending on which combination of organs is to be removed. However, certain principles remain the same. Wide exposure is necessary to achieve adequate visualization. Careful dissection of the organs to be removed is necessary to assess them for aberrant anatomy and to prevent damaging vital structures. Cannulas must be placed for in situ cold perfusion for adequate preservation. Orderly removal of the organs must be accomplished, with removal of the heart first and with cold protection of the organs to be removed last.

Most centers use a technique of careful dissection in the donors to harvest organs. A complete midline incision is made from the sternal notch to the symphysis. The sternum is split. Most hospitals own a sternal splitting saw; however, the procurement team should carry a Lebsche knife with a mallet in case the saw is not available.

The pericardium is opened, and the heart is inspected for its anatomy and function.

The abdominal organs to be transplanted are carefully inspected for their suitability and for other abdominal pathology, such as tumor, foci of sepsis, or unrecognized trauma. The number of organs can range from only the kidneys to all organs, including the intestine. After these organs are deemed acceptable, dissection begins.

The liver is mobilized by dividing the falciform and the left triangular ligaments. Palpation of the lesser omentum for aberrant left hepatic artery from the left gastric artery and a search behind the common bile duct for the right hepatic artery from the superior mesenteric artery are undertaken. Such vessels are carefully preserved. Otherwise, the common hepatic artery from the celiac trunk can be identified. The common bile duct is ligated and divided.

The splenic and left gastric arteries can be ligated to ensure full delivery of preservative solution to the target organs. The portal vein is mobilized. The distal inferior vena cava (IVC) and aorta are exposed by mobilizing the cecum, right colon, and small bowel mesentery. The distal abdominal aorta and the superior mesenteric vein are prepared for cannulation. The infradiaphragmatic aorta is encircled with tape in preparation for cross-clamping.

Dissection of the kidneys can be delayed until the end of the procedure because some surgeons prefer to mobilize the kidneys before perfusion. This facilitates topical cooling of the kidneys.

The cardiac team also may be working simultaneously, exposing the great arteries, superior vena cava (SVC) and IVC, and placing the cardioplegia cannula. After all the teams are ready, the donor patient is given heparin 20,000 IU. Cannulas are inserted into the distal aorta to perfuse the abdominal organs, and the portal vein is cannulated through the mesenteric vein to perfuse the liver. The proximal aortic arch and the infradiaphragmatic aorta are cross-clamped. The left pulmonary vein and IVC are incised to drain the heart and the liver. Cardioplegia and abdominal organ preservation solution are simultaneously delivered through the cannulas. Topical cooling of the heart and abdominal organs is achieved by pouring ice-cold sodium chloride solution into the pericardial sac and abdominal cavity.

The heart is removed first. The IVC and pulmonary veins are divided, followed by the branch pulmonary arteries, aortic arch, and distal SVC. Care is taken to avoid handling the area of the sinoatrial (SA) node and placing excessive tension on the SVC, which may cause dysfunction of the SA node. If the lungs are harvested, they are excised en bloc and separated on the back table. The liver and pancreas are excised next. The common hepatic artery is removed at the level of the celiac trunk with an aortic patch (Carrel patch). The portal vein is divided at the level of the splenic and mesenteric vein junction. The infrahepatic IVC is divided above the renal vein, the suprahepatic IVC is taken with a cuff of diaphragm, and the liver is removed.

The kidneys are retrieved last. The aorta and IVC are exposed by mobilizing the right colon using the Kocher maneuver. The kidneys are mobilized sharply along the Gerota fascia. The ureters are divided below the pelvic brim. Renal vessels are divided with a good cuff of aorta and IVC. Care is taken to include any accessory renal vessels in the vascular patch. In the retrieval of kidneys, there has been a resurgence of the use of the perfusion system to maintain the organ for longer periods of time. Once the kidneys are removed, they are connected to a perfusion apparatus and maintained until the time of delivery. This system appears to lengthen the time of viability over simple cold storage.

The spleen and lymph nodes are also removed for tissue typing. The common and external iliac vessels are harvested and preserved. They are used if needed for transplant vascular reconstruction.

Pancreas recovery is part of a multiorgan retrieval. The techniques for pancreas removal vary from in situ separation from the liver to en bloc retrieval with the liver and kidneys. The more common technique is en bloc removal of the liver and pancreas with separation of the organs at the back table.

The small bowel is also retrieved en bloc with the liver and pancreas. ^[5] The small bowel is divided at the level of the second part of the duodenum and the distal ileum. Further dissection to obtain a segment of small bowel graft or as a combined small bowel and liver graft is performed as a back table procedure.

As the number of donors considered for multiorgan donation has continued to increase, sequential harvesting by several retrieval teams has become impractical. Several rapid techniques for multiorgan harvest to minimize time, dissection, and retrieval injury are described next.

Rapid harvest of a block of tissue including the liver and the pancreas has been advocated. After the midline incision is made, any vascular anatomic variants are then sought. The infrarenal aorta is isolated and controlled with tape. The fundus of the gallbladder is opened and washed free of bile. When all the teams are ready, heparin 20,000 IU are intravenously administered, and a cannula is inserted into the distal aorta. The infradiaphragmatic aorta is clamped. The donor is exsanguinated by incising the IVC intrapericardially at the diaphragmatic level. The aorta is flushed with 2-3 L of UW solution, depending on the size of the donor. On some occasions, the portal vein is perfused through the inferior mesenteric or ileocolic veins. Topical cooling of the abdominal organs is also achieved by using iced sodium chloride solution.

After the heart is removed, the distal abdominal aorta and IVC are exposed by amply mobilizing the right colon and duodenum. Proximal dissection stops at the renal veins to avoid injuring the renal arteries or an unrecognized right hepatic artery from the superior mesenteric artery. The gastrocolic ligament and the short gastric vessels are divided. The spleen and pancreas are mobilized medially. The left gastric artery is cut, and the celiac axis is exposed. The duodenum is transected just distal to the pylorus and the fourth portion by using GI anastomosis (GIA) staplers. The aorta is divided at the diaphragmatic hiatus and freed posteriorly from retroperitoneal attachments. It is transected distally below the mesenteric artery and the IVC above the renal veins. The liver and pancreas are removed en bloc and separated on the back table. The kidneys can be removed with the liver and pancreas by transecting the aorta and IVC just above the iliac bifurcation.

Efforts are in place to initiate cadaveric perfusion to increase organ yield. Studies are in place to perfuse organs of clinically dead donors to recover kidneys and liver. The results of these efforts are pending. ^{[6, 7, 8]}

The issue of who should receive the retrieved organ still remains. Several sharing and allocation schema have been used over the years. At present, the recipient's severity of illness, time on the waiting list, and location from the donor hospital are used to calculate a point score. The patient with the most points reaches the top of the list.

This allocation system varies from organ to organ, depending on the acceptable ischemic time for the given organ offered. For instance, kidney allografts can be preserved for 48 hours or longer, which allows for kidneys to be shipped easily across the country. Also involved in kidney allocation is the biologic reality that 0 antigen mismatches between the donor and the recipient improves long-term allograft survival. As a result, a payback system has evolved for kidney allocation. If one center receives a kidney from another region that is a 0 antigen mismatch for one of their recipients, that center is required to payback by releasing the next procured kidney to the general pool.

The most recent controversy in allocation involves the distribution of liver allografts. Because liver preservation has improved to the point that they can be maintained for more than 12 hours, regional sharing of this organ alone has been questioned. The current policy is that the potential recipient who is most ill receives the next available organ.

UNOS recently implemented policy designed to match donated livers with patients on the waiting list. The MELD is used for adult candidates for liver transplants. Each candidate is given a numerical score calculated by using a formula based on routine laboratory results. This score reflects the urgency of each candidate's need in the next 3 months. With this policy, the former liver transplant statuses of 2A, 2B, and 3 are replaced with a continuous scale. The MELD policy does not affect the status 1. (Status 1 patients are critically ill with fulminant liver failure or a new but nonfunctioning liver allograft; their life expectancy is < 7 d without liver transplantation or retransplantation.)

The MELD system improves precise ranking of patients so that those in greatest need are assigned the highest priority, rather than allocating livers to patients who have accumulated waiting time but who are in relatively stable condition. MELD score ranges from 6 (relatively well) to 40 (gravely ill). These scores fluctuate as a candidate's laboratory results change during the waiting period. When 2 patients with the same MELD score are offered an organ, waiting time is the tiebreaker. See the MELD Score calculator.

The PELD model is used to rank liver transplant candidates younger than 18 years. Although this similar to the MELD system, the PELD system also accounts for the growth and developmental needs of the candidates. ^[9] Children with rare medical conditions may be eligible for a modified score. Again, pediatric status 1 remains in place. The 2B and 3 statuses are replaced by PELD system. No pediatric status 2A is defined. See the PELD Score calculator.

The sharing of hearts and lungs is limited by the 4- to 6-hour viability of these organs after they are removed from the donor's body. Therefore, travel distance still restricts their distribution. These organs tend to be distributed regionally, and potential recipients who are most ill are still favored in the allocation schema.

As organ preservation methods improve, the controversy surrounding the sharing of this vital resource will intensify because of the paucity of organ donors.

Organ transplantation is clearly a feasible therapeutic alternative for the management of end-stage organ failure. Proliferation of this therapy is severely limited by the inadequate number of organ donors.

Deceased donor organ donation has plateaued. The reasons for this are unclear; however, an estimated 12,500-27,000 potential donors die each year in the United States. Only 15-20% of potential donors become actual donors. This failure stems from a lack of education of the public and of health professionals. If consent were obtained from these potential donors, as many as 180,000 additional recipients would be helped annually.

The future of organ procurement and donation rests on education of the public and on legislative assistance.