Optimal care of the potential organ donor requires a sound grasp of the physiologic derangements unique to brain death, including hemodynamic instability, diabetes insipidus, disseminated intravascular coagulation due to the release of tissue thromboplastin from the injured brain tissue, and neurogenic pulmonary edema. Before brainstem herniation the patient often develops hypertension and tachycardia due to an autonomic storm, which results in massive release of catecholamines. These hemodynamic manifestations are transient, and they are followed by hemodynamic collapse and hypotension after brainstem herniation and loss of vasomotor tone. Overly aggressive attempts to control the transient hypertension may result in profound shock. This may be exacerbated by volume depletion due to the use of mannitol, diuretics, and/or hypertonic saline for attempted control of elevated intracranial pressure. Diabetes insipidus is common, and a failure to administer appropriate volume replacement and dosmopressin (DDAVP) may result in severe hypernatremia, which has been reported to increase the risk of organ preservation damage and primary nonfunction in the donated graft. Vasopressors should be kept to a minimum to avoid myocardial damage and splanchnic ischemia. Some centers consider the donor heart unsuitable if vasopressors exceed 10 to 15 mcg per kg per minute for prolonged periods of time. Although most donors will require the judicious use of vasopressors, it has recently been shown that the doses can be kept to a minimum by the concomitant use of replacement thyroxine (3).

Two licensed physicians should independently perform neurologic examination to declare brain death. The recommended interval between the two evaluations is 48 hours for infants younger than 2 months, 24 hours for infants 2 months to 1 year, 12 hours for ages 1 to 18 years, and for patients older than 18 years the interval is optional. The patient should be normotensive, normothermic, and not hypoxic. Toxicology should be negative for suppressant drugs, and the electrolytes should be within normal range. Clinical absence of brainstem function is manifest by the lack of corneal, pupillary, and gag reflexes, no “doll’s eyes” or response to cold caloric stimulation, and no spontaneous respiration as determined by the apnea test (4). The apnea test should be performed carefully in the presence of concomitant hypoxia or hemodynamic instability due to the risk of cardiac arrest. Because apnea test may be risky, the physician may choose to substitute a confirmatory test such as a cerebral perfusion scan, electroencephalogram, or transcranial Doppler. In infant organ donation, some believe that confirmatory tests should be mandatory and recommend two confirmatory tests if the donor is younger than 2 months old, one confirmatory test if the donor is 2 months to 1 year of age, and optional confirmatory test if the donor is greater than 1 year. A word of caution, however—confirmatory tests may yield an imprecise or ambiguous result, posing an emotionally difficult situation for both clinicians and family.

It is important that the treating physicians and nurses do not discuss the possibility of organ donation with the patient’s family. The trained representative of the local organ procurement agency is best suited to make this approach. The emotional needs of the grieving family, and the individual cultural differences are best recognized and addressed by specifically trained professionals. The team of nurses, trauma surgeons, neurosurgeons, and intensivists should be frank in their discussions with the family regarding the gravity of the patient’s clinical condition. The treating team must compassionately explain the meaning and diagnosis of brain death. However, the team should never give the family the slightest suspicion of a “conflict of interest.”

Allocation of donor solid organs depends on severity of illness, blood type, and, to some extent, waiting time. Kidney allocation also takes human leukocyte antigen (HLA) typing into account when there is a six-antigen match. Allocation of donor hearts depends heavily on the severity of heart failure. The allocation systems for both kidneys and hearts has not changed significantly in several years.

Conversely, the allocation of donor livers changed dramatically in 2002. An effort was made by the United Network of Organ Sharing (UNOS) to establish measurable, objective criteria for cadaveric liver allocation in place of the previous Child-Turcotte-Pugh-based status 2A, 2B, and 3 categories. The new model for adults is a continuous point system called the model for end-stage liver disease (MELD), a mortality risk score based on serum creatinine, bilirubin, and international normalized ratio (INR). In children, the pediatric end-stage liver disease (PELD) point system is based on similar criteria, including bilirubin, INR, albumin, growth failure, and age (5). In neither the MELD nor PELD systems, is much consideration given to waiting time; rather, the organ is preferentially allocated to the sickest patient, that is, the patient with the most points. In both systems a patient listed as a medical emergency, status 1 (strictly defined as less than 1 week life expectancy without a transplant), has precedent over all other patients, regardless of the MELD or PELD points. In addition, the transplant center may apply to the regional UNOS board for a medical exception to the standard MELD and PELD criteria (e.g., malignancy). If the exception is approved, it may yield a large number of “bonus” points. The intended objectivity of the new PELD system has been called into question by many because there have been dramatic increases in the number of patients listed as status 1 and of patients with approved exceptions.

The geographic and age priorities for liver allocation also changed in 2002. Donor livers were previously placed preferentially within the local procurement area. Now, status I recipients in the entire region are given priority over the top MELD/PELD score in the local procurement area. This has raised much emotional debate throughout the transplant community. Kentucky and Arizona are examples of states prohibiting sending an organ out of state before first offering it to an instate transplant center. At least 13 states have considered similar legislation. In Colorado, a bill was introduced directing organs away from adults when they could be used by children. In fact, most regions now preferentially allocate organs donated by children (younger than 18 years old) to other children. Because donor organs remain in critically short supply, it is likely that the competition for priority will continue to prompt ongoing changes in the allocation system.

The competition for allocation priority should not cause us to lose sight of the fundamental problem—there is a shortage of donor organs. The committee assigned to review liver organ utilization by the American Society of Transplant Surgeons and the American Society of Transplantation identified multiple practices that could expand the donor pool (6). Such measures include non–heart-beating donors, increased use of marginal grafts, more efficient allocation, and especially for livers, a wider application of split-liver transplantation.

Once consent for donation has been obtained, the local organ procurement agency must coordinate the allocation of all appropriate solid organs involved (heart, lungs, liver, kidney, pancreas, and/or small bowel), and arrange for a timely and coordinated organ harvest. In contacting each potential recipient’s transplant surgeon, the agency must offer a complete summary of the donor’s medical history and current condition. The vital information, which must be relayed to the potential accepting surgeon, is shown in Table 46-1. General criteria of a suitable donor are listed in Table 46-2.

Most donors will be suitable for multiorgan retrieval. A cardiac team will procure the heart and lungs if suitable. The technique for deceased donor heart and lung retrieval is described in Chapter 48.

The classic technique for donor hepatectomy was described by Starzl and includes dissection of the hepatic hilum before cold perfusion (7). When time is of the essence, a modification of this technique known as the “rapid flush” technique is used to improve organ recovery in unstable donors (8). A midline skin incision is made from the sternal notch to the symphysis pubis and is often augmented by a bilateral transverse extension to maximize exposure. The peritoneal cavity must be thoroughly inspected for intraabdominal trauma, neoplasm, or peritonitis. The right colon and duodenum are mobilized medially until the root of the mesentery, superior mesenteric artery (SMA) and vein (SMV), vena cava, and aorta are exposed. The portal system is cannulated through the superior mesenteric vein. The gallbladder is opened and flushed. Generous systemic heparin is given, approximately 250 units per kg. The aorta is encircled proximal to the iliac bifurcation, and an aortic cannula is inserted. When the liver and pancreas are to be harvested, the hepatic artery and SMA are often dissected before cold perfusion, although this may not be possible in a hemodynamically unstable donor. Similarly, an in vivo split of the liver must be completed before cold perfusion. The cardiac team simultaneously prepares the heart and lungs, and places a vent in the suprahepatic vena cava. Once all appropriate preparatory work is completed, the aorta is cross-clamped above the bifurcation, the viscera are perfused simultaneously through both the aortic and SMV/portal cannulas with cold preservation solution (University of Wisconsin), and the viscera are packed in crushed ice (frozen saline). The thoracic aorta is generally not clamped until after removal of the heart. Once the effluent fluid from the suprahepatic vena cava clears (in an adult after about 4 L through the aorta and 1 L through the SMV/portal), hepatectomy is completed taking care to perform the dissection well away from important anatomic structures and preserve any aberrant hepatic arterial anatomy (9,10). Once the liver, kidneys, and possibly pancreas and small bowel are removed, the iliac vessels are harvested. Each organ is submerged in cold preservation solution, sterilely triple-bagged, and carefully packed in ice and slush to maintain a tissue temperature of 0°C to 4°C. The final dissection to clean the arteries, reconstruct any aberrant arterial anatomy, and clear away extraneous tissue is performed as a back-table procedure at the site of transplantation. It is vitally important to keep the organ
submerged in the cold preservative solution at 0°C to 4°C throughout transport and back-table preparation.