Chapter 33 Organ Transplantation
1. What are the most commonly transplanted organs?
2. How does donation after brain death differ from donation after cardiac death?
3. What conditions preclude transplantation?
4. What is the most common cause of death in organ transplant recipients?
5. Most transplant candidates are screened for comorbidities prior to being waitlisted. What additional beneficial preoperative measures can be undertaken once a donor is identified?
Kidney transplantation
6. Who is a candidate for renal transplantation?
7. What is the major cause of death in dialysis patients?
8. What differs between an extended criteria donor kidney and a standard criteria donor graft?
9. Where is the donor kidney transplanted in the recipient patient? From where does it derive its vascular supply? Where is the ureter anastomosed?
10. What are the preoperative considerations for the patient scheduled to undergo renal transplantation?
11. How is preoperative ischemic heart disease ruled out prior to transplant listing?
12. What is the usual general anesthetic regimen administered for renal transplantation?
13. What consideration must be made when selecting a neuromuscular blocking drug for patients undergoing renal transplantation?
14. Why is optimal hydration important during renal transplantation? What type of crystalloid solution should be used for hydration? What monitoring method may be used to help guide hydration intraoperatively for renal transplantation?
15. Is dopamine of benefit during renal transplant procedures?
16. Why is mannitol administered intraoperatively during renal transplant procedures?
17. Cardiac arrest after completion of the renal artery anastomosis is thought to be secondary to what?
Liver transplantation
18. Who is a candidate for liver transplantation?
19. How are liver transplant recipients prioritized for organ allocation?
20. What is the 1-month mortality for a waitlisted candidate with a high model for end-stage liver disease (MELD) score (score > 30)?
21. What physiologic disturbances are often present in patients before liver transplantation?
22. What is the best screening test for portopulmonary hypertension?
23. What is hepatopulmonary syndrome? Why is it significant?
24. What types of monitoring may be used intraoperatively during liver transplantation?
25. What types of intravenous access are typically established preoperatively for liver transplant procedures? Why should placement be supradiaphragmatic?
26. Why are cell-saver devices used intraoperatively for liver transplantation?
27. Why is calcium administration often required during liver transplantation?
28. What are the three stages of liver transplant procedures?
29. What are the characteristic physiologic derangements of the preanhepatic stage of liver transplant procedures?
30. What are the characteristic physiologic derangements of the anhepatic stage of liver transplant procedures?
31. What is the “piggy-back” technique and why is it used in some patients?
32. What are the characteristic physiologic derangements that occur with reperfusion of the donor graft during liver transplant procedures?
33. Which coagulopathies can occur during liver transplantation?
34. Why is nitrous oxide avoided for maintenance anesthesia during liver transplantation?
35. Why do some anesthesiologists prefer cisatracurium as the nondepolarizing neuromuscular blocking drug for liver transplantation?
36. What signs of donor graft function can be assessed intraoperatively after graft reperfusion?
37. When is extubation of the trachea after liver transplant surgery performed?
Heart transplantation
38. Who is a candidate for heart transplantation? What ejection fraction is commonly seen in patients undergoing heart transplantation?
39. What are the goals for the induction and maintenance of anesthesia for heart transplant patients?
40. What vessels are transected and anastomosed during heart transplant surgery? What does this mean with regard to a central venous or pulmonary artery catheter?
41. What is the indication for isoproterenol during heart transplantation?
42. Does the transplanted heart react better to catecholamines that are direct or indirect acting?
43. Name the physiologic conditions that should be optimized prior to weaning from cardiopulmonary bypass.
44. Name three conditions that may worsen pulmonary hypertension.
Answers*
1. Organs that may be transplanted in humans include the heart, kidneys, liver, lungs, pancreas, and intestines. The bone marrow may also be transplanted for certain forms of cancer. (580)
2. The diagnosis of brain death is based on the loss of cerebral cortical and brainstem function. The loss of cerebral cortical function is implied from unconsciousness, the lack of spontaneous movement, and unresponsiveness to external stimuli. The loss of brainstem function is implied from apnea and absent cranial nerve reflexes. Clinical studies that may be performed to provide supporting evidence include an electroencephalogram or cerebral blood flow studies. Irreversibility of the diagnosis of brain death should also be established. This is usually achieved by the lack of any improvement in 12 to 24 hours after the diagnosis. Other derangements that must be excluded include central drug effects, postictal states, cardiovascular or metabolic instability, or hypothermia. The diagnosis of brain death is always made before a donor procedure and never in the operating room. However, in the absence of brain death, but in the presence of a devastating and irreversible brain injury, the patient’s family may elect to withdraw life support. In the event the family consents to organ donation, withdrawal of support is typically done in the operating room. If the patient succumbs as a result of the withdrawal of life support—experiences cardiac death—organs may be harvested. Under these conditions, the organs undergo a period of ischemia at normal body temperature (termed “warm ischemia”), a condition which necessitates rapid cooling, preservative administration, and procurement to minimize ischemic injury. (580)
3. Untreated systemic infection, incurable malignancy, untreated substance abuse, and lack of sufficient social support to comply with post-transplant care are contraindications to transplantation. (580)
4. The most common cause of death in transplant recipients is infections due to chronic immunosuppression. All physicians, including anesthesiologists, caring for the transplant patient should adhere to strict aseptic technique. (587)
5. Because of the long wait times between listing and transplantation (not infrequently a year or more), preoperative screening tests may need to be repeated particularly when prior results are equivocal. Most important are tests for ischemic heart disease (postoperative cardiovascular mortality is second in frequency to infection), assessment of laboratory results such as electrolytes and hemoglobin, and, if needed, preoperative dialysis. (580)
Kidney transplantation
6. Kidneys are the most commonly transplanted major organ. Patients who have end-stage renal disease and are being considered for (or are currently receiving) dialysis are candidates for renal transplantation. Transplantation has led to lower overall morbidity and mortality than dialysis and to improved survival. The most common cause of end-stage renal disease leading to chronic dialysis dependence is diabetes mellitus, followed by hypertension. (581)
7. Cardiovascular disease is responsible for over 50% of deaths in patients receiving dialysis. (581)
8. Extended criteria donors are older donors, donors with diabetes, and grafts with prolonged preservation times (acceptable times vary by organ; for the kidney > 24 to 36 hours of cold ischemia is considered prolonged, for the liver > 8 to 12 hours). Organs donated after cardiac death incur additional warm ischemia and are considered as a subcategory of extended criteria grafts. (581)
9. The kidney is transplanted on one side of the recipient’s iliac fossa. The vascular supply for the transplanted kidney is derived from the iliac vessels. The ureter of the transplanted kidney is anastomosed directly to the recipient’s bladder. (581)
10. Preoperative considerations for the patient scheduled to undergo a renal transplant are similar to any other surgical procedure in which the patient has chronic renal failure. This includes scheduling of hemodialysis prior to surgery to optimize the patient’s volume status, electrolytes (particularly potassium), and acid-base balance. The serum glucose levels of the patient with diabetes mellitus should also be evaluated before and during surgery. (581)
11. Preoperative ischemic heart disease should be ruled out preoperatively. Stress echocardiography is probably better than thallium imaging in predicting postoperative cardiac events. Coronary angiography should be considered in high-risk patients. (581)
12. The usual general anesthetic regimen for renal transplant procedures is balanced anesthesia: a combination of volatile anesthetic and short-acting opioid. Nitrous oxide is avoided because it causes bowel distention. (582)
13. When selecting a neuromuscular blocking (NMB) drug, consideration should be given to the method of clearance. A NMB that does not rely primarily on renal clearance should be selected. Cisatracurium is particularly attractive because its metabolism is independent of both the kidney and liver. (582)
14. Optimal hydration is important to improve the early function of the transplanted kidney. The crystalloid solution used for hydration intraoperatively should not contain potassium (e.g., normal saline). Monitoring the patient’s central venous pressure may be a useful guide to the patient’s state of hydration. (582)
15. Dopamine is often administered intraoperatively during renal transplant in an effort to increase renal blood flow and kidney perfusion. However, no studies support this practice. Other methods of ensuring adequate renal perfusion are the maintenance of systemic blood pressure near normal and the provision of adequate hydration. (582)
16. Mannitol is often administered intraoperatively during renal transplant procedures to facilitate an osmotic diuresis. However, controlled studies supporting an improved outcome are lacking. (582)
17. Reperfusion of the newly transplanted graft can lead to hyperkalemia; however, this life-threatening complication is less frequently seen during kidney transplantation than with liver graft reperfusion. A potassium-containing solution is used to preserve the kidney before transplantation. The washout of this solution and accumulated acid metabolites is believed to be the cause of the hyperkalemia. (584)
Liver transplantation
18. Patients with acute hepatic failure, chronic end-stage liver disease, tumors (in the absence of extrahepatic spread), and metabolic abnormalities affecting their liver are candidates for liver transplantation. (582)
19. Patient acuity, as determined by the MELD score, is used to allocate organs. The MELD score predicts 90-day mortality in the absence of transplantation. (582)
20. A patient with a MELD score greater than 30 has a 30% probability of dying or becoming too ill for transplant within a 30-day period. (582)
21. Physiologic disturbances in patients with end-stage liver disease affect virtually every organ system. The patient may have encephalopathy, ranging from mild confusion to coma; hyperdynamic circulation due to decreased systemic vascular resistance and an increased cardiac output; decreased plasma volume; and ascites. Arterial hypoxemia may be due to pulmonary effusions, atelectasis, or hepatopulmonary syndrome. Renal dysfunction and oliguria may be present. Patients may have anemia, thrombocytopenia, and coagulopathy. Electrolyte abnormalities that may be present include hypokalemia, hypocalcemia, and hyponatremia. Finally, these patients may have glucose intolerance or frank diabetes. As the age of patients undergoing liver transplantation increases, the proportion with coronary artery disease has increased. (583)
22. Portopulmonary hypertension is defined as pulmonary hypertension (mean pulmonary artery pressure >25 mm Hg) in the presence of portal hypertension. Resting echocardiography is a useful screening test because it identifies nearly all patients with the condition. In patients with an estimated right ventricular systolic pressure greater than 50 mm Hg on echo, right heart catheterization is used to confirm or rule out the diagnosis. There is significant perioperative mortality associated with mean preoperative PA pressure greater than 35 mm Hg. (583)
23. Hepatopulmonary syndrome (HPS) consists of arterial hypoxemia (PaO2 < 70 mm Hg on room air) in the presence of an intrapulmonary shunt. Liver transplantation cures HPS, albeit over a variable time course. There is, however, an increased risk of perioperative mortality in patients with significant HPS (PaO2 < 50 mm Hg on room air). (583)
24. Monitors that facilitate the anesthetic management of patients undergoing liver transplant procedures include invasive arterial blood pressure monitoring and monitoring of cardiac filling pressures using a pulmonary artery catheter. These monitors are useful because major shifts in the intravascular volume and hemodynamic instability almost always occur. Arterial blood pressure is best monitored from an artery above the level of the diaphragm because the aorta may be cross-clamped during the portion of the procedure in which anastomosis of the hepatic artery takes place. Transesophageal echocardiograms are useful to monitor the volume status and cardiac function, and to detect emboli. A Foley catheter is used to measure urine output. (583)
25. Peripheral intravenous access should be established preoperatively using several large-bore catheters to allow for the ability to transfuse blood products rapidly. Intravenous catheters should be placed above the level of the diaphragm because the inferior vena cava is typically cross-clamped during the procedure. (584)
26. Cell-saver devices are often used intraoperatively during liver transplant procedures because of the massive amounts of blood loss and massive fluid requirements during the procedure. (584)
27. Calcium administration is often required during liver transplantation because of the frequency of citrate toxicity, caused when the citrate in banked blood binds with ionized calcium, which can cause myocardial depression. This condition is more frequent during liver transplantation, particularly the anhepatic stage, as the liver is unavailable to metabolize citrate. (584)
28. The preanhepatic, anhepatic, and neohepatic stage comprise the stages of the surgical procedure. The preanhepatic stage involves the dissection of the portal venous structures and mobilization of the native liver. The anhepatic stage begins when the native liver’s blood supply is interrupted by clamping of the suprahepatic and infrahepatic inferior vena cava and the portal vein. The neohepatic stage begins with the return of vascular supply to the graft, usually via the inferior vena cava and portal vein. (584)
29. The preanhepatic stage of liver transplant procedures is characterized by cardiovascular instability due to sudden decreases in the intraabdominal pressure, and the exacerbation of chronic hypovolemia due to loss of ascites and hemorrhage. Metabolic and electrolyte abnormalities can occur during this stage, including metabolic acidosis and hypocalcemia. Hemorrhage, often requiring the rapid infusion of fluids and blood products, is related to the degree of portal hypertension and adhesions from prior abdominal surgery. (584)
30. The anhepatic stage of liver transplant procedures is characterized by precipitous decreases in venous return and cardiac output. For this reason, cardiac inotropic drugs and sympathomimetic drugs are often administered during this portion of the liver transplant procedure to maintain cardiac output. Hypocalcemia and metabolic acidosis commonly occur during this stage. (584)
31. The piggy-back technique involves the anastomosis of the donor hepatic veins to the recipient vena cava, followed by portal anastomosis. The piggy-back technique is preferred by some centers because it avoids transection of the inferior vena cava, which may preserve venous return. An alternative to the piggy-back technique is the use of venovenous bypass, which involves rerouting blood from the inferior vena cava to the superior vena cava, which can augment venous return. It is not universally used as it prolongs surgery and has unique complications, including air embolism.
32. The neohepatic stage of liver transplant procedures is characterized by the potential for precipitous hyperkalemia, acidosis, and hypothermia due to the cold ischemic effluent from the graft entering the central circulation. The systemic vascular resistance drops, and emboli of blood or air can occur. Hyperkalemia is exacerbated by the washout of the potassium-containing solution used to preserve the liver, in addition to unclamping of the inferior vena cava and portal vein. Hypotension, arrhythmias, and cardiac arrest may potentially occur during this time. (584, Table 36-5)
33. Coagulopathies that can occur during a liver transplant procedure include thrombocytopenia, decreased levels of multiple coagulation factors (due to decreased synthesis and dilution), and fibrinolysis. (584)
34. Nitrous oxide is often avoided for maintenance anesthesia during liver transplantation because it may cause bowel distention. Additionally, nitrous oxide may increase the size of embolized air, and it may increase pulmonary vascular resistance in a population prone to pulmonary hypertension. (583)
35. Cisatracurium is often selected as the nondepolarizing neuromuscular blocking drug, because its elimination is by spontaneous Hofmann elimination and ester hydrolysis, which are independent of liver function. (583)
36. Signs of graft function include improvement in metabolic acidosis (due to metabolism of citrate to bicarbonate), a reduced calcium requirement (again, due to the liver’s ability to metabolize citrate), and a rising body temperature (due to exothermic reactions in the liver). Hepatorenal syndrome may occur, as noted, by increasing urine output.
37. The trachea generally remains intubated at the conclusion of the transplant until the patient is hemodynamically stable, bleeding is controlled, and the graft appears to be functioning well. (584)
Heart transplantation
38. Patients with end-stage heart disease are candidates for heart transplantation. Patients with pulmonary hypertension and end-stage heart disease are candidates for heart-lung transplant procedures. Patients undergoing a heart transplant procedure usually have heart disease secondary to coronary artery disease or a cardiomyopathy. The ejection fraction generally seen in these patients is less than 20%. (585)
39. The induction of anesthesia for cardiac transplantation may include a benzodiazepine and an opioid. The maintenance of anesthesia may be opioid based as well. The goal of the anesthetic induction and maintenance is to provide good endotracheal intubating conditions while preserving cardiac function. The potential risk of volatile anesthetics during a heart transplant procedure is myocardial depression, vasodilation, or both. (585)
40. Vessels that are transected and anastomosed during heart transplant procedures include the aorta, pulmonary artery, and left and right atria. These are done during cardiopulmonary bypass. A central venous or pulmonary artery catheter that is in place at the onset of surgery must be pulled back into the internal jugular vein when the patient’s heart is excised. (585)
41. Isoproterenol is indicated for the maintenance of myocardial contractility and heart rate in the denervated donor heart during and after weaning from cardiopulmonary bypass. Isoproterenol also decreases pulmonary vasculature resistance. (585)
42. The transplanted heart reacts better to direct-acting catecholamines. Indirect acting drugs including atropine, which work via the autonomic nervous system, are ineffective due to denervation of the graft. (585)
43. Prior to weaning from cardiopulmonary bypass, patients should be normothermic, and free from acid-base and electrolyte disturbances. The lungs are ventilated and the cardiac chambers free from air.
44. Pulmonary hypertension is exacerbated by hypoxemia, hypercarbia, and elevated cardiac output, pulmonary vessel spasm, and emboli. (585)
Lung transplantation
45. Double-lumen endotracheal tubes are used for intubation of the trachea for lung transplant surgery. This allows isolated ventilation of either the left or right lung, so that one lung may be ventilated while the other is being transplanted. (586)
46. Intraoperative problems during lung transplant procedures may include arterial hypoxemia and pulmonary hypertension. Arterial hypoxemia may occur during one-lung ventilation. Pulmonary hypertension may occur secondary to pulmonary artery clamping, particularly in patients with preexisting elevation of pulmonary pressure. (586)
47. Lung transplant patients are predisposed to pneumonia due to disruption of lymphatic drainage, poor mucociliary function, obstruction of bronchi from clots in the bronchial suture lines, and loss of the cough reflex. Immunosuppression exacerbates the risk of infection. (586)
Pancreas transplantation
48. Patients with diabetes mellitus are candidates for pancreas transplantation. (586)
49. Most (65%) pancreas transplants are performed simultaneously with kidney transplants because of the advanced nature of the diabetes, which is associated with renal failure. Simultaneous pancreas-kidney transplant recipients experience the best graft survival rates. The success of a pancreas transplant is measured by monitoring blood glucose levels after surgery; blood glucose concentrations may return to normal within hours. (587)
