Heart History Current history
Careful and complete documentation of the circumstances surrounding the death of the donor is essential. A history of blunt chest trauma raises the question of myocardial contusion, which can be ruled out with a combination of myocardial specific enzymes, ECG, and direct inspection of the chest wall and heart. A history of sudden death without known cause raises the question of a primary cardiac event such as an arrhythmia or myocardial infarction. Even with a clear history of a closed head injury due to a fall or motor vehicle accident, it is important to determine if a sudden cardiac event could have precipitated the accident. The role of any toxin exposure contributing to the cause of death (e.g., cocaine, alcohol, or carbon monoxide) may increase the risk of myocardial damage. Documentation of the duration or estimated duration of any "down time" prior to resuscitation is important to determine the possibility of ischemic injury to the heart. The need for prolonged CPR or DC cardioversion should be documented, although it does not preclude transplantation of the heart if the functional assessment is satisfactory. Past history
Any prior medical or surgical history of cardiac disease, or other disease with systemic manifestations likely to affect the heart, will likely preclude cardiac donation. These may include malignancy, connective tissue diseases, blood dyscrasias, or peripheral vascular disease. Potential cardiac donors with a recent or distant myocardial infarction, valvular heart disease, or a documented history of arrhythmias should be excluded. Coronary artery disease is the most common form of cardiac disease in the United States, affecting up to 40% of those over the age of 40. Therefore, any risk factors for coronary artery disease including male sex, a family history of premature coronary disease, smoking, diabetes mellitus, hypertension, hyperlipidemia, and obesity should be carefully documented. The presence of any of these risk factors in a patient over 40 years of age may prompt the request for a coronary angiogram prior to accepting the organ. Additionally, the transplant surgeon should take special care in assessing the coronary arteries at the time of organ procurement. Robiscek59 has suggested performing bench coronary angiography at the time of organ procurement to rule out significant coronary disease in the older or high risk donor. On occasion, coronary revascularization has even been performed on donor hearts at the time of transplantation into high risk recipients.14,15,60
Primary graft failure remains the leading cause of early death after heart transplantation.25 Early graft failure may occur as the result of (1) preexisting cardiac disease, (2) inadequate cardiopulmonary resuscitation after brain death, (3) myocardial injury resulting from brain death, (4) organ preservation injury, or (5) technical complications during implantation (e.g., air embolism). A careful history and functional evaluation of the donor heart can reduce the risk of early graft failure due to the first three factors. The techniques for functional assessment of the heart are outlined below. Preventing graft failure from preservation injury or technical complications is addressed in other chapters. Electrocardiography (ECG)
An electrocardiogram is obtained from all donors looking for evidence of active ischemia, prior infarction, rhythm or conduction disturbances. Other abnormalities such as fluctuation in the ST segment are often seen in patients with increased intracranial pressure or subarachnoid hemorrhage.61-64 These ECG changes may not always indicate irreversible myocardial injury. However, when associated with wall motion abnormalities on echocardiogram, they are frequently associated with histopathologic evidence for injury (contraction band necrosis, coagulation necrosis, and myocytolysis) and the risk of early graft failure is substantial.65-69 These findings have been attributed to the "catecholamine storm" which occurs following brain death. The very high levels of norepinephrine, epineph-rine, and dopamine noted after brain death are felt to cause a rapid influx of cal
cium into the myocyte with overload of the contractile apparatus similar to that observed with ischemia.65,70 Echocardiography (ECHO)
ECHO evaluation is the key study used in assessing the potential cardiac donor. Information regarding cardiac anatomy, valvular structure and function, ventricular chamber size and function, wall thickness and motion abnormalities is readily obtained by this modality. Interpretation of such crude quantitative measures of global ventricular function as ejection fraction or shortening fraction must always take into account the heart rate, volume status, and evidence for sep-tal dysfunction caused by pulmonary hypertension and right ventricular afterload. ECHO may be particularly helpful in assessing cardiac function and structure after trauma, where it can exclude valvular abnormalities or cardiac contusions. Moreover, rare congenital defects and cardiac tumors can be identified. More subtle abnormalities such as septal hypokinesis, mitral valve prolapse without regurgitation, or small pericardial effusions can be detected by this modality. In general, such findings would not preclude transplantation. Hemodynamic status and pressors
Basic hemodynamic data such as systemic blood pressure, heart rate, and central venous pressure (when available) are reviewed. The current level of pressor and/or inotropic support is of significant importance. The use of dopamine at a dose of < 10 mcg/kg/min is usually preferred. More than low or moderate doses of these agents should alert the evaluating physician to potential problems with the heart. Etiologies of cardiac dysfunction may include preexisting disease, myocardial contusion, prolonged pressor support, systemic sepsis, hypoxemia, or cardiac depression secondary to brain death. The use of a pulmonary artery catheter is of occasional utility in assessing these patients. Coronary angiography
As the age range of donors has expanded, the requests by transplant programs for coronary angiography has also increased. Potential donors with risk factors for coronary artery disease can now be assessed and many may remain acceptable based on results of angiography.
Cardiac enzymes are often obtained in potential donors but rarely impact the decision to use the organ. They become useful when there is a question about myocardial injury prior to organ donation, such as with prolonged CPR or resuscitation, multiple DC cardioversions, or concerns about possible myocardial infarction or contusion. The level of total CK alone is virtually useless since it is too nonspecific, being elevated with any brain, muscle, or heart injury. The combination of total CK with the CKMB isoenzyme determination is more helpful, but timing is quite critical since the CKMB usually peaks within 6-12 hours after injury and often falls to near normal within 24-48 hours. We have found that a measurement of troponin-I is often much more useful since it is quite cardiac specific and usually remains elevated for up to a week following myocardial inj ury.
Only about 25% of cardiac donors (15-20% of all cadaver solid organ donors) have lungs suitable for lung transplantation using standard lung donor criteria.71 Multiple factors account for this discrepancy including
1) early colonization of the airway caused by loss of upper airway clearance mechanisms with mechanical intubation,
2) aspiration during resuscitation,
3) neurogenic pulmonary edema caused by brain injury,
4) excessive volume resuscitation to compensate for the loss of peripheral vasomotor tone associated with brain death,
5) acute respiratory distress syndrome (ARDS) due to release of cytokines with the systemic bacterial infection (SIRS),
6) traumatic pulmonary contusion, and
7) fat embolization following long bone fractures.
A careful history of the events surrounding the death of the donor is important. Any blunt or penetrating chest trauma which could lead to direct lung injury should be noted, in addition to any long bone or pelvic fractures which might cause injury secondary to fat emboli. Closed head injury alone has been associated with up to a 40% incidence of pneumonia within the first week after intubation, most occurring within the first three days.72 Thus, the duration of intubation is a critical historical factor, but would not independently exclude the use of an otherwise acceptable organ. Any history of aspiration noted at the time of intubation and resuscitation must be considered in the context of the chest xray, sputum gram stain, bronchoscopy, and functional assessment.
A history of significant pulmonary disease likely to effect function and long term organ durability or any prior thoracic (not cardiac) surgery should preclude lung donation. While lungs with a history of prior granulomatous disease have been successfully transplanted, we feel that the risk of reactivation of the disease with immunosuppressive therapy is too risky. However, a history of asthma or mild reactive airway disease easily controlled on low doses of bronchodilators is not a contraindication to lung transplantation. Patients requiring steroids for control of asthma should be excluded. Similarly, tobacco smoking with a normal chest x-ray, bronchoscopy, lung function and mechanics, does not preclude lung transplantation.
Obtaining serial chest radiographs every 6-8 hours during the period of onsite donor management and within 2 hours of organ procurement is recommended.73-75 Serial chest radiographs are reviewed initially by a radiologist or pulmonologist on site at the donor hospital and then by the donor surgeon looking for signs of atelectasis, pulmonary infiltrates (suggesting pneumonia or aspiration), pulmonary edema, contusion, or other pulmonary abnormalities. The presence or de
velopment of an infiltrate would strongly influence the decision against the use of the specific lung. In situations where the infiltrate is thought to be secondary to aspiration, use of both lungs would be in question. In some circumstances, such as a pulmonary contusion, the affected lung may still be used. Similarly, if the infiltrate is thought to be related to pulmonary edema, diuresis can be attempted to aid in salvaging the donor organs. Some of these earlier guidelines have been recently expanded, and less than optimal donors have been utilized to combat the severe shortage of available organs.9 The chest radiograph is also useful for size-matching the recipient and donor as previously discussed. Ventilation mechanics
An assessment of the static compliance of the donor lungs should made to assure normal lung mechanics. This usually means a peak airway pressure (PAP) of less than 25 cm H2O using a tidal volume (TV) of 10-15 mL/kg and 5 cm of PEEP. Evidence for reduced static compliance (evidenced by higher PAP with adequate TV) may indicate atelectasis or airway obstruction caused by secretions which can usually be corrected. If it cannot be corrected this suggests either acute (aspiration, pneumonia, pulmonary edema, etc.) or chronic intrinsic lung disease, a strong contraindication for transplantation. Gas exchange
The key element in the assessment of the potential lung donor is the adequacy of gas exchange. Oxygenation as defined as the partial pressure of oxygen (paO2) of the donor should be greater than 300 mm Hg immediately prior to procurement on ventilator settings which include a FO of 1.0, a tidal volume of 10-15 mL/kg, and a PEEP of 5 cm H2O. Serial determinations are important during the donor assessment period to assist in recognizing unfavorable trends in pulmonary function. The partial pressure of CO2 is given less emphasis but should reflect adequate ventilation parameters. Bronchoscopy
Bronchoscopy is performed in all donors to detect the presence of occult aspiration as well as anatomical or pathological abnormalities that would preclude organ utilization. This may be performed by a pulmonologist, intensivist, or thoracic surgeon during the preliminary evaluation phase, but should always be repeated by the donor surgeon at the time of organ procurement. The finding of either endobronchial secretions that cannot be cleared by suctioning or diffuse erythema of the bronchial mucosa indicates aspiration, which usually precludes lung procurement.
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