Intraoperative Management

Increasingly, anesthesiologists are being asked to manage organ donors during organ retrieval. Organ retrieval is not performed solely at major medical centers. Indeed, most organ retrievals are performed at small hospitals with no academic affiliation. Hence, any anesthesiologist may be confronted with a brain-dead patient and the attendant pathophysiologic perturbations. Furthermore, the logistics of harvesting organs, social circumstances (interaction with relatives of the potential organ donor), and the unusual sequence of intraoperative events may appear intimidating to the anesthesiologist.

Cessation of cerebral function will invariably result in a sequence of pathophysiologic changes leading to death of the potential organ donor within a few days unless appropriate intervention is undertaken. At the same time, it may take several days for identification of a possible organ donor, declaration of brain death, consent,

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After an initial hyperdynamic response consisting of hypertension, brain-dead patients brought to the operating room for organ retrieval experience hypotension, reduced cardiac output, myocardial dysfunction,^[19] and decreased systemic vascular resistance. In addition, diminished oxygenation as a result of neurogenic pulmonary edema and diabetes insipidus secondary to decreased circulating levels of antidiuretic hormone may be observed. The latter, in turn, may also lead to hypernatremia and hypokalemia. Hyperglycemia, coagulopathy, and hypothermia may be encountered and must be corrected when severe. The therapeutic response will be determined by which organs are being retrieved because therapy may have an impact on organ viability.

Certain guidelines^[20] can be summarized as follows:

• Systolic blood pressure >100 mm Hg (mean, 70 to 110 mm Hg)

• PO₂ >100 mm Hg

• Urine output >100 mL/hr (1 to 1.5 mL/kg/hr)

• Hemoglobin concentration >100 g/L

• Central venous pressure (CVP) between 5 and 10 mm Hg

• FIO₂ <40% (if tolerated) for lung retrieval

To achieve these goals, the anesthesiologist should use standard monitors, measure urine output, and use invasive measurements of arterial pressure and CVP (frequently with a pulmonary artery catheter). The first response in the treatment of hypotension should be administration of fluid. A mixture of crystalloid and colloid solutions, as well as occasional administration of blood, will most rapidly correct hypovolemia with the goal of increasing urine output. For lung and pancreas transplant retrieval, colloids are preferred over crystalloids. Frequent communication with the surgical team regarding volume replacement is essential. Excessive fluid administration may result in swelling and even loss of the organ. To decontaminate the intestines for retrieval of the pancreas, a mixture of povidone-iodine (Betadine), amphotericin, and normal saline is administered through an orogastric/nasogastric tube. Should pharmacologic support of the circulation be necessary, the inotrope of choice is commonly dopamine; however, other cardiovascular drugs such as norepinephrine, epinephrine, vasopressin, and dobutamine may need to be added to maintain hemodynamic stability during the latter stages of organ dissection and harvest. Surgical techniques may vary depending on whether the procedure is single- or multiple-organ recovery. ^[18] In general, wide exposure of the surgical field is established, cannulas are placed for in situ perfusion, and the organs to be removed are isolated with preservation of their central vascular structures. Heparin is administered (approximately 20,000 to 30,000 IU) when requested by the harvest team. If harvest of the heart or lung is anticipated, pulmonary artery catheters or central venous catheters will need to be pulled back before cross-clamping. If lung recovery is anticipated, the lungs are ventilated well beyond cross-clamping and initiation of organ harvest other than the lung. Removal of the organs is performed under cold protection by applying ice to the surgical field. Organs are removed according to their susceptibility to ischemia, with the heart first and the kidney last in a multiorgan donor. Excellent communication between the frequently different surgical teams (e.g., abdominal organ team versus thoracic organ team) and the anesthesiologist is critical to ensure optimal organ quality.^[18]

Vasodilators such as phentolamine or alprostadil (lung recovery) may be administered during cross-clamping with the goal of decreasing systemic vascular resistance and allowing even distribution of the preservation solution. Long-acting nondepolarizing muscle relaxants should be used for optimal intra-abdominal and intrathoracic exposure. Clinically significant bradycardia in brain-dead patients will not respond to atropine, so a direct-acting chronotrope such as isoproterenol must be readily available. Patients declared brain-dead do not have pain perception, and hence analgesia is not required. However, volatile anesthetics or narcotics may nonetheless be used to facilitate hemodynamic stability. The changes in heart rate and blood pressure that may occur with surgical stimulation are the result of intact spinal reflexes. Although these hemodynamic changes can often be easily controlled with vasoactive agents alone, the anesthesiologist is probably most comfortable responding to these changes by increasing the amount of volatile anesthetics.

Frequently, the anesthesiologist is asked to draw blood for several pretransplant tests. The volume may vary in different organ procurement organizations but is generally between 60 and 200 mL in adults.