Cardiac organ donor management

Abstract

There is a critical shortage of donor organs. According to the United Network for Organ Sharing (UNOS), 20% of organs are discarded after procurement. Many of these may be potentially salvageable. Brain death is particularly detrimental to cardiac function. The initial sympathetic storm can produce direct myocardial injury. The ensuing spinal shock reduces global oxygen delivery. There is a change to anaerobic metabolism due to global mitochondrial dysfunction. Diabetes insipidus worsens hypovolemia and thyroid deficiency impairs cardiac function. Inadequate replacement of blood loss from trauma and coagulopathy worsens anemia and oxygen delivery. In the mid-1990s, the Papworth Hospital group in the UK advocated early invasive hemodynamic monitoring and administration of a 'hormonal cocktail', consisting of triiodothyronine (T3), vasopressin, methylprednisolone and insulin. This has been widely accepted and is endorsed by UNOS. Ventricular function, volume status and adequacy of resuscitation should be guided by invasive monitoring and serial echocardiography. Dopamine or epinephrine is used for inotropic support. If hypotension persists, vasopressin should be added which may allow reduction of inotropes. Donor lung function and ventilation should be optimized. Recently, two large retrospective studies have shown that, with aggressive pharmacological and hormonal resuscitation, a significant increase in the number and quality of organs harvested can be achieved.

Brain Death: Assessment, Controversy, and Confounding Factors

“…Continued increases in pressure then may lead to transtentorial (central) herniation syndromes with distortion of the posterior fossa and brain stem displacement through the foramen magnum. 13,[17][18][19][20] The Cushing response, due to pressure or ischemia on the pons, is considered a reflex response to maintain brain perfusion in patients with elevated ICPs and is characterized by hypertension, bradycardia, and widened pulse pressure. 20 Progression of ischemia or distortion of the medulla oblongata and hypothalamus results in additional sympathetic outflow as endogenous catecholamine stores are released, causing hypertension, tachycardia, and vasoconstriction in an effort to maintain cerebral perfusion pressure.…”

Management of Neuroendocrine Instability During Maintenance of Potential Organ Donors

“…The most important endocrine disturbances are a reduction in anti-diuretic hormone secretion, thyroid dysfunction, reduction in adenocorticotrophic hormone and insulin levels (Ullah et al 2006). In experimental animal models of brain death, the pituitary gland hormones vasopressin and adenocorticotrophic hormone decreased significantly after 15 and 45 minutes of brain death respectively (Bittner et al 1995).…”

“…It has been defined "sick euthyroid syndrome" and has also been described in cardiopulmonary by-pass. It is postulated that proinflammatory cytokines may play a role in inhibiting the conversion of thyroxine to the active form of thyroid hormone, and instead, convert it to the non-active form, reverse-thyroid hormone (Ullah et al 2006). In an animal model of brain death, Novitzky et al showed that levels of thyroid hormones were severely depleted (Novitzky et al 1988).…”

“…Therefore, there is still a considerable debate whether the sick euthyroid syndrome requires treatment. Insulin levels fall after brain stem death, leading to a decrease in intracellular glucose concentration, the development of an cellular energy deficit, and a shift toward anaerobic metabolism and acidosis (Ullah et al 2006). In brain dead patients there is also a significant decreases in cortisol levels that, in association with decreases in thyroid hormone, may contribute to the cardiovascular instability.…”

“…In severe acute brain injury patients evolving to brain death, hypothalamic-pituitary-adrenal insufficiency occurs in 30-50% (Behan et al 2008;Corneli et al 2007) of patients and a high prevalence of neuroendocrine deficiency is present in brain dead patients (Howlett et al 1989;Salim et al 2006). These endocrine alterations lead to metabolic abnormalities and hemodynamic instability with deleterious effects on these potential organ donors (Ullah et al 2006). Adequate organ donor management is therefore mandatory to prevent, reduce or reverse these alterations and to maintain the functional integrity of potentially transplantable organs.…”