The rate of organ donation continues to be insufficient to meet the increasing demand for donor hearts. One of the main steps proposed to improve procurement and transplant activity is education of the general public and health care professionals. As such, an ongoing training program for health care professionals should be present in every medical institution to improve the identification and management of potential donors using standardized protocols (16
). The importance of organ donation, signing donor cards and discussing one’s organ donation wishes with family members are key components in the education of the public.
The United Network for Organ Sharing (USA) reported only a 42% donor yield in 1998 (19
). In Canada, similar donor yields have been reported, with a heart donation yield as low as 39% (20
). Clinical efforts to improve donor management have traditionally focused on hemodynamics. The overall goals are to achieve euvolemia, to adjust vasoconstrictors and vasodilators to maintain normal afterload, and to optimize cardiac output without relying on high doses of inotropes, which increase myocardial oxygen demand. Although echocardiography is effective in screening for anatomical abnormalities of the heart, the use of a single echocardiogram to determine the physiological suitability of a donor is not always sufficient. In fact, serial echocardiography may be necessary to evaluate resuscitation efforts to rescue organs and allow for their use (19
). The Papworth Hospital transplant program in Great Britain has been a pioneer in the field of resuscitating donor hearts. The donor yield was increased substantially by using a PA catheter to guide physiological assessment and management of ventricular dysfunction (21
). The investigators suggested an aggressive approach to donor management including invasive monitoring with PA catheters and onsite resuscitation under the guidance of an experienced cardiac intensivist. More recent work from the same group has been aimed at developing tools to identify subclinical right ventricular (RV) dysfunction present in donor hearts, a condition that is well known to adversely affect transplant outcomes (22
The importance of hormonal resuscitation in increasing donor yield has become clear and was the focus of a recent consensus conference report on improving organ donation (18
). Hormonal resuscitation consisting of donor infusions of combined glucose, insulin and potassium, triiodothyronine, cortisol and arginine vasopressin have been shown to reduce donor inotropic requirements and improve recipient outcome following transplantation, and were recommended in a recent consensus statement (19
- Hormonal replacement for potential cardiac donors (grade B, level 2).
- ○ Triiodothyronine: 4 μg bolus then continuous infusion at 3 μg/h.
- ○ Arginine vasopressin: 1 U bolus then continuous infusion at 0.5 U/h to 4 U/h (titrate to systemic vascular resistance of 800 dyn•s/cm5 to 1200 dyn•s/cm5.
- ○ Methylprednisolone: 15 mg/kg bolus.
- ○ Insulin: 1 U/h (titrate to maintain blood sugar of 6 nmol/L to 10 nmol/L).
Recipient status and donor allocation
When patients have been listed for transplantation, they are assigned a listing status according to their disease stability and the likelihood of survival without transplantation. Status criteria have been developed by the Canadian Cardiac Transplant Network (CCTN) for listing of cardiac transplant recipients across the country (25
). The highest priority patients (status 4) are those who are mechanically dependent (on mechanical circulatory support or ventilatory support) and intensive care unit-dependent. Status 3.5 patients are those on high-dose or multiple inotropes in the hospital, highly sensitized patients and those with acute refractory life-threatening arrhythmias. Status 3 patients include those with ventricular assist devices (VADs) in the absence of complications, patients on single, low-dose inotropes in the hospital, adult congenital heart disease patients who are arterial shunt-dependent or who have a resting oxygen saturation of less than 65%, and those with complex congenital heart disease and increasing dysrhythmic or systemic ventricular decline. Heart and lung recipients are also status 3. In-hospital patients, patients on outpatient inotropic therapy and adult congenital patients with a resting oxygen saturation of 65% to 75% or those with Fontan palliation and protein-losing enteropathy, as well as patients listed for multiple organ transplantation (other than heart and lung) are considered status 2. All other out-of-hospital patients are considered status 1.
The CCTN has endorsed and formalized a system whereby donor hearts are allocated nationwide to the patients most in need of transplantation. A nationwide list is distributed to all organ procurement organizations (OPOs) across Canada, on which patients are identified according to their listing status. The principle of the organ-sharing agreement, as outlined by the CCTN, is as follows (25
The OPO will offer the donor heart to the Canadian site with the highest status recipient in the geographic area. The OPO will also notify the Canadian program(s) with a potentially appropriate Status 4 recipient(s) nationwide of the potential donor heart. If there are competing potential recipients, mandatory discussion in a timely fashion, physician to physician, will ensue to allocate the organ, the principle being that the recipient with the longest current listing as Status 4 be given priority. If consensus is not reached, final allocation will be made by the center to which the heart was originally offered.
All out-of-country donor hearts will be offered nationally to all programs with eligible Status 4 recipients. If there are competing Status 4 candidates, mandatory discussion is required in a timely manner, physician to physician, prior to allocation of the donor heart. If consensus is not reached, final allocation will be made by the centre with the recipient with the longest current listing time as Status 4.