Fast track — ArticlesTransplantation of lungs from a non-heart-beating donor
Introduction
The possibility of transplanting lungs from fresh non-heart-beating cadavers (eg, patients who have had a witnessed cardiac arrest due to ischaemic heart disease) has been the subject of much discussion.1 Experimental studies have shown that the lungs and their vascular function can be safely preserved for up to 24 h;2, 3 that the gas-exchange system of the lungs can tolerate 1 h of warm ischaemia after circulatory arrest without significant loss of its functional capacity;4, 5 and that the pulmonary artery can withstand warm ischaemia for 3 h after death without impairment of endothelium-dependent relaxation or vascular smooth-muscle function.6 Furthermore, simple topical cooling of nonventilated lungs gives excellent preservation for 12–24 h.7
We have previously transplanted animal lungs from non-heart-beating donors in simulated clinical situations in which the lungs were first topically cooled in the non heart-beating cadaver after failed resuscitation.8, 9, 10 However, if lungs from patients dying of acute myocardial infarction are to serve as donor organs in clinical lung transplantation, their function must be properly assessed first. In cooperation with Vitrolife AB (Gothenburg, Sweden), we have developed a lung-function assessment solution which, when mixed with red cells to a packed-cell volume of 10–20%, permits perfusion of lungs ex vivo for several hours without development of oedema (figure 1). By supplying nitrogen, carbon dioxide, and oxygen to the oxygenator, venous blood gases can be simulated in the solution. During ventilation of the lungs with gases of different inspired oxygen fractions, the blood gases analysed in the solution taken from the left atrial cannula will show the gas-exchange capacity of the lungs. Measurement of the endtidal carbon dioxide concentration and comparison of that value with the arterial carbon dioxide concentration, ventilation-perfusion discrepancies (eg, those due to pulmonary emboli) can be detected. By clamping one hilus with a vascular clamp, each lung can be assessed individually. Vascular function can be judged by observing the effect on the pulmonary vascular resistance of a gradual increase in the proportion of nitric oxide in the inhalation gas; the greater the effect of nitric oxide on pulmonary vascular resistance, the more impaired the endothelium-dependent relaxation.11
The results of our animal experiments and studies on ex-vivo assessment of lung function convinced us that it should be possible to transplant lungs from non-heart-beating donors to live recipients, provided an ethically acceptable method of cooling the lungs within 1 h of death could be found. Here we report the methods used to ascertain what constitutes ethical acceptability in these circumstances, and the results of our experience with the first non-heart-beating lung donor and recipient.
Section snippets
Preliminary investigations
At the beginning of 1997, we started to prepare for a clinical study. We asked doctors, nurses, hospital chaplains, judges, teachers, philosophers, theologians, and ordinary citizens across Sweden about how lungs could be transplanted from a non-heart-beating donor. From this consultation, we learned that any type of surgery on a dead body within 1 h of death was ethically unsound, but that if topical cooling of the lungs could be accomplished without leaving scars, then the planned procedure
Results
A ventilation-perfusion scintigram of the recipient showed no great mismatch; the right lung had 51% and the left lung 49% of the ventilation. Right lung transplantation was done. The phrenic nerve had adhered to the teflon reinforced staple line after the lung-volume reduction surgery, and had to be carefully dissected free. There were also strong adherences between the lung and the diaphragm. Otherwise the transplantation was not difficult, and did not require extracorporeal circulation. The
Discussion
The lung is unique among the vital organs owing to its tolerance of warm ischaemia. When acute cardiac arrest occurs, the vasculature of the lung is filled with blood saturated with oxygen to 70–100%, and the airways are filled with air (or with 100% oxygen if the person has been resuscitated). Normally the alveolocapillary membrane gets its nutrition by direct diffusion. The lung consists mainly of elastic tissue with a low metabolic requirement and its function is retained for up to an hour
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