ESOT 2011 Report – Donation after cardiac death: Can hearts be successfully reanimated?

The success of organ donation after cardiac death (DCD) has yet to extend into cardiac transplantation although it is felt that rescuing hearts from donors after cardiac death would allow significant expansion of the donor pool. The study by Dr A. Muhammad and colleagues from the UK used an ex vivo circuit to reperfuse porcine hearts in a simulated DCD model with the aim of restoring myocardial activity, testing various combinations of both established and novel perfusion solutions.

Dr A. Muhammad and colleagues used eleven cross-Yorkshire Landrace pigs (mean weight 29.4±5.7 kg) that were euthanased humanely. The non-beating hearts were procured after being subjected to 10 minutes of warm ischaemia. All eleven hearts underwent initial antegrade flush with 250mls of AQIX® RS-I solution (a novel non-phosphate pH buffered preservation solution) at ambient room temperature. Hearts numbered 3 to 11 were flushed with a further 250mls of either cold AQIX® RS-I (n=6) or cold University of Wisconsin (UW) solution (n=3). Static cold storage was in either AQIX® RS-I (n=6) or UW solution and this was achieved in 5 hearts. Reperfusion was performed on a Langendorff modification of Model 30 Functional Circulation Circuit, using a mixture of heparinised, leukocyte-depleted blood and AQIX® RS-I solution. Drugs administered included adrenaline, calcium gluconate and dopamine and DC cardioversion were used to initiate left ventricular activity, which was measured by ultrasonic probes on the left ventricular outflow.

The researchers found that hearts sourced from DCD donors can be successfully reanimated. The important factors influencing successful reanimation included adequate coronary flush, administration of adrenaline and DC cardioversion. Restoration of cardiac activity was achieved using both a conventional (UW) and novel perfusion solution (AQIX® RS-I). The researchers concluded that further studies are needed before hearts procured from DCD donors can be incorporated into mainstream cardiac donation. However this was a successful start to amassing a body of evidence in this area.

 

Omar A. Mownah and colleagues from the UK continued on a similar theme and presented data on using dialysis for prolonged ex vivo warm reperfusion of DCD hearts. It is documented that ex vivo reperfusion of organs sourced from DCD offers the possibility of restoring organ function. However, prolonged reperfusion with warm blood can introduce waste metabolites and electrolyte imbalance into the ex vivo circuit. This potentially adversely affects the health of the organ and the success of the procedure.

Omar A. Mownah explained that following 10 minutes of warm ischaemia, six porcine hearts were flushed and preserved using oxygenated, hypothermic machine perfusion for 2-4 hours. Subsequent warm blood (heparinised and leukocyte-depleted) reperfusion took place on an ex vivo circuit, with Aqix RS-I® (a novel perfusion solution) added to provide an adequate circulating volume.

A dialysis circuit was fashioned using a filter (Fresenius FX8 Capillary Dialyzer®) and two roller-pumps. This was placed in parallel with the reperfusion circuit.

Circulating blood was diverted, using a pump, to the filter whilst dialysate was simultaneously pumped to run counter to the blood, allowing diffusion to occur. Blood was sampled for real-time acid/base and biochemical analysis.

The Fresenius A/5® dialysate used lacks phosphate due to its design for use with chronic renal failure patients. Therefore, phosphate was added to the dialysate.

Dialysate composition

	Composition of dialysate		Composition of dialysate
	(mmol/L)		(mmol/L)
Na+	138.0	HCO3–	35.0
K+	2.00	Cl–	105.5
Ca2+	1.25	CH3COO–	3.0
Mg2+	0.50	Glucose	1.0 g/L
Osmolality	291 mosm/L

The results of the study showed that after the commencement of dialysis at T2, potassium and lactate levels were rapidly corrected. Dialysis was also seen to maintain arterial blood acid/base balance.

The researchers concluded, “Our dialysis circuit corrected potassium disturbance while rapidly reducing lactate levels. Our previous work has demonstrated that preservation followed by reperfusion is a technique which, when applied to a DCD-sourced heart, may lead to functional recovery and reanimation. Prolonged reperfusion, which may be necessary to achieve reanimation, would benefit from the dialysis technique we have described in order to protect the reperfusing organ from the deleterious effects of electrolyte and acid/base disturbance, as well as lactate accumulation.”

References:

RO-152 – DONATION AFTER CARDIAC DEATH: CAN HEARTS BE SUCCESSFULLY REANIMATED? Muhammad A. Khurram et al. Newcastle and Sunderland, UK

RO-153 – USING DIALYSIS FOR PROLONGED EX VIVO WARM REPERFUSION OF DCD HEARTS Omar A. Mownah et al. Newcastle and Sunderland, UK