A Kanwar

Development of an ex vivo technique to achieve reanimation of hearts sourced from a porcine donation after circulatory death model

BACKGROUND This study reports on the development of a novel method for achieving ex vivo reanimation of hearts from a porcine donation after circulatory death (DCD) model without the use of donor pretreatment. METHODS Porcine hearts (n = 23) were procured 10-29 min after confirmation of asystole. All hearts underwent initial flush with AQIX RS-I solution (London, UK). A 2-h preservation period followed: group 1 hearts (n1-n11) were preserved using static cold storage, group 2 hearts (n12-n17) were preserved using oxygenated, hypothermic machine perfusion (MP), and group 3 hearts (n18-n23) were subjected to retrograde oxygen persufflation. Reperfusion was performed on a Langendorff modification of a Model 33 Functional Circulation circuit. In hearts n16-n23, a dialysis circuit was incorporated into the circuit to facilitate removal of metabolites. The experimental protocol was allowed to follow an evolutionary course, with the aim of achieving greater success with reanimation. RESULTS In group 1 (static cold storage), 7 of the 11 hearts (63.6%) achieved reanimation on the ex vivo circuit. Two of the six hearts (33.3%) in group 2 (MP) were successfully reanimated. All the six hearts (100%) in group 3 (persufflation) were successfully reanimated. The period of sustained reanimation increased when dialysis was incorporated into the circuit with a maximum of 300 min. CONCLUSIONS Porcine DCD hearts after 29 min of warm ischemia can be reanimated using the method described. A mechanism of reoxygenation (oxygenated MP or coronary sinus oxygen persufflation) during preservation appears mandatory for hearts from DCDs. Persufflation was associated with a higher probability of successful reanimation. Dialysis in the warm phase was useful in removing metabolites that could interfere with reanimation. The results demonstrate the potential of DCDs to counter the decline affecting heart transplantation.

Porcine Model of Extra-Corporeal Membrane Oxygenation (ECMO) in the Uncontrolled Non-Heart Beating Donor; the Effect on Renal Viability

In response to the novel technique to secure the aorta in donation after cardiac death, described by Mateo et al. [1] in December 2008, we write with a note of caution. We read with great interest the method of employing commercially available cable ties to secure the aorta, for organ perfusion in DCD donors. The technique aims to create a simple, rapid technique to secure an aortic cannula and thereby minimize the warm ischaemic time. After mobilizing and isolating the aorta in standard fashion, the cable tie is passed around a section of the aorta, proximal to the planned site of arteriotomy. Once the aortotomy is performed and the cannula has been placed in the desired position, the cable tie is tightened to secure the cannula in place. The benefits of this technique, described by Mateo, seemed clear. It is rapid, secure and simple. It has the added benefit of secure control of atherosclerotic vessels – where nylon ties have been noted to fracture vessel walls. We decided to undertake a trial of this technique in our current research model assessing the benefits of extra-corporeal membrane oxygenation (ECMO), over combined intra-vascular and -peritoneal cooling in a porcine model of donation-after-cardiac death. In both comparison groups we cannulated the aorta and vena cava at an initial laparotomy. The aortic cannula was employed to administer the ECMO or arterial cooling and flush. In an alteration to the technique employed by Mateo, we used a commercially available cable tie gun (Fig. 1) to secure the tie and tighten it down. Once the tie had been positioned around the aorta, the tip of the tie was passed through the ratcheted head and the tie loosely tightened down around the vessel. After performing the aortotomy and positioning the cannula, the gun was used to rapidly and securely tighten the cable-tie around the vessel and cannula (Fig. 2). The loose end of the tie can be cut when desired by firing an additional trigger on the gun. The major drawback of this technique, as we later discovered, is that use of the cable tie gun leads to a loss in tactile feedback. The cable tie can therefore be easily over tightened and constrict the cannula within the aorta. On commencing our ECMO bypass circuit, we immediFigure 2 Application of cable-tie to secure the aortic cannula, using a cable-tie gun. Figure 1 Commercially available cable-tie gun.

Poor Perfusion of Retrieved Kidneys from Non-Heart Beating Donors: The Impact of Machine Perfusion

In response to the novel technique to secure the aorta in donation after cardiac death, described by Mateo et al. [1] in December 2008, we write with a note of caution. We read with great interest the method of employing commercially available cable ties to secure the aorta, for organ perfusion in DCD donors. The technique aims to create a simple, rapid technique to secure an aortic cannula and thereby minimize the warm ischaemic time. After mobilizing and isolating the aorta in standard fashion, the cable tie is passed around a section of the aorta, proximal to the planned site of arteriotomy. Once the aortotomy is performed and the cannula has been placed in the desired position, the cable tie is tightened to secure the cannula in place. The benefits of this technique, described by Mateo, seemed clear. It is rapid, secure and simple. It has the added benefit of secure control of atherosclerotic vessels – where nylon ties have been noted to fracture vessel walls. We decided to undertake a trial of this technique in our current research model assessing the benefits of extra-corporeal membrane oxygenation (ECMO), over combined intra-vascular and -peritoneal cooling in a porcine model of donation-after-cardiac death. In both comparison groups we cannulated the aorta and vena cava at an initial laparotomy. The aortic cannula was employed to administer the ECMO or arterial cooling and flush. In an alteration to the technique employed by Mateo, we used a commercially available cable tie gun (Fig. 1) to secure the tie and tighten it down. Once the tie had been positioned around the aorta, the tip of the tie was passed through the ratcheted head and the tie loosely tightened down around the vessel. After performing the aortotomy and positioning the cannula, the gun was used to rapidly and securely tighten the cable-tie around the vessel and cannula (Fig. 2). The loose end of the tie can be cut when desired by firing an additional trigger on the gun. The major drawback of this technique, as we later discovered, is that use of the cable tie gun leads to a loss in tactile feedback. The cable tie can therefore be easily over tightened and constrict the cannula within the aorta. On commencing our ECMO bypass circuit, we immediFigure 2 Application of cable-tie to secure the aortic cannula, using a cable-tie gun. Figure 1 Commercially available cable-tie gun.