Background.Strategies to minimize ischemic damage during heart transplantation (HTX) by donation after circulatory death (DCD) are warranted because the inevitable ischemic injury linked to DCD HTX deteriorates mitochondrial respiratory capacity and ultimately graft quality. This study aimed to examine the myocardial mitochondrial function during DCD HTX with hypothermic oxygenated machine perfusion (HOPE) and compare the effect of normothermic regional perfusion (NRP) with that of direct procurement and perfusion (DPP).Methods.A porcine DCD HTX model was used with hearts subjected to either DPP (n = 6) or NRP (n = 7) followed by HOPE and orthotopic HTX. Mitochondrial respiratory function was analyzed by high-resolution respirometry in left ventricle biopsies at baseline, after 180 min of HOPE, and after 60 min of reperfusion post-HTX.Results.Mitochondrial oxidative phosphorylation (P = 0.0008), respiratory control ratio (P = 0.04), and coupling efficiency (P = 0.04) declined during DCD HTX. Fatty acid oxidation was preserved after 3 h of HOPE with a modest, statistically nonsignificant decline after reperfusion (P = 0.2). Oxidative phosphorylation was inversely correlated with troponin-T levels (r = -0.70, P = 0.0004). No statistically significant difference in mitochondrial respiratory capacity was observed between participants exposed to NRP and DPP.Conclusions.Mitochondrial respiratory capacity declined gradually throughout the course of DCD HTX and correlated with the degree of myocardial damage. Following HOPE, the extent of mitochondrial deterioration was comparable between NRP and DPP.

BACKGROUND:Butyrate, a short-chain fatty acid, has shown potential to improve left ventricular (LV) function and induce vasorelaxation in rodents. Butyrate may either be produced by the microbiome in the colon, be ingested or administered intravenously. This study aimed to evaluate effects of butyrate on cardiac output (CO) and associated hemodynamic variables in a porcine model. METHODS:In a randomized, blinded crossover study, ten healthy 60-kg pigs were given three hour infusions of 600 mM butyrate and equimolar sodium chloride (control). CO was measured by thermodilution via a pulmonary artery catheter. LV contractility was assessed using pressure-volume admittance catheterization. Additionally, isolated porcine coronary arteries were exposed to butyrate in a wire myograph to evaluate vasorelaxation. RESULTS:Butyrate infusion increased plasma butyrate concentration to 0.53 mM (95 % confidence interval (CI): 0.49 to 0.58 mM, P < 0.58 mM, P < 0.001) and CO by 1.6 L/min (95 % CI: 1.0 to 2.1 L/min, P < 0.001) compared with the control. Heart rate, LV ejection fraction, cardiac efficiency and dP/dtmax rose, while systemic vascular resistance, arterial elastance, mean arterial pressure and LV end-systolic volume decreased. Load-independent LV contractility and stroke volume did not significantly differ. In the myograph, porcine coronary arteries relaxed in response to butyrate in a concentration-dependent manner. CONCLUSION:Butyrate increases cardiac output and lowers vascular resistance in a large animal model, through increased HR and systemic vasorelaxation. Load-independent LV contractility was not significantly altered. We observed indices of increased end-organ perfusion. These potentially beneficial cardiovascular properties of butyrate should be further studied.

The aim was to establish combined H215O PET/MRI during ex vivo normothermic machine perfusion (NMP) of isolated porcine kidneys. We examined whether changes in renal arterial blood flow (RABF) are accompanied by changes of a similar magnitude in renal blood perfusion (RBP) as well as the relation between RBP and renal parenchymal oxygenation (RPO). Methods: Pig kidneys (n = 7) were connected to a NMP circuit. PET/MRI was performed at two different pump flow levels: a blood-oxygenation-level-dependent (BOLD) MRI sequence performed simultaneously with a H215O PET sequence for determination of RBP. Results: RBP was measured using H215O PET in all kidneys (flow 1: 0.42–0.76 mL/min/g, flow 2: 0.7–1.6 mL/min/g). We found a linear correlation between changes in delivered blood flow from the perfusion pump and changes in the measured RBP using PET imaging (r2 = 0.87). Conclusion: Our study demonstrated the feasibility of combined H215O PET/MRI during NMP of isolated porcine kidneys with tissue oxygenation being stable over time. The introduction of H215O PET/MRI in nephrological research could be highly relevant for future pre-transplant kidney evaluation and as a tool for studying renal physiology in healthy and diseased kidneys.

Background Lactate is traditionally recognized as a by-product of anaerobic metabolism. However, lactate is a preferred oxidative substrate for stressed myocardium. Exogenous lactate infusion increases cardiac output (CO). The exact mechanism underlying this mechanism has yet to be elucidated. The aim of this study was to investigate the cardiovascular mechanisms underlying the acute haemodynamic effects of exogenous lactate infusion in an experimental model of human-sized pigs. Methods In this randomised, blinded crossover study in eight 60-kg-pigs, the pigs received infusions with one molar sodium lactate and a control infusion of tonicity matched hypertonic saline in random order. We measured CO and pulmonary pressures using a pulmonary artery catheter. A pressure–volume admittance catheter in the left ventricle was used to measure contractility, afterload, preload and work-related parameters. Results Lactate infusion increased circulating lactate levels by 9.9 mmol/L (95% confidence interval (CI) 9.1 to 11.0) and CO by 2.0 L/min (95% CI 1.2 to 2.7). Afterload decreased as arterial elastance fell by -1.0 mmHg/ml (95% CI -2.0 to -0.1) and systemic vascular resistance decreased by -548 dynes/s/cm 5 (95% CI -261 to -835). Mixed venous saturation increased by 11 percentage points (95% CI 6 to 16), whereas ejection fraction increased by 16.0 percentage points (95% CI 1.1 to 32.0) and heart rate by 21 bpm (95% CI 8 to 33). No significant changes in contractility nor preload were observed. Conclusion Lactate infusion increased cardiac output by increasing heart rate and lowering afterload. No differences were observed in left ventricular contractility or preload. Lactate holds potential as a treatment in situations with lowered CO and should be investigated in future clinical studies. Graphical Abstract

Background The ketone body 3‐hydroxybutyrate (3‐OHB) increases cardiac output (CO) by 35% to 40% in healthy people and people with heart failure. The mechanisms underlying the effects of 3‐OHB on myocardial contractility and loading conditions as well as the cardiovascular effects of its enantiomeric forms, D‐3‐OHB and L‐3‐OHB, remain undetermined. Methods and Results Three groups of 8 pigs each underwent a randomized, crossover study. The groups received 3‐hour infusions of either D/L‐3‐OHB (racemic mixture), 100% L‐3‐OHB, 100% D‐3‐OHB, versus an isovolumic control. The animals were monitored with pulmonary artery catheter, left ventricle pressure‐volume catheter, and arterial and coronary sinus blood samples. Myocardial biopsies were evaluated with high‐resolution respirometry, coronary arteries with isometric myography, and myocardial kinetics with D‐[ 11 C]3‐OHB and L‐[ 11 C]3‐OHB positron emission tomography. All three 3‐OHB infusions increased 3‐OHB levels ( P <0.001). D/L‐3‐OHB and L‐3‐OHB increased CO by 2.7 L/min ( P <0.003). D‐3‐OHB increased CO nonsignificantly ( P =0.2). Circulating 3‐OHB levels correlated with CO for both enantiomers ( P <0.001). The CO increase was mediated through arterial elastance (afterload) reduction, whereas contractility and preload were unchanged. Ex vivo, D‐ and L‐3‐OHB dilated coronary arteries equally. The mitochondrial respiratory capacity remained unaffected. The myocardial 3‐OHB extraction increased only during the D‐ and D/L‐3‐OHB infusions. D‐[ 11 C]3‐OHB showed rapid cardiac uptake and metabolism, whereas L‐[ 11 C]3‐OHB demonstrated much slower pharmacokinetics. Conclusions 3‐OHB increased CO by reducing afterload. L‐3‐OHB exerted a stronger hemodynamic response than D‐3‐OHB due to higher circulating 3‐OHB levels. There was a dissocitation between the myocardial metabolism and hemodynamic effects of the enantiomers, highlighting L‐3‐OHB as a potent cardiovascular agent with strong hemodynamic effects.

Normothermic regional perfusion (NRP) allows assessment of therapeutic interventions prior to donation after circulatory death transplantation. Sodium-3-hydroxybutyrate (3-OHB) increases cardiac output in heart failure patients and diminishes ischemia–reperfusion injury, presumably by improving mitochondrial metabolism. We investigated effects of 3-OHB on cardiac and mitochondrial function in transplanted hearts and in cardiac organoids. Donor pigs (n = 14) underwent circulatory death followed by NRP. Following static cold storage, hearts were transplanted into recipient pigs. 3-OHB or Ringer’s acetate infusions were initiated during NRP and after transplantation. We evaluated hemodynamics and mitochondrial function. 3-OHB mediated effects on contractility, relaxation, calcium, and conduction were tested in cardiac organoids from human pluripotent stem cells. Following NRP, 3-OHB increased cardiac output (P < 0.0001) by increasing stroke volume (P = 0.006), dP/dt (P = 0.02) and reducing arterial elastance (P = 0.02). Following transplantation, infusion of 3-OHB maintained mitochondrial respiration (P = 0.009) but caused inotropy-resistant vasoplegia that prevented weaning. In cardiac organoids, 3-OHB increased contraction amplitude (P = 0.002) and shortened contraction duration (P = 0.013) without affecting calcium handling or conduction velocity. 3-OHB had beneficial cardiac effects and may have a potential to secure cardiac function during heart transplantation. Further studies are needed to optimize administration practice in donors and recipients and to validate the effect on mitochondrial function.

Organs obtained from brain dead donors can have suboptimal outcomes. Activation of the innate immune system and translocation of intestinal bacteria could be causative. Thirty two pigs were assigned to control, brain death (BD), BD + luminal intestinal polyethylene glycol (PEG), and BD + luminal intestinal University of Wisconsin solution (UW) groups. Animals were observed for 360 min after BD before organ retrieval. 2,000 mL luminal intestinal preservation solution was instilled into the duodenum at the start of organ procurement. Repeated measurements of plasma C3a, Terminal Complement Complex (TCC), IL-8, TNF, and lipopolysaccharide binding protein were analysed by immunoassays. C3a was significantly higher in the BD groups compared to controls at 480 min after brain death. TCC was significantly higher in BD and BD + UW, but not BD + PEG, compared to controls at 480 min. TNF was significantly higher in the BD group compared to all other groups at 480 min. LPS binding protein increased following BD in all groups except BD + PEG, which at 480 min was significantly lower compared with all other groups. Brain death induced innate immune system activation was decreased by luminal preservation using PEG during organ procurement, possibly due to reduced bacterial translocation.

Background: Organs obtained from brain dead (BD) donors often have worse outcomes. Activation of the complement system and translocation of intestinal bacteria could be causative. We aimed to examine activation of the complement system following BD and evaluate the systemic and local effect of adding luminal intestinal preservation to classical vascular preservation. Methods and material: BD was induced in 30 pigs (four groups: control (n=7), BD alone (n=8), BD + luminal intestinal polyethylene glycol (PEG, n=7) and BD + luminal intestinal University of Wisconsin solution (UW, n=8) using a previously validated method and all animals were observed for 6 hours before organ retrieval. In the PEG and UW groups, 2000 ml of the selected solution was instilled into the duodenum during the organ procurement surgery. Repeated measurements of C3a, Terminal Complement Complex (TCC), IL-8 and TNF were performed in plasma at baseline, BD, 30, 60, 120, 240 and 360 minutes after BD, and following the intestinal intervention (480). Plasma lipopolysaccharide binding protein (LPS-BP) was measured at baseline, BD, and 480 minutes after BD. All were normalised to albumin concentration. Biopsies were taken from jejunum and ileum at time of removal and following 8, 14 and 24 hours of static cold storage (SCS) using UW. Preliminary analysis has been performed at 24 hours of SCS for the BD groups, full histology will be available soon. Results: All animals were kept circulatory- and respiratory stable until organ procurement. At 480 minutes, C3a was significantly higher in BD, BD+PEG, and BD+UW groups compared to control group (all p<0.05) (fig. 1A). TCC was significantly higher in the combined BD group compared to control at 360 minutes, at 480 minutes, the BD and BD+UW groups were significantly higher compared to the control group (all p<0.05) (fig. 1B). IL-8 and TNF were significantly higher in the BD group compared to all other groups at 480 minutes (p=0,003 and p=0.001) (fig. 1C and D). LPS-BP increased following induction of BD in all groups except BD+PEG, which at 480 minutes were significantly lower (p=0.002) (fig. 1E and F) compared with all other groups. Preliminary biopsies from the Jejunum after 24 hours of SCS show a reduced median Chiu/Park score in the BD+PEG (2.5) and BD+UW (2.0) groups compared to the BD group (fig. 2). Conclusion: The complement system is activated following BD independently of intestinal and luminal preservation and may lead to inflammation. Luminal intestinal preservation during organ procurement led to lower Chiu/Park scores, and reduced cytokine and LPS-BP expression, which may be due to reduced bacterial translocation occurring during surgery independent of BD. Luminal PEG intervention may be combined with early innate immune system inhibition in BD donors to prevent systemic inflammation, which hampers organ function.

Abstract Background Lactate is traditionally acknowledged as a by-product of anaerobic glucose metabolism. Recently, however, lactate has been proven to be a preferred oxidative substrate for stressed myocardium. Studies have shown that exogenous lactate infusion provides beneficial hemodynamic effects including increased cardiac output (CO). Nevertheless, the exact mechanism of action underlying the hemodynamic effects of lactate infusion has not been fully elucidated. Aim To identify the cardiovascular mechanisms behind the acute hemodynamic effects of exogenous sodium lactate infusion in an experimental model of healthy human-sized pigs. Methods We performed a randomized, assessor-blinded crossover study in eight female 60 kg pigs. In randomized order, the pigs received an infusion with 1 M sodium lactate for two hours and a control infusion with iso-osmolar and isovolumetric sodium chloride for two hours. The two infusion periods were separated by a one-hour washout period. We measured CO and pulmonary pressures hourly with a pulmonary artery catheter. A pressure-volume admittance catheter was inserted in the left ventricle to assess measures of cardiac efficiency, contractility, afterload, and preload. Hemodynamic measures as arterial blood pressure, heart rate, and mixed venous saturation (SvO2) were measured hourly as well. The study followed the principles of laboratory animal care (NIH Publication no. 85-23 revised 1985) and national and European legislations. Results Lactate levels increased by 9.9 mmol/L (95% CI 9.1 to 11.0) and CO increased by 2.0 L/min (95% CI 1.2 to 2.8) during lactate infusion as compared with the control period (figure 1). During lactate infusion, ejection fraction increased by 16.0 percentage points (95% CI 1.9 to 31.0) and heart rate by 21 bpm (95% CI 9 to 32) compared with control. Arterial elastance decreased by -1.1 mmHg/ml (95% CI -2.1 to -0.18). Lactate infusion also increased cardiac efficiency, SvO2, arterial pH, and arterial glucose concentration significantly. The infusion of lactate led to no changes in systemic arterial pressure nor pulmonary pressures including pulmonary artery wedge pressure. Also, no changes were found in left ventricle end systolic elastance (contractility). Futhermore, no change in left ventricle end-diastolic volume or -pressure (preload) were observed during lactate infusion compared with the control (figure 2). Conclusion High dose lactate infusion increased cardiac output by reducing afterload. No changes in left ventricular contractility or -preload were observed.Fig 1:Lactate concentration and COFig 2:Changes of endpoint parameters

Abstract Animal models of cardiovascular disease are often evaluated by invasive instrumentation for phenotyping. As no consensus exists, both open‐ and closed‐chest approaches are used, which might compromise rigour and reproducibility in preclinical research. We aimed to quantify the cardiopulmonary changes induced by sternotomy and pericardiotomy in a large animal model. Seven pigs were anaesthetized, mechanically ventilated and evaluated by right heart catheterization and bi‐ventricular pressure–volume loop recordings at baseline and after sternotomy and pericardiotomy. Data were compared by ANOVA or the Friedmann test where appropriate, with post‐hoc analyses to control for multiple comparisons. Sternotomy and pericardiotomy caused reductions in mean systemic (−12 ± 11 mmHg, P = 0.027) and pulmonary pressures (−4 ± 3 mmHg, P = 0.006) and airway pressures. Cardiac output decreased non‐significantly (−1329 ± 1762 ml/min, P = 0.052). Left ventricular afterload decreased, with an increase in ejection fraction (+9 ± 7%, P = 0.027) and coupling. No changes were observed in right ventricular systolic function or arterial blood gases. In conclusion, open‐ versus closed‐chest approaches to invasive cardiovascular phenotyping cause a systematic difference in key haemodynamic variables. Researchers should adopt the most appropriate approach to ensure rigour and reproducibility in preclinical cardiovascular research.

Purpose To investigate primary graft function of hearts from circulatory dead donors (DCD) preserved with oxygenated hypothermic machine perfusion (oHMP) (XVIVO Heart preservation system) following either direct procurement and perfusion (DPP) or normothermic regional perfusion (NRP) with subsequent transplantation and correlate graft function to oHMP perfusion parameters. Methods In a porcine model, DCD was instituted with circulatory arrest of 15 min, followed by preservation with either DPP and oHMP or NRP and oHMP. After 180 min preservation, orthotopic heart transplantation (HTX) was performed. Dobutamine and norepinephrine were titrated for inotropic and vasoconstrictive support. After weaning from cardiopulmonary bypass, ventricular function was assessed by pressure-volume admittance and Swan-Ganz catheters. Left ventricular contractility was correlated to available HMP parameters using spearman rank correlation. Results Functional warm ischemic time (FWIT) was similar between groups (DPP 19±1 and NRP 18±1 min, p = 0.23), while time from withdrawal to oxygenated reperfusion was significantly longer in the DPP group (DPP 39±6 and NRP 21±1 min, p < 0.001). End-oHMP coronary flow was negatively correlated to contractile function, while oxygen uptake was positive correlated contractile function. Delta values of perfusion parameters did not correlate to contractile function. Conclusion Coronary flow and oxygen extraction during oHMP may be important predictors of early graft contractile function post-HTX from DCD donors.

BACKGROUND: Heart transplantation in donation after circulatory death (DCD) relies on warm perfu-sion using either in situ normothermic regional perfusion (NRP) or ex situ normothermic machine perfusion. In this study, we explore an alternative: oxygenated hypothermic machine perfusion (HMP) using a novel clinically applicable perfusion system, which is compared to NRP with static cold storage (SCS). METHODS: In a porcine model, a DCD setting was simulated, followed by either (1) NRP and SCS (2) NRP and HMP with the XVIVO Heart preservation system or (3) direct procurement (DPP) and HMP. After preservation, heart transplantation (HTX) was performed. After weaning from cardiopulmonary bypass (CPB), biventricular function was assessed by admittance and Swan-Ganz catheters. RESULTS: Only transplanted hearts in the HMP groups showed significantly increased biventricular contractility (end-systole elastance) 2 hour post-CPB (left ventricle absolute change: NRP HMP: +1.8 +/- 0.56, p = 0.047, DPP HMP: +1.5 +/- 0.43, p = 0.045 and NRP SCS: +0.97 +/- 0.47 mmHg/ml, p = 0.21; right ventricle absolute change: NRP HMP: +0.50 +/- 0.12, p = 0.025, DPP HMP: +0.82 +/- 0.23, p = 0.039 and NRP SCS: +0.28 +/- 0.26, p = 0.52) while receiving significantly less dobutamine to maintain a cardiac output >4l/min compared to SCS. Diastolic function was preserved in all groups. Post-HTX, both HMP groups showed significantly less increments in plasma troponin T compared to SCS. CONCLUSION: In DCD HTX, increased biventricular contractility post-HTX was only observed in hearts preserved with HMP. In addition, the need for inotropic support and signs of myocardial damage were lower in the HMP groups. DCD HTX can be successfully performed using DPP followed by preservation with HMP in a preclinical setting. J Heart Lung Transplant 2023;42:730-740 (c) 2023 The Author(s). Published by Elsevier Inc. on behalf of International Society for Heart and Lung Transplantation. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

BACKGROUND:Thoracoabdominal normothermic regional perfusion (NRP) is a new method for in situ reperfusion and reanimation of potential donor organs in donation after circulatory death by reperfusion of the thoracic and abdominal organs with oxygenated blood. We investigated effects of high oxygenation (HOX) versus low oxygenation (LOX) during NRP on donor heart function in a porcine model. METHODS:Pigs (80 kg) underwent a 15-min anoxic cardiac arrest followed by cardiac reanimation on NRP using a heart-lung bypass machine with subsequent assessment 180 min post-NRP. The animals were randomized to HOX (FiO2 1.0) or LOX (FiO2 0.21 increased to 0.40 during NRP). Hemodynamic data were obtained by invasive blood pressure and biventricular pressure-volume measurements. Blood gases, biomarkers of inflammation, and oxidative stress were measured. RESULTS:Eight of 9 animals in the HOX group and 7 of 10 in the LOX group were successfully weaned from NRP. Right ventricular end-systole elastance was significantly improved in the HOX group compared with the LOX group, whereas left ventricular end-systole elastance was preserved at baseline levels. Post-NRP cardiac output, mean arterial, central venous, and pulmonary capillary wedge pressure were all comparable to baseline. Creatinine kinase-MB increased more in the LOX group than the HOX group, whereas proinflammatory cytokines increased more in the HOX group than the LOX group. No difference was found in oxidative stress between groups. CONCLUSIONS:All hearts weaned from NRP showed acceptable hemodynamic function for transplantation. Hearts exposed to LOX showed more myocardial damage and showed poorer contractile performance than hearts reperfused with high oxygen.

BACKGROUND:Ex vivo lung perfusion (EVLP), is a platform that allows simultaneous testing and treatment of the lungs. However, use of EVLP is costly and requires access to lab animals and accompanying facilities. To increase the use of EVLP for research, we developed a method to perform EVLP using abattoir procured lungs. Furthermore, we were also able to significantly decrease costs.METHODS:Six pair of lungs were procured from abattoir sheep. The lungs were then flushed and stored in ice for 3 h. A low-flow (20% of cardiac output) approach, a tidal volume of 6 ml/kg bodyweight and total perfusion time of 3 h were chosen. Perfusion fluids and circuits were self-made. Lung biopsies, perfusate collection, respiratory values, circulatory pressures were recorded and hourly blood gas analyses were performed.RESULTS:Mean pO2 remained stable from 60 min (49.3 ± 7.1 kPa) to 180 min (51.5 kPa ± 8.0), p = 0.66. Pulmonary artery pressure remained ≤15 mm Hg and the left atrial pressure remained between 3 and 5 mm Hg and peak respiratory pressures ≤20 cmH2 O. Lactate dehydrogenase increased from start (96.3 ± 56.4 U/L) to the end of perfusion (315.8 ± 85.0 U/L), p < 0.05. No difference was observed in ATP between procurement and post-EVLP, 129.7 ± 37.4 μmol/g protein to 132.0 ± 23.4 μmol/g, p = 0.92.CONCLUSIONS:Sheep lungs, acquired from an abattoir, can be ex vivo perfused under similar conditions as lab animal lungs with similar results regarding e.g., oxygenation and ATP restoration. Furthermore, costs can be significantly reduced by making use of this abattoir model. By increasing accessibility and lowering costs for experiments using lung perfusion, more results may be achieved in the field of lung diseases.

Purpose We sought to compare two strategies for cardiac reanimation in normothermic regional perfusion (NRP) in a clinically relevant porcine model of donation after circulatory death (DCD). To this day, many different protocols for NRP have been described. Methods For NRP-strategy 1(30mProp), pigs (n=16) were anaesthetized with intravenous Propofol (3.5 mg/kg/h) and subjected to hypoxic circulatory arrest (CA) by halting mechanical ventilation. After an 8-minute warm ischemia period, donor hearts were reanimated by a 30-minute NRP-period with Propofol suspended. For NRP-strategy 2(60mSevo), pigs (n=10) were anaesthetized with inhaled Sevoflurane (3.5%) before institution of hypoxia induced CA. A 10-minute warm ischemia followed before 60 minutes NRP with Sevoflurane continued. Both groups were reperfused via central cannulation with the aortic arch vessels and infrarenal aorta occluded. NRP flow, oxygenation, and weaning were standardized between groups. We assessed hemodynamic function with invasive blood pressure and bi-ventricular pressure-volume recordings 30 minutes post-NRP. Results All hearts were successfully reanimated during NRP in both groups. During NRP, a significantly higher mean arterial blood pressure and a minor need for pressor support with norepinephrine were observed in the 60mSevo group compared to the 30mProp group. Cardiac output remained on baseline levels in both groups post-NRP. Arterial lactate was significantly lower in the 60mSevo group post-NRP compared to the 30-minProp group. Left ventricular end-systole elastance as a measure of contractility increased significantly from baseline to post-NRP by 0.5 mmHg/mL (95%CI 0.09 : 1.0) in the 60-minSevo group and increased non-significantly by 0.3 mmHg/mL (95%CI -0.04 : 0.7) in the 30minProp group, while right ventricular contractility increased non-significantly in both groups. Conclusion Hearts reperfused for 60 minutes combined with inhaled Sevoflurane showed superior contractile function compared to hearts subjected to 30-minute NRP and Propofol anaesthesia. The results indicate that longer NRP is beneficial in DCD heart donation.

BACKGROUND:The hemodynamic effects of aortic arch vessel (AAV) clamping during normothermic regional perfusion (NRP) in donation after circulatory death is unknown. We investigated effects of AAV clamping during NRP compared with no clamping in a porcine model. METHODS:In 16 pigs, hemodynamic parameters were recorded including biventricular pressure-volume measurements and invasive blood pressure. Additionally, blood gas parameters and inflammatory cytokines were used to assess the effect of AAV clamping. The animals were centrally cannulated for NRP, and baseline measurements were obtained before hypoxic circulatory arrest was induced by halting mechanical ventilation. During an 8-min asystole period, the animals were randomized to clamp (n = 8) or no-clamp (n = 8) of the AAV before commencement of NRP. During NRP, circulation was supported with norepinephrine (NE) and dobutamine. After 30 min of NRP, animals were weaned and observed for 180 min post-NRP. RESULTS:All hearts were successfully reanimated and weaned from NRP. The nonclamp groups received significantly more NE to maintain a mean arterial pressure >60 mm Hg during and after NRP compared with the clamp group. There were no between group differences in blood pressure or cardiac output. Pressure-volume measurements demonstrated preserved cardiac function' including ejection fraction and diastolic and systolic function. No between group differences in inflammatory markers were observed. CONCLUSIONS:AAV clamping did not negatively affect donor cardiac function or inflammation after circulatory death and NRP. Significantly less NE was used to support in the clamp group than in the nonclamp group.

Absolute differences in cardiopulmonary variables at baseline with closed cest and closed pericardium to conditions after sternotomy with open chest but closed pericardium and after pericardiotomy with open chest and open pericardium. Data are presented as mean±SD or median [interquartile range] where appropriate. Groups are compared with one-way ANOVA or Friedman test with Turkey’s or Dunn’s multiple comparison post-hoc test where appropriate. Statistical analyses were performed on the absolute values and not on the differences. n=7 for all unless stated otherwise.Abbreviations: MAP, mean arterial pressure; RV, right ventricular; CO, cardiac output; SV, stroke volume; mPAP, mean pulmonary arterial pressure; CVP, central venous pressure; PCWP, pulmonary capillary wedge pressure; PVR, pulmonary vascular resistance; SVR, systemic vascular resistance; PaCO2, partial pressure of arterial CO2; PaO2, partial pressure of arterial O2; FiO2, fraction of inhaled O2; PvCO2, partial pressure of mixed venous CO2; PvO2, partial pressure of mixed venous O2; EtCO2, end-tidal CO2; Ppeak, peak airway pressure; Pmean, mean airway pressure; LV, left ventricular; ESP, end-systolic pressure; EDP, end-diastolic pressure; ESV, end-systolic volume; EDV, end-diastolic volume; EF, ejection fraction; Ea, arterial elastance; SW, stroke work; dP/dt, derivative of pressure over time; Ees, end-systolic elastance; Eed, end-diastolic elastance; PRSW, preload recruitable stroke work; PVA, pressure-volume area.

Background. The cerebral effect of clamping following normothermic regional perfusion (NRP) in donation after circulatory death (DCD) remains unknown. We investigated the effect of cerebral reperfusion during NRP and the preventive effect of clamping on brain function in a porcine model. Methods. In 16 pigs, intracranial physiological parameters were recorded, including pressure, cerebral blood perfusion (CBF), temperature, and oxygen. Additionally, electroencephalography (EEG) and somatosensory evoked potentials (SSEPs) were used to assess brain function. The animals were cannulated for the heart-lung machine, and baseline measurements were performed before withdrawal from life support. After 8 min of mechanical asystole, the animals were randomly allocated to clamp (n = 8) or nonclamp (n = 8) of the aortic arch vessels. After 30 min of NRP, the animals were monitored for 3 h after weaning (AW). Results. Intracranial measurements of CBF, oxygen, and temperature indicated successful occlusion of the arch vessels following NRP and AW in the clamp group versus the nonclamp group. In the clamp group, EEG was isoelectric and SSEPs were absent AW in all pigs. In the nonclamp group, EEG activity was observed in all 8 pigs, whereas SSEPs were observed in 6 of 8 pigs. Additionally, agonal respiratory movements in the form of gasping were observed in 6 of 8 pigs in the nonclamp group. Conclusions. Reperfusion of the brain during NRP led to a return of brain activity. Conversely, clamping of the arch vessels halted cerebral circulation, ensuring the permanent cessation of brain function and maintaining the determination of death in DCD.

Introduction: Cardiac transplantation following circulatory death (DCD) and normothermic regional perfusion (NRP) is a new strategy that allows assessment of cardiac function and therapeutical interventions before cardiac transplantation. Sodium-3-hydroxybutyric acid (3-OHB) increases cardiac output by 40% in heart failure patients and diminishes ischemia and reperfusion (IR) injury, presumably by improving mitochondrial energy metabolism. Hypothesis: We hypothesize that infusion with 3-OHB during NRP improves cardiac hemodynamic function after NRP and mitochondrial function after cardiac transplantation. Methods: Pigs ~80 kg underwent a 15-minute anoxic cardiac arrest followed by NRP on a heart-lung cardiac bypass machine. During NRP pigs received 3-OHB or Ringer Acetate infusion. We measured hemodynamic function invasively using pressure-volume catheters and mitochondrial function by high resolution respirometry. Results: Infusion with 3-OHB (360mg/kg/h) increased plasma levels of 3-OHB from 0.05±0.06mM to 3.95±1.13mM (P=0.006) following NRP. 3-OHB increased cardiac output by 5.18±0.97 L min -1 (P<0.0001) driven by a 60% reduction in afterload (3-OHB vs. control: 1.4±0.2 vs. 2.2±0.7 mmHg*mL -1 , P=0.02) and an increase in stroke volume of 36±11mL (P=0.006). Following transplantation and 3-OHB infusion, maximally coupled mitochondrial respiration returned to baseline levels corresponding to a 50% improvement compared with control (3-OHB vs. control: 135±25 vs. 78±26 ρmol O 2 *s -1 mg -1 , P=0.0008). The increment was associated with uncoupling of the inner mitochondrial membrane (3-OHB vs. control: 122±19 vs. 70±34 ρmol O 2 *s -1 mg -1 , P=0.018). Transplantation caused a shift in mitochondrial substrate efficiency measured as the respiratory control ratio, favoring 3-OHB over glucose linked substrates (3-OHB vs. glucose: 22±12 vs. 8±4, p=0.0008). Conclusions: Infusion with 3-OHB improved cardiac hemodynamic recovery following NRP. The improvement was driven predominantly by afterload reduction and was associated with an improvement in mitochondrial respiratory capacity.