Perfusion Temperature Research Articles

Machine perfusion in organ transplantation

Machine perfusion has emerged as a tool to evaluate pretransplant graft function more objectively during preservation. Machine perfusion also offers the possibility to recondition questionable organs and to 'immunomodulate' allografts ex vivo. This article aims to review the current knowledge on machine perfusion of the various solid thoracic and abdominal organs, and to discuss the new possibility of conditioning and treating grafts with mesenchymal stem cells (MSCs) during machine perfusion. Different methods of machine perfusion have been described varying among organs in temperature and composition of perfusate. Commercial devices have recently become available for machine perfusion of all organs, with the largest clinical experience acquired in kidney and lung transplantation. Clinical studies are ongoing for liver, heart, and pancreas. MSC therapy in organ transplantation is now emerging with clinical studies set up to investigate its potential to attenuate ischemia/reperfusion injury (innate immunity) and to downregulate the alloimmune response (adaptive immunity) and promote engraftment after transplantation. We hypothesize that delivery of MSCs directly into the machine perfusion circuit may provide a unique opportunity to treat and immunomodulate organs prior to transplantation. To our knowledge, no study on ex-vivo delivery of MSCs during machine perfusion has been reported. Machine perfusion of solid organs has regained much attention during the last decade. It provides a new promising tool that may allow pretransplant ex-vivo assessment, preservation, repair, and conditioning of grafts. Experimental research and clinical trials testing the administration of MSCs during machine perfusion are warranted to explore the potential benefit and mechanisms of this approach.

Preparation of Kupffer cell enriched non‐parenchymal liver cells with high yield and reduced damage of surface markers by a modified method for flow cytometry

The aim of this study was to optimise a collagenase perfusion protocol for the isolation of a liver non-parenchymal cell (NPC) suspension enriched for Kupffer cells that reduced damage to F4/80 antigen cell surface expression to allow analysis by flow cytometry. Kupffer cell-enriched liver NPCs were isolated from C57BL/6 mice using different protocols. Flow cytometry was used to examine the effect of collagenase digestion on F4/80 expression on Kupffer cells, and results were represented by the percentage of F4/80 positive cells and by the F4/80 mean fluorescence intensity (MFI). The perfusion temperature, concentration of collagenase solution and total dosage of collagenase for liver perfusion influenced the effect of collagenase perfusion on the expression of F4/80 antigen on Kupffer cells. Collagenase perfusion at 28°C resulted in an increased percentage of F4/80 positive cells (P = 0.001) and MFI (P = 0.005) compared with 37°C. Perfusion with a total dose of 1.0 g/kg BW collagenase (using a 0.75 mg/mL solution) resulted in the highest percentage of F4/80 positive cells (P = 0.001) compared with 0.8 g/kg BW and 1.2 g/kg BW collagenase. Isolation of cells using the modified protocol resulted in a higher percentage of Kupffer cells (P < 0.001) and a higher MFI of F4/80 antigen (P < 0.001) compared with the common protocol.

Influence of perfusate temperature on nasal potential difference

Nasal potential difference (NPD) quantifies abnormal ion transport in cystic fibrosis. It has gained acceptance as an outcome measure for the investigation of new therapies. To quantify the effect of solution temperature on NPD, we first examined the effect of switching from room temperature (20-25°C) to warmed (32-37°C) solutions and vice versa during each perfusion step. Secondly, standard protocols were repeated at both temperatures in the same subjects. Changing solution temperature did not alter NPD during perfusion with Ringer's solution (<1 mV) (p>0.1). During perfusion with zero chloride solution, changing from room temperature to warmed solutions tended to decrease absolute NPD (i.e. it became less negative) by 0.9 mV (p>0.1); changing from warmed to room temperature increased NPD by 2.1 mV (p<0.05). During isoprenaline perfusion, changing from room temperature to warmed solutions increased NPD by 1.5 mV (p<0.01) and from warmed to room temperature decreased NPD by 1.4 mV (p<0.05). For full protocols at room temperature or warmed in the same subjects, mean values were similar (n = 24). During warmed perfusion, group results for total chloride response had a larger standard deviation. As this increased variability will probably decrease the power of trials, this study suggests that solutions at room temperature should be recommended for the measurement of NPD.

Effect of perfusion temperature on glucose and electrolyte transport during hyperthermic intraperitoneal chemoperfusion (HIPEC) with oxaliplatin

Hyperthermic intraperitoneal chemoperfusion (HIPEC) with oxaliplatin is increasingly used in patients with carcinomatosis from colorectal cancer. For reasons of chemical stability, oxaliplatin can only be administered in a dextrose (D5%) solution, and this causes peroperative glucose and electrolyte shifts. Here, we examined the influence of perfusion temperature on glucose and electrolyte transport, metabolic shifts, and surgical morbidity. Patients with carcinomatosis underwent cytoreduction and HIPEC using oxaliplatin (460 mg/m(2) in D5%, open abdomen) during 30 min at 39°-41 °C. Intraperitoneal (IP) temperature was measured at three locations using thermocouple probes. The area under the temperature versus time curve (AUCt) was calculated using the trapezoid rule. The influence of perfusion temperature on surgical outcome was assessed using linear regression models and the Mann Whitney U test where appropriate. From July 2005 until March 2011, 145 procedures were performed in 139 patients with a diagnosis of CRC (70%), pseudomyxoma peritonei (11%), ovarian cancer (10%), or miscellaneous peritoneal malignancies (9%). Postoperative mortality and major morbidity were 1.4% and 26%, respectively. Higher perfusion temperature was related to more pronounced changes in serum glucose (P = 0.058), sodium (P = 0.017), and lactate (P < 0.001). The median duration of nasogastric drainage was 5 days, and this was unrelated to perfusion temperature (P = 0.76). The GI fistula rate and reoperation rate were 12.4% and 16.5% respectively; neither was related to perfusion temperature. In patients undergoing HIPEC with oxaliplatin, perfusion temperature exacerbates peroperative metabolic shifts but does not affect surgical outcome.

Evaluation of changes in hepatic disposition of phenolsulfonphthalein, indocyanine green and fluorescein isothiocyanate-dextran at low temperatures using a rat liver perfusion system

The aim of this study was to determine the factor changing the hepatic disposition of a drug during hypothermia using a rat liver perfusion system. The livers of male Wistar rats were perfused at 37, 32 or 28°C in the single-pass mode. Venous outflow dilution patterns and biliary excretion rate patterns of phenolsulfonphthalein (PSP), indocyanine green (ICG) and fluorescein isothiocyanate (FITC)-dextran (FD-4, MW 4400) after the injection of a bolus into the perfused rat liver were analysed based on statistical moment theory. The first-pass extraction ratio (E(h) ) of PSP was significantly decreased at 32 and 28°C compared with 37°C. The biliary recovery of PSP and its conjugate was decreased and the biliary excretion was kept at a high concentration and was prolonged by low perfusion temperatures. ICG was almost extracted by a single-pass through the liver even at 32 and 28°C. The biliary recovery of ICG was significantly decreased at low temperature. Although the distribution volume of FD-4 as a vascular reference was not changed by perfusion temperature, the E(h) of FD-4 was decreased at 28°C although not markedly. The change in hepatic disposition of a drug at low perfusion temperatures differed according to disposition processes under hypothermia.

Effects of Perfusion Temperature on Inflammatory Response and Outcome Following Cardiopulmonary Bypass

Effects of Perfusion Temperature on Inflammatory Response and Outcome Following Cardiopulmonary Bypass

Myocardial protection strategy for conventional aortic valve replacement following previous coronary surgery: should it be patient-specific?

We read with great interest the recent article by Park et al. [1] regarding outcomes in patients who underwent isolated aortic valve replacement (AVR) in a redo setting with a patent internal thoracic artery (ITA). They further analysed the impact of ITA control on patient outcome, concluding that not impeding ITA blood flow and allowing thus myocardial perfusion was associated with improved outcomes. Myocardial territories at the borders of ITA distribution are traditionally considered prone to ischaemic changes due to an incomplete cardioplegic effect. Although ITA control aims at preventing cardioplegia ‘washout’ to achieve adequate cardioplegic arrest, this was early associated with a substantial risk of graft injury and associated mortality. A number of approaches have been developed to address myocardial protection in this anatomically complex group, including various on-pump beating heart approaches. These incorporate pure retrograde perfusion of normothermic oxygenated blood [2, 3] as well as simultaneous retrograde and antegrade blood perfusion, according to individual patient anatomy [4]. Furthermore, if previous revascularization provides sufficient perfusion of all myocardial territories, retrograde and/ or antegrade blood perfusion may be avoided entirely with safety [2, 5]. We have described a case of AVR in the presence of bilateral patent ITAs with the use of cross-clamp fibrillation [6]. Perfusion temperature ranged from 32°C to normothermia in these series. The authors used cold blood cardioplegia in all patients [1]. Retrograde and/or antegrade perfusion with oxygenated blood appears to provide myocardial protection and optimal conditions for performing conventional AVR in selected patients. From the technical standpoint, potential washout from the coronary ostia is easily manageable with simple measures, as already described in the literature. Appreciating the limitations of a retrospective study in this complex entity, we would like to enquire if the authors have modified their approach in recent years in regard to achieving myocardial protection. We commend the authors on their outstanding results.

Attempt to Rescue Discarded Human Liver Grafts by End Ischemic Hypothermic Oxygenated Machine Perfusion

In a porcine liver transplant model, a brief period of oxygenated hypothermic machine perfusion (HMP) at the end of simple cold storage (SCS) has been shown to improve the viability of damaged liver grafts. To test the clinical validity of this strategy, we randomized SCS-discarded human liver grafts to either 4 hours of HMP ( n = 13) or an additional 4 hours of SCS ( n = 14). All livers were then warm reperfused to mimic ischemia-reperfusion injury ex vivo. The settings for HMP were: portal vein: 3 mm Hg, 300 mL/min and hepatic artery: 20 mm Hg, p o 2: 300 mm Hg. Perfusion used Kidney Machine Perfusion Solution at 4°C to 8°C. During warm reperfusion, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) values were higher ( P < .015) among the SCS versus HMP methods at all times. The AST slope was lower in HMP versus SCS ( P = .01). The LDH slope tended to be lower for HMP versus SCS ( P = .07). Morphological scores were not different between HMP and SCS. At the start of warm reperfusion, MAPK was lower in HMP versus SCS ( P = .02). Endothelin-1 (EDN1) and ICAM-1 tended to be lower in HMP versus SCS ( P = .1 and .07, respectively). No difference was noted in MAPK, EDN1, and ICAM-1 after 60 or 120 minutes of warm reperfusion. In conclusion, HMP down-regulated MAPK and tended to reduce EDN1 and ICAM-1 mRNA in human liver grafts. During warm reperfusion, HMP versus SCS livers showed reduced AST and LDH release but no morphological difference. Further optimization of liver HMP may require different timing/duration of perfusion and/or an higher perfusion temperature.

Timing of Heparin and Perfusion Temperature During Procurement of Organs with Extracorporeal Support in Donors After Circulatory Determination of Death

Despite successful resuscitation of donors after circulatory determination of death (DCD) with extracorporeal support (ECS), the technique is limited by ethical concerns about donor management (heparinization) and the complexity to operate the ECS circuit. This work studies different timing of heparin administration and the effects of ECS-perfusion temperature. Cardiac arrest (CA) was induced in swine. Heparin studies, three groups: 1) PRE5, heparin 5 minutes before CA; 2) POST5, heparin 5 minutes after CA, plus 2 minutes external chest compressions; and 3) POST30, heparin with the initiation of ECS after 30 minutes CA. Perfusion temperature study, two groups: 1) normothermic, ECS-38.5°C after 30 minutes CA and 2) room temperature, ECS-25.5°C for the first 90 minutes, followed by ECS-38.5°C. Heparin studies: ECS target flows (>50 ml/kg/min) were not achieved in the POST30 group, affecting local organ perfusion as observed with poor bile (<4 ml/min) and urine output (<25 ml/min), when compared with the other groups (normal values). Temperature study: In both groups, ECS target flows were reached, and urine/bile output was restored. Heparinization 5 minutes after CA is equivalent to premortem heparinization in this ECS-DCD model. Heparinization after CA could reduce ethical concerns. Donors after circulatory determination of death were successfully resuscitated at both temperatures, suggesting that the heat exchanger/water heater can be removed to simplify the ECS circuit.

Chaos particle swarm optimization and T–S fuzzy modeling approaches to constrained predictive control

Predictive control of systems is very much related to the efficiency and cost of systems, as well as to the quality of systems outcomes. However, it is difficult to achieve optimal predictive control because most predictive controls for systems have characteristics of randomness, strong and complex constraints, large delay time, fuzziness, and nonlinearity. Conventional methods of solving constrained nonlinear optimization problems for predictive control are mainly based on quadratic programming, which is quite sensitive to initial values, easy to trap in local minimal points, and requires large computational effort. In recent years, T–S fuzzy modeling has been found to be an effective approach in performing predictive control. Intelligent optimization algorithms, such as chaos optimization algorithm (COA) and particle swarm optimization (PSO), have been shown to have faster convergence and higher iterative accuracy than those based on conventional optimization methods. In this paper, chaos particle swarm optimization (CPSO), which involves combining the strengths of COA and PSO, and T–S fuzzy modeling are proposed as approaches to perform constrained predictive control. Predictive control of temperature of continued hyperthermic celiac perfusion for medical treatment based on the proposed approaches was carried out. Simulation tests were conducted to evaluate the performance of temperature control based on T–S fuzzy modeling and CPSO. Test results indicate that the T–S fuzzy model based on CPSO outperforms models based on generalized predictive control, COA, and PSO.

Rationale for Heating Oxaliplatin for the Intraperitoneal Treatment of Peritoneal Carcinomatosis

To study the effect of heat on the absorption of intraperitoneal (IP) oxaliplatin using a murine model. Because of its efficiency in the systemic treatment of colorectal cancer, oxaliplatin is currently used in hyperthermic intraperitoneal chemotherapy (HIPEC) for peritoneal carcinomatosis. However, its properties when administered by the IP route have not been well characterized by preclinical studies. Under general anesthesia, 35 Sprague-Dawley rats were submitted to 3 different doses of IP oxaliplatin (460, 920, and 1840 mg/m(2)) at 3 different perfusion temperatures (37, 40, and 43°C) during 25 minutes. At the end of perfusion, samples in different compartments (peritoneum, portal blood, and systemic blood) were harvested and the concentrations of oxaliplatin were measured by high performance liquid chromatography. As the dose of IP oxaliplatin was increased, higher concentrations were observed in every compartment. When the temperature of IP oxaliplatin was increased, it resulted in an increase of its peritoneal concentration (linear regression 0.38; 95% CI: 0.28-0.47) and in a decrease of its systemic blood (linear regression -1, 02; 95% CI: -1.45 to -0.60) and portal blood (linear regression -1.08; 95% CI: -1.70 to -0.47) concentrations. Proportionally to the dose administered, IP oxaliplatin leads to high concentration of drug in peritoneal tissues. Furthermore, heat enhances peritoneal tissue concentration of Oxaliplatin while reducing its systemic absorption. This last effect may possibly lead to decreased systemic toxicity. These observations support the use of oxaliplatin for HIPEC.

The effect of temperature on the alpha-adrenoceptor antagonist potency of indoramin and labetalol in the rat perfused mesenteric vascular bed.

The effect of reduction in temperature of perfusion from 37 to 27 degrees C and 20 degrees C on the ability of the adrenoceptor antagonists indoramin and labetalol to block pressor responses to noradrenaline in the perfused mesenteric vascular bed of the rat was examined. The results suggest that in rat mesenteric bed, antagonist potency of both agents is increased at low temperatures.

Tepid hypothermic (32 C) circulatory arrest for total aortic arch replacement: a paradigm shift from profound hypothermic surgery

In total aortic arch replacement (TARCH) using hypothermic circulatory arrest (HCA) and selective cerebral perfusion (SCP), postoperative cerebral complications, including metabolic abnormalities, are by no means rare. Furthermore, there is a lack of international guidelines for the optimal perfusion temperature and flow for SCP. Starting in 2008, TARCH was performed using tepid HCA at 32 °C. In the present study, 27 patients (group C) who underwent TARCH with deep hypothermia at the lowest rectal temperatures of 20-25 °C were retrospectively reviewed and compared with 23 patients (group W) who underwent TARCH with 32 °C tepid hypothermia. Preoperative patient characteristics and intraoperative and postoperative parameters were compared. Preoperative patient characteristics did not differ significantly between the two groups. Circulatory arrest time, cardiopulmonary bypass time, operating time, amount of blood transfused and postoperative neurological complications were significantly reduced in group W compared with group C. Our procedure of TARCH using tepid hypothermia at 32 °C was safe, and it significantly reduced all parameters of extracorporeal circulation time. However, this study has several limitations. To indicate the safety and usefulness of tepid HCA for TARCH, a further multifaceted study should be performed with a greater number of patients.

What is the optimal myocardial preservation strategy at re-operation for aortic valve replacement in the presence of a patent internal thoracic artery?

The optimal myocardial preservation strategy at re-operation for aortic valve replacement (AVR) after prior coronary artery bypass grafting (CABG) in the presence of a patent internal thoracic artery (ITA) remains undefined. Patients undergoing AVR after prior CABG at our institution between 1 January 1996 and 31 December 2007 were identified; operative notes and outcomes were reviewed. Of 628 patients with prior CABG undergoing AVR with or without concomitant procedures, 427 patients had a patent ITA. In 390, management of the ITA was detailed in the operative note, including 251 in whom it was clamped and 139 in whom it was left uncontrolled. Groups were demographically similar, although re-operative CABG was more frequent in the clamped group (42% vs 23%, p<0.001). The operative mortality rate among those undergoing only AVR ± CABG was 7.7% (19/246), while that for all cases was 10.8% (42/390), and was lower when the ITA was left uncontrolled both for AVR ± CABG (4.1% vs 10.1%, p=0.08) and overall (7.2% vs 12.7%, p=0.09). By multivariate analysis, leaving the ITA uncontrolled appeared protective (odds ratio (OR) 0.46, p=0.08). There was no clear trend supporting an optimal perfusion temperature when the ITA was left uncontrolled. Efforts to control the patent ITA at re-operation for AVR after prior CABG increase risk of injury and may actually increase operative mortality rate compared with leaving this critical graft open and perfusing the heart.

Osmotic and thermal control of magnocellular neurosecretory neurons – role of an N‐terminal variant of trpv1

The release of vasopressin (antidiuretic hormone) plays a key role in the osmoregulatory response of mammals to changes in salt or water intake and in the rate of water loss through evaporation during thermoregulatory cooling. Previous work has shown that the hypothalamus encloses the sensory elements that modulate vasopressin release during systemic changes in fluid osmolality or body temperature. These responses depend in part on a synaptic regulation of vasopressin neurons by afferent inputs arising from osmosensory and thermosensory neurons in the preoptic area. However, recent studies in rats and mice have shown that vasopressin neurons in the supraoptic nucleus also display intrinsic osmosensory and thermosensory properties. Isolated vasopressin neurons exposed to increases in perfusate temperature or osmolality generate increases in non-selective cation channel activity that cause membrane depolarization and increase neuronal excitability. These channels are calcium-permeable and can be blocked by ruthenium red. Moreover, intrinsic responses to osmotic and thermal stimuli are absent in magnocellular neurosecretory cells isolated from mice lacking the transient receptor potential vanilloid-1 (trpv1) gene, which encodes the capsaicin receptor. Immunostaining of vasopressin-releasing neurons with anti-TRPV1 antibodies reveals the presence of amino acids present in the carboxy terminus of the protein, but not those lying in the amino terminal domain. Thus, magnocellular neurosecretory neurons appear to express an N-terminal variant of trpv1 which lacks sensitivity to capsaicin, but which enables osmosensing and thermosensing.

Blood Temperature Management and Gaseous Microemboli Creation: An In-Vitro Analysis

Gaseous microemboli have been associated with post operative neurological deficits in patients undergoing cardiopulmonary bypass. Creating an optimal perfusion system that minimizes microemboli production and has enhanced abilities to sequester entrained air during the bypass procedure has been an important focus. This study examines the air-handling capabilities of a cardiopulmonary bypass circuit and correlates blood temperatures with microemboli loads proximal and distal to the arterial line filter within the circuit. Utilizing a Capiox RX25R oxygenator, Capiox 37 micron arterial filter, vacuum assisted venous return, and emboli detectors, 30 mL of air were injected into the venous line of a bypass circuit at eight different temperatures. Emboli were counted distal to the arterial line filter by the EDAQ® Quantifier (Emboli Detection and Classification). The average number of emboli detected distal to the arterial filter progressively increased as the perfusate temperature was dropped. At 37.0°C an average of 1.4 emboli was observed distal to the arterial filter within 90 seconds of the air injection. At 23.0°C an average of 49.8 emboli was detected. Air introduced into the venous side of the bypass circuit resulted in showers of microemboli being sent past the arterial line filter. In addition, as the bovine blood was cooled, the air handling capability of the circuit was diminished.

Stability of brain neocortical slice seizure-like activity during low-magnesium exposure: Measurement and effect of artificial cerebrospinal fluid temperature

Low-magnesium perfusion is an established method for inducing seizure-like activity in neocortical slices and is widely utilized as a model of human epilepsy. However, many contentious issues remain around optimizing in vitro cortical slice experimental protocols. In this study we investigated the stability of low-magnesium seizure-like event (SLE) activity at different perfusion temperatures; with an aim towards determining whether time-dependent effects in this preparation could be attributed to a reduction in tissue viability. The results showed that SLE characteristics changed significantly and consistently over a 3h recording period, independent of artificial cerebrospinal fluid temperature; there was a median increase in event frequency of 61% (p<0.001) following 2h of recording which remained elevated after 3h (52%, p<0.001). Event amplitude was significantly reduced after 3h (38% reduction, p<0.001). Similar effects were recorded whether perfusion temperature was maintained at 26°C or 36°C. No evidence was found to implicate a reduction in slice viability in these time-dependent changes in SLE behaviour. The results indicate that low-magnesium-induced SLE activity is not stable for long periods and the likelihood of time-related changes in slice performance must be considered when planning and interpreting experiments utilizing the low-magnesium seizure model.

The response of the human circulatory system to an acute 200-μT, 60-Hz magnetic field exposure

Recent research by the authors on the effects of extremely low-frequency (ELF) magnetic field (MF) exposure on human heart rate (HR), heart rate variability (HRV), and skin blood perfusion found no cardiovascular effects of exposure to an 1,800-μT, 60-Hz MF. Research from our group using rats, however, has suggested a microcirculatory response to a 200-μT, 60-Hz MF exposure. The present pilot study investigated the effects of 1h of exposure to a 200-μT, 60-Hz MF on the human circulation. Microcirculation (as skin blood perfusion) and HR were measured using laser Doppler flowmetry. Mean arterial pressure was monitored with a non-invasive blood pressure system. Ten volunteers were recruited to partake in a counterbalanced, single-blinded study consisting of two testing sessions (real and sham exposure) administered on separate days. Each session included four consecutive measurement periods separated by rest, allowing assessment of cumulative and residual MF effects. A within-subjects analysis of variance did not reveal session by time period interactions for any of the parameters which would have been suggestive of a MF effect (p>0.05). Perfusion, HR, and skin surface temperature decreased over the course of the experiment (p<0.05). The MF used in this experiment did not affect perfusion, HR, or mean arterial pressure. Decreasing perfusion and HR trends over time were similar to our previous results and appear to be associated with a combination of inactivity (resulting in decreasing body temperatures) and reduced physiological arousal.

Hypothermia improves ventricular myocyte contractility under conditions of normal perfusion and after an interval of ischemia

Aim Recent investigations have reported improved myocardial function during hypothermia following resuscitation from cardiac arrest. The effects of hypothermia on myocyte contractility were investigated under conditions of normal perfusion and after a 10 min interval of ischemia. Methods Ventricular myocytes were obtained from 10 male Sprague–Dawley rats weighing 400 ± 50 g. The myocytes were randomized to be perfused at: 37 °C, 34 °C, 32 °C, or 30 °C. A subsequent set of myocytes was subjected to 10 min of ischemia at 37 °C, prior to being randomized to reperfusion at: 37 °C, 34 °C, 32 °C or 30 °C. Myocyte contractility was expressed as length-shortening percentage. Intracellular Ca 2+ transients were assessed in a separate group of myocytes preloaded with Fura-2/AM. Sensitivity to Ca 2+ was tested by increasing perfusate Ca 2+ content, i.e. 0.5 mM, 1 mM and 2 mM. Results During normal perfusion and following reperfusion after 10 min of ischemia, myocyte contractility increased at 34 °C compared to 37 °C ( P < 0.01). When the perfusion temperature was decreased to 32 °C and 30 °C, contractility further increased ( P < 0.001). Intracellular Ca 2+ transients were greater during perfusion at 34 °C compared to those at 37 °C ( P < 0.001) and further increased at 30 °C ( P < 0.001). Increases in extracellular Ca 2+ concentration from 0.5 mM to 2 mM resulted in greater myocyte contractility during perfusion at 30 °C compared to that observed at 37 °C ( P < 0.001). Effects of hypothermia on intracellular Ca 2+ transients and sensitivity to Ca 2+ persisted after ischemia. Conclusions Hypothermia improved myocyte contractility, intracellular Ca 2+ transients and sensitivity to Ca 2+ under conditions of normal perfusion and following reperfusion after 10 min of ischemia.

The influence of storage temperature during machine perfusion on preservation quality of marginal donor livers

Although non-heart-beating donors have the potential to increase the number of available organs, the livers are used very seldom because of the risk of primary non-function. There is evidence that machine perfusion is able to improve the preservation of marginal organs, and therefore we evaluated in our study the influence of the perfusate temperature during oxygenated machine perfusion on the graft quality. Livers from male Wistar rats were harvested after 60-min warm ischemia induced by cardiac arrest. The portal vein was cannulated and the liver flushed with Lifor (Lifeblood Medical, Inc.) organ preservation solution for oxygenated machine perfusion (MP) at 4, 12 or 21 degrees C. Other livers were flushed with HTK and stored at 4 degrees C by conventional cold storage (4 degrees C-CS). Furthermore two groups with either warm ischemic damage only or without any ischemic damage serve as control groups. After 6h of either machine perfusion or cold storage all livers were normothermic reperfused with Krebs-Henseleit buffer, and functional as well as structural data were analyzed. Contrary to livers stored by static cold storage, machine perfused livers showed independently of the perfusate temperature a significantly decreased enzyme release of hepatic transaminases (ALT) during isolated reperfusion. Increasing the machine perfusion temperature to 21 degrees C resulted in a marked reduction of portal venous resistance and an increased bile production. Oxygenated machine perfusion improves viability of livers after prolonged warm ischemic damage. Elevated perfusion temperature of 21 degrees C reconstitutes the hepatic functional capacity better than perfusion at 4 or 12 degrees C.