Randomized controlled trial to evaluate flush and reperfusion techniques in liver transplantation

Post-reperfusion syndrome in liver transplant recipients: What is new in prevention and management?

Post-reperfusion syndrome (PRS) in liver transplant recipients remains one of the most dreaded complications in liver transplant surgery. PRS can impact the short-term and long-term patient and graft outcomes. The definition of PRS has evolved over the years, from changes in arterial blood pressures and heart and/or decreases in the systemic vascular resistance and cardiac output to including the fibrinolysis and grading the severity of PRS. However, all that did not reflect on the management of PRS or its impact on the outcomes. In recent years, new scientific techniques and new technology have been in the pipeline to better understand, manage and maybe prevent PRS. These new methods and techniques are still in the infancy, and they have to be proven not in prevention and management of PRS but their effects in the patient and graft outcomes. In this article, we will review the long history of PRS, its definition, etiology, management and most importantly the new advances in science and technology to prevent and properly manage PRS.

Hyperkalemia in liver transplantation

Hyperkalemia commonly occurs in patients undergoing liver transplantation. The intraoperative course of liver transplant often involves hemodynamic and metabolic derangements leading up to liver reperfusion. Potassium levels can rise to dangerous levels immediately after reperfusion. The consequences of intraoperative hyperkalemia include risk of malignant arrhythmias and cardiac arrest. This review explores the numerous causes of hyperkalemia, including contributing surgical and anesthetic factors. The authors also discuss various treatment options and surgical techniques to manage perioperative hyperkalemia. It is important for anesthesiologists to understand the implications and management of hyperkalemia to optimize patients and reduce the risk of an intraoperative cardiac arrest.

Mitigating hepatic ischemia and reperfusion injury with polyethylene glycol-enriched Ringer's lactate fluid: insights from an isolated perfused rat model

BACKGROUND

Cold ischemia-reperfusion (IR) injury is a multifactorial process detrimental to liver graft function during liver transplantation (LT). Although flushing hepatic grafts prior to reperfusion have been well explored, the optimal graft rinse solution to prevent cold IR injury remains largely undefined. The aim of this study was to evaluate whether a new rinse solution combining polyethylene glycol PM 35,000 Da (PEG35) with lactated solution (RLS) could mitigate cold IR injury in Wistar rats.

METHODS

Livers were isolated, preserved for 24 h and flushed immediately before ex vivo reperfusion with either RLS or PEG35-enriched RLS. Liver injury, graft function, energy balance, autophagy, oxidative stress as well as inflammatory response were assessed.

RESULTS

Flushing hepatic grafts with PEG35-enriched RLS resulted in decreased transaminase levels after cold ischemia. The improved graft function was evidenced by increased bile flow, enhanced BSP clearance, and reduced vascular resistance in these flushed grafts. Phospho-AMPK protein expression, as well as LC3B gene and protein expression were significantly increased compared to those unflushed and flushed only with RLS. PEG35-enriched RLS also maintained the oxidative state, as indicated by reduced activities of antioxidant enzymes and decreased MDA concentration. Additionally, this graft rinse solution down-regulated the inflammatory response by inhibiting the expression of genes involved in the HMGB-1/NF-κB/TNF-α signaling pathway.

CONCLUSION

These data strongly suggest that rinsing liver grafts with PEG35-enriched RLS prior to reperfusion represents a simple and cost-effective strategy to enhance liver functional recovery after cold IR injury. This approach could serve as a viable alternative to RLS in clinical applications, highlighting the need for further research to explore its broader implications.

Postreperfusion Syndrome in Patients Receiving Vasoactive Drugs During Liver Graft Reperfusion

OBJECTIVES

The most widely used definition of postreperfusion syndrome in liver transplant is a 30% decrease in mean arterial pressure during the first 5 minutes after vascular unclamping. With these criteria, increased postoperative morbidity has been reported. Vasoactivedrugs couldpreventthis syndrome.Themain objective of our study was to determine the incidence and complications associated with postreperfusion syndrome inpatientswho receivedvasoactive support.

MATERIALS AND METHODS

We studied 246 patients who received norepinephrine infusions to maintain mean arterial pressure ≥60 mm Hg and who were monitored with a Swan-Ganz catheter. Patients received a bolus of adrenaline after vascular unclamping in cases of insufficient response to norepinephrine.

RESULTS

Among the study patients, 57 (23.17%) developed postreperfusion syndrome. Patients who developed postreperfusion syndrome did not present with morepostoperative complications interms ofrenal dysfunction (P = .69), repeat surgery (P = .15), graft rejection (P = .69), transplant replacement surgery (P = .76), hospital stay (P = .70), or survival (P = .17) compared with patients without postreperfusion syndrome.

CONCLUSIONS

In patients who underwent orthotopic liver transplant, in whom vasoactive drugs were administered, a diagnosis of self-limited postreperfusion syndrome during the first 5 minutes after unclamping may not be associated with postoperative complications. The administration of vasoconstrictors may have a preventive effect on the postoperative complications associated with postreperfusion syndrome or they may mask the real incidence of postreperfusion syndrome. A broader definition of postreperfusion syndrome should be accepted.

Hypothermic Oxygenated Machine Perfusion (HOPE) Prior to Liver Transplantation Mitigates Post-Reperfusion Syndrome and Perioperative Electrolyte Shifts

(1) Background: Post-reperfusion syndrome (PRS) and electrolyte shifts (ES) represent considerable challenges during liver transplantation (LT) being associated with significant morbidity. We aimed to investigate the impact of hypothermic oxygenated machine perfusion (HOPE) on PRS and ES in LT. (2) Methods: In this retrospective study, we compared intraoperative parameters of 100 LTs, with 50 HOPE preconditioned liver grafts and 50 grafts stored in static cold storage (SCS). During reperfusion phase, prospectively registered serum parameters and vasopressor administration were analyzed. (3) Results: Twelve percent of patients developed PRS in the HOPE cohort vs. 42% in the SCS group (p = 0.0013). Total vasopressor demand in the first hour after reperfusion was lower after HOPE pretreatment, with reduced usage of norepinephrine (−26%; p = 0.122) and significant reduction of epinephrine consumption (−52%; p = 0.018). Serum potassium concentration dropped by a mean of 14.1% in transplantations after HOPE, compared to a slight decrease of 1% (p < 0.001) after SCS. The overall incidence of early allograft dysfunction (EAD) was reduced by 44% in the HOPE group (p = 0.04). (4) Conclusions: Pre-transplant graft preconditioning with HOPE results in higher hemodynamic stability during reperfusion and lower incidence of PRS and EAD. HOPE has the potential to mitigate ES by preventing hyperpotassemic complications that need to be addressed in LT with HOPE-pre-treated grafts.

Intraoperative management and early post-operative outcomes of patients with coronary artery disease who underwent orthotopic liver transplantation

BACKGROUND

Coronary artery disease (CAD) is frequently observed in aging end-stage liver disease (ESLD) patients who require orthotopic liver transplantation (OLT). This situation is challenging for both the patients and the medical staff.

METHODS

We retrospectively studied the case records of 26 ESLD patients with CAD who underwent OLT with total clamping of the inferior vena cava between 2014 and 2018. We analyzed the details of the pre-operative evaluation, intraoperative anesthetic management and post-operative prognosis of these patients.

RESULTS

All patients tolerated the anhepatic stage well. Post-reperfusion syndrome (PRS) was observed in 13 patients (50%) and 2 of them were severe but corrected well. ST-segment depression was frequently observed during the anhepatic stage and reperfusion stage. No mortality due to cardiac-related events occurred among the patients during hospitalization. OLT with the modified piggyback technique could successfully be performed in ESLD patients with mild and moderate CAD.

CONCLUSIONS

A thorough evaluation and optimization of recipients, strict monitoring and optimized management of circulation, knowledge of the complicated changes during OLT procedures, and strategies to ameliorate post-reperfusion syndrome favorite the outcomes.

Post-Reperfusion Syndrome in Liver Transplantation: Does a Caval Blood Flush Vent Help?

BACKGROUND Post-reperfusion syndrome (PRS) during liver transplantation can range from a benign event to a profound hemodynamic excursion from baseline with significant morbidity. Multiple variables can be responsible for the diverse presentations. Over time, our group noticed that a blood flush of the liver graft via a caval vent (in addition to a standard chilled flush via the portal vein) appeared to result in a milder reperfusion effect. Attenuation of PRS via caval vent seemed to minimize hemodynamic instability and reduce metabolic derangements associated with reperfusion. MATERIAL AND METHODS This was a prospective observational pilot study of standard practice with the addition of lab values and hemodynamic evaluations. We methodically observed normal clinical flow in 20 adult orthotopic liver transplant recipients. We analyzed blood and fluid samples at set time intervals during the peri-reperfusion phase. RESULTS Sixteen out of 20 patients received a blood flush via caval venting. Mean arterial pressure (MAP) and heart rate were better preserved in the patient population that received a caval blood flush vent. Elevations in central venous pressure (CVP) were similar between the 2 groups. Lab values (blood gas, electrolyte, and hemoglobin) of the patients' blood were similar, with no notable differences. Analysis of the initial blood flushed through the liver graft proved to be hypothermic, acidotic, and hyperkalemic. CONCLUSIONS Pre-reperfusion caval venting in liver transplantation (in addition to a portal vent and a chilled LR/albumin portal flush solution) appears to have favorable hemodynamic effects. The literature on this technique is sparse and larger studies are needed.

Identifying the Superior Reperfusion Technique in Liver Transplantation: A Network Meta-Analysis

Objective

To investigate the clinical effects of different reperfusion techniques in liver transplantation based on network meta-analysis.

Method

Literature retrieval was conducted in globally recognized databases, namely, MEDLINE, EMBASE, and Cochrane Central, to address relative randomized controlled trials (RCTs) investigating the clinical effects of respective reperfusion techniques in liver transplantation. Short- and long-term parametric data, including ICU stay, dysfunction rate (DFR), biliary complications (BC), 1-year graft survival (GS), and patient survival (PS), were quantitatively pooled and estimated based on the Bayesian theorem. The P values of surface under the cumulative ranking (SUCRA) probabilities regarding each parameter were calculated and ranked by various techniques. The Grades of Recommendations Assessment, Development and Evaluation (GRADE) criteria were utilized for the recommendations of evidence from pairwise direct comparisons.

Results

Seven RCTs containing 6 different techniques were finally included for network meta-analysis. The results indicated that retrograde vena cava (RVC) reperfusion possessed the highest possibility of revealing the best clinical effects on DFR (SUCRA, P = 0.93), ICU stay (SUCRA, P = 0.76), and GS (SUCRA, P = 0.44), while portal-arterial reperfusion (simultaneous initialize) seemed to exhibit the most benefits in reducing BC (SUCRA, P = 0.67) and enhancing PS rate (SUCRA, P = 0.48). Moreover, sensitivity analysis with the inconsistency approach clarified the reliability of the main results, and the evidence of the most direct comparisons was ranked low or very low.

Conclusions

Current evidence demonstrated that RVC and portal-arterial reperfusion (simultaneously initialized) revealed superior clinical effects, compared to other interventions. Investigation of these 2 techniques should be a future research direction, and more high-quality RCTs are expected.

Order of liver graft revascularization in deceased liver transplantation: A systematic review and meta-analysis

BACKGROUND

The ideal order for liver graft revascularization during liver transplantation remains unknown. The majority of liver transplant centers prefer portal venous reperfusion followed by arterial reperfusion to shorten the warm ischemia time. The aim of this study was to review the different revascularization techniques used in clinical liver transplantation to identify any potential clinical benefits.

METHODS

A systematic search of 5 databases was performed to identify all available original articles that reported liver transplantation and compared different techniques of reperfusion. The primary outcomes were patient and graft survival. Secondary outcomes were defined by postreperfusion syndrome, primary nonfunction, vascular complications, biliary complications, and retransplantation.

RESULTS

A total of 1,160 patients undergoing liver transplantation from 15 studies were included in this review and meta-analysis. There were no differences regarding the 1-year patient and graft survival for the revascularization techniques. The incidence of primary nonfunction, vascular complications, and retransplantation did not differ between the groups. Although there were no differences regarding biliary complications between the different groups, there were more nonanastomotic strictures in patients with initial portal revascularization (9%) compared with those with simultaneous revascularization (2%; risk ratio 1.07; 95% confidence interval, 1.00-1.14; P = .05; I² = 51%).

CONCLUSION

The order of liver graft revascularization does not influence patient and graft survival. Each revascularization technique offers potential benefits that can be used under specific clinical situations.

Post reperfusion syndrome during liver transplantation: From pathophysiology to therapy and preventive strategies

This review aims at evaluating the existing evidence regarding post reperfusion syndrome, providing a description of the pathophysiologic mechanisms involved and possible management and preventive strategies. A PubMed search was conducted using the MeSH database, “Reperfusion” AND “liver transplantation” were the combined MeSH headings; EMBASE and the Cochrane library were also searched using the same terms. 52 relevant studies and one ongoing trial were found. The concept of post reperfusion syndrome has evolved through years to a multisystemic disorder. The implications of the main organ, recipient and procedure related factors in the genesis of this complex syndrome are discussed in the text as the novel pharmacologic and technical approaches to reduce its incidence. However the available evidence about risk factors, physiopathology and preventive measures is still confusing, the presence of two main definitions and the numerosity of possible confounding factors greatly complicates the interpretation of the studies.

Postreperfusion syndrome during liver transplantation

As surgical and graft preservation techniques have improved and immunosuppressive drugs have advanced, liver transplantation (LT) is now considered the gold standard for treating patients with end-stage liver disease worldwide. However, despite the improved survival following LT, severe hemodynamic disturbances during LT remain a serious issue for the anesthesiologist. The greatest hemodynamic disturbance is postreperfusion syndrome (PRS), which occurs at reperfusion of the donated liver after unclamping of the portal vein. PRS is characterized by marked decreases in mean arterial pressure and systemic vascular resistance, and moderate increases in pulmonary arterial pressure and central venous pressure. The underlying pathophysiological mechanisms of PRS are complex. Moreover, risk factors associated with PRS are not fully understood. Rapid and appropriate treatment with vasopressors, volume replacement, or venesection must be provided depending on the cause of the hemodynamic disturbance when hemodynamic instability becomes profound after reperfusion. The negative effects of PRS on postoperative early morbidity and mortality are clear, but the effect of PRS on postoperative long-term mortality remains a matter of debate.

Graft rinse prior to reperfusion in liver transplantation: literature review and online survey within the Eurotransplant community

Graft rinse prior reperfusion in liver transplantation (LT) is believed to reduce the incidence of postreperfusion syndrome and improve clinical outcome. A MEDLINE search was performed to obtain a comprehensive review of the published literature dealing with graft rinse in LT. Moreover, all thirty-four LT centers in the Eurotransplant (ET) region were invited to participate in an online survey to whether or not graft rinse is performed and whether further research in the field is needed. Seventeen reports have been found to investigate graft rinse protocols in 1894 LT recipients. Eighteen of the thirty centers that participated in the online survey performed graft rinse prior reperfusion in LT. The most commonly used rinse solution was albumin. Nineteen centers stated interest in participating in a multicenter RCT in the field. The published literature does not provide concluding appraisal of the benefit of graft rinse in LT. Graft rinse protocols are not standardized and are based on personal experience. Appropriately designed clinical trials addressing the topic are demanded. The online survey appears to be a helpful tool for the evaluation of clinical practice and future research topics in the transplant community.

Serum acidosis prior to reperfusion facilitates hemodynamic recovery following liver transplantation

INTRODUCTION

Reperfusion is the most critical event during liver transplantation, and sustained leakage of acidic preservation solution from the liver graft contributes to marked hemodynamic instability. Recent laboratory studies with hepatocyte cultures have revealed that low pH may protect hepatocyte mitochondria against ischemia-reperfusion injury by inhibiting the mitochondrial permeability transition (MPT), the so-called "pH paradox." However, the clinical significance of this pH paradox theory remains largely unknown. In this study, we sought to determine whether there is an association between serum pH immediately prior to reperfusion and hemodynamic recovery after reperfusion and graft survival.

METHODS

We analyzed retrospective data from 527 patients who underwent Orthotopic liver transplantation between 2003 and 2008. All patients were allocated to one of two groups: pH ≤ 7.32 or pH > 7.32, as measured 5 min before reperfusion. Case-control matching was performed using the propensity score to adjust for background differences between the two groups. Data were analyzed using Student's t-test and the χ (2) test.

RESULTS

There were 85 patients in the pH ≤ 7.32 group and 385 patients in the pH > 7.32 group. The recovery of mean arterial pressure after hepatic artery reperfusion was significantly faster in the pH ≤ 7.32 group (slope of recovery: 0.0004 % vs. 0.0002 %/min, p = 0.041). Other parameters studied, including vasopressor dosage after reperfusion, did not show any statistically significant difference between groups.

CONCLUSIONS

Our findings suggest that less aggressive treatment of acidosis with a slower rate of normalization of serum pH (from low to normal) after reperfusion promotes faster hemodynamic stabilization. These findings provide evidence to support the concept of the pH paradox, and may also substantiate the argument against the usage of alkalizing agents before reperfusion unless acidosis becomes clinically significant.

Perioperative management of liver transplantation with concurrent coronary artery disease: Report of two cases

Coronary artery disease (CAD), even if asymptomatic, has been known to complicate the perioperative management of patients undergoing liver transplantation. Perioperative outcome for such patients is worse than those without CAD despite improvement in risk stratification and management of CAD. We hereby report the successful perioperative management of two patients with CAD undergoing living-related liver transplantation. Maintaining systemic vascular resistance, goal-directed volume administration and surgical technique avoiding total clamping of IVC was the mainstay of stable intraoperative course. Moreover, a lower model for end stage liver disease (MELD) score at the time of liver transplant may also have been contributory to successful outcome in our patients.

Crystalloid flush with backward unclamping may decrease post-reperfusion cardiac arrest and improve short-term graft function when compared to portal blood flush with forward unclamping during liver transplantation

During liver transplant (LT), the release of vasoactive substances into the systemic circulation is associated with severe hemodynamic instability that is injurious to the recipient and/or the post-ischemic graft. Crystalloid flush with backward unclamping (CB) and portal blood flush with forward unclamping (PF) are two reperfusion methods to reduce reperfusion-related cardiovascular perturbations in our center. The primary aim of this study was to compare these two methods. After institutional review board (IRB) approval, cadaveric whole LT cases performed between 2003 and 2008 were reviewed. Patients were divided into two groups based on reperfusion methods: CB or PF. After background matching with propensity score, the effect of each method on post-operative graft function was assessed in detail. In our cohort of 478 patients, CB was used in 313 grafts and PF in 165. Thirty-day graft survival was lower, and risk of retransplantation was higher in PF. Multivariable model showed that CB is an independent factor to reduce primary non-function, cardiac arrest and improve 30-d graft survival. Also, the incidence of ischemic-type biliary lesions was significantly higher in the PF group. Reperfusion methods affect intraoperative hemodynamics and post-transplant outcome. CB allows for control over temperature and composition of the perfusate, perfusion pressure, and the rate of infusion.

Techniques of flushing and reperfusion for liver transplantation

BACKGROUND

Various techniques of flushing and reperfusion have been advocated to improve outcomes after liver transplantation. There is considerable uncertainty as to which method is superior.

OBJECTIVES

To compare the benefits and harms of different methods of flushing and reperfusion during liver implantation in the transplant recipients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until March 2011.

SELECTION CRITERIA

We included all randomised clinical trials that were performed to compare different techniques of flushing and reperfusion during liver transplantation.

DATA COLLECTION AND ANALYSIS

Two authors independently identified the trials and extracted the data. We analysed the data with both the fixed-effect model and the random-effects model using RevMan analysis. For each outcome we calculated the hazard ratio (HR), risk ratio (RR), rate ratio, mean difference (MD), or standardised mean difference (SMD) with 95% confidence intervals (CI) based on available case analysis.

MAIN RESULTS

We included six trials involving 418 patients for this review. The sample size in the trials varied from 30 to 131 patients. Only one trial involving 131 patients was of low risk of bias for mortality. This trial was at high risk of bias for other outcomes. Four trials excluded patients who underwent liver transplantation for acute liver failure. All the trials included livers obtained from cadaveric donors. The remaining five trials were of high risk of bias for all outcomes. Liver transplantation was performed by the conventional method (caval replacement) in two trials and piggy-back method (caval preservation) in one trial. The method of liver transplantation was not available in the remaining three trials. The comparisons performed included an initial hepatic artery flush versus initial portal vein flush; blood venting via inferior vena cava in addition to venting of storage fluid versus no blood venting; initial hepatic artery reperfusion versus initial portal vein reperfusion; simultaneous hepatic artery and portal vein reperfusion versus initial portal vein reperfusion; and retrograde inferior vena cava reperfusion versus simultaneous hepatic artery and portal vein reperfusion. Only one or two trials could be included under each comparison. There was no significant difference in mortality, graft survival, or severe morbidity rates in any of the comparisons. Quality of life was not reported in any of the trials.

AUTHORS' CONCLUSIONS

There is currently no evidence to support or refute the use of any specific technique of flushing or reperfusion during liver transplantation. Due to the paucity of data, absence of evidence should not be confused with evidence of absence of any differences. Further well designed trials with low risk of systematic error and low risk of random errors are necessary.

Sequential versus contemporaneous portal and arterial reperfusion during liver transplantation

Although sequential portal and arterial revascularization (SPAr) is the most common method of graft reperfusion at liver transplantation (OLT), contemporaneous portal and hepatic artery revascularization (CPAr) has been used to reduce arterial ischemia to the bile ducts. The aim of this study was to prospectively compare SPAr (group 1; n=19) versus CPAr (group 2; n=21) among 40 consecutive OLT from heart-beating donors. There were no differences in the demographics characteristics, Model for End-stage Liver Disease scores, indication for OLT and donor parameters between the groups. OLT was performed using the piggyback technique. The biliary anastomosis was performed in all cases by a duct-to-duct technique with a T-tube in 32% versus 29% of cases without a T tube (P=.83). In the CPAr group, the liver was reperfused simultaneously via the portal vein and hepatic artery. CPAr showed a longer warm ischemia (66 ± 8 vs 37 ± 7 minutes; P<.001), while SPAr had a longer arterial ischemia 103 ± 42 vs 66 ± 8 minutes (P=.0004). Recovery of graft function was similar. There was no primary nonfunction and delayed graft function occurred among 10% versus 9%. Liver function tests were similar between the two groups up to 90 days case of follow-up- One-year graft and patient survivals were, respectively, 89% and 95% versus 94% and 100% (P=.29). At a median follow-up of 13 ± 6 versus 14 ± 7 months, biliary complications included anastomotic stenoses in 15% versus 19% (P=.78) and intrahepatic non-anastomotic biliary strictures in 26% versus none (P=.01) for SPAr and CPAr, respectively. CPAr was safe and feasible, reducing the incidence of intrahepatic biliary strictures by decreasing the duration of arterial ischemia to the intrahepatic bile ducts.

Contemporaneous Portal-Arterial Reperfusion during Liver Transplantation: Preliminary Results

We prospectively compared sequential portal-arterial revascularization (SPAr, group 1 no. 19) versus contemporaneous portal-hepatic artery revascularization (CPAr, group 2 no. 21) in 40 consecutive liver transplantation (LT). There were no differences in the demographics characteristics, MELD score, indication to LT, and donor's parameters between the two groups. CPAr had longer warm ischemia 66 ± 8 versus 37 ± 7 min (P < .001), while SPAr had longer arterial ischemia 103 ± 42 min (P = .0004). One-year patient's and graft survival were, respectively, 89% and 95% versus 94% and 100% (P = .29). At median followup of 13 ± 6 versus 14 ± 7 months biliary complications were anastomotic stenosis in 15% versus 19% (P = .78), and intrahepatic nonanastomotic biliary strictures in 26% versus none (P = .01), respectively, in SPAr and CPAr. CPAr reduces the incidence of intrahepatic biliary strictures by decreasing the duration of arterial ischemia.

Retrograde reperfusion via vena cava lowers the risk of initial nonfunction but increases the risk of ischemic-type biliary lesions in liver transplantation--a randomized clinical trial

Initial nonfunction (INF) and biliary complications such as ischemic-type biliary lesion (ITBL) remain two major complications in clinical orthotopic liver transplantation (OLT). The influence of ischemia and reperfusion injury (I/R) as a significant risk factor for both complications is widely unquestioned. A new reperfusion technique that reduces I/R injury should lead to a reduction in both INF and ITBL. One hundred and thirty two OLT patients were included in this study and randomized into two groups. Group A underwent standard reperfusion with anterograde simultaneous arterial and portal reperfusion and group B received retrograde reperfusion via the vena cava before sequential anterograde reperfusion of portal vein and hepatic artery. Serum transaminase level as a surrogate parameter for I/R injury and serum bilirubin level as a parameter for graft function were significantly reduced during the first week after OLT in group B. INF rate was 7.7% in group A and 0% in group B (P = 0.058). ITBL incidence was 4.55% in group A versus 12.3% in group B (P = 0.053). Retrograde reperfusion seemed to be beneficial for hepatocytes, but was detrimental for the biliary epithelium. The unexplained increased incidence of ITBL after retrograde reperfusion will be focus of further investigation.

Sequential and simultaneous revascularization in adult orthotopic piggyback liver transplantation

The aim of the study was to assess whether there is a difference in outcome after sequential or simultaneous revascularization during orthotopic liver transplantation (OLT) in terms of patient and graft survival, mortality, morbidity, and liver function. The study population consisted of 102 adult patients with primary full-size piggyback OLT transplanted between January 1998 and December 2001. In 71 patients (70%) the grafts were sequentially reperfused after completion of the portal vein anastomosis and subsequent arterial reconstruction was performed (sequential reperfusion [SeqR] group). In 31 patients (30%) the graft was reperfused simultaneously via the portal vein and hepatic artery (simultaneous reperfusion [SimR] group). Patient and graft survival at 1, 3, and 6 months and at 1 year did not differ between the SeqR group and the SimR group. The red blood cell (RBC) requirements were significantly higher in the SimR group (5.5 units; range 0-20) in comparison to the SeqR group (2 units; range 0-19) (P = 0.02). Apart from a higher number of biliary anastomotic complications and abdominal bleeding complications in the SimR group in comparison to the SeqR group (13% vs. 2% and 19% vs. 6%, respectively; P = 0.06), morbidity was not different between the groups. No differences between the groups were observed regarding the incidence of primary nonfunction (PNF), intensive care unit stay, and acute rejection. This was also true for the severity of rejections. Postoperative recuperation of liver function was not different between the groups. In conclusion, no advantage of either of the 2 reperfusion protocols could be observed in this analysis, especially with respect to the incidence of ischemic type biliary lesions (ITBL).

Influence of retrograde flushing via the caval vein on the post-reperfusion syndrome in liver transplantation

INTRODUCTION

The reperfusion phase during orthotopic liver transplantation (LTX) is a critical event with sometimes profound hemodynamic and cardiac changes. We present the influence of retrograde reperfusion in LTX on the post-reperfusion syndrome (PRS).

METHODS

Fifty-six LTXs in 53 patients were performed with the piggy-back technique with retrograde reperfusion via the caval vein and antegrade reperfusion via the portal vein. The incidence of PRS was evaluated.

RESULTS

We observed a PRS in two patients (3.6%), four patients (7.1%) had a decrease in mean arterial pressure (MAP) of 20-29%, 18 patients (32.2%) of 10-19%, 27 patients (48.2%) of 1-9% and five patients (8.9%) had a small increase in MAP.

DISCUSSION

Our retrospective study showed that retrograde reperfusion seems to maintain stability during the reperfusion phase. Hemodynamic disturbances during LTX were uncommon, leading us to suppose that the incidence of PRS could be diminished with retrograde reperfusion.

Factors affecting metabolic and electrolyte changes after reperfusion in liver transplantation

BACKGROUND

The metabolic and electrolyte changes were evaluated after various durations of cold and warm ischemia times to correlate ASA status with hemodynamic changes that may affect the severity of the reperfusion syndrome.

PATIENTS AND METHODS

Sixty-one patients who underwent liver transplantation (OLT) were monitored by arterial pH, PaO2, PaCO2, HCO2, BE, K+, Ca2+, Na+, GL, and serial Ht at three specific times: after the skin incision (baseline), 10 minutes before reperfusion (T2), and 10 minutes after reperfusion (T3). Changes in metabolic parameters were correlated with ASA status, hemodynamic changes, time of OLT, as well as cold and warm ischemia times.

RESULTS

The pH in ASA IV patients was significantly lower at T1 and T3, and PCO2 higher in ASA V at T1. A significant correlation was observed between pH, PaCO2, HCO3-, BE, Na+, Ca2+, and glucose with the phase of the procedure. The pH and HCO3- decreased significantly from T1 and T2, increasing during T3. Ca2+ fell from T1 to T2 increasing in T3. Mean glucose and sodium levels increase from T1 to T3. Mean BE dropped from T1 to T2 and increased at T3 without a significant correlation between the metabolic parameters in any phase of the study and the cold or warm ischemia times. Patients with a high ASA status showed an increased risk for cardiovascular collapse after reperfusion.

CONCLUSIONS

Patients with advanced ASA status are more prone to metabolic and acid-base disturbances during reperfusion, without any relation to the cold or warm ischemia times. High ASA status shows an increased risk for cardiovascular collapse after reperfusion.

Characterization of hepatic parenchymous perfusion heterogeneity and regional flow kinetics after porcine liver transplantation

BACKGROUND

In clinical practice, a heterogeneous hepatic tissue microperfusion (MC) is often observed after liver resection or transplantation (LTx). Nevertheless this hepatic perfusion phenomenon has never been really quantified with respect to its anatomic distribution and time course in detail. The aim of the study was to characterize liver perfusion heterogeneity and local flow kinetics both in the physiological situation and after standardized ischemia and reperfusion using an established model of porcine LTx.

METHODS

Regional distribution of hepatic MC in healthy native porcine livers (control group; n = 8) was analyzed in comparison with data derived 60 min, 24 h, and 72 h after porcine LTx (transplantation group; n = 8 each subgroup; cold ischemia time: 5.7 +/- 1.2 h). MC was measured with implanted thermal diffusion electrodes (TD). Flow in hepatic artery and portal vein was continuously detected by ultrasonic probes. For standardization of measurement localizations, porcine liver lobes were divided anatomically into three horizontal layers (cranial, medial, caudal), defining 12 distinct hepatic measurement regions.

RESULTS

In the control group, a homogenous liver MC with a mean flow of 81.6 +/- 13.9 ml/100 g/min was detected in all regions. After LTx, a marked MC heterogeneity was noted 60 min after reperfusion. MC rehomogenization was first documented within horizontal liver planes 24 h later. Comparison of MC between planes showed persisting heterogeneity with a significant intralober drop of mean MC in the cranio-caudal direction. Complete MC rehomogenization (both between horizontal and vertical liver planes) was detected 72 h after reperfusion. Still, an overall reduction of mean liver perfusion by about 15% was existent.

CONCLUSIONS

A homogenous tissue perfusion was observed in healthy porcine livers. In contrast, marked heterogeneity of hepatic MC was detected after LTx. Heterogeneity presents as a very dynamic and temporary phenomenon. Early horizontal flow rehomogenization and reconstitution of normal blood flow, particularly primarily in the cranial liver layers, appear to be characteristic features during early flow reconstitution after postischemic reperfusion. Due to heterogeneity and time-dependent flow dynamics, measurement of MC volumes at single hepatic regions may not always allow a valid characterization of liver perfusion quality during the first 24 h after postischemic reperfusion.

Presence of methylated arginine derivatives in orthotopic human liver transplantation: relevance for liver function

Orthotopic liver transplantation (OLT) is a frequent option in the treatment of liver diseases. During the cold ischemia period of the donor liver, there is an accumulation of metabolites that are potent inhibitors of the cytokine-inducible and endothelial nitric oxide synthase isoenzymes. We identified the presence of L-N-monomethylarginine and asymmetric dimethylarginine (ADMA) as the main inhibitors by means of analytic high-pressure liquid chromatography and mass spectrometry techniques. An average ADMA concentration of 450 micromol/L was measured in the preservation medium of donor livers with poor outcomes after OLT. A statistically significant relationship was observed between the concentration of methylated arginine derivatives in the graft and liver function after OLT. These data suggest that measurement of methylated arginine, released after liver protein catabolism, might provide an indication of functional status of the liver that can help the development of strategies intended to improve graft viability.

Pathophysiological mechanisms of postrevascularization hyperkalemia in orthotopic liver transplantation

The underlying mechanisms of hyperkalemia occurring immediately after revascularization in orthotopic liver transplantation (OLT) are unknown. We investigated the possible pathophysiological mechanisms of hyperkalemia in relation to the donor and recipient. The study included 64 consecutive patients undergoing OLT. Recipients were divided into two groups: Group 1 consisted of 47 patients with serum K(+) concentration <5.5 mmol/L at 1-min postrevascularization, and Group 2 consisted of 17 patients with serum K(+) exceeding 5.5 mmol/L. Increased serum K(+) concentration, more progressive metabolic acidosis, and decreased mean arterial blood pressure and cardiac index during the anhepatic phase were recognized in Group 2. Multiple regression analysis showed that cardiac index, serum lactate, and serum K(+) concentration during the anhepatic phase were independent and significant factors that could predict serum K(+) concentration 1-min postrevascularization. Hyperkalemia at 1-min postrevascularization did not correlate with the extent of preservation injury of the graft liver (represented by the peak value of aspartate aminotransferase measured within the first 72 h after OLT) or the duration of cold ischemia. We conclude that hyperkalemia occurring immediately after revascularization in OLT is mainly caused by metabolic acidosis as a result of insufficient cardiac output during the anhepatic phase.

Lesão de isquemia e reperfusão hepáticas em cães: estudos histológicos sobre necrose hepatocítica, conteúdo de glicogênio hepático e contagem tecidual de polimorfonucleares

No transplante hepático, a fisiopatologia da lesão de isquemia e reperfusão do fígado não é completamente conhecida. Várias preparações experimentais têm sido usadas para estudos de tal lesão. Para tal fim, no presente trabalho, um modelo modificado foi proposto e avaliado. Vinte cães mestiços, pesando 15,25 ± 1,21 kg, sob anestesia geral, foram distribuídos em dois grupos de investigação: 1. Grupo Teste (n = 10) - os animais foram submetidos a desvascularização de 70% da massa hepática, por período de noventa minutos, seguida de revascularização do fígado. Durante o período de isquemia, a descompressão venosa esplâncnica foi realizada através dos lobos caudado e lateral direito; 2. Grupo Controle (n = 10) - os cães foram submetidos a operação simulada. Em todos os animais foram realizadas biópsias do fígado. O método foi avaliado através de determinações de Necrose Hepatocítica (NH), Conteúdo de Glicogênio Hepático (CGH) e Contagem Tecidual de Polimorfonucleares (CTPMN), realizadas aos cinco minutos antes da isquemia (To) cinco minutos antes da reperfusão (T1) e uma hora (T2) e cinco horas (T3) após a reperfusão. Os resultados permitiram concluir com uma confiança de 95% que: I. Houve aumento progressivo de intensidade de NH e diminuição do CGH durante os estágios de isquemia e de reperfusão hepáticas; 2. Não foi comprovada diferença significativa na CTPMN entre os grupos investigados. As alterações histológicas verificadas são indicativas de NH efetiva, decorrente de isquemia e reperfusão do fígado.