Nitroglycerin versus epoprostenol: effects on hemodynamics, oxygen delivery, and hepatic venous oxygenation after liver transplantation

Correlation of hepatic venous saturation and mixed venous saturation: pooled analyses

INTRODUCTION

In critical care, monitoring adequate tissue oxygenation is essential. Mixed venous oxygen saturation has traditionally been considered the gold standard for measuring cardiac output, which represents systemic oxygen delivery. Studies have shown that hepatic vein saturation is correlated with mixed venous oxygen saturation and mortality. The primary aim of this study was to determine the correlation between hepatic vein saturation and mixed venous saturation, and the impact of clinical characteristics on this correlation.

EVIDENCE ACQUISITION

A systematic review of the literature was performed to identify manuscripts. They must have included patients who received simultaneous mixed venous saturations and hepatic vein saturations, and the data for both must have been explicitly shared. Data were pooled from these studies to analyze the correlation between mixed venous saturation and the corresponding hepatic vein saturation.

EVIDENCE SYNTHESIS

A total of 13 studies with 333 patients were included in the final analyses. The average age across these studies was 60.3±5.2. The pooled correlation between the mixed venous saturation and hepatic vein saturation was 0.88, demonstrating a strong correlation between the two. The average mixed venous saturation was 73.3±5.0 while the average hepatic vein saturation was 59.5±11.1.

CONCLUSIONS

In these pooled analyses, hepatic vein saturation has a strong correlation with mixed venous saturation. This correlation is not significantly impacted by patient age, weight, or clinical setting. Nonetheless, further prospective studies are needed for confirmation.

Prostaglandins for adult liver transplanted recipients

BACKGROUND

Prostaglandins are naturally occurring lipids that are synthesised from arachidonic acid. Multiple studies have evaluated the benefits of prostaglandins in reducing ischaemia reperfusion injury after liver transplantation. New studies have been published since the previous review, and hence it was important to update the evidence for this intervention.

OBJECTIVES

To evaluate the benefits and harms of prostaglandins in adults undergoing liver transplantation compared with placebo or standard care.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 27 December 2022.

SELECTION CRITERIA

We included randomised clinical trials evaluating prostaglandins initiated in the perioperative period compared with placebo or standard care for adults undergoing liver transplantation. We included trials irrespective of reported outcomes.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. all-cause mortality, 2. serious adverse events, and 3. health-related quality of life. Our secondary outcomes were 4. liver retransplantation, 5. early allograft dysfunction, 6. primary non-function of the allograft, 7. acute kidney failure, 8. length of hospital stay, and 9. adverse events considered non-serious. We used GRADE to assess certainty of evidence.

MAIN RESULTS

We included 11 randomised clinical trials with 771 adult liver transplant recipients (mean age 47.31 years, male 61.48%), of whom 378 people were randomised to receive prostaglandins and 393 people were randomised to either placebo (272 participants) or standard care (121 participants). All trials were published between 1993 and 2016. Ten trials were conducted in high- and upper-middle-income countries. Prostaglandins may reduce all-cause mortality up to one month (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.61 to 1.23; risk difference (RD) 21 fewer per 1000, 95% CI 63 fewer to 36 more; 11 trials, 771 participants; low-certainty evidence). Prostaglandins may result in little to no difference in serious adverse events (RR 0.92, 95% CI 0.60 to 1.40; RD 81 fewer per 1000, 95% CI 148 fewer to 18 more; 6 trials, 568 participants; low-certainty evidence). None of the included trials reported health-related quality of life. Prostaglandins may result in little to no difference in liver retransplantation (RR 0.98, 95% CI 0.49 to 1.96; RD 1 fewer per 1000, 95% CI 33 fewer to 62 more; 6 trials, 468 participants; low-certainty evidence); early allograft dysfunction (RR 0.62, 95% CI 0.33 to 1.18; RD 137 fewer per 1000, 95% CI 241 fewer to 47 more; 1 trial, 99 participants; low-certainty evidence); primary non-function of the allograft (RR 0.58, 95% CI 0.26 to 1.32; RD 23 fewer per 1000, 95% CI 40 fewer to 16 more; 7 trials, 624 participants; low-certainty evidence); and length of hospital stay (mean difference (MD) -1.15 days, 95% CI -5.44 to 3.14; 4 trials, 369 participants; low-certainty evidence). Prostaglandins may result in a large reduction in the development of acute kidney failure requiring dialysis (RR 0.42, 95% CI 0.24 to 0.73; RD 100 fewer per 1000, 95% CI 132 fewer to 49 fewer; 5 trials, 477 participants; low-certainty evidence). The evidence is very uncertain about the effect of prostaglandins on adverse events considered non-serious (RR 1.19, 95% CI 0.42 to 3.36; RD 225 fewer per 1000, 95% CI 294 fewer to 65 fewer; 4 trials, 329 participants; very low-certainty evidence). Two trials reported receiving funding; one of these was with vested interests. We found one registered ongoing trial.

AUTHORS' CONCLUSIONS

Eleven trials evaluated prostaglandins in adult liver transplanted recipients. Based on low-certainty evidence, prostaglandins may reduce all-cause mortality up to one month; may cause little to no difference in serious adverse events, liver retransplantation, early allograft dysfunction, primary non-function of the allograft, and length of hospital stay; and may have a large reduction in the development of acute kidney injury requiring dialysis. We do not know the effect of prostaglandins on adverse events considered non-serious. We lack adequately powered, high-quality trials evaluating the effects of prostaglandins for people undergoing liver transplantation.

Prostaglandins for adult liver transplanted patients

BACKGROUND

Prostaglandins may reduce ischaemic injury after liver transplantation. Several small randomised trials have evaluated the effects of prostaglandins in patients undergoing liver transplantation. Results of these trials are inconsistent, and none has enough power to reliably exclude effects of prostaglandins.

OBJECTIVES

To assess the benefits and harms of prostaglandin E1 or E2 in adult liver-transplanted patients.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and LILACS (search on 20 April 2011). In addition, we perused the reference lists of the identified studies and contacted trials investigators, and national and international experts in order to identify more trials for the review.

SELECTION CRITERIA

We included randomised clinical trials evaluating prostaglandin E1 or E2 initiated in the perioperative period versus placebo or standard treatment for adult patients undergoing liver transplantation. We did not apply any language or publication status restrictions.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated methodological quality, ie, risk of bias of the included trials, and extracted data using standardised data extraction forms. We contacted trial investigators in attempt to retrieve information not available in the original manuscripts. We used random-effects model meta-analyses and fixed-effect model meta-analyses to estimate the odds ratio with 95% confidence interval (CI).

MAIN RESULTS

We included ten trials in which 652 patients were randomised. The risk of bias was considered high in most trials. There was no significant effect of prostaglandins on all-cause mortality (37/298[12.4%] in prostaglandin group versus 47/312[15.1%] in control group; OR 0.84, 95% CI 0.53 to 1.37; I(2) = 0%), on primary non-function of the allograft (8/238 [3.4%] versus. 16/250[6.4%] ;OR 0.55, 95% CI 0.23 to 1.33; I(2) = 0%), and on liver re-transplantation (12/161[7.5%] versus 14/171[8.2%]; OR 0.99, 95% CI 0.44 to 2.25; I(2) = 0%). Prostaglandins seemed to significantly decrease the risk of acute kidney failure requiring dialysis (13/158[8.2%] versus 34/171[9.9%]; OR 0.37, 95% CI 0.18 to 0.75; I(2) = 0%). There was no significant increase in the risk of adverse events with prostaglandins.

AUTHORS' CONCLUSIONS

We found no evidence that the administration of prostaglandins to liver transplanted patients reduces the risk of death, primary non-function of the allograft, or liver re-transplantation. Prostaglandins might reduce the risk of acute kidney failure requiring dialysis, but the quality of the evidence is considered only moderate due to high risk of bias in most of the included trials. Moreover, there are risks of outcome measure reporting bias and random errors. Therefore, further randomised, placebo-controlled trials are deemed necessary.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Prostacyclin in sepsis: A systematic review

According to current literature, infective processes greatly modify both vascular hemodynamics and anti-oxidant properties of affected tissues, causing a change in homeostasis that regulates the correct functioning of all cells responsible for the physiological and metabolic balance of various organs. As a consequence, the response to the infection that has caused the change is also likely to be weaker and, in the case of septic shock, ineffective. In this review, we will take into consideration these mechanisms and then focus on a group of vasodilator drugs (prostacyclin and its analogs) which, though have been used for over 20 years mainly to treat obstructive vascular diseases, have such hemodynamic and anti-inflammatory properties which prevent homeostatic changes. It is obvious that prostacyclin does not definitively have anti-infective characteristics; however, in association with anti-infective drugs (antibiotics, etc.), the effectiveness of the latter appears improved, at least in some circumstances. Similarly, the fact that prostacyclin and its analogs have a cytoprotective effect on the liver and reduce the ischemia-reperfusion damage following liver transplant is not a novelty and evidence that they improve hepatic hemodynamics suggests their use in those pathologies characterized by possible reduced perfusion or ascertained ischemia of the liver.

Small-dose epoprostenol decreases systemic oxygen consumption and splanchnic oxygen extraction during normothermic cardiopulmonary bypass

Normothermic, nonpulsatile cardiopulmonary bypass (CPB) impairs systemic and splanchnic oxygen transport and increases gastrointestinal permeability. It is an important therapeutic goal to avoid splanchnic dysoxia during CPB. Small-dose prostacyclin therapy improves splanchnic oxygen transport and microcirculation in septic patients. In this study, we sought to determine if during cardiac surgery, the prostacyclin analog epoprostenol improves the balance of systemic and splanchnic oxygen transport. Eighteen patients undergoing cardiac valve replacement were randomized to receive either epoprostenol (3 ng x kg(-1) x min(-1)) or placebo during, and for 1 hour after, surgery. Systemic and splanchnic oxygen delivery, consumption, and extraction and arterial, mixed venous, and hepato-venous lactate concentrations were measured before, during, and after CPB. Gastrointestinal permeability was measured 1 day before and 1 day after surgery using the triple sugar permeability test. During CPB, the epoprostenol group had decreased systemic oxygen consumption and splanchnic oxygen extraction (P = 0.024). These effects were not present 1 hour after the end of epoprostenol infusion. The study was not adequately powered to determine whether epoprostenol altered the trend towards increased lactate metabolism and increased postoperative gastrointestinal permeability, nor could we demonstrate any differences between groups in clinically relevant end-points. In conclusion, these findings suggest that during normothermic CPB, small-dose epoprostenol therapy may reduce systemic oxygen consumption and splanchnic oxygen extraction.

Preconditioning with the prostacyclin analog epoprostenol and cobra venom factor prevents reperfusion injury and hyperacute rejection in discordant liver xenotransplantation

Liver xenografts transplanted from guinea pig to rat suffer from inadequate organ reperfusion and initial dysfunction, despite sufficient complement depletion using cobra venom factor (CVF). Reperfusion injury is prevented when complement depleted donors are treated with the prostacyclin analog epoprostenol. Histological analysis suggests that epoprostenol preconditioning prevents post-reperfusion spasms of the intrahepatic branches of the portal vein and strongly reduces appearance of hepatocyte apoptosis shortly after transplantation. Cobra-venom-treated rats show breakdown of glucose metabolism and die in acute hypoglycaemia, whereas the additional application of epoprostenol restores gluconeogenesis. Consequently, recipient survival after epoprostenol and CVF treatment is significantly improved compared with animals receiving CVF only (5.1 +/- 2.6 h vs. 17.9 +/- 5.1 h). These data demonstrate that initial dysfunction of discordant liver grafts in the guinea-pig-to-rat species combination, can be overcome by the application of epoprostenol combined with CVF. Using this pharmacologic regimen, the discordant guinea-pig-to-rat model appears useful to study further questions concerning functional and immunological compatibility of a discordant liver xenograft.

Progressive portopulmonary hypertension after liver transplantation treated with epoprostenol

Portopulmonary hypertension (PPHTN) is an uncommon complication of advanced liver disease. Epoprostenol has been effective in the treatment of PPHTN and has been used as a bridge to orthotopic liver transplantation (OLT). The role of OLT in the reversal of PPHTN is unclear. We report a case of severe PPHTN (mean pulmonary artery pressure of 45 mm Hg) that progressed after OLT. Acute dosing with epoprostenol improved the pulmonary vascular resistance by 55% and the cardiac index by 134%. Hemodynamic and symptomatic improvements were maintained after 18 months of long-term treatment with epoprostenol. This is the first reported case of a successful favorable outcome after treatment for progressive PPHTN after OLT. Our case report complements previous reports by highlighting the potential effective use of epoprostenol as a definitive treatment for PPHTN.

Administration of prostacyclin after liver transplantation: a placebo controlled randomized trial

The shortage of suitable organs for liver grafts is responsible for the use of marginal donors for liver transplantation (OLT). If these liver grafts function poorly initially after OLT, a supportive therapy is necessary. The purpose of this study was to evaluate the effects of prostacyclin (PGI2) on postoperative liver graft function after OLT. A total of 30 adult recipients of primary OLT were randomized to either receive PGI2 (4 ng/kg per min body weight, n = 15) or a placebo for 6 d. To evaluate regional splanchnic oxygenation a fiberoptic pulmonary-artery catheter was inserted into a hepatic vein and the difference between mixed venous oxygen content and hepatic venous oxygen content was determined (deltaO2). Measurements were performed directly after transplantation and at 6, 12, 24 and 48 h postoperatively. A significant correlation between deltaO2 and the level of transaminases (ALT/AST) was observed 24 and 48 h after transplantation (p < 0.05). PGI2 treatment induced a significant decrease in deltaO2 after 24 and 48 h after reperfusion (p < 0.05). Peak AST levels tended to be lower in the PGI2 treatment group (418 +/- 99 vs. 638 +/- 156 U/L, p < 0.1). These results suggest that administration of PGI2 after OLT improves hepatic-splanchnic oxygenation and may thereby reduce reperfusion injury after OLT.