The effect of blood transfusion on pulmonary permeability in cardiac surgery patients: a prospective multicenter cohort study

Perioperative Characteristics and Outcomes of Fontan Versus Non-Fontan Patients Undergoing Combined Heart-Liver Transplantation: A Retrospective Cohort Study

OBJECTIVES

Combined heart-liver transplantation (CHLT) is becoming increasingly frequent as a maturing population of patients with Fontan-palliated congenital heart disease develop advanced liver fibrosis or cirrhosis. The authors present their experience with CHLT for congenital and noncongenital indications, and identify characteristics associated with poor outcomes that may guide intervention in high-risk patients.

DESIGN

This was a single-center retrospective cohort study.

SETTING

This study was conducted at Vanderbilt University Medical Center in Nashville, Tennessee.

PARTICIPANTS

The study included 16 consecutive adult recipients of CHLT at the authors' institution between April 2017 and February 2022.

INTERVENTIONS

Eleven patients underwent transplantation for Fontan indications, and 5 were transplanted for non-Fontan indications.

MEASUREMENTS AND MAIN RESULTS

Compared with non-Fontan patients, Fontan recipients had longer cardiopulmonary bypass duration (199 v 119 minutes, p =m0.002), operative times (786 v 599 minutes, p = 0.01), and larger blood product transfusions (15.4 v 6.3 L, p = 0.18). Six of 16 patients required extracorporeal membrane oxygenation (ECMO), of whom 4 were Fontan patients who subsequently died. Patients who required ECMO had lower 5-hour lactate clearance (0.0 v 3.5 mmol/L, p = 0.001), higher number of vasoactive infusions, lower pulmonary artery pulsatility indices (0.58 v 1.77, p = 0.03), and higher peak inspiratory pressures (28.0 v 18.5 mmHg, p = 0.01) after liver reperfusion.

CONCLUSIONS

Combined heart-liver transplantation in patients with Fontan-associated end-organ disease is particularly challenging and associated with higher recipient morbidity compared with non-Fontan-related CHLT. Early hemodynamic intervention for signs of ventricular dysfunction may improve outcomes in this growing high-risk population.

Three Logistic Predictive Models for the Prediction of Mortality and Major Pulmonary Complications after Cardiac Surgery

Background and Objectives: Pulmonary complications are a leading cause of morbidity after cardiac surgery. The aim of this study was to develop models to predict postoperative lung dysfunction and mortality. Materials and Methods: This was a single-center, observational, retrospective study. We retrospectively analyzed the data of 11,285 adult patients who underwent all types of cardiac surgery from 2003 to 2015. We developed logistic predictive models for in-hospital mortality, postoperative pulmonary complications occurring in the intensive care unit, and postoperative non-invasive mechanical ventilation when clinically indicated. Results: In the "preoperative model" predictors for mortality were advanced age (p < 0.001), New York Heart Association (NYHA) class (p < 0.001) and emergent surgery (p = 0.036); predictors for non-invasive mechanical ventilation were advanced age (p < 0.001), low ejection fraction (p = 0.023), higher body mass index (p < 0.001) and preoperative renal failure (p = 0.043); predictors for postoperative pulmonary complications were preoperative chronic obstructive pulmonary disease (p = 0.007), preoperative kidney injury (p < 0.001) and NYHA class (p = 0.033). In the "surgery model" predictors for mortality were intraoperative inotropes (p = 0.003) and intraoperative intra-aortic balloon pump (p < 0.001), which also predicted the incidence of postoperative pulmonary complications. There were no specific variables in the surgery model predicting the use of non-invasive mechanical ventilation. In the "intensive care unit model", predictors for mortality were postoperative kidney injury (p < 0.001), tracheostomy (p < 0.001), inotropes (p = 0.029) and PaO2/FiO2 ratio at discharge (p = 0.028); predictors for non-invasive mechanical ventilation were kidney injury (p < 0.001), inotropes (p < 0.001), blood transfusions (p < 0.001) and PaO2/FiO2 ratio at the discharge (p < 0.001). Conclusions: In this retrospective study, we identified the preoperative, intraoperative and postoperative characteristics associated with mortality and complications following cardiac surgery.

Autologous red blood cell transfusion does not result in a more profound increase in pulmonary capillary wedge pressure compared to saline in critically ill patients: A randomized crossover trial

Background and Objectives

Transfusion‐associated circulatory overload (TACO) is a major cause of severe transfusion‐related morbidity. Transfusion of red blood cells (RBCs) has been shown to induce hydrostatic pressure overload. It is unclear which product‐specific factors contribute. We set out to determine the effect of autologous RBC transfusion versus saline on pulmonary capillary wedge pressure (PCWP) change.

Materials and Methods

In a randomized crossover trial, patients who had undergone coronary bypass surgery were allocated to treatment post‐operatively in the intensive care unit with either an initial 300 ml autologous RBC transfusion (salvaged during surgery) or 300 ml saline infusion first, followed by the other. Primary outcome was the difference in PCWP change. Secondary outcome measures were the difference in extra‐vascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI).

Results

Change in PCWP was not higher after autologous RBC transfusion compared to saline (ΔPCWP 0.3 ± 0.4 vs. 0.1 ± 0.4 mmHg). ΔEVLWI and ΔPVPI were significantly decreased after autologous RBC transfusion compared to saline (ΔEVLWI −1.6 ± 0.6 vs. 0.2 ± 0.4, p = 0.02; ΔPVPI −0.3 ± 0.1 vs. 0.0 ± 0.1, p = 0.01). Haemodynamic variables and colloid osmotic pressure were not different for autologous RBC transfusion versus saline.

Conclusion

Transfusion of autologous RBCs did not result in a more profound increase in PCWP compared to saline. RBC transfusion resulted in a decrease of EVLWI and PVPI compared to saline. Our data suggest that transfusing autologous RBCs may lead to less pulmonary oedema compared to saline. Future studies with allogeneic RBCs are needed to investigate other factors that may mediate the increase of PCWP, resulting in TACO.

Effect of red blood cell transfusion on inflammation, endothelial cell activation and coagulation in the critically ill

Background and Objectives

Red blood cell (RBC) transfusion is a frequently applied intervention in an intensive care unit. However, transfusion is associated with adverse outcomes including organ failure and thrombo‐embolic events. Mechanisms of these effects are not known but may be related to activation of the endothelium or of the coagulation or inflammatory system. We hypothesized that a RBC transfusion in the critically ill would result in further activation of these systems.

Materials and Methods

In 74 non‐bleeding critically ill patients receiving one RBC unit, markers of inflammation, endothelial cell activation and coagulation were measured before transfusion, at 1 h after transfusion and 24 h after transfusion. The impact of disease severity of the recipient on these changes was assessed by comparing septic and non‐septic patients (according to sepsis‐3 definition) and by correlation of biomarkers with the sequential organ failure assessment (SOFA) score.

Results

Levels of von Willebrand Factor (vWF), soluble ICAM‐1, soluble thrombomodulin, fibrinogen and d‐dimer were already high at baseline, whereas ADAMTS13 levels were low. VWF levels increased significantly 24 h after RBC transfusion (median 478% (338–597) vs. 526% (395–623), p = 0.009). The other biomarkers did not change significantly. Post transfusion change was not dependent on the presence of sepsis and was not correlated with SOFA score.

Conclusion

RBC transfusion in critically ill patients was associated with an increase in circulating vWF levels, suggesting a further increase in activation of the endothelium, a finding that was independent of the presence of sepsis or organ injury level.

Transfusion in the mechanically ventilated patient

Red blood cell transfusions are a frequent intervention in critically ill patients, including in those who are receiving mechanical ventilation. Both these interventions can impact negatively on lung function with risks of transfusion-related acute lung injury (TRALI) and other forms of acute respiratory distress syndrome (ARDS). The interactions between transfusion, mechanical ventilation, TRALI and ARDS are complex and other patient-related (e.g., presence of sepsis or shock, disease severity, and hypervolemia) or blood product-related (e.g., presence of antibodies or biologically active mediators) factors also play a role. We propose several strategies targeted at these factors that may help limit the risks of associated lung injury in critically ill patients being considered for transfusion.

Short-term effects of stored homologous red blood cell transfusion on cardiorespiratory function and inflammation: an experimental study in a hypovolemia model

The pathophysiological mechanisms associated with the effects of red blood cell (RBC) transfusion on cardiopulmonary function and inflammation are unclear. We developed an experimental model of homologous 14-days stored RBC transfusion in hypovolemic swine to evaluate the short-term effects of transfusion on cardiopulmonary system and inflammation. Sixteen healthy male anesthetized swine (68±3.3 kg) were submitted to controlled hemorrhage (25% of blood volume). Two units of non-filtered RBC from each animal were stored under blood bank conditions for 14 days. After 30 min of hypovolemia, the control group (n=8) received an infusion of lactated Ringer's solution (three times the removed volume). The transfusion group (n=8) received two units of homologous 14-days stored RBC and lactated Ringer's solution in a volume that was three times the difference between blood removed and blood transfusion infused. Both groups were followed up for 6 h after resuscitation with collection of hemodynamic and respiratory data. Cytokines and RNA expression were measured in plasma and lung tissue. Stored RBC transfusion significantly increased mixed oxygen venous saturation and arterial oxygen content. Transfusion was not associated with alterations on pulmonary function. Pulmonary concentrations of cytokines were not different between groups. Gene expression for lung cytokines demonstrated a 2-fold increase in mRNA level for inducible nitric oxide synthase and a 0.5-fold decrease in mRNA content for IL-21 in the transfused group. Thus, stored homologous RBC transfusion in a hypovolemia model improved cardiovascular parameters but did not induce significant effects on microcirculation, pulmonary inflammation and respiratory function up to 6 h after transfusion.

Effect of perioperative blood transfusion on postoperative complications after liver transplantation

AIM: To investigate the effect of perioperative blood transfusion on complications after liver transplantation.

METHODS: In order to analyze the relationship between blood transfusion and complications after liver transplantation, the clinical data for 418 patients who underwent liver transplantation from January 1, 2005 to December 31, 2012 at our hospital were analyzed retrospectively.

RESULTS: Of 386 liver transplantation patients, 235 (60.88%) developed postoperative complications and 151 (39.12%) did not occur. The main early complications were lung infection, electrolyte disturbance and reperfusion injury. As the frequency and amount of blood transfused increased, the incidence of complications increased.

CONCLUSION: The higher the frequency and amount of perioperative blood transfusion after liver transplantation, the higher the incidence of complications including infection, electrolyte imbalance, reperfusion injury and so on. Therefore, perioperative blood transfusion should be minimized.

Risk factor analysis of postoperative acute respiratory distress syndrome in valvular heart surgery

PURPOSE

The aim of this study is to investigate the incidence, severity, and outcome of postoperative acute respiratory distress syndrome (ARDS), according to the Berlin definition, in isolated valvular heart surgery. The preoperative and perioperative predisposing factors of this complication were also identified.

METHODS

A retrospective chart review was conducted on 457 patients who underwent isolated valvular heart surgery between January 2010 and December 2012. Clinical characteristics and outcomes were collected. The primary outcome was postoperative ARDS, according to the 2012 Berlin definition for ARDS.

RESULTS

A total of 37 patients (8.1%) developed postoperative ARDS, with a mortality rate of 29.7%. The multivariate analysis identified that age (odds ratios [ORs], 1.067, P ≤ .001), liver cirrhosis (OR, 7.159; P = .001), massive blood transfusion (OR, 2.980; P = .005), and tricuspid valve replacement (OR, 5.197; P = .012) were independent risk factors of postoperative ARDS. Furthermore, we have determined that the increased severity stages of ARDS were associated with decreased postoperative survival.

CONCLUSIONS

In conclusion, postoperative ARDS, according to Berlin definition, in valvular surgery, was associated with high in-hospital mortality. The severity of ARDS was associated with patient midterm mortality. In multivariate analysis, age, liver cirrhosis, massive blood transfusion, and tricuspid valve replacement were identified as independent risk factors of ARDS.

Postoperative Critical Care of the Adult Cardiac Surgical Patient. Part I: Routine Postoperative Care

OBJECTIVES

Cardiac surgery, including coronary artery bypass, cardiac valve, and aortic procedures, is among the most common surgical procedures performed in the United States. Successful outcomes after cardiac surgery depend on optimum postoperative critical care. The cardiac intensivist must have a comprehensive understanding of cardiopulmonary physiology and the sequelae of cardiopulmonary bypass. In this concise review, targeted at intensivists and surgeons, we discuss the routine management of the postoperative cardiac surgical patient.

DATA SOURCE AND SYNTHESIS

Narrative review of relevant English-language peer-reviewed medical literature.

CONCLUSIONS

Critical care of the cardiac surgical patient is a complex and dynamic endeavor. Adequate fluid resuscitation, appropriate inotropic support, attention to rewarming, and ventilator management are key components. Patient safety is enhanced by experienced personnel, a structured handover between the operating room and ICU teams, and appropriate transfusion strategies.

Pulmonary complications of cardiopulmonary bypass

Pulmonary complications after the use of extracorporeal circulation are common, and they range from transient hypoxemia with altered gas exchange to acute respiratory distress syndrome (ARDS), with variable severity. Similar to other end-organ dysfunction after cardiac surgery with extracorporeal circulation, pulmonary complications are attributed to the inflammatory response, ischemia-reperfusion injury, and reactive oxygen species liberated as a result of cardiopulmonary bypass. Several factors common in cardiac surgery with extracorporeal circulation may worsen the risk of pulmonary complications including atelectasis, transfusion requirement, older age, heart failure, emergency surgery, and prolonged duration of bypass. There is no magic bullet to prevent or treat pulmonary complications, but supportive care with protective ventilation is important. Targets for the prevention of pulmonary complications include mechanical, surgical, and anesthetic interventions that aim to reduce the contact activation, systemic inflammatory response, leukocyte sequestration, and hemodilution associated with extracorporeal circulation.

Aortic valve surgery in octogenarians: Risk factors and long-term impact

BACKGROUND AND OBJECTIVES

To understand the risk factors and long-term impact and results of aortic valve surgery in patients over age 80.

PATIENTS AND METHODS

We consecutively evaluated 255 octogenarians who were operated on between 2000 and 2013 and referred for aortic valve disease (isolated or combined with coronary artery disease), which, even when associated with other diseases, was the primary cause of the patient's functional limitation.

RESULTS

The mortality rate decreased from 14.08% (2000-2004) to 7.7% (isolated valve surgery, 4.4%; with coronary bypass, 3.3%) (2010-2013). The independent risk factors associated with mortality were urgent surgery, combined procedures, peripheral vascular disease, a postsurgery hematocrit level <24% and the need for transfusion. More than 50% of the patients experienced a postoperative complication. Blood product transfusions were associated with renal and respiratory failure, and preoperative anemia was associated with an increased rate of myocardial infarction and stroke. Survival at 1, 3, 5 and 10 years was 79.5, 74.3, 63.6 and 30.5%, respectively, with 91.5% of patients in NYHA functional class I-II. Long-term survival was lower for cases of preoperative left ventricular dysfunction. The EuroSCORE I logistics score was not useful for our population as a predictor of mortality or of medium to long-term survival.

CONCLUSIONS

The morbidity and mortality of aortic valve surgery for patients over age 80 has decreased in recent years, although it remains higher when valve surgery is combined with coronary surgery. The presence of preoperative left ventricular dysfunction decreases long-term survival.

Possible transfusion-related acute lung injury (TRALI) in cardiac surgery patients

Aim

To determine the incidence of possible transfusion-related acute lung injury (TRALI) and related risk factors in cardiac surgery patients.

Methods

A single-center prospective cohort study was conducted from January 2009 to March 2010 at the Zagreb University Hospital Center, Croatia. Patient-, transfusion-, and surgery-related data were collected. The study included 262 patients who were observed for respiratory worsening including measurements of arterial oxygen saturation (SaO₂), fraction of inspired oxygen (FiO₂), and partial pressure of arterial oxygen (PaO₂). Possible TRALI was defined according to the Toronto Consensus Conference definition broadened for 24-hour post-transfusion. This cohort was divided in two groups. TRALI group included 32 participants with diagnosis of TRALI and the control group included 220 patients with or without respiratory worsening, but with no signs of ALI.

Results

Possible TRALI was observed in 32 (12.2%) patients. Compared with the control group, possible TRALI patients had higher American Association of Anesthesiology scores, higher rate of respiratory comorbidity (43.8% vs 15.5%), and required more red blood cells (median 4, range [2.5-6] vs 2 [1-3]), plasma (5 [0-6] vs 0 [0-2]), and platelet units (0 [0-8] vs 0 [0-0]) (P < 0.001 all). Risk factors for possible TRALI were total number of transfused blood units (odds ratio [OR] 1.23; 95% confidence interval [CI] 1.10-1.37) and duration of cardiopulmonary bypass (OR 1.08; 95% CI 1.05-1.11). Post-transfusion PaO₂/FiO₂ ratio was significantly decreased in possible TRALI patients and significantly increased in transfused controls without acute lung injury.

Conclusion

We observed a higher rate of possible TRALI cases than in other studies on cardiac surgery patients. Serial monitoring of PaO₂/FiO₂ ratio and detection of its post-transfusion worsening aids in identification of possible TRALI cases.

Anemia and red blood cell transfusion in critically ill cardiac patients

Anemia and red blood cell (RBC) transfusion occur frequently in hospitalized patients with cardiac disease. In this narrative review, we report the epidemiology of anemia and RBC transfusion in hospitalized adults and children (excluding premature neonates) with cardiac disease, and on the outcome of anemic and transfused cardiac patients. Both anemia and RBC transfusion are common in cardiac patients, and both are associated with mortality. RBC transfusion is the only way to rapidly treat severe anemia, but is not completely safe. In addition to hemoglobin (Hb) concentration, the determinant(s) that should drive a practitioner to prescribe a RBC transfusion to cardiac patients are currently unclear. In stable acyanotic cardiac patients, Hb level above 70 g/L in children and above 70 to 80 g/L in adults appears safe. In cyanotic children, Hb level above 90 g/L appears safe. The appropriate threshold Hb level for unstable cardiac patients and for children younger than 28 days is unknown. The optimal transfusion strategy in cardiac patients is not well characterized. The threshold at which the risk of anemia outweighs the risk of transfusion is not known. More studies are needed to determine when RBC transfusion is indicated in hospitalized patients with cardiac disease.

Soluble receptor for advanced glycation end products as an indicator of pulmonary vascular injury after cardiac surgery

Background

Cardiac surgery is frequently complicated by an acute vascular lung injury and this may be mediated, at least in part, by the (soluble) receptor for advanced glycation end products (sRAGE).

Methods

In two university hospital intensive care units, circulating sRAGE was measured together with the ⁶⁸Gallium-transferrin pulmonary leak index (PLI), a measure of pulmonary vascular permeabiliy, in 60 consecutive cardiac surgery patients stratified by the amount of blood transfusion, within 3 hours of admission to the intensive care.

Results

Cardiac surgery resulted in elevated plasma sRAGE levels compared to baseline (315 ± 181 vs 110 ± 55 pg/ml, P = 0.001). In 37 patients the PLI was elevated 50% above normal. The PLI correlated with sRAGE (r² = 0.11, P = 0.018). Plasma sRAGE discriminated well between those with an elevated PLI and those with a normal PLI (area under the operator curve 0.75; P = 0.035; 95% CI 0.55-0.95), with 91% sensitivity but low specificity of 36% at a cutoff value of 200 pg/mL. Blood transfusion did not influence sRAGE levels.

Conclusions

sRAGE is elevated in plasma after cardiac surgery and indicates increased pulmonary vascular permeability. The level of sRAGE is not affected by transfusion.

[Spleen injuries during colorectal carcinoma surgery. Effect on the early postoperative result]

INTRODUCTION

Unlike gastric carcinomas, the consequences of spleen damage during operative treatment of colorectal carcinoma have barely been investigated, as splenectomy is not performed on these tumor patients to extend the radicality. In this context, the only interest is in the iatrogenic intraoperative spleen lesions, which make a splenectomy necessary or require reconstructive spleen preservation.

METHODOLOGY

During the study period from January 2000 to the end of December 2004 the perioperative data of a prospective multicenter observational study of 46,682 Patients whose tumor had been removed with a curative or palliative intent were analyzed with respect to the early postoperative consequences of an iatrogenic spleen lesion.

RESULTS

Of these 46,682 Patients, 640 (1.4%) suffered an iatrogenic spleen injury during the operative therapy. The spleens of 127 Patients (0.3%) were removed and the spleens of 513 Patients (1.1%) could be left in situ following repair. In more than 80% of the cases with an iatrogenic spleen injury, the tumor was localized in the left colon and in the rectum. Logistic regression analysis showed that the decisive risk factor for this organ lesion was the mobilization of the left colonic flexure with tumor localization in the left colon and rectum. Following spleen lesion a significantly higher morbidity rate was registered (47.2% following splenectomy, 48.5% following spleen repair) compared to patients without spleen injury (36.5%). Anastomotic leaks requiring surgery were most frequently observed following splenectomy (7.9%) but this was significantly lower following spleen preservation (3.3%, p = 0.003). The total hospital mortality was 3.1%. In patients with splenectomy the hospital mortality was 11.8% and subsequent repair with organ preservation was 4.7% (p < 0.0001).

CONCLUSIONS

Iatrogenic spleen lesions during colorectal carcinoma surgery represent a significant risk factor for a poor early postoperative result. In particular, this concerns the high rate of anastomotic leaks and infectious septic complications. This also leads to a higher rate of total morbidity and hospital mortality. By comparison significantly worse postoperative results were found in the group of splenectomised patients compared to the group with organ preservation through repair of the injured spleen.

Inhibition of lysophosphatidic acid increase by prestorage whole blood leukoreduction in autologous CPDA-1 whole blood

BACKGROUND

Lysophosphatidylcholine (LPC) has been implicated in the onset of transfusion-related acute lung injury (TRALI). In plasma, LPC is converted to lysophosphatidic acid (LPA) by autotaxin (ATX). The effect of leukoreduction in the accumulation of these bioactive lipids and ATX in human autologous blood has not been fully investigated.

STUDY DESIGN AND METHODS

The accumulation of choline-containing phospholipids (LPC, sphingomyelin [SM], and phosphatidylcholine [PC]), LPA, and ATX during the storage of autologous blood and the changes caused by leukoreduction were investigated. A total of 26 orthopedic patients were enrolled. Autologous blood was collected as whole blood and, after leukoreduction, preserved refrigerated until use. Prestorage leukoreduced (LR) and non-LR autologous blood samples were analyzed. The time-dependent changes and the effect of the filtration were compared.

RESULTS

A time-dependent and significant increase in the levels of LPA was observed in both non-LR and LR samples. The concentration of LPA was significantly reduced in LR compared to non-LR samples. The concentration of LPC was higher in LR compared to non-LR samples. The levels of PC, SM, and ATX were not affected by either the storage period or the leukoreduction.

CONCLUSIONS

Leukoreduction of autologous whole blood effectively reduced the accumulation of LPA. On the other hand, prestorage leukoreduction resulted in an increased concentration of LPC, without significantly affecting ATX. Further studies are necessary to confirm the role of LPA in the pathogenesis of adverse effects of blood transfusion, especially TRALI.

Mini-extracorporeal circulation minimizes coagulation abnormalities and ameliorates pulmonary outcome in coronary artery bypass grafting surgery

Hemostasis is impaired during CABG and coagulation abnormalities often result in clinically relevant organ dysfunctions, eventually increasing morbidity and mortality rates. Fifteen consecutive patients with coronary artery disease submitted to conventional extracorporeal circulation (cECC) have been compared with 15 matched patients, using mini-ECC (MECC). Postoperative lung function was evaluated according to gas exchange, intubation time and lung injury score. In the MECC group, thrombin-antithrombin complex levels (TaTc), prothrombin fragments (PF1+2) formation and thromboelastography (TEG) clotting times were lower compared to the cECC group (p=0.002 and p<0.001, respectively) whereas postoperative blood loss was higher in the cECC group (p=0.030) and more patients required blood transfusion (p=0.020). In the MECC group, postoperative gas exchange values were better, intubation time shorter and lung injury score lower (p<0.001 for all comparisons). Our study suggests that MECC induces less coagulation disorders, leading to lower postoperative blood loss and better postoperative lung function. This approach may be advantageous in high-risk patients.

Pulmonary complications of transfused blood components

Three transfusion complications are responsible for the majority of the morbidity and mortality in hospitalized patients. This article discusses the respiratory complications associated with these pathophysiologic processes, including definitions, diagnosis, mechanism, incidence, risk factors, clinical management, and strategies for prevention. It also explores how different patient populations and different blood components differentially affect the risk of these deadly transfusion complications. Lastly, the article discusses how health care providers can risk stratify individual patients or patient populations to determine whether a given transfusion is more likely to benefit or harm the patient based on the transfusion indication, risk, and expected result.

Pre-treatment with allopurinol or uricase attenuates barrier dysfunction but not inflammation during murine ventilator-induced lung injury

Introduction

Uric acid released from injured tissue is considered a major endogenous danger signal and local instillation of uric acid crystals induces acute lung inflammation via activation of the NLRP3 inflammasome. Ventilator-induced lung injury (VILI) is mediated by the NLRP3 inflammasome and increased uric acid levels in lung lavage fluid are reported. We studied levels in human lung injury and the contribution of uric acid in experimental VILI.

Methods

Uric acid levels in lung lavage fluid of patients with acute lung injury (ALI) were determined. In a different cohort of cardiac surgery patients, uric acid levels were correlated with pulmonary leakage index. In a mouse model of VILI the effect of allopurinol (inhibits uric acid synthesis) and uricase (degrades uric acid) pre-treatment on neutrophil influx, up-regulation of adhesion molecules, pulmonary and systemic cytokine levels, lung pathology, and regulation of receptors involved in the recognition of uric acid was studied. In addition, total protein and immunoglobulin M in lung lavage fluid and pulmonary wet/dry ratios were measured as markers of alveolar barrier dysfunction.

Results

Uric acid levels increased in ALI patients. In cardiac surgery patients, elevated levels correlated significantly with the pulmonary leakage index. Allopurinol or uricase treatment did not reduce ventilator-induced inflammation, IκB-α degradation, or up-regulation of NLRP3, Toll-like receptor 2, and Toll-like receptor 4 gene expression in mice. Alveolar barrier dysfunction was attenuated which was most pronounced in mice pre-treated with allopurinol: both treatment strategies reduced wet/dry ratio, allopurinol also lowered total protein and immunoglobulin M levels.

Conclusions

Local uric acid levels increase in patients with ALI. In mice, allopurinol and uricase attenuate ventilator-induced alveolar barrier dysfunction.