A New Global Definition of Acute Respiratory Distress Syndrome.

Background: Since publication of the 2012 Berlin definition of acute respiratory distress syndrome (ARDS), several developments have supported the need for an expansion of the definition, including the use of high-flow nasal oxygen, the expansion of the use of pulse oximetry in place of arterial blood gases, the use of ultrasound for chest imaging, and the need for applicability in resource-limited settings. Methods: A consensus conference of 32 critical care ARDS experts was convened, had six virtual meetings (June 2021 to March 2022), and subsequently obtained input from members of several critical care societies. The goal was to develop a definition that would 1) identify patients with the currently accepted conceptual framework for ARDS, 2) facilitate rapid ARDS diagnosis for clinical care and research, 3) be applicable in resource-limited settings, 4) be useful for testing specific therapies, and 5) be practical for communication to patients and caregivers. Results: The committee made four main recommendations: 1) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2) use PaO2:FiO2 ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry SpO2:FiO2 ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify hypoxemia; 3) retain bilateral opacities for imaging criteria but add ultrasound as an imaging modality, especially in resource-limited areas; and 4) in resource-limited settings, do not require positive end-expiratory pressure, oxygen flow rate, or specific respiratory support devices. Conclusions: We propose a new global definition of ARDS that builds on the Berlin definition. The recommendations also identify areas for future research, including the need for prospective assessments of the feasibility, reliability, and prognostic validity of the proposed global definition.

Evaluation of GSK2789917-induced TRPV4 inhibition in animal models of fluid induced lung injury.

Administration of bolus intravenous fluids, common in pre-hospital and hospitalised patients, is associated with increased lung vascular permeability and mortality outside underlying disease states. In our laboratory, the induction of lung injury and oedema through rapid administration of intravenous fluid in rats was reduced by a non-specific antagonist of transient receptor potential vanilloid 4 (TRPV4) channels. The aims of this study were to determine the effect of selective TRPV4 inhibition on fluid-induced lung injury (FILI) and compare the potency of FILI inhibition to that of an established model of TRPV4 agonist-induced lung oedema. In a series of experiments, rats received specific TRPV4 inhibitor (GSK2789917) at high (15 µg/kg), medium (5 µg/kg) or low (2 µg/kg) dose or vehicle prior to induction of lung injury by intravenous infusion of TRPV4 agonist (GSK1016790) or saline. GSK1016790 significantly increased lung wet weight/body weight ratio by 96% and lung wet-to-dry weight ratio by 43% in vehicle pre-treated rats, which was inhibited by GSK2789917 in a dose-dependent manner (IC50 = 3 ng/mL). Similarly, in a single-dose study, bolus saline infusion significantly increased lung wet weight/body weight by 17% and lung wet-to-dry weight ratio by 15%, which was attenuated by high dose GSK2789917. However, in a final GSK2789917 dose-response study, inhibition did not reach significance and an inhibitory potency was not determined due to the lack of a clear dose-response. In the FILI model, TRPV4 may have a role in lung injury induced by rapid-fluid infusion, indicated by inconsistent amelioration with high dose TRPV4 antagonist.

Monocyte chemotactic protein (MCP)-1 (CCL2) and its receptor (CCR2) are elevated in chronic heart failure facilitating lung monocyte infiltration and differentiation which may contribute to lung fibrosis.

BACKGROUND: Dyspnea, the cardinal manifestation of chronic heart failure (CHF), may reflect both pulmonary oedema and pulmonary remodeling resulting in tissue stiffening. Emerging evidence suggests that predominance of distinct phenotypes of alveolar and recruited macrophages, designated M1 and M2, may regulate the course of inflammatory tissue repair and remodeling in the lung. METHODS: In a CHF rat model, we found fibrotic reinforcement of the extracellular matrix with an increase in monocyte chemotactic protein (MCP)-1/CCL2 in bronchoalveolar lavage (BAL), corresponding to a 3-fold increase in recruited macrophages. In this clinical cross sectional study, we aimed to examine potential mediators of leukocyte activation and lung infiltration in parallel BAL and blood from CHF patients compared to non-CHF controls. RESULTS: Mini-BAL and peripheral blood samples were obtained from hospitalized CHF, acute decompensated CHF and non-CHF patients. CHF patients and decompensated CHF patients demonstrated increases from non-CHF patients in BAL MCP-1, as well as the M2 macrophage cytokines interleukin-10 and transforming growth factor-ß. BAL and plasma MCP-1 were significantly correlated; however, MCP-1 was 20-fold higher in epithelial lining fluid in BAL, indicative of an alveolar chemotactic gradient. An increase in transglutaminase 2 positive M2 macrophages in parallel with a decrease in the MCP-1 receptor, CC chemokine receptor 2 (CCR2), was apparent in BAL cells of CHF patients compared to non-CHF. CONCLUSION: These data suggest a pathway of MCP-1 mediated M2 macrophage prevalence in the lungs of CHF patients which may contribute to pulmonary fibrotic remodeling and consequent increased severity of dyspnea.

ADMA and homoarginine independently predict mortality in critically ill patients.

BACKGROUND: Arginine metabolites are associated with cardiovascular and all-cause mortality in several patient groups. We investigated whether arginine metabolites are associated with mortality in patients with critical illness and whether associations are independent of other factors affecting prognosis in an Intensive Care Unit (ICU). METHODS: 1155 acutely unwell adult patients admitted to a mixed medical-surgical ICU were studied. Arginine, asymmetric dimethyl-l-arginine (ADMA), monomethyl-l-arginine (MMA), symmetric dimethyl-l-arginine (SDMA) and l-homoarginine were measured in a plasma sample collected at admission to ICU by liquid chromatography tandem mass spectrometry. Risk of death score was calculated using data submitted to the Australia and New Zealand Intensive Care Society. RESULTS: In this cohort, 163 patients (14.1%) died. ADMA (odds ratio = 1.159 (1.033-1.300) per 0.1 µmol/L increment, p = 0.012), homoarginine (odds ratio = 0.963 (0.934-0.992), p = 0.013) and risk of death score (odds ratio = 1.045 (1.037-1.053) per 1% increment, p < 0.001) were independently associated with mortality in ICU patients. The area under the receiver operator characteristic curve for risk of death score, ADMA and homoarginine combined for mortality was greater than for risk of death score alone (0.815 (95% CI 0.790-0.837) vs 0.796 (95% CI 0.781-0.820), p = 0.019). Other arginine metabolites were not independently associated with mortality. CONCLUSIONS: ADMA is positively and homoarginine negatively associated with mortality in ICU patients, independent of other clinical factors. Measuring ADMA and homoarginine may refine models to predict ICU mortality. Reducing ADMA and increasing homoarginine are potential therapeutic targets to reduce mortality in critically ill patients.

Hospital-acquired complications: the relative importance of hospital- and patient-related factors.

OBJECTIVE: To quantify the prevalence of hospital-acquired complications; to determine the relative influence of patient- and hospital-related factors on complication rates. DESIGN, PARTICIPANTS: Retrospective analysis of administrative data (Integrated South Australian Activity Collection; Victorian Admitted Episodes Dataset) for multiple-day acute care episodes for adults in public hospitals. SETTING: Thirty-eight major public hospitals in South Australia and Victoria, 2015-2018. MAIN OUTCOME MEASURES: Hospital-acquired complication rates, overall and by complication class, by hospital and hospital type (tertiary referral, major metropolitan service, major regional service); variance in rates (intra-class correlation coefficient, ICC) at the patient, hospital, and hospital type levels as surrogate measures of their influence on rates. RESULTS: Of 1 558 978 public hospital episodes (10 029 918 bed-days), 151 486 included a total of 214 286 hospital-acquired complications (9.72 [95% CI, 9.67-9.77] events per 100 episodes; 2.14 [95% CI, 2.13-2.15] events per 100 bed-days). Complication rates were highest in tertiary referral hospitals (12.7 [95% CI, 12.6-12.8] events per 100 episodes) and for episodes including intensive care components (37.1 [95% CI, 36.7-37.4] events per 100 episodes). For all complication classes, inter-hospital variation was determined more by patient factors (overall ICC, 0.55; 95% CI, 0.53-0.57) than by hospital factors (ICC, 0.04; 95% CI, 0.02-0.07) or hospital type (ICC, 0.01; 95% CI, 0.001-0.03). CONCLUSIONS: Hospital-acquired complications were recorded for 9.7% of hospital episodes, but patient-related factors played a greater role in determining their prevalence than the treating hospital.

Induced hypernatremia in patients with moderate-to-severe ARDS: a randomized controlled study.

BACKGROUND: Induced hypernatremia and hyperosmolarity is protective in animal models of lung injury. We hypothesized that increasing and maintaining plasma sodium between 145 and 150 mmol/l in patients with moderate-to-severe ARDS would be safe and will reduce lung injury. This was a prospective randomized feasibility study in moderate-to-severe ARDS, comparing standard care with intravenous hypertonic saline to achieve and maintain plasma sodium between 145 and 150 mmol/l for 7 days (HTS group). Both groups of patients were managed with lung protective ventilation and conservative fluid management. The primary outcome was 1-point reduction in lung injury score (LIS) or successful extubation by day 7. RESULTS: Forty patients were randomized with 20 in each group. Baseline characteristics of severity of illness were well balanced. Patients in the HTS group had higher plasma sodium levels during the first 7 days after randomization when compared with the control group (p = 0.04). Seventy five percent (15/20) of patients in the HTS group were extubated or had ≥ 1-point reduction in LIS compared with 35% (7/20) in the control group (p = 0.02). There was also a decrease in length of mechanical ventilation and hospital length of stay in the HTS group. CONCLUSION: We have shown clinical improvement in patients with moderate-to-severe ARDS following induced hypernatremia, suggesting that administration of hypertonic saline is a safe and feasible intervention in patients with moderate-to-severe ARDS. This suggests progress to a phase II study. Clinical Trial Registration Australian and New Zealand Clinical Trials Registry (ACTRN12615001282572).

Understanding Restrictive Versus Liberal Fluid Therapy for Major Abdominal Surgery Trial Results: Did Liberal Fluids Associate With Increased Endothelial Injury Markers?

Liberal fluid strategies in critically ill patients are associated with harm, thought to be due to endothelial and glycocalyx injury. As the restrictive versus liberal fluid therapy for major abdominal surgery trial not only failed to report survival benefit with restrictive fluids but was associated with a higher rate of acute kidney injury, we hypothesized that factors other than endothelial and glycocalyx injury were likely to account for these findings. Consequently, we measured injury biomarkers in a cohort of the restrictive versus liberal fluid therapy for major abdominal surgery trial. DESIGN: The restrictive versus liberal fluid therapy for major abdominal surgery trial was an international, randomized, assessor-blinded trial comparing restrictive with liberal IV fluid regimens that represented traditional care in patients undergoing major abdominal surgery. SETTING AND PATIENTS: Cohort of restrictive versus liberal fluid therapy for major abdominal surgery bloods was collected at a single major site (161 patients) prior to, day 1 and day 3 after surgery. INTERVENTION: Bloods were blindly and randomly batch analyzed for plasma markers of endothelial/glycocalyx injury-angiopoietin-1, angiopoietin-2, soluble tyrosine-protein kinase-2 receptor, soluble intracellular adhesion molecule-1, syndecan, and tumor necrosis factor-α. Data were examined as restrictive versus liberal enrollment groups and high versus low (± 5,000 mL) fluid groups. Differences were examined by linear mixed modeling. MEASUREMENT AND MAIN RESULTS: There were no significant differences in any biomarkers between the restrictive (n = 75) and liberal (n = 86) groups. When examined as low (n = 81) and high (n = 79) fluid groups, plasma angiopoietin-2 (p = 0.009) and soluble intracellular adhesion molecule-1 (p = 0.01) were elevated in the high fluid group. There were no differences in other biomarkers. CONCLUSIONS: Although these results are consistent with previous findings of vascular injury following liberal fluid therapy, they suggest alternative mechanisms underlie the clinical outcomes from restrictive versus liberal fluid therapy for major abdominal surgery study. CLINICALTRIALSGOV IDENTIFIER: NCT01424150.

Potential for bacteriophage therapy for Staphylococcus aureus pneumonia with influenza A coinfection.

The ability of influenza A virus to evolve, coupled with increasing antimicrobial resistance, could trigger an influenza pandemic with great morbidity and mortality. Much of the 1918 influenza pandemic mortality was likely due to bacterial coinfection, including Staphylococcus aureus pneumonia. S. aureus resists many antibiotics. The lack of new antibiotics suggests alternative antimicrobials, such as bacteriophages, are needed. Potential delivery routes for bacteriophage therapy (BT) include inhalation and intravenous injection. BT has recently been used successfully in compassionate access pulmonary infection cases. Phage lysins, enzymes that hydrolyze bacterial cell walls and which are bactericidal, are efficacious in animal pneumonia models. Clinical trials will be needed to determine whether BT can ameliorate disease in influenza and S. aureus coinfection.

Systemic Markers of Monocyte Activation in Acute Pulmonary Oedema.

BACKGROUND: Hydrostatic lung injury followed by pulmonary remodelling variably complicates cardiogenic acute pulmonary oedema (APO). Pulmonary remodelling may be regulated by the balance between distinct phenotypes of pulmonary macrophages; activated/inflammatory (M1), and reparative/anti-inflammatory (M2), derived from circulating monocyte populations. The aim of this study was to identify biomarkers in peripheral blood that are consistent with hydrostatic lung injury and pulmonary remodelling in APO and which follow the variable clinical course. METHODS: To examine peripheral markers of lung inflammation, resolution and remodelling, 18 patients, admitted to the intensive care unit (ICU) with a clinical diagnosis of APO, were enrolled. Admission, 12- and 24-hour post-admission bloods were assayed for cytokines by ELISA (R&D Systems, Minneapolis, MN, USA) and leukocyte surface markers by flow cytometry. RESULTS: Admission PaO2 to FiO2 ratio was positively correlated with Mon 2 (intermediate) monocyte prevalence, through increasing ratio of CD16+ monocytes to CD11b+ and CD40+ monocytes, and negatively correlated with Mon 1 (classical) monocyte prevalence, through decreasing ratio of CD16+ monocytes to CD62L+. Secondary cohort analysis compared 10 APO patients with established chronic heart failure (CHF) to eight without CHF. An increase in monocyte chemotactic peptide (MCP)-1, monocyte prevalence, and CD16-CD62L+ monocytes with CHF, all characteristic of monocyte activation to a Mon 1 phenotype, were found in the CHF APO patients. CONCLUSIONS: Increased systemic monocyte prevalence and expression of cell surface markers suggest a Mon 1 profile in CHF patients during episodes of APO. Future studies should define the role of systemic monocyte prevalence and activation in decompensated CHF.

Reduced Surfactant Contributes to Increased Lung Stiffness Induced by Rapid Inspiratory Flow.

INTRODUCTION: The mechanism of fast inspiratory flow rate (VI') induced lung injury is unclear. As fast VI' increases hysteresis, a measure of surface tension at the air-liquid interface, surfactant release or function may be important. This experimental study examines the contribution of impaired surfactant release or function to dynamic-VILI. METHODS: Isolated perfused lungs from male Sprague Dawley rats were randomly allocated to four groups: a long or short inspiratory time (Ti = 0.5 s; slow VI' or Ti = 0.1 s; fast VI') at PEEP of 2 or 10 cmH2O. Tidal volume was constant (7 ml/kg), with f = 60 breath/min. Forced impedance mechanics (tissue elastance (Htis), tissue resistance (Gtis) and airway resistance (Raw) were measured at 30, 60 and 90 min following which the lung was lavaged for surfactant phospholipids (PL) and disaturated PL (DSP). RESULTS: Fast VI' resulted in a stiffer lung. Concurrently, PL and DSP were decreased in both tubular myelin rich and poor fractions. Phospholipid decreases were similar with PEEP. In a subsequent cohort, laser confocal microscopy-based assessment demonstrated increased cellular injury with increased VI' at both 30 and 90 min ventilation. CONCLUSION: Rapid VI' may contribute to ventilator induced lung injury (VILI) through reduced surfactant release and/or more rapid reuptake despite unchanged tidal stretch.

Prevention and Amelioration of Rodent Ventilation-Induced Lung Injury with Either Prophylactic or Therapeutic feG Administration.

PURPOSE: Mechanical ventilation is a well-established therapy for patients with acute respiratory failure. However, up to 35% of mortality in acute respiratory distress syndrome may be attributed to ventilation-induced lung injury (VILI). We previously demonstrated the efficacy of the synthetic tripeptide feG for preventing and ameliorating acute pancreatitis-associated lung injury. However, as the mechanisms of induction of injury during mechanical ventilation may differ, we aimed to investigate the effect of feG in a rodent model of VILI, with or without secondary challenge, as a preventative treatment when administered before injury (prophylactic), or as a therapeutic treatment administered following initiation of injury (therapeutic). METHODS: Lung injury was assessed following prophylactic or therapeutic intratracheal feG administration in a rodent model of ventilation-induced lung injury, with or without secondary intratracheal lipopolysaccharide challenge. RESULTS: Prophylactic feG administration resulted in significant improvements in arterial blood oxygenation and respiratory mechanics, and decreased lung oedema, bronchoalveolar lavage protein concentration, histological tissue injury scores, blood vessel activation, bronchoalveolar lavage cell infiltration and lung myeloperoxidase activity in VILI, both with and without lipopolysaccharide. Therapeutic feG administration similarly ameliorated the severity of tissue damage and encouraged the resolution of injury. feG associated decreases in endothelial adhesion molecules may indicate a mechanism for these effects. CONCLUSIONS: This study supports the potential for feG as a pharmacological agent in the prevention or treatment of lung injury associated with mechanical ventilation.

Efficacy and safety of 20% albumin fluid loading in healthy subjects: a comparison of four resuscitation fluids.

Recently, buffered salt solutions and 20% albumin (small volume resuscitation) have been advocated as an alternative fluid for intravenous resuscitation. The relative comparative efficacy and potential adverse effects of these solutions have not been evaluated. In a randomized, double blind, cross-over study of six healthy male subjects we compared the pulmonary and hemodynamic effects of intravenous administration of 30 ml/kg of 0.9% saline, Hartmann's solution and 4% albumin, and 6 ml/kg of 20% albumin (albumin dose equivalent). Lung tests (spirometry, ultrasound, impulse oscillometry, diffusion capacity, and plethysmography), two- to three-dimensional Doppler echocardiography, carotid applanation tonometry, blood gases, serum/urine markers of endothelial, and kidney injury were measured before and after each fluid bolus. Data were analyzed with repeated measures ANOVA with effect of fluid type examined as an interaction. Crystalloids caused lung edema [increase in ultrasound B line (P = 0.006) and airway resistance (P = 0.009)], but evidence of lung injury [increased angiopoietin-2 (P = 0.019)] and glycocalyx injury [increased syndecan (P = 0.026)] was only observed with 0.9% saline. The colloids caused greater left atrial stretch, decrease in lung volumes, and increase in diffusion capacity than the crystalloids, but without pulmonary edema. Stroke work increased proportionally to increase in preload with all four fluids (R2 = 0.71). There was a greater increase in cardiac output and stroke volume after colloid administration, associated with a reduction in afterload. Hartmann's solution did not significantly alter ventricular performance. Markers of kidney injury were not affected by any of the fluids administrated. Bolus administration of 20% albumin is both effective and safe in healthy subjects. NEW & NOTEWORTHY Bolus administration of 20% albumin is both effective and safe in healthy subjects when compared with other commonly available crystalloids and colloidal solution.

Healthcare costs and outcomes for patients undergoing tracheostomy in an Australian tertiary level referral hospital.

OBJECTIVE: Patients undergoing tracheostomy represent a unique cohort, as often they have prolonged hospital stay, require multi-disciplinary, resource-intensive care, and may have poor outcomes. Currently, there is a lack of data around overall healthcare cost for these patients and their outcomes in terms of morbidity and mortality. The objective of the study was to estimate healthcare costs and outcomes associated in tracheostomy patients at a tertiary level hospital in South Australia. DESIGN: Retrospective review of prospectively collected data in patients who underwent tracheostomy between July 2009 and May 2015. METHODS: Overall healthcare-associated costs, length of mechanical ventilation, length of intensive care unit stay, and mortality rates were assessed. RESULTS: A total of 454 patients with tracheostomies were examined. Majority of the tracheostomies (n = 386 (85%)) were performed in intensive care unit patients, predominantly using bedside percutaneous approach (85%). The median length of hospital stay was 44 (29-63) days and the in-hospital mortality rate was 20%. Overall total cost of managing a patient with tracheostomy was median $192,184 (inter-quartile range $122560-$295553); mean 225,200 (range $5942-$1046675) Australian dollars. There were no statistically significant differences in any of the measured outcomes, including costs, between patients who underwent percutaneous versus surgical tracheostomy and patients who underwent early versus late tracheostomy in their intensive care unit stay. Factors that predicted (adjusted R 2 = 0.53) the cost per patient were intensive care unit length of stay and hospital length of stay. CONCLUSION: Hospitalised patients undergoing tracheostomy experience high morbidity and mortality and typically experience highly resource-intensive and costly healthcare.

Addressing the inadvertent sodium and chloride burden in critically ill patients: a prospective before-and-after study in a tertiary mixed intensive care unit population.

BACKGROUND: Inadvertent fluid loading - and resultant sodium and chloride - is common in critically ill patients. Sources such as fluid used as vehicles for drug infusions and boluses (fluid creep) and maintenance fluid are a common cause. We hypothesised that total sodium and chloride loading can be safely reduced in critically ill patients both by the use of 5% glucose as a diluent for infusions and boluses, when possible, and by its use as a maintenance fluid. METHODS: This was a prospective before-and-after study design in a single centre tertiary mixed intensive care unit (ICU). Comprehensive data about patient demographics, sources of fluid, feeds, intravenous drugs, fluid balance and electrolyte levels were collected for 4 weeks before and after the intervention (2016 and 2017). The amount of administered sodium was estimated from these sources. RESULTS: There were 146 patients (643 study days) and 133 patients (684 study days) examined in 2016 and 2017 respectively. The change of practice lead to an increase in the use of 5% glucose as the maintenance fluid and as a diluent, which resulted in a decrease in the total daily administered sodium from a median of 197 mmol (interquartile range [IQR], 155-328 mmol) to a median of 109 mmol (IQR, 77-288 mmol) (P = 0.0001). It also resulted in decrease in daily fluid balance, plasma chloride and ICU-acquired hypernatraemia. CONCLUSIONS: It is safely possible to decrease the total sodium and chloride loading to ICU patients by intervening on fluid creep and on maintenance fluid types. This intervention was accompanied by favourable changes in serum electrolyte and fluid balance.

Small volume resuscitation with 20% albumin in intensive care: physiological effects : The SWIPE randomised clinical trial.

PURPOSE: We set out to assess the resuscitation fluid requirements and physiological and clinical responses of intensive care unit (ICU) patients resuscitated with 20% albumin versus 4-5% albumin. METHODS: We performed a randomised controlled trial in 321 adult patients requiring fluid resuscitation within 48 h of admission to three ICUs in Australia and the UK. RESULTS: The cumulative volume of resuscitation fluid at 48 h (primary outcome) was lower in the 20% albumin group than in the 4-5% albumin group [median difference - 600 ml, 95% confidence interval (CI) - 800 to - 400; P < 0.001]. The 20% albumin group had lower cumulative fluid balance at 48 h (mean difference - 576 ml, 95% CI - 1033 to - 119; P = 0.01). Peak albumin levels were higher but sodium and chloride levels lower in the 20% albumin group. Median (interquartile range) duration of mechanical ventilation was 12.0 h (7.6, 33.1) in the 20% albumin group and 15.3 h (7.7, 58.1) in the 4-5% albumin group (P = 0.13); the proportion of patients commenced on renal replacement therapy after randomization was 3.3% and 4.2% (P = 0.67), respectively, and the proportion discharged alive from ICU was 97.4% and 91.1% (P = 0.02). CONCLUSIONS: Resuscitation with 20% albumin decreased resuscitation fluid requirements, minimized positive early fluid balance and was not associated with any evidence of harm compared with 4-5% albumin. These findings support the safety of further exploration of resuscitation with 20% albumin in larger randomised trials. TRIAL REGISTRATION: http://www.anzctr.org.au . Identifier ACTRN12615000349549.

Fluid resuscitation associated with elevated angiopoietin-2 and length of mechanical ventilation after cardiac surgery.

BACKGROUND: Fluid restriction in patients with acute respiratory distress syndrome increases ventilator-free days while lowering plasma angiopoietin-2 (Ang-2), a marker of pulmonary endothelial injury. We hypothesised that fluid resuscitation may lead to endothelial injury after cardiac surgery and analysed Ang-2, angiopoietin-1 (Ang-1) and phospholipase A2 (PLA2) levels and the impact of fluid management on ventilation time. METHODS: Patients enrolled in a single-centre, prospectively randomised interventional study of liberal or conservative fluid resuscitation strategy had plasma Ang-2, Ang-1 and PLA2 levels measured at baseline (pre-operative), 6 and 24 hours after commencement of cardiopulmonary bypass, and analysed by linear mixed models as liberal v conservative (intention to treat) or high v low fluid group (actual treatment, ≥ 3250 mL of fluid administered), and further subclassified as EuroSCORE (European System for Cardiac Operative Risk Evaluation) II ≥ 0.9 or < 0.9. RESULTS: Over 9 months, 144 patients were randomly allocated to either liberal (n =74) or conservative (n =70) fluid. Patients in the liberal fluid arm tended to an increased Ang-2 (P =0.12) and had higher PLA2 levels (P =0.03). Based on actual fluid administered, Ang-2 levels were higher, the Ang-1/Ang-2 ratio lower, and the length of mechanical ventilation and intensive care unit (ICU) stay was longer in the high fluid group (P < 0.001). The highest levels of Ang- 2 and corresponding lowest Ang-1/Ang-2 ratio, along with longest length of mechanical ventilation and ICU stay, were found with both the liberal and high fluid groups in patients with a EuroSCORE II ≥ 0.9 (P < 0.01). CONCLUSION: Liberal fluid resuscitation after cardiac surgery was associated with both pulmonary endothelial injury and prolonged length of mechanical ventilation. CLINICAL TRIAL REGISTRATION: ACTRN12612000754842.