Indicator dilution measurements of extravascular lung water: basic assumptions and observations

Transpulmonary thermodilution detects rapid and reversible increases in lung water induced by positive end-expiratory pressure in acute respiratory distress syndrome

PURPOSE

It has been suggested that, by recruiting lung regions and enlarging the distribution volume of the cold indicator, increasing the positive end-expiratory pressure (PEEP) may lead to an artefactual overestimation of extravascular lung water (EVLW) by transpulmonary thermodilution (TPTD).

METHODS

In 60 ARDS patients, we measured EVLW (PiCCO2 device) at a PEEP level set to reach a plateau pressure of 30 cmH₂O (HighPEEP_start) and 15 and 45 min after decreasing PEEP to 5 cmH₂O (LowPEEP_15' and LowPEEP_45', respectively). Then, we increased PEEP back to the baseline level (HighPEEP_end). Between HighPEEP_start and LowPEEP_15', we estimated the degree of lung derecruitment either by measuring changes in the compliance of the respiratory system (Crs) in the whole population, or by measuring the lung derecruited volume in 30 patients. We defined patients with a large derecruitment from the other ones as patients in whom the Crs changes and the measured derecruited volume were larger than the median of these variables observed in the whole population.

RESULTS

Reducing PEEP from HighPEEP_start (14 ± 2 cmH₂O) to LowPEEP_15' significantly decreased EVLW from 20 ± 4 to 18 ± 4 mL/kg, central venous pressure (CVP) from 15 ± 4 to 12 ± 4 mmHg, the arterial oxygen tension over inspired oxygen fraction (PaO₂/FiO₂) ratio from 184 ± 76 to 150 ± 69 mmHg and lung volume by 144 [68-420] mL. The EVLW decrease was similar in "large derecruiters" and the other patients. When PEEP was re-increased to HighPEEP_end, CVP, PaO₂/FiO₂ and EVLW significantly re-increased. At linear mixed effect model, EVLW changes were significantly determined only by changes in PEEP and CVP (p < 0.001 and p = 0.03, respectively, n = 60). When the same analysis was performed by estimating recruitment according to lung volume changes (n = 30), CVP remained significantly associated to the changes in EVLW (p < 0.001).

CONCLUSIONS

In ARDS patients, changing the PEEP level induced parallel, small and reversible changes in EVLW. These changes were not due to an artefact of the TPTD technique and were likely due to the PEEP-induced changes in CVP, which is the backward pressure of the lung lymphatic drainage. Trial registration ID RCB: 2015-A01654-45. Registered 23 October 2015.

Aortic volume determines global end-diastolic volume measured by transpulmonary thermodilution

Background

Global end-diastolic volume (GEDV) measured by transpulmonary thermodilution is regarded as indicator of cardiac preload. A bolus of cold saline injected in a central vein travels through the heart and lung, but also the aorta until detection in a femoral artery. While it is well accepted that injection in the inferior vena cava results in higher values, the impact of the aortic volume on GEDV is unknown. In this study, we hypothesized that a larger aortic volume directly translates to a numerically higher GEDV measurement.

Methods

We retrospectively analyzed data from 88 critically ill patients with thermodilution monitoring and who did require a contrast-enhanced thoraco-abdominal computed tomography scan. Aortic volumes derived from imaging were compared with GEDV measurements in temporal proximity.

Results

Median aortic volume was 194 ml (interquartile range 147 to 249 ml). Per milliliter increase of the aortic volume, we found a GEDV increase by 3.0 ml (95% CI 2.0 to 4.1 ml, p < 0.001). In case a femoral central venous line was used for saline bolus injection, GEDV raised additionally by 2.1 ml (95% CI 0.5 to 3.7 ml, p = 0.01) per ml volume of the vena cava inferior. Aortic volume explained 59.3% of the variance of thermodilution-derived GEDV. When aortic volume was included in multivariate regression, GEDV variance was unaffected by sex, age, body height, and weight.

Conclusions

Our results suggest that the aortic volume is a substantial confounding variable for GEDV measurements performed with transpulmonary thermodilution. As the aorta is anatomically located after the heart, GEDV should not be considered to reflect cardiac preload. Guiding volume management by raw or indexed reference ranges of GEDV may be misleading.

Assessment of lung edema during ex-vivo lung perfusion by single transpulmonary thermodilution: A preliminary study in humans

BACKGROUND

Single transpulmonary thermodilution (SD) with extravascular lung water index (EVLWI) could become a new tool to better assess lung graft edema during ex-vivo lung perfusion (EVLP). In this study we compare EVLWI with conventional methods to better select lungs during EVLP and to predict post-transplant primary graft dysfunction (PGD).

METHODS

We measured EVLWI, arterial oxygen/fraction of inspired oxygen (P/F) ratio, and static lung compliance (SLC) during EVLP in an observational study. At the end of EVLP, grafts were accepted or rejected according to a standardized protocol blinded to EVLWI results. We compared the respective ability of EVLWI, P/F, and SLC to predict PGD. Mann-Whitney U-test, Fisher's exact test, and receiver-operating characteristic (ROC) curve data were used for analysis. p < 0.05 was considered statistically significant.

RESULTS

Thirty-five lungs were evaluated by SD during EVLP. Three lungs were rejected for pulmonary edema. Thirty-two patients were transplanted, 8 patients developed Grade 2 or 3 PGD, and 24 patients developed Grade 0 or 1 PGD. In contrast to P/F ratio, SLC, and pulmonary artery pressure, EVLWI differed between these 2 populations (p < 0.001). The area under the ROC for EVLWI assessing Grade 2 or 3 PGD at the end of EVLP was 0.93. Donor lungs with EVLWI >7.5 ml/kg were more likely associated with a higher incidence of Grade 2 or 3 PGD at Day 3.

CONCLUSIONS

Increased EVLWI during EVLP was associated with PGD in recipients.

Prognostic value of extravascular lung water assessed with lung ultrasound score by chest sonography in patients with acute respiratory distress syndrome

BACKGROUND

The prognostic value of extravascular lung water indices (EVLWI) has been widely investigated, which is determined by lung ultrasound B-lines. However, the clinical value of lung ultrasound B-lines for determining prognosis/intensive care unit (ICU) outcomes in patients with acute respiratory distress syndrome (ARDS) has been rarely reported.

METHODS

Twenty-one ARDS patients admitted to the ICU of Fu Xing Hospital underwent both lung ultrasonography and pulse index continuous cardiac output (PiCCO) monitoring on the first, second, and third days after diagnosis. The correlation between lung ultrasound score (LUS) and EVLWI measured by the PiCCO system was investigated. The prognostic clinical value of lung ultrasonography in ARDS patients was explored. Chest ultrasound was performed using the 12 regions method. The comprehensive score of lung ultrasound was determined according to the level of lung aeration.

RESULTS

With ICU mortality as the end point, 21 patients were divided into a survivor group (8 patients, 39.1 %) and a non-survivor group (13 patients, 61.9 %). Significant positive linear correlations were found between LUS and EVLWI, including predicted body weight (r (2) = 0.906), sequential organ failure assessment score (r (2) = 0.815), lung injury score (r (2) = 0.361), and PaO2/FiO2 (r (2) = 0.472). Significantly different LUSs were found between the non-survivor and survivor groups (F = 77.64, P <0.01) by repeated-measures analysis of variance. There were no significant differences between the two groups on different days. The areas under the receiver operating characteristic curves of LUS and EVLW measured by PiCCO were 0.846 (P < 0.01) and 0.918 (P < 0.01), respectively. The cut-off of LUS for prognosis prediction was 16.5.

CONCLUSIONS

Lung ultrasonography is a non-invasive, economic, simple, user-friendly, and radiation-free bedside method for predicting the prognosis of ARDS patients. Early measurement of LUS is a better prognostic indicator in patients with ARDS.

Improving diagnostic accuracy in assessing pulmonary edema on bedside chest radiographs using a standardized scoring approach

Background

To assess the value of a score-based system which allows standardized evaluation of pulmonary edema on bedside chest radiographs (CXRs) under routine clinical conditions.

Methods

Seven experienced readers assessed bedside CXRs of ten patients with an extravascular lung water (EVLW)-value of ≤ 8 mL/kg (range: 4–8 mL/kg; indicates no pulmonary edema) and a series of ten patients with an EVLW-value of ≥ 15 mL/kg (range: 15–21 mL/kg; = indicates a pulmonary edema) with and without customized software which would permit a standardized assessment of the various indications of pulmonary edema. The software provides a score that identifies patients with and without pulmonary edema. EVLW-values were measured instantly after bedside CXR imaging using a pulse contour cardiac output (PiCCO) system and served as a reference standard. The patients were non-traumatic and not treated with diuretics or dobutamine during bedside CXR imaging and the PiCCO measurements. Mean sensitivity, specificity, positive and negative predictive value, the percentage of overall agreement and the free-marginal multirater kappa value was calculated for both the standard and the standardized score-based approach. The net reclassification index was calculated for each reader as well as for all readers.

Results

Evaluation of bedside CXRs by means of the score-based approach took longer (23 ± 12 seconds versus 7 ± 3 seconds without the use of the software) but improved radiologists’ sensitivity (from 57 to 77%), specificity (from 90 to 100%) and the free-marginal multirater kappa value (from 0.34 to 0.68). The positive predictive value was raised from 85 to 100% and the negative predictive value from 68 to 81%. A net reclassification index of 0.3 (all readers) demonstrates an improvement in prediction performance gained by the score-based approach. The percentage of overall agreement was 67% with the standard approach and 84% with the software-based approach.

Conclusions

The diagnostic accuracy of bedside CXRs to discriminate patients with elevated EVLW-values from those with a normal value can be improved with the use of a standardized score-based approach. The investigated system is freely available as a web-based application (accessible via: http://www.radiologie.uk-erlangen.de/aerzte-und-zuweiser/edema).

Acute lung injury and pulmonary vascular permeability: use of transgenic models

Acute lung injury is a general term that describes injurious conditions that can range from mild interstitial edema to massive inflammatory tissue destruction. This review will cover theoretical considerations and quantitative and semi-quantitative methods for assessing edema formation and increased vascular permeability during lung injury. Pulmonary edema can be quantitated directly using gravimetric methods, or indirectly by descriptive microscopy, quantitative morphometric microscopy, altered lung mechanics, high-resolution computed tomography, magnetic resonance imaging, positron emission tomography, or x-ray films. Lung vascular permeability to fluid can be evaluated by measuring the filtration coefficient (Kf) and permeability to solutes evaluated from their blood to lung clearances. Albumin clearances can then be used to calculate specific permeability-surface area products (PS) and reflection coefficients (σ). These methods as applied to a wide variety of transgenic mice subjected to acute lung injury by hyperoxic exposure, sepsis, ischemia-reperfusion, acid aspiration, oleic acid infusion, repeated lung lavage, and bleomycin are reviewed. These commonly used animal models simulate features of the acute respiratory distress syndrome, and the preparation of genetically modified mice and their use for defining specific pathways in these disease models are outlined. Although the initiating events differ widely, many of the subsequent inflammatory processes causing lung injury and increased vascular permeability are surprisingly similar for many etiologies.

Clinical review: the role of ultrasound in estimating extra-vascular lung water

The estimation of extra-vascular lung water (EVLW) is an essential component in the assessment of critically ill patients. EVLW is independently associated with mortality and its manipulation has been shown to improve outcome. Accurate assessment of lung water is possible with CT and MR imaging but these are impractical for real-time measurement in sick patients and have been superseded by single thermal dilution techniques. While useful, single thermo-dilution requires repeated calibration and is prone to error, suggesting a need for other monitoring methods. Traditionally the lung was not thought amenable to ultrasound examination owing to the high acoustic impedance of air; however, the identification of artefacts in diseased lung has led to increased use of ultrasound as a point of care investigation for both diagnosis and to monitor response to interventions. Following the initial description of B-lines in association with increased lung water, accumulating evidence has shown that they are a useful and responsive measure of the presence and dynamic changes in EVLW. Animal models have confirmed a correlation with lung gravimetry and the utility of B-lines has been demonstrated in many clinical situations and correlated against other established measures of EVLW. With increasing availability and expertise the role of ultrasound in estimating EVLW should be embedded in clinical practice and incorporated into clinical algorithms to aid decision making. This review looks at the evidence for ultrasound as a valid, easy to use, non-invasive point of care investigation to assess EVLW.

The role for invasive monitoring in acute lung injury

Because acute lung injury (ALI) may arise from diverse and heterogeneous clinical insults, monitoring strategies for patients with ALI are heterogeneous as well. This review divides the monitoring strategies for ALI into three distinct phases. The "at-risk phase" is the period in which patients are at risk for ALI, and interventions may be applied to minimize or eliminate this risk. The "ALI phase" is the period during which ALI has occurred and requires attentive clinical management. The "resolution phase" is the period defined by resolution of ALI and successful discontinuation of mechanical ventilation. These phases are arbitrary, but they provide a useful framework for discussing the temporal changes in patient condition and monitoring goals in ALI.Invasive hemodynamic monitoring has specific roles in each phase of therapy for patients with ALI: pre-ALI, peri-ALI, and post-ALI. The primary goals are to optimize fluid resuscitation to prevent organ dysfunction, including ALI, and if ALI occurs to additional optimize fluid balance vis-à-vis the lung. By judicious application of invasive hemodynamic monitoring, particularly in its more modern iterations, clinicians can optimize the ebb and flow phases common to critically ill patients. This is vitally important given our current and growing understanding of the relationship between fluid balance and important clinical outcomes, multiple organ dysfunction syndrome, and mortality.

How to perform indexing of extravascular lung water: a validation study

BACKGROUND

Extravascular lung water is a quantitative marker of the amount of fluid in the thoracic cavity besides the vasculature. Indexing to both predicted and actual body weight have been proposed to compare different individuals and provide a uniform range of normal.

OBJECTIVE

We explored extravascular lung water measured by single-indicator transpulmonary thermodilution in a large cohort of patients without cardiopulmonary instability, in order to evaluate current and alternative indexing methods.

DESIGN

Prospective, observational.

SETTING

Neurosurgical ICU in a tertiary referral academic teaching hospital.

PATIENTS

One hundred and one consecutive patients requiring elective brain tumor surgery and postoperative ICU surveillance.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Indexed to predicted body weight, females had a mean extravascular lung water of 9.1 (SD=3.1, range: 5-23) mL/kg and males of 8.0 (SD=2.0, range: 4-19) mL/kg (p<0.001). Values indexed to predicted body weight were inversely correlated with the patient's height (p<0.001). Indexed to the traditionally used actual body weight, data showed a significant relationship to weight (p<0.001) and gender (p<0.05). In contrast, indexing to body height presented a method without dependencies on height, weight, or gender, yielding a uniform 95% confidence interval of 218-430 mL/m. Extravascular lung water increased with positive perioperative fluid balance (p=0.04).

CONCLUSIONS

Using either predicted or actual body weight for indexing extravascular lung water does not lead to independence of height, weight, and gender of the patient. Specifying a fixed range of normal or a uniform upper threshold for all patients is misleading for either method, despite widespread use. Our data suggest that indexing extravascular lung water to height is superior to weight-based methods. As we are not aware of any abnormal hemodynamic profile for brain tumor patients, we propose our findings to be a close approximation to normal values.

Pulmonary artery vs. transpulmonary thermodilution for the assessment of cardiac output in mitral regurgitation: a prospective observational study

CONTEXT

With increasing prevalence of mitral regurgitation, even noncardiac anaesthesiologists will be confronted by this disorder and will need to be familiar with the extended haemodynamic monitoring required. The assessment of cardiac output (CO) measured by transpulmonary thermodilution (COTP) has become an accepted alternative to the CO measured by thermodilution via pulmonary artery catheter (COPAC). However, the integrity of COTP in severe mitral regurgitation requires systematic evaluation.

OBJECTIVE

This study was designed to test the hypothesis that transpulmonary thermodilution is compromised by severe mitral regurgitation.

DESIGN

Prospective method comparison study.

SETTING

Single university-affiliated hospital.

PARTICIPANTS

Thirty patients with mitral regurgitation undergoing elective mitral valve repair.

MAIN OUTCOME MEASURE

COTP and COPAC were determined in triplicate after induction of anaesthesia, and at the end of surgery after closure of the chest. The methods were compared using bias and precision statistics.

RESULTS

Echocardiography revealed severe mitral regurgitation in most patients (n  =  27) after induction of anaesthesia. The least significant change in COTP (the minimum change in COTP required to detect a real change with a probability of 95%) was increased under the condition of mitral regurgitation (15.4  ±  10.2% after anaesthesia induction vs. 9.3  ±  5.9% after valve repair, P = 0.008), whereas it remained constant in COPAC (9.6  ±  5.4 vs. 8.5  ±  7.2%, P = 0.55). There was no significant bias between COTP and COPAC after anaesthesia induction [mean CO, 4.03 ± 0.92 l  min; bias 0.12 l  min (95% confidence interval, CI, -0.073 to 0.311)], and after valve repair [mean CO 7.47  ±  1.44 l  min; bias 0.045 l  min (95% CI, -0.147 to 0.237)]. The percentage error was 28.4 and 13.6%, respectively.

CONCLUSION

The results suggest that even severe mitral regurgitation has no significant impact on the accuracy of COTP. The precision of COTP was reduced under the condition of mitral regurgitation.

Extravascular lung water in acute respiratory distress syndrome: potential clinical value, assumptions and limitations

Extravascular lung water has been proposed as a marker of disease severity, response to treatment and mortality in patients with acute respiratory distress syndrome. Here, we discuss its potential value and limitations in clinical practice.

Comparison of chest radiograph scoring to lung weight as a quantitative index of pulmonary edema in organ donors

Quantification of the degree of pulmonary edema in organ donors is useful for assessing the clinical severity of pulmonary edema, determining response to therapy, and as an endpoint for therapeutic trials. Currently, there is no accurate non-invasive method for assessing the degree of pulmonary edema. We tested the performance of a four-quadrant chest radiographic scoring system compared to quantification of pulmonary edema by excised lung weight in 84 donors whose lungs were not used for transplantation. Chest radiographs were taken 3.6 ± 3.0 h prior to organ procurement and were scored by two of the authors. Lungs were excised without perfusion and individually weighed. The chest radiographic scoring system had good performance: correlation between total radiographic score and total lung weight of 0.61, p < 0.001. Performance of the scoring system was improved when chest radiographs with atelectasis were excluded (r = 0.79, p < 0.001). The area under the receiver operator characteristic curve for the detection of moderate pulmonary edema (total lung weight >1000 g) was 0.80. This chest radiographic scoring system may potentially be used to assess the clinical severity of pulmonary edema and may be useful as part of the evaluation of donors for suitability for lung transplantation.

Assessing the quantity of pulmonary edema in critically ill children

Measuring extravascular lung water may be useful for predicting outcome in adults with acute lung injury. The present commentary briefly reviews the potential role and limitations of extravascular lung water measurement in critically ill children.

Cell-based multiscale computational modeling of small molecule absorption and retention in the lungs

PURPOSE

For optimizing the local, pulmonary targeting of inhaled medications, it is important to analyze the relationship between the physicochemical properties of small molecules and their absorption, retention and distribution in the various cell types of the airways and alveoli.

METHODS

A computational, multiscale, cell-based model was constructed to facilitate analysis of pulmonary drug transport and distribution. The relationship between the physicochemical properties and pharmacokinetic profile of monobasic molecules was explored. Experimental absorption data of compounds with diverse structures were used to validate this model. Simulations were performed to evaluate the effect of active transport and organelle sequestration on the absorption kinetics of compounds.

RESULTS

Relating the physicochemical properties to the pharmacokinetic profiles of small molecules reveals how the absorption half-life and distribution of compounds are expected to vary in different cell types and anatomical regions of the lung. Based on logP, pK(a) and molecular radius, the absorption rate constants (K(a)) calculated with the model were consistent with experimental measurements of pulmonary drug absorption.

CONCLUSIONS

The cell-based mechanistic model developed herein is an important step towards the rational design of local, lung-targeted medications, facilitating the design and interpretation of experiments aimed at optimizing drug transport properties in lung.

Extravascular lung water indexed to predicted body weight is a novel predictor of intensive care unit mortality in patients with acute lung injury

OBJECTIVES

Acute lung injury and the acute respiratory distress syndrome are characterized by noncardiogenic pulmonary edema, which can be assessed by measurement of extravascular lung water. Traditionally, extravascular lung water has been indexed to actual body weight (mL/kg). Because lung size is dependent on height rather than weight, we hypothesized indexing to predicted body weight may be a better predictor of mortality in acute lung injury/acute respiratory distress syndrome.

DESIGN

Prospective observational cohort study.

SETTING

A tertiary referral intensive care unit.

PATIENTS

Patients were recruited within 48 hrs of fulfilling the American European Consensus Conference definition of acute lung injury/acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographics, severity of illness scores, and respiratory parameters were collected. Extravascular lung water was measured using the PiCCO system. This was indexed to actual and predicted body weight. Statistically significant predictors of mortality identified using single regressor logistic regression and additional variables known to be associated with outcome were entered into a multiple logistic regression analysis. Receiver operator characteristic curves were generated. Forty-four patients were recruited (septic 34%). Using single regressor logistic regression, six variables were statistically significantly related to mortality: Acute Physiology and Chronic Health Evaluation II, PaO2, PaO2/Fio2 ratio, oxygenation index, actual extravascular lung water, and predicted extravascular lung water. In multiple logistic regression analysis, predicted extravascular lung water but not actual extravascular lung water was a predictor of mortality with an odds ratio of 4.3 (95% confidence interval, 1.5-12.9) per sd. Although the area under the curve for predicted extravascular lung water (0.8; confidence interval, 0.65-0.94) was larger than for actual extravascular lung water (0.72; confidence interval, 0.53-0.91), this was not statistically significant (p = .12). A baseline predicted extravascular lung water value of 16 mL/kg predicted intensive care unit mortality with a sensitivity of 0.75 (confidence interval, 0.47-0.91) and specificity of 0.78 (confidence interval, 0.61-0.89).

CONCLUSIONS

Early measurement of predicted extravascular lung water is a better predictor than actual extravascular lung water to identify patients at risk for death in acute lung injury/acute respiratory distress syndrome.

Redistribution of pulmonary blood flow impacts thermodilution-based extravascular lung water measurements in a model of acute lung injury

BACKGROUND

Studies using transthoracic thermodilution have demonstrated increased extravascular lung water (EVLW) measurements attributed to progression of edema and flooding during sepsis and acute lung injury. The authors hypothesized that redistribution of pulmonary blood flow can cause increased apparent EVLW secondary to increased perfusion of thermally silent tissue, not increased lung edema.

METHODS

Anesthetized, mechanically ventilated canines were instrumented with PiCCO (Pulsion Medical, Munich, Germany) catheters and underwent lung injury by repetitive saline lavage. Hemodynamic and respiratory physiologic data were recorded. After stabilized lung injury, endotoxin was administered to inactivate hypoxic pulmonary vasoconstriction. Computed tomographic imaging was performed to quantify in vivo lung volume, total tissue (fluid) and air content, and regional distribution of blood flow.

RESULTS

Lavage injury caused an increase in airway pressures and decreased arterial oxygen content with minimal hemodynamic effects. EVLW and shunt fraction increased after injury and then markedly after endotoxin administration. Computed tomographic measurements quantified an endotoxin-induced increase in pulmonary blood flow to poorly aerated regions with no change in total lung tissue volume.

CONCLUSIONS

The abrupt increase in EVLW and shunt fraction after endotoxin administration is consistent with inactivation of hypoxic pulmonary vasoconstriction and increased perfusion to already flooded lung regions that were previously thermally silent. Computed tomographic studies further demonstrate in vivo alterations in regional blood flow (but not lung water) and account for these alterations in shunt fraction and EVLW.

Measurement of extravascular lung water using the single indicator method in patients: research and potential clinical value

Extravascular lung water includes all of the fluid within the lung but outside of the vasculature. Lung water increases as a result of increased hydrostatic vascular pressure or from an increase in lung endothelial and epithelial permeability or both. Experimentally, extravascular lung water has been measured gravimetrically. Clinically, the chest radiograph is used to determine whether extravascular lung water is present but is an insensitive instrument for determining the quantity of lung water. Bedside measurement of extravascular lung water in patients is now possible using a single indicator thermodilution method. This review critically evaluates the experimental and clinical evidence supporting the potential value of measuring extravascular lung water in patients using the single indicator method.

Effects of hydroxyethyl starch resuscitation on extravascular lung water and pulmonary permeability in sepsis-related acute respiratory distress syndrome

OBJECTIVE

Hydroxyethyl starch (HES) has greater volume expansion effect and longer intravascular persistence than crystalloids. HES also decreases microvascular permeability and capillary leakage by biophysically plugging endothelial leaks, exerting an anti-inflammatory effect, and decreasing activation of endothelial cells. The aim of our study was to determine whether medium molecular weight HES (pentastarch) resuscitation in the early stage of acute respiratory distress syndrome (ARDS) simultaneously increases cardiac output without worsening pulmonary edema and whether it attenuates pulmonary vascular permeability.

DESIGN

Prospective observational study.

SETTING

Twenty-bed medical intensive care unit of a tertiary medical center.

PATIENTS

Twenty patients with early-stage ARDS.

INTERVENTION

Volume expansion with a 500-mL infusion of 10% pentastarch (HES 200/0.5) at a rate of 10 mL/kg/hr.

MEASUREMENTS AND MAIN RESULTS

Baseline hemodynamics including systemic and pulmonary artery blood pressures, central venous pressure, pulmonary artery occlusion pressure, and cardiac output were obtained from an online HP Component Monitoring System and a pulmonary artery catheter. Intrathoracic blood volume (ITBV), global end-diastolic volume, extravascular lung water (EVLW), and pulmonary vascular permeability (EVLW/ITBV) were measured with a PiCCOplus monitor. Hemodynamic measurements were repeated immediately and 2, 4, and 6 hours after volume expansion. Pentastarch loading significantly increased central venous pressure, pulmonary artery occlusion pressure, pulmonary arterial pressures, and cardiac output. Pulmonary mechanics, venous admixtures, and EVLW values remained unchanged throughout the study. EVLW/ITBV significantly decreased immediately after the pentastarch infusion.

CONCLUSIONS

In patients with early ARDS, pentastarch resuscitation significantly improved their hemodynamics and cardiac output without worsening pulmonary edema and pulmonary mechanics. It even attenuated pulmonary vascular permeability.