Quantitative Lung Ultrasonography for the Nephrologist: Applications in Dialysis and Heart Failure

Volume overload and its attendant increase in acute care utilization and cardiovascular morbidity and mortality represents a critical challenge for the practicing nephrologist. This is particularly true among patients with ESKD on HD where pre-dialysis volume overload and intradialytic and postdialytic hypovolemia account for almost a third of all cost for the Medicare dialysis benefit. Quantitative lung ultrasound is a tool for assessing the extent of extravascular lung water which outperforms physical exam and plain chest radiography. B-lines are vertical hyperechoic artifacts present in patients with increased extravascular lung water. B-lines have been shown to decrease dynamically during the hemodialysis treatment in proportion to ultrafiltration volume. Among patients with chronic heart failure, titration of diuretics based on the extent of pulmonary congestion noted on lung ultrasonography has been shown to decrease recurrent acute care utilization. Early data from randomized-controlled trials of lung ultrasound-guided ultrafiltration therapy among patients with ESKD on HD have shown promise for potential reduction in recurrent episodes of decompensated heart failure and cardiovascular events. Ultimately lung ultrasound may predict those who are ultrafiltration tolerant and could be used to decreased acute care utilization and thus cost in this population.

Ultrasonographic Assessment of Extravascular Lung Water in Hospitalized Patients Requiring Hemodialysis: A Prospective Observational Study

<b><i>Introduction:</i></b> Sonographic technologies can estimate extravascular lung water (EVLW) in hemodialysis (HD) patients. This study investigated the suitability of a handheld scanner in contrast to a portable scanner for quantifying EVLW in hospitalized patients requiring HD. <b><i>Methods:</i></b> In this prospective study, 54 hospitalized HD patients were enrolled. Bedside lung ultrasound was performed within 30 min before and after dialysis using handheld (phased array transducer, 1.7–3.8 MHz) and portable (curved probe, 5–2 MHz) ultrasound devices. Eight lung zones were scanned for total B-lines number (TBLN). The maximum diameter of inferior vena cava (IVC) was measured. We performed Passing-Bablok regression, Deming regression, Bland-Altman, and logistic regression analysis. <b><i>Results:</i></b> The 2 devices did not differ in measuring TBLN and IVC (<i>p</i> &#x3e; 0.05), showing a high correlation (<i>r</i> = 0.92 and <i>r</i> = 0.51, respectively). Passing-Bablok regression had a slope of 1.11 and an intercept of 0 for TBLN, and the slope of Deming regression was 1.02 within the CI bands of 0.94 and 1.11 in the full cohort. TBLN was logarithmically transformed for Bland-Altman analysis, showing a bias of 0.06 (TBLN = 1.2) between devices. The slope and intercept of the Deming regression in IVC measurements were 0.77 and 0.46, respectively; Bland-Altman plot showed a bias of −0.07. Compared with predialysis, TBLN significantly (<i>p</i> &#x3c; 0.001) decreased after dialysis, while IVC was unchanged (<i>p</i> = 0.16). Univariate analysis showed that cardiovascular disease (odds ratio [OR] 8.94 [2.13–61.96], <i>p</i> = 0.002), smoking history (OR 5.75 [1.8–20.46], <i>p</i> = 0.003), and right pleural effusion (OR 5.0 [1.2–25.99], <i>p</i> = 0.03) were strong predictors of EVLW indicated by TBLN ≥ 4. <b><i>Conclusion:</i></b> The lung and IVC findings obtained from handheld and portable ultrasound scanners are comparable and concordant. Cardiovascular disease and smoking history were strong predictors of EVLW. The use of TBLN to assess EVLW in hospitalized HD patients is feasible. Further studies are needed to determine if TBLN can help guide volume removal in HD patients.

COVID-19 ARDS is characterized by higher extravascular lung water than non-COVID-19 ARDS: the PiCCOVID study

Background In acute respiratory distress syndrome (ARDS), extravascular lung water index (EVLWi) and pulmonary vascular permeability index (PVPI) measured by transpulmonary thermodilution reflect the degree of lung injury. Whether EVLWi and PVPI are different between non-COVID-19 ARDS and the ARDS due to COVID-19 has never been reported. We aimed at comparing EVLWi, PVPI, respiratory mechanics and hemodynamics in patients with COVID-19 ARDS vs. ARDS of other origin. Methods Between March and October 2020, in an observational study conducted in intensive care units from three university hospitals, 60 patients with COVID-19-related ARDS monitored by transpulmonary thermodilution were compared to the 60 consecutive non-COVID-19 ARDS admitted immediately before the COVID-19 outbreak between December 2018 and February 2020. Results Driving pressure was similar between patients with COVID-19 and non-COVID-19 ARDS, at baseline as well as during the study period. Compared to patients without COVID-19, those with COVID-19 exhibited higher EVLWi, both at the baseline (17 (14–21) vs. 15 (11–19) mL/kg, respectively, p = 0.03) and at the time of its maximal value (24 (18–27) vs. 21 (15–24) mL/kg, respectively, p = 0.01). Similar results were observed for PVPI. In COVID-19 patients, the worst ratio between arterial oxygen partial pressure over oxygen inspired fraction was lower (81 (70–109) vs. 100 (80–124) mmHg, respectively, p = 0.02) and prone positioning and extracorporeal membrane oxygenation (ECMO) were more frequently used than in patients without COVID-19. COVID-19 patients had lower maximal lactate level and maximal norepinephrine dose than patients without COVID-19. Day-60 mortality was similar between groups (57% vs. 65%, respectively, p = 0.45). The maximal value of EVLWi and PVPI remained independently associated with outcome in the whole cohort. Conclusion Compared to ARDS patients without COVID-19, patients with COVID-19 had similar lung mechanics, but higher EVLWi and PVPI values from the beginning of the disease. This was associated with worse oxygenation and with more requirement of prone positioning and ECMO. This is compatible with the specific lung inflammation and severe diffuse alveolar damage related to COVID-19. By contrast, patients with COVID-19 had fewer hemodynamic derangement. Eventually, mortality was similar between groups. Trial registration number and date of registration ClinicalTrials.gov (NCT04337983). Registered 30 March 2020—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04337983.

Increased extravascular lung water index (EVLWI) reflects rapid non-cardiogenic oedema and mortality in COVID-19 associated ARDS

Nearly 5% of patients suffering from COVID-19 develop acute respiratory distress syndrome (ARDS). Extravascular lung water index (EVLWI) is a marker of pulmonary oedema which is associated with mortality in ARDS. In this study, we evaluate whether EVLWI is higher in patients with COVID-19 associated ARDS as compared to COVID-19 negative, ventilated patients with ARDS and whether EVLWI has the potential to monitor disease progression. EVLWI and cardiac function were monitored by transpulmonary thermodilution in 25 patients with COVID-19 ARDS subsequent to intubation and compared to a control group of 49 non-COVID-19 ARDS patients. At intubation, EVLWI was noticeably elevated and significantly higher in COVID-19 patients than in the control group (17 (11–38) vs. 11 (6–26) mL/kg; p < 0.001). High pulmonary vascular permeability index values (2.9 (1.0–5.2) versus 1.9 (1.0–5.2); p = 0.003) suggested a non-cardiogenic pulmonary oedema. By contrast, the cardiac parameters SVI, GEF and GEDVI were comparable in both cohorts. High EVLWI values were associated with viral persistence, prolonged intensive care treatment and in-hospital mortality (23.2 ± 6.7% vs. 30.3 ± 6.0%, p = 0.025). Also, EVLWI showed a significant between-subjects (r = − 0.60; p = 0.001) and within-subjects correlation (r = − 0.27; p = 0.028) to Horowitz index. Compared to non COVID-19 ARDS, COVID-19 results in markedly elevated EVLWI-values in patients with ARDS. High EVLWI reflects a non-cardiogenic pulmonary oedema in COVID-19 ARDS and could serve as parameter to monitor ARDS progression on ICU.

Hemodynamic Characteristics of Mechanically Ventilated COVID-19 Patients: A Cohort Analysis

Background. Solid data on cardiovascular derangements in critically ill COVID-19 patients remain scarce. The aim of this study is to describe hemodynamic characteristics in a cohort of COVID-19-related critically ill patients. Methods. A retrospective observational cohort study in twenty-eight consecutive mechanically ventilated COVID-19 patients. Pulse contour analysis-derived data were obtained from all patients, using the PiCCO® system. Results. The mean arterial pressure increased from 77 ± 10 mmHg on day 1 to 84 ± 9 mmHg on day 21 ( p = 0.04 ), in combination with the rapid tapering and cessation of norepinephrine and the gradual use of antihypertensive drugs in the vast majority of patients. The cardiac index increased significantly from 2.8 ± 0.7 L/min/m2 on day 1 to 4.0 ± 0.8 L/min/m2 on day 21 ( p < 0.001 ). Dobutamine was administered in only two patients. Mean markers of left ventricular contractility and peripheral perfusion, as well as lactate levels, remained within the normal range. Despite a constant fluid balance, extravascular lung water index decreased significantly from 17 ± 7 mL/kg on day 1 to 11 ± 4 mL/kg on day 21 ( p < 0.001 ). Simultaneously, intrapulmonary right-to-left shunt fraction (Qs/Qt) decreased significantly from 27 ± 10% in week 1 to 15 ± 9% in week 3 ( p = 0.007 ). PaO2/FiO2 ratio improved from 159 ± 53 mmHg to 319 ± 53 mmHg ( p < 0.001 ), but static lung compliance remained unchanged. Conclusions. In general, this cohort of patients with COVID-19 respiratory failure showed a marked rise in blood pressure over time, not accompanied by distinctive markers of circulatory failure. Characteristically, increased extravascular lung water, vascular permeability, and intrapulmonary shunt diminished over time, concomitant with an improvement in gas exchange.