A modified subcostal view: a novel method for measuring the LVOT VTI

Passive leg raising test using the carotid flow velocity-time integral to predict fluid responsiveness

PURPOSE

The passive leg raising test (PLR) is a noninvasive method widely adopted to assess fluid responsiveness. We propose to explore if changes in the carotid flow assessed by echo-Doppler can predict fluid responsiveness after a PLR.

METHODS

We conducted a performance diagnostic study in two intensive care units from Argentina between February and April 2022. We included patients with signs of tissular hypoperfusion that required fluid resuscitation. We labeled the patients as fluid responders when we measured, after a fluid bolus, an increase greater than 15% in the left ventricle outflow tract (LVOT) VTI in an apical 5-chamber view and we compared those results with the carotid flow (CF) velocity-time integral (VTI) from the left supraclavicular region in a semi-recumbent position and during the PLR.

RESULTS

Of the 62 eligible patients, 50 patients (80.6%) were included. The area under the ROC curve for a change in CF VTI during the PLR test was 0.869 (95% CI 0.743-0.947). An increase of at least of 11% in the CF VTI with the PLR predicted fluid-responsiveness with a sensitivity of 77.3% (95% CI 54.6-92.2%) and specificity of 78.6% (95% CI 59-91.7%). The positive predictive value was 73.9% (95% CI 57.4-85.6%) and the negative predictive value was 81.5% (95% CI 66.5-90.7%). The positive likelihood ratio was 3.61 and the negative likelihood ratio was 0.29.

CONCLUSION

An increase greater than 11% in CF VTI after a PLR may be useful to predict fluid responsiveness among critically ill patients.

Alternative Cardiac Point-of-Care Ultrasound Views

Point of care ultrasound (POCUS) and critical care echocardiography (CCE) is increasingly being used in intensive care units (ICUs). POCUS and CCE may be limited in some ICU patients because of inadequate information from standard echocardiographic windows. At the same time, data from POCUS and CCE in ICU may be critical to managing patients with cardiorespiratory failure. Alternative echocardiographic views done at the bedside by ICU practitioners may yield additional information or replace the missing data from the standard views. Information obtained from multiple echocardiographic views should be integrated and interpreted within the patient's other clinical information.

Passive leg raising test to predict fluid responsiveness using the right ventricle outflow tract velocity-time integral through a subcostal view

PURPOSE

The passive leg raising test (PLR) produces a reversible increase in venous return and, if the patient's ventricles are preload dependent, in the cardiac output. As this effect occurs in seconds, the transthoracic echocardiography is optimal for its real time assessment. The utility of the PLR for monitoring fluid responsiveness through the measurement of the left ventricle outflow tract velocity-time integral (LVOT VTI) in an apical 5-chamber view is well stablished. To achieve this view in critically ill patients is often challenging. The aim of this study is to explore the accuracy for predicting fluid responsiveness of the change in the right ventricle outflow tract velocity-time integral (RVOT VTI) from a subcostal view during a PLR.

METHODS

This is a diagnostic accuracy study carried out in two centers in Argentina. We included patients admitted to the intensive care unit from January 2022 to April 2022, that required fluid expansion due to signs of tissular hypoperfusion. We measured the RVOT VTI from a subcostal view in a semi-recumbent position and during the PLR, and the LVOT VTI in an apical 5-chamber view before and after a fluid bolus. If the LVOT VTI increased by 15% after the fluid bolus, the patients were considered fluid responders.

RESULTS

We included 43 patients. The area under the ROC curve for a change in the RVOT VTI during the PLR was 0.879 (95% CI 0.744-0.959). A change of 15.36% in the RVOT VTI with the PLR predicted fluid responsiveness with a sensitivity of 85.7% (95% CI 57.2%-98.2%) and specificity of 93.1% (95% CI 77.2-99.2). The positive predictive value was 85.7% (95% CI 60.8%-95.9%) and the negative predictive value was 93.1% (95% CI 78.8%-98%). The positive likelihood ratio was 12.43 and the negative predictive value was 0.15.

CONCLUSION

The RVOT VTI change during a PLR is suitable for the prediction of fluid responsiveness in critically ill patients.