Two Methods of Hemodynamic and Volume Status Assessment in Critically Ill Patients: A Study of Disagreement

Emergency department non-invasive cardiac output study (EDNICO): an accuracy study

BACKGROUND

There is little published data investigating non-invasive cardiac output monitoring in the emergency department (ED). We assess here the accuracy of five non-invasive methods in detecting fluid responsiveness in the ED: (1) common carotid artery blood flow, (2) suprasternal aortic Doppler, (3) bioreactance, (4) plethysmography with digital vascular unloading method, and (5) inferior vena cava collapsibility index. Left ventricular outflow tract echocardiography derived velocity time integral is the reference standard. This follows an assessment of feasibility and repeatability of these methods in the same cohort of ED patients.

METHODS

This is a prospective observational study of non-invasive methods for assessing fluid responsiveness in the ED. Participants were non-ventilated ED adult patients requiring intravenous fluid resuscitation. Sensitivity and specificity of each method in determining the fluid responsiveness status of participants is determined in comparison to the reference standard.

RESULTS

Thirty-three patient data sets were included for analysis. The specificity and sensitivity to detect fluid responders was 46.2 and 45% for common carotid artery blood flow (CCABF), 61.5 and 63.2% for suprasternal artery Doppler (SSAD), 46.2 and 50% for bioreactance, 50 and 41.2% for plethysmography vascular unloading technique (PVUT), and 63.6 and 47.4% for inferior vena cava collapsibility index (IVCCI), respectively. Analysis of agreement with Cohen's Kappa - 0.08 for CCABF, 0.24 for SSAD, - 0.04 for bioreactance, - 0.08 for PVUT, and 0.1 for IVCCI.

CONCLUSION

In this study, non-invasive methods were not found to reliably identify fluid responders. Non-invasive methods of identifying fluid responders are likely to play a key role in improving patient outcome in the ED in fluid depleted states such as sepsis. These results have implications for future studies assessing the accuracy of such methods.

Correlations between pulmonary artery pressures and inferior vena cava collapsibility in critically ill surgical patients: An exploratory study

INTRODUCTION

As pulmonary artery catheter (PAC) use declines, search continues for reliable and readily accessible minimally invasive hemodynamic monitoring alternatives. Although the correlation between inferior vena cava collapsibility index (IVC-CI) and central venous pressures (CVP) has been described previously, little information exists regarding the relationship between IVC-CI and pulmonary artery pressures (PAPs). The goal of this study is to bridge this important knowledge gap. We hypothesized that there would be an inverse correlation between IVC-CI and PAPs.

METHODS

A post hoc analysis of prospectively collected hemodynamic data was performed, examining correlations between IVC-CI and PAPs in a convenience sample of adult Surgical Intensive Care Unit patients. Concurrent measurements of IVC-CI and pulmonary arterial systolic (PAS), pulmonary arterial diastolic (PAD), and pulmonary arterial mean (PAM) pressures were performed. IVC-CI was calculated as ([IVCmax - IVCmin]/IVCmax) × 100%. Vena cava measurements were obtained by ultrasound-credentialed providers. For the purpose of correlative analysis, PAP measurements (PAS, PAD, and PAM) were grouped by terciles while the IVC-CI spectrum was divided into thirds (<33, 33-65, ≥66).

RESULTS

Data from 34 patients (12 women, 22 men, with median age of 59.5 years) were analyzed. Median Acute Physiologic Assessment and Chronic Health Evaluation II score was 9. A total of 76 measurement pairs were recorded, with 57% (43/76) obtained in mechanically ventilated patients. Correlations between IVC-CI and PAS (rs = -0.334), PAD (rs = -0.305), and PAM (rs = -0.329) were poor. Correlations were higher between CVP and PAS (R2 = 0.61), PAD (R2 = 0.68), and PAM (R2 = 0.70). High IVC-CI values (≥66%) consistently correlated with measurements in the lowest PAP ranges. Across all PAP groups (PAS, PAD, and PAM), there were no differences between the mean measurement values for the lower and middle IVC-CI ranges (0%-65%). However, all three groups had significantly lower mean measurement values for the ≥66% IVC-CI group.

CONCLUSIONS

Low PAS, PAD, and PAM measurements show a reasonable correlation with high IVC-CI (≥66%). These findings are consistent with previous descriptions of the relationship between IVC-CI and CVP. Additional research in this area is warranted to better describe the hemodynamic relationship between IVC-CI and PAPs, with the goal of further reduction in the reliance on the use of PACs.

Clinician-performed ultrasound in hemodynamic and cardiac assessment: a synopsis of current indications and limitations

Accurate hemodynamic and intravascular volume status assessment is essential in the diagnostic and therapeutic management of critically ill patients. Over the last two decades, a number of technological advances were translated into a variety of minimally invasive or non-invasive hemodynamic monitoring modalities. Despite the promise of less invasive technologies, the quality, reliability, reproducibility, and generalizability of resultant hemodynamic and intravascular volume status data have been lacking. Since its formal introduction, ultrasound technology has provided the medical community with a more standardized, higher quality, broadly applicable, and reproducible method of accomplishing the above-mentioned objectives. With the advent of portable, hand-carried devices, the importance of sonography in hemodynamic and volume status assessment became clear. From basic venous collapsibility and global cardiac assessment to more complex tasks such as the assessment of cardiac flow and tissue Doppler signals, the number of real-life indications for sonology continues to increase. This review will provide an outline of the essential ultrasound applications in hemodynamic and volume status assessment, focusing on evidence-based uses and indications.