PURPOSE: Volume status assessment is an important aspect of managing the critically ill patient. Echocardiography can noninvasively detect the change in inferior vena cava (IVC) diameter due to respiratory variation and can be used as a surrogate marker for central venous pressure (CVP). The pocket echocardiograph’s (PE) small size increases portability and potentially broadens use to novice echocardiographers. We hypothesize that a novice echocardiographer using PE can provide an accurate diagnostic tool for quantification of CVP in intubated patients.
METHODS: Unselected subjects scheduled for cardiac surgery underwent blinded PE (Acuson P10, Siemens) after induction of anesthesia, endotracheal intubation, Swan-Ganz catheter placement, and confirmation of a hemodynamic steady state. A cardiology fellow with two months of dedicated echocardiography training acquired all PE images. Subcostal images were acquired during maximal inspiration and expiration. CVP measurements were simultaneously obtained. The fellow and an experienced echocardiographer both interpreted PE studies offline in a blinded fashion and recorded maximal and minimal IVC dimensions. A CVP category was assigned using standard American Society of Echocardiography definitions. The experienced echocardiographer also performed image quality analysis.
RESULTS: Subjects (n=22) were 81% male; age 69±9 years. Overall subcostal image quality graded by the expert echocardiographer was unacceptable in 7 (31.8%) subjects and the novice echocardiographer could not interpret inferior vena cava diameter in 11 (50%) studies. Subsequent analysis was performed only on studies with complete data sets. Interobserver variability of echocardiographic CVP grade was high (kappa=0.39). Wilcoxon analysis revealed a trend towards significant difference between the novice echocardiographer’s CVP grade and direction CVP measurement (p=0.13), but was underpowered due to the inability to image subjects.
CONCLUSION: A novice echocardiographer using PE cannot acquire interpretable subcostal images in the majority of intubated patients, and when image quality is adequate, respiratory variation lacks precision for accurate CVP estimation.
CLINICAL IMPLICATIONS: While PE is a promising technology, thorough evaluation of clinical applications is needed prior to widespread use. PE should not be used currently for CVP estimation.
DISCLOSURE: Benjamin Culp, No Financial Disclosure Information; No Product/Research Disclosure Information