Radial Artery Tonometry to Monitor Blood Pressure and Hemodynamics in Ambulatory Left Ventricular Assist Device Patients in Comparison With Doppler Ultrasound and Transthoracic Echocardiography: A Pilot Study

Validity and success rate of noninvasive mean arterial blood pressure measurements in cf-LVAD patients: A technical review

BACKGROUND

The life expectancy of patients with a continuous flow left ventricular assist device (cf-LVAD) is increasing. Adequate determination and regulation of mean arterial pressure (MAP) is important to prevent adverse events. Given the low pulsatility characteristics in these patients, standard blood pressure equipment is inadequate to monitor MAP and not recommended. We provide an overview of currently available noninvasive techniques, using an extensive search strategy in three online databases (Pubmed, Scopus and Google Scholar) to find validation studies using invasive intra-arterial blood pressure measurement as a reference. Mean differences with the reference values smaller than 5 ± 8 mm Hg were considered acceptable.

OBSERVATIONS

After deduplication, screening, and exclusion of incorrect sources, eleven studies remained with 3139 successful MAP measurements in 386 patients. Four noninvasive techniques, using Doppler, pulse oximetry, finger cuff volume clamp, or slow upper arm cuff deflation, were identified and evaluated for validity and success rate in cf-LVAD patients. Here, a comprehensive technical background of the blood pressure measurement methods is provided in combination with a clinical use comparison. Of the reported noninvasive techniques, slow cuff devices performed most optimally (mean difference 1.3 ± 5.2 mm Hg).

CONCLUSIONS

Our results are encouraging and indicate that noninvasive blood pressure monitoring options with acceptable validity and success rate are available. Further technical development and validation is warranted for the growing population of patients on long-term cf-LVAD support.

Contemporary Review of Hemodynamic Monitoring in the Critical Care Setting

Hemodynamic assessment remains the most valuable adjunct to physical examination and laboratory assessment in the diagnosis and management of shock. Through the years, multiple modalities to measure and trend hemodynamic indices have evolved with varying degrees of invasiveness. Pulmonary artery catheter (PAC) has long been considered the gold standard of hemodynamic assessment in critically ill patients and in recent years has been shown to improve clinical outcomes among patients in cardiogenic shock. The invasive nature of PAC is often cited as its major limitation and has encouraged development of less invasive technologies. In this review, the authors summarize the literature on the mechanism and validation of several minimally invasive and noninvasive modalities available in the contemporary intensive care unit. They also provide an update on the use of focused bedside echocardiography.

Noninvasive measurement of arterial blood pressure in patients with continuous-flow left ventricular assist devices: a systematic review

Accurate mean blood pressure determination is essential to prevent adverse events in patients with continuous-flow left ventricular assist devices (CFLVAD). We sought to evaluate the accuracy of noninvasive methods of blood pressure measurement compared with invasive intra-arterial recordings in patients with CFLVAD. Systematic electronic search was performed on four online databases (PubMed, Scopus, Embase, and Web of Knowledge) for the terms "Blood Pressure" AND ("Heart-Assist Devices" OR "Left ventricular Assist Devices"). Only studies that compared an intra-arterial and noninvasive blood pressure measurement were included. Electronic search of scientific literature identified 5968 articles. After deduplication, screening of titles and abstracts, full-text review, and excluding incorrect populations and comparator, a total of 12 studies with 502 participants were included, of those 402 participants who had intra-arterial blood pressure measurement. Doppler mean arterial blood pressure showed a very high correlation with mean intra-arterial blood pressure (r = 0.97, r = 0.87) in low pulsatility situations. When the pulsatility was not evaluated, the correlation was high moderate (r = 0.63, r = 0.741). In low pulsatility situations, the correlation was moderate to high moderate (r = 0.42 to r = 0.65). Oscillometer automatic blood pressure cuff showed a moderate to very high correlation with intra-arterial mean arterial blood pressure (r = 0.42, r = 0.86) but also could be low in the context of low pulsatility associated with inconsistent success in noninvasive measurement (r = 0.25). Studies correlating intra-arterial with noninvasive techniques were performed in the context of routine clinical care using fluid-filled catheters. The degree of correlation between both methods is at least moderate.

Accuracy of non-invasive and minimally invasive hemodynamic monitoring: where do we stand?

One of the most important variables in assessing hemodynamic status in the intensive care unit (ICU) is the cardiac function and blood pressure. Invasive methods such as pulmonary artery catheter and arterial line allow monitoring of blood pressure and cardiac function accurately and reliably. However, their use is not without drawbacks, especially when the invasive nature of these procedures and complications associated with them are considered. There are several newer methods of noninvasive and minimally invasive hemodynamic monitoring available. In this manuscript, we will review these different methods of minimally invasive and non-invasive hemodynamic monitoring and will discuss their advantages, drawbacks and limitations.