Mortality Benefit From the Passive Leg Raise Maneuver in Guiding Resuscitation of Septic Shock Patients: A Systematic Review and Meta-Analysis of Randomized Trials

Background: Fluid therapy plays a major role in the management of critically ill patients. Yet assessment of intravascular volume in these patients is challenging. Different invasive and non-invasive methods have been used with variable results. The passive leg raise (PLR) maneuver has been recommended by international guidelines as a means to determine appropriate fluid resuscitation. We performed this systematic review and meta-analysis to determine if using this method of volume assessment has an impact on mortality outcome in patients with septic shock. Methods: This study is a systematic review and meta-analysis. We searched available data in the MEDLINE, CINAHL, EMBASE, and CENTRAL databases from inception until October 2020 for prospective, randomized, controlled trials that compared PLR-guided fluid resuscitation to standard care in adult patients with septic shock. Our primary outcome was mortality at the longest duration of follow-up. Results: We screened 1,425 article titles and abstracts. Of the 23 full-text articles reviewed, 5 studies with 462 patients met our eligibility criteria. Odds ratios (ORs) and associated 95% confidence intervals (CIs) for mortality at the longest reported time interval were calculated for each study. Using random effects modeling, the pooled OR (95% CI) for mortality with a PLR-guided resuscitation strategy was 0.82 (0.52 -1.30). The included studies were not blinded and they ranged from having low to high risk of bias using the Cochrane Risk of Bias Tool. Conclusion: Our analysis showed there was no statistically significant difference in mortality among septic shock patients treated with PLR-guided resuscitation vs. those with standard care.

Inferring the Frank–Starling Curve From Simultaneous Venous and Arterial Doppler: Measurements From a Wireless, Wearable Ultrasound Patch

The Frank–Starling relationship is a fundamental concept in cardiovascular physiology, relating change in cardiac filling to its output. Historically, this relationship has been measured by physiologists and clinicians using invasive monitoring tools, relating right atrial pressure (Pra) to stroke volume (SV) because the Pra-SV slope has therapeutic implications. For example, a critically ill patient with a flattened Pra-SV slope may have low Pra yet fail to increase SV following additional cardiac filling (e.g., intravenous fluids). Provocative maneuvers such as the passive leg raise (PLR) have been proposed to identify these “fluid non-responders”; however, simultaneously measuring cardiac filling and output via non-invasive methods like ultrasound is cumbersome during a PLR. In this Hypothesis and Theory submission, we suggest that a wearable Doppler ultrasound can infer the Pra-SV relationship by simultaneously capturing jugular venous and carotid arterial Doppler in real time. We propose that this method would confirm that low cardiac filling may associate with poor response to additional volume. Additionally, simultaneous assessment of venous filling and arterial output could help interpret and compare provocative maneuvers like the PLR because change in cardiac filling can be confirmed. If our hypothesis is confirmed with future investigation, wearable monitors capable of monitoring both variables of the Frank–Starling relation could be helpful in the ICU and other less acute patient settings.

Non-invasive assessment of fluid responsiveness to guide fluid therapy in patients with sepsis in the emergency department: a prospective cohort study

BackgroundLittle is known about optimal fluid therapy for patients with sepsis without shock who present to the ED. In this study, we aimed to quantify the effect of a fluid challenge on non-invasively measured Cardiac Index (CI) in patients presenting with sepsis without shock.MethodsIn a prospective cohort study, CI, stroke volume (SV) and systemic vascular resistance (SVR) were measured non-invasively in 30 patients presenting with sepsis without shock to the ED of a large teaching hospital in the Netherlands between May 2018 and March 2019 using the ClearSight system. After baseline measurements were performed, a passive leg raise (PLR) was done to simulate a fluid bolus. Measurements were then repeated 30, 60, 90 and 120 s after PLR. Finally, a standardised 500 mL NaCl 0.9% intravenous bolus was administered after which final measurements were done. Fluid responsiveness was defined as >15% increase in CI after a standardised fluid challenge.Measurements and main resultsSeven out of 30 (23%) patients demonstrated a >15% increase in CI after PLR and after a 500 mL fluid bolus. Fluid responders had a higher estimated glomerular filtration rate (eGFR) (64 (44–78) vs 37 (23–47), p=0.009) but otherwise similar patient and treatment characteristics as non-responders. Baseline measurements of cardiac output (CO), CI, SV and SVR were unrelated to PLR fluid responsiveness. The change in CI after PLR was strongly positive correlated to the change in CI after a 500 mL NaCl 0.9% fluid bolus (r=0.88, p<0.001).ConclusionThe results of the present study demonstrate that in patients with sepsis in the absence of shock, three out of four patients do not demonstrate a clinically relevant increase in CI after a standardised fluid challenge. Non-invasive CO monitoring in combination with a PLR test has the potential to identify patients who might benefit from fluid resuscitation and may contribute to a better tailored treatment of these patients.

A novel, hands-free ultrasound patch for continuous monitoring of quantitative Doppler in the carotid artery

Quantitative Doppler ultrasound of the carotid artery has been proposed as an instantaneous surrogate for monitoring rapid changes in left ventricular output. Tracking immediate changes in the arterial Doppler spectrogram has value in acute care settings such as the emergency department, operating room and critical care units. We report a novel, hands-free, continuous-wave Doppler ultrasound patch that adheres to the neck and tracks Doppler blood flow metrics in the common carotid artery using an automated algorithm. String and blood-mimicking test objects demonstrated that changes in velocity were accurately measured using both manually and automatically traced Doppler velocity waveforms. In a small usability study with 22 volunteer users (17 clinical, 5 lay), all users were able to locate the carotid Doppler signal on a volunteer subject, and, in a subsequent survey, agreed that the device was easy to use. To illustrate potential clinical applications of the device, the Doppler ultrasound patch was used on a healthy volunteer undergoing a passive leg raise (PLR) as well as on a congestive heart failure patient at resting baseline. The wearable carotid Doppler patch holds promise because of its ease-of-use, velocity measurement accuracy, and ability to continuously record Doppler spectrograms over many cardiac and respiratory cycles.