Clinical review: Update on hemodynamic monitoring--a consensus of 16

A recommendation for the use of electrical biosensing technology in neonatology

Non-invasive cardiac output monitoring, via electrical biosensing technology (EBT), provides continuous, multi-parameter hemodynamic variable monitoring which may allow for timely identification of hemodynamic instability in some neonates, providing an opportunity for early intervention that may improve neonatal outcomes. EBT encompasses thoracic (TEBT) and whole body (WBEBT) methods. Despite the lack of relative accuracy of these technologies, as compared to transthoracic echocardiography, the use of these technologies in neonatology, both in the research and clinical arena, have increased dramatically over the last 30 years. The European Society of Pediatric Research Special Interest Group in Non-Invasive Cardiac Output Monitoring, a group of experienced neonatologists in the field of EBT, deemed it appropriate to provide recommendations for the use of TEBT and WBEBT in the field of neonatology. Although TEBT is not an accurate determinant of cardiac output or stroke volume, it may be useful for monitoring longitudinal changes of hemodynamic parameters. Few recommendations can be made for the use of TEBT in common neonatal clinical conditions. It is recommended not to use WBEBT to monitor cardiac output. The differences in technologies, study methodologies and data reporting should be addressed in ongoing research prior to introducing EBT into routine practice. IMPACT STATEMENT: TEBT is not recommended as an accurate determinant of cardiac output (CO) (or stroke volume (SV)). TEBT may be useful for monitoring longitudinal changes from baseline of hemodynamic parameters on an individual patient basis. TEBT-derived thoracic fluid content (TFC) longitudinal changes from baseline may be useful in monitoring progress in respiratory disorders and circulatory conditions affecting intrathoracic fluid volume. Currently there is insufficient evidence to make any recommendations regarding the use of WBEBT for CO monitoring in neonates. Further research is required in all areas prior to the implementation of these monitors into routine clinical practice.

MAN VERSUS MACHINE: PROVIDER DIRECTED VERSUS PRECISION AUTOMATED CRITICAL CARE MANAGEMENT IN A PORCINE MODEL OF DISTRIBUTIVE SHOCK

ABSTRACT

Background: Critical care management of shock is a labor-intensive process. Precision Automated Critical Care Management (PACC-MAN) is an automated closed-loop system incorporating physiologic and hemodynamic inputs to deliver interventions while avoiding excessive fluid or vasopressor administration. To understand PACC-MAN efficacy, we compared PACC-MAN to provider-directed management (PDM). We hypothesized that PACC-MAN would achieve equivalent resuscitation outcomes to PDM while maintaining normotension with lower fluid and vasopressor requirements. Methods : Twelve swine underwent 30% controlled hemorrhage over 30 min, followed by 45 min of aortic occlusion to generate a vasoplegic shock state, transfusion to euvolemia, and randomization to PACC-MAN or PDM for 4.25 h. Primary outcomes were total crystalloid volume, vasopressor administration, total time spent at hypotension (mean arterial blood pressure <60 mm Hg), and total number of interventions. Results : Weight-based fluid volumes were similar between PACC-MAN and PDM; median and IQR are reported (73.1 mL/kg [59.0-78.7] vs. 87.1 mL/kg [79.4-91.8], P = 0.07). There was no statistical difference in cumulative norepinephrine (PACC-MAN: 33.4 μg/kg [27.1-44.6] vs. PDM: 7.5 [3.3-24.2] μg/kg, P = 0.09). The median percentage of time spent at hypotension was equivalent (PACC-MAN: 6.2% [3.6-7.4] and PDM: 3.1% [1.3-6.6], P = 0.23). Urine outputs were similar between PACC-MAN and PDM (14.0 mL/kg vs. 21.5 mL/kg, P = 0.13). Conclusion : Automated resuscitation achieves equivalent resuscitation outcomes to direct human intervention in this shock model. This study provides the first translational experience with the PACC-MAN system versus PDM.

Improving sub-pixel accuracy in ultrasound localization microscopy using supervised and self-supervised deep learning

With a spatial resolution of tens of microns, ultrasound localization microscopy (ULM) reconstructs microvascular structures and measures intravascular flows by tracking microbubbles (1-5 μm) in contrast enhanced ultrasound (CEUS) images. Since the size of CEUS bubble traces, e.g. 0.5-1 mm for ultrasound with a wavelength λ = 280 μm, is typically two orders of magnitude larger than the bubble diameter, accurately localizing microbubbles in noisy CEUS data is vital to the fidelity of the ULM results. In this paper, we introduce a residual learning based supervised super-resolution blind deconvolution network (SupBD-net), and a new loss function for a self-supervised blind deconvolution network (SelfBD-net), for detecting bubble centers at a spatial resolution finer than λ/10. Our ultimate purpose is to improve the ability to distinguish closely located microvessels and the accuracy of the velocity profile measurements in macrovessels. Using realistic synthetic data, the performance of these methods is calibrated and compared against several recently introduced deep learning and blind deconvolution techniques. For bubble detection, errors in bubble center location increase with the trace size, noise level, and bubble concentration. For all cases, SupBD-net yields the least error, keeping it below 0.1 λ. For unknown bubble trace morphology, where all the supervised learning methods fail, SelfBD-net can still maintain an error of less than 0.15 λ. SupBD-net also outperforms the other methods in separating closely located bubbles and parallel microvessels. In macrovessels, SupBD-net maintains the least errors in the vessel radius and velocity profile after introducing a procedure that corrects for terminated tracks caused by overlapping traces. Application of these methods is demonstrated by mapping the cerebral microvasculature of a neonatal pig, where neighboring microvessels separated by 0.15 λ can be readily distinguished by SupBD-net and SelfBD-net, but not by the other techniques. Hence, the newly proposed residual learning based methods improve the spatial resolution and accuracy of ULM in micro- and macro-vessels.

Wireless Battery-free and Fully Implantable Organ Interfaces

Advances in soft materials, miniaturized electronics, sensors, stimulators, radios, and battery-free power supplies are resulting in a new generation of fully implantable organ interfaces that leverage volumetric reduction and soft mechanics by eliminating electrochemical power storage. This device class offers the ability to provide high-fidelity readouts of physiological processes, enables stimulation, and allows control over organs to realize new therapeutic and diagnostic paradigms. Driven by seamless integration with connected infrastructure, these devices enable personalized digital medicine. Key to advances are carefully designed material, electrophysical, electrochemical, and electromagnetic systems that form implantables with mechanical properties closely matched to the target organ to deliver functionality that supports high-fidelity sensors and stimulators. The elimination of electrochemical power supplies enables control over device operation, anywhere from acute, to lifetimes matching the target subject with physical dimensions that supports imperceptible operation. This review provides a comprehensive overview of the basic building blocks of battery-free organ interfaces and related topics such as implantation, delivery, sterilization, and user acceptance. State of the art examples categorized by organ system and an outlook of interconnection and advanced strategies for computation leveraging the consistent power influx to elevate functionality of this device class over current battery-powered strategies is highlighted.

Intraoperative haemodynamic monitoring and management of adults having non-cardiac surgery: Guidelines of the German Society of Anaesthesiology and Intensive Care Medicine in collaboration with the German Association of the Scientific Medical Societies

Haemodynamic monitoring and management are cornerstones of perioperative care. The goal of haemodynamic management is to maintain organ function by ensuring adequate perfusion pressure, blood flow, and oxygen delivery. We here present guidelines on "Intraoperative haemodynamic monitoring and management of adults having non-cardiac surgery" that were prepared by 18 experts on behalf of the German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und lntensivmedizin; DGAI).

Challenges in Septic Shock: From New Hemodynamics to Blood Purification Therapies

Sepsis and septic shock are associated with high mortality, with diagnosis and treatment remaining a challenge for clinicians. Their management classically encompasses hemodynamic resuscitation, antibiotic treatment, life support, and focus control; however, there are aspects that have changed. This narrative review highlights current and avant-garde methods of handling patients experiencing septic shock based on the experience of its authors and the best available evidence in a context of uncertainty. Following the first recommendation of the Surviving Sepsis Campaign guidelines, it is recommended that specific sepsis care performance improvement programs are implemented in hospitals, i.e., "Sepsis Code" programs, designed ad hoc, to achieve this goal. Regarding hemodynamics, the importance of perfusion and hemodynamic coherence stand out, which allow for the recognition of different phenotypes, determination of the ideal time for commencing vasopressor treatment, and the appropriate fluid therapy dosage. At present, this is not only important for the initial timing, but also for de-resuscitation, which involves the early weaning of support therapies, directed elimination of fluids, and fluid tolerance concept. Finally, regarding blood purification therapies, those aimed at eliminating endotoxins and cytokines are attractive in the early management of patients in septic shock.

Novel Pulse Waveform Index by Ambulatory Blood Pressure Monitoring and Cardiac Function: A Pilot Study

Background

A simple ambulatory measure of cardiac function could be helpful for monitoring heart failure patients.

Objectives

The purpose of this paper was to determine whether a novel pulse waveform analysis using data obtained by our developed multisensor-ambulatory blood pressure monitoring (ABPM) device, the 'Sf/Am' ratio, is associated with echocardiographic left ventricular ejection fraction (LVEF).

Methods

Multisensor-ABPM was conducted twice at baseline in 20 heart failure (HF) patients with HF-reduced LVEF or HF-preserved LVEF (median age 66 years, male 65%) and over a 6- to 12-month follow-up after patient-tailored treatment. We assessed the changes in the pulse waveform index Sf/Am and LVEF that occurred between the baseline and follow-up. The Sf/Am consists of the area of the ejection part in the square forward wave (Sf) and the amplitude of the measured wave (Am). We divided the patients into the recovered (n = 11) and not-recovered (n = 9) groups defined by a ≥10% increase in LVEF.

Results

Although the ambulatory BP levels and variabilities did not change in either group, the Sf/Am increased significantly in the recovered group (baseline 21.4 ± 4.5; follow-up, 25.6 ± 3.7, P = 0.004). The not-recovered group showed no difference between the baseline and follow-up. The follow-up/baseline Sf/Am ratio was significantly associated with the LVEF ratio (r = 0.469, P = 0.037). The Sf/Am was significantly correlated with the LVEF in overall measurements (n = 40, r = 0.491, P = 0.001).

Conclusions

These results demonstrated that a novel noninvasive pulse waveform index, the Sf/Am measured by multisensor-ABPM is associated with LVEF. The Sf/Am may be useful for estimating cardiac function.

The Evolution and Future of Intensive Care Management in the Era of Telecritical Care and Artificial Intelligence

Critical care practice has been embodied in the healthcare system since the institutionalization of intensive care units (ICUs) in the late '50s. Over time, this sector has experienced many changes and improvements in providing immediate and dedicated healthcare as patients requiring intensive care are often frail and critically ill with high mortality and morbidity rates. These changes were aided by innovations in diagnostic, therapeutic, and monitoring technologies, as well as the implementation of evidence-based guidelines and organizational structures within the ICU. In this review, we examine these changes in intensive care management over the past 40 years and their impact on the quality of care available to patients. Moreover, the current state of intensive care management is characterized by a multidisciplinary approach and the use of innovative technologies and research databases. Advancements such as telecritical care and artificial intelligence are being increasingly explored, especially since the COVID-19 pandemic, to reduce the length of hospitalization and ICU mortality. With these advancements in intensive care and ever-changing patient needs, critical care experts, hospital managers, and policymakers must also explore appropriate organizational structures and future enhancements within the ICU.

A critical review of the perioperative fluid therapy and hemodynamic monitoring recommendations of the Enhanced Recovery of the Adult Pathway (RICA): A position statement of the fluid therapy and hemodynamic monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR)

In an effort to standardize perioperative management and improve postoperative outcomes of adult patients undergoing surgery, the Ministry of Health, through the Spanish Multimodal Rehabilitation Group (GERM), and the Aragonese Institute of Health Sciences, in collaboration with multiple Spanish scientific societies and based on the available evidence, published in 2021 the Spanish Intensified Adult Recovery (RICA) guideline. This document includes 12 perioperative measures related to fluid therapy and hemodynamic monitoring. Fluid administration and hemodynamic monitoring are not straightforward but are directly related to postoperative patient outcomes. The Fluid Therapy and Hemodynamic Monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR) has reviewed these recommendations and concluded that they should be revised as they do not follow an adequate methodology.

Precision Automated Critical Care Management: Closed-loop critical care for the treatment of distributive shock in a swine model of ischemia-reperfusion

BACKGROUND

Goal-directed blood pressure management in the intensive care unit can improve trauma outcomes but is labor-intensive. Automated critical care systems can deliver scaled interventions to avoid excessive fluid or vasopressor administration. We compared a first-generation automated drug and fluid delivery platform, Precision Automated Critical Care Management (PACC-MAN), to a more refined algorithm, incorporating additional physiologic inputs and therapeutics. We hypothesized that the enhanced algorithm would achieve equivalent resuscitation endpoints with less crystalloid utilization in the setting of distributive shock.

METHODS

Twelve swine underwent 30% hemorrhage and 30 minutes of aortic occlusion to induce an ischemia-reperfusion injury and distributive shock state. Next, animals were transfused to euvolemia and randomized into a standardized critical care (SCC) of PACC-MAN or an enhanced version (SCC+) for 4.25 hours. SCC+ incorporated lactate and urine output to assess global response to resuscitation and added vasopressin as an adjunct to norepinephrine at certain thresholds. Primary and secondary outcomes were decreased crystalloid administration and time at goal blood pressure, respectively.

RESULTS

Weight-based fluid bolus volume was lower in SCC+ compared with SCC (26.9 mL/kg vs. 67.5 mL/kg, p = 0.02). Cumulative norepinephrine dose required was not significantly different (SCC+: 26.9 μg/kg vs. SCC: 13.76 μg/kg, p = 0.24). Three of 6 animals (50%) in SCC+ triggered vasopressin as an adjunct. Percent time spent between 60 mm Hg and 70 mm Hg, terminal creatinine and lactate, and weight-adjusted cumulative urine output were equivalent.

CONCLUSION

Refinement of the PACC-MAN algorithm decreased crystalloid administration without sacrificing time in normotension, reducing urine output, increasing vasopressor support, or elevating biomarkers of organ damage. Iterative improvements in automated critical care systems to achieve target hemodynamics in a distributive-shock model are feasible.

Sepsis-induced cardiomyopathy in animals: From experimental studies to echocardiography-based clinical research

The term "sepsis-induced cardiomyopathy" (SIC) is used to describe transient cardiac dysfunction in septic patients. However, there is no universally accepted definition of SIC; a reduction in left ventricular ejection fraction (LVEF) is often used. In addition to systolic dysfunction, diastolic dysfunction is now recognized as an essential component of SIC. It can be emphasized that previous animal experiments played an essential role in revealing SIC and hemodynamic instability in sepsis and septic shock. The diagnostic and prognostic capabilities of echocardiography for the assessment of SIC have been extensively studied since its introduction into intensive care clinical practice. Recent studies in dogs, calves, and horses have shown that left and right ventricular systolic dysfunction, left ventricular diastolic dysfunction, and circulatory dysfunction can occur in sepsis, severe sepsis, and septic shock in animals. Echocardiographic variables have also shown that indices of left and right ventricular dysfunction and circulatory failure are valuable indicators of mortality in septic animals.

Stroke Volume Measurements by Echocardiography and Ultrasonic Cardiac Output Monitor in Children: A Prospective Observational Cohort Study

OBJECTIVES

Stroke volume (SV) and cardiac output monitoring is a cornerstone of hemodynamic assessment. Noninvasive technologies are increasingly used in children. This study compared SV measurements obtained by transcutaneous Doppler ultrasound techniques (ultrasonic cardiac output monitor [USCOM]), transthoracic echocardiography jugular (TTE-J), and parasternal (TTE-P) views performed by pediatric intensivists (OP-As) with limited training in cardiac sonography (20 previous examinations) and pediatric cardiologists (OP-Bs) with limited training in USCOM (30 previous examinations) in spontaneously ventilating children.

METHODS

A single-center study was conducted in 37 children. Each operator obtained 3 sets of USCOM SV measurements within a period of 3 to 5 minutes, followed with TTE measurements from both apical and jugular views. The investigators were blinded to each other's results to prevent visual and auditory bias.

RESULTS

Both USCOM and TTE methods were applicable in 89% of patients. The intraobserver variability of USCOM, TTE-J, and TTE-P were less than 10% in both investigators. The SV measurements by OP-As using USCOM, TTE-J, and TTE-P were 46.15 (25.48) mL, 39.45 (20.65) mL, and 33.42 (16.69) mL, respectively. The SV measurements by OP-Bs using USCOM, TTE-J, and TTE-P were 43.99 (25.24) mL, 38.91 (19.98) mL, and 37.58 (19.81) mL, respectively.The percentage error in SV with USCOM relative to TTE-J was 36% in OP-As and 37% in OP-Bs. The percentage error in SV with TTE-P was 33% relative to TTE-J in OP-As and 21% in OP-Bs.

CONCLUSIONS

Our findings show that the methods are not interchangeable because SV values by USCOM are higher in comparison with the SV values obtained by TTE. Both methods have low level of intraobserver variability. The SV measurements obtained by TTE-P were significantly lower compared with the TTE-J for the operator with limited training in echocardiography. The TTE-P requires longer practice compared with the TTE-J; therefore, we recommend to prefer TTE-J to TTE-P for inexperienced operators.

An Implantable Wireless System for Remote Hemodynamic Monitoring of Heart Failure Patients

This article presents an implantable wireless system for remote hemodynamic monitoring, which enables direct, continuous (24/7), and simultaneous measurement of pulmonary arterial pressure (PAP) and cross-sectional area (CSA) of the artery. The implantable device, which measures 3.2 mm × 2 mm × 10 mm, comprises a piezoresistive pressure sensor, an ASIC implemented in 180-nm CMOS, a piezoelectric ultrasound (US) transducer, and a nitinol anchoring loop. An energy-efficient pressure monitoring system, which employs duty-cycling and spinning excitation technique, achieves 0.44 mmHg resolution in a pressure range from -135 mmHg to +135 mmHg and consumes 1.1 nJ conversion energy. The artery diameter monitoring system utilizes the inductive characteristic of the implant's anchoring loop and achieves 0.24 mm resolution within a diameter range of 20 mm to 30 mm, four times higher than echocardiography lateral resolution. The wireless US power and data platform enables simultaneous power and data transfer employing a single piezoelectric transducer in the implant. The system is characterized with an 8.5 cm tissue phantom and achieves a US link efficiency of 1.8%. The uplink data is transmitted by using an ASK modulation scheme parallel to the power transfer and achieves a modulation index of 26%. The implantable system is tested in an in-vitro experimental setup, which emulates the arterial blood flow, and accurately detects fast pressure peaks for systolic and diastolic pressure changes at both 1.28 MHz and 1.6 MHz US powering frequencies, with corresponding uplink data rates of 40 kbps and 50 kbps.

Monitoring Macro- and Microcirculation in the Critically Ill: A Narrative Review

Circulatory shock is a common and important diagnosis in the critical care environment. Hemodynamic monitoring is quintessential in the management of shock. The currently used hemodynamic monitoring devices not only measure cardiac output but also provide data related to the prediction of fluid responsiveness, extravascular lung water, and also pulmonary vascular permeability. Additionally, these devices are minimally invasive and associated with fewer complications. The area of hemodynamic monitoring is progressively evolving with a trend toward the use of minimally invasive devices in this area. The critical care physician should be well-versed with current hemodynamic monitoring limitations and stay updated with the upcoming advances in this field so that optimal therapy can be delivered to patients in circulatory shock.

Towards continuous non-invasive blood pressure measurements-interpretation of the vasculature response to cuff inflation

Blood pressure (BP) surrogates, such as pulse transit time (PTT) or pulse arrival time (PAT), have been intensively explored with the goal of achieving cuffless, continuous, and accurate BP inference. In order to estimate BP, a one-point calibration strategy between PAT and BP is typically used. Recent research focuses on advanced calibration procedures exploiting the cuff inflation process to improve calibration robustness by active and controlled modulation of peripheral PAT, as measured via plethysmograph (PPG) and electrocardiogram (ECG) combination. Such methods require a detailed understanding of the mechanisms behind the vasculature's response to cuff inflation; for this, a model has recently been developed to infer the PAT-BP calibration from measured cuff-induced vasculature changes. The model, while promising, is still preliminary and only partially validated; in-depth analysis and further developments are still needed. Therefore, this work aims to improve our understanding of the cuff-vasculature interaction in this model; we seek to define potential opportunities and to highlight which aspects may require further study. We compare model behaviors with clinical data samples based on a set of observable characteristics relevant for BP inference and calibration. It is found that the observed behaviors are qualitatively well represented with the current simulation model and complexity, with limitations regarding the prediction of the onset of the distal arm dynamics and behavior changes at high cuff pressures. Additionally, a sensitivity analysis of the model's parameter space is conducted to show the factors that influence the characteristics of its observable outputs. It was revealed that easily controllable experimental variables, such as lateral cuff length and inflation rate, have a significant impact on cuff-induced vasculature changes. An interesting dependency between systemic BP and cuff-induced distal PTT change is also found, revealing opportunities for improved methods for BP surrogate calibration. However, validation via patient data shows that this relation does not hold for all patients, indicating required model improvements to be validated in follow up studies. These results provide promising directions to improve the calibration process featuring cuff inflation towards accurate and robust non-invasive blood pressure estimation.

Extracorporeal veno-venous ultrafiltration in congestive heart failure: What’s the state of the art? A mini-review

Hospitalizations for heart failure exceed 1 million per year in both the United States and Europe and more than 90% are due to symptoms and signs of fluid overload. Rates of rehospitalizations or emergency department visit at 60 days are remarkable regardless of whether loop diuretics were administered at low vs high doses or by bolus injection vs continuous infusion. Ultrafiltration (UF) has been considered a promising alternative to stepped diuretic therapy and it consists in the mechanical, adjustable removal of iso-tonic plasma water across a semipermeable membrane with the application of hydrostatic pressure gradient generated by a pump. Fluid removal with ultrafiltration presents several advantages such as elimination of higher amount of sodium with less neurohormonal activation. However, the conflicting results from UF studies highlight that patient selection and fluid removal targets are not completely understood. The best way to assess fluid status and therefore establish the fluid removal target is also still a matter of debate. Herein, we provide an up-to-date systematic review about the role of ultrafiltration among patients with fluid overload and its gaps in daily practice.

Accuracy of hemodynamic parameters derived by GE E-PiCCO in comparison with PiCCO® in patients admitted to the intensive care unit

To evaluate the agreement and accuracy of a novel advanced hemodynamic monitoring (AHM) device, the GE E-PiCCO module, with the well-established PiCCO® device in intensive care patients using pulse contour analysis (PCA) and transpulmonary thermodilution (TPTD). A total of 108 measurements were performed in 15 patients with AHM. Each of the 27 measurement sequences (one to four per patient) consisted of a femoral and a jugular indicator injection via central venous catheters (CVC) and measurement using both PiCCO (PiCCO® Jug and Fem) and GE E-PiCCO (GE E-PiCCO Jug and Fem) devices. For statistical analysis, Bland-Altman plots were used to compare the estimated values derived from both devices. The cardiac index measured via PCA (CIpc) and TPTD (CItd) was the only parameter that fulfilled all a priori-defined criteria based on bias and the limits of agreement (LoA) by the Bland-Altman method as well as the percentage error by Critchley and Critchley for all three comparison pairs (GE E-PiCCO Jug vs. PiCCO® Jug, GE E-PiCCO Fem vs. PiCCO® Fem, and GE E-PiCCO Fem vs. GE E-PiCCO Jug), while the GE E-PiCCO did not accurately estimate EVLWI, SVRI, SVV, and PPV values measured via the jugular and femoral CVC compared with values assessed by PiCCO®. Consequently, measurement discrepancy should be considered on evaluation and interpretation of the hemodynamic status of patients admitted to the ICU when using the GE E-PiCCO module instead of the PiCCO® device.

New Hemodynamic Parameters in Peri-Operative and Critical Care-Challenges in Translation

Hemodynamic monitoring technologies are evolving continuously-a large number of bedside monitoring options are becoming available in the clinic. Methods such as echocardiography, electrical bioimpedance, and calibrated/uncalibrated analysis of pulse contours are becoming increasingly common. This is leading to a decline in the use of highly invasive monitoring and allowing for safer, more accurate, and continuous measurements. The new devices mainly aim to monitor the well-known hemodynamic variables (e.g., novel pulse contour, bioreactance methods are aimed at measuring widely-used variables such as blood pressure, cardiac output). Even though hemodynamic monitoring is now safer and more accurate, a number of issues remain due to the limited amount of information available for diagnosis and treatment. Extensive work is being carried out in order to allow for more hemodynamic parameters to be measured in the clinic. In this review, we identify and discuss the main sensing strategies aimed at obtaining a more complete picture of the hemodynamic status of a patient, namely: (i) measurement of the circulatory system response to a defined stimulus; (ii) measurement of the microcirculation; (iii) technologies for assessing dynamic vascular mechanisms; and (iv) machine learning methods. By analyzing these four main research strategies, we aim to convey the key aspects, challenges, and clinical value of measuring novel hemodynamic parameters in critical care.

Real-Time Measurements of Relative Tidal Volume and Stroke Volume Using Electrical Impedance Tomography with Spatial Filters: A Feasibility Study in a Swine Model Under Normal and Reduced Ventilation

Continuous monitoring of both hemodynamic and respiratory parameters would be beneficial to patients, e.g., those in intensive care unit. The objective of this exploratory animal study was to test the feasibility of simultaneous measurements of relative tidal volume (rTV) and relative stroke volume (rSV) using an electrical impedance tomography (EIT) device equipped with a new real-time source separation algorithm implemented as two spatial filters. Five pigs were anesthetized and mechanically ventilated. The supplied tidal volume from a mechanical ventilator was reduced to 70, 50 and 30% from the 100% normal volume to simulate hypoventilation. The respiratory volume signal and cardiac volume signal were generated by applying the spatial filters to the acquired EIT data, from which values of rTV and rSV were extracted. The measured rTV values were compared with the TV values from the mechanical ventilator using the four-quadrant concordance analysis method. For changes in TV, the concordance rate in each animal ranged from 81.8% to 100%, while it was 92.5% when the data from all five animals were pooled together. When the measured rTV values for each animal were scaled to the absolute TV_EIT values in mL using the TV_Vent data from the mechanical ventilator, the smallest 95% limits of agreement (LoA) were - 6.04 and 7.44 mL for the 70% ventilation level, and the largest 95% LoA were - 18.1 and 19.4 mL for the 50% ventilation level. The percentage error between TV_EIT and TV_Vent was 10.3%. Although similar statistical analyses on rSV data could not be performed due to limited intra-animal variability, changes in rSV values measured by the EIT device were comparable to those measured by an invasive hemodynamic monitor. In this animal study, we were able to demonstrate the feasibility of an EIT device for noninvasive and simultaneous measurements of rTV and rSV in real time. However, the performance of the real-time source separation method needs to be further validated on animals and human subjects, particularly over a wide range of SV values. Future clinical studies are needed to assess the potential usefulness of the new method in dynamic cardiopulmonary monitoring and explore other clinical applications.

Optimization of the target strategy of perioperative infusion therapy based on monitoring data of central hemodynamics in order to prevent complications

Enhanced Recovery After Surgery (ERAS) protocols are increasingly used in the perioperative period around the world. The concept of goal-directed fluid therapy (GDT) is a key element of the ERAS protocols. Inadequate perioperative infusion therapy can lead to a number of complications, including the development of an infectious process, namely surgical site infections, pneumonia, urinary tract infections. Optimal infusion therapy is difficult to achieve with standard parameters (e.g., heart rate, blood pressure, central venous pressure), so there are various methods of monitoring central hemodynamics - from invasive, minimally invasive to non-invasive. The latter are increasingly used in clinical practice. The current evidence base shows that perioperative management, specifically the use of GDT guided by real-time, continuous hemodynamic monitoring, helps clinicians maintain a patient's optimal fluid balance. The manuscript presents the analytical data, which describe the benefits and basic principles of perioperative targeted infusion therapy based on central hemodynamic parameters to reduce the risk of complications.

Evaluation of a New Echocardiographic Tool for Cardiac Output Monitoring: An Experimental Study on A Controlled Hemorrhagic Shock Model in Anesthetized Piglets

Background: Cardiac output (CO) monitoring is recommended in patients with shock. The search for a reliable, rapid, and noninvasive tool is necessary for clinical practice. A new echocardiographic CO flow index (COF) is the automatic calculation of the sub-aortic VTI multiplied by the automatic calculation of the heart rate (HR). The primary objective of this study was to show the correlation between COF and CO measured by thermodilution (COth) in a controlled hemorrhagic shock model in anesthetized piglets. Secondary objectives were to show the correlation between COth and CO calculated from left outflow tract (LVOT) measurement and manual VTI (COman), and CO measured by LVOT measurement and VTIauto (COauto). Methods: Prospective interventional experimental study. In seventeen ventilated and anesthetized piglets, a state of hemorrhagic shock was induced, maintained, then resuscitated and stabilized. The gold standard for CO and stroke volume measurement was thermodilution (COth). Results: 191 measurements were performed. The correlation coefficients (r) between COth and COF, COman, and COauto were 0.73 [0.62; 0.81], 0.66 [0.56; 0.74], and 0.73 [0.63; 0.81], respectively. Conclusions: In this study, the COF appears to have a strong correlation to the COth. This automatic index, which takes into account the HR and does not require the measurement of LVOT, could be a rapidly obtained index in clinical practice.

Measurement of Cardiac Output Using an Ultrasonic Cardiac Output Monitor (USCOM) in Patients with Single-Ventricle Physiology

We evaluate the validity of cardiac index (CI) measurements utilizing the Ultrasonic Cardiac Output Monitor (USCOM), a non-invasive Doppler ultrasound device, by comparing measurements to cardiac catheterization-derived CI measurements in patients with single-ventricle physiology. USCOM measurements were repeated three times for each patient at the beginning of a cardiac catheterization procedure for twenty-six patients undergoing elective pre-Glenn or pre-Fontan catheterization. CI was measured by USCOM and was calculated from cardiac catheterization data using Fick's method. Bland-Altman analysis for CI showed bias of 0.95 L/min/m² with the 95% limits of agreement of - 1.85 and 3.75. Pearson's correlation coefficient was 0.89 (p < 0.001) indicating a strong positive relationship between USCOM and cardiac catheterization CI measurements. When excluding two patients with significant dilation of the neo-aortic valve (z-score >  + 5), the bias improved to 0.66 L/min/m² with the 95% limits of agreement of - 1.38 and 2.70. Percent error of limits of agreement was 34%. There was excellent intra-operator reproducibility of USCOM CI measurements with an intra-class coefficient of 0.96. We demonstrate the use of USCOM to measure CI in patients with single-ventricle physiology for the first time, showing acceptable agreement of the CI measurements between USCOM and cardiac catheterization with a high intra-operator reproducibility.

Fully implantable wireless batteryless vascular electronics with printed soft sensors for multiplex sensing of hemodynamics

The continuous monitoring of hemodynamics attainable with wireless implantable devices would improve the treatment of vascular diseases. However, demanding requirements of size, wireless operation, and compatibility with endovascular procedures have limited the development of vascular electronics. Here, we report an implantable, wireless vascular electronic system, consisting of a multimaterial inductive stent and printed soft sensors capable of real-time monitoring of arterial pressure, pulse rate, and flow without batteries or circuits. Developments in stent design achieve an enhanced wireless platform while matching conventional stent mechanics. The fully printed pressure sensors demonstrate fast response times, high durability, and sensing at small bending radii. The device is monitored via inductive coupling at communication distances notably larger than prior vascular sensors. The wireless electronic system is validated in artery models, while minimally invasive catheter implantation is demonstrated in an in vivo rabbit study. Overall, the vascular system offers an adaptable framework for comprehensive monitoring of hemodynamics.

[Haemodynamic monitoring in sepsis and septic shock]

Cardiovascular disturbances associated with sepsis cause hypoperfusion situations, which will negatively impact these patients' prognosis. The aim of haemodynamic monitoring is to guide the detection and correction of this hypoperfusion, and assist in decision making in optimising oxygen transport to tissues, primarily by manipulating cardiac output. This review seeks to summarise the different parameters of haemodynamic monitoring, the objectives of resuscitation, the physiological parameters, and the tools available to us for appropriate cardiac output manipulation.

Fluid and Hemodynamics

Several components of an Enhanced Recovery After Surgery (ERAS) pathway act to improve and simplify perioperative fluid and hemodynamic therapy. Modern perioperative fluid management has shifted away from the liberal fluid therapy and toward more individualized approaches. Clinical evidence has also emphasized the importance of maintaining adequate mean arterial pressure and avoiding intraoperative hypotension. Goal-directed hemodynamic therapy (GDHT), or the use of cardiac output monitoring to guide fluid and vasopressor use, has been shown to reduce complications, but its role within ERAS pathways is likely best-suited to high-risk patients or those undergoing high-risk procedures. This article reviews the mechanisms by which ERAS pathways aid the provider in hemodynamic management, reviews trends, and evidence regarding fluid and hemodynamic therapy approaches, and provides guidance on the practical implementation of these concepts within ERAS pathways.

Machines that save lives in the intensive care unit: the ultrasonography machine

This article highlights the ultrasonography machine as a machine that saves lives in the intensive care unit. We review its utility in the limited resource intensive care unit and some elements of machine design that are relevant to both the constrained operating environment and the well-resourced intensive care unit. As the ultrasonography machine can only save lives, if is operated by a competent intensivist; we discuss the challenges of training the frontline clinician to become competent in critical care ultrasonography followed by a review of research that supports its use.

Application of perioperative hemodynamics today and potentials for tomorrow

Hemodynamic (HD) monitoring remains integral to the assessment and management of perioperative and critical care patients. This review article seeks to provide an update on the different types of flow-guided HD monitoring technologies available, highlight their limitations, and review the therapies associated with the application of these technologies. Additionally, we will also comment on the expanding roles of HD monitoring in the future.

Noninvasive Beat-To-Beat Stroke Volume Measurements to Determine Preload Responsiveness During Mini-Fluid Challenge in a Swine Model: A Preliminary Study

ABSTRACT

Cardiac output (CO) is an important parameter in fluid management decisions for treating hemodynamically unstable patients in intensive care unit. The gold standard for CO measurements is the thermodilution method, which is an invasive procedure with intermittent results. Recently, electrical impedance tomography (EIT) has emerged as a new method for noninvasive measurements of stroke volume (SV). The objectives of this paper are to compare EIT with an invasive pulse contour analysis (PCA) method in measuring SV during mini-fluid challenge in animals and determine preload responsiveness with EIT. Five pigs were anesthetized and mechanically ventilated. After removing 25% to 30% of the total blood from each animal, multiple fluid injections were conducted. The EIT device successfully tracked changes in SV beat-to-beat during varying volume states, i.e., from hypovolemia and preload responsiveness to target volume and volume overload. From a total of 50 100-mL fluid injections on five pigs (10 injections per pig), the preload responsiveness value was as large as 32.3% in the preload responsiveness state while in the volume overload state it was as low as -4.9%. The bias of the measured SV data using EIT and PCA was 0 mL, and the limits of agreement were ±3.6 mL in the range of 17.6 mL to 51.0 mL. The results of the animal experiments suggested that EIT is capable of measuring beat-to-beat SV changes during mini-fluid challenge and determine preload responsiveness. Further animal and clinical studies will be needed to demonstrate the feasibility of the EIT method as a new tool for fluid management.

Value of early critical care transthoracic echocardiography for patients undergoing mechanical ventilation: a retrospective study

OBJECTIVES

To evaluate whether early intensive care transthoracic echocardiography (TTE) can improve the prognosis of patients with mechanical ventilation (MV).

DESIGN

A retrospective cohort study.

SETTING

Patients undergoing MV for more than 48 hours, based on the Medical Information Mart for Intensive Care III (MIMIC-III) database and the eICU Collaborative Research Database (eICU-CRD), were selected.

PARTICIPANTS

2931 and 6236 patients were recruited from the MIMIC-III database and the eICU database, respectively.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was in-hospital mortality. Secondary outcomes were 30-day mortality from the date of ICU admission, days free of MV and vasopressors 30 days after ICU admission, use of vasoactive drugs, total intravenous fluid and ventilator settings during the first day of MV.

RESULTS

We used propensity score matching to analyse the association between early TTE and in-hospital mortality and sensitivity analysis, including the inverse probability weighting model and covariate balancing propensity score model, to ensure the robustness of our findings. The adjusted OR showed a favourable effect between the early TTE group and in-hospital mortality (MIMIC: OR 0.78; 95% CI 0.65 to 0.94, p=0.01; eICU-CRD: OR 0.76; 95% CI 0.67 to 0.86, p<0.01). Early TTE was also associated with 30-day mortality in the MIMIC database (OR 0.71, 95% CI 0.57 to 0.88, p=0.001). Furthermore, those who had early TTE had both more ventilation-free days (only in eICU-CRD: 23.48 vs 24.57, p<0.01) and more vasopressor-free days (MIMIC: 18.22 vs 20.64, p=0.005; eICU-CRD: 27.37 vs 28.59, p<0.001) than the control group (TTE applied outside of the early TTE and no TTE at all).

CONCLUSIONS

Early application of critical care TTE during MV is beneficial for improving in-hospital mortality. Further investigation with prospectively collected data is required to validate this relationship.

Noninvasive cardiac output measurement is inaccurate in patients with severe aortic valve stenosis undergoing transcatheter aortic valve implantation

Background

Noninvasive cardiac output (CO) measured using ClearSight™ eliminates the need for intra-arterial catheter insertion. The purpose of this study was to examine the accuracy of non-invasive CO measurement in patients with severe aortic stenosis (AS).

Methods

Twenty-eight patients undergoing elective transcatheter aortic valve implantation were prospectively enrolled in this study. The CO was simultaneously measured twice before and twice after valve deployment (total of four times) per patient, and the CO was compared between the ClearSight (CO_ClearSight) system and the pulmonary artery catheter (PAC) thermodilution (CO_TD) method as a reference. The Bland-Altman analysis was used to compare the percentage errors between the methods.

Results

A total of 112 paired data points were obtained. The percentage error between the CO_ClearSight and CO_TD was 43.1%. The paired datasets were divided into the following groups according to the systemic vascular resistance index (SVRI): low (< 1,200 dyne s/cm⁵/m²) and normal (1,200–2,500 dyne s/cm⁵/m²). The percentage errors were 44.9% and 49.4%, respectively. The discrepancy of CO between CO_ClearSight and CO_TD was not significantly correlated with SVRI (r = −0.06, P < 0.001). The polar plot analysis showed the trending ability of the CO_ClearSight after artificial valve deployment was 51.1% which below the acceptable cut-off (92%).

Conclusions

The accuracy and the trending ability of the ClearSight CO measurements were not acceptable in patients with severe AS. Therefore, the ClearSight system is not interchangeable with the PAC thermodilution for determining CO in this population.

Simulating Radial Pressure Waveforms with a Mock Circulatory Flow Loop to Characterize Hemodynamic Monitoring Systems

PURPOSE

Mock circulatory loops (MCLs) can reproducibly generate physiologically relevant pressures and flows for cardiovascular device testing. These systems have been extensively used to characterize the performance of therapeutic cardiac devices, but historically MCLs have had limited use for assessing patient monitoring systems. Here, we adapted an MCL to include peripheral components and evaluated its utility for qualitative and quantitative benchtop testing of hemodynamic monitoring devices.

METHODS

An MCL was designed to simulate three physiological hemodynamic states: normovolemia, cardiogenic shock, and hyperdynamic circulation. The system was assessed for stability in pressure and flow values over time, repeatability, waveform morphology, and systemic-peripheral pressure relationships.

RESULTS

For each condition, cardiac output was controlled to the nearest 0.2 L/min, and flow rate and mean arterial pressure remained stable and repeatable over a 60-s period (n = 5, standard deviation of ± 0.1 L/min and ± 0.84 mmHg, respectively). Transfer function analyses showed that the systemic-peripheral relationships could be adequately manipulated. The results from this MCL were comparable to those from other published MCLs and computational simulations. However, resolving current limitations of the system would further improve its utility. Three pulse contour analysis algorithms were applied to the pressure and flow data from the MCL to demonstrate the potential role of MCLs in characterizing hemodynamic monitoring systems.

CONCLUSION

Overall, the development of robust analysis methods in conjunction with modified MCLs can expand device testing applications to hemodynamic monitoring systems. Properly validated MCLs can create a stable and reproducible environment for testing patient monitoring systems over their entire operating ranges prior to clinical use.

Modulation of Pulse Propagation and Blood Flow via Cuff Inflation-New Distal Insights

In standard critical care practice, cuff sphygmomanometry is widely used for intermittent blood pressure (BP) measurements. However, cuff devices offer ample possibility of modulating blood flow and pulse propagation along the artery. We explore underutilized arrangements of sensors involving cuff devices which could be of use in critical care to reveal additional information on compensatory mechanisms. In our previous work, we analyzed the response of the vasculature to occlusion perturbations by means of observations obtained non-invasively. In this study, our aim is to (1) acquire additional insights by means of invasive measurements and (2) based on these insights, further develop cuff-based measurement strategies. Invasive BP experimental data is collected downstream from the cuff in two patients monitored in the OR. It is found that highly dynamic processes occur in the distal arm during cuff inflation. Mean arterial pressure increases in the distal artery by 20 mmHg, leading to a decrease in pulse transit time by 20 ms. Previous characterizations neglected such distal vasculature effects. A model is developed to reproduce the observed behaviors and to provide a possible explanation of the factors that influence the distal arm mechanisms. We apply the new findings to further develop measurement strategies aimed at acquiring information on pulse arrival time vs. BP calibration, artery compliance, peripheral resistance, artery-vein interaction.

The autonomic nervous system in septic shock and its role as a future therapeutic target: a narrative review

The autonomic nervous system (ANS) regulates the cardiovascular system. A growing body of experimental and clinical evidence confirms significant dysfunction of this regulation during sepsis and septic shock. Clinical guidelines do not currently include any evaluation of ANS function during the resuscitation phase of septic shock despite the fact that the severity and persistence of ANS dysfunction are correlated with worse clinical outcomes. In the critical care setting, the clinical use of ANS-related hemodynamic indices is currently limited to preliminary investigations trying to predict and anticipate imminent clinical deterioration. In this review, we discuss the evidence supporting the concept that, in septic shock, restoration of ANS-mediated control of the cardiovascular system or alleviation of the clinical consequences induced by its dysfunction (e.g., excessive tachycardia, etc.), may be an important therapeutic goal, in combination with traditional resuscitation targets. Recent studies, which have used standard and advanced monitoring methods and mathematical models to investigate the ANS-mediated mechanisms of physiological regulation, have shown the feasibility and importance of monitoring ANS hemodynamic indices at the bedside, based on the acquisition of simple signals, such as heart rate and arterial blood pressure fluctuations. During the early phase of septic shock, experimental and/or clinical studies have shown the efficacy of negative-chronotropic agents (i.e., beta-blockers or ivabradine) in controlling persistent tachycardia despite adequate resuscitation. Central α-2 agonists have been shown to prevent peripheral adrenergic receptor desensitization by reducing catecholamine exposure. Whether these new therapeutic approaches can safely improve clinical outcomes remains to be confirmed in larger clinical trials. New technological solutions are now available to non-invasively modulate ANS outflow, such as transcutaneous vagal stimulation, with initial pre-clinical studies showing promising results and paving the way for ANS modulation to be considered as a new potential therapeutic target in patients with septic shock.

The Reproducibility of the Point of Care Microcirculation (POEM) Score When Used to Assess Critically Ill Patients: A Multicenter Prospective Observational Study

BACKGROUND

The current standard of analyzing microcirculatory video microscopy is time-consuming and occurs away from the patient, limiting its clinical utility. Point-of-care assessment with incident dark field (IDF) microscopy, however, may offer greater clinical applicability. We aimed to determine the reproducibility of the Point of Care Microcirculation (POEM) tool when used at the bedside in critically ill patients.

METHODS

A multinational, multicenter, prospective observational study of adult intubated patients was undertaken during a 9-month period in Germany, the United Kingdom, and the United States. A user recorded a batch of four standardized video clips from each patient, calculated a POEM score and recorded the time for image acquisition. A second user blinded to the first repeated this process. Patients with video clips of poor quality were excluded. At a later date, the two users again blinded themselves to reassess both their own clips and those of the other user. Basic demographic information was recorded. Intrauser reliability (an individual user rescoring the same batch of videos after blinding), interuser reliability (a second user rescoring the other user's video batch after blinding), and test-retest reliability (two users individually capturing videos and recording POEM scores) were assessed using a linearly weighted kappa statistic for ordinal data.

RESULTS

Sixty-five patients were included in the final analysis. Observer agreement was substantial for all tests. Intrauser agreement was 0.73 (0.95 CI 0.64-0.81), interuser agreement 0.71 (0.95 CI 0.63-0.79), and test-retest agreement 0.75 (0.95 CI 0.65-0.86). Average time to record videos and assess POEM scores 7:34 ± 3:37 minutes.

CONCLUSIONS

Point-of-care assessment of the microcirculation using IDF video microscopy and POEM scoring appears to be both a feasible and reproducible approach to microcirculatory assessment. Testing of the score in critically ill patients showed substantial agreement within and between investigators, but further studies should validate its utility as a tool to guide shock resuscitation.

Four different methods of measuring cardiac index during cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

BACKGROUND

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are high-risk extensive abdominal surgery. During high-risk surgery, less invasive methods for cardiac index (CI) measurement have been widely used in operating theater. We investigated the accuracy of CI derived from different methods (FroTrac, ProAQT, ClearSight, and arterial pressure waveform analysis [APWA], from PICCO) and compared them to transpulmonary thermodilution (TPTD) during CRS and HIPEC in the operative room and intensive care unit (ICU).

METHODS

Twenty-five patients scheduled for CRS-HIPEC were enrolled. During nine predefined time-points, simultaneous hemodynamic measurements were performed in the operating room and ICU. Absolute and relative changes of CI were analyzed using a Bland-Altman plot, four-quadrant plot, and interchangeability.

RESULTS

The mean bias was -0.1 L/min/m2 for ClearSight, ProAQT, and APWA and was -0.2 L/min/m2 for FloTrac compared with TPTD. All devices had large limits of agreement (LoA). The percentage of errors and interchangeabilities for ClearSight, FloTrac, ProAQT, and APWA were 50%, 50%, 54%, 36% and 36%, 47%, 40%, 72%, respectively. Trending capabilities expressed as concordance using clinically significant CI changes were -7º ± 39º, -19º ± 38º, -13º ± 41º, and -15º ± 39º. Interchangeability in trending showed low percentages of interchangeable and gray zone data pairs for all devices.

CONCLUSIONS

During CRS-HIPEC, ClearSight, FloTrac and ProAQT systems were not able to reliably measure CI compared to TPTD. Reproducibility of changes over time using concordance, angular bias, radial LoA, and interchangeability in trending of all devices was unsatisfactory.

Perioperative echocardiography-guided hemodynamic therapy in high-risk patients: a practical expert approach of hemodynamically focused echocardiography

The number of high-risk patients undergoing surgery is growing. To maintain adequate hemodynamic functioning as well as oxygen delivery to the vital organs (DO2) amongst this patient population, a rapid assessment of cardiac functioning is essential for the anesthesiologist. Pinpointing any underlying cardiovascular pathophysiology can be decisive to guide interventions in the intraoperative setting. Various techniques are available to monitor the hemodynamic status of the patient, however due to intrinsic limitations, many of these methods may not be able to directly identify the underlying cause of cardiovascular impairment. Hemodynamic focused echocardiography, as a rapid diagnostic method, offers an excellent opportunity to examine signs of filling impairment, cardiac preload, myocardial contractility and the function of the heart valves. We thus propose a 6-step-echocardiographic approach to assess high-risk patients in order to improve and maintain perioperative DO2. The summary of all echocardiographic based findings allows a differentiated assessment of the patient's cardiovascular function and can thus help guide a (patho)physiological-orientated and individualized hemodynamic therapy.

Hemodynamic support in septic shock

PURPOSE OF REVIEW

The current article reviews recent findings on the monitoring and hemodynamic support of septic shock patients.

RECENT FINDINGS

The ultimate goal of hemodynamic resuscitation is to restore tissue oxygenation. A multimodal approach combining global and regional markers of tissue hypoxia seems appropriate to guide resuscitation. Several multicenter clinical trials have provided evidence against an aggressive fluid resuscitation strategy. Fluid administration should be personalized and based on the evidence of fluid responsiveness. Dynamic indices have proven to be highly predictive of responsiveness. Recent data suggest that balanced crystalloids may be associated with less renal failure. When fluid therapy is insufficient, a multimode approach with different types of vasopressors has been suggested as an initial approach. Dobutamine remains the firs inotropic option in patients with persistent hypotension and decrease ventricular systolic function. Calcium sensitizer and phosphodiesterase inhibitors may be considered, but evidence is still limited. Veno-arterial extracorporeal membrane oxygenation may be considered in selected unresponsive patients, particularly with myocardial depression, and in a highly experienced center.

SUMMARY

Resuscitation should be personalized and based on global and regional markers of tissue hypoxia as well as the fluid responsiveness indices. The beneficial effect of multimode approach with different types of vasopressors, remains to be determined.

[Perioperative optimization using hemodynamically focused echocardiography in high-risk patients-A practice guide]

BACKGROUND

The number of high-risk patients undergoing surgery is steadily increasing. In order to maintain and, if necessary, optimize perioperative hemodynamics as well as the oxygen supply to the organs (DO₂) in this patient population, a timely assessment of cardiac function and the underlying pathophysiological causes of hemodynamic instability is essential for the anesthesiologist. A variety of hemodynamic monitoring procedures are available for this purpose; however, due to method-immanent limitations they are often not able to directly identify the underlying cause of cardiovascular impairment.

OBJECTIVE

To present a stepwise algorithm for a perioperative echocardiography-based hemodynamic optimization in noncardiac surgery high-risk patients. In this context, echocardiography on demand according to international guidelines can be performed under certain conditions (hemodynamic instability, nonresponse to hemodynamic treatment) as well as in the context of a planned intraoperative procedure, mostly as a transesophageal echocardiography.

METHODS AND RESULTS

Hemodynamically focused echocardiography as a rapidly available bedside method, enables the timely diagnosis and assessment of cardiac filling obstructions, volume status and volume response, right and left heart function, and the function of the heart valves.

CONCLUSION

Integrating all echocardiographic findings in a differentiated assessment of the patient's cardiovascular function enables a (patho)physiologically oriented and individualized hemodynamic treatment.

Carotid Blood Flow-Guided Fluid Therapy in Cytoreductive Surgery With Hyperthermic Intraperitoneal Chemotherapy: A Case Report

Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy is associated with significant volume shifts and requires meticulous hemodynamic management. The conventional and arbitrary "liberal" and "restrictive" fluid regimens are now being challenged. With increasing recognition of the need to individualize perioperative fluid therapy, dynamic assessment of fluid status and hemodynamic response to administration of fluids have become vital. Herein, we describe a case in which point of care ultrasound of the carotid artery and derived parameters were used to guide intraoperative fluid management. We discuss the reliability of this technique and the potential advantages it could offer.

Inferior vena cava dilation predicts global cardiac dysfunction in acute respiratory distress syndrome: A strain echocardiographic study

PURPOSE

Limited data exist on the utility of ultrasonographic evaluation of inferior vena cava (IVC) in acute respiratory distress syndrome (ARDS). We studied the value of IVC diameter in assessing cardio-circulatory performance in ARDS using strain echocardiography.

MATERIALS AND METHODS

Retrospective cross-sectional analysis of Doppler echocardiograms of patients with moderate-severe ARDS was performed. Right ventricle (RV) parameters, IVC diameter, and left ventricle (LV) systolic and diastolic parameters were collected. RV free wall strain (RVFWS) and LV global longitudinal strain (LVGLS) were calculated.

RESULTS

Fifty-one patients were dichotomized into two groups: with IVC > 2.1 cm (dilated) and with IVC ≤ 2.1 cm (nondilated). The dilated IVC group presented worse hypoxemic profile, hypotension, and poor perfusion markers. No significant associations with positive end-expiratory pressure or lung mechanics were observed. Dilated IVC was associated with impaired RV function, high central venous pressure, elevated pulmonary artery pressure, and LV systolic and diastolic dysfunctions. Strongest predictors of a dilated IVC were RVFWS, LVGLS, and tissue Doppler mitral annular early diastolic velocity. Dilated IVC predicted a global cardiac dysfunction defined by strain echocardiography (GCDS) with high sensitivity and specificity.

CONCLUSIONS

In ARDS, strain echocardiography analyses demonstrated that a dilated IVC is associated with GCDS and impaired hemodynamics independent of lung mechanics. A dilated IVC should be considered a marker of circulatory distress, signaling the potential necessity for improved hemodynamic optimization.

Cardiac output estimation using pulse wave analysis-physiology, algorithms, and technologies: a narrative review

Pulse wave analysis (PWA) allows estimation of cardiac output (CO) based on continuous analysis of the arterial blood pressure (AP) waveform. We describe the physiology of the AP waveform, basic principles of PWA algorithms for CO estimation, and PWA technologies available for clinical practice. The AP waveform is a complex physiological signal that is determined by interplay of left ventricular stroke volume, systemic vascular resistance, and vascular compliance. Numerous PWA algorithms are available to estimate CO, including Windkessel models, long time interval or multi-beat analysis, pulse power analysis, or the pressure recording analytical method. Invasive, minimally-invasive, and noninvasive PWA monitoring systems can be classified according to the method they use to calibrate estimated CO values in externally calibrated systems, internally calibrated systems, and uncalibrated systems.

Application of Critical Care Ultrasound in Patients With COVID-19: Our Experience and Perspective

Up to April 4, 2020, the novel coronavirus disease-2019 COVID-19 has affected more than 1 099000 patients and has become a major global health concern. World Health Organization (WHO) has defined COVID-19 as a global pandemic. Critical care ultrasound (CCUS) can rapidly acquire the image of lung and other organs and demonstrate the pathophysiological changes to guide precise therapy in COVID-19 pneumonia without radiation or interfering with personal protective equipment. In addition, the application of CCUS can cover the whole courses from the fever clinic to the intensive care unit to improve the treatment. We would like to present the CCUS features about COVID-19 pneumonia and share the application experience of CCUS in Wuhan, China, and hope it works for physicians worldwide to solve the problem and improve the outcome.

A modelling framework for assessment of arterial compliance by fusion of oscillometry and pulse wave velocity information

BACKGROUND AND OBJECTIVES

Measurement of arterial compliance is recognized as important for clinical use and for enabling better understanding of circulatory system regulation mechanisms. Estimation of arterial compliance involves either a direct measure of the ratio between arterial volume and pressure changes or an inference from the pulse wave velocity (PWV). In this study we demonstrate an approach to assess arterial compliance by fusion of these two information sources. The approach is based on combining oscillometry as used for blood pressure inference and PWV measurements based on ECG/PPG. Enabling reliable arterial compliance measurements will contribute to the understanding of regulation mechanisms of the arterial tree, possibly establishing arterial compliance as a key measure relevant in hemodynamic monitoring.

METHODS

A measurement strategy, a physiological model, and a framework based on Bayesian principles are developed for measuring changes in arterial compliance based on combining oscillometry and PWV data. A simulation framework is used to study and validate the algorithm and measurement principle in detail, motivated by previous experimental findings.

RESULTS

Simulations demonstrate the possibility of inferring arterial compliance via fusion of simultaneously acquired volume/pressure relationships and PWV data. In addition, the simulation framework demonstrates how Bayesian principles can be used to handle low signal - to - noise ratio and partial information loss.

CONCLUSIONS

The developed simulation framework shows the feasibility of the proposed approach for assessment of arterial compliance by combining multiple data sources. This represents a first step towards integration of arterial compliance measurements in hemodynamic monitoring using existing clinical technology. The Bayesian approach is of particular relevance for such patient monitoring settings, where measurements are repeated frequently, context is relevant, and data is affected by artefacts. In addition, the simulation framework is necessary for future clinical-study design, in order to determine device specifications and the extent to which noise affects the inference process.

Method for measurement of arterial compliance by fusion of oscillometry and pulse wave velocity

Up until now estimation of arterial compliance has been performed either by analysis of arterial pressure changes with respect to volume changes or by inference based on pulse wave velocity (PWV). In this study we demonstrate the possibility of an approach to assess arterial compliance by fusing the two information sources namely the pressure/volume relationship obtained from oscillography and PWV data. The goal is to assess arterial properties easily and robustly, enhancing current hemodynamic monitoring. The approach requires as input signals: an electrocardiogram (ECG), a photo- plethysmogram (PPG) and the arterial oscillation as measured during non-invasive blood pressure measurements based on oscillometry with a cuff. These signals are fused by an algorithm using Bayesian principles underpinned by a physiological model. In our simulations, we demonstrate the feasibility to infer arterial compliance by our proposed strategy. A very first measurement on a healthy volunteer supports our findings from the simulation.Clinical Relevance- Arterial compliance/stiffness is recognized as a key hemodynamic parameter, which is not easily accessible and not a standard parameter currently. The presented method and obtained results are encouraging for future research in this area.