Clinical review: Does it matter which hemodynamic monitoring system is used?

The Investigation of Bio-impedance Analysis at a Wrist Phantom with Two Pulsatile Arteries

PURPOSE

Bio-impedance analysis (BIA) has been widely investigated for hemodynamic monitoring. However, previous works rarely modelled two synchronously pulsatile arteries (representing the radial and ulnar arteries) in the wrist/forearm model. This work aims to clarify and quantify the influences of two pulsatile arteries on BIA.

METHODS

First, two blood-filled arteries were structured in a 3D wrist segment using the finite element method (FEM). Afterwards, an easy-to-produce two-arteries artificial wrist was fabricated with two components: gelatine-based surrounding tissue phantom and saline blood phantom. A syringe driver was utilised to constrict the arteries, and the impedance signals were measured using a Multi-frequency Impedance Analyser (MFIA).

RESULTS

Both simulation and experimental results demonstrated the non-negligible influences of the ulnar artery on the overall BIA, inducing unwanted resistance changes to the acquired signals from the radial artery. The phantom experiments revealed the summation of the individual resistance changes caused by a single pulsatile artery was approximately equal to the measured resistance change caused by two synchronously pulsatile arteries, confirming the measured impedance signal at the wrist contains the pulsatile information from both arteries.

CONCLUSION

This work is the first simulation and phantom investigation into two synchronously pulsatile arteries under BIA in the distal forearm, providing a better insight and understanding in the morphology of measured impedance signals. Future research can accordingly select either a small spacing 4-spot electrode configuration for a single artery sensing or a band electrode configuration for overall pulsatile arteries sensing. A more accurate estimation of blood volume change and pulse wave analysis (PWA) could help to develop cuffless blood pressure measurement (BPM).

Influence of blood hemodynamics on the treatment outcomes of limited fluid resuscitation in emergency patients with traumatic hemorrhagic shock

OBJECTIVES

Traumatic hemorrhagic shock is a major death-related factor contributing to mortality in emergencies and can be effectively handled by the Limited Fluid Resuscitation (LFR) method. In the current investigation, the authors analyzed the influence of different administrating blood pressure on the treatment outcomes of LFR.

METHODS

276 participants were enrolled in the current study retrospectively from January 2016 to December 2021 and were divided into three groups based on the administrating blood pressure of LFR. The difference among the three groups regarding serum levels of cytokines as well as blood hemodynamics parameters was analyzed.

RESULTS

The results showed after the T2 stage treatment, cytokine levels in the three groups were all significantly influenced by different LFR strategies with medium MAP showing the strongest effects on the expression of all cytokine genes. Moreover, the MAP value was in positive correlation with IL-6, IL-10, and TNF-α levels, but showed no clear relation with IL-4 level in all three groups. Regarding the effects on hemodynamics parameters, the levels of CVP, CO, and CI were slightly increased by the different LFR administrating strategies, and the effect of medium and high MAP was statistically stronger than that of low MAP.

CONCLUSION

The present results showed that LFR would influence serum inflammatory levels by improving blood hemodynamics parameters. Medium MAP showed the strongest improving effects with the least side effects, which can be employed as the optimal administrating strategy for LFR in the future.

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.

Non invasive hemodynamic monitoring for fluids and blood resuscitation during placenta praevia accreta cesarean delivery: a retrospective observational study

BACKGROUND

We carry out a retrospective observational analysis of clinical records of patients with major placenta praevia who underwent cesarean section surgery over a period of 20 months in our hospital. Out of a total of 40 patients, 20 were subjected to Goal-Directed Therapy (GDT) implemented with non-invasive hemodynamic monitoring using the EV1000 ClearSight system (Group I) and 20 to standard hemodynamic monitoring (Group II). Given the risk of conspicuous blood loss, this study evaluate the impact on maternal and fetal health of GDT relative to standard hemodynamic monitoring.

RESULTS

Average total infusion of fluids was 1600 +/- 350 ml. Use of blood products occurred in 29 patients (72,5%), of which 11 had a hysterectomy and 8 were treated with Bakri Balloons. For 2 patients > 1000 mL of concentrated red blood cells were used. When stroke volume index SVI dropped below 35 mL/m2/beat, it responded well to the infusion of at least 2 crystalloid boluses (5 ml/kg) in 7 patients. Cardiac index (CI) increased in 8 patients in concomitance with a reduction in medium arterial pressure (MAP), but the use of ephedrine (10 mg iv) re-established acceptable baseline values. Group I means are higher than Group II means for MAP, lower for RBC usage, end-of-surgery maternal lactates and fetal pH, and for LOS. Statistical analysis determines that the null hypotheses of equalities between Groups I and II can be rejected for all measures apart from MAP at baseline and induction. Proportions of serious complications in Groups I and II are respectively 10% and 32% and Boschloo's test rejects the null of equality of proportions against the alternative hypothesis of lower proportion of occurrence in Group I than in Group II.

CONCLUSIONS

Hypovolemia can lead to vasoconstriction and inadequate perfusion with decreased oxygen delivery to organs and peripheral tissues and ultimately cause organ dysfunction. Despite the small sample size due to the rarity of the pathology, our statistical analysis finds evidence in favor of more favorable clinical outcomes for patients who received GDT implemented with non-invasive hemodynamic monitoring infusion relative to patients who received standard hemodynamic monitoring.

Carotid Doppler Ultrasonography for Hemodynamic Assessment in Critically Ill Children

An accurate assessment of cardiovascular performance is essential to predict and evaluate hemodynamic response to interventions. The objective of this prospective study was to assess whether point-of-care ultrasonography of the common carotid artery (CCA) can estimate the stroke volume (SV) and cardiac index (Ci) of critically ill children. Participants underwent Doppler ultrasonography of the left CCA and transthoracic echocardiography (TTE). Variables measured by TTE were SV and Ci. Carotid blood flow (CBF) was calculated based on both systolic velocity-time integral (CBF_(s)) and total velocity-time integral (CBF_(t)). Carotid corrected flow time(CFT)was also determined. A total of 50 children were enrolled. The median age and weight of participants were 36.0 months and 14.2 kg, respectively. Both CBF_(s) and CBF_(t) correlated very strongly with SV (ρ = 0.98 and 0.97, respectively) and Ci (ρ = 0.96 and 0.92, respectively). Agreement analysis showed low biases and clinically acceptable percentage errors between variables measured by TTE (SV and Ci) and those estimated by Doppler ultrasonography. Linear regression analysis revealed that the Ci of mechanically ventilated children can be estimated by the following equation: [Formula: see text]. CFT did not significantly correlate with SV or Ci (ρ = 0.27 and 0.05, respectively). Doppler ultrasonography of the left CCA is able to estimate the SV and Ci of critically ill children. Therefore, the CDU may be considered as an alternative for estimating Ci in critically ill children when TTE is not feasible or available.

Developments in pediatrics in 2020: choices in allergy, autoinflammatory disorders, critical care, endocrinology, genetics, infectious diseases, microbiota, neonatology, neurology, nutrition, ortopedics, respiratory tract illnesses and rheumatology

In this article, we describe the advances in the field of pediatrics that have been published in the Italian Journal of Pediatrics in 2020. We report progresses in understanding allergy, autoinflammatory disorders, critical care, endocrinology, genetics, infectious diseases, microbiota, neonatology, neurology, nutrition, orthopedics, respiratory tract illnesses, rheumatology in childhood.

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.

Pharmacodynamic analysis of a fluid challenge with 4 ml kg-1 over 10 or 20 min: a multicenter cross-over randomized clinical trial

Purpose

A number of studies performed in the operating room evaluated the hemodynamic effects of the fluid challenge (FC), solely considering the effect before and after the infusion. Few studies have investigated the pharmacodynamic effect of the FC on hemodynamic flow and pressure variables. We designed this trial aiming at describing the pharmacodynamic profile of two different FC infusion times, of a fixed dose of 4 ml kg⁻¹.

Methods

Forty-nine elective neurosurgical patients received two consecutive FCs of 4 ml kg⁻¹ of crystalloids in 10 (FC₁₀) or 20 (FC₂₀) minutes, in a random order. Fluid responsiveness was defined as stroke volume index increase ≥ 10%. We assessed the net area under the curve (AUC), the maximal percentage difference from baseline (d_max), time when the d_max was observed (t_max), change from baseline at 1-min (d₁) and 5-min (d₅) after FC end.

Results

After FC₁₀ and FC_20, 25 (51%) and 14 (29%) of 49 patients were classified as fluid responders (p = 0.001). With the exception of the AUCs of SAP and MAP, the AUCs of all the considered hemodynamic variables were comparable. The d_max and the t_max were overall comparable. In both groups, the hemodynamic effects on flow variables were dissipated within 5 min after FC end.

Conclusions

The infusion time of FC administration affects fluid responsiveness, being higher for FC₁₀ as compared to FC₂₀. The effect on flow variables of either FCs fades 5 min after the end of infusion.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10877-021-00756-3.

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.

Multivariable haemodynamic approach to predict the fluid challenge response: A multicentre cohort study

BACKGROUND

Beat-to-beat stroke volume (SV) results from the interplay between left ventricular function and arterial load. Fluid challenge induces time-dependent responses in cardiac performance and peripheral vascular and capillary characteristics.

OBJECTIVE

To assess whether analysis of the determinants of the haemodynamic response during fluid challenge can predict the final response at 10 and 30 min.

DESIGN

Observational multicentric cohort study.

SETTING

Three university ICUs.

PATIENTS

85 ICU patients with acute circulatory failure diagnosed within the first 48 h of admission.

INTERVENTION(S)

The fluid challenge consisted of 500 ml of Ringer's solution infused over 10 min. A SV index increase at least 10% indicated fluid responsiveness.

MAIN OUTCOME MEASURES

The SV, pulse pressure variation (PPV), arterial elastance, the systolic-dicrotic pressure difference (SAP-Pdic) and cardiac cycle efficiency (CCE) were measured at baseline, 1, 2, 3, 4, 5, 10, 15 and 30 min after the start of the fluid challenge. All haemodynamic data were submitted to a univariable logistic regression model and a multivariable analysis was then performed using the significant variables given by univariable analysis.

RESULTS

The multivariable model including baseline PPV, and the changes of arterial elastance at 1 min and of the CCE and SAP-Pdic at 5 min when compared with their baseline values, correctly classified 80.5% of responders and 90.7% of nonresponders at 10 min. For the response 30 min after starting the fluid challenge, the model, including the changes of PPV, CCE, SAP-Pdic at 5 min and of arterial elastance at 10 min compared with their baseline values, correctly identified 93.3% of responders and 91.4% of nonresponders.

CONCLUSION

In a selection of mixed ICU patients, a statistical model based on a multivariable analysis of the changes of PPV, CCE, arterial elastance and SAP-Pdic, with respect to baseline values, reliably predicts both the early and the late response to a standardised fluid challenge.

TRIAL REGISTRATION

ACTRN12617000076370.

Bioimpedance analysis as a tool for hemodynamic monitoring: overview, methods and challenges

Recent advances in hemodynamic monitoring have seen the advent of non-invasive methods which offer ease of application and improve patient comfort. Bioimpedance Analysis or BIA is one of the currently employed non-invasive techniques for hemodynamic monitoring. Impedance Cardiography (ICG), one of the implementations of BIA, is widely used as a non-invasive procedure for estimating hemodynamic parameters such as stroke volume (SV) and cardiac output (CO). Even though BIA is not a new diagnostic technique, it has failed to gain consensus as a reliable measure of hemodynamic parameters. Several devices have emerged for estimating CO using ICG which are based on evolving methodologies and techniques to calculate SV. However, the calculations are generally dependent on the electrode configurations (whole body, segmental or localised) as well as the accuracy of different techniques in tracking blood flow changes. Blood volume changes, concentration of red blood cells, pulsatile velocity profile and ambient temperature contribute to the overall conductivity of blood and hence its impedance response during flow. There is a growing interest in investigating limbs for localised BIA to estimate hemodynamic parameters such as pulse wave velocity. As such, this paper summarises the current state of hemodynamic monitoring through BIA in terms of different configurations and devices in the market. The conductivity of blood flow has been emphasized with contributions from both volume and velocity changes during flow. Recommendations for using BIA in hemodynamic monitoring have been mentioned highlighting the suitable range of frequencies (1 kHz-1 MHz) as well as safety considerations for a BIA setup. Finally, current challenges in using BIA such as geometry assumption and inaccuracies have been discussed while mentioning potential advantages of a multi-frequency analysis to cover all the major contributors to blood's impedance response during flow.

Updates in Hemodynamic Monitoring: A Review for Pharmacists

Vital signs are regularly monitored in hospitalized patients. In the intensive care unit (ICU), traditional non-invasive blood pressure monitoring and telemetry may not provide enough information to determine the etiology of hemodynamic instability or guide intervention. Arterial catheters remain the gold-standard for continuous blood pressure monitoring and are commonly used in ICU patients. Pulmonary artery catheters and central venous catheters are beneficial in select patient populations and provide more advanced and specific information about a patient's hemodynamics. However, neither are benign and can increase risk of complications such as infection, arrhythmias, pneumothorax and vascular or valvular damage. In the past 10 years, the development of reliable non-invasive (NICOM), or minimally-invasive (MICOM), cardiac output monitoring devices has accelerated. The MICOM devices require an arterial catheter to obtain hemodynamic values, whereas NICOM devices do not require any arterial or venous access. These devices have emerged to be particularly useful in evaluating and managing patients with suspected mixed shock. As these devices become more prevalent, it is imperative that clinical pharmacists become familiar with interpreting this data as it may have a substantial impact on medication selection and optimization. This review will discuss the basics of NICOM and MICOM devices, limitations with these methods of monitoring, and clinical application for pharmacists.

Bioreactance Cardiac Output Trending Ability in Preterm Infants: A Single Centre, Longitudinal Study

INTRODUCTION

It is unknown whether bioreactance (BR) can accurately track cardiac output (CO) changes in preterm neonates.

METHODS

A prospective observational longitudinal study was performed in stable preterm infants (<37 weeks) during the first 72 h of life. Stroke volume (SV) and CO, as measured by BR and transthoracic echocardiography, were compared.

RESULTS

The mean gestational age (GA) was 31.3 weeks and mean birth weight (BW) was 1,563 g. Overall, 690 measurements were analysed for trending ability by 4-quadrant and polar plots. For non-weight-indexed measurements, 377 (54.6%) lay outside the 5% exclusion zone, the concordance rate was poor (77.2%) with a high mean angular bias (28.6°), wide limits of agreement and a poor angular concordance rate (17.4%). Neither GA, BW nor respiratory support mode affected trending data. Patent ductus arteriosus, postnatal age, and CO level had variable effects on trending data. Trending data for 5 and 10% exclusion zones were also compared.

CONCLUSION

The ability of BR to track changes in CO is not interchangeable with CO changes as measured by echocardiography. BR, as a trend monitor for changes in CO or SV to determine clinical decisions around interventions in neonatology, should be used with caution.

Investigating Electrical Impedance Spectroscopy for Estimating Blood Flow-Induced Variations in Human Forearm

This work aims to investigate the feasibility of employing multi-frequency bioimpedance analysis for hemodynamic assessment. Towards this, we aim to explore one of its implementations, electrical impedance spectroscopy (EIS), for estimating changes in radial artery diameter due to blood flow. Following from our previous investigations, here, we use a commercial device-the Quadra^® Impedance Spectroscopy device-for impedance measurements of the forearm of three subjects under normal conditions and occluding the artery with a cuff. This was performed simultaneously with ultrasound measurements as a reference. The impedance spectra were measured over time, yielding waveforms reflecting changes due to blood flow. Contributions from the fat/muscle domains were accounted for using the occluded impedance response, resulting in arterial impedance. A modified relationship was approximated to calculate the diameter from the arterial impedance, which showed a similarity with ultrasound measurements. Comparison with the ultrasound measurements revealed differences in phase and amplitude, primarily due to the approximated relationship between impedance and diameter and neglecting the impedance phase analysis. This work shows the potential of EIS, with improvements, towards estimating blood flow-induced variation in arteries. Further analysis and improvements could help place this technology in mainstream clinical practice for hemodynamic monitoring.

Comparison of cardiac output and cardiac index values measured by critical care echocardiography with the values measured by pulse index continuous cardiac output (PiCCO) in the pediatric intensive care unit:a preliminary study

Background

Planning optimal fluid and inotrope-vasopressor-inodilator therapy is essential in critically ill children. Pulse index Contour Cardiac Output (PiCCO) monitoring is an invasive, hemodynamic monitor that provides parameter measurements such as cardiac output (CO), cardiac index (CI). Use of ultrasonography and critical care echocardiography by the pediatric intensivists has increased in recent years. In the hands of an experienced pediatric intensivist, critical echocardiography can accurately measure both CO and CI. Our objective in this study is to compare the CO and CI values measured by pediatric intensivist using critical care echocardiography to the values measured by PiCCO monitor in critically ill pediatric patients.

Methods

A prospective observational study from a tertiary university hospital PICU. A total of 15 patients who required advanced hemodynamic monitoring and applied PiCCO monitoring were included the study. The diagnosis of patients were septic shock, cardiogenic shock, acute respiratory distress syndrome, pulmonary edema. Forty nine echocardiographic measurements were performed and from 15 patients. All echocardiographic measurements were performed by a pediatric intensive care fellow experienced in cardiac ultrasound. The distance of left ventricle outflow tract (LVOT) in the parasternal long axis and LVOT-Velocity Time Integral (LVOT-VTI) measurement was performed in the apical five chamber image. Cardiac output_echocardiography (CO_echo) and CI_echocardiography (CI_echo) were calculated using these two measurements. PiCCO (PiCCO, Pulsion Medical Systems, Munich, Germany) monitoring was performed. Cardiac output (CO_picco) and CI (CI_picco) were simultaneously measured by PiCCO monitor and echocardiography. We performed a correlation analysis with this 49 echocardiographic measurements and PiCCO measurements.

Results

We detected a strong positive correlation between CO_echo and CO_picco measurements (p < 0.001, r = 0.985) and a strong positive correlation between CI_echo and CI_picco measurements (p < 0.001, r = 0.943).

Conclusions

Our study results suggest that critical care echocardiography measurement of CO and CI performed by an experienced pediatric intensivist are comparable to PiCCO measurements. The critical care echocardiography measurement can be used to guide fluid and vasoactive-inotropic management of critically ill pediatric patients.

Near-Infrared Spectroscopy in Adult Circulatory Shock: A Systematic Review

BACKGROUND

Circulatory shock affects every third patient in intensive care units and is associated with high mortality. Near-infrared spectroscopy (NIRS) could serve as a means for monitoring tissue perfusion in circulatory shock.

PURPOSE

To assess the evidence of NIRS monitoring in circulatory shock, we conducted a systematic review of the literature.

METHODS

The study protocol was registered in International Prospective Register of Systematic Reviews (PROSPERO). We searched PubMed, Ovid MEDLINE, Scopus, and EBM Reviews databases. The reference lists of included articles, last volumes of key journals, and NIRS monitor manufacturers' webpages were searched manually. Two reviewers independently selected included studies. The quality of studies was assessed. The qualitative synthesis was guided by 3 questions: First, does NIRS monitoring improve patient-centered outcomes in adult circulatory shock patient? Second, do NIRS-derived parameters predict patient-centered outcomes, such as mortality and organ dysfunction, and third, does NIRS monitoring give additional information to guide treatment decisions?

MAIN RESULTS

Eighteen observational studies with 927 patients were included. Because of considerable clinical heterogeneity of the data, we were not able to perform a meta-analysis. Also, due to lack of randomized controlled trials, the first review question could not be answered. Based on the current review, baseline tissue oxygen saturation (StO2) however seems to predict mortality and identify patients with most severe forms of circulatory shock.

CONCLUSIONS

Near-infrared spectroscopy-derived StO2 can predict mortality in circulatory shock, but high-quality data on the impact of NIRS monitoring are lacking. Furthermore, the marked heterogeneity of the studies makes combining the results of individual studies difficult. Standardization of methodology and clinical randomized trials are needed before wider clinical use.

Are management decisions in critical patients changed with use of hemodynamic parameters from transpulmonary thermodilution technique?

Background

The assessment of hemodynamic variables is a mainstay in the management of critically ill patients. Hemodynamic variables may help physicians to choose among use of a vasopressor, an inotropic agent, or discontinuation of drugs. In this study, we aimed to investigate the usefulness of advanced hemodynamic variables in clinical decision-making.

Methods

Surveys regarding the case were administered to 25 surgeons working in nationally designated trauma centers or on trauma teams, using a voting system at a medical conference. The patient was a 67-year-old male with a crush injury of the left leg after a pedestrian traffic accident, who had aggravated pulmonary edema after leg amputation. Three clinical situations were given and the decision choices were: immediately after amputation, in 8 hours, and on the second day after amputation. Three kinds of variables from hemodynamic monitoring systems were provided for each clinical situation: conventional hemodynamic variables, including central venous pressure; variables from pulse contour analysis (PCA) [cardiac output (CO), stroke volume index, stroke volume variation (SVV), and systemic vascular resistance index); and variables from transpulmonary thermodilution (TPTD) technique (global ejection fraction and extravascular lung water index). The changes in decisions according to each provided hemodynamic variable were investigated and analyzed.

Results

The advanced hemodynamic parameters were considered to have a decisive effect on choosing vasopressors and inotropic agents. The decision was changed in 88% (22/25) of physicians using variables from the advanced monitoring systems. Among them, 82% (18/22) of physicians chose hemodynamic variables from the TPTD technique as their reason for change regarding management of a patient with severe pulmonary edema.

Conclusions

Advanced monitoring systems might be helpful in decision-making for critically ill patients. Multiple parameters and trends in change could be more important than a single value. Clinicians should select the system most appropriate according to its advantages and limitations, and interpret the variables obtained correctly.

Autonomic nervous system monitoring in intensive care as a prognostic tool. Systematic review

Objective

To present a systematic review of the use of autonomic nervous system monitoring as a prognostic tool in intensive care units by assessing heart rate variability.

Methods

Literature review of studies published until July 2016 listed in PubMed/Medline and conducted in intensive care units, on autonomic nervous system monitoring, via analysis of heart rate variability as a prognostic tool (mortality study). The following English terms were entered in the search field: ("autonomic nervous system" OR "heart rate variability") AND ("intensive care" OR "critical care" OR "emergency care" OR "ICU") AND ("prognosis" OR "prognoses" OR "mortality").

Results

There was an increased likelihood of death in patients who had a decrease in heart rate variability as analyzed via heart rate variance, cardiac uncoupling, heart rate volatility, integer heart rate variability, standard deviation of NN intervals, root mean square of successive differences, total power, low frequency, very low frequency, low frequency/high frequency ratio, ratio of short-term to long-term fractal exponents, Shannon entropy, multiscale entropy and approximate entropy.

Conclusion

In patients admitted to intensive care units, regardless of the pathology, heart rate variability varies inversely with clinical severity and prognosis.

Impedance cardiography as tool for continuous hemodynamic monitoring during cesarean section: randomized, prospective double blind study

BACKGROUND

Impedance Cardiography (ICG) is a non-invasive tool for continuous hemodynamic monitoring. Aims of our study were to assess the utility of ICG to evaluate the hemodynamic impact of 6 mg (GL6) vs 8 mg (GL8) levobupivacaine combined with fentanyl in healthy patients undergoing elective cesarean section; secondary, to compare the duration and quality of analgesia and anesthesia.

METHODS

Sixty-two women receiving combined spinal-epidural (CSE) for elective cesarean delivery were randomly allocated to GL6 or GL8 groups. Mean arterial pressure (MAP), cardiac index (CI), systemic vascular resistance index (SVRI), heart rate (HR), stroke volume index (SVI) were recorded from Tbaseline to 31 min after CSE by ICG. Sensory and motor blocks, patients and surgeons satisfaction, neonatal data were also recorded.

RESULTS

Fifteen of 32 patients in GL6 and 15 of 30 patients in GL8 experienced hypotension at T2 vs Tbaseline (P < .001) and SVRI reduction (P = .035 and P < .001 respectively). MAP, CI and SVRI were always slightly higher in GL6 vs GL8. HR and SVI remained stable until the end of surgery in all patients. Total ephedrine requirements was higher in GL8 (P = .010). The onset and offset time of sensory and motor block were similar in both groups, but the number of patients with motor block was lower in GL6 vs GL8 (P = .001). Patients and surgeon satisfaction scores, the number of patients needed systemic rescue doses, neonatal data were similar in both groups.

CONCLUSIONS

ICG is a useful noninvasive tool to monitor continuously hemodynamics during cesarean section. The hemodynamic stability, the satisfying sensory block and rapid mobilization provided by low levobupivacaine dose may be particularly advantageous in obstetric patients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03170427 . Retrospectively Registered (Date of registration: May 2017).

Propranolol Reduces Cardiac Index But does not Adversely Affect Peripheral Perfusion in Severely Burned Children

PURPOSE

The aim of this study was to quantify the effect of propranolol on hemodynamic parameters assessed using the PiCCO system in burned children.

METHODS

We analyzed hemodynamic data from patients who were randomized to receive either propranolol (4 mg/kg/day) or placebo (control), which was initiated as a prospective randomized controlled trial. Endpoints were cardiac index (CI), percent predicted heart rate (%HR), mean arterial pressure (MAP), percent predicted stroke volume (%SV), rate pressure product (RPP), cardiac work (CW), systemic vascular resistance index (SVRI), extravascular lung water index (EVLWI), arterial blood gases, events of lactic acidosis, and mortality. Mixed multiple linear regressions were applied, and a 95% level of confidence was assumed.

RESULTS

One hundred twenty-one burned children (control: n = 62, propranolol: n = 59) were analyzed. Groups were comparable in demographics, EVLWI, SVRI, %SV, arterial blood gases, Denver 2 postinjury organ failure score, incidence of lactic acidosis, or mortality. Percent predicted HR, MAP, CI, CW, and RPP were significantly reduced in the propranolol-treated group (P <0.01).

CONCLUSIONS

Propranolol significantly reduces cardiogenic stress by reducing CI and MAP in children with severe burn injury. However, peripheral oxygen delivery was not reduced and events of lactic acidosis as well as organ dysfunction was not higher in propranolol treated patients.

Transpulmonary Thermodilution Versus Transthoracic Echocardiography for Cardiac Output Measurements in Severely Burned Children

INTRODUCTION

Severe burns trigger a hyperdynamic state, necessitating accurate measurement of cardiac output (CO) for cardiovascular observation and guiding fluid resuscitation. However, it is unknown whether, in burned children, the increasingly popular transthoracic echocardiography (TTE) method of CO measurement is as accurate as the widely used transpulmonary thermodilution (TPTD) method.

PATIENTS AND METHODS

We retrospectively compared near-simultaneously performed CO measurements in severely burned children using TPTD with the Pulse index Continuous Cardiac Output (PiCCO) system or TTE. Outcomes were compared using t tests, multiple linear regression, and a Bland-Altman plot.

RESULTS

Fifty-four children (9 ± 5 years) with 68 ± 18% total body surface area burns were studied. An analysis of 105 data pairs revealed that PiCCO yielded higher CO measurements than TTE (190 ± 39% vs. 150 ± 50% predicted values; P < 0.01). PiCCO- and TTE-derived CO measurements correlated moderately well (R = 0.54, P < 0.01). A Bland-Altman plot showed a mean bias of 1.53 L/min with a 95% prediction interval of 4.31 L/min.

CONCLUSIONS

TTE-derived estimates of CO may underestimate severity of the hyperdynamic state in severely burned children. We propose using the PiCCO system for objective cardiovascular monitoring and to guide goal-directed fluid resuscitation in this population.

Accuracy, Precision, and Trending of 4 Pulse Wave Analysis Techniques in the Postoperative Period

OBJECTIVE

The aim of this study was to analyze the accuracy, precision, and trending ability of the following 4 pulse wave analysis devices to measure continuous cardiac output: PiCCO₂ ([PCCO]; Pulsion Medical System, Munich, Germany); LiDCO_Rapid ([LCCO]; LiDCO Ltd, London, UK); FloTrac/Vigileo ([FCCO]; Edwards Lifesciences, Irvine, CA); and Nexfin ([NCCO]; BMEYE, Amsterdam, The Netherlands).

DESIGN

Prospective, observational clinical study.

SETTING

Intensive care unit of a single-center, teaching hospital.

PARTICIPANTS

The study comprised 22 adult patients after elective coronary artery bypass surgery.

INTERVENTIONS

Three measurement cycles were performed in all patient durings their immediate postoperative intensive care stay before and after fluid loading. Hemodynamic measurements were performed 5 minutes before and immediately after the administration of 500 mL colloidal fluid over 20 minutes.

MEASUREMENTS AND MAIN RESULTS

PCCO, LCCO, FCCO, and NCCO were assessed and compared with cardiac output derived from intermittent transpulmonary thermodilution (ICO). One hundred thirty-two matched sets of data were available for analysis. Bland-Altman analysis using linear mixed effects models with random effects for patient and trial revealed a mean bias ±2 standard deviation (%error) of -0.86 ± 1.41 L/min (34.9%) for PCCO-ICO, -0.26 ± 2.81 L/min (46.3%) for LCCO-ICO, -0.28 ± 2.39 L/min (43.7%) for FCCO-ICO, and -0.93 ± 2.25 L/min (34.6%) for NCCO-ICO. Bland-Altman plots without adjustment for repeated measurements and replicates yielded considerably larger limits of agreement. Trend analysis for all techniques did not meet criteria for acceptable performance.

CONCLUSIONS

All 4 tested devices using pulse wave analysis for measuring cardiac output failed to meet current criteria for meaningful and adequate accuracy, precision, and trending ability in cardiac output monitoring.

A review of hemodynamic monitoring techniques, methods and devices for the emergency physician

The emergency department (ED) is frequently the doorway to the intensive care unit (ICU) for a significant number of critically ill patients presenting to the hospital. Hemodynamic monitoring (HDM) which is a key component in the effective management of the critically ill patient presenting to the ED, is primarily concerned with assessing the performance of the cardiovascular system and determining the correct therapeutic intervention to optimise end-organ oxygen delivery. The spectrum of hemodynamic monitoring ranges from simple clinical assessment and routine bedside monitoring to point of care ultrasonography and various invasive monitoring devices. The clinician must be aware of the range of available techniques, methods, interventions and technological advances as well as possess a sound approach to basic hemodynamic monitoring prior to selecting the optimal modality. This article comprises an in depth discussion of an approach to hemodynamic monitoring techniques and principles as well as methods of predicting fluid responsiveness as it applies to the ED clinician. We review the role, applicability and validity of various methods and techniques that include; clinical assessment, passive leg raising, blood pressure, finger based monitoring devices, the mini-fluid challenge, the end-expiratory occlusion test, central venous pressure monitoring, the pulmonary artery catheter, ultrasonography, bioreactance and other modern invasive hemodynamic monitoring devices.

A modified breathing pattern improves the performance of a continuous capnodynamic method for estimation of effective pulmonary blood flow

In a previous study a new capnodynamic method for estimation of effective pulmonary blood flow (CO_EPBF) presented a good trending ability but a poor agreement with a reference cardiac output (CO) measurement at high levels of PEEP. In this study we aimed at evaluating the agreement and trending ability of a modified CO_EPBF algorithm that uses expiratory instead of inspiratory holds during CO and ventilatory manipulations. CO_EPBF was evaluated in a porcine model at different PEEP levels, tidal volumes and CO manipulations (N = 8). An ultrasonic flow probe placed around the pulmonary trunk was used for CO measurement. We tested the CO_EPBF algorithm using a modified breathing pattern that introduces cyclic end-expiratory time pauses. The subsequent changes in mean alveolar fraction of carbon dioxide were integrated into a capnodynamic equation and effective pulmonary blood flow, i.e. non-shunted CO, was calculated continuously breath by breath. The overall agreement between CO_EPBF and the reference method during all interventions was good with bias (limits of agreement) 0.05 (-1.1 to 1.2) L/min and percentage error of 36 %. The overall trending ability as assessed by the four-quadrant and the polar plot methodology was high with a concordance rate of 93 and 94 % respectively. The mean polar angle was 0.4 (95 % CI -3.7 to 4.5)°. A ventilatory pattern recurrently introducing end-expiratory pauses maintains a good agreement between CO_EPBF and the reference CO method while preserving its trending ability during CO and ventilatory alterations.

Anesthetic management of a patient with giant retroperitoneal liposarcoma: case report with literature review

Patients with giant retroperitoneal liposarcomas are considered at great risks of perioperative complications and require meticulous anaesthetic management. There have been few reports about anaesthetic management of giant retroperitoneal liposarcoma. We present the case of a 66-year-old patient who suffered from a giant retroperitoneal liposarcoma (diameter 45 cm and weigh 4.5 kg), needing a resection surgery under general anesthesia. We successfully managed anesthesia procedures in this patient using FloTrac/Vigileo(TM) monitoring system without major perioperative complications. The surgery was completed uneventfully and the patient recovered smoothly. After reviewing the literature, we summarize FloTrac/Vigileo(TM) monitoring system is useful to help anaesthesiologists adjust infusion rate to maintain the stability of circulatory state. Anesthetic monitoring, fluid management and temperature control need to be focused in the anesthetic management.

Perioperative fluid guidance with transthoracic echocardiography and pulse-contour device in morbidly obese patients

BACKGROUND

In bariatric surgery, non- or mini-invasive modalities for cardiovascular monitoring are addressed to meet individual variability in hydration needs. The aim of the study was to compare conventional monitoring to an individualized goal-directed therapy (IGDT) regarding the need of perioperative fluids and cardiovascular stability.

METHODS

Fifty morbidly obese patients were consecutively scheduled for laparoscopic bariatric surgery (ClinicalTrials.gov Identifier: NCT01873183). The intervention group (IG, n=30) was investigated preoperatively with transthoracic echocardiography (TTE) and rehydrated with colloid fluids if a low level of venous return was detected. During surgery, IGDT was continued with a pulse-contour device (FloTrac™). In the control group (CG, n=20), conventional monitoring was conducted. The type and amount of perioperative fluids infused, vasoactive/inotropic drugs administered, and blood pressure levels were registered.

RESULTS

In the IG, 213 ± 204 mL colloid fluids were administered as preoperative rehydration vs. no preoperative fluids in the CG (p<0.001). During surgery, there was no difference in the fluids administered between the groups. Mean arterial blood pressures were higher in the IG vs. the CG both after induction of anesthesia and during surgery (p=0.001 and p=0.001).

CONCLUSIONS

In morbidly obese patients suspected of being hypovolemic, increased cardiovascular stability may be reached by preoperative rehydration. The management of rehydration should be individualized. Additional invasive monitoring does not appear to have any effect on outcomes in obesity surgery.

Stroke volume variation to guide fluid therapy: is it suitable for high-risk surgical patients? A terminated randomized controlled trial

Background

Perioperative goal-directed fluid therapy (GDFT) may improve outcome after high-risk surgery. Minimal invasive measurement of stroke volume variation (SVV) has been recommended to guide fluid therapy. We intended to study how perioperative GDFT with arterial-based continuous SVV monitoring influences postoperative complications in a high-risk surgical population.

Methods

From February 1st 2012, all ASA 3 and 4 patients undergoing abdominal surgery in two university hospitals were assessed for randomization into a control group or GDFT group. An arterial-line cardiac output monitor was used to measure SVV, and fluid was given after an algorithm in the intervention group. Restrictions of the method excluded patients undergoing laparoscopic surgery, patients with atrial fibrillation and patients with severe mitral/aortal stenosis. To detect a decrease in number of complication from 40 % in the control group to 20 % in the GDFT group, n = 164 patients were needed (power 80 %, alpha 0.05, two-sided test). To include the needed amount of patients, the study was estimated to last for 2 years.

Results

After 1 year, 30 patients were included and the study was halted due to slow inclusion rate. Of 732 high-risk patients scheduled for abdominal surgery, 391 were screened for randomization. Of those, n = 249 (64 %) were excluded because a laparoscopic technique was preferred and n = 95 (24 %) due to atrial fibrillation.

Conclusions

Our study was stopped due to a slow inclusion rate. Methodological restrictions of the arterial-line cardiac output monitor excluded the majority of patients. This leaves the question if this method is appropriate to guide fluid therapy in high-risk surgical patients.

Trial registration

ClinicalTrials.gov: NCT01473446.

Electronic supplementary material

The online version of this article (doi:10.1186/s13741-015-0016-x) contains supplementary material, which is available to authorized users.

Assessing volume status

Shock is a physiologic state associated with high morbidity and mortality rates. The clinician has several tools available to evaluate volume status. Each modality has its benefits and limitations but, to date, no one test can indicate with 100% accuracy which patients will be truly volume responsive. Although the search for the Holy Grail of a perfect intravascular monitor continues, we must remember the importance of early, aggressive, and goal-directed interventions for patients in shock. Finally, there is no substitute for the most important intervention-the frequent presence of the physician at the patient's bedside.

Therapeutic strategies for high-dose vasopressor-dependent shock

There is no consensual definition of refractory shock. The use of more than 0.5 mcg/kg/min of norepinephrine or epinephrine to maintain target blood pressure is often used in clinical trials as a threshold. Nearly 6% of critically ill patients will develop refractory shock, which accounts for 18% of deaths in intensive care unit. Mortality rates are usually greater than 50%. The assessment of fluid responsiveness and cardiac function can help to guide therapy, and inotropes may be used if hypoperfusion signs persist after initial resuscitation. Arginine vasopressin is frequently used in refractory shock, although definite evidence to support this practice is still missing. Its associations with corticosteroids improved outcome in observational studies and are therefore promising alternatives. Other rescue therapies such as terlipressin, methylene blue, and high-volume isovolemic hemofiltration await more evidence before use in routine practice.