Transesophageal Doppler reliably tracks changes in cardiac output in comparison with intermittent pulmonary artery thermodilution in cardiac surgery patients

Prediction of Fluid Responsiveness by the Effect of the Lung Recruitment Maneuver on the Perfusion Index in Mechanically Ventilated Patients During Surgery

Introduction

Excessive or inadequate fluid administration during perioperative period affects outcomes. Adjustment of volume expansion (VE) by performing fluid responsiveness (FR) test plays an important role in optimizing fluid infusion. Since changes in stroke volume (SV) during lung recruitment maneuver (LRM) can predict FR, and peripheral perfusion index (PI) is related to SV; therefore, we hypothesized that the changes in PI during LRM (ΔPILRM) could predict FR during perioperative period.

Methods

Patients who were scheduled for elective non-laparoscopic surgery under general anesthesia with a mechanical ventilator and who required VE (250 mL of crystalloid solution infusion over 10 min) were included. Before VE, LRM was performed by a continuous positive airway pressure of 30 cm H2O for 30 sec; hemodynamic variables with their changes (PI, obtained by pulse oximetry; and ΔPILRM, calculated by using [(PI before LRM—PI after LRM)/PI before LRM]*100) were obtained before and after LRM. After SV (measured by esophageal doppler) and PI had returned to the baseline values, VE was infused, and the values of these variables were recorded again, before and after VE. Fluid responders (Fluid-Res) were defined by an increase in SV ≥10% after VE. Receiver operating characteristic curves of the baseline values and ΔPILRM were constructed and reported as areas under the curve (AUC) with 95% confidence intervals, to predict FR.

Results

Of 32 mechanically ventilated adult patients included, 13 (41%) were in the Fluid-Res group. Before VE and LRM, there were no differences in the mean arterial pressure (MAP), heart rate, SV, and PI between patients in the Fluid-Res and fluid non-responders (Fluid-NonRes) groups. After LRM, SV, MAP, and, PI decreased in both groups, ΔPILRM was greater in the Fluid-Res group than in Fluid-NonRes group (55.2 ± 17.8% vs. 35.3 ± 17.3%, p < 0.001, respectively). After VE, only SV and cardiac index increased in the Fluid-Res group. ΔPILRM had the highest AUC [0.81 (0.66–0.97)] to predict FR with a cut-off value of 40% (sensitivity 92.3%, specificity 73.7%).

Conclusions

ΔPILRM can be applied to predict FR in mechanical ventilated patients during the perioperative period.

Estimation of cardiac output variations induced by hemodynamic interventions using multi-beat analysis of arterial waveform: a comparative off-line study with transesophageal Doppler method during non-cardiac surgery

Multi-beat analysis (MBA) of the radial arterial pressure (AP) waveform is a new method that may improve cardiac output (CO) estimation via modelling of the confounding arterial wave reflection. We evaluated the precision and accuracy using the trending ability of the MBA method to estimate absolute CO and variations (ΔCO) during hemodynamic challenges. We reviewed the hemodynamic challenges (fluid challenge or vasopressors) performed when intra-operative hypotension occurred during non-cardiac surgery. The CO was calculated offline using transesophageal Doppler (TED) waveform (COTED) or via application of the MBA algorithm onto the AP waveform (COMBA) before and after hemodynamic challenges. We evaluated the precision and the accuracy according to the Bland & Altman method. We also assessed the trending ability of the MBA by evaluating the percentage of concordance with 15% exclusion zone between ΔCOMBA and ΔCOTED. A non-inferiority margin was set at 87.5%. Among the 58 patients included, 23 (40%) received at least 1 fluid challenge, and 46 (81%) received at least 1 bolus of vasopressors. Before treatment, the COTED was 5.3 (IQR [4.1-8.1]) l min-1, and the COMBA was 4.1 (IQR [3-5.4]) l min-1. The agreement between COTED and COMBA was poor with a 70% percentage error. The bias and lower and upper limits of agreement between COTED and COMBA were 0.9 (CI95 = 0.82 to 1.07) l min-1, -2.8 (CI95 = -2.71 to-2.96) l min-1 and 4.7 (CI95 = 4.61 to 4.86) l min-1, respectively. After hemodynamic challenge, the percentage of concordance (PC) with 15% exclusion zone for ΔCO was 93 (CI97.5 = 90 to 97)%. In this retrospective offline analysis, the accuracy, limits of agreements and percentage error between TED and MBA for the absolute estimation of CO were poor, but the MBA could adequately track induced CO variations measured by TED. The MBA needs further evaluation in prospective studies to confirm those results in clinical practice conditions.

Clinical Application of the Fluid Challenge Approach in Goal-Directed Fluid Therapy: What Can We Learn From Human Studies?

Resuscitative fluid therapy aims to increase stroke volume (SV) and cardiac output (CO) and restore/improve tissue oxygen delivery in patients with circulatory failure. In individualized goal-directed fluid therapy (GDFT), fluids are titrated based on the assessment of responsiveness status (i.e., the ability of an individual to increase SV and CO in response to volume expansion). Fluid administration may increase venous return, SV and CO, but these effects may not be predictable in the clinical setting. The fluid challenge (FC) approach, which consists on the intravenous administration of small aliquots of fluids, over a relatively short period of time, to test if a patient has a preload reserve (i.e., the relative position on the Frank-Starling curve), has been used to guide fluid administration in critically ill humans. In responders to volume expansion (defined as individuals where SV or CO increases ≥10–15% from pre FC values), FC administration is repeated until the individual no longer presents a preload reserve (i.e., until increases in SV or CO are <10–15% from values preceding each FC) or until other signs of shock are resolved (e.g., hypotension). Even with the most recent technological developments, reliable and practical measurement of the response variable (SV or CO changes induced by a FC) has posed a challenge in GDFT. Among the methods used to evaluate fluid responsiveness in the human medical field, measurement of aortic flow velocity time integral by point-of-care echocardiography has been implemented as a surrogate of SV changes induced by a FC and seems a promising non-invasive tool to guide FC administration in animals with signs of circulatory failure. This narrative review discusses the development of GDFT based on the FC approach and the response variables used to assess fluid responsiveness status in humans and animals, aiming to open new perspectives on the application of this concept to the veterinary field.

Evaluation of the ability of haemodynamic variables obtained with minimally invasive techniques to assess fluid responsiveness in endotoxaemic Beagles

OBJECTIVE

To examine the ability of different haemodynamic variables recorded by minimally invasive monitoring techniques to assess fluid responsiveness (FR) in endotoxaemic Beagles.

STUDY DESIGN

Prospective terminal experimental study.

ANIMALS

A group of six healthy, purpose-bred Beagle dogs (three intact females and males), age 5-9.8 years (range) and weighing 11.4-17.9 kg.

METHODS

Endotoxaemic shock was induced by injecting 1 mg kg^-1Escherichia coli lipopolysaccharide (LPS) intravenously in six sevoflurane-anaesthetized mechanically ventilated Beagles for another project. After 10 minutes, three Ringer's acetate boluses (10 mL kg^-1) were administered each over 10 minutes with collection of haemodynamic data immediately before and after each bolus. Thereafter, arterial hypotension was treated with noradrenaline ± dexmedetomidine until arterial pressures increased to a target value. After a wash-out period of 20 minutes another three boluses of fluid were administered and measurements were repeated equally. For each fluid bolus, FR was considered positive when change (Δ) in stroke volume measured by pulmonary artery thermodilution was ≥15%. To test predictive accuracy for FR, we recorded heart rate, invasive arterial, right atrial and pulmonary capillary wedge pressures, pulse wave transit time with haemodynamic monitors, calculated pulse pressure, shock index and rate over pressure evaluation (ROPE) and measured stroke distance and corrected flow time (FTc) with oesophageal Doppler monitoring.

RESULTS

A total of 35 measurements (19 positive and 16 negative responses) were evaluated. A FTc < 330 ms, Δ pulse pressure ≥20%, Δ shock index ≤-14% and ΔROPE ≤-17% were the most significant indicators of positive FR with an area under the receiver operating characteristics curve between 0.72 and 0.74.

CONCLUSIONS AND CLINICAL RELEVANCE

In endotoxaemic Beagles, none of the assessed haemodynamic variables could predict FR with high sensitivity and specificity.

Intraoperative management and hemodynamic monitoring for ma- jor abdominal surgery : a narrative review

Background : Several trials suggest that postoperative outcomes may be improved by the use of hemodynamic monitoring, but a survey by the American Society of Anesthesiologists (ASA) and the European Society of Anaesthesiology (ESA) showed that cardiac output is monitored by only 34% of ASA and ESA respondents and central venous pressure is monitored by 73% of ASA respondents and 84% of ESA respondents. Moreover, 86.5% of ASA respondents and 98.1% of ESA respondents believe that their current hemodynamic management could be improved (1). The interaction of general anesthesia and surgical stress is the main problem and the leading cause for postoperative morbidity and mortality. The choice of a suitable hemodynamic monitoring system for patients at high anesthesiological risk is of crucial importance to reduce the incidence of major postoperative complications. The aim of the present review is to summarize the benefits of a defined path beginning before surgery, and discuss the available evidence supporting the efficacy and safety of an individualized hemodynamic approach for major abdominal surgery. Objective : To evaluate the clinical effectiveness of a perioperative hemodynamic therapy algorithm in high risk patients

A novel method of trans-esophageal Doppler cardiac output monitoring utilizing peripheral arterial pulse contour with/without machine learning approach

Transesophageal Doppler (TED) velocity in the descending thoracic aorta (DA) is used to track changes in cardiac output (CO). However, CO tracking by this method is hampered by substantial change in aortic cross-sectional area (CSA) or proportionality between blood flow to the upper and lower body. To overcome this, we have developed a new method of TED CO monitoring. In this method, TED signal is obtained primarily from the aortic arch (AA). Using AA velocity signal, CO (CO_AA-CSA) is estimated by compensating changes in the aortic CSA with peripheral arterial pulse contour. When AA cannot be displayed properly or when the quality of AA velocity signal is unacceptable, our method estimates CO (CO_DA-ML) from DA velocity signal first by compensating changes in the aortic CSA, and by compensating changes in the blood flow proportionality through a machine learning of the relation between the CSA-adjusted CO and a reference CO (CO_ref). In 12 anesthetized dogs, we compared CO_AA-CSA and CO_DA-ML with CO_ref measured by an ascending aortic flow probe under diverse hemodynamic conditions (CO_ref changed from 723 to 7316 ml·min^-1). Between CO_AA-CSA and CO_ref, concordance rate in the four-quadrant plot analysis was 96%, while angular concordance rate in the polar plot analysis was 91%. Between CO_DA-ML and CO_ref, concordance rate was 93% and angular concordance rate was 94%. Both CO_AA-CSA and CO_DA-ML demonstrated "good to marginal" tracking ability of CO_ref. In conclusion, our method may allow a robust and reliable tracking of CO during perioperative hemodynamic management.

Volumetric and End-Tidal Capnography for the Detection of Cardiac Output Changes in Mechanically Ventilated Patients Early after Open Heart Surgery

Background

Exhaled carbon dioxide (CO₂) reflects cardiac output (CO) provided stable ventilation and metabolism. Detecting CO changes may help distinguish hypovolemia or cardiac dysfunction from other causes of haemodynamic instability. We investigated whether CO₂ measured as end-tidal concentration (EtCO₂) and eliminated volume per breath (VtCO₂) reflect sudden changes in cardiac output (CO).

Methods

We measured changes in CO, VtCO₂, and EtCO₂ during right ventricular pacing and passive leg raise in 33 ventilated patients after open heart surgery. CO was measured with oesophageal Doppler.

Results

During right ventricular pacing, CO was reduced by 21% (CI 18–24; p < 0.001), VtCO₂ by 11% (CI 7.9–13; p < 0.001), and EtCO₂ by 4.9% (CI 3.6–6.1; p < 0.001). During passive leg raise, CO increased by 21% (CI 17–24; p < 0.001), VtCO₂ by 10% (CI 7.8–12; p < 0.001), and EtCO₂ by 4.2% (CI 3.2–5.1; p < 0.001). Changes in VtCO₂ were significantly larger than changes in EtCO₂ (ventricular pacing: 11% vs. 4.9% (p < 0.001); passive leg raise: 10% vs. 4.2% (p < 0.001)). Relative changes in CO correlated with changes in VtCO₂ (ρ=0.53; p=0.002) and EtCO₂ (ρ=0.47; p=0.006) only during reductions in CO. When dichotomising CO changes at 15%, only EtCO₂ detected a CO change as judged by area under the receiver operating characteristic curve.

Conclusion

VtCO₂ and EtCO₂ reflected reductions in cardiac output, although correlations were modest. The changes in VtCO₂ were larger than the changes in EtCO₂, but only EtCO₂ detected CO reduction as judged by receiver operating characteristic curves. The predictive ability of EtCO₂ in this setting was fair. This trial is registered with NCT02070861.

Accuracy and precision of non-invasive cardiac output monitoring by electrical cardiometry: a systematic review and meta-analysis

Cardiac output monitoring is used in critically ill and high-risk surgical patients. Intermittent pulmonary artery thermodilution and transpulmonary thermodilution, considered the gold standard, are invasive and linked to complications. Therefore, many non-invasive cardiac output devices have been developed and studied. One of those is electrical cardiometry. The results of validation studies are conflicting, which emphasize the need for definitive validation of accuracy and precision. We performed a database search of PubMed, Embase, Web of Science and the Cochrane Library of Clinical Trials to identify studies comparing cardiac output measurement by electrical cardiometry and a reference method. Pooled bias, limits of agreement (LoA) and mean percentage error (MPE) were calculated using a random-effects model. A pooled MPE of less than 30% was considered clinically acceptable. A total of 13 studies in adults (620 patients) and 11 studies in pediatrics (603 patients) were included. For adults, pooled bias was 0.03 L min^-1 [95% CI - 0.23; 0.29], LoA - 2.78 to 2.84 L min^-1 and MPE 48.0%. For pediatrics, pooled bias was - 0.02 L min^-1 [95% CI - 0.09; 0.05], LoA - 1.22 to 1.18 L min^-1 and MPE 42.0%. Inter-study heterogeneity was high for both adults (I² = 93%, p < 0.0001) and pediatrics (I² = 86%, p < 0.0001). Despite the low bias for both adults and pediatrics, the MPE was not clinically acceptable. Electrical cardiometry cannot replace thermodilution and transthoracic echocardiography for the measurement of absolute cardiac output values. Future research should explore it's clinical use and indications.

Noninvasive cardiac output monitoring in a porcine model using the inspired sinewave technique: a proof-of-concept study

Background

Cardiac output (Q˙) monitoring can support the management of high-risk surgical patients, but the pulmonary artery catheterisation required by the current ‘gold standard’—bolus thermodilution (Q˙T)—has the potential to cause life-threatening complications. We present a novel noninvasive and fully automated method that uses the inspired sinewave technique to continuously monitor cardiac output (Q˙IST).

Methods

Over successive breaths the inspired nitrous oxide (N₂O) concentration was forced to oscillate sinusoidally with a fixed mean (4%), amplitude (3%), and period (60 s). Q˙IST was determined in a single-compartment tidal ventilation lung model that used the resulting amplitude/phase of the expired N₂O sinewave. The agreement and trending ability of Q˙IST were compared with Q˙T during pharmacologically induced haemodynamic changes, before and after repeated lung lavages, in eight anaesthetised pigs.

Results

Before lung lavage, changes in Q˙IST and Q˙T from baseline had a mean bias of –0.52 L min⁻¹ (95% confidence interval [CI], –0.41 to –0.63). The concordance between Q˙IST and Q˙T was 92.5% as assessed by four-quadrant analysis, and polar plot analysis revealed a mean angular bias of 5.98° (95% CI, –24.4°–36.3°). After lung lavage, concordance was slightly reduced (89.4%), and the mean angular bias widened to 21.8° (–4.2°, 47.6°). Impaired trending ability correlated with shunt fraction (r=0.79, P<0.05).

Conclusions

The inspired sinewave technique provides continuous and noninvasive monitoring of cardiac output, with a ‘marginal–good’ trending ability compared with cardiac output based on thermodilution. However, the trending ability can be reduced with increasing shunt fraction, such as in acute lung injury.

Minimally invasive cardiac output technologies in the ICU: putting it all together

PURPOSE OF REVIEW

Haemodynamic monitoring is a cornerstone in the diagnosis and evaluation of treatment in critically ill patients in circulatory distress. The interest in using minimally invasive cardiac output monitors is growing. The purpose of this review is to discuss the currently available devices to provide an overview of their validation studies in order to answer the question whether these devices are ready for implementation in clinical practice.

RECENT FINDINGS

Current evidence shows that minimally invasive cardiac output monitoring devices are not yet interchangeable with (trans)pulmonary thermodilution in measuring cardiac output. However, validation studies are generally single centre, are based on small sample sizes in heterogeneous groups, and differ in the statistical methods used.

SUMMARY

Minimally and noninvasive monitoring devices may not be sufficiently accurate to replace (trans)pulmonary thermodilution in estimating cardiac output. The current paradigm shift to explore trending ability rather than investigating agreement of absolute values alone is to be applauded. Future research should focus on the effectiveness of these devices in the context of (functional) haemodynamic monitoring before adoption into clinical practice can be recommended.

Journal of Clinical Monitoring and Computing 2017 end of year summary: cardiovascular and hemodynamic monitoring

Hemodynamic monitoring provides the basis for the optimization of cardiovascular dynamics in intensive care medicine and anesthesiology. The Journal of Clinical Monitoring and Computing (JCMC) is an ideal platform to publish research related to hemodynamic monitoring technologies, cardiovascular (patho)physiology, and hemodynamic treatment strategies. In this review, we discuss selected papers published on cardiovascular and hemodynamic monitoring in the JCMC in 2017.

Comparison of stroke volume measurements during hemodialysis using bioimpedance cardiography and echocardiography

BACKGROUND

Fluid management remains a major challenge of hemodialysis (HD) care, with serious implications for morbidity and mortality. Intradialytic fluid management is typically guided by blood pressure, an indirect resultant of hemodynamics status. Direct measurements of hemodynamic parameters may improve cardiovascular outcomes by providing rational bases for intervention. We compare stroke volume (SV) measurements using a noninvasive, regional biompedance cardiography device (NiCaS) with Doppler echocardiography (Echo) in HD setting.

METHODS

Stroke volumes were simultaneously measured using the devices in 17 patients receiving maintenance HD. Measurements were made during 2 weekly HD treatments, and twice within each HD treatment during the first and last hour of each treatment, for a total of 64 SV measurements. Agreement between devices was assessed using linear regression, a Pearson's correlation coefficient, and a Bland-Altman plot all adjusted for repeated measures within patients.

RESULTS

Echo and NiCaS SV mean and 95% CIs were 58.0 (50.1, 65.8) and 56.7 (49.4, 64.0) mL, respectively. NiCaS SV correlated strongly with Echo SV during the first and last hours of treatments (r = 0.93, P < 0.001 and r = 0.92, P < 0.001, respectively). Linear regression of NiCaS on Echo showed a slope of 0.97, 95% CI (0.91, 1.02) which did not differ from 1, P = 0.20. A Bland-Altman plot and 4-Quadrant plot confirmed that the 2 methods produced comparable measurements.

CONCLUSION

NiCaS SV measurements are similar to and strongly correlated with Echo SV measurements. This suggests that noninvasive NiCaS technology may be a practical method for measuring SV during HD.