Arterial pressure-based cardiac output monitoring: a multicenter validation of the third-generation software in septic patients

Internal jugular vein collapsibility does not predict fluid responsiveness in spontaneously breathing patients after cardiac surgery

PURPOSE

The objective of our study was to evaluate the diagnostic accuracy of internal jugular vein (IJV) collapsibility as a predictor of fluid responsiveness in spontaneously breathing patients after cardiac surgery.

METHODS

In this prospective observational study, spontaneously breathing patients were enrolled on the first postoperative day after coronary artery bypass grafting. Hemodynamic data coupled with simultaneous ultrasound assessment of the IJV were collected at baseline and after passive leg raising test (PLR). Continuous cardiac index (CI), stroke volume (SV), and stroke volume variation (SVV) were assessed with FloTracTM/EV1000™. Fluid responsiveness was defined as an increase in CI ≥ 10% after PLR. We compared the differences in measured variables between fluid responders and non-responders and tested the ability of ultrasonographic IJV indices to predict fluid responsiveness.

RESULTS

Fifty-four patients were included in the study. Seventeen (31.5%) were fluid responders. The responders demonstrated significantly lower inspiratory and expiratory diameters of the IJV at baseline, but IJV collapsibility was comparable (P = 0.7). Using the cut-off point of 20%, IJV collapsibility predicted fluid responsiveness with a sensitivity of 76.5% and specificity of 38.9%, ROC AUC 0.55.

CONCLUSION

In spontaneously breathing patients after surgical coronary revascularisation, collapsibility of the internal jugular vein did not predict fluid responsiveness.

Prediction of Fluid Responsiveness Using Combined End-Expiratory and End-Inspiratory Occlusion Tests in Cardiac Surgical Patients

End-expiratory occlusion (EEO) and end-inspiratory occlusion (EIO) tests have been successfully used to predict fluid responsiveness in various settings using calibrated pulse contour analysis and echocardiography. The aim of this study was to test if respiratory occlusion tests predicted fluid responsiveness reliably in cardiac surgical patients with protective ventilation. This single-centre, prospective study, included 57 ventilated patients after elective coronary artery bypass grafting who were indicated for fluid expansion. Baseline echocardiographic measurements were obtained and patients with significant cardiac pathology were excluded. Cardiac index (CI), stroke volume and stroke volume variation were recorded using uncalibrated pulse contour analysis at baseline, after performing EEO and EIO tests and after volume expansion (7 mL/kg of succinylated gelatin). Fluid responsiveness was defined as an increase in cardiac index by 15%. Neither EEO, EIO nor their combination predicted fluid responsiveness reliably in our study. After a combined EEO and EIO, a cut-off point for CI change of 16.7% predicted fluid responsiveness with a sensitivity of 61.8%, specificity of 69.6% and ROC AUC of 0.593. In elective cardiac surgical patients with protective ventilation, respiratory occlusion tests failed to predict fluid responsiveness using uncalibrated pulse contour analysis.

New Developments in Continuous Hemodynamic Monitoring of the Critically Ill Patient

Hemodynamic monitoring is a cornerstone in the assessment of patients with circulatory shock. Timely recognition of hemodynamic compromise and proper optimisation is essential to ensure adequate tissue perfusion and maintain renal, hepatic, abdominal, and cerebral functions. Hemodynamic monitoring has significantly evolved since the first inception of the pulmonary artery catheter more than 50 years ago. Bedside echocardiography, when combined with noninvasive and minimally invasive technologies, provides tools to monitor and quantify the cardiac output to promptly react and improve hemodynamic management in an acute care setting. Commonly used technologies include noninvasive pulse-wave analysis, pulse-wave transit time, thoracic bioimpedance and bioreactance, esophageal Doppler, minimally invasive pulse-wave analysis, transpulmonary thermodilution, and pulmonary artery catheter. These monitoring strategies are reviewed here, along with detailed analysis of their operating mode, particularities, and limitations. The use of artificial intelligence to enhance performance and effectiveness of hemodynamic monitoring is reviewed to apprehend future possibilities.

Do Cerebral Cortex Perfusion, Oxygen Delivery, and Oxygen Saturation Responses Measured by Near-Infrared Spectroscopy Differ Between Patients Who Fail or Succeed in a Spontaneous Breathing Trial? A Prospective Observational Study

BACKGROUND

Alterations in perfusion to the brain during the transition from mechanical ventilation (MV) to a spontaneous breathing trial (SBT) remain poorly understood. The aim of the study was to determine whether changes in cerebral cortex perfusion, oxygen delivery (DO₂), and oxygen saturation (%StiO₂) during the transition from MV to an SBT differ between patients who succeed or fail an SBT.

METHODS

This was a single-center prospective observational study conducted in a 16-bed medical intensive care unit of the University Hospital Leuven, Belgium. Measurements were performed in 24 patients receiving MV immediately before and at the end of a 30-min SBT. Blood flow index (BFI), DO₂, and %StiO₂ in the prefrontal cortex, scalene, rectus abdominis, and thenar muscle were simultaneously assessed by near-infrared spectroscopy using the tracer indocyanine green dye. Cardiac output, arterial blood gases, and systemic oxygenation were also recorded.

RESULTS

During the SBT, prefrontal cortex BFI and DO₂ responses did not differ between SBT-failure and SBT-success groups (p > 0.05). However, prefrontal cortex %StiO₂ decreased in six of eight patients (75%) in the SBT-failure group (median [interquartile range 25-75%]: MV = 57.2% [49.1-61.7] vs. SBT = 51.0% [41.5-62.5]) compared to 3 of 16 patients (19%) in the SBT-success group (median [interquartile range 25-75%]: MV = 65.0% [58.6-68.5] vs. SBT = 65.1% [59.5-71.1]), resulting in a significant differential %StiO₂ response between groups (p = 0.031). Similarly, a significant differential response in thenar muscle %StiO₂ (p = 0.018) was observed between groups. A receiver operating characteristic analysis identified a decrease in prefrontal cortex %StiO₂ > 1.6% during the SBT as an optimal cutoff, with a sensitivity of 94% and a specificity of 75% to predict SBT failure and an area under the curve of 0.79 (95% CI: 0.55-1.00). Cardiac output, systemic oxygenation, scalene, and rectus abdominis BFI, DO₂, and %StiO₂ responses did not differ between groups (p > 0.05); however, during the SBT, a significant positive association in prefrontal cortex BFI and partial pressure of arterial carbon dioxide was observed only in the SBT-success group (SBT success: Spearman's ρ = 0.728, p = 0.002 vs. SBT failure: ρ = 0.048, p = 0.934).

CONCLUSIONS

This study demonstrated a reduced differential response in prefrontal cortex %StiO₂ in the SBT-failure group compared with the SBT-success group possibly due to the insufficient increase in prefrontal cortex perfusion in SBT-failure patients. A > 1.6% drop in prefrontal cortex %StiO₂ during SBT was sensitive in predicting SBT failure. Further research is needed to validate these findings in a larger population and to evaluate whether cerebral cortex %StiO₂ measurements by near-infrared spectroscopy can assist in the decision-making process on liberation from MV.

Optimising fluid requirements after initial resuscitation: A pilot study evaluating mini-fluid challenge and passive leg raising test in patients with predicted severe acute pancreatitis

BACKGROUND

The goals and approaches to fluid therapy vary through different stages of resuscitation. This pilot study was designed to test the safety and feasibility of a fluid therapy protocol for the second or optimisation stage of resuscitation in patients with predicted severe acute pancreatitis (SAP).

METHODS

Spontaneously breathing patients with predicted SAP were admitted after initial resuscitation and studied over a 24-h period in a tertiary hospital ward. Objective clinical assessment (OCA; heart rate, mean arterial pressure, urine output, and haematocrit) was done at 0, 4, 8, 12, 18-20, and 24 h. All patients had mini-fluid challenge (MFC; 250 ml intravenous normal saline within 10 min) at 0 h and repeated at 4 and 8 h if OCA score ≥2. Patients who were fluid responsive (>10% change in stroke volume after MFC) received 5-10 ml/kg/h, otherwise 1-3 ml/kg/h until the next time point. Passive leg raising test (PLRT) was done at each time point and compared with OCA for assessing volume status and predicting fluid responsiveness.

RESULTS

This fluid therapy protocol based on OCA, MFC, and PLRT and designed for the second stage of resuscitation was safe and feasible in spontaneously breathing predicted SAP patients. The PLRT was superior to OCA (at 0 and 8 h) for predicting fluid responsiveness and guiding fluid therapy.

CONCLUSIONS

This pilot study found that a protocol for intravenous fluid therapy specifically for the second stage of resuscitation in patients with predicted SAP was safe, feasible, and warrants further investigation.

Safety during interhospital helicopter transfer of ventilated COVID-19 patients. No clinical relevant changes in vital signs including non-invasive cardiac output

Background

During the COVID-19 pandemic in The Netherlands, critically ill ventilated COVID-19 patients were transferred not only between hospitals by ambulance but also by the Helicopter Emergency Medical Service (HEMS). To date, little is known about the physiological impact of helicopter transport on critically ill patients and COVID-19 patients in particular. This study was conducted to explore the impact of inter-hospital helicopter transfer on vital signs of mechanically ventilated patients with severe COVID-19, with special focus on take-off, midflight, and landing.

Methods

All ventilated critically ill COVID-19 patients who were transported between April 2020 and June 2021 by the Dutch ‘Lifeliner 5’ HEMS team and who were fully monitored, including noninvasive cardiac output, were included in this study. Three 10-min timeframes (take-off, midflight and landing) were defined for analysis. Continuous data on the vital parameters heart rate, peripheral oxygen saturation, arterial blood pressure, end-tidal CO₂ and noninvasive cardiac output using electrical cardiometry were collected and stored at 1-min intervals. Data were analyzed for differences over time within the timeframes using one-way analysis of variance. Significant differences were checked for clinical relevance.

Results

Ninety-eight patients were included in the analysis. During take-off, an increase was noticed in cardiac output (from 6.7 to 8.2 L min⁻¹; P < 0.0001), which was determined by a decrease in systemic vascular resistance (from 1071 to 739 dyne·s·cm⁻⁵, P < 0.0001) accompanied by an increase in stroke volume (from 88.8 to 113.7 mL, P < 0.0001). Other parameters were unchanged during take-off and mid-flight. During landing, cardiac output and stroke volume slightly decreased (from 8.0 to 6.8 L min⁻¹, P < 0.0001 and from 110.1 to 84.4 mL, P < 0.0001, respectively), and total systemic vascular resistance increased (P < 0.0001). Though statistically significant, the found changes were small and not clinically relevant to the medical status of the patients as judged by the attending physicians.

Conclusions

Interhospital helicopter transfer of ventilated intensive care patients with COVID-19 can be performed safely and does not result in clinically relevant changes in vital signs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02177-5.

Optimal Perfusion Targets in Cardiogenic Shock

Cardiology shock is a syndrome of low cardiac output resulting in end-organ dysfunction. Few interventions have demonstrated meaningful clinical benefit, and cardiogenic shock continues to carry significant morbidity with mortality rates that have plateaued at upwards of 40% over the past decade. Clinicians must rely on clinical, biochemical, and hemodynamic parameters to guide resuscitation. Several features, including physical examination, renal function, serum lactate metabolism, venous oxygen saturation, and hemodynamic markers of right ventricular function, may be useful both as prognostic markers and to guide therapy. This article aims to review these targets, their utility in the care of patients with cardiology shock, and their association with outcomes.

Colorectal Surgery in Critically Unwell Patients: A Multidisciplinary Approach

A proportion of patients require critical care support following elective or urgent colorectal procedures. Similarly, critically ill patients in intensive care units may also need colorectal surgery on occasions. This patient population is increasing in some jurisdictions given an aging population and increasing societal expectations. As such, this population often includes elderly, frail patients or patients with significant comorbidities. Careful stratification of operative risks including the need for prolonged intensive care support should be part of the consenting process. In high-risk patients, especially in setting of unplanned surgery, treatment goals should be clearly defined, and appropriate ceiling of care should be established to minimize care that is not in the best interest of the patient. In this article we describe approaches to critically unwell patients requiring colorectal surgery and how a multidisciplinary approach with proactive intensive care involvement can help achieve the best outcomes for these patients.

Monitoring of Cardiac Output Using a New Smartphone Application (Capstesia) vs. Vigileo FloTrac System

(1) Background: We tested Capstesia against a reference system, Vigileo FloTrac, in patients undergoing major vascular surgery procedures. (2) Methods: Twenty-two adult patients (236 data pairs) were enrolled. Cardiac output (CO), stroke volume (SV), systemic vascular resistance (SVR), and related indexed parameters from the two monitoring systems were collected and compared at eleven time points during surgery. Intraclass correlation coefficients with 95% confidence intervals (CIs) and Bland–Altman plots with percentages of error were used. (3) Results: The interclass correlation coefficients for CO, SV, and SVR were 0.527 (95%CI 0.387 to 0.634), 0.580 (95%CI 0.454 to 0.676), and 0.609 (95%CI 0.495 to 0.698), respectively. In the Bland–Altman analysis, bias (and limits of agreement) of CO was 0.33 L min−1 (−2.44; 3.10), resulting in a percentage error of 61.91% for CO. For SV, it was 5.02 mL (−36.42; 46.45), with 57.19% of error. Finally, the bias (and limit of agreement) of SVR was −75.99 dyne sec cm−5 (−870.04; 718.06), resulting in an error of 69.94%. (4) Conclusions: Although promising, cost-effective, and easy to use, the moderate level of agreement with Vigileo and the high level of error make Capstesia unsuitable for use in the intraoperative setting of vascular surgery. Critical errors in acquisition or digitalization of the snap might have a strong impact on the accuracy and performance. Further standardization of the acquisition technique and improvements in the processing algorithm are needed.

Bioreactance and fourth-generation pulse contour methods in monitoring cardiac index during off-pump coronary artery bypass surgery

The pulmonary artery catheter (PAC) is considered the gold standard for cardiac index monitoring. Recently new and less invasive methods to assess cardiac performance have been developed. The aim of our study was to assess the reliability of a non-invasive monitor utilizing bioreactance (Starling SV) and a non-calibrated mini-invasive pulse contour device (FloTrac/EV1000, fourth-generation software) compared to bolus thermodilution technique with PAC (TDCO) during off-pump coronary artery bypass surgery (OPCAB). In this prospective study, 579 simultaneous intra- and postoperative cardiac index measurements obtained with Starling SV, FloTrac/EV1000 and TDCO were compared in 20 patients undergoing OPCAB. The agreement of data was investigated by Bland-Altman plots, while trending ability was assessed by four-quadrant plots with error grids. In comparison with TDCO, Starling SV was associated with a bias of 0.13 L min^-1 m^-2 (95% confidence interval, 95% CI, 0.07 to 0.18), wide limits of agreement (LOA, - 1.23 to 1.51 L min^-1 m^-2), a percentage error (PE) of 60.7%, and poor trending ability. In comparison with TDCO, FloTrac was associated with a bias of 0.01 L min^-1 m^-2 (95% CI - 0.05 to 0.06), wide LOA (- 1.27 to 1.29 L min^-1 m^-2), a PE of 56.8% and poor trending ability. Both Starling SV and fourth-generation FloTrac showed acceptable mean bias but imprecision due to wide LOA and high PE, and poor trending ability. These findings indicate limited reliability in monitoring cardiac index in patients undergoing OPCAB.

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.

Noninvasive Monitoring in the Intensive Care Unit

There has been considerable development in the field of noninvasive hemodynamic monitoring in recent years. Multiple devices have been proposed to assess blood pressure, cardiac output, and tissue perfusion. All have their own advantages and disadvantages and selection should be based on individual patient requirements and disease severity and adjusted according to ongoing patient evolution.

Comparison the accuracy and trending ability of cardiac index measured by the fourth- generation of FloTrac with the PiCCO device in septic shock patients

Background/aim

FloTrac/Vigileo is a noncalibrated arterial pressure waveform analysis for cardiac index (CI) monitoring. The aim of our study was to compare the CI measured by the 4th generation of FloTrac with PiCCO in septic shock patients.

Materials and methods

We simultaneously measured the CI using FloTrac (CIv) and compared it with the CI derived from transpulmonary thermodilution (CItd) as well as the pulse contour-derived CI using PiCCO (CIp).

Results

Thirty-one septic shock patients were included. The CIv correlated with CItd (r = 0.62, P < 0.0001). The Bland-Altman analysis showed a bias of 0.14, and the limits of agreement were –1.62–1.91 L/min/m2 with a percentage error of 47.4%. However, the concordance rate between CIv and CItd was 93.6%. The comparison of CIv with CIp (n = 352 paired measurements) revealed a bias of -0.16, and the limits of agreement were –1.45–1.79 L/min/m2 with a percentage error of 44.8%. The overall correlation coefficient between CIv and CIp was 0.63 (P < 0.0001), and the concordance rate was 85.4%.

Conclusion

The 4th generation of FloTrac has not acceptable agreement to assess CI; however, it has the ability to tracked changes of CI, when compared with the transpulmonary thermodilution method by PiCCO.

Collapsibility of the Right Internal Jugular Vein Predicts Responsiveness to Fluid Administration in Patients Receiving Pressure Support Ventilation: A Prospective Cohort Study

Background

The aim of this study was to evaluate the utility of collapsibility of the internal jugular veins (IJVs) and subclavian veins (SCVs) in comparison with collapsibility of the inferior vena cava (IVC) in patients receiving pressure support ventilation.

Methods

Patients receiving pressure support ventilation were prospectively enrolled when fluid bolus administration was clinically indicated. The antero-posterior diameters of IJVs, SCVs and IVC were measured. Fluid responsiveness was defined as an 8% increase in stroke volume calculated with arterial pulse contour analysis after a passive leg raising maneuver.

Results

Twenty-seven patients (34 measurements) were included. Eighteen measurements were deemed fluid responsive. The area under the receiver operating characteristic curve of collapsibility of the right IJV antero-posterior diameter was 0.88 (95% confidence interval (CI): 0.75 - 0.99), while the area under the ROC curves for the antero-posterior diameter of the left IJV, right SCV, left SCV and the IVC were 0.57 (95% CI: 0.37 - 0.77), 0.61 (95% CI: 0.41 - 0.80), 0.55 (95% CI: 0.35 - 0.76) and 0.57 (95% CI: 0.37 - 0.77), respectively.

Conclusions

These results suggest that collapsibility of the right IJV is a useful predictor of fluid responsiveness in patients receiving pressure support ventilation. Collapsibility of the IVC did not predict fluid responsiveness in these patients.

Cerebral cortex and respiratory muscles perfusion during spontaneous breathing attempts in ventilated patients and its relation to weaning outcomes: a protocol for a prospective observational study

INTRODUCTION

In addition to the well-documented factors that contribute to weaning failure, increased energy demands of the respiratory muscles during spontaneous breathing trials (SBTs) might not be met by sufficient increases in energy supplies. This discrepancy may deprive blood and oxygen of other tissues. In this context, restrictions in perfusion of splanchnic organs and non-working muscles during SBT have been associated with weaning failure. However, alterations in perfusion of the brain during the weaning process are less well understood.

OBJECTIVE AND HYPOTHESIS

To investigate whether cerebral cortex perfusion evolves differentially during the transition from mechanical ventilation (MV) to spontaneous breathing between patients failing or succeeding the SBT. We hypothesise that patients failing the SBT will exhibit reduced cerebral cortex perfusion during the transition from MV to spontaneous breathing as compared with patients succeeding the SBT.

METHODS AND ANALYSIS

This single-centre, prospective, observational study will be conducted in a medical Intensive Care unit of University Hospital Leuven, Belgium in ready to wean patients. Blood flow index in the cerebral cortex (prefrontal area), inspiratory (scalene) and expiratory muscle (upper rectus abdominis) and a non-working muscle (thenar eminence) will be simultaneously assessed by near-infrared spectroscopy (NIRS) using the tracer indocyanine green dye. Measurements will be performed on the same day during MV and during SBT. NIRS-derived tissue oxygenation index and cardiac output (by pulse contour analyses) will be recorded continuously. Twenty patients failing an SBT are estimated to be sufficient for detecting a significant difference in the change of cerebral cortex perfusion from MV to SBT (primary outcome) between SBT failure and success patients.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the local ethical committee (Ethische Commissie Onderzoek UZ/KU Leuven protocol ID: S60516). Results from this study will be presented at scientific meetings and congresses and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03240263; Pre-results.

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

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

The pulmonary artery catheter: is it still alive?

PURPOSE OF REVIEW

The present review discusses the current role of the pulmonary artery catheter (PAC) in the hemodynamic monitoring of critically ill patients.

RECENT FINDINGS

The PAC has an important role in the characterization and management of hemodynamic alterations in critically ill patients. Use of the PAC has decreased in the last 30 years because of recent advances in less invasive hemodynamic monitoring techniques, in particular transpulmonary thermodilution and echocardiography, combined with the publication of the results of several randomized trials that failed to show improvements in outcome with the use of the PAC in various settings. Although it is obvious that the PAC should not be used in most critically ill patients, the PAC is still indicated in some patients with circulatory and/or respiratory failure, especially when associated with pulmonary hypertension or left heart dysfunction. As for any technique, optimal PAC use requires expertise in insertion, acquisition, and interpretation of measurements. The decrease in use of the PAC may unfortunately limit exposure of junior doctors and nurses to this device, so that they become less familiar with using the PAC, making it more complicated and less optimal.

SUMMARY

The PAC still has an important role in the cardiopulmonary monitoring of critically ill patients.

Validation of radial artery-based uncalibrated pulse contour method (PulsioFlex) in critically ill patients: A observational study

BACKGROUND

Because of their simplicity, uncalibrated pulse contour (UPC) methods have been introduced into clinical practice in critical care but are often validated with a femoral arterial waveform.

OBJECTIVE

We aimed to test the accuracy of cardiac index (CI) measurements and trending ability from a radial artery with one UPC.

DESIGN

An observational study.

SETTING

Tertiary care mixed-surgical ICU. Data were obtained from April 2015 to July 2016.

PATIENTS

We studied 20 critically ill mechanically ventilated patients monitored by UPC (PulsioFlex; Pulsion Medical Systems SE, Feldkirchen, Germany). We used transpulmonary thermodilution (PiCCO2) as a reference.

MAIN OUTCOME MEASURES

Bland-Altman-analyses with percentage errors were calculated to assess the accuracy of CI values from radial pulse contour analysis (CIRAD), autocalibration (CIAC) and femoral pulse contour analysis (CIFEM). All were compared with a reference (CITD) at 4-h intervals for 24 h. Trending ability was assessed by polar-plots and four-quadrant-plots. CI is given in l min m.

RESULTS

Bland-Altman-analyses: for CIRAD, the mean bias was -0.1 with limits of agreement (LOA) of -2.9 to 2.7 and a percentage error of 70%; for CIAC, the mean bias was 0 with LOA -2.8 to 2.7 and a percentage error of 70%; for CIFEM, the mean bias was 0 with LOA -1.2 to 1.2 and a percentage error of 30%, respectively. Polar plots for trending: for CIRAD, the angular bias was 12° with radial LOA of 39°, a polar concordance rate of 73% and a concordance rate of 67% in the four-quadrant-plot; for CIAC, the angular bias was 4° with radial LOA of 41°, polar concordance rate of 79% and a concordance rate of 74% in the four quadrant plot; for CIFEM, the angular bias was -2° with radial LOA of 50°, polar concordance rate of 74% and a concordance rate of 81%.

CONCLUSION

In critically ill patients, the PulsioFlex system connected to a radial arterial catheter is inaccurate for CI measurements and does not track changes in CI adequately. We therefore recommend using validated thermodilution techniques for monitoring in the critical care setting.

Internal jugular vein variability predicts fluid responsiveness in cardiac surgical patients with mechanical ventilation

BACKGROUND

To evaluate the efficacy of using internal jugular vein variability (IJVV) as an index of fluid responsiveness in mechanically ventilated patients after cardiac surgery.

METHODS

Seventy patients were assessed after cardiac surgery. Hemodynamic data coupled with ultrasound evaluation of IJVV and inferior vena cava variability (IVCV) were collected and calculated at baseline, after a passive leg raising (PLR) test and after a 500-ml fluid challenge. Patients were divided into volume responders (increase in stroke volume ≥ 15%) and non-responders (increase in stroke volume < 15%). We compared the differences in measured variables between responders and non-responders and tested the ability of the indices to predict fluid responsiveness.

RESULTS

Thirty-five (50%) patients were fluid responders. Responders presented higher IJVV, IVCV and stroke volume variation (SVV) compared with non-responders at baseline (P < 0.05). The relationship between IJVV and SVV was moderately correlated (r = 0.51, P < 0.01). The areas under the receiver operating characteristic (ROC) curves for predicting fluid responsiveness were 0.88 (CI 0.78-0.94) for IJVV compared with 0.83 (CI 0.72-0.91), 0.97 (CI 0.89-0.99), 0.91 (CI 0.82-0.97) for IVCV, SVV, and the increase in stroke volume in response to a PLR test, respectively.

CONCLUSIONS

Ultrasound-derived IJVV is an accurate, easily acquired noninvasive parameter of fluid responsiveness in mechanically ventilated postoperative cardiac surgery patients, with a performance similar to that of IVCV.

Cardiac Output Assessed by the Fourth-Generation Arterial Waveform Analysis System Is Unreliable in Liver Transplant Recipients

BACKGROUND

Liver transplant recipients often have violent hemodynamic fluctuation during surgery that may be related to perioperative and postoperative morbidity. Because there are some considerations for the risk of the pulmonary arterial catheter (PAC), the conventional invasive device for cardiac output (CO) measurement, a reliable and minimally invasive alternative is required. We validated the reliability of CO measurements with the use of a minimally invasive FloTrac system with the latest fourth-generation algorithm in liver transplant recipients.

METHODS

Forty liver transplant recipients without atrial fibrillation, valvular pathology, or intracardiac shunt were recruited in this prospective, observational study. CO values measured by use of PAC with continuous thermodilution method (COTh) and FloTrac devices (COFT) were collected simultaneously throughout the operation for reliability validation.

RESULTS

Four hundred pairs of CO data points were collected in total. The linear regression analysis showed a high correlation coefficient (73%, P < .001). However, the percent error between COTh and COFT was 42.2%, which is worse than the established interchangeability criterion of 30%. The concordance rates were calculated at 89% and 59% by 4-quadrant plot and polar plot analysis, respectively. Neither met the preset validation criteria (>92% for the 4-quadrant plot and >90% for polar plot analyses).

CONCLUSIONS

Our study demonstrates that the CO measurements in liver transplant recipients by the latest FloTrac system and the PAC do not meet the recognized interchangeability criterion. Although the result showed improvement in linear regression analysis, it failed to display a qualified trending ability.

Fluid responsiveness prediction using Vigileo FloTrac measured cardiac output changes during passive leg raise test

Background

Passive leg raising (PLR) is a so called self-volume challenge used to test for fluid responsiveness. Changes in cardiac output (CO) or stroke volume (SV) measured during PLR are used to predict the need for subsequent fluid loading. This requires a device that can measure CO changes rapidly. The Vigileo™ monitor, using third-generation software, allows continuous CO monitoring. The aim of this study was to compare changes in CO (measured with the Vigileo device) during a PLR manoeuvre to calculate the accuracy for predicting fluid responsiveness.

Methods

This is a prospective study in a 20-bedded mixed general critical care unit in a large non-university regional referral hospital. Fluid responders were defined as having an increase in CO of greater than 15 % following a fluid challenge. Patients meeting the criteria for circulatory shock with a Vigileo™ monitor (Vigileo™; FloTrac; Edwards™; Lifesciences, Irvine, CA, USA) already in situ, and assessed as requiring volume expansion by the clinical team based on clinical criteria, were included. All patients underwent a PLR manoeuvre followed by a fluid challenge.

Results

Data was collected and analysed on stroke volume variation (SVV) at baseline and CO and SVV changes during the PLR manoeuvre and following a subsequent fluid challenge in 33 patients. The majority had septic shock. Patient characteristics, baseline haemodynamic variables and baseline vasoactive infusion requirements were similar between fluid responders (10 patients) and non-responders (23 patients). Peak increase in CO occurred within 120 s during the PLR in all cases. Using an optimal cut point of 9 % increase in CO during the PLR produced an area under the receiver operating characteristic curve of 0.85 (95 % CI 0.63 to 1.00) with a sensitivity of 80 % (95 % CI 44 to 96 %) and a specificity of 91 % (95 % CI 70 to 98 %).

Conclusions

CO changes measured by the Vigileo™ monitor using third-generation software during a PLR test predict fluid responsiveness in mixed medical and surgical patients with vasopressor-dependent circulatory shock.

Electronic supplementary material

The online version of this article (doi:10.1186/s40560-016-0188-6) contains supplementary material, which is available to authorized users.

Comparison of PulsioFlex® uncalibrated pulse contour method and a modified Fick principle with transpulmonary thermodilution measurements in critically ill patients

Monitoring of cardiac index (CI) by uncalibrated pulse contour (PC) methods has been shown to be inaccurate in critically ill patients. We tested accuracy and trending of a new pulse contour method and a modified Fick method using central venous oxygen saturation. We studied 21 critically ill and mechanically ventilated patients (age 20-86 years) monitored by PC (PulsioFlex®) and transpulmonary thermodilution (TPTD, PiCCO2®) as reference. At baseline, reference and PC-derived CI (CIPC) were recorded and CI obtained by Fick's method (FM, CIFICK). After four hours, measurements were performed analogously for trending analysis. CI are given in l/min/m2 as mean±standard deviation. At baseline CITPTD was 3.7±0.7, CIPC 3.8±0.7 and CIFICK 5.2±1.8. After 4 hours, CITPTD was 3.5±0.6, CIPC 3.8±1.2 and CIFICK 4.8±1.7. Mean bias for PC at baseline was -0.1 (limits of agreement [LOA] -1.4 to 1.2) and -0.4 (LOA -2.6 to 1.9) after four hours. Percentage errors (PE) were 34% and 60% respectively. FM revealed a bias of -1.5 (LOA -4.8 to 1.8, PE 74%) at baseline and -1.5 (LOA -4.5 to 1.4, PE 68%) at four hours. With an exclusion window of 10% of mean cardiac index, trending analysis by polar plots showed an angular bias of 5° (radial LOA±57°) for PC and 16° (radial LOA±51°) for FM. Although PC values at baseline were marginally acceptable, both methods fail to yield clinically acceptable absolute values. Likewise, trending ability is not adequate for both methods to be used in critically ill patients.

Inferior vena cava diameter variation compared with pulse pressure variation as predictors of fluid responsiveness in patients with sepsis

BACKGROUND

Currently, physicians employ pulse pressure variation (PPV) as a gold standard for predicting fluid responsiveness. However, employing ultrasonography in intensive care units is increasing, including using the ultrasonography for assessment of fluid responsiveness. Data comparing the performance of both methods are still lacking. This is the reason for the present study.

MATERIALS AND METHODS

We conducted a prospective observational study in patients with sepsis requiring fluid challenge. The PPV, inferior vena cava diameter variation (IVDV), stroke volume variation (SVV), and the other hemodynamic variables were recorded before and after fluid challenges. Fluid responders were identified when cardiac output increased more than 15% after fluid loading.

RESULTS

A total of 29 patients with sepsis were enrolled in this study. Sixteen (55.2%) were fluid responders. Threshold values to predict fluid responsiveness were 13.8% of PPV (sensitivity 100% and specificity 84.6%), 10.2% of IVDV (sensitivity 75% and specificity 76.9%) and 10.7% of SVV (sensitivity 81.3% and specificity 76.9%). The area under the curves of receiver operating characteristic showed that PPV (0.909, 95% confidence interval [CI], 0.784-1.00) and SVV (0.812, 95% CI, 0.644-0.981) had greater performance than IVDV (0.688, 95% CI, 0.480-0.895) regarding fluid responsiveness assessment.

CONCLUSIONS

The present study demonstrated better performance of the PPV than the IVDV. A threshold value more than 10% may be used for identifying fluid responders.

Monitoring high-risk patients: minimally invasive and non-invasive possibilities

Over the past decades, there has been considerable progress in the field of less invasive haemodynamic monitoring technologies. Substantial evidence has accumulated, which supports the continuous measurement and optimization of flow-based variables such as stroke volume, that is, cardiac output, in order to prevent occult hypoperfusion and consequently to improve patients' outcome in the perioperative setting. However, there is a striking gap between the developments in haemodynamic monitoring and the increasing evidence to implement defined treatment protocols based on the measured variables, and daily clinical routine. Recent trials have shown that perioperative morbidity and mortality is higher than anticipated. This emphasizes the need for the anaesthesia community to address this issue and promotes the implementation of proven concepts into clinical practice in order to improve patients' outcome, especially in high-risk patients. The advances in minimally invasive and non-invasive monitoring techniques can be seen as a driving force in this respect, as the degree of invasiveness of any monitoring tool determines the frequency of its application, especially in the operating room (OR). From this point of view, we are very confident that some of these minimally invasive and non-invasive haemodynamic monitoring technologies will become an inherent part of our monitoring armamentarium in the OR and in the intensive care unit (ICU).

Agreement in hemodynamic monitoring during orthotopic liver transplantation: a comparison of FloTrac/Vigileo at two monitoring sites with pulmonary artery catheter thermodilution

To study agreement in cardiac index (CI), systemic vascular resistance index (Systemic VRI) and stroke volume variation (SV variation) between the FloTrac/Vigileo at radial and femoral arterial cannulation sites, and pulmonary artery catheter (PAC) thermodilution, in patients undergoing orthotopic liver transplantation. A prospective observational study of 25 adult patients with liver failure. Radial and femoral arteries were cannulated with standardised FloTrac/Vigileo arterial transducer kits and a PAC was inserted. CI, SV variation and Systemic VRI were measured four times (30 min after induction of anesthesia, 30 min after portal vein clamping, 30 min after graft reperfusion, 30 min after commencement of bile duct anastomosis). The bias, precision, limits of agreement (LOA) and percentage errors were calculated using Bland-Altman statistics to compare measurements from radial and femoral arterial cannulation sites and PAC thermodilution. Neither radial nor femoral CI achieved acceptable agreement with PAC CI [radial to PAC bias (SD) 1.17 (1.49) L/min/m², percentage error 64.40 %], [femoral to PAC bias (SD) -0.71 (1.81) L/min/m², percentage error 74.20 %]. Agreement between radial and femoral sites for CI [mean difference (SD) -0.43 (1.51) L/min/m², percentage error 70.40 %] and Systemic VRI [mean difference (SD) 0.03 (4.17) LOA ±8.17 mmHg min m²/L] were also unacceptable. Agreement in SV variation between radial and femoral measurement sites approached a clinically acceptable threshold [mean difference (SD) 0.68 (2.44) %), LOA ±4.78 %]. FloTrac/Vigileo CI cannot substitute for PAC thermodilution CI, regardless of measurement site. SV variation measurements may be interchangeable between radial and femoral sites for determining fluid responsiveness.

Hemodynamic monitoring in the era of digital health

Digital innovations are changing medicine, and hemodynamic monitoring will not be an exception. Five to ten years from now, we can envision a world where clinicians will learn hemodynamics with simulators and serious games, will monitor patients with wearable or implantable sensors in the hospital and after discharge, will use medical devices able to communicate and integrate the historical, clinical, physiologic and biological information necessary to predict adverse events, propose the most rationale therapy and ensure it is delivered properly. Considerable intellectual and financial investments are currently made to ensure some of these new ideas and products soon become a reality.

Agreement in hemodynamic monitoring during orthotopic liver transplantation: a comparison of FloTrac/Vigileo at two monitoring sites with pulmonary artery catheter thermodilution

To study agreement in cardiac index (CI), systemic vascular resistance index (Systemic VRI) and stroke volume variation (SV variation) between the FloTrac/Vigileo at radial and femoral arterial cannulation sites, and pulmonary artery catheter (PAC) thermodilution, in patients undergoing orthotopic liver transplantation. A prospective observational study of 25 adult patients with liver failure. Radial and femoral arteries were cannulated with standardised FloTrac/Vigileo arterial transducer kits and a PAC was inserted. CI, SV variation and Systemic VRI were measured four times (30 min after induction of anesthesia, 30 min after portal vein clamping, 30 min after graft reperfusion, 30 min after commencement of bile duct anastomosis). The bias, precision, limits of agreement (LOA) and percentage errors were calculated using Bland-Altman statistics to compare measurements from radial and femoral arterial cannulation sites and PAC thermodilution. Neither radial nor femoral CI achieved acceptable agreement with PAC CI [radial to PAC bias (SD) 1.17 (1.49) L/min/m², percentage error 64.40 %], [femoral to PAC bias (SD) -0.71 (1.81) L/min/m², percentage error 74.20 %]. Agreement between radial and femoral sites for CI [mean difference (SD) -0.43 (1.51) L/min/m², percentage error 70.40 %] and Systemic VRI [mean difference (SD) 0.03 (4.17) LOA ±8.17 mmHg min m²/L] were also unacceptable. Agreement in SV variation between radial and femoral measurement sites approached a clinically acceptable threshold [mean difference (SD) 0.68 (2.44) %), LOA ±4.78 %]. FloTrac/Vigileo CI cannot substitute for PAC thermodilution CI, regardless of measurement site. SV variation measurements may be interchangeable between radial and femoral sites for determining fluid responsiveness.

Shock in the first 24 h of intensive care unit stay: observational study of protocol-based fluid management

Precision in fluid management for shock could lead to better clinical outcomes. We evaluated the association of protocol-based fluid management with intensive care unit (ICU) and hospital mortality. We performed an observational study of mechanically ventilated patients admitted directly from our emergency department to the ICU from August 2011 to December 2013, who had circulatory shock in the first 24 h of ICU stay (systolic blood pressure <90 mmHg at ICU admission or lactate >4 mmol/L). Patients with onset of shock beyond 24 h of ICU stay were excluded. Protocol-based fluid management required close physician-nurse cooperation and computerized documentation, checking for fluid response (≥10% arterial pulse pressure or stroke volume increase after two consecutive 250-mL crystalloid boluses), and fluid loading with repeated 500-mL boluses until fluid response became negative. Six hundred twelve mechanically ventilated patients with shock (mean [±SD] age, 63.0 years [16.5]; 252 or 41.2% females; mean Acute Physiology and Chronic Health Evaluation II score, 30.2 [8.8]) were studied. The fluid management protocol was used 455 times for 242 patients (39.5% of 612 patients) within the first 24 h of ICU stay, with 244 (53.6% of 455) positive responses. Adjusted for age, sex, Acute Physiology and Chronic Health Evaluation II score, comorbidity, and admission year, protocol use was associated with reduced ICU mortality (odds ratio, 0.60; 95% confidence interval, 0.39-0.94; P = 0.025) but not hospital mortality (odds ratio, 0.82; 95% confidence interval, 0.54-1.23; P = 0.369). Among mechanically ventilated patients with shock within the first 24 h of ICU stay, about half had positive fluid responses. Adherence to protocol-based fluid management was associated with improved ICU survival.

Accuracy of an autocalibrated pulse contour analysis in cardiac surgery patients: a bi-center clinical trial

BACKGROUND

Less-invasive and easy to install monitoring systems for continuous estimation of cardiac index (CI) have gained increasing interest, especially in cardiac surgery patients who often exhibit abrupt haemodynamic changes. The aim of the present study was to compare the accuracy of CI by a new semi-invasive monitoring system with transpulmonary thermodilution before and after cardiopulmonary bypass (CPB).

METHODS

Sixty-five patients (41 Germany, 24 Spain) scheduled for elective coronary surgery were studied before and after CPB, respectively. Measurements included CI obtained by transpulmonary thermodilution (CITPTD) and autocalibrated semi-invasive pulse contour analysis (CIPFX). Percentage changes of CI were also calculated.

RESULTS

There was only a poor correlation between CITPTD and CIPFX both before (r (2) = 0.34, p < 0.0001) and after (r (2) = 0.31, p < 0.0001) CPB, with a percentage error (PE) of 62 and 49 %, respectively. Four quadrant plots revealed a concordance rate over 90 % indicating an acceptable correlation of trends between CITPTD and CIPFX before (concordance: 93 %) and after (concordance: 94 %) CPB. In contrast, polar plot analysis showed poor trending before and an acceptable trending ability of changes in CI after CPB.

CONCLUSIONS

Semi-invasive CI by autocalibrated pulse contour analysis showed a poor ability to estimate CI compared with transpulmonary thermodilution. Furthermore, the new semi-invasive device revealed an acceptable trending ability for haemodynamic changes only after CPB.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02312505 Date: 12.03.2012.

Unreliable Tracking Ability of the Third-Generation FloTrac/Vigileo™ System for Changes in Stroke Volume after Fluid Administration in Patients with High Systemic Vascular Resistance during Laparoscopic Surgery

BACKGROUND

The FloTrac/Vigileo™ system does not thoroughly reflect variable arterial tones, due to a lack of external calibration. The ability of this system to measure stroke volume and track its changes after fluid administration has not been fully evaluated in patients with the high systemic vascular resistance that can develop during laparoscopic surgery.

METHODS

In 42 patients undergoing laparoscopic prostatectomy, the stroke volume derived by the third-generation FloTrac/Vigileo™ system (SV-Vigileo), the stroke volume measured using transesophageal echocardiography (SV-TEE) as a reference method, and total systemic vascular resistance were evaluated before and after 500 ml fluid administration during pneumoperitoneum combined with the Trendelenburg position.

RESULTS

Total systemic vascular resistance was 2159.4 ± 523.5 dyn·s/cm5 before fluid administration. The SV-Vigileo was significantly higher than the SV-TEE both before (68.8 ± 15.9 vs. 57.0 ± 11.0 ml, P < 0.001) and after (73.0 ± 14.8 vs. 64.9 ± 12.2 ml, P = 0.003) fluid administration. During pneumoperitoneum combined with the Trendelenburg position, Bland-Altman analysis for repeated measures showed a 53.8% of percentage error between the SV-Vigileo and the SV-TEE. Four-quadrant plot (69.2% of a concordance rate) and polar plot analysis (20.6° of a mean polar angle, 16.4° of the SD of a polar angle, and ±51.5° of a radial sector containing 95% of the data points) did not indicate a good trending ability of the FloTrac/Vigileo™ system.

CONCLUSIONS

The third-generation FloTrac/Vigileo™ system may not be useful in patients undergoing laparoscopic surgery, based on unreliable performance in measuring the stroke volume and in tracking changes in the stroke volume after fluid administration during pneumoperitoneum combined with the Trendelenburg position.

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.

Comparison of an advanced minimally invasive cardiac output monitoring with a continuous invasive cardiac output monitoring during lung transplantation

The aim of this study was to compare a continuous non-calibrated left heart cardiac index (CI) measurement by arterial waveform analysis (FloTrac(®)/Vigileo(®)) with a continuous calibrated right heart CI measurement by pulmonary artery thermodilution (CCOmbo-PAC(®)/Vigilance II(®)) for hemodynamic monitoring during lung transplantation. CI was measured simultaneously by both techniques in 13 consecutive lung transplants (n = 4 single-lung transplants, n = 9 sequential double-lung transplants) at distinct time points perioperatively. Linear regression analysis and Bland-Altman analysis with percentage error calculation were used for statistical comparison of CI measurements by both techniques. In this study the FloTrac(®) system underestimated the CI in comparison with the continuous pulmonary arterial thermodilution (p < 0.000). For all measurement pairs we calculated a bias of -0.55 l/min/m(2) with limits of agreement between -2.31 and 1.21 l/min/m(2) and a percentage error of 55 %. The overall correlations before clamping a branch oft the pulmonary artery (percentage error 41 %) and during the clamping periods of a branch oft the pulmonary artery (percentage error 66 %) failed to reached the required percentage error of less than 30 %. We found good agreement of both CI measurements techniques only during the measurement point "15 min after starting the second one-lung ventilation period" (percentage error 30 %). No agreement was found during all other measurement points. This pilot study shows for the first time that the CI of the FloTrac(®) system is not comparable with the continuous pulmonary-artery thermodilution during lung transplantation including the time periods without clamping a branch of the pulmonary artery. Arterial waveform and continuous pulmonary artery thermodilution are, therefore, not interchangeable during these complex operations.

Minimally invasive monitoring

Although use of the classic pulmonary artery catheter has declined, several techniques have emerged to estimate cardiac output. Arterial pressure waveform analysis computes cardiac output from the arterial pressure curve. The method of estimating cardiac output for these devices depends on whether they need to be calibrated by an independent measure of cardiac output. Some newer devices have been developed to estimate cardiac output from an arterial curve obtained noninvasively with photoplethysmography, allowing a noninvasive beat-by-beat estimation of cardiac output. This article describes the different devices that perform pressure waveform analysis.

Evaluation of the non-calibrated pulse contour cardiac output monitor FloTrac/Vigileo against thermodilution in standing horses

OBJECTIVE

To evaluate the non-calibrated, minimally invasive cardiac output (CO) monitor FloTrac/Vigileo (FloTrac) against thermodilution (TD) CO in standing horses.

STUDY DESIGN

Prospective, experimental trial.

ANIMALS

Nine adult horses weighing a median (range) of 535 (470-602) kg.

METHODS

Catheters were placed in the right atrium, pulmonary artery and carotid artery under local anaesthesia. CO was measured 147 times by TD and FloTrac and indexed to body weight. Changes in CO were achieved with romifidine or xylazine and dobutamine constant rate infusions. Bland-Altman analysis, concordance and polar plot analysis were used to assess agreement and ability to track changes in CO.

RESULTS

Mean ± standard deviation COTD of 48 ± 16 mL kg(-1) minute(-1) (range: 19-93 mL kg(-1) minute(-1) ) and mean COF loTrac of 9 ± 3 mL kg(-1) minute(-1) (range: 5-21 mL kg(-1) minute(-1) ) were measured. Low agreement with a large mean bias of 39 mL kg(-1) minute(-1) and wide limits of agreement of 8-70 mL kg(-1) minute(-1) were found. The percentage error of 108% and precision of TD of ± 18% resulted in an estimated precision of FloTrac of ± 106%. Comparison of changes in COF loTrac with changes in COTD gave a concordance rate of 52% in the four-quadrant plot, and a mean polar angle of -11° with radial limits of agreement of ± 61 ° in the polar plot. Mean arterial pressure (MAP) and COF loTrac were positively correlated (r = 0.5, p < 0.0001). No correlation of MAP with COTD was observed.

CONCLUSIONS AND CLINICAL RELEVANCE

The FloTrac system, originally designed for use in humans, neither measured absolute CO in standing horses accurately nor tracked relative changes in CO measured by TD correctly. The false dependence of COF loTrac on arterial blood pressure further discourages the use of this technique in horses.

Predictors of the accuracy of pulse-contour cardiac index and suggestion of a calibration-index: a prospective evaluation and validation study

Background

Cardiac Index (CI) is a key-parameter of hemodynamic monitoring. Indicator-dilution is considered as gold standard and can be obtained by pulmonary arterial catheter or transpulmonary thermodilution (TPTD; CItd). Furthermore, CI can be estimated by Pulse-Contour-Analysis (PCA) using arterial wave-form analysis (CIpc). Obviously, adjustment of CIpc to CItd initially improves the accuracy of CIpc. Despite uncertainty after which time accuracy of CIpc might be inappropriate, recalibration by TPTD is suggested after a maximum of 8 h.

We hypothesized that accuracy of CIpc might not only depend on time to last TPTD, but also on changes of the arterial wave curve detectable by PCA itself. Therefore, we tried to prospectively characterize predictors of accuracy and precision of CIpc (primary outcome). In addition to “time to last TPTD” we evaluated potential predictors detectable solely by pulse-contour-analysis.

Finally, the study aimed to develop a pulse-contour-derived “calibration-index” suggesting recalibration and to validate these results in an independent collective.

Methods

In 28 intensive-care-patients with PiCCO-monitoring (Pulsion Medical-Systems, Germany) 56 datasets were recorded. CIpc-values at baseline and after intervals of 1 h, 2 h, 4 h, 6 h and 8 h were compared to CItd derived from immediately subsequent TPTD. Results from this evaluation-collective were validated in an independent validation-collective (49 patients, 67 datasets).

Results

Mean bias values CItd-CIpc after different intervals ranged between -0.248 and 0.112 L/min/m². Percentage-error after different intervals to last TPTD ranged between 18.6% (evaluation, 2 h-interval) and 40.3% (validation, 6 h-interval). In the merged data, percentage-error was below 30% after 1 h, 2 h, 4 h and 8 h, and exceeded 30% only after 6 h. “Time to last calibration” was neither associated to accuracy nor to precision of CIpc in any uni- or multivariate analysis.

By contrast, the height of CIpc and particularly changes in CIpc compared to last thermodilution-derived CItd(base) univariately and independently predicted the bias CItd-CIpc in both collectives.

Relative changes of CIpc compared to CItd(base) exceeding thresholds derived from the evaluation-collective (-11.6% < CIpc-CItd(base)/CItd(base) < 7.4%) were confirmed as significant predictors of a bias |CItd-CIpc| ≥ 20% in the validation-collective.

Conclusion

Recalibration triggered by changes of CIpc compared to CItd(base) derived from last calibration should be preferred to fixed intervals.