A comparison of volume clamp method-based continuous noninvasive cardiac output (CNCO) measurement versus intermittent pulmonary artery thermodilution in postoperative cardiothoracic surgery patients.

The CNAP technology (CNSystems Medizintechnik AG, Graz, Austria) allows continuous noninvasive arterial pressure waveform recording based on the volume clamp method and estimation of cardiac output (CO) by pulse contour analysis. We compared CNAP-derived CO measurements (CNCO) with intermittent invasive CO measurements (pulmonary artery catheter; PAC-CO) in postoperative cardiothoracic surgery patients. In 51 intensive care unit patients after cardiothoracic surgery, we measured PAC-CO (criterion standard) and CNCO at three different time points. We conducted two separate comparative analyses: (1) CNCO auto-calibrated to biometric patient data (CNCObio) versus PAC-CO and (2) CNCO calibrated to the first simultaneously measured PAC-CO value (CNCOcal) versus PAC-CO. The agreement between the two methods was statistically assessed by Bland-Altman analysis and the percentage error. In a subgroup of patients, a passive leg raising maneuver was performed for clinical indications and we present the changes in PAC-CO and CNCO in four-quadrant plots (exclusion zone 0.5 L/min) in order to evaluate the trending ability of CNCO. The mean difference between CNCObio and PAC-CO was +0.5 L/min (standard deviation ± 1.3 L/min; 95% limits of agreement -1.9 to +3.0 L/min). The percentage error was 49%. The concordance rate was 100%. For CNCOcal, the mean difference was -0.3 L/min (±0.5 L/min; -1.2 to +0.7 L/min) with a percentage error of 19%. In this clinical study in cardiothoracic surgery patients, CNCOcal showed good agreement when compared with PAC-CO. For CNCObio, we observed a higher percentage error and good trending ability (concordance rate 100%).

Personalized hemodynamic management.

PURPOSE OF REVIEW: To describe personalized hemodynamic management of critically ill patients in the operating room and the ICU. RECENT FINDINGS: Several recent clinical studies have investigated different strategies for optimizing blood pressure (BP) and flow in the operating room and in the ICU. In the past, (early) goal-directed hemodynamic treatment strategies often used predefined fixed population-based 'normal' values as hemodynamic targets. Most hemodynamic variables, however, have large interindividual variability and are dependent on several biometric factors. Personalized BP management aims to set specific BP targets for a given patient taking into account blood flow autoregulation and any history of chronic hypertension. To optimize cardiac output and oxygen delivery, individualized hemodynamic management based on functional assessment of fluid responsiveness is used. Innovative noninvasive technologies now enable preoperative assessment of a patient's personal normal hemodynamic values, which can then be targeted in the perioperative phase. In critically ill patients admitted to the ICU, adaptive multiparametric hemodynamic monitoring can help to personalize hemodynamic management. SUMMARY: Personalized hemodynamic management targets personal normal values of hemodynamic variables, which are adjusted to biometric data and adapted to the clinical situation (i.e., adequate values). This approach optimizes cardiovascular dynamics based on the patient's personal hemodynamic profile.

Advanced Hemodynamic Management in Patients with Septic Shock.

In patients with sepsis and septic shock, the hemodynamic management in both early and later phases of these "organ dysfunction syndromes" is a key therapeutic component. It needs, however, to be differentiated between "early goal-directed therapy" (EGDT) as proposed for the first 6 hours of emergency department treatment by Rivers et al. in 2001 and "hemodynamic management" using advanced hemodynamic monitoring in the intensive care unit (ICU). Recent large trials demonstrated that nowadays protocolized EGDT does not seem to be superior to "usual care" in terms of a reduction in mortality in emergency department patients with early identified septic shock who promptly receive antibiotic therapy and fluid resuscitation. "Hemodynamic management" comprises (a) making the diagnosis of septic shock as one differential diagnosis of circulatory shock, (b) assessing the hemodynamic status including the identification of therapeutic conflicts, and (c) guiding therapeutic interventions. We propose two algorithms for hemodynamic management using transpulmonary thermodilution-derived variables aiming to optimize the cardiocirculatory and pulmonary status in adult ICU patients with septic shock. The complexity and heterogeneity of patients with septic shock implies that individualized approaches for hemodynamic management are mandatory. Defining individual hemodynamic target values for patients with septic shock in different phases of the disease must be the focus of future studies.

Continuous noninvasive cardiac output determination using the CNAP system: evaluation of a cardiac output algorithm for the analysis of volume clamp method-derived pulse contour.

The CNAP system (CNSystems Medizintechnik AG, Graz, Austria) provides noninvasive continuous arterial pressure measurements by using the volume clamp method. Recently, an algorithm for the determination of cardiac output by pulse contour analysis of the arterial waveform recorded with the CNAP system became available. We evaluated the agreement of the continuous noninvasive cardiac output (CNCO) measurements by CNAP in comparison with cardiac output measurements invasively obtained using transpulmonary thermodilution (TDCO). In this proof-of-concept analysis we studied 38 intensive care unit patients from a previously set up database containing CNAP-derived arterial pressure data and TDCO values obtained with the PiCCO system (Pulsion Medical Systems SE, Feldkirchen, Germany). We applied the new CNCO algorithm retrospectively to the arterial pressure waveforms recorded with CNAP and compared CNCO with the corresponding TDCO values (criterion standard). Analyses were performed separately for (1) CNCO calibrated to the first TDCO (CNCO-cal) and (2) CNCO autocalibrated to biometric patient data (CNCO-auto). We did not perform an analysis of trending capabilities because the patients were hemodynamically stable. The median age and APACHE II score of the 22 male and 16 female patients was 63 years and 18 points, respectively. 18 % were mechanically ventilated and in 29 % vasopressors were administered. Mean ± standard deviation for CNCO-cal, CNCO-auto, and TDCO was 8.1 ± 2.7, 6.4 ± 1.9, and 7.8 ± 2.4 L/min, respectively. For CNCO-cal versus TDCO, Bland-Altman analysis demonstrated a mean difference of +0.2 L/min (standard deviation 1.0 L/min; 95 % limits of agreement -1.7 to +2.2 L/min, percentage error 25 %). For CNCO-auto versus TDCO, the mean difference was -1.4 L/min (standard deviation 1.8 L/min; 95 % limits of agreement -4.9 to +2.1 L/min, percentage error 45 %). This pilot analysis shows that CNCO determination is feasible in critically ill patients. A percentage error of 25 % indicates acceptable agreement between CNCO-cal and TDCO. The mean difference, the standard deviation, and the percentage error between CNCO-auto and TDCO were higher than between CNCO-cal and TDCO. A hyperdynamic cardiocirculatory state in a substantial number of patients and the hemodynamic stability making trending analysis impossible are main limitations of our study.

Tracking Changes in Cardiac Output: Statistical Considerations on the 4-Quadrant Plot and the Polar Plot Methodology.

When comparing 2 technologies for measuring hemodynamic parameters with regard to their ability to track changes, 2 graphical tools are omnipresent in the literature: the 4-quadrant plot and the polar plot recently proposed by Critchley et al. The polar plot is thought to be the more advanced statistical tool, but care should be taken when it comes to its interpretation. The polar plot excludes possibly important measurements from the data. The polar plot transforms the data nonlinearily, which may prevent it from being seen clearly. In this article, we compare the 4-quadrant and the polar plot in detail and thoroughly describe advantages and limitations of each. We also discuss pitfalls concerning the methods to prepare the researcher for the sound use of both methods. Finally, we briefly revisit the Bland-Altman plot for the use in this context.

Radial Artery Applanation Tonometry for Continuous Noninvasive Cardiac Output Measurement: A Comparison With Intermittent Pulmonary Artery Thermodilution in Patients After Cardiothoracic Surgery.

OBJECTIVES: Radial artery applanation tonometry allows completely noninvasive continuous cardiac output estimation. The aim of the present study was to compare cardiac output measurements obtained with applanation tonometry (AT-CO) using the T-Line system (Tensys Medical, San Diego, CA) with cardiac output measured by intermittent pulmonary artery thermodilution using a pulmonary artery catheter (PAC-CO) with regard to accuracy, precision of agreement, and trending ability. DESIGN: A prospective method comparison study. SETTING: The study was conducted in a cardiosurgical ICU of a German university hospital. PATIENTS: We performed cardiac output measurements in 50 patients after cardiothoracic surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Three independent sets of three consecutive thermodilution measurements (i.e., PAC-CO) each were performed per patient, and AT-CO was measured simultaneously. The average of the three thermodilution cardiac output measurements was compared with the average of the corresponding three AT-CO values resulting in 150 paired cardiac output measurements. In 13 patients, cardiac output-modifying maneuvers performed for clinical reasons additionally allowed to evaluate trending ability. For statistical analysis, we used Bland-Altman analysis, the percentage error, four-quadrant plot, and concordance analysis. Mean PAC-CO was 4.7 ± 1.2 L/min and mean AT-CO was 4.9 ± 1.1 L/min. The mean of differences was -0.2 L/min with 95% limits of agreement of -1.8 to + 1.4 L/min. The percentage error was 34%. The concordance rate was 95%. CONCLUSIONS: Continuous cardiac output measurement using the noninvasive applanation tonometry technology is basically feasible in ICU patients after cardiothoracic surgery. The applanation tonometry technology provides cardiac output values with reasonable accuracy and precision of agreement compared with intermittent pulmonary artery thermodilution measurements in a clinical study setting and is able to reliably track cardiac output changes induced by cardiac output-modifying maneuvers.

Continuous noninvasive arterial pressure measurement using the volume clamp method: an evaluation of the CNAP device in intensive care unit patients.

The CNAP system allows continuous noninvasive arterial pressure measurement based on the volume clamp method using a finger cuff. We aimed to evaluate the agreement between arterial pressure measurements noninvasively obtained using the CNAP device and arterial catheter-derived arterial pressure measurements in intensive care unit patients. In 55 intensive care unit patients, we simultaneously recorded arterial pressure values obtained by an arterial catheter placed in the abdominal aorta through the femoral artery (criterion standard) and arterial pressure values determined noninvasively using CNAP. We performed Bland-Altman analysis and calculated the percentage error. The mean difference (±standard deviation, 95% limits of agreement, percentage error) between noninvasive (CNAP) and invasively assessed arterial pressure was for mean arterial pressure +1 mmHg (±9 mmHg, -16 to +19 mmHg, 22%), for systolic arterial pressure -10 mmHg (±16 mmHg, -42 to +21 mmHg, 27%), and for diastolic arterial pressure +7 mmHg (±9 mmHg, -10 to +24 mmHg, 28%). Our results indicate a reasonable accuracy and precision for the determination of mean and diastolic arterial pressure by noninvasive continuous arterial pressure measurements using the volume clamp method compared with the criterion standard (invasive arterial catheter). Systolic arterial pressure is determined less accurately and precisely.

Hemodynamic management of septic shock: is it time for "individualized goal-directed hemodynamic therapy" and for specifically targeting the microcirculation?

Septic shock is a life-threatening condition in both critically ill medical patients and surgical patients during the perioperative phase. In septic shock, specific alterations in global cardiovascular dynamics (i.e., the macrocirculation) and in the microcirculatory blood flow (i.e., the microcirculation) have been described. However, the presence and degree of microcirculatory failure are in part independent from systemic macrohemodynamic variables. Macrocirculatory and microcirculatory failure can independently induce organ dysfunction. We review current diagnostic and therapeutic approaches for the assessment and optimization of both the macrocirculation and the microcirculation in septic shock. There are various technologies for the determination of macrocirculatory hemodynamic variables. We discuss the data on early goal-directed therapy for the resuscitation of the macrocirculation. In addition, we describe the concept of "individualized goal-directed hemodynamic therapy." Technologies to assess the local microcirculation are also available. However, adequate resuscitation goals for the optimization of the microcirculation still need to be defined. At present, we are not ready to specifically monitor and target the microcirculation in clinical routine outside studies. In the future, concepts for an integrative approach for individualized hemodynamic management of the macrocirculation and in parallel the microcirculation might constitute a huge opportunity to define additional resuscitation end points in septic shock.

Radial artery applanation tonometry for continuous noninvasive arterial blood pressure monitoring in the cardiac intensive care unit.

BACKGROUND: Hemodynamic monitoring plays a pivotal role in the treatment of patients in the cardiac intensive care unit (CICU). The innovative radial artery applanation tonometry technology allows for continuous noninvasive arterial blood pressure (AP) measurement. By closing the gap between continuous invasive AP monitoring (arterial catheter) and intermittent noninvasive AP monitoring (oscillometry) this technology might improve CICU patient monitoring. We therefore aimed to evaluate the measurement performance of radial artery applanation tonometry in comparison with a radial arterial catheter in CICU patients. METHODS: In this prospective method comparison study, we simultaneously recorded AP noninvasively with radial artery applanation tonometry (T-line 200 pro device; Tensys Medical Inc., San Diego, CA, USA) and invasively with an arterial catheter (criterion standard) in 30 patients treated in the CICU of a German university hospital. We statistically analyzed 7,304 averaged 10-beat epochs of measurements of mean AP, systolic AP, and diastolic AP by using Bland-Altman analysis for repeated measurements. RESULTS: Our study revealed a mean difference ± standard deviation (95% limits of agreement; percentage error) between radial artery applanation tonometry and the criterion standard method (radial arterial catheter) of +2 ± 6 mmHg (-10 to +14 mmHg; 17%) for mean AP, -6 ± 11 mmHg (-28 to +15 mmHg; 20%) for systolic AP, and +4 ± 7 mmHg (-9 to +17 mmHg; 23%) for diastolic AP. CONCLUSIONS: In CICU patients, continuous noninvasive measurement of AP using radial artery applanation tonometry is feasible. The technology showed reasonable accuracy and precision in comparison with radial arterial catheter-derived AP values.

Measurement of blood pressure.

Blood pressure is overwhelmingly the most commonly measured parameter for the assessment of haemodynamic stability. In clinical routine in the operating theatre and in the intensive care unit, blood pressure measurements are usually obtained intermittently and non-invasively using oscillometry (upper-arm cuff method) or continuously and invasively with an arterial catheter. However, both the oscillometric method and arterial catheter-derived blood pressure measurements have potential limitations. A basic technical understanding of these methods is crucial in order to avoid unreliable blood pressure measurements and consequential treatment errors. In the recent years, technologies for continuous non-invasive blood pressure recording such as the volume clamp method or radial artery applanation tonometry have been developed and validated. The question in which patient groups and clinical settings these technologies should be applied to improve patient safety or outcome has not been definitively answered. In critically ill patients and high-risk surgery patients, further improvement of these technologies is needed before they can be recommended for routine clinical use.

The effects of transjugular intrahepatic portosystemic stent shunt on systemic cardiocirculatory parameters.

PURPOSE: We aimed to evaluate the effects of transjugular intrahepatic portosystemic stent shunt (TIPS) on systemic cardiocirculatory parameters in patients treated with TIPS for portal hypertension-associated complications. MATERIALS AND METHODS: This prospective study was conducted in an intensive care unit of a German university hospital (October 2010-July 2013). We assessed hemodynamic parameters before and after TIPS placement using single-indicator transpulmonary thermodilution and pulse contour analysis. After exclusion of 5 patients treated with vasoactive agents during study measurements, 15 patients were included in the final statistical analysis. RESULTS: Transjugular intrahepatic portosystemic stent shunt induced a statistically significant decrease in portal pressure (median, 29 [25%-75% percentile range, 23-37] mm Hg before TIPS vs 21 [18-27] mm Hg after TIPS; P<.01) in parallel with a statistically significant increase in central venous pressure (10 [6-15] mm Hg before TIPS vs 13 [9-16] mm Hg after TIPS; P=.01), cardiac index (3.8 [2.9-4.6] L min(-1) m(-2) before TIPS vs 4.5 [3.8-5.4] L min(-1) m(-2) 14 hours after TIPS; P=.01), and stroke volume index (54 [42-60] mL/m2 before TIPS vs 60 [47-63] mL/m2 14 hours after TIPS; P=.03). Arterial blood pressure and systemic vascular resistance index were statistically significantly lower after TIPS. CONCLUSIONS: Transjugular intrahepatic portosystemic stent shunt placement is associated with an increase in central venous pressure and an improvement of global blood flow (cardiac index and stroke volume index) in patients with portal hypertension.

Noninvasive continuous versus intermittent arterial pressure monitoring: evaluation of the vascular unloading technique (CNAP device) in the emergency department.

BACKGROUND: Monitoring cardiovascular function in acutely ill patients in the emergency department (ED) is of paramount importance. Arterial pressure (AP) is usually monitored using intermittent oscillometric measurements with an upper arm cuff. The vascular unloading technique (VUT) allows continuous noninvasive AP monitoring. In this study, we compare continuous AP measurements obtained by VUT with intermittent oscillometric AP measurements in ED patients. In addition, we aimed to investigate whether continuous noninvasive AP monitoring allows detection of relevant hypotensive episodes that might be missed with intermittent AP monitoring. METHODS: In a German university hospital, 130 ED patients who required AP monitoring were analyzed in this prospective method comparison study. Continuous AP monitoring was performed using VUT (CNAP technology; CNSystems Medizintechnik AG, Graz, Austria) over a 2-hour period. The oscillometric AP values were recorded simultaneously every 15 minutes for the comparison of both methods. For statistical evaluation, Bland-Altman plots accounting for repeated AP measurements per individual were used. RESULTS: The mean difference (±standard deviation) between AP measurements obtained by VUT and oscillometric AP measurements was -5 mmHg (±22 mmHg) for systolic AP (SAP), -2 mmHg (±15 mmHg) for diastolic AP (DAP), and -6 mmHg (±16 mmHg) for mean AP (MAP), respectively. In the interval between two oscillometric measurements, the VUT device detected hypotensive episodes (≥4 minutes) defined as either SAP <90 mmHg or MAP <65 mmHg in 30 patients and 16 patients, respectively. In 11 (SAP <90 mmHg) and 6 (MAP <65 mmHg) of these patients, hypotension was also detected by the subsequent intermittent oscillometric AP measurement. CONCLUSIONS: VUT using the CNAP system for noninvasive continuous AP measurement shows reasonable agreement with intermittent oscillometric measurements in acutely ill ED patients. Continuous AP monitoring allows immediate recognition of clinically relevant hypotensive episodes, which are missed or only belatedly recognized with intermittent AP measurement.

Evaluation of a dosing regimen for continuous vancomycin infusion in critically ill patients: an observational study in intensive care unit patients.

PURPOSE: We aimed to evaluate a dosing algorithm for continuous vancomycin administration in intensive care unit patients. MATERIALS AND METHODS: This observational study was conducted in a medical intensive care unit (German university hospital; June 2012-February 2013). Following a loading dose of 20 mg per kg actual body weight, vancomycin was administered continuously (20 or 30 mg of vancomycin per kg actual body weight over 24 hours depending on renal function). The vancomycin infusion rate was adjusted to achieve a target serum vancomycin concentration of 20-30 mg/L. RESULTS: Vancomycin was administered for a median (interquartile range) of 7 (5-9) days. The median vancomycin dose given as an initial bolus was 1750 (1400-2000) mg. The median daily vancomycin dose ranged from 480 (180-960) mg (day 6) to 3.120 (2596-3980) mg (day 1). Altogether, the achieved median serum vancomycin concentration was 29.0 (25.2-33.2) mg/L. On treatment days 1 to 7, we observed target serum vancomycin levels (20-30 mg/L) in 48%, 39%, 33%, 26%, 43%, 57%, and 69% of patients. Supra-therapeutic serum vancomycin concentrations (>30 mg/L) were observed in 36%, 52%, 61%, 63%, 39%, 19%, and 15% of patients on treatment days 1 to 7. CONCLUSIONS: The evaluated vancomycin dosing regimen for continuous infusion allowed rapid achievement of sufficient vancomycin serum levels. However, we frequently observed supra-therapeutic serum vancomycin concentrations in the first days of vancomycin treatment.

An autocalibrating algorithm for non-invasive cardiac output determination based on the analysis of an arterial pressure waveform recorded with radial artery applanation tonometry: a proof of concept pilot analysis.

We aimed to describe and evaluate an autocalibrating algorithm for determination of cardiac output (CO) based on the analysis of an arterial pressure (AP) waveform recorded using radial artery applanation tonometry (AT) in a continuous non-invasive manner. To exemplarily describe and evaluate the CO algorithm, we deliberately selected 22 intensive care unit patients with impeccable AP waveforms from a database including AP data obtained with AT (T-Line system; Tensys Medical Inc.). When recording AP data for this prospectively maintained database, we had simultaneously noted CO measurements obtained from just calibrated pulse contour analysis (PiCCO system; Pulsion Medical Systems) every minute. We applied the autocalibrating CO algorithm to the AT-derived AP waveforms and noted the computed CO values every minute during a total of 15 min of data recording per patient (3 × 5-min intervals). These 330 AT-derived CO (AT-CO) values were then statistically compared to the corresponding pulse contour CO (PC-CO) values. Mean ± standard deviation for PC-CO and AT-CO was 7.0 ± 2.0 and 6.9 ± 2.1 L/min, respectively. The coefficient of variation for PC-CO and AT-CO was 0.280 and 0.299, respectively. Bland-Altman analysis demonstrated a bias of +0.1 L/min (standard deviation 0.8 L/min; 95% limits of agreement -1.5 to 1.7 L/min, percentage error 23%). CO can be computed based on the analysis of the AP waveform recorded with AT. In the selected patients included in this pilot analysis, a percentage error of 23% indicates clinically acceptable agreement between AT-CO and PC-CO.

Evaluation of the radial artery applanation tonometry technology for continuous noninvasive blood pressure monitoring compared with central aortic blood pressure measurements in patients with multiple organ dysfunction syndrome.

PURPOSE: We compared blood pressure (BP) measurements obtained using radial artery applanation tonometry with invasive BP measurements using a catheter placed in the abdominal aorta through the femoral artery in patients with multiple organ dysfunction syndrome (MODS). MATERIALS AND METHODS: In 23 intensive care unit patients with MODS, we simultaneously assessed BP values for 15 minutes per patient using radial artery applanation tonometry (T-Line TL-200 pro device; Tensys Medical Inc, San Diego, Calif) and the arterial catheter (standard-criterion technique). A total of 2879 averaged 10-beat epochs were compared using Bland-Altman plots. RESULTS: The mean difference ± SD (with corresponding 95% limits of agreement) between radial artery applanation tonometry-derived BP and invasively assessed BP was +1.0 ± 5.5 mm Hg (-9.9 to +11.8 mm Hg) for mean arterial pressure, -3.3 ± 11.2 mm Hg (-25.3 to +18.6 mm Hg) for systolic arterial pressure, and +4.9 ± 7.0 mm Hg (-8.8 to +18.6 mm Hg) for diastolic arterial pressure, respectively. CONCLUSIONS: In intensive care unit patients with MODS, mean arterial pressure and diastolic arterial pressure can be determined accurately and precisely using radial artery applanation tonometry compared with central aortic values obtained using a catheter placed in the abdominal aorta through the femoral artery. Although systolic arterial pressure could also be derived accurately, wider 95% limits of agreement suggest lower precision for determination of systolic arterial pressure.