Pressure recording analytical method (PRAM) for measurement of cardiac output during various haemodynamic states

Comparison of noninvasive cardiac output monitoring by electrical cardiometry with transthoracic echocardiography in postoperative paediatric cardiac surgical patients - A prospective observational study

Aim

The present study was conducted to validate cardiac output (CO) and cardiac index (CI) obtained from electrical cardiometry (EC) ICON ® with transthoracic echocardiography (TTE) in postoperative pediatric cardiac surgical patients.

Materials and Methods

A prospective observational study was conducted in 25 pediatric patients with age < 10 years who underwent elective cardiac surgery.

Data Analysis

BlandAltman plot was constructed for interchangeability and Polar plot was constructed to know trending ability.

Results

A total of 250 datasets were analyzed. Spearman's correlation coefficient for CO between ICON ® and TTE showed good positive correlation (r = 0.850, 95% confidence interval 0.81 to 0.881, P <.0001). Moderate positive correlation was observed between ICON ® and TTE for CI (r = 0.60, 95% confidence interval 0.515 to 0.674, P <.0001). Linear regression equations for CO and CI between ICON ® and TTE were: y = 0.5230 + 0.8078 X (R2 = 0.6597, P <.001) and y = 1.8350 + 0.5869 X (R2 = 0.3985, P <.001) [y- ICON ®; X - TTE], respectively. BlandAltman plot for CO between ICON ® and TTE showed a bias of 0.3012 with limits of agreement (LOA) being -0.69 to 1.3 and for CI bias was 0.6939 with LOA-2.1 to 3.5. Polar plot analysis showed an angular bias of 8.1750, with radial LOA being -13.74° to 30.08° for CO and angular bias of 6.6931, with radial LOA being -15.69° to 29.07° for CI.

Conclusion

ICON ® monitor-derived parameters are not interchangeable with the values derived from TTE. However, the ICON ® monitor demonstrated a good trending ability for both CO and CI.

Comparision of cardiac output measured by transthoracic echocardiography with continuous cardiac output measured by pressure recording analytical method

Background

Low cardiac output is a common complication following cardiac surgery and it is associated with higher mortality in the pediatric population. A gold standard method for cardiac output (CO) monitoring in the pediatric population is lacking. The present study was conducted to validate cardiac output and cardiac index measured by transthoracic echocardiography and Pressure recording analytical method, a continuous pulse contour method, MostCareUp in postoperative pediatric cardiac surgical patients.

Materials and Methods

This was a prospective observational clinical study conducted at a tertiary care hospital. A total of 23 pediatric patients weighed between 2 and 20 kg who had undergone elective cardiac surgery were included in the study.

Results

Spearman's correlation coefficient of CO between transthoracic echocardiography (TTE) and Pressure Recording Analytical Method (PRAM) showed of positive correlation (r = 0.69, 95% Confidence interval 0.59-0.77, P < 0.0001) Linear regression equations for CO between TTE and PRAM were y = 0.55 + 0.88x (R2 = 0.46, P < 0.0001). (y = PRAM, x = TTE), respectively. Bland- Altman plot for CO between TTE and PRAM showed a bias of -0.397 with limits of the agreement being -2.01 to 1.22. Polar plot analysis showed an angular bias of 6.55° with radial limits of the agreement being -21.46 to 34.58 for CO and angular bias of 6.22° with radial limits of the agreement being -22.4 to 34.84 for CI.

Conclusion

PRAM has shown good trending ability for cardiac output. However, values measured by PRAM are not interchangeable with the values measured by transthoracic echocardiography.

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.

Cardiac Output Evaluation on Septic Shock Patients: Comparison between Calibrated and Uncalibrated Devices during Vasopressor Therapy

There are no reliable, non-invasive methods to accurately measure cardiac output (CO) in septic patients. MostCare (Vytech Health™, Vygon, Padova, Italy), is a beat-to-beat, self calibrated method for CO measurement based on continuous analysis of reflected arterial pressure waveforms. We enrolled 40 patients that were suffering from septic shock and requiring norepinephrine infusion to target blood pressure in order to to evaluate the level of agreement between a calibrated transpulmonary thermodilution device (PiCCO System, Pulsion Medical Systems, Feldkirchen, Germany) and the MostCare system in detecting and tracking changes in CO measurements related to norepinephrine reduction in septic shock patients,. PiCCO was connected to a 5 Fr femoral artery catheter and to a central venous catheter. System calibration was performed with 15 mL of cold saline injection over about 3 s. The MostCare device was connected to the artery catheter to analyze the arterial waveform. Before reducing norepinephrine infusion, the PiCCO system was calibrated, the MostCare waveform was optimized, and the values of the complete hemodynamic profile were recorded (T1). Norepinephrine infusion was then reduced by 0.03 mcg/Kg/min. After 30 min, a new calibration of PiCCO system and a new record on both monitors were performed (T2). Static measurements agreements were assessed using the Bland-Altman test, while trending ability was investigated using polar plot analysis. If volume expansion occurred, then related data were separately analyzed. At T1 mean the CO was 5.38 (SD 0.60) L/min, the mean difference was 0.176 L/min, the limits of agreement (LoA) was +1.39 and -1.04 L/min, and the percentage error (PE) was 22.6%; at T2 the mean CO was 5.44 (SD 0.73) L/min, the mean difference was 0.053 L/min, the LoA was +1.51 and -1.40, and the PE was 27%. After considering the volume expansion between T1 and T2, the mean CO at T1 was 5.39 L/min (SD 0.47), the LoA was +1.09 and -0.78 L/min, and the percentage error (PE) was 17%; at T2 the mean CO was 5.35 L/min (SD 0.81), the LoA was +1.73 and -1.52 L/min, and the PE was 30%. The polar plot diagram seems to confirm the trending ability of MostCare system versus the reference method. In septic patients, when the arterial waveform is accurate, MostCare and PiCCO transpulmonary thermodilution exhibit good agreement even after the reduction of norepinephrine and changes in vascular tone or volume expansion. MostCare could be a rapid to set, reliable, and useful tool to monitor hemodynamic variations in septic patients in emergency contexts where thermodilution methods or other advanced systems are not easily available.

Prediction of Fluid Responsiveness by Stroke Volume Variation in Children Undergoing Fontan Operation

Background

Fontan operation is a palliative medical procedure performed on children with single-ventricle defects. As postoperative success of the procedure largely depends on the preload volume, it is necessary to maintain an appropriate pressure gradient between the systemic vein and the left atrium to ensure the effective volume of systemic circulation. However, there is a lack of effective indexes to evaluate fluid responsiveness in Fontan patients. Stroke volume variation (SVV) is a dynamic hemodynamic parameter based on cardiopulmonary interaction in mechanical ventilation. This study is aimed at validating the sensitivity and specificity of SVV and central venous pressure (CVP) in assessing the fluid responsiveness of Fontan patients.

Method

Sixty-four children with single ventricle who underwent modified Fontan operation between May 2018 and January 2020 were included in this study. Patients were administered 10 ml·kg⁻¹ albumin for fluid challenge within 10 min after cardiopulmonary bypass. Before and after fluid challenge, the invasive arterial pressure module was connected to MostCare™ equipment to collect the cardiac index (CI) and SVV dynamically in a time window of 30 s at a frequency of 1000 Hz. According to the range of CI change, patients with ΔCI ≥ 15% were classified into the responder (R) group and those with ΔCI < 15% into the nonresponder (NR) group. Using SVV and CVP as indicators, the receiver operating characteristic (ROC) curve of the patients was established, and the area under curve (AUC), diagnostic threshold, sensitivity, and specificity were calculated.

Results

The SVV values were 16.28% (25th and 75th percentiles 14.17%-19.24%) and 13.68% (25th and 75th percentiles 12.90%-15.89%) before and after fluid challenge treatment in responders, respectively, and the values were 18.60 ± 1.83 mmHg before and 20.20 ± 2.39 mmHg for CVP after treatment. The AUC of SVV was 0.74 (95% confidence interval (CI) 0.54-0.94, P < 0.05), and the cutoff value was 16%, offering a sensitivity of 50% and a specificity of 91.7%. Meanwhile, the AUC of CVP was 0.70 (95% CI 0.50-0.92, P > 0.05), and the cutoff value was 19.5 mmHg, offering a sensitivity of 58% and a specificity of 76%.

Conclusion

SVV exhibited a good predictive value for fluid responsiveness in pediatric Fontan patients. Appropriate fluid therapy according to SVV could improve the cardiac function of such patients. Trial registration. This study was registered in Chinese Clinical Trail Registry on Jan 26, 2018. Registration number is ChiCTR1800014654. Registry URL is http://www.chictr.org.cn/showproj.aspx?proj=25019. This observational prospective study was approved by the Local Ethics Committee of Shanghai Children's Medical Center affiliated to Shanghai Jiao Tong University (SCMCIRB-K2017035).

To Swan or Not to Swan: Indications, Alternatives, and Future Directions

The pulmonary artery catheter (PAC) has revolutionized bedside assessment of preload, afterload, and contractility using measured pulmonary capillary wedge pressure, calculated systemic vascular resistance, and estimated cardiac output. It is placed percutaneously by a flow-directed balloon-tipped technique through the venous system and the right heart to the pulmonary artery. Interest in the hemodynamic variables obtained from PACs paved the way for the development of numerous less-invasive hemodynamic monitors over the past 3 decades. These devices estimate cardiac output using concepts such as pulse contour and pressure analysis, transpulmonary thermodilution, carbon dioxide rebreathing, impedance plethysmography, Doppler ultrasonography, and echocardiography. Herein, the authors review the conception, technologic advancements, and modern use of PACs, as well as the criticisms regarding the clinical utility, reliability, and safety of PACs. The authors comment on the current understanding of the benefits and limitations of alternative hemodynamic monitors, which is important for providers caring for critically ill patients. The authors also briefly discuss the use of hemodynamic monitoring in goal-directed fluid therapy algorithms in Enhanced Recovery After Surgery programs.

Superior mesenteric and renal flow patterns during intra-aortic counterpulsation

NEW FINDINGS

What is the central question of this study? Visceral ischaemia is one of the most feared complications during use of an intra-aortic balloon pump. Using an animal model, we measured the flows at the abdominal level directly and examined flow patterns to enable investigation of flow patterns during the use of the intra-aortic balloon pump. What is the main finding and its importance? We show that there is a significant balloon-related reduction in superior mesenteric flow in both early and mid-diastole.

ABSTRACT

A number of previous studies have shown that blood flow in the visceral arteries is altered during intra-aortic balloon pump (IABP) treatment. We used a porcine model to analyse the pattern of blood flow into the visceral arteries during IABP use. For this purpose, we measured the superior mesenteric, right renal and left renal flows before and during IABP support, using surgically placed flowmeters surrounding these visceral arteries. The superior mesenteric flow significantly decreased in early diastole (P < 0.001) and in mid-diastole (P = 0.003 versus early diastole), whereas in late diastole it increased again (P < 0.001 versus mid-diastole). During systole, the flow was not significantly increased compared with late diastole (P = 0.51), but it was significantly lower than at baseline (both P < 0.001). Flows did not differ between right and left kidneys. Perfusion of either kidney did not change significantly in early diastole (P > 0.05), whereas it decreased significantly in mid-diastole (P < 0.001), rising dramatically in late diastole (P < 0.001) and with an additional slight increase in systole (P = 0.054). This study provides important insights into abdominal flows during intra-aortic pump counterpulsation. Furthermore, it supports the need to rethink the balloon design to avoid visceral ischaemia during circulatory assistance.

Comparison between Pressure Recording Analytical Method and Fick Method to Measure Cardiac Output in Pediatric Cardiac Surgery

Background:

There is an increased interest in methods of objective cardiac output measurement in pediatric cardiac surgery. Several techniques are available, but have limitations, among the new technologies pressure recording analytical method with MostCare (MostCare-PRAM), a minimally invasive hemodynamic monitoring system, represents a novel arterial pulse contour method that does not require calibration. For this reason, we compared the MostCare-PRAM vs the Fick method for estimation of cardiac output.

Methods:

We studied prospectively 13 pediatric patients who underwent cardiac surgery and compared intraoperatively Cardiac Index (CI) measured with the MostCare-PRAM with the CI measured with the Fick method. We also measured Cardiac Cycle Efficiency (CCE) and maximal arterial pressure/time ratio (dp/dt max) and compared with Fick method.

Results:

The data showed good agreement between CI Fick and CI MostCare-PRAM (r = 0.93 and R2= 0.86; p < 0.0001) and also between CCE (r = 0.82 and R2 = 0.67; p < 0.001) and dp/dt (r = 0.84; R2 = 0.81; p < 0.001) with CI measured with Fick method.

Conclusion:

In pediatric patients submitted to cardiac surgery, the MostCare-PRAM seems to estimate CI with a good level of agreement with the Fick method measurements.

Cardiac Output Monitoring by Pulse Contour Analysis, the Technical Basics of Less-Invasive Techniques

Routine use of cardiac output (CO) monitoring became available with the introduction of the pulmonary artery catheter into clinical practice. Since then, several systems have been developed that allow for a less-invasive CO monitoring. The so-called “non-calibrated pulse contour systems” (PCS) estimate CO based on pulse contour analysis of the arterial waveform, as determined by means of an arterial catheter without additional calibration. The transformation of the arterial waveform signal as a pressure measurement to a CO as a volume per time parameter requires a concise knowledge of the dynamic characteristics of the arterial vasculature. These characteristics cannot be measured non-invasively and must be estimated. Of the four commercially available systems, three use internal databases or nomograms based on patients’ demographic parameters and one uses a complex calculation to derive the necessary parameters from small oscillations of the arterial waveform that change with altered arterial dynamic characteristics. The operator must ensure that the arterial waveform is neither over- nor under-dampened. A fast-flush test of the catheter–transducer system allows for the evaluation of the dynamic response characteristics of the system and its dampening characteristics. Limitations to PCS must be acknowledged, i.e., in intra-aortic balloon-pump therapy or in states of low- or high-systemic vascular resistance where the accuracy is limited. Nevertheless, it has been shown that a perioperative algorithm-based use of PCS may reduce complications. When considering the method of operation and the limitations, the PCS are a helpful component in the armamentarium of the critical care physician.

A preliminary study evaluating cardiac output measurement using Pressure Recording Analytical Method (PRAM) in anaesthetized dogs

Background

Haemodynamic variations normally occur in anaesthetized animals, in relation to the animal status, administered drugs, sympathetic and parasympathetic tone, fluid therapy and surgical stimulus. The possibility to measure some cardiovascular parameters, such as cardiac output (CO), during anaesthesia would be beneficial for both the anaesthesia management and its outcome. New techniques for the monitoring of CO are aimed at finding methods which are non invasive, accurate and with good trending ability, which can be used in a clinical setting. The aim of this study was to compare the Pressure Recording Analytical Method (PRAM) with the pulmonary artery thermodilution (TD) for the measurement of cardiac output in 6 anaesthetized critically ill dogs.

Results

Fifty-four pairs of CO measurements were obtained with a median (range) of 3.33 L/min (0.81–7.21) for PRAM-CO and 3.48 L/min (1.41–6.56) for TD-CO. The Bland-Altman analysis showed a mean bias of 0.17 L/min with limits of agreement (LoA) of − 0.46 to 0.81 L/min. The percentage error resulted 18.2%. The 4-quadrant plot analysis showed an acceptable concordance (93%) between the 2 methods. The polar plot showed a good trending ability with the mean angular bias of 3.9° and radial LoA ± 12.1°.

Conclusions

The PRAM resulted in good precision, acceptable concordance and good trending ability for the measure of CO in the anaesthetized dog, representing a promising alternative to thermodilution for the measurement of CO. Among all the pulse contour methods available on the market it is the only one that does not require any calibration or adjustment of the measurement. Further studies are required to verify the ability of this method to accurately measure cardiac output even during unstable hemodynamic conditions.

Pulse contour analysis of arterial waveform in a high fidelity human patient simulator

The measurement of cardiac output (CO) may be useful to improve the assessment of hemodynamics during simulated scenarios. The purpose of this study was to evaluate the feasibility of introducing an uncalibrated pulse contour device (MostCare, Vytech, Vygon, Padova, Italy) into the simulation environment. MostCare device was plugged to a clinical monitor and connected to the METI human patient simulator (HPS) to obtain a continuous arterial waveform analysis and CO calculation. In six different simulated clinical scenarios (baseline, ventricular failure, vasoplegic shock, hypertensive crisis, hypovolemic shock and aortic stenosis), the HPS-CO and the MostCare-CO were simultaneously recorded. The level of concordance between the two methods was assessed by the Bland and Altman analysis. 150-paired CO values were obtained. The HPS-CO values ranged from 2.3 to 6.6 L min^-1 and the MostCare-CO values from 2.8 to 6.4 L min^-1. The mean difference between HPS-CO and MostCare-CO was - 0.3 L min^-1 and the limits of agreement were - 1.5 and 0.9 L min^-1. The percentage of error was 23%. A good correlation between HPS-CO and MostCare-CO was observed in each scenario of the study (r = 0.88). Although MostCare-CO tended to underestimate the CO over the study period, good agreements were found between the two methods. Therefore, a pulse contour device can be integrated into the simulation environment, offering the opportunity to create new simulated clinical settings.

A System for Continuous Estimating and Monitoring Cardiac Output via Arterial Waveform Analysis

BACKGROUND

Cardiac output (CO) is the total volume of blood pumped by the heart per minute and is a function of heart rate and stroke volume. CO is one of the most important parameters for monitoring cardiac function, estimating global oxygen delivery and understanding the causes of high blood pressure. Hence, measuring CO has always been a matter of interest to researchers and clinicians. Several methods have been developed for this purpose, but a majority of them are either invasive, too expensive or need special expertise and experience. Besides, they are not usually risk free and have consequences.

OBJECTIVE

Here, a semi-invasive system was designed and developed for continuous CO measurement via analyzing and processing arterial pulse waves.

RESULTS

Quantitative evaluation of developed CO estimation system was performed using 7 signals. It showed that it has an acceptable average error of (6.5%) in estimating CO. In addition, this system has the ability to consistently estimate this parameter and to provide a CO versus time curve that assists in tracking changes of CO. Moreover, the system provides such curve for systolic blood pressure, diastolic blood pressure, average blood pressure, heart rate and stroke volume.

CONCLUSION

Evaluation of the results showed that the developed system is capable of accurately estimating CO. The curves which the system provides for important parameters may be valuable in monitoring hemodynamic status of high-risk surgical patients and critically ill patients in Intensive Care Units (ICU). Therefore, it could be a suitable system for monitoring hemodynamic status of critically ill patients.

Hemodynamic monitoring in the critically ill: an overview of current cardiac output monitoring methods

Critically ill patients are often hemodynamically unstable (or at risk of becoming unstable) owing to hypovolemia, cardiac dysfunction, or alterations of vasomotor function, leading to organ dysfunction, deterioration into multi-organ failure, and eventually death. With hemodynamic monitoring, we aim to guide our medical management so as to prevent or treat organ failure and improve the outcomes of our patients. Therapeutic measures may include fluid resuscitation, vasopressors, or inotropic agents. Both resuscitation and de-resuscitation phases can be guided using hemodynamic monitoring. This monitoring itself includes several different techniques, each with its own advantages and disadvantages, and may range from invasive to less- and even non-invasive techniques, calibrated or non-calibrated. This article will discuss the indications and basics of monitoring, further elaborating on the different techniques of monitoring.

Pulse wave analysis to assess systemic blood flow during mechanical biventricular support

Measurement of systemic blood flow is of crucial importance in patients on mechanical circulatory support (MCS). We reported the case of a 65-year-old female patient in severe cardiogenic shock undergoing left (Jarvik 2000 axial flow pump) and right (Levitronix-Centrimag centrifugal pump) ventricular assist device implant. Evaluation of blood flow was obtained by ultrasonic flowmetry, continuous thermodilution technique, and pressure recording analytical method (PRAM). This pulse contour system allows beat-by-beat systemic blood flow assessment from the analysis of radial artery pressure waveform. At a Jarvik pump speed ≤ 10 000 rotations per minutes (rpm), thermodilution and PRAM showed similar blood flow values. At a Jarvik pump speed ≥11 000 rpm, the aortic valve did not open and PRAM did not provide blood flow values due to nonpulsatile blood flow. The present paper describes the first experience with PRAM in a single patient on MCS. Further studies are required to assess the validity of PRAM as an additional monitoring system in the setting of ventricular assist device support. Perfusion (2007) 22, 63-66.

Comparison between pressure-recording analytical method (PRAM) and femoral arterial thermodilution method (FATD) cardiac output monitoring in an infant animal model of cardiac arrest

Background

The pressure-recording analytical method is a new semi-invasive method for cardiac output measurement (PRAM). There are no studies comparing this technique with femoral artery thermodilution (FATD) in an infant animal model.

Methods

A prospective study was performed using 25 immature Maryland pigs weighing 9.5 kg. Fifty-eight simultaneous measurements of cardiac index (CI) were made by FATD and PRAM at baseline and after return of spontaneous circulation. Differences, correlation, and concordance between both methods were analyzed. The ability of PRAM to track changes in CI was explored with a polar plot.

Results

Mean CI measurements were 4.5 L/min/m² (95 % CI, 4.2–4.8 L/min/m²; coefficient of variation, 27 %) by FATD and 4.0 L/min/m² (95 % CI, 3.6–4.3 L/min/m²; coefficient for variation, 37 %) by PRAM (difference, 0.5 L/min/m²; 95 % CI for the difference, 0.1–1.0 L/min/m²; p = 0.003; n = 58). No correlation between both methods was observed (r = 0.170, p = 0.20). Limits of agreement were −2.9 to 4.0 L/min/m² (−69.9 to 84.9 %). Percentage error was 80.6 %. Only 26.1 % of data points lied within an absolute deviation of ±30° from the polar axis.

Conclusions

No correlation nor concordance between both methods was observed. Limits of agreement and percentage of error were high and clinically not acceptable. No concurrence between both methods in CI changes was observed. PRAM is not a useful method for measurement of the CI in this pediatric model of cardiac arrest.

Shape analysis of the microcirculatory flow wave

The cardiovascular system and its alterations are a crucial aspect of physiology and medicine. Non-invasive assessment of the functional properties of circulation is of considerable interest to clinicians and physiologists. In this work we investigate the possibility of detecting alterations of the flow waveform in microcirculation, using non-invasive measurements based on a laser Doppler flowmeter. As a test case, we focus on the effect of ageing. Skin is warmed up to a fixed temperature (44 °C) during measurement, to increase blood flow. The shape of the perfusion waveform during each heart beat after the flow was stabilized was used to estimate dynamic parameters of the microcirculatory system. Both the wave rise time, defined as the delay between the diastolic minimum and the following systolic maximum, and the oscillation fraction, defined as the normalized difference between the maximum and minimum flow, present significant variation with age.

Pressure recording analytical method and bioreactance for stroke volume index monitoring during pediatric cardiac surgery

BACKGROUND

It is currently uncertain which hemodynamic monitoring device reliably measures stroke volume and tracks cardiac output changes in pediatric cardiac surgery patients.

OBJECTIVE

To evaluate the difference between stroke volume index (SVI) measured by pressure recording analytical method (PRAM) and bioreactance and their ability to track changes after a therapeutic intervention.

METHODS

A single-center prospective observational cohort study in children undergoing cardiac surgery with cardiopulmonary bypass (CPB) was conducted. Twenty children below 20 kg with median (interquartile range) weight of 5.3 kg (4.1-7.8) and age of 6 months (3-20) were enrolled. Data were collected after anesthesia induction, at the end of CPB, before fluid administration and after fluid administration. Overall, median-IQR PRAM SVI values (23 ml·m(-2), 19-27) were significantly higher than bioreactance SVI (15 ml·m(-2), 12-25, P = 0.0001). Correlation (r(2) ) between the two methods was 0.15 (P = 0.0003). The mean difference between the measurements (bias) was 5.7 ml·m(-2) with a standard deviation of 9.6 (95% limits of agreement ranged from -13 to 24 ml·m(-2)). Percentage error was 91.7%. Baseline SVI appeared to be similar, but PRAM SVI was systematically greater than bioreactance thereafter, with the highest gap after the fluid loading phase: 13 (12-18) ml·m(-2) vs. 23 (19-25) ml·m(-2), respectively, P = 0.0013. A multivariable regression model showed that a significant independent inverse correlation with patients' body weight predicted the CI difference between the two methods after fluid challenge (β coefficient -0.12, P = 0.013).

CONCLUSIONS

Pressure recording analytical method and bioreactance provided similar SVI estimation at stable hemodynamic conditions, while bioreactance SVI values appeared significantly lower than PRAM at the end of CPB and after fluid replacement.

Measurement of cardiac output in children by pressure-recording analytical method

We evaluated two pressure-recording analytical method (PRAM) software versions (v.1 and v.2) to measure cardiac index (CI) in hemodynamically stable critically ill children and investigate factors that influence PRAM values. The working hypothesis was that PRAM CI measurements would stay within normal limits in hemodynamically stable patients. Ninety-five CI PRAM measurements were analyzed in 47 patients aged 1-168 months. Mean CI was 4.1 ± 1.4 L/min/m(2) (range 2.0-7.0). CI was outside limits defined as normal (3-5 L/min/m(2)) in 53.7% of measurements (47.8% with software v.1 and 69.2% with software v.2, p = 0.062). Moreover, 14.7% of measurements were below 2.5 L/min/m(2), and 13.6% were above 6 L/min/m(2). CI was significantly lower in patients with a clearly visible dicrotic notch than in those without (3.7 vs. 4.6 L/min/m(2), p = 0.004) and in children with a radial arterial catheter (3.5 L/min/m(2)) than in those with a brachial (4.4 L/min/m(2), p = 0.021) or femoral catheter (4.7 L/min/m(2), p = 0.005). By contrast, CI was significantly higher in children under 12 months (4.2 vs. 3.6 L/min/m(2), p = 0.034) and weighing under 10 kg (4.2 vs. 3.6 L/min/m(2), p = 0.026). No significant differences were observed between cardiac surgery patients and the rest of children. A high percentage of CI measurements registered by PRAM were outside normal limits in hemodynamically stable, critically ill children. CI measured by PRAM may be influenced by the age, weight, location of catheter, and presence of a dicrotic notch.

Relationship between pulse pressure variation and echocardiographic indices of left ventricular filling pressure in critically ill patients

BACKGROUND

Pulse pressure variation (PPV) is a dynamic index of fluid responsiveness. This parameter helps clinicians in improving haemodynamic status while avoiding potential fluid overload. Echocardiographic indices, such as E/E' ratio and left atrial (LA) strain by speckle tracking echocardiography (STE), are used to estimate left ventricular (LV) filling pressures. This study aimed at exploring the relationship between PPV and echocardiographic indices of LV filling pressures in critically ill patients.

METHODS

Twenty-two patients (mean age of 50.9 ± 21.6, male/female = 15/7) admitted to intensive care unit, and requiring mechanical ventilation and invasive arterial pressure monitoring, were studied. In all patients, two independent operators assessed simultaneously PPV, using a pulse contour method, mean E/E' ratio and peak atrial longitudinal strain (PALS) by means of STE. PALS values were obtained by averaging LA segments measured in the 4-chamber and 2-chamber views (global PALS).

RESULTS

A significant negative correlation was found between mean E/E' ratio and PPV (R(2) = -0.76; P<0.001). A positive correlation between global PALS and PPV was found (R(2) = 0.80, P<0.001). Mean global PALS of 26.2% demonstrated excellent accuracy (Area Under Roc Curve = 0.86, P<0.001), and good sensitivity (92%) and specificity (86%) in predicting a PPV >15%.

CONCLUSION

In a group of mechanically ventilated patients PPV, derived from pulse contour analysis, and echocardiographic preload parameters were well correlated. Global PALS by STE provided better estimation of PPV than mean E/E' ratio. PALS seems a potential alternative to PPV in assessing fluid responsiveness in critically ill patients.

Cardiovascular effects of mild hypothermia in post-cardiac arrest patients by beat-to-beat monitoring. A single centre pilot study

BACKGROUND

Data on the hemodynamic and cardiovascular effects of hypothermia in patients with cardiac arrest are scarce. The aim of this study was to evaluate the hemodynamic changes induced by hypothermia by means of Most Care(®) (pressure recording analytical method, PRAM methodology), a beat-to-beat hemodynamic monitoring method.

METHODS

We enrolled 20 patients with cardiac arrest (CA) consecutively admitted to our intensive cardiac care unit and treated with mild hypothermia (TH).

RESULTS

While non-survivors showed no changes in haemodynamic variables throughout the study period, survivors exhibited a significant increase in systemic vascular resistance indexed during hypothermia and a trend towards lower values of heart rate and higher levels of mean arterial pressure.

CONCLUSIONS

According to our data, PRAM methodology proved to be a feasible and clinically useful tool in CA patients treated with TH since it provides continuous beat-to-beat haemodynamic monitoring that is based on assessment of several haemodynamic variables. Moreover, we observed that survivors showed a different haemodynamic behaviour during hypothermia in respect to patients who died. However, further studies, performed in larger cohorts, are needed to better elucidate the haemodynamic effects of hypothermia in CA patients by means of PRAM methodology.

Semi-invasive measurement of cardiac output based on pulse contour: a review and analysis

PURPOSE

The aim of this review was to provide a meta-analysis of all five of the most popular systems for arterial pulse contour analysis compared with pulmonary artery thermodilution, the established reference method for measuring cardiac output (CO). The five investigated systems are FloTrac/Vigileo(®), PiCCO(®), LiDCO/PulseCO(®), PRAM/MostCare(®), and Modelflow.

SOURCE

In a comprehensive literature search through MEDLINE(®), Web of Knowledge (v.5.11), and Google Scholar, we identified prospective studies and reviews that compared the pulse contour approach with the reference method (n = 316). Data extracted from the 93 selected studies included range and mean cardiac output, bias, percentage error, software versions, and study population. We performed a pooled weighted analysis of their precision in determining CO in various patient groups and clinical settings.

PRINCIPAL FINDINGS

Results of the majority of studies indicate that the five investigated systems show acceptable accuracy during hemodynamically stable conditions. Forty-three studies provided adequate data for a pooled weighted analysis and resulted in a mean (SD) total pooled bias of -0.28 (1.25) L·min(-1), percentage error of 40%, and a correlation coefficient of r = 0.71. In hemodynamically unstable patients (n = 8), we found a higher percentage error (45%) and bias of -0.54 (1.64) L·min(-1).

CONCLUSION

During hemodynamic instability, CO measurement based on continuous arterial pulse contour analysis shows only limited agreement with intermittent bolus thermodilution. The calibrated systems seem to deliver more accurate measurements than the auto-calibrated or the non-calibrated systems. For reliable use of these semi-invasive systems, especially for critical therapeutic decisions during hemodynamic disorders, both a strategy for hemodynamic optimization and further technological improvements are necessary.

Thermodilution vs pressure recording analytical method in hemodynamic stabilized patients

PURPOSE

Many mini-invasive devices to monitor cardiac output (CO) have been introduced and, among them, the pressure recording analytical method (PRAM). The aim of this study was to assess the agreement of PRAM with the intermittent transpulmonary thermodilution and continuous pulmonary thermodilution in measuring CO in hemodynamically stabilized patients.

MATERIALS AND METHODS

This is a prospective clinical study in a mixed medical-surgical intensive care unit (ICU) and in a postcardiac surgical ICU. Forty-eight patients were enrolled: 32 patients to the medical-surgical ICU monitored with PiCCO (Pulsion Medical System AG, Munich, Germany) and 16 were cardiac patients monitored with Vigilance (Edwards Lifesciences, Irvine, CA).

RESULTS

A total of 112 measurements were made. Ninety-six comparisons of paired CO measurements were made in patients hospitalized in medical-surgical ICU; 16, in cardiac surgical patients. The mean Vigilance-CO was 4.49 ± 0.99 L/min (range, 2.80-5.90 L/min), and the mean PRAM-CO was 4.27 ± 0.88 L/min (range, 2.85-6.19 L/min). The correlation coefficient between Vigilance-CO and PRAM-CO was 0.83 (95% confidence interval, 0.57-0.94; P < .001). The bias was 0.22 ± 0.55 L/min with limits of agreement between 0.87 and 1.30 L/min. The percentage error was 25%. Mean TP-CO was 6.78 ± 2.04 L/min (range, 4.12-11.27 L/min), and the mean PRAM-CO was 6.11 ± 2.18 L/min (range, 2.82-10.90 L/min). The correlation coefficient between PiCCO-CO and PRAM-CO was 0.91 (95% confidence interval, 0.83-0.96; P < .0001). The bias was 0.67 ± 0.89 L/min with limits of agreement -1.07 and 2.41 L/min. The coefficient of variation for PiCCO was 4% ± 2%, and the coefficient of variation for PRAM was 10% ± 8%. The percentage error was 28%.

CONCLUSIONS

The PRAM system showed good agreement with pulmonary artery catheter and PiCCO in hemodynamically stabilized patients.

Less-invasive approaches to perioperative haemodynamic optimization

PURPOSE OF REVIEW

A number of less-invasive haemodynamic monitoring devices have been introduced in recent years, largely replacing the pulmonary artery catheter (PAC) as a standard monitoring tool. Apart from tracking cardiac output (CO), these monitors provide additional haemodynamic parameters. The aim of this article is to review the most widely used less-invasive monitoring modalities, their technical characteristics and limitations regarding their clinical performance.

RECENT FINDINGS

The utilization of CO monitoring in the perioperative setting has been shown to be associated with improved outcomes if integrated into a haemodynamic optimization strategy. These findings provide the basis of recent recommendations for perioperative monitoring.

SUMMARY

An array of monitoring modalities have been introduced that can reliably track CO in the perioperative setting and make the PAC dispensable in most clinical situations. In order to be used safely and efficiently, knowledge regarding the inherent monitoring techniques and their limitations, their clinical validity and the utility of the parameters provided is crucial.

Evaluation of stroke volume variations obtained with the pressure recording analytic method

OBJECTIVE

To investigate whether stroke volume variations obtained with the pressure recording analytic method can predict fluid responsiveness in mechanically ventilated patients with circulatory failure.

DESIGN

Prospective study.

SETTING

Surgical intensive care unit of a university hospital.

PATIENTS

Thirty-five mechanically ventilated patients with circulatory failure for whom the decision to give fluid was taken by the physician were included. Exclusion criteria were: Arrhythmia, tidal volume <8 mL/kg, left ventricular ejection fraction<50%, right ventricular dysfunction, and heart rate/respiratory rate ratio <3.6.

INTERVENTIONS

Fluid challenge with 500 mL of saline over 15 mins.

MEASUREMENTS AND MAIN RESULTS

Stroke volume variations and cardiac output obtained with a pressure recording analytic method, pulse pressure variations, and cardiac output estimated by echocardiography were recorded before and after volume expansion. Patients were defined as responders if stroke volume obtained using echocardiography increased by ≥15% after volume expansion. Nineteen patients responded to the fluid challenge. Median [interquartile range, 25% to 75%] stroke volume variation values at baseline were not different in responders and nonresponders (10% [8-16] vs. 14% [12-16]), whereas pulse pressure variations were significantly higher in responders (17% [13-19] vs. 7% [5-10]; p < .0001). A 12.6% stroke volume variations threshold discriminated between responders and nonresponders with a sensitivity of 63% (95% confidence interval 38% to 84%) and a specificity of 69% (95% confidence interval 41% to 89%). A 10% pulse pressure variation threshold discriminated between responders and nonresponders with a sensitivity of 89% (95% confidence interval 67% to 99%) and a specificity of 88% (95% confidence interval 62% to 98%). The area under the receiver operating characteristic curves was different between pulse pressure variations (0.95; 95% confidence interval 0.82-0.99) and stroke volume variations (0.60; 95% confidence interval 0.43-0.76); p < .0001). Volume expansion-induced changes in cardiac output measured using echocardiography or pressure recording analytic method were not correlated (r = 0.14; p > .05) and the concordance rate of the direction of change in cardiac output was 60%.

CONCLUSION

Stroke volume variations obtained with a pressure recording analytic method cannot predict fluid responsiveness in intensive care unit patients under mechanical ventilation. Cardiac output measured by this device is not able to track changes in cardiac output induced by volume expansion.

Non invasive continuous hemodynamic evaluation of cirrhotic patients after postural challenge

AIM

To assess whether Most Care is able to detect the cardiovascular alterations in response to physiological stress (posture).

METHODS

Non invasive hemodynamic was assessed in 26 cirrhotic patients compared to healthy subjects, both in the supine and standing positions.

RESULTS

In baseline conditions, when compared to healthy subjects, cirrhotic patients showed significantly lower values of dicrotic and diastolic pressures and systemic vascular resistance. While in the standing position, cirrhotic patients showed higher values of cardiac index, stroke volume index and cardiac cycle efficiency. When returning to the supine position, cirrhotic patients exhibited lower values of dicrotic and diastolic pressures and systemic vascular resistance in the presence of higher values of cardiac index, stroke volume index and cardiac cycle efficiency.

CONCLUSION

Most Care proved to be able to detect cardiovascular abnormalities bedside in the resting state and after postural challenge in cirrhotic patients.

Emerging technologies

Hemodynamic monitoring in critically ill patients has been considered part of the standard of care in managing patients with shock and/or acute lung injury, but outcome benefit, particularly in pediatric patients, has been questioned. There is difficulty in validating the reliability of monitoring devices, especially since this validation requires comparison to the pulmonary artery catheter, which has its own problems as a measurement tool. Interpretation of the available evidence reveals advantages and disadvantages of the available hemodynamic monitoring devices.