The Pressure Recording Analytical Method (PRAM): Technical Concepts and Literature Review

Effect of Hemodynamic Monitoring Systems on Short-Term Outcomes after Living Donor Liver Transplantation

Background and Objectives: To evaluate the effects of the pulse index continuous cardiac output and MostCare Pressure Recording Analytical Method hemodynamic monitoring systems on short-term graft and patient outcomes during living donor liver transplantation in adult patients. Materials and Methods: Overall, 163 adult patients who underwent living donor liver transplantation between January 2018 and March 2022 and met the study inclusion criteria were divided into two groups based on the hemodynamic monitoring systems used during surgery: the MostCare Pressure Recording Analytical Method group (n = 73) and the pulse index continuous cardiac output group (n = 90). The groups were compared with respect to preoperative clinicodemographic features (age, sex, body mass index, graft-to-recipient weight ratio, and Model for End-stage Liver Disease score), intraoperative clinical characteristics, and postoperative biochemical parameters (aspartate aminotransferase, alanine aminotransferase, total bilirubin, direct bilirubin, prothrombin time, international normalized ratio, and platelet count). Results: There were no significant between-group differences with respect to recipient age, sex, body mass index, graft-to-recipient weight ratio, Child, Model for End-stage Liver Disease score, ejection fraction, systolic pulmonary artery pressure, surgery time, anhepatic phase, cold ischemia time, warm ischemia time, erythrocyte suspension use, human albumin use, crystalloid use, urine output, hospital stay, and intensive care unit stay. However, there was a significant difference in fresh frozen plasma use (p < 0.001) and platelet use (p = 0.037). Conclusions: The clinical and biochemical outcomes are not significantly different between pulse index continuous cardiac output and MostCare Pressure Recording Analytical Method as hemodynamic monitoring systems in living donor liver transplantation. However, the MostCare Pressure Recording Analytical Method is more economical and minimally invasive.

Novel parameters for predicting fluid responsiveness during the mini fluid challenge and ability of the cardiac power index: an observational cohort study

Background/aim

The percentage change in the stroke volume index (SVI) due to the mini fluid challenge (MFC) (MFC-ΔSVI%) is used commonly in daily practice. However, up to 20% of patients remain in the gray zone of this variable. Thus, it was aimed to compare the MFC-ΔSVI% and the percentage change in the cardiac power index (CPI) due to the MFC (MFC-ΔCPI%) with the baseline values of the pulse pressure variation (PPV) and stroke volume variation (SVV) in terms of their abilities to predict fluid responsiveness.

Materials and methods

The SVI, CPI, SVV, and PPV were recorded before 100 mL of isotonic saline was infused (MFC), after MFC was completed, and after an additional 400 mL of isotonic saline was infused to complete 500 mL of fluid loading (FL). Patients whose SVI increased more than 15% after the FL were defined as fluid responders.

Results

Sixty-seven patients completed the study and 35 (52%) of them were responders.The areas under the receiver operating characteristics curves for the MFC-ΔSVI% and MFC-ΔCPI% (0.94; 95% CI: 0.86-0.99 and 0.89; 95% CI: 0.79-0.95, respectively) were significantly higher than those for the SVV and PPV (0.63; 95% CI: 0.50-0.75 and 0.55; 95% CI: 0.42-0.67, respectively) (p < 0.001 for all of the comparisons). The gray zone analysis revealed that the MFC-ΔSVI% values of 12 patients were in the gray zone. Of the 12, the MFC-ΔCPI% values of 7 patients were outside of the gray zone.

Conclusion

Fluid responsiveness can be predicted more accurately using the MFC-ΔSVI% and MFC-ΔCPI% than using the SVV and PPV. Additionally, concomitant use of the MFC-ΔSVI% and MFC-ΔCPI% is recommended, as this approach diminishes the number of patients in the gray zone.

Agreement between cardiac output measurements by pulse wave analysis using the Pressure Recording Analytical Method and transthoracic echocardiography in patients with veno-venous extracorporeal membrane oxygenation therapy: An observational method comparison

BACKGROUND

Measuring cardiac output (CO) is important in patients treated with veno-venous extracorporeal membrane oxygenation (vvECMO) because vvECMO flow and CO need to be balanced. Uncalibrated pulse wave analysis with the Pressure Recording Analytical Method (PRAM) may be suitable to measure CO in patients with vvECMO therapy.

OBJECTIVE

To assess the agreement between CO measured by PRAM (PRAM-CO; test method) and CO measured by transthoracic echocardiography (TTE-CO; reference method).

DESIGN

A prospective observational method comparison study.

SETTING

The ICU of a German university hospital between March and December 2021.

PATIENTS

Thirty one adult patients with respiratory failure requiring vvECMO therapy: 29 of the 31 patients (94%) were treated for COVID-19 related respiratory failure.

MAIN OUTCOME MEASURES

PRAM-CO and TTE-CO were measured simultaneously at two time points in each patient with at least 20 min between measurements. A radial or femoral arterial catheter-derived blood pressure waveform was used for PRAM-CO measurements. TTE-CO measurements were conducted using the pulsed wave Doppler-derived velocity time integral of the left ventricular outflow tract (LVOT) and the corresponding LVOT diameter. PRAM-CO and TTE-CO were compared using Bland-Altman analysis and the percentage error (PE). We defined a PE of <30% as clinically acceptable.

RESULTS

Mean ± SD PRAM-CO was 6.86 ± 1.49 l min -1 and mean TTE-CO was 6.94 ± 1.58 l min -1 . The mean of the differences between PRAM-CO and TTE-CO was 0.09 ± 0.73 l min -1 with a lower 95% limit of agreement of -1.34 l min -1 and an upper 95% limit of agreement of 1.51 l min -1 . The PE was 21%.

CONCLUSIONS

The agreement between PRAM-CO and TTE-CO is clinically acceptable in adult patients with vvECMO therapy.

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.

Effects of dexmedetomidine on cardiac electrophysiology in patients undergoing general anesthesia during perioperative period: a randomized controlled trial

Background

Dexmedetomidine has controversial influence on cardiac electrophysiology. The aim of this study was to explore the effects of dexmedetomidine on perioperative cardiac electrophysiology in patients undergoing general anesthesia.

Methods

Eighty-one patients were randomly divided into four groups: groups D₁, D₂, D₃ receiving dexmedetomidine 1, 1, 0.5 μg/kg over 10 min and 1, 0.5, 0.5 μg/kg/h continuous infusion respectively, and control group (group C) receiving normal saline. Twelve-lead electrocardiograms were recorded at the time before dexmedetomidine/normal saline infusion (T₁), loading dose finish (T₂), surgery ending (T₆), 1 h (T₇) after entering PACU, 24 h (T₈), 48 h (T₉), 72 h (T₁₀) and 1 month (T₁₁) postoperatively. Cardiac circulation efficiency (CCE) were also recorded.

Results

Compared with group C, QTc were significantly increased at T₂ in groups D₁ and D₂ while decreased at T₇ and T₈ in group D₃ (P < 0.05), iCEB were decreased at T₈ (P < 0.05). Compared with group D₁, QTc at T₂, T₆, T₇, T₉ and T₁₀ and iCEB at T₈ were decreased, and CCE at T₂-T₄ were increased in group D₃ significantly (P < 0.05). Compared with group D₂, QTc at T₂ and iCEB at T₈ were decreased and CCE at T₂ and T₃ were increased in group D₃ significantly (P < 0.05).

Conclusions

Dexmedetomidine at a loading dose of 0.5 μg/kg and a maintenance dose of 0.5 μg/kg/h can maintain stability of cardiac electrophysiology during perioperative period and has no significant adverse effects on CCE.

Trial registration

ClinicalTrials.gov NCT04577430 (Date of registration: 06/10/2020).

Hemodynamic Assessment of a Large Pulmonary Arteriovenous Malformation in a Neonate: Case Report and Review of Literature

Herein we report the case of a neonate with a prenatally diagnosed large pulmonary arteriovenous malformation, managed with minimally invasive hemodynamic monitoring in our Neonatal Intensive Care Unit. The combination of Near-Infrared Spectroscopy and Pressure Recording Analytical Method could guide neonatal management of critical cases of vascular anomalies: immediate data are offered to clinicians, from which therapeutic decisions such as timing of surgical resection are made to achieve a positive outcome. We also systemically collected and summarized information on patients' characteristics of previous cases reported in literature to data, and we compared them to our case.

Pulse Wave Analysis Using the Pressure Recording Analytical Method to Measure Cardiac Output in Pediatric Cardiac Surgery Patients: A Method Comparison Study Using Transesophageal Doppler Echocardiography as Reference Method

BACKGROUND

Cardiac output (CO) is a key determinant of oxygen delivery, but choosing the optimal method to obtain CO in pediatric patients remains challenging. The pressure recording analytical method (PRAM), implemented in the MostCareUp system (Vygon), is an invasive uncalibrated pulse wave analysis (PWA) method to measure CO. The objective of this study is to compare CO measured by PRAM (PRAM-CO; test method) with CO simultaneously measured by transesophageal Doppler echocardiography (TEE-CO; reference method) in pediatric patients.

METHODS

In this prospective observational method comparison study, PRAM-CO and TEE-CO were assessed in pediatric elective cardiac surgery patients at 2 time points: after anesthesia induction and after surgery. The study was performed in a German university medical center from March 2019 to March 2020. We included pediatric patients scheduled for elective cardiac surgery with arterial catheter and TEE monitoring. PRAM-CO and TEE-CO were compared using Bland-Altman analysis accounting for repeated measurements per subject, and the percentage error (PE).

RESULTS

We included 52 PRAM-CO and TEE-CO measurement pairs of 30 patients in the final analysis. Mean ± SD TEE-CO was 2.15 ± 1.31 L/min (range 0.55-6.07 L/min), and mean PRAM-CO was 2.21 ± 1.38 L/min (range 0.55-5.90 L/min). The mean of the differences between TEE-CO and PRAM-CO was -0.06 ±0.38 L/min with 95% limits of agreement (LOA) of 0.69 (95% confidence interval [CI], 0.53-0.82 L/min) to -0.80 L/min (95% CI, -1.00 to -0.57 L/min). The resulting PE was 34% (95% CI, 27%-41%).

CONCLUSIONS

With a PE of <45%, PRAM-CO shows clinically acceptable agreement with TEE-CO in hemodynamically stable pediatric patients before and after cardiac surgery.

Estimation of cardiac stroke volume from radial pulse waveform by artificial neural network

BACKGROUND AND OBJECTIVES

Stroke volume (SV) and cardiac output (CO) are the key indicators for the evaluation of cardiac function and hemodynamic status during the perioperative period, which are very important in the detection and treatment of cardiovascular diseases. Traditional CO and SV measurement methods have problems such as complex operation, low precision and poor generalization ability.

METHODS

In this paper, a method for estimating stroke volume based on cascade artificial neural network (ANN) and time domain features of radial pulse waveform (SV_ANN) was proposed. The simulation datasets of 4000 radial pulse waveforms and stroke volume (SV_meas) were generated by a 55 segment transmission line model of the human systemic vasculature and a recursive algorithm. The ANN was trained and tested by 10-fold cross-validation, and compared with 12 traditional models.

RESULTS

Experimental results showed that the Pearson correlation coefficients and mean difference between SV_ANN and SV_meas (R=0.95, mean standard deviation (SD) = 0.00 ± 6.45) were better than the best results of the 12 traditional models. Moreover, as increasing the number of training samples, the performance improvement of the ANN (R=0.94(Δ + 0.04), mean ± SD = 0.00 ± 6.38(Δ± 2.02)) was better than the other best model, namely, multiple linear regression model (MLR) (R=0.93(Δ + 0.03), mean ± SD = 0.00 ± 6.99(Δ± 1.50)).

CONCLUSIONS

A method is proposed to estimate cardiac stroke volume by the ANN with time domain features of radial pulse wave. It avoids the complicated modeling process based on hemodynamics within traditional models, improves the estimation accuracy of SV, and has a good generalization ability.

A novel method for the noninvasive estimation of cardiac output with brachial oscillometric blood pressure measurements through an assessment of arterial compliance

OBJECTIVE

To propose and validate a new method for estimating cardiac output based on the total arterial compliance (Ct) formula that does not need an arterial waveform and to apply it to brachial oscillometric blood pressure measurements (OBPMs).

METHODS

One hundred subjects with normal heart anatomy and function were included. Reference values for cardiac output were measured with echocardiography, and Ct was calculated with a two-element Windkessel model. Then, a statistical model of arterial compliance (Ce) was used to estimate cardiac output. Finally, the measured and estimated cardiac output values were compared for accuracy and reproducibility.

RESULTS

The model was derived from the data of 70 subjects and prospectively tested with the data from the remaining 30 individuals. The mean age of the whole group was 43.4 ± 12.8 years, with 46% women. The average blood pressure (BP) was 107.1/65.0 ± 15.0/9.6 mmHg and the average heart rate was 67.7 ± 11.4 beats/min. The average Ct was 1.39 ± 0.27 mL/mmHg and the average cardiac output was 5.5 ± 1.0 L/min. The mean difference in the cardiac output estimated by the proposed methodology vs. that measured by Doppler echocardiography was 0.022 L/min with an SD of 0.626 L/min. The intraclass correlation coefficient was 0.93, and the percentage error was 19%.

CONCLUSION

Cardiac output could be reliably and noninvasively obtained with brachial OBPMs through a novel method for estimating Ct without the need for an arterial waveform. The new method could identify hemodynamic factors that explain BP values in an ambulatory care setting.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Supplementary Information

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

Hemodynamic outcome of different ventilation modes in laparoscopic surgery with exaggerated trendelenburg: a randomised controlled trial

Purpose

To compare hemodynamic effects of two different modes of ventilation (volume-controlled and pressure-controlled volume guaranteed) in patients undergoing laparoscopic gynecology surgeries with exaggerated Trendelenburg position.

Methods

Thirty patients undergoing laparoscopic gynecology operations were ventilated using either volume-controlled (Group VC) or pressure-controlled volume guaranteed mode (Group PCVG) (n = 15 for both groups). Hemodynamic variables were measured using Pressure Recording Analytical Method by radial artery cannulation in addition to peak and mean airway pressures and expired tidal volume.

Results

The only remarkable finding was a more stable cardiac index in Group PCVG, where other hemodynamic parameters were similar. Expired tidal volume increased in Group VC while peak airway pressure was lower in Group PCVG.

Conclusion

PCV-VG causes less hemodynamic perturbations as measured by Pressure Recording Analytical Method (PRAM) and allows better intraoperative hemodynamic control in exaggerated Trendelenburg position in laparoscopic surgery.

Veno-arterial CO2 difference and cardiac index in children after cardiac surgery

Veno-arterial CO2 difference has been considered as a marker of low cardiac output. This study aimed to evaluate the correlation between veno-arterial CO2 difference and cardiac index estimated by MostCareTM in children after cardiac surgery and its association with other indirect perfusion parameters and the complex clinical course (vasoactive inotropic score above 15 or length of stay above 5 days).Data from 40 patients and 127 arterial and venous CO2 measurements for gap calculation taken 0-5 days postoperatively were available. The median (range) veno-arterial CO2 difference value was 9 (1-25 mmHg). The correlation between veno-arterial CO2 difference and cardiac index was not significant (r: -0.16, p = 0.08). However, there was a significant correlation between veno-arterial CO2 difference and vasoactive inotropic score (r: 0.21, p = 0.02), systolic arterial pressure (r: -0.43, p = 0.0001), dP/dtMAX (r: 0.26, p = 0.004), and arterio-venous O2 difference (r: 0.63, p = 0.0001). Systolic arterial pressure (OR 0.95, 95% CI 0.90-0.99), dP/dtMAX (OR 0.00, 95% CI 0.00-0.06), lactates (OR 1.87, 95% CI 1.21-3.31), and veno-arterial CO2 difference (OR 1.13, 95% CI 1.01-1.35) showed a significant univariate association with the complex clinical course. In conclusion, veno-arterial CO2 difference did not correlate with cardiac index estimated by MostCareTM in our cohort of post-cardiosurgical children, but it identified patients with the complex clinical course, especially when combined with other direct and indirect variables of perfusion.

Cardiac Output Measurement With Echocardiography and Pressure Recording Analytical Method in Pediatric Patients Admitted to the Cardiac Intensive Care Unit: A Retrospective Assessment of Bias Between the Two Methods

OBJECTIVES

This study aimed to compare, in a cohort of critically ill children with biventricular anatomy and no cardiovascular shunt, cardiac output (CO) and cardiac index (CI) assessed by echocardiography and a continuous pulse-contour method, MostCare^UP, to measure the differences between these techniques (biasCO and biasCI), and their association with clinical variables.

DESIGN

Retrospective study.

SETTING

Tertiary pediatric cardiac intensive care unit.

PARTICIPANTS

Children admitted to the pediatric cardiac intensive care unit who underwent echocardiography with CO measurement.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thirty-five patients were included. BiasCO was -0.02 (0.26) L/min (percentage error 36%). BiasCI was 0.07 (0.34) L/min/m² (percentage error 18%). Biases and percentage errors were higher in 24 nonsupervised echocardiographies. A negative biasCO (overestimation by MostCare^UP) was associated with post-surgical status (v cardiomyopathy), higher systolic arterial pressure, and spontaneous breathing (v intubation). When only absolute values were considered, biasCO_NONEG correlated with age, weight, arterial pressure, and heart rate, whereas biasCI_NONEG was associated with a femoral arterial cannula, no use of inotropes, and the absence of mechanical ventilation. After adjustment, biasCO_NONEG remained independently associated with patients' body weight(p = 0.0001). BiasCI_NONEG showed a nonlinear relationship with weight below 20 kg and above 40 kg.

CONCLUSIONS

Children with extreme low or high weights, those who are extubated, and those with a femoral cannula carry the highest bias. When younger patients are considered, CI should be evaluated instead of CO, because biases are better highlighted by indexing data on body surface area. In children, both echocardiography and MostCare^UP may be responsible of inaccurate CO/CI assessment.

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.

Prognostic value of cardiac cycle efficiency in children undergoing cardiac surgery: a prospective observational study

BACKGROUND

Cardiac cycle efficiency (CCE) derived from a pressure-recording analytical method is a unique parameter to assess haemodynamic performance from an energetic view. This study investigated changes of CCE according to an anatomical diagnosis group, and its association with early postoperative outcomes in children undergoing cardiac surgery.

METHODS

Ninety children were included with a ventricular septal defect (VSD; n=30), tetralogy of Fallot (TOF; n=40), or total anomalous pulmonary venous connection (TAPVC; n=20). CCE along with other haemodynamic parameters, was recorded from anaesthesia induction until 48 h post-surgery. Predictive CCE (CCE_p) was defined as the average of CCE at post-modified ultrafiltration and CCE at the end of surgery. The relationship between CCE and early outcomes was assessed by the comparison between the high-CCE_p group (CCE_p ≥75th centile) and the low-CCE_p group (CCE_p ≤25th centile).

RESULTS

There was a significant time × diagnostic group interaction effect in the trend of CCE. Compared with the high-CCE_p group (n=23), the low-CCE_p group (n=22) required more inotropics post-surgery, had higher lactate concentrations at 8 and 24 h post-surgery, a longer intubation time and longer ICU stay, and higher frequency of peritoneal fluid.

CONCLUSIONS

Perioperative changes of CCE vary according to anatomical diagnosis in children undergoing cardiac surgery. Children with TOF have an unfavourable trend of CCE compared with children with VSD or TAPVC. A decline in CCE is associated with adverse early postoperative outcomes.

CLINICAL TRIAL REGISTRATION

ChiCTR1800014996.

Accuracy of a multiparametric score based on pulse wave analysis for prediction of fluid responsiveness: ancillary analysis of an observational study

Purpose

The pressure recording analytical method (PRAM) monitor is a non-invasive pulse contour cardiac output (CO) device that cannot be considered interchangeable with the gold standard for CO estimation. It, however, generates additional hemodynamic indices that need to be evaluated. Our objective was to investigate the performance of a multiparametric predictive score based on a combination of several parameters generated by the PRAM monitor to predict fluid responsiveness.

Methods

Secondary analysis of a prospective observational study from April 2016 to December 2017 in two French teaching hospitals. We included critically ill patients who were monitored by esophageal Doppler monitoring and an invasive arterial line, and received a 250–500 mL crystalloid fluid challenge. The main outcome measure was the predictive score discrimination evaluated by the area under the receiver operating characteristics curve.

Results

The three baseline PRAM-derived parameters associated with fluid responsiveness in univariate analysis were pulse pressure variation, cardiac cycle efficiency, and arterial elastance (P < 0.01, P = 0.03, and P < 0.01, respectively). The median [interquartile range] predictive score, calculated after discretization of these parameters according to their optimal threshold value was 3 [2–3] in fluid responders and 1 [1–2] in fluid non-responders, respectively (P < 0.001). The area under the curve of the predictive score was 0.807 (95% confidence interval, 0.662 to 0.909; P < 0.001).

Conclusion

A multiparametric score combining three parameters generated by the PRAM monitor can predict fluid responsiveness with good positive and negative predictive values in intensive care unit patients.

Electronic supplementary material

The online version of this article (10.1007/s12630-020-01736-y) contains supplementary material, which is available to authorized users.

Measuring cardiac output at the bedside

PURPOSE OF REVIEW

Bedside cardiac output (CO) measurement is an important part of routine hemodynamic monitoring in the differential diagnosis of circulatory shock and fluid management. Different choices of CO measurement devices are available. The purpose of this review is to review the importance of CO [or stroke volume (SV)] measurement and to discuss the various methods (devices) used in determination of CO.

RECENT FINDINGS

CO measurement devices can be classified into two types: those use simple physical principles with minimal assumptions, and those predicting CO via mathematical modelling with a number of assumptions. Both have pros and cons, with the former being more accurate but with limited continuous monitoring capability whereas the latter less accurate but usually equipped with continuous monitoring functionality. With frequent updates in mathematical models, research data constantly become outdated in this area. Recent data suggest devices based on mathematical modelling have limited accuracies and poor precisions.

SUMMARY

Measurement of CO or SV is important in critically ill patients. Most devices have accuracy and reliability issues. The choice of device should depend on the purpose of measurement. For diagnostic purposes, devices based on simple physical principles, especially thermodilution and transthoracic echocardiography are more reliable due to accuracy.

Comparison of estimation of cardiac output using an uncalibrated pulse contour method and echocardiography during veno-venous extracorporeal membrane oxygenation

Introduction:

During veno-venous extracorporeal membrane oxygenation, cardiac output monitoring is essential to assess tissue oxygen delivery. Adequate arterial oxygenation depends on the ratio between the extracorporeal pump blood flow and the cardiac output. The aim of this study was to compare estimates of cardiac output and blood flow/cardiac output ratios made using an uncalibrated pulse contour method with those made using echocardiography in patients treated with veno-venous extracorporeal membrane oxygenation.

Methods:

Cardiac output was estimated simultaneously using a pulse contour method (MostCareUp; Vygon, Encouen, France) and echocardiography in 17 hemodynamically stable patients treated with veno-venous extracorporeal membrane oxygenation. Comparisons were made using Bland–Altman and linear regression analysis.

Results:

There were significant correlations between cardiac output estimated using pulse contour method and echocardiography and between blood flow/cardiac output estimated using pulse contour method and blood flow/cardiac output estimated using echocardiography (r = 0.84, p < 0.001 and r = 0.87, p < 0.001, respectively). Bland–Altman analysis showed a good agreement (bias −0.20 ± 0.50 L/min) and a low percentage of error (25%) for the cardiac output values estimated by the two methods. The bias between the blood flow/cardiac output ratios obtained with the two methods was 5.19% ± 12.3% (percentage of error = 28.1%).

Conclusions:

The pulse contour method is a valuable alternative to echocardiography for the assessment of cardiac output and the blood flow/cardiac output ratio in patients treated with veno-venous extracorporeal membrane oxygenation.

Estimation of central arterial pressure from the radial artery in patients undergoing invasive neuroradiological procedures

Backgrounds

Central arterial pressure can be derived from analysis of the peripheral artery waveform. The aim of this study was to compare central arterial pressures measured from an intra-aortic catheter with peripheral radial arterial pressures and with central arterial pressures estimated from the peripheral pressure wave using a pressure recording analytical method (PRAM).

Methods

We studied 21 patients undergoing digital subtraction cerebral angiography under local or general anesthesia and equipped with a radial arterial catheter. A second catheter was placed in the ascending aorta for central pressure wave acquisition. Central (AO) and peripheral (RA) arterial waveforms were recorded simultaneously by PRAM for 90–180 s. During an off-line analysis, AO pressures were reconstructed (AO_rec) from the RA trace using a mathematical model obtained by multi-linear regression analysis. The AO_rec values obtained by PRAM were compared with the true central pressure value obtained from the catheter placed in the ascending aorta.

Results

Systolic, diastolic and mean pressures ranged from 79 to 180 mmHg, 47 to 102 mmHg, and 58 to 128 mmHg, respectively, for AO, and 83 to 174 mmHg, 47 to 107 mmHg, and 60 to 129 mmHg, respectively, for RA. The correlation coefficients between AO and RA were 0.86 (p < 0.01), 0.83 (p < 0.01) and 0.86 (p < 0.01) for systolic, diastolic and mean pressures, respectively, and the mean differences − 0.3 mmHg, 2.4 mmHg and 1.5 mmHg. The correlation coefficients between AO and AO_rec were 0.92 (p < 0.001), 0.87 (p < 0.001) and 0.92 (p < 0.001), for systolic, diastolic and mean pressures, respectively, and the mean differences 0.01 mmHg, 1.8 mmHg and 1.2 mmHg.

Conclusions

PRAM can provide reliable estimates of central arterial pressure.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0844-1) contains supplementary material, which is available to authorized users.

Monitoring haemodynamic response to fluid-challenge in ICU: comparison of pressure recording analytical method and oesophageal Doppler: A prospective observational study

BACKGROUND

The ability of the pressure recording analytical method (PRAM) in tracking change in cardiac output (ΔCO) after a fluid challenge in ICU needs to be evaluated with the most contemporary comparison methods recommended by experts.

OBJECTIVE

Our objective was to report the trending ability of PRAM in tracking ΔCO after a fluid challenge in ICU and to compare this with oesophageal Doppler monitoring (ODM).

DESIGN

Prospective, observational study.

SETTING

Hôpital Lariboisière and Hôpital Européen George Pompidou, Paris, France, from April 2016 to December 2017.

PATIENTS

Critically ill patients admitted to ICU with monitoring of CO monitored by ODM and invasive arterial pressure.

INTERVENTION

ΔCO after fluid challenge was simultaneously registered with ODM and PRAM connected to the arterial line.

MAIN OUTCOME MEASURE

Polar statistics (mean angular bias, radial limits of agreement and polar concordance rate) and clinical concordance evaluation (error grid and clinical concordance rate). Predictors of bias were determined.

RESULTS

Sixty-eight fluid challenge were administered in 49 patients. At the time of fluid challenge, almost all were mechanically ventilated (99%), with 85% receiving norepinephrine. Admission diagnosis was septic shock in 70% of patients. Patients had a Sequential Organ Failure Assessment score of 10 [7 to 12] and a median Simplified Acute Physiology Score II of 61 [49 to 69]. Relative ΔCO bias was 7.8° (6.3°) with radial limits of agreement of ±41.7°, polar concordance rate 80% and clinical concordance rate 74%. ΔCO bias was associated with baseline bias (P = 0.007). Baseline bias was associated with radial location of the arterial line (P = 0.03).

CONCLUSION

When compared with ODM, PRAM has insufficient performance to track ΔCO induced by fluid challenge in ICU patients. Baseline bias is an independent predictor of trending bias.

TRIAL REGISTRATION

IRB 00010254-2016-033.

Relationship between Microcirculatory Perfusion and Arterial Elastance: A Pilot Study

Background

Arterial elastance (Ea) represents the total afterload imposed on the left ventricle, and it is largely influenced by systemic vascular resistance (SVR). Although one can expect that Ea is influenced by peripheral endothelial function, no data are available to support it in patients. The aim of this study was to investigate the relationship between Ea, SVR, and microvascular perfusion in critically ill patients undergoing the fluid challenge (FC).

Methods

A prospective study in patients receiving a fluid challenge. A pulse wave analysis system (MostCare, Vygon, France) was used to estimate Ea and an incident dark field (IDF) handheld device (Braedius Medical BV, The Netherlands) to evaluate the sublingual microcirculation. Microvascular perfusion was assessed using the proportion of small-perfused vessels (PPV). Relative changes in each variable were calculated before and after FC; fluid responsiveness was defined as an increase in the cardiac index by at least 10% from baseline.

Results

We studied 20 patients requiring a fluid challenge (n=10 for hypotension; n=5 for oliguria; n=3 for lactate values greater than 2 mmol/l; n=2 for tachycardia), including 12 fluid responders. There was a strong correlation between Ea and SVR (r² = 0.75; p < 0.001) and only a weak correlation between Ea and PPV at baseline (r² = 0.22; p=0.04). Ea decreased from 1.4 [1.2–1.6] to 1.2 [1.1–1.4] mmHg/mL (p=0.01), SVR from 1207 [1006–1373] to 1073 [997–1202] dyn ∗ s/cm⁵ (p=0.06), and PPV from 56 [51–64] % to 59 [47–73] % (p=0.25) after fluid challenge. Changes in Ea were significantly correlated with changes in SVR, but not with changes in PPV.

Conclusions

The correlation between Ea and indexes of microvascular perfusion in the sublingual region is weak. The impact of microcirculatory perfusion on the arterial load is probably limited.

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.

Hyperthermic intrathoracic chemotherapy after extended pleurectomy and decortication for malignant pleura mesothelioma: an observational study on outcome and microcirculatory changes

Background

In the treatment of malignant pleural mesothelioma the Hyperthermic Intra THOracic Chemotherapy (HITHOC) can improve the efficacy of pleurectomy and decortication with a local cytotoxic effect. However its biological impact in patient's hemodynamic and microcirculatory changes were rarely investigated. Aim of this study is to describe our experience with HITHOC after pleurectomy and decortication evaluating the role of sublingual video-microscopy in assessing the microcirculatory changes in the perioperative period.

Methods

This is a prospective and observational study concerning 10 consecutive patients undergoing extended P/D followed by HITHOC. These patients underwent sublingual microcirculatory monitoring, which was adopted as a routine procedure since 2012. Haemodynamic parameters were collected at eight consecutive times: the day before surgery (T1), induction of anaesthesia (T2), surgical phase before HITHOC beginning (T3), 5 and 30 minutes after HITHOC start (T4 and T5, respectively), 5 minutes from HITHOC end (T6), after the admission in ICU (T7), at discharge from the ICU (T8). Cardiac output (CO) was calculated with MostCare. Systemic vascular resistance (SVR), oxygen delivery (DO₂), and oxygen extraction rate (O₂ER) were calculated using standard formulas. Arterial blood pressure and central venous pressure (CVP) were obtained with standard arterial and venous catheters. At the same times we assessed the sublingual microcirculation with Sidestream Dark Field technique.

Results

Hemodynamic and microcirculatory data were collected in 10 patients, 8 male and 2 females (mean age 68.6±9.0, and body surface area of 1.9±0.1 m²). All patients had arterial hypertension, and one patient had diabetes. The mean arterial pressure significantly decreased at T2, with respect to T1 (P=0.05). CO, CVP, DO₂, O₂ER, and ScvO₂, did not change significantly over the time. All patients needed infusion of noradrenalin from T4 to T6. TVD significantly decreased from T1 to T3, T5, and T8. Similarly, PVD significantly decreased from T1 to T3 and T8, and MFI from T1 to T6 and T8. PPV and HI did not change over the study period. No correlation was found between hemodynamic parameters (MAP, CO, CVP, DO₂, O₂ER, ScvO₂) and microcirculatory data (TVD, PVD, PPV, MFI, HI), at any time of the study.

Conclusions

In patients who receive HITHOC the fluid load can reduce the microvascular impairment restoring the normal tissue perfusion. This process takes days but is most evident in the first 72 h. The use of colloid and blood transfusion is much more effective in restoring microcirculation and reducing tissue damaging.