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

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

Velocity-pressure loops can estimate intrinsic and pharmacologically induced changes in cardiac afterload during non-cardiac surgery. An observational study.

PURPOSE: Continuous measurement of aortic pressure and aortic flow velocity signals in the operating theatre allows us to draw velocity-pressure (Vel-Pre) loops. The global afterload angle (GALA), derived from the Vel-Pre loops, has been linked to cardiac afterload indicators. As age is the major determinant of constitutive arterial stiffness, we aimed to describe (1) the evolution of the GALA according to age in a large cohort of anesthetized patients and (2) GALA variations induced by haemodynamic interventions. METHODS: We included patients for whom continuous monitoring of arterial pressure and cardiac output were indicated. Fluid challenges or vasopressors were administered to treat intra-operative hypotension. The primary endpoint was the comparison of the GALA values between young and old patients. The secondary endpoint was the difference in the GALA values before and after haemodynamic interventions. RESULTS: We included 133 anaesthetized patients: 66 old and 67 young patients. At baseline, the GALA was higher in the old patients than in young patients (38 ± 6 vs. 25 ± 4 degrees; p < 0.001). The GALA was positively associated with age (p < 0.001), but the mean arterial pressure (MAP) and cardiac output were not. The GALA did not change after volume expansion, regardless of the fluid response, but it did increase after vasopressor administration. Furthermore, while a vasopressor bolus led to a similar increase in MAP, phenylephrine induced a more substantial increase in the GALA than noradrenaline (+ 12 ± 5° vs. + 8 ± 5°; p = 0.01). CONCLUSION: In non-cardiac surgery, the GALA seems to be associated with both intrinsic rigidity (reflected by age) and pharmacologically induced vasoconstriction changes (by vasopressors). In addition, the GALA can discriminate the differential effects of phenylephrine and noradrenaline. These results should be confirmed in a prospective, ideally randomized, trial.

Evaluation of cardiac output variations with the peripheral pulse pressure to mean arterial pressure ratio.

Cardiac output (CO) optimisation during surgery reduces post-operative morbidity. Various methods based on pulse pressure analysis have been developed to overcome difficulties to measure accurate CO variations in standard anaesthetic settings. Several of these methods include, among other parameters, the ratio of pulse pressure to mean arterial pressure (PP/MAP). The aim of this study was to evaluate whether the ratio of radial pulse pressure to mean arterial pressure (ΔPPrad/MAP) could track CO variations (ΔCO) induced by various therapeutic interventions such as fluid infusions and vasopressors boluses [phenylephrine (PE), norepinephrine (NA) or ephedrine (EP)] in the operating room. Trans-oesophageal Doppler signal and pressure waveforms were recorded in patients undergoing neurosurgery. CO and PPrad/MAP were recorded before and after fluid challenges, PE, NA and EP bolus infusions as medically required during their anaesthesia. One hundred and three patients (mean age: 52 ± 12 years old, 38 men) have been included with a total of 636 sets of measurement. During fluids challenges (n = 188), a positive correlation was found between ΔPPrad/MAP and ΔCO (r = 0.22, p = 0.003). After PE (n = 256) and NA (n = 121) boluses, ΔPPrad/MAP positively tracked ΔCO (r = 0.53 and 0.41 respectively, p < 0.001). By contrast, there was no relation between ΔPPrad/MAP and ΔCO after EP boluses (r = 0.10, p = 0.39). ΔPPrad/MAP tracked ΔCO variations during PE and NA vasopressor challenges. However, after positive fluid challenge or EP boluses, ΔPPrad/MAP was not as performant to track ΔCO which could make the use of this ratio difficult in current clinical practice.

Beat-by-beat assessment of cardiac afterload using descending aortic velocity-pressure loop during general anesthesia: a pilot study.

INTRODUCTION: Continuous cardiac afterload evaluation could represent a useful tool during general anesthesia (GA) to titrate vasopressor effect. Using beat to beat descending aortic pressure(P)/flow velocity(U) loop obtained from esophageal Doppler and femoral pressure signals might allow to track afterload changes. Methods We defined three angles characterizing the PU loop (alpha, beta and Global After-Load Angle (GALA)). Augmentation index (AIx) and total arterial compliance (Ctot) were measured via radial tonometry. Peripheral Vascular Resistances (PVR) were also calculated. Twenty patients were recruited and classified into low and high cardiovascular (CV) risk group. Vasopressors were administered, when baseline mean arterial pressure (MAP) fell by 20%. Results We studied 118 pairs of pre/post bolus measurements. At baseline, patients in the lower CV risk group had higher cardiac output (6.1 ± 1.7 vs 4.2 ± 0.6 L min; p = 0.005), higher Ctot (2.7 ± 1.0 vs 2.0 ± 0.4 ml/mmHg, p = 0.033), lower AIx and PVR (13 ± 10 vs 32 ± 11% and 1011 ± 318 vs 1390 ± 327 dyn s/cm5; p < 0.001 and p = 0.016, respectively) and lower GALA (41 ± 15 vs 68 ± 6°; p < 0.001). GALA was the only PU Loop parameter associated with Ctot, AIx and PVR. After vasopressors, MAP increase was associated with a decrease in Ctot, an increase in AIx and PVR and an increase in alpha, beta and GALA (p < 0.001 for all). Changes in GALA and Ctot after vasopressors were strongly associated (p = 0.004). Conclusions PU Loop assessment from routine invasive hemodynamic optimization management during GA and especially GALA parameter could monitor cardiac afterload continuously in anesthetized patients, and may help clinicians to titrate vasopressor therapy.

Velocity-pressure loops for continuous assessment of ventricular afterload: influence of pressure measurement site.

VPloop, the graphical representation of pressure versus velocity, and its characteristic angles, GALA and ß, can be used to monitor cardiac afterload during anesthesia. Ideally VPloop should be measured from pressure and velocity obtained at the same arterial location but standard of care usually provide either radial or femoral pressure waveforms. The purpose of this study was to look at the influence of arterial sites and the use of a transfer function (TF) on VPloop and its related angles. Invasive pressure signals were recorded in 25 patients undergoing neuroradiology intervention under general anesthesia with transesophageal flow velocity monitoring. Pressures were recorded in the descending thoracic aorta, abdominal aorta, femoral and radial arteries. We compared GALA and ß from VPloops generated from each location and in high and low risk patients. GALA was similar in the central locations (55°[49-63], 52°[47-61] and 54°[45-62] from descending thoracic to femoral artery, median[interquartile], p = 0.10), while there was a difference in ß angle (16°[4-27] to 8°[3-15], p < 0.0001). GALA and ß obtained from radial waveforms were different (39°[31-47] compared to 46°[36-54] and 6°[2-14] compared to 16°[4-27] for GALA and ß angles respectively, p < 0.001) which was corrected by the use of a TF (45°[32-55] and 17°[5-28], p = ns). GALA and ß are underestimated when measured with a radial catheter. Using pressure waveforms from femoral locations alters VPloops, GALA and ß in a smaller extend. The use of a TF on radial pressure allows to correctly plot VPloops and their characteristic angles for routine clinical use.

A biomechanics-based parametrized cardiac end-diastolic pressure-volume relationship for accurate patient-specific calibration and estimation.

A simple power law has been proposed in the pioneering work of Klotz et al. (Am J Physiol Heart Circ Physiol 291(1):H403-H412, 2006) to approximate the end-diastolic pressure-volume relationship of the left cardiac ventricle, with limited inter-individual variability provided the volume is adequately normalized. Nevertheless, we use here a biomechanical model to investigate the sources of the remaining data dispersion observed in the normalized space, and we show that variations of the parameters of the biomechanical model realistically account for a substantial part of this dispersion. We therefore propose an alternative law based on the biomechanical model that embeds some intrinsic physical parameters, which directly enables personalization capabilities, and paves the way for related estimation approaches.

Monitoring of cardiovascular physiology augmented by a patient-specific biomechanical model during general anesthesia. A proof of concept study.

During general anesthesia (GA), direct analysis of arterial pressure or aortic flow waveforms may be inconclusive in complex situations. Patient-specific biomechanical models, based on data obtained during GA and capable to perform fast simulations of cardiac cycles, have the potential to augment hemodynamic monitoring. Such models allow to simulate Pressure-Volume (PV) loops and estimate functional indicators of cardiovascular (CV) system, e.g. ventricular-arterial coupling (Vva), cardiac efficiency (CE) or myocardial contractility, evolving throughout GA. In this prospective observational study, we created patient-specific biomechanical models of heart and vasculature of a reduced geometric complexity for n = 45 patients undergoing GA, while using transthoracic echocardiography and aortic pressure and flow signals acquired in the beginning of GA (baseline condition). If intraoperative hypotension (IOH) appeared, diluted norepinephrine (NOR) was administered and the model readjusted according to the measured aortic pressure and flow signals. Such patients were a posteriori assigned into a so-called hypotensive group. The accuracy of simulated mean aortic pressure (MAP) and stroke volume (SV) at baseline were in accordance with the guidelines for the validation of new devices or reference measurement methods in all patients. After NOR administration in the hypotensive group, the percentage of concordance with 10% exclusion zone between measurement and simulation was >95% for both MAP and SV. The modeling results showed a decreased Vva (0.64±0.37 vs 0.88±0.43; p = 0.039) and an increased CE (0.8±0.1 vs 0.73±0.11; p = 0.042) in hypotensive vs normotensive patients. Furthermore, Vva increased by 92±101%, CE decreased by 13±11% (p < 0.001 for both) and contractility increased by 14±11% (p = 0.002) in the hypotensive group post-NOR administration. In this work we demonstrated the application of fast-running patient-specific biophysical models to estimate PV loops and functional indicators of CV system using clinical data available during GA. The work paves the way for model-augmented hemodynamic monitoring at operating theatres or intensive care units to enhance the information on patient-specific physiology.

ExtraCorporeal life support for Cardiac ARrest in patients with post cardiac arrest syndrome: The ECCAR study.

BACKGROUND: Post cardiac arrest shock (PCAS) occurring after resuscitated cardiac arrest (CA) is a main cause of early death. Extracorporeal life support (ECLS) could be useful pending recovery from myocardial failure. AIM: To describe our PCAS population, and the factors associated with initiation of ECLS. METHODS: This analysis included 921 patients admitted to two intensive care units between 2005 and 2014 for CA and PCAS; 43 of these patients had ECLS initiated. Neurological and ECLS-related outcomes were gathered retrospectively. RESULTS: The 43 patients treated with ECLS were predominantly (70%) young males with evidence of myocardial infarction on coronary angiography. ECLS was initiated in patients with severe cardiovascular dysfunction (median left ventricular ejection fraction 15% [interquartile range 10-25%]), a median of 9hours [interquartile range 6-16hours] after the CA. At 1 year, eight patients (19%) had survived without neurological disability. Blood lactate and coronary aetiology were associated with neurological outcomes. Logistic regression conducted using 878 controls with PCAS identified age>62 years, location of CA, use of a high dose of adrenaline (>3mg) and blood lactate and serum creatinine concentrations (>5mmol/L and>109µmol/L, respectively) as risk factors for initiation of ECLS. CONCLUSIONS: ECLS, as a salvage therapy for PCAS, could be an acceptable alternative for highly-selected patients.

Veno-arterial-ECMO in the intensive care unit: From technical aspects to clinical practice.

The use of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) as a salvage therapy in cardiogenic shock is becoming of current practice. While VA-ECMO is potentially a life-saving technique, results are sometimes mitigated, emphasising the need for selecting the right indication in the right patient. This relies upon a clear definition of the individual therapeutic project, including the potential for recovery as well as the possible complications associated with VA-ECMO. To maximise the benefits of VA-ECMO, the basics of extracorporeal circulation should be perfectly understood since VA-ECMO can sometimes be detrimental. Hence, to be successful, VA-ECMO should be used by teams with sufficient experience and initiated after a thorough multidisciplinary discussion considering patient's medical history, pathology as well the anticipated evolution of the disease.

Perioperative management of patients with coronary artery disease undergoing non-cardiac surgery: Summary from the French Society of Anaesthesia and Intensive Care Medicine 2017 convention.

This review summarises the specific stakes of preoperative, intraoperative, and postoperative periods of patients with coronary artery disease undergoing non-cardiac surgery. All practitioners involved in the perioperative management of such high cardiac risk patients should be aware of the modern concepts expected to decrease major adverse cardiac events and improve short- and long-term outcomes. A multidisciplinary approach via a functional heart team including anaesthesiologists, cardiologists and surgeons must be encouraged. Rational and algorithm-guided management of those patients should be known and implemented from preoperative to postoperative period.