Estimating the rapid haemodynamic effects of passive leg raising in critically ill patients using bioreactance.

BACKGROUND: Rapid detection of changes in cardiac index (CI) in real time using minimally invasive monitors may be of clinical benefit. We tested whether the Starling-SV bioreactance device, which averages CI over a short 8 s period, could assess the effects of passive leg raising (PLR), a clinical test that is recommended to assess fluid responsiveness during septic shock. METHODS: In 32 critically ill patients, we measured CI by transpulmonary thermodilution (PiCCO2, CItd), pulse contour analysis (PiCCO2, CIPulse), and the Starling-SV device (CIStarling) at baseline. CIPulse and CIStarling were measured again at the end of a PLR test. In the 13 patients with a positive PLR test, CItd, CIPulse, and CIStarling were measured before and after a 500 ml saline infusion. The primary outcome was relative changes from baseline measurements in CItd, CIPulse, and CIStarling. Secondary outcomes compared absolute values measured by each method. RESULTS: Relative changes in CIPulse and CItd were significantly correlated (r=0.82; n=45; P<0.001), with an 89% concordance rate (n=45 paired measurements). Relative changes in CIStarling and CItd were also significantly correlated (r=0.59; n=45; P<0.001) with a 78% concordance rate. For absolute measures of CI (n=77 paired measurements), the bias between CIPulse and CItd was 0.01 L min-1 m-2 (limits of agreement, -0.49 and 0.51 L min-1 m-2; 15% percentage error). Bias between CIStarling and CItd was 0.03 L min-1 m-2 (limits of agreement, -1.61 and 1.67 L min-1 m-2; 48% percentage error). CONCLUSIONS: In critically ill patients, a non-invasive bioreactance device with a shorter averaging period assessed a passive leg raising test with reasonable accuracy.

Norepinephrine exerts an inotropic effect during the early phase of human septic shock.

BACKGROUND: We conducted this study to investigate whether norepinephrine increases cardiac contractility when administered during the early phase of septic shock. METHODS: We studied 38 patients with septic shock who had been resuscitated for <3 h and whose mean arterial pressure (MAP) remained <65 mm Hg. Echocardiographic variables were obtained before (T0) and after either initiation or an increase in the dose of a norepinephrine infusion to increase MAP to ≥ 65 mm Hg (T1). We collected left ventricular ejection fraction (LVEF), velocity-time integral of the left ventricular outflow tract (VTI), tissue Doppler imaging of mean systolic velocity of the lateral tricuspid annulus (Sa) and of the lateral mitral annulus (Sm), and tricuspid annular plane systolic excursion (TAPSE). RESULTS: There were significant (P<0.05) increases from T0 to T1 in MAP [mean (sd): from 56 (7) to 80 (9) mm Hg], LVEF [from 49 (13) to 56 (13)%], VTI [from 18 (5) to 20 (6) cm], Sm [from 10.8 (5.1) to 12.1 (5.0) cm s-1], TAPSE [from 1.8 (0.5) to 2.0 (0.5) cm], and Sa [from 13.0 (5.6) to 15.1 (6.4) cm s-1]. In the subgroup of 15 patients with LVEF ≤45%, significant increases in VTI [from 16 (8) to 18 (7) cm] and in LVEF [from 36 (7) to 44 (10)%] were observed. CONCLUSIONS: Norepinephrine administration during early resuscitation in patients with septic shock increased the cardiac systolic function despite the presumed increase in left ventricular afterload secondary to the increased arterial pressure. Whether such an effect persists over time remains to be evaluated. CLINICAL TRIAL REGISTRATION: NCT02750683.

Comparison of pulse contour analysis by Pulsioflex and Vigileo to measure and track changes of cardiac output in critically ill patients.

BACKGROUND: We compared the new Pulsioflex and the Vigileo devices to measure cardiac index (CI) in critically ill patients. Both devices measure CI by pulse-contour analysis. The Pulsioflex device also allows an auto-calibration (not based on thermodilution). METHODS: Patients were included if we administered fluids (20 patients), reduced (20 patients), or increased (20 patients) the dose of norepinephrine. Before and after interventions, we measured CI provided by the Vigileo (CIVig) and Pulsioflex (CIPfx) devices before and after its auto-calibration. CI measured by transpulmonary thermodilution (CIthermo) was used as the reference. RESULTS: Considering absolute values of CI (n=120), the percentage error was 59% for CIVig vs CIthermo and 40% for CIthermo vs CIPfx. Auto-calibrating CIPfx after interventions did not improve the percentage error between CIPfx and CIthermo (39%). Considering the fluid-induced changes in CI, the coefficient of correlation with changes in CIthermo was 0.50 for CIVig, and 0.73 for CIPfx (P=0.27). It was not significantly improved if CIPfx was auto-calibrated (r=0.64). Considering the norepinephrine-induced changes in CI, the coefficient of correlation with changes in CIthermo was 0.41 for CIVig. It tended to be better for CIPfx (r=0.71, P=0.07). It was not significantly improved by auto-calibration (r=0.53). CONCLUSIONS: The Pulsioflex did not reliably estimate the absolute values of CI. For tracking fluid-induced changes in CI, the Pulsioflex was reliable, and also the Vigileo. For tracking norepinephrine-induced changes in CI, it was also reliable and tended to be better than the Vigileo. Auto-calibration allowed by the system did not improve its reliability.

Assessment of changes in left ventricular systolic function with oesophageal Doppler.

BACKGROUND: We tested the ability of mean acceleration (Acc) and peak velocity (V peak) of the aortic velocity signal measured by oesophageal Doppler to reflect left ventricular (LV) systolic performance. METHODS: We included critically ill patients in whom a fluid challenge (n=25) or the introduction of dobutamine, 5 µg kg(-1) min(-1) (n=25), was planned by the attending physician. Before and after therapeutic interventions, we measured Acc and V peak (CardioQ device) and LV ejection fraction (LVEF) using echocardiography. RESULTS: For all pairs of measurements, the absolute values of Acc and V peak correlated with LVEF (r=0.36 and 0.57, respectively). The correlation was significantly higher for V peak than for Acc. Volume expansion did not significantly change LVEF and Acc, but significantly increased V peak by 7 (8)%. Dobutamine increased LVEF by 30 (15)%, Acc by 33 (25)%, and V peak by 20 (10)%. Considering the pooled effects of volume expansion and dobutamine, changes in Acc and V peak and those of LVEF were correlated (r=0.53 and 0.67, respectively). When excluding changes <18% (i.e. the least significant change for LVEF), the concordance rate was 96% for Acc and 100% for V peak. CONCLUSIONS: V peak and, to a lesser extent, Acc measured by oesophageal Doppler behaved as markers of LV systolic performance as they were almost insensitive to fluid administration and changed to a much larger extent with dobutamine. These indices could be used to estimate LV systolic performance and to assess the effects of inotropic therapy.

Bioreactance is not reliable for estimating cardiac output and the effects of passive leg raising in critically ill patients.

BACKGROUND: Bioreactance estimates cardiac output in a non-invasive way. We evaluated the ability of a bioreactance device (NICOM®) to estimate cardiac index (CI) and to track relative changes induced by volume expansion. METHODS: In 48 critically ill patients, we measured CI estimated by the NICOM® device (CINicom) and by transpulmonary thermodilution (CItd, PiCCO2™ device) before and after a 500 ml saline infusion. Before volume expansion, we performed a passive leg raising (PLR) test and measured the changes it induced in CINicom and in pulse contour analysis-derived CI. RESULTS: Considering the values recorded before PLR and before and after volume expansion (n=144), the bias (lower and upper limits of agreement) between CItd and CINicom was 0.9 (-2.2 to 4.1) litre min(-1) m(-2). The percentage error was 82%. There was no significant correlation between the changes in CItd and CINicom induced by volume expansion (P=0.24). An increase in CI estimated by pulse contour analysis >9% during the PLR test predicted fluid responsiveness with a sensitivity of 84% (95% confidence interval 60-97%) and a specificity of 97% (95% confidence interval 82-100%). The area under the receiver operating characteristic curve constructed to test the ability of the PLR-induced changes in CINicom in predicting fluid responsiveness did not differ significantly from 0.5 (P=0.77). CONCLUSIONS: The NICOM® device cannot accurately estimate the cardiac output in critically ill patients. Moreover, it could not predict fluid responsiveness through the PLR test.

Pleth variability index is a weak predictor of fluid responsiveness in patients receiving norepinephrine.

BACKGROUND: In patients receiving an infusion of norepinephrine, the relationship between the amplitude of the oximeter plethysmographic waveform and stroke volume may be variable and quality of the waveform might be reduced, compared with patients not receiving norepinephrine. We assessed the reliability of the pleth variability index (PVI), an automatic measurement of the respiratory variation of the plethysmographic waveform, for predicting fluid responsiveness in patients receiving norepinephrine infusions. METHODS: We measured the response of cardiac index (transpulmonary thermodilution) to i.v. fluid administration in 42 critically ill patients receiving norepinephrine. Patients with arrhythmias, spontaneous breathing, tidal volume <8 ml kg(-1), and respiratory system compliance <30 ml cm H(2)O(-1) were excluded. Before fluid administration, we recorded the arterial pulse pressure variation (PPV) and pulse contour analysis-derived stroke volume variation (SVV, PiCCO2) and PVI (Masimo Radical-7). RESULTS: In seven patients, the plethysmographic signal could not be obtained. Among the 35 remaining patients [mean SAPS II score=77 (sd=17)], i.v. fluid increased cardiac index ≥15% in 15 'responders'. A baseline PVI ≥16% predicted fluid responsiveness with a sensitivity of 47 (inter-quartile range=21-73)% and a specificity of 90 (68-99)%. The area under the receiver operating characteristic curve was significantly lower for PVI [0.68 (0.09)] than for PPV and SVV [0.93 (0.06) and 0.89 (0.07), respectively]. Considering all pairs of measurements, PVI was correlated with PPV (r(2)=0.27). The fluid-induced changes in PVI and PPV were not significantly correlated. CONCLUSIONS: PVI was less reliable than PPV and SVV for predicting fluid responsiveness in critically ill patients receiving norepinephrine. In addition, PVI could not be measured in a significant proportion of patients. This suggests that PVI is not useful in patients receiving norepinephrine.

Third-generation FloTrac/Vigileo does not reliably track changes in cardiac output induced by norepinephrine in critically ill patients.

BACKGROUND: The ability of the third-generation FloTrac/Vigileo software to track changes in cardiac index (CI) induced by volume expansion and norepinephrine in critically ill patients is unknown. METHODS: In subjects with circulatory failure, we administered volume expansion (20 subjects) and increased (20 subjects) or decreased (20 subjects) the dose of norepinephrine. We measured arterial pressure waveform-derived CI provided by the third-generation FloTrac/Vigileo device (CI(pw)) and transpulmonary thermodilution CI (CI(td)) before and after therapeutic interventions. RESULTS: Considering the pairs of measurements performed before and after all therapeutic interventions (n=60), a bias between the absolute values of CI(pw) and CI(td) was 0.26 (0.94) litre min(-1) m(-2) and the percentage error was 54%. Changes in CI(pw) tracked changes in CI(td) induced by volume expansion with moderate accuracy [n=20, bias=-0.11 (0.54) litre min(-1) m(-2), r(2)=0.26, P=0.02]. When changes in CI(td) were induced by norepinephrine (n=40), a bias between CI(pw) and CI(td) was 0.01 (0.41) litre min(-1) m(-2) (r(2)=0.11, P=0.04). The concordance rates between changes in CI(pw) and CI(td) induced by volume expansion and norepinephrine were 73% and 60%, respectively. The bias between changes in CI(pw) and CI(td) significantly correlated with changes in total systemic vascular resistance (r(2)=0.41, P<0.0001). CONCLUSIONS: The third-generation FloTrac/Vigileo device was moderately reliable for tracking changes in CI induced by volume expansion and poorly reliable for tracking changes in CI induced by norepinephrine.

Prediction of fluid responsiveness by a continuous non-invasive assessment of arterial pressure in critically ill patients: comparison with four other dynamic indices.

BACKGROUND: We evaluated the ability of an infrared photoplethysmography arterial waveform (continuous non-invasive arterial pressure, CNAP) to estimate arterial pulse pressure variation (PPV). We compared the ability of non-invasive PPV to predict fluid responsiveness with invasive PPV, respiratory variation of pulse contour-derived stroke volume, and changes in cardiac index induced by passive leg raising (PLR) and end-expiratory occlusion (EEO) tests. METHODS: We measured the responses of cardiac index (PiCCO) to 500 ml of saline in 47 critically ill patients with haemodynamic failure. Before fluid administration, we recorded non-invasive and invasive PPVs, stroke volume variation, and changes in cardiac index induced by PLR and by 15 s EEO. Logistic regressions were performed to investigate the advantage of combining invasive PPV, stroke volume variation, PLR, and EEO when predicting fluid responsiveness. RESULTS: In eight patients, CNAP could not record arterial pressure. In the 39 remaining patients, fluid increased cardiac index by ≥15% in 17 'responders'. Considering the 195 pairs of measurements, the bias (sd) between invasive and non-invasive PPVs was -0.6 (2.3)%. The areas under the receiver operating characteristic (ROC) curves for predicting fluid responsiveness were 0.89 (95% confidence interval, 0.78-1.01) for non-invasive PPV compared with 0.89 (0.77-1.01), 0.84 (0.70-0.96), 0.95 (0.88-1.03), and 0.97 (0.91-1.03) for invasive pulse pressure, stroke volume variations, PLR, and EEO tests (no significant difference). Combining multiple tests did not significantly improve the area under the ROC curves. CONCLUSIONS: Non-invasive assessment of PPV seems valuable in predicting fluid responsiveness.

[The Script Concordance Test: A multimodal teaching tool]. / Le test de concordance de script : un outil pédagogique multimodal.

In recent years, there has been a major interest in assessing learners during their medical education. The core of medical competence is the clinical reasoning that should be acquired by all medical actors. Its assessment includes the ability to integrate and apply different types of knowledge, weigh critical evidence and think about the process used to have a diagnosis. French faculties of medicine will have to include it in the training and evaluation of students during 2017. It should therefore be part of the new docimological modalities of the computerized "Épreuves Classantes Nationales" from 2020 onwards. In this article, we did a specific review of the literature concerning the theoretical foundations, methodology and use of Script Concordance Test (SCT) in the field of health. To do so, we used the PubMed, EMBASE and PsycINFO databases and selected articles in English and French language using the following keywords alone or in combination: script, concordance, script concordance test, medical studies, validity, fidelity, psychometric properties. We have found 62 articles that matched our search. Built on a well-targeted methodology, the SCT is a reliable and valid pedagogical tool. It can discriminate the levels of practice between medical students, residents and medical doctors, evaluate the progression and skills of clinical reasoning. It can be administered online, in multicentric centers, at a national or international level. There are, however, limitations that teachers must take into account.

Heart rate reduction by inhibition of If or by beta-blockade has different effects on postsystolic wall thickening.

BACKGROUND AND PURPOSE: Postsystolic wall thickening (PSWT) is part of thickening that occurs after end-systole and represents wasted effort as it does not contribute to ejection. The effects of antianginal drugs on PSWT remain to be established. We compared the effects on PSWT of two agents that reduce heart rate, the beta-blocker atenolol and the selective inhibitor of If current, ivabradine. EXPERIMENTAL APPROACH: Six dogs were prepared to measure wall thickening by sonomicrometry in the conscious state, at rest and during exercise, after administration of saline, atenolol (1 mg.kg-1) or ivabradine (1 mg.kg-1). KEY RESULTS: Atenolol and ivabradine similarly reduced heart rate vs saline at rest (about 10-20%) and during exercise (about 30%). Atenolol but not ivabradine decreased dP/dtmax. Concomitantly, PSWT increased with atenolol vs saline at rest (0.35+/-0.07 vs 0.21+/-0.03 mm, respectively) and during exercise (0.30+/-0.04 vs 0.15+/-0.04 mm, respectively). In contrast, ivabradine did not alter PSWT. Importantly, atenolol but not ivabradine increased the ratio of postsystolic to systolic wall thickening by 80+/-23%. This enhanced thickening during diastole with atenolol was accompanied by impeded isovolumic relaxation of the left ventricle, as illustrated by the significant correlation between the isovolumic relaxation time constant tau and the postsystolic to systolic wall thickening ratio. None of these effects of atenolol were abolished when heart rate was controlled with atrial pacing. CONCLUSION AND IMPLICATIONS: For a similar heart rate reduction at rest and during exercise, ivabradine, but not atenolol, did not alter PSWT and preserved the part of thickening contributing to ejection.

Rapid and beneficial hemodynamic effects of activated protein C in septic shock patients.

OBJECTIVE: Because recombinant human activated protein C (rhAPC) reduces NO production during sepsis, it could improve the vascular tone. We tested whether rhAPC reduces the dose of norepinephrine required to maintain mean arterial pressure (MAP) in septic shock patients. DESIGN AND SETTING: Retrospective study in intensive care unit of two university hospitals. PATIENTS: Twenty-two septic shock patients with at least two organ failures were retrospectively investigated for MAP and the required dose of norepinephrine before and 24 h after rhAPC administration. A control group of 22 septic shock patients with at least two organ failures who did not receive rhAPC was matched on age, SAPS II, MAP, and norepinephrine dose at the time of the theoretical start of rhAPC. MEASUREMENTS AND RESULTS: The MAP remained stable and similar in the two groups (86+/-16 vs. 89+/-9 mmHg at 24 h). The required dose of norepinephrine increased in the control group (+38%, from -41% to +38%) but decreased in the treated group (-33%, from -74% to +11%). CONCLUSIONS: rhAPC rapidly improved the vascular tone in septic shock patients as assessed by a decrease in the norepinephrine dose required to maintain arterial pressure.

Pulse pressure variation and ARDS.

Fluid management is a crucial issue in patients with acute respiratory distress syndrome (ARDS). Assessment of preload responsiveness should help to define the best fluid strategy. Arterial pulse pressure variation (PPV), which represents the amplitude of the respiratory changes in arterial pulse pressure, is considered as a marker of preload responsiveness in patients mechanically ventilated and fully adapted to their ventilator. The good ability of PPV to predict fluid responsiveness has been confirmed in various clinical situations (sepsis, operative and post-operative periods). However, there are a number of limits of using PPV (e.g., spontaneous breathing activity, cardiac arrhythmias, low tidal volume ventilation, low lung compliance), which are particularly important in ARDS. Clinical studies have confirmed the poor reliability of PPV in predicting fluid responsiveness in patients with ARDS, ventilated according to the currently recommended lung protective strategy. Although a PPV >10-12% still keeps its good predictive value, a lower PPV (<10%) is far to guarantee fluid unresponsiveness since many false-negative cases can be encountered in this setting. Thus, performance of alternative preload responsiveness tests such as passive leg raising or end-expiratory occlusion tests, is necessary when low PPV values are measured. This review addresses the meaning of PPV, its conditions of use and its limits in ARDS patients.

Hemolysis and schistocytosis in the emergency department: consider pseudothrombotic microangiopathy related to vitamin B12 deficiency.

BACKGROUND: Hemolytic anemia with thrombocytopenia and schistocytosis is suggestive of thrombotic thrombocytopenic purpura (TTP). However, these features can occur in the context of vitamin B12 deficiency. AIM: To identify simple means of distinguishing between TTP and pseudothrombotic microangiopathies related to vitamin B12 deficiency (pseudo-TMA) at the bedside. DESIGN AND METHODS: Retrospective study of patients with pseudo-TMA compared with patients with TTP. The patients with pseudo-TMA were further compared with other cases of cobalamin deficiency, in order to detect factors associated with microangiopathic hemolysis during vitamin B12 deprivation. RESULTS: Seven patients with pseudo-TMA were compared with six patients with TTP. The pseudo-TMA patients had higher median lactate dehydrogenase (LDH) levels (7310 vs. 1460 IU/l, P = 0.01), a higher platelet count (73 vs.12.5 × 10(9)/l, P = 0.0023), a lower reticulocyte count (13.1 vs. 265.5 × 10(9)/l, P = 0.0012) and a lower neutrophil count (1.3 vs. 5.1 × 10(9)/l, P = 0.0023). When compared with 21 patients with vitamin B12 deficiency and anemia (but no schistocytosis), the pseudo-TMA patients were more likely to present with pernicious anemia [7 out of 21 (33.3%) vs. 5 out of 7 (71.4%), respectively] and had lower vitamin B12 levels (105 vs. 45 µmol/l, respectively). Vitamin supplementation led to hematological improvements in all pseudo-TMA patients. CONCLUSION: In a context of mechanical hemolysis with thrombocytopenia in a patient admitted to the emergency department, very high LDH levels and a low reticulocyte count are strongly suggestive of pseudo-TMA and should prompt the physician to screen for cobalamin deficiency.

[Field 6. Safety practices for haemodynamic procedures (administration of vasoactive drugs, vascular and cardiac catheterization). French-speaking Society of Intensive Care. French Society of Anesthesia and Resuscitation]. / Champ 6. Sécurisation des procédures "circulatoires" (administration des substances vasoactives, utilisation des cathéters artériels, veineux centraux et artériels pulmonaires). SRLF. SFAR.

Arterial and central venous catheterizations and their use for continuous infusion of vasoactive drugs could lead to serious adverses events that could be life threatening. The incidence of human errors related patient adverses events could be decreased by the uses of algorithms and procedures. Concerning the continuous infusion of vasoactive drugs, the name of drug and its concentration should be clearly notified. The use of modern pump and noncompliant pipe could reduce the frequency bolus infusion and their related haemodynamic alterations. Reasonable procedure could reduce the arterial and central venous catheters related complications. Subclavian and radial sites should be preferred for central venous and arterial catheter insertion, respectively. The use of real time echographic guidance could facilitate the catheter insertion. These catheters should be removed when they are not indicated. Concerning the pulmonary artery catheter, the balloon tip should be inflated with visual control of the pulmonary artery pressure. Its removal is recommended within the first five days.

Meaning of arterio-venous PCO2 difference in circulatory shock.

The arterovenous difference in carbon dioxide tension (DeltaPCO2) can be calculated after simultaneous sampling of arterial blood (PaCO2) and of mixed venous blood from the distal of a pulmonary artery catheter (PvCO2). Under physiological conditions, DeltaPCO2 ranges from 2 to 5 mmHg. The DeltaPCO2 depends on carbon dioxide and cardiac output by a complex fashion. In this article, we detail the influence of these factors on DeltaPCO2 in normoxic conditions and in hypoxic conditions. We bring evidence that DeltaPCO2 cannot serve as a marker of tissue hypoxia contrary to what was initially thought. However, DeltaPCO2 can be considered as a marker of the adequacy of venous blood flow (i.e. cardiac output) to remove the total CO2 produced by the peripheral tissues. In this regard, the knowledge of DeltaPCO2 should help the clinicians for the decision of giving therapy aimed at increasing cardiac output.

The pulmonary artery catheter in critically ill patients. Does it change outcome?

Initially described more than 30 years ago, the Pulmonary Artery Catheter (PAC) technique was becoming more and more used in the following years. This hemodynamic monitoring device can be used according 2 different therapeutic attitudes. The first one strives to achieve supranormal hemodynamic values, particularly in terms of cardiac index and oxygen consumption. However, this attitude has been demonstrated to be deleterious in the intensive care setting and is, to date, strongly questioned in the perioperative period. Conversely, the use of PAC to optimize the hemodynamic status in an individualized manner appears more seductive, even if the impact of a therapeutic attitude guided by standardized protocols has never been investigated. Although the PAC affords a continuous monitoring of a large panel of hemodynamic data, including tissue oxygenation parameters and estimation of left cardiac filling pressures, some pitfalls may occur in the measurement as well as in the interpretation of the data. Furthermore, because it is an invasive procedure, the safety of the PAC has been seriously questioned for several years. However, the recent study of Richard and coworkers clearly demonstrated that the use of PAC was not responsible for increased mortality in severely ill patients with circulatory shock and/or acute respiratory distress syndrome. The development of educational programs would allow to improve the quality of the collection and interpretation of hemodynamic parameters with the hope to enhance the efficiency of the PAC for the management of critically ill patients.