RETRACTED ARTICLE: Noninvasive assessment of cardiac output using thoracic electrical bioimpedance in hemodynamically stable and unstable patients after cardiac surgery: a comparison with pulmonary artery thermodilution

Objective To compare noninvasive cardiac output (CO)measurement obtained with a new thoracic electrical bioimpedance (TEB) device, using a proprietary modification of the impedance equation, with invasive measurement obtained via pulmonary artery thermodilution.Design Prospective, observational study.Setting Surgical intensive care unit (ICU) of a university-affiliated community hospital.Patients and participants Seventy-four adult patients undergoing elective cardiac surgery with routine pulmonary artery catheter placement.Interventions None.Measurements and results Simultaneous paired CO and cardiac index (CI) measurements by TEB and thermodilution were obtained in mechanically ventilated patients upon admission to the ICU. For analysis of CI data the patients were subdivided into a hemodynamically stable group and a hemodynamically unstable group. The groups were analyzed using linear regression and tests of bias and precision. We found a significant correlation between thermodilution and TEB (r = 0.83; n< 0.001), accompanied by a bias of –0.01 l/min/m² and a precision of ±0.57 l/min/m² for all CI data pairs. Correlation, bias, and precision were not influenced by stratification of the data. The correlation coefficient, bias, and precision for CI were 0.86 (n< 0.001), 0.03 l/min/m², and ±0.47 l/min/m² in hemodynamically stable patients and 0.79 (n< 0.001), 0.06 l/min/m², and ±0.68 l/min/m² in hemodynamically unstable patients.Conclusions Our results demonstrate a close correlation and clinically acceptable agreement and precision between CO measurements obtained with impedance cardiography using a new algorithm to calculate CO from variations in TEB, and those obtained with the clinical standard of care, pulmonary artery thermodilution, in hemodynamically stable and unstable patients after cardiac surgery.     

Noninvasive cardiac output monitoring (NICOM): a clinical validation

OBJECTIVE: To evaluate the clinical utility of a new device for continuous noninvasive cardiac output monitoring (NICOM) based on chest bio-reactance compared with cardiac output measured semi-continuously by thermodilution using a pulmonary artery catheter (PAC-CCO). DESIGN: Prospective, single-center study. SETTING: Intensive care unit. PATIENTS: Consecutive adult patients immediately after cardiac surgery. INTERVENTIONS: Cardiac output measurements obtained from NICOM and thermodilution were simultaneously recorded minute by minute and compared in 110 patients. We evaluated the accuracy, precision, responsiveness, and reliability of NICOM for detecting cardiac output changes. Tolerance for each of these parameters was specified prospectively. MEASUREMENTS AND RESULTS: A total of 65,888 pairs of cardiac output measurements were collected. Mean reference values for cardiac output ranged from 2.79 to 9.27 l/min. During periods of stable PAC-CCO (slope<+/-10%, 2SD/mean<20%), the correlation between NICOM and thermodilution was R=0.82; bias was +0.16+/-0.52 l/min (+4.0+/-11.3%), and relative error was 9.1%+/-7.8%. In 85% of patients the relative error was <20%. During periods of increasing output, slopes were similar with the two methods in 96% of patients and intra-class correlation was positive in 96%. Corresponding values during periods of decreasing output were 90% and 84%, respectively. Precision was always better with NICOM than with thermodilution. During hemodynamic challenges, changes were 3.1+/-3.8 min faster with NICOM (p<0.01) and amplitude of changes did not differ significantly. Finally, sensitivity of the NICOM for detecting significant directional changes was 93% and specificity was 93%. CONCLUSION: Cardiac output measured by NICOM had most often acceptable accuracy, precision, and responsiveness in a wide range of circulatory situations.     

Interleukin-10, T-lymphocytes, and cardiac output in children after ventricular septal defect repair: a pilot study

Objective To evaluate the acute inflammatory response and cardiac output in children after surgery for ventricular septal defect.Design and setting Prospective, observational study in a level III multidisciplinary neonatal and pediatric intensive care unit.Patients Ten children undergoing open-heart surgery for ventricular septal defect.Interventions All children received methylprednisolone (30 mg/kg) in cardiopulmonary bypass (CPB) prime.Measurements and results Before and after cardiopulmonary bypass, plasma interleukin-10 and tumor necrosis factor α were measured by enzyme-linked immunosorbent assay, and lymphocyte subsets in peripheral blood by flow cytometry. Relative values (post-/pre-CPB) of interleukin-10 and tumor necrosis factor α were calculated. The cardiac index (CI) was measured continuously beat-to-beat by a pulse contour analysis (PiCCO). Children above the cutoff value (median cardiac index value 3.0 l min^{– 1} m^{– 2}) were designated as the normal CI group and those below this value as the low CI group. In the normal CI group the relative values of interleukin-10 remained almost seven times higher than pre-CPB values at 24 h while in the low CI group they decreased almost to pre-CPB values. Furthermore, the normal CI group, but not the low CI group, exhibited more than threefold decrease in T-lymphocytes (lymphocyte T-cells, T-helper cells, and cytotoxic T-cells) 24 h after CPB.Conclusions Children operated on for ventricular septal defect developed either a normal or low CI. The higher relative values of interleukin-10 and lower counts of lymphocyte T-cells, T-helper and cytotoxic T-cells differentiated the normal CI group from the low CI group at 24 h after cardiopulmonary bypass.     

Dextran-70 to modulate inflammatory response after cardiopulmonary bypass: potential for a novel approach?

Potential deleterious effects of cardiopulmonary bypass (CPB) and cardioplegic cardiac arrest are known to influence outcome. The inflammatory response after CPB may have unfavourable effects especially in high-risk patients, for example, the very elderly. Thus, to blunt the release of pro-inflammatory mediators seems to be a promising approach. So far, numerous attempts at immune modulation have been performed. However, the management of cardiac surgery patients needs further improvement. In this context, Gombocz and colleagues investigated the potential anti-inflammatory effect of dextran-70. Their results suggest that compared to gelatine, dextran-70 reduces the inflammatory response in patients after CPB.     

Oxygen consumption after cardiac surgery —a comparison between calculation by Fick's principle and measurement by indirect calorimetry

Oxygen consumption calculated by Fick's principle (c ₂) was compared to oxygen consumption measured (m ₂) by indirect calorimetry (Deltatrac Metabolic Computer) in 10 patients in the post-operative period after cardiac surgery. For 50 pairs of measurements the mean difference (m ₂–c ₂) was 34±27ml/min·m². The limits of agreement were –20ml/min·m² to 88ml/min·m². These results showed that c ₂ and m ₂ were not interchangeable in this study.     

Does modified ultrafiltration reduce the systemic inflammatory response to cardiac surgery with cardiopulmonary bypass?

Cardiopulmonary bypass (CPB) is associated with an accumulation of total body water and a systemic inflammatory response syndrome (SIRS), which, in turn, is associated with organ dysfunction and postoperative morbidity. It has been suggested that modified ultrafiltration (MUF) may be capable of reducing SIRS and improving clinical outcome by filtering out the inflammatory mediators generated during CPB. This paper reviews the data regarding the use of MUF in paediatric and adult settings. Specifically, three issues will be considered: 1) Does MUF improve clinical outcome? 2) Does MUF reduce the systemic inflammatory response to cardiac surgery with CPB? 3) Is MUF more effective than conventional ultrafiltration in improving clinical outcome?     

Emergency department initiation of cardiopulmonary bypass: a case report and review of the literature

Background

Out-of-hospital cardiac arrest carries a dismal prognosis. Percutaneous extracorporeal membrane oxygenation (ECMO) has been used with success for in-hospital arrests, and some literature suggests improvement in long-term survival for out-of-hospital arrests as well.

Objectives

This case highlights the use of ECMO in the emergency department.

Case Report

We report a case in which emergency physician-initiated ECMO was used as a bridge to definitive care in an out-of- hospital cardiac arrest in the United States.

Conclusions

ECMO is a novel adjunct for patients in cardiac arrest in whom the usual advanced life support techniques have failed.     

Pexelizumab – a C5 complement inhibitor for use in both acute myocardial infarction and cardiac surgery with cardiopulmonary bypass

Myocardial injury and dysfunction in acute infarction and during cardiac surgery with cardiopulmonary bypass (CPB) are associated with an undesirable systemic inflammatory response, in which the complement cascade plays a major role. In animal models C5 inhibition has been found to significantly reduce myocardial infarct size and decrease cellular necrosis and apoptosis. Pexelizumab (Alexion Pharmaceuticals, Inc., Cheshire, CT, USA) is a humanised, monoclonal, single-chain antibody fragment that inhibits C5, thereby blocking its cleavage into active forms. Prospective, randomised, double-blind, placebo-controlled trials using pexelizumab during percutaneous coronary intervention following acute myocardial infarction (AMI), or in patients undergoing coronary artery bypass graft (CABG) with CPB, have demonstrated a reduction in morbidity and mortality. Thus, pexelizumab represents a promising therapeutic option with sustained benefit both in AMI and during CABG with CPB.     

Intraoperative renal near-infrared spectroscopy indicates developing acute kidney injury in infants undergoing cardiac surgery with cardiopulmonary bypass: a case–control study

IntroductionAcute kidney injury (AKI) is a frequent complication after cardiac surgery with cardiopulmonary bypass in infants. Renal near-infrared spectroscopy (NIRS) is used to evaluate regional oximetry in a non-invasive continuous real-time fashion, and reflects tissue perfusion. The aim of this study was to evaluate the relationship between renal oximetry and development of AKI in the operative and post-operative setting in infants undergoing cardiopulmonary bypass surgery.MethodsIn this prospective study, we enrolled 59 infants undergoing cardiopulmonary bypass surgery for congenital heart disease for univentricular (n = 26) or biventricular (n = 33) repair. Renal NIRS was continuously measured intraoperatively and for at least 24 hours postoperatively and analysed for the intraoperative and first 12 hours, first 24 hours and first 48 hours postoperatively. The renal oximetry values were correlated with the paediatric risk, injury, failure, loss, end (pRIFLE) classification for AKI, renal biomarkers and the postoperative course.ResultsTwenty-eight (48%) infants developed AKI based on pRIFLE classification. Already during intraoperative renal oximetry and further in the first 12 hours, 24 hours and 48 hours postoperatively, significantly lower renal oximetry values in AKI patients compared with patients with normal renal function were recorded (P < 0.05). Of the 28 patients who developed AKI, 3 (11%) needed renal replacement therapy and 2 (7%) died. In the non-AKI group, no deaths occurred. Infants with decreased renal oximetry values developed significantly higher lactate levels 24 hours after surgery. Cystatin C was a late parameter of AKI, and neutrophil gelatinase-associated lipocalin values were not correlated with AKI occurrence.ConclusionOur results suggest that prolonged low renal oximetry values during cardiac surgery correlate with the development of AKI and may be superior to conventional biochemical markers. Renal NIRS might be a promising non-invasive tool of multimodal monitoring of kidney function and developing AKI in infants undergoing cardiac surgery with cardiopulmonary bypass.     

The compromised inflammatory response to bacterial components after pediatric cardiac surgery is associated with cardiopulmonary bypass–suppressed Toll-like receptor signal transduction pathways

Purpose

Cardiopulmonary bypass (CPB) during pediatric cardiac surgery often elicits a systemic inflammatory response followed by a compromised immune response, which has been attributed to the morbidity of postoperative infection; however, the underlying mechanism(s) has not yet been fully elucidated. We hypothesized that CPB inhibits the activation of Toll-like receptor (TLR) signal transduction pathways, thereby causing an immunosuppressive state after pediatric cardiac surgery.

Methods

We examined 20 children with congenital heart disease undergoing pediatric cardiac surgery.

Results

Cardiopulmonary bypass differentially affected lipopolysaccharide (LPS)- or bacterial lipoprotein (BLP)–stimulated ex vivo production of proinflammatory and anti-inflammatory cytokines, with significantly diminished tumor necrosis factor α, interleukin (IL) 1β, IL-6, and IL-8, but substantially enhanced IL-10 production. Consistent with the reduced inflammatory response, CPB strongly inhibited LPS- or BLP-activated TLR signal transduction pathways in monocytes with down-regulated expression of CD14, TLR4, and TLR2 and with suppressed phosphorylation of nuclear factor κB p65, p38, and extracellular signal-regulated kinase 1/2.

Conclusions

These results indicate that CPB during pediatric cardiac surgery causes substantially reduced production of inflammatory cytokines in response to bacterial component LPS or BLP stimulation, which is associated with CPB-induced suppression of TLR-mediated signal transduction pathways. This reduced inflammatory response after CPB in children with congenital heart disease may predispose them to an increased risk of postoperative infection.     

Bench-to-bedside review: The importance of the precision of the reference technique in method comparison studies – with specific reference to the measurement of cardiac output

Bland-Altman analysis is used for assessing agreement between two measurements of the same clinical variable. In the field of cardiac output monitoring, its results, in terms of bias and limits of agreement, are often difficult to interpret, leading clinicians to use a cutoff of 30% in the percentage error in order to decide whether a new technique may be considered a good alternative. This percentage error of ± 30% arises from the assumption that the commonly used reference technique, intermittent thermodilution, has a precision of ± 20% or less. The combination of two precisions of ± 20% equates to a total error of ± 28.3%, which is commonly rounded up to ± 30%. Thus, finding a percentage error of less than ± 30% should equate to the new tested technique having an error similar to the reference, which therefore should be acceptable. In a worked example in this paper, we discuss the limitations of this approach, in particular in regard to the situation in which the reference technique may be either more or less precise than would normally be expected. This can lead to inappropriate conclusions being drawn from data acquired in validation studies of new monitoring technologies. We conclude that it is not acceptable to present comparison studies quoting percentage error as an acceptability criteria without reporting the precision of the reference technique.