The effectiveness of right heart catheterization in the initial care of critically ill patients. SUPPORT Investigators

A review of cardiogenic shock in acute myocardial infarction

Cardiogenic shock continues to be the most common cause of death in patients hospitalized with acute myocardial infarction. It has also been frequently associated with ST-segment elevation myocardial infarction (STEMI) and patients with co-morbidities. Cardiogenic shock presents with low systolic blood pressure and clinical signs of hypoperfusion. Rapid diagnosis and supportive therapy in the form of medications, airway support and intra-aortic balloon counterpulsation is required. Initial stabilization can be followed by reperfusion by fibrinolytic therapy, emergent percutaneous intervention (PCI) or coronary artery bypass grafting (CABG). The latter two have been found to decrease mortality in the long term. Research is being carried out on the role of inflammatory mediators in the clinical manifestation of cardiogenic shock. Mechanical support devices also show promise in the future.

Cardiac output assessed by invasive and minimally invasive techniques

Cardiac output (CO) measurement has long been considered essential to the assessment and guidance of therapeutic decisions in critically ill patients and for patients undergoing certain high-risk surgeries. Despite controversies, complications and inherent errors in measurement, pulmonary artery catheter (PAC) continuous and intermittent bolus techniques of CO measurement continue to be the gold standard. Newer techniques provide less invasive alternatives; however, currently available monitors are unable to provide central circulation pressures or true mixed venous saturations. Esophageal Doppler and pulse contour monitors can predict fluid responsiveness and have been shown to decrease postoperative morbidity. Many minimally invasive techniques continue to suffer from decreased accuracy and reliability under periods of hemodynamic instability, and so few have reached the level of interchangeability with the PAC.

Pulmonary artery catheters

BACKGROUND

After its introduction in 1970, the use of the pulmonary artery catheter became a central part of the management of critically ill patients in adult and pediatric intensive care units. However, because it was introduced as a class II device, efficacy for its safety and clinical benefit did not exist during the early years of use. This review describes the pulmonary artery catheter and reviews the literature supporting its use.

METHODOLOGY

A search of MEDLINE, PubMed, and the Cochrane Database was made to find literature about pulmonary artery catheter use. Literature for both adult and pediatric patients was reviewed. Guidelines published by the Society for Critical Care Medicine and the American Heart Association were reviewed, including further review of references cited.

RESULTS AND CONCLUSIONS

The evidence supporting the use of the pulmonary artery catheter is mostly limited to level IV (nonrandomized, historical controls, and expert opinion) and level V (case series, uncontrolled studies, and expert opinion). A higher level of evidence supports the use of the pulmonary artery catheter in selected pediatric patients, especially those with pulmonary arterial hypertension and shock refractory to standard fluid resuscitation and vasoactive agents. There are no data to suggest that use of the pulmonary artery catheter increases mortality in children.

Propensity score modelling in observational studies using dimension reduction methods

Conditional independence assumptions are very important in causal inference modelling as well as in dimension reduction methodologies. These are two very strikingly different statistical literatures, and we study links between the two in this article. The concept of covariate sufficiency plays an important role, and we provide theoretical justification when dimension reduction and partial least squares methods will allow for valid causal inference to be performed. The methods are illustrated with application to a medical study and to simulated data.

Diagnostic utility of C-reactive protein combined with brain natriuretic peptide in acute pulmonary edema: a cross sectional study

INTRODUCTION

Discriminating acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) from cardiogenic pulmonary edema (CPE) using the plasma level of brain natriuretic peptide (BNP) alone remains controversial. The aim of this study was to determine the diagnostic utility of combination measurements of BNP and C-reactive protein (CRP) in critically ill patients with pulmonary edema.

METHODS

This was a cross-sectional study. BNP and CRP data from 147 patients who presented to the emergency department due to acute respiratory failure with bilateral pulmonary infiltrates were analyzed.

RESULTS

There were 53 patients with ALI/ARDS, 71 with CPE, and 23 with mixed edema. Median BNP and CRP levels were 202 (interquartile range 95-439) pg/mL and 119 (62-165) mg/L in ALI/ARDS, and 691 (416-1,194) pg/mL (p < 0.001) and 8 (2-42) mg/L (p < 0.001) in CPE. BNP or CRP alone offered good discriminatory performance (C-statistics 0.831 and 0.887), but the combination offered greater one [C-statistics 0.931 (p < 0.001 versus BNP) (p = 0.030 versus CRP)]. In multiple logistic-regression, BNP and CRP were independent predictors for the diagnosis after adjusting for other variables.

CONCLUSIONS

Measurement of CRP is useful as well as that of BNP for distinguishing ALI/ARDS from CPE. Furthermore, a combination of BNP and CRP can provide higher accuracy for the diagnosis.

Early non-invasive cardiac output monitoring in hemodynamically unstable intensive care patients: a multi-center randomized controlled trial

INTRODUCTION

Acute hemodynamic instability increases morbidity and mortality. We investigated whether early non-invasive cardiac output monitoring enhances hemodynamic stabilization and improves outcome.

METHODS

A multicenter, randomized controlled trial was conducted in three European university hospital intensive care units in 2006 and 2007. A total of 388 hemodynamically unstable patients identified during their first six hours in the intensive care unit (ICU) were randomized to receive either non-invasive cardiac output monitoring for 24 hrs (minimally invasive cardiac output/MICO group; n = 201) or usual care (control group; n = 187). The main outcome measure was the proportion of patients achieving hemodynamic stability within six hours of starting the study.

RESULTS

The number of hemodynamic instability criteria at baseline (MICO group mean 2.0 (SD 1.0), control group 1.8 (1.0); P = .06) and severity of illness (SAPS II score; MICO group 48 (18), control group 48 (15); P = .86)) were similar. At 6 hrs, 45 patients (22%) in the MICO group and 52 patients (28%) in the control group were hemodynamically stable (mean difference 5%; 95% confidence interval of the difference -3 to 14%; P = .24). Hemodynamic support with fluids and vasoactive drugs, and pulmonary artery catheter use (MICO group: 19%, control group: 26%; P = .11) were similar in the two groups. The median length of ICU stay was 2.0 (interquartile range 1.2 to 4.6) days in the MICO group and 2.5 (1.1 to 5.0) days in the control group (P = .38). The hospital mortality was 26% in the MICO group and 21% in the control group (P = .34).

CONCLUSIONS

Minimally-invasive cardiac output monitoring added to usual care does not facilitate early hemodynamic stabilization in the ICU, nor does it alter the hemodynamic support or outcome. Our results emphasize the need to evaluate technologies used to measure stroke volume and cardiac output--especially their impact on the process of care--before any large-scale outcome studies are attempted.

TRIAL REGISTRATION

The study was registered at ClinicalTrials.gov (Clinical Trials identifier NCT00354211).

Continuous arterial pressure waveform monitoring in pediatric cardiac transplant, cardiomyopathy and pulmonary hypertension patients

PURPOSE

A continuous cardiac output monitor based on arterial pressure waveform (FloTrac/Vigileo; Edwards Lifesciences, Irvine, CA) is now approved for use in adults but not in children. This device is minimally invasive, calculates cardiac output continuously and in real time, and is easy to use. Our study sought to validate the FloTrac with the pulmonary artery catheter (PAC) intermittent thermodilution technique in pediatric cardiac patients.

METHODS

This was a prospective pilot study comparing cardiac output measurements obtained via the FloTrac and arterial pressure waveform analysis with intermittent thermodilution. Subjects carried the diagnosis of pulmonary hypertension or cardiomyopathy, or were in the postoperative course after orthotopic heart transplantation.

RESULTS

Enrolled in the study were 31 subjects, and 136 data points were obtained. The age range was 8 months to 16 years. The mean body surface area (BSA) was 1.1 m(2). Bland-Altman plots for the mean cardiac outputs of all subjects with a BSA ≥ 1 m(2) showed limits of agreement of -2.7 to 8.0 l/min (± 5.4 l/min). Patients with a BSA ≤ 1 m(2) demonstrated even wider limits of agreement (± 8.5 l/min). The intraclass correlation for the PAC was 0.929 and 0.992 for the FloTrac.

CONCLUSION

There was poor agreement between the PAC and FloTrac in measuring cardiac output in a population of children with pulmonary hypertension or cardiomyopathy, or after cardiac transplantation. This is in contrast to adult studies published thus far. This suggests that the utility of the FloTrac and measurements obtained from arterial pulse wave analysis in children is uncertain at this time.

Uncalibrated pulse power analysis fails to reliably measure cardiac output in patients undergoing coronary artery bypass surgery

Introduction

Uncalibrated arterial pulse power analysis has been recently introduced for continuous monitoring of cardiac index (CI). The aim of the present study was to compare the accuracy of arterial pulse power analysis with intermittent transpulmonary thermodilution (TPTD) before and after cardiopulmonary bypass (CPB).

Methods

Forty-two patients scheduled for elective coronary surgery were studied after induction of anaesthesia, before and after CPB respectively. Each patient was monitored with the pulse contour cardiac output (PiCCO) system, a central venous line and the recently introduced LiDCO monitoring system. Haemodynamic variables included measurement of CI derived by transpulmonary thermodilution (CI_TPTD) or CI derived by pulse power analysis (CI_PP), before and after calibration (CI_PPnon-cal., CI_PPcal.). Percentage changes of CI (ΔCI_TPTD, ΔCI_{PPnon-cal./PPcal.}) were calculated to analyse directional changes.

Results

Before CPB there was no significant correlation between CI_PPnon-cal. and CI_TPTD (r² = 0.04, P = 0.08) with a percentage error (PE) of 86%. Higher mean arterial pressure (MAP) values were significantly correlated with higher CI_PPnon-cal. (r² = 0.26, P < 0.0001). After CPB, CI_PPcal. revealed a significant correlation compared with CI_TPTD (r² = 0.77, P < 0.0001) with PE of 28%. Changes in CI_PPcal. (ΔCI_PPcal.) showed a correlation with changes in CI_TPTD (ΔCI_TPTD) only after CPB (r² = 0.52, P = 0.005).

Conclusions

Uncalibrated pulse power analysis was significantly influenced by MAP and was not able to reliably measure CI compared with TPTD. Calibration improved accuracy, but pulse power analysis was still not consistently interchangeable with TPTD. Only calibrated pulse power analysis was able to reliably track haemodynamic changes and trends.

Posttraumatic stress disorder and HIV risk among poor, inner-city women receiving care in an emergency department

OBJECTIVES

We examined the associations between posttraumatic stress disorder (PTSD) and HIV risk behaviors among a random sample of 241 low-income women receiving care in an urban emergency department.

METHODS

We recruited participants from the emergency department waiting room during randomly selected 6-hour blocks of time. Multivariate analyses and propensity score weighting were used to examine the associations between PTSD and HIV risk after adjustment for potentially confounding sociodemographic variables, substance use, childhood sexual abuse, and intimate partner violence.

RESULTS

A large majority of the sample self-identified as Latina (49%) or African American (44%). Almost one third (29%) of the participants met PTSD criteria. Women who exhibited symptoms in 1 or more PTSD symptom clusters were more likely than women who did not to report having had sex with multiple sexual partners, having had sex with a risky partner, and having experienced partner violence related to condom use in the preceding 6 months.

CONCLUSIONS

The high rate of PTSD found in this sample and the significant associations between PTSD symptom clusters and partner-related risk behaviors highlight the need to take PTSD into account when designing HIV prevention interventions for low-income, urban women.

Maintaining tissue perfusion in high-risk surgical patients: a systematic review of randomized clinical trials

BACKGROUND

Surgical patients with limited organic reserve are considered high-risk patients and have an increased perioperative mortality. For this reason, they need a more rigorous perioperative protocol of hemodynamic control to prevent tissue hypoperfusion. In this study, we systematically reviewed the randomized controlled clinical trials that used a hemodynamic protocol to maintain adequate tissue perfusion in the high-risk surgical patient.

METHODS

We searched MEDLINE, Embase, LILACS, and Cochrane databases to identify randomized controlled clinical studies of surgical patients studied using a perioperative hemodynamic protocol of tissue perfusion aiming to reduce mortality and morbidity; the latter characterized at least one dysfunctional organ in the postoperative period. Pooled odds ratio (POR) and 95% confidence interval (CI) were calculated for categorical outcomes.

RESULTS

Thirty-two clinical trials were selected, comprising 5056 high-risk surgical patients. Global meta-analysis showed a significant reduction in mortality rate (POR: 0.67; 95% CI: 0.55-0.82; P < 0.001) and in postoperative organ dysfunction incidence (POR: 0.62; 95% CI: 0.55-0.70; P < 0.00,001) when a hemodynamic protocol was used to maintain tissue perfusion. When the mortality rate was >20% in the control group, the use of a hemodynamic protocol to maintain tissue optimization resulted in a further reduction in mortality (POR: 0.32; 95% CI: 0.21-0.47; P < 0.00,001). Monitoring cardiac output with a pulmonary artery catheter and increasing oxygen transport and/or decreasing consumption also significantly reduced mortality (POR: 0.67; 95% CI: 0.54-0.84; P < 0.001 and POR: 0.71; 95% CI: 0.57-0.88; P < 0.05, respectively). Therapy directed at increasing mixed or central venous oxygen saturation did not significantly reduce mortality (POR: 0.68; 95% CI: 0.22-2.10; P > 0.05). The only study using lactate as a marker of tissue perfusion failed to demonstrate a statistically significant reduction in mortality (OR: 0.33; 95% CI: 0.07-1.65; P > 0.05).

CONCLUSIONS

In high-risk surgical patients, the use of a hemodynamic protocol to maintain tissue perfusion decreased mortality and postoperative organ failure. Monitoring cardiac output calculating oxygen transport and consumption helped to guide therapy. Additional randomized controlled clinical studies are necessary to analyze the value of monitoring mixed or central venous oxygen saturation and lactate in high-risk surgical patients.

Cross-comparison of cardiac output trending accuracy of LiDCO, PiCCO, FloTrac and pulmonary artery catheters

Introduction

Although less invasive than pulmonary artery catheters (PACs), arterial pulse pressure analysis techniques for estimating cardiac output (CO) have not been simultaneously compared to PAC bolus thermodilution CO (COtd) or continuous CO (CCO) devices.

Methods

We compared the accuracy, bias and trending ability of LiDCO™, PiCCO™ and FloTrac™ with PACs (COtd, CCO) to simultaneously track CO in a prospective observational study in 17 postoperative cardiac surgery patients for the first 4 hours following intensive care unit admission. Fifty-five paired simultaneous quadruple CO measurements were made before and after therapeutic interventions (volume, vasopressor/dilator, and inotrope).

Results

Mean CO values for PAC, LiDCO, PiCCO and FloTrac were similar (5.6 ± 1.5, 5.4 ± 1.6, 5.4 ± 1.5 and 6.1 ± 1.9 L/min, respectively). The mean CO bias by each paired method was -0.18 (PAC-LiDCO), 0.24 (PAC-PiCCO), -0.43 (PAC-FloTrac), 0.06 (LiDCO-PiCCO), -0.63 (LiDCO-FloTrac) and -0.67 L/min (PiCCO-FloTrac), with limits of agreement (1.96 standard deviation, 95% confidence interval) of ± 1.56, ± 2.22, ± 3.37, ± 2.03, ± 2.97 and ± 3.44 L/min, respectively. The instantaneous directional changes between any paired CO measurements displayed 74% (PAC-LiDCO), 72% (PAC-PiCCO), 59% (PAC-FloTrac), 70% (LiDCO-PiCCO), 71% (LiDCO-FloTrac) and 63% (PiCCO-FloTrac) concordance, but poor correlation (r² = 0.36, 0.11, 0.08, 0.20, 0.23 and 0.11, respectively). For mean CO < 5 L/min measured by each paired devices, the bias decreased slightly.

Conclusions

Although PAC (CO_TD/CCO), FloTrac, LiDCO and PiCCO display similar mean CO values, they often trend differently in response to therapy and show different interdevice agreement. In the clinically relevant low CO range (< 5 L/min), agreement improved slightly. Thus, utility and validation studies using only one CO device may potentially not be extrapolated to equivalency of using another similar device.

A systematic review and meta-analysis on the use of preemptive hemodynamic intervention to improve postoperative outcomes in moderate and high-risk surgical patients

BACKGROUND

Complications from major surgery are undesirable, common, and potentially avoidable. The long-term consequences of short-term surgical complications have recently been recognized to have a profound influence on longevity and quality of life in survivors. In the past 30 years, there have been a number of studies conducted attempting to reduce surgical mortality and morbidity by deliberately and preemptively manipulating perioperative hemodynamics. Early studies had a high control-group mortality rate and were criticized for this as being unrepresentative of current practice and raised opposition to its implementation as routine care. We performed this review to update this body of literature and to examine the effect of changes in current practice and quality of care to see whether the conclusions from previous quantitative analyses of this field remain valid.

METHODS

Randomized clinical trials evaluating the use of preemptive hemodynamic intervention to improve surgical outcome were identified using multiple methods. Electronic databases (MEDLINE, EMBASE, and the Cochrane Controlled Clinical Trials register) were screened for potential trials, reference lists of identified trials were examined, and additional sources were sought from experts and industry representatives. Identified studies that fulfilled the entry criteria were examined in full and subjected to quantifiable analysis, subgroup analysis, and sensitivity analysis where possible.

RESULTS

There were 29 studies identified, 23 of which reported surgical complications. In total, the 29 trials involved 4805 patients with an overall mortality of 7.6%. The use of preemptive hemodynamic intervention significantly reduced mortality (pooled odds ratio [95% confidence interval] of 0.48 [0.33-0.78]; P = 0.0002) and surgical complications (odds ratio 0.43 [0.34-0.53]; P < 0.0001). Subgroup analysis showed significant reductions in mortality for studies using a pulmonary artery catheter, supranormal resuscitation targets, studies using cardiac index or oxygen delivery as goals, and the use of fluids and inotropes as opposed to fluids alone. By contrast, there was a significant reduction in morbidity for each of the 4 subgroups analyzed.

CONCLUSION

The use of a preemptive strategy of hemodynamic monitoring and coupled therapy reduces surgical mortality and morbidity.

Peak cardiac power measured noninvasively with a bioreactance technique is a predictor of adverse outcomes in patients with advanced heart failure

Peak oxygen consumption (VO(2) ) during cardiopulmonary exercise testing (CPET) is a powerful predictor of survival, providing an indirect assessment of cardiac output (CO). Noninvasive indices of CO derived from bioreactance methodology would add significantly to peak VO(2) as a means of risk-stratifying patients with heart failure. In this study, 127 patients (53 ± 14 years of age, 66% male) with heart failure and an average ejection fraction of 31% ± 15% underwent symptom-limited CPET using a bicycle ergometer while measuring CO noninvasively by a bioreactance technique. Peak cardiac power was derived from the product of the peak mean arterial blood pressure and CO divided by 451. Follow-up averaged 404 ± 179 days (median, 366 days) to assess endpoints including death (n=3), heart transplant (n=10), or left ventricular assisted device implantation (n=2). Peak VO(2) and peak power had similar areas under the curve (0.77 and 0.76), which increased to 0.83 when combined. Kaplan-Meier cumulative survival curves demonstrated different outcomes in the subgroup with a VO(2) <14 mL/kg/min when stratified by a cardiac power above or below 1.5 W (92.2% vs 82.1% at 1 year and 81.6% vs 58.3% at last follow-up, P=.02 by log-rank test). Among patients with heart failure, peak cardiac power measured with bioreactance methodology and peak VO(2) had similar associations with adverse outcomes and peak power added independent prognostic information to peak VO(2) in those with advanced disease (eg, VO(2) <14 mL/kg/min).

Critical care trial design and interpretation: a primer

OBJECTIVE

Better understanding of the pathophysiology of critical illness has led to an increase in clinical trials designed to improve the clinical care and outcomes of patients with life-threatening illness. Knowledge of basic principles of clinical trial design and interpretation will assist the clinician in better applying the results of these studies into clinical practice.

DATA SOURCES

We review selected clinical trials to highlight important design features that will improve understanding of the results of critical care clinical trials designed to improve clinical care of the critically ill.

RESULTS

Trial design features such as patient selection, bias, sample size calculation, selection of subjects and controls, and primary outcome measure may influence the results of a critical care clinical trial designed to test a therapy targeting improved clinical care. In conjunction with trial design knowledge, understanding the size of the anticipated treatment effect, the importance of any clinical end point achieved, and whether patients in the trial are representative of typical patients with the illness will assist the reader in determining whether the results should be applied to specific patients or usual clinical practice.

CONCLUSIONS

Better understanding of important aspects of trial design and interpretation, such as whether patients enrolled in both intervention arms were comparable and whether the primary outcome of the trial is clinically important, will assist the bedside clinician in determining whether to apply the findings from the clinical study into clinical practice.

Minimally invasive monitoring of cardiac output in the cardiac surgery intensive care unit

Cardiac output monitoring in the cardiac surgery patient is standard practice that is traditionally performed using the pulmonary artery catheter. However, over the past 20 years, the value of pulmonary artery catheters has been challenged, with some authors suggesting that its use might be not only unnecessary but also harmful. New minimally invasive devices that measure cardiac output have become available. In this paper, we review their operative principles, limitations, and utility in an integrated approach that could potentially change patients' outcome. However, it is now clear that it is how the monitor is used (ie, the protocol or therapy associated with its use, or its lack thereof), and not the monitor per se, that should be questioned when a patient's outcome is being evaluated.

Sepsis and septic shock: pathophysiological and cardiovascular background as basis for therapy

INTRODUCTION

Sepsis and septic shock are common causes for admission to intensive care units. The morbidity and mortality remain unacceptably high despite the advanced treatments.

OBJECTIVES

To review the most commonly reported underlying mechanisms of sepsis and septic shock, besides discussion of sepsis-induced cardiovascular dysfunction. Therapeutic strategies for sepsis-induced myocardial depression are briefly discussed.

DATA SYNTHESIS

The development of sepsis and septic shock is multifactorial. Two major mechanisms contribute to the haemodynamic collapse. The extrinsic and intrinsic mechanisms induce a complex cascade which results in the release of pro- and anti-inflammatory mediators. Sepsis develops when the initial, appropriate host response to an infection becomes amplified and then dysregulated leading to haemodynamic and circulatory changes. The pro-inflammatory mediators tumour necrosis factor alpha, interleukin-beta and nitric oxide play a significant role in sepsis-related hypotension, shock and depression of cardiomyocyte contractility. Septic cardiac dysfunction can be explained by various mechanisms: changes in circulating volume, down-regulation of beta-adrenergic receptors, depressed post-receptor signalling pathways, reduced calcium release from the sarcoplasmic reticulum and impaired electromechanical coupling and reduced calcium sensibility at the myofibrillar level. Mitochondrial derangement seems to be of great importance in tissue injury and sepsis-associated multi organ failure. There is no consistent protocol for treating sepsis and septic shock. Guidelines include early goal-directed therapy, source control and haemodynamic supportive measures.

CONCLUSION

Further studies are needed to distinguish the importance of these various mechanisms. We recommend that further investigational work should focus on the recovery of the mitochondria-related bio-energetic shut down as the mitochondria could play a key role in the understanding of apoptosis and protective measures. Understanding the pathophysiology of sepsis and septic shock will inevitably lead to a more accurate treatment of these still too often fatal syndromes.

A novel noninvasive ultrasonic cardiac output monitor: comparison with cardiac magnetic resonance

BACKGROUND

USCOM, a novel continuous wave Doppler (CWD) device, has been introduced for noninvasive determination of cardiac output (CO). The present study aimed to compare the accuracy and reproducibility of the new device, using cardiovascular magnetic resonance imaging (CMR) as the noninvasive gold standard.

METHODS AND RESULTS

The CO of 56 consecutive patients was prospectively determined by CWD either before or after CMR imaging. The CWD probe was placed in the suprasternal or supraclavicular notch aiming at the aortic valve. Valid CWD signals could be obtained in 45 patients yielding a CO of 5.3+/-1.1 L/min (range, 3.0-7.5 L/min) by CMR and 4.7+/-1.1 L/min by CWD (2.5-8.0 L/min, P = .004), respectively. CWD measurements showed an acceptable agreement with CMR (bias: 0.6+/-1.1 L/min) and a high reproducibility (bias: 0.1+/-0.4 L/min). Higher CO and body mass index (BMI) were identified as sources of inaccuracy in univariate analysis. By multivariate analysis, only CO(CMR) was found to be independently associated with larger variation. Estimated diameters of the left ventricular outflow tract (LVOT), a prerequisite for CO measurement by CWD, correlated only weakly with those measured by CMR.

CONCLUSIONS

Continuous wave Doppler is a feasible technique for measuring cardiac function. Although the overall agreement with CMR was acceptable, CWD showed a trend to underestimate CO. The estimated LVOT diameter by CWD is likely to be an important source of error. Nevertheless, the CWD device could be of clinical use especially for detection of intraindividual hemodynamic changes since a high reproducibility could be demonstrated.

Clinical evaluation of the flotrac/Vigileo system for continuous cardiac output monitoring in patients undergoing regional anesthesia for elective cesarean section: a pilot study

BACKGROUND

Spinal anesthesia for cesarean delivery may cause severe maternal hypotension and a decrease in cardiac output. Compared to assessment of cardiac output via a pulmonary artery catheter, the FloTrac/Vigileo system may offer a less invasive technique. The aim of this study was to evaluate cardiac output and other hemodynamic measurements made using the FloTrac/Vigileo system in patients undergoing spinal anesthesia for elective cesarean section.

METHODS

A prospective study enrolling 10 healthy pregnant women was performed. Hemodynamic parameters were continuously obtained at 15 main points: admission to surgery (two baseline measurements), after preload, after spinal anesthesia administration and 4 time points thereafter (4, 6, 8 and 10 min after anesthesia), at skin and uterine incision, newborn and placental delivery, oxytocin administration, end of surgery, and recovery from anesthesia. Hemodynamic therapy was guided by mean arterial pressure, and vasopressors were used as appropriate to maintain baseline values. A repeated measures ANOVA was used for data analysis.

RESULTS

There was a significant increase in heart rate and a decrease of stroke volume and stroke volume index up to 10 min after spinal anesthesia (P < 0.01). Importantly, stroke volume variation increased immediately after newborn delivery (P < 0.001) and returned to basal values at the end of surgery. Further hemodynamic parameters showed no significant changes over time.

DISCUSSION AND CONCLUSIONS

No significant hemodynamic effects, except for heart rate and stroke volume changes, were observed in pregnant women managed with preload and vasopressors when undergoing elective cesarean section and spinal anesthesia.

Characterizing the risk profiles of intensive care units

OBJECTIVE

To develop a new method to evaluate the performance of individual ICUs through the calculation and visualisation of risk profiles.

METHODS

The study included 102,561 patients consecutively admitted to 77 ICUs in Austria. We customized the function which predicts hospital mortality (using SAPS II) for each ICU. We then compared the risks of hospital mortality resulting from this function with the risks which would be obtained using the original function. The derived risk ratio was then plotted together with point-wise confidence intervals in order to visualise the individual risk profile of each ICU over the whole spectrum of expected hospital mortality.

MAIN MEASUREMENTS AND RESULTS

We calculated risk profiles for all ICUs in the ASDI data set according to the proposed method. We show examples how the clinical performance of ICUs may depend on the severity of illness of their patients. Both the distribution of the Hosmer-Lemeshow goodness-of-fit test statistics and the histogram of the corresponding P values demonstrated a good fit of the individual risk models.

CONCLUSIONS

Our risk profile model makes it possible to evaluate ICUs on the basis of the specific risk for patients to die compared to a reference sample over the whole spectrum of hospital mortality. Thus, ICUs at different levels of severity of illness can be directly compared, giving a clear advantage over the use of the conventional single point estimate of the overall observed-to-expected mortality ratio.

Critical care of the hematopoietic stem cell transplant recipient

An estimated 50,000 to 60,000 patients undergo hematopoietic stem cell transplantation (HSCT) worldwide annually, of which 15.7% are admitted to the intensive care unit (ICU). The most common reason for ICU admission is respiratory failure and almost all develop single or multiorgan failure. Most HSCT recipients admitted to ICU receive invasive mechanical ventilation (MV). The overall short-term mortality rate of HSCT recipients admitted to ICU is 65%, and 86.4% for those receiving MV. Patient outcome has improved over time. Poor prognostic indicators include advanced age, poor functional status, active disease at transplant, allogeneic transplant, the severity of acute illness, and the development of multiorgan failure. ICU resource limitations often lead to triage decisions for admission. For HSCT recipients, the authors recommend (1) ICU admission for full support during their pre-engraftment period and when there is no evidence of disease recurrence; (2) no ICU admission for patients who refuse it and those who are bedridden with disease recurrence and without treatment options except palliation; (3) a trial ICU admission for patients with unknown status of disease recurrence with available treatment options.

Stroke volume variation as a guide to fluid administration in morbidly obese patients undergoing laparoscopic bariatric surgery

BACKGROUND

Perioperative fluid administration in morbidly obese patients is critical. There is scarcity of scientific information in literature on amount and rate of its application. Functional parameters (stroke volume variation (SVV), pulse pressure variation) are considered more accurate predictor of volume status of patients than blood pressure and central venous pressure.

METHODS

SVV was used as a guide for intraoperative fluid administration in 50 morbidly obese patients subjected to bariatric surgery. Pulse contour waveform analysis (LiDCO Cardiac Sensor System, UK Company Regd. 2736561, VAT Regd. 672475708) was utilized to monitor SVV, and a value more than 10% was used as infusion trigger for intraoperative fluid management.

RESULTS

Mean amount of fluid infused was 1,989.90 ml (+/-468.70 SD) for mean 206.94 min (+/-50.30 SD) duration of surgery. All patients maintained hemodynamic parameters (cardiac output, cardiac index, stroke volume, noninvasive blood pressure, heart rate) within 10% of the baseline values. Central venous pressure and SVV showed no correlation, except for short period initially. Renal and metabolic indices remained within normal limits.

CONCLUSION

Obese patients coming for laparoscopic bariatric surgery may not require excessive fluid. Intraoperative fluid requirement is the same as for nonobese patients. SVV is a valuable guide for fluid application in obese patients undergoing bariatric surgery.

Perforation of the right ventricle induced by pulmonary artery catheter at induction of anesthesia for the surgery for liver transplantation: a case report and reviewed of literature

We report a case of a 45-year-old male patient diagnosed with liver cirrhosis by hepatitis C and alcohol, with a Child-Pugh score C and a model for end-stage liver disease (MELD) score of 27, and submitted to liver transplantation. The subject underwent insertion of the pulmonary artery catheter (PAC) in the right internal jugular vein, with technical difficulty concerning catheter advance. There was sudden hypotension, increase in central venous pressure (CVP), and decrease in SvO₂ 15 minutes after the PAC had been inserted, followed by cardiorespiratory arrest in pulseless electrical activity (PEA), which was promptly assisted with resuscitation. Pericardiocentesis was performed without success, so the individual was subjected to a subxiphoid pericardial window, which led to output of large amounts of blood as well as PEA reversal to sinus rhythm. Sternotomy was performed; rupture of the apex of the right ventricle (RV) was detected, and suture of the site was accomplished. After hemodynamic stabilization, the patient was transferred to the ICU, where he developed septic shock and, despite adequate therapy, died on the eighteenth day after ICU admission.

Pulmonary artery catheters in acute heart failure: end of an era?

Whereas the pulmonary artery catheter (PAC) is still widely used in guiding assessment and treatment of heart failure, controversy surrounding its safety and efficacy has prompted development of newer, less invasive techniques. For these purposes, the transpulmonary thermodilution technique allows assessment of preload, cardiac output, filling volumes, and metrics of contractility without the need to pass a catheter through the right heart. In a previous issue of Critical Care, Ritter and colleagues compare metrics of transpulmonary thermodilution with the PAC in patients with acute heart failure and severe sepsis. The results add to a growing body of evidence that the PAC adds little to information attainable by less invasive methods in many conditions, including acute heart failure. Whether newer devices improve outcome needs to be tested in well-controlled prospective trials.

Complication rates among trauma centers

BACKGROUND

The goal of this study was to examine the association between patient complications and admission to Level I trauma centers (TC) compared with nontrauma centers (NTC).

STUDY DESIGN

This was a retrospective cohort study of data derived from the National Study on the Costs and Outcomes of Trauma (NSCOT). Patients were recruited from 18 Level I TCs and 51 NTCs in 15 regions encompassing 14 states. Trained study nurses, using standardized forms, abstracted the medical records of the patients. The overall number of complications per patient was identified, as was the presence or absence of 13 specific complications.

RESULTS

Patients treated in TCs were more likely to have any complication compared with patients in NTCs, with an adjusted relative risk (RR) of 1.34 (95% CI, 1.03, 1.74). For individual complications, only the urinary tract infection RR of 1.94 (95% CI, 1.07, 3.17) was significantly higher in TCs. TC patients were more likely to have 3 or more complications (RR, 1.83; 95% CI, 1.16, 2.90). Treatment variables that are surrogates for markers of injury severity, such as use of pulmonary artery catheters, multiple operations, massive transfusions (> 2,500 mL packed red blood cells), and invasive brain catheters, occurred significantly more often in TCs.

CONCLUSIONS

Trauma centers have a slightly higher incidence rate of complications, even after adjusting for patient case mix. Aggressive treatment may account for a significant portion of TC-associated complications. Pulmonary artery catheter use and intubation had the most influence on overall TC complication rates. Additional study is needed to provide accurate benchmark measures of complication rates and to determine their causes.

Clinical review: Goal-directed therapy in high risk surgical patients

A small group of patients account for the majority of peri-operative morbidity and mortality. These 'high-risk' patients have a poor outcome due to their inability to meet the oxygen transport demands imposed on them by the nature of the surgical response during the peri-operative period. It has been shown that by targeting specific haemodynamic and oxygen transport goals at any point during the peri-operative period, the outcomes of these patients can be improved. This goal directed therapy includes the use of fluid loading and inotropes, in order to optimize the preload, contractility and afterload of the heart whilst maintaining an adequate coronary perfusion pressure. Despite the benefits seen, it remains a challenge to implement this management due to difficulties in identifying these patients, scepticism and lack of critical care resources.

Oesophageal Doppler Ultrasound in the Assessment of Haemodynamic Status of Patients Admitted to the Medical Intensive Care Unit with Septic Shock

Introduction: Haemodynamic monitoring is an essential element in the management of critically ill patients in the intensive care unit (ICU). However, there have been increasing concerns about the clinical utility and safety profile of the invasive pulmonary artery catheter (PAC). Oesophageal Doppler (ED) monitoring has emerged recently as a safer and less invasive tool which can be used by the intensivist to estimate cardiac output in the critically ill patient. Validation studies have thus far only been performed in surgical patients perioperatively and in mixed surgical/medical ICU patients. Currently, minimal data are available in any sizeable Asian population or in patients with severe sepsis. The assumption that these normograms and data hold true for our local medical ICU patients may not be valid due to differences in body habitus. Materials and Methods: Our primary aim is to validate the oesophageal Doppler as a reliable measure of cardiac index, systemic vascular resistance (SVR) and preload in our local Asian population of patients with severe sepsis and septic shock in the medical ICU. This was a prospective pilot study on 12 consecutive mechanically ventilated patients in our medical ICU with the diagnosis of septic shock as defined by SCCM/ESICM/ACCP/ATS/SIS International Sepsis definitions Conference – Critical Care Medicine 2003 and required PAC haemodynamic monitoring as indicated by Medical Intensive Care Unit attending. Results: Ninety-seven paired cardiac output measurements were made. Cardiac output ranged from 2.87 to 11.0 L/ min (calculated cardiac index ranging from 1.73 to 6.36 L/min/m2) when measured using the PAC with thermodilution technique and from 2.0 to 12.1 L/min (calculated cardiac index of 1.2 to 7.2 L/min/m2) using the trans-oesophageal Doppler. There was moderately good correlation between CIpac and CIed (correlation coefficient, r = 0.762 with PCA = 58%). The mean bias was 0.26 L/min/m2 (P <0.07), while the limit of agreement was ± 1.44 L/min/m2. Conclusion: ED has good correlation with PAC in measuring cardiac index in Asians with septic shock but is an unreliable measure of both pre-load and SVR. Key words: Cardiac index, Pulmonary artery cathether, Systemic vascular resistance

Non-invasive stroke volume measurement and passive leg raising predict volume responsiveness in medical ICU patients: an observational cohort study

Introduction

The assessment of volume responsiveness and the decision to administer a fluid bolus is a common dilemma facing physicians caring for critically ill patients. Static markers of cardiac preload are poor predictors of volume responsiveness, and dynamic markers are often limited by the presence of spontaneous respirations or cardiac arrhythmias. Passive leg raising (PLR) represents an endogenous volume challenge that can be used to predict fluid responsiveness.

Methods

Medical intensive care unit (ICU) patients requiring volume expansion were eligible for enrollment. Non-invasive measurements of stroke volume (SV) were obtained before and during PLR using a transthoracic Doppler ultrasound device prior to volume expansion. Measurements were then repeated following volume challenge to classify patients as either volume responders or non-responders based on their hemodynamic response to volume expansion. The change in SV from baseline during PLR was then compared with the change in SV with volume expansion to determine the ability of PLR in conjunction with SV measurement to predict volume responsiveness.

Results

A total of 102 fluid challenges in 89 patients were evaluated. In 47 of the 102 fluid challenges (46.1%), SV increased by ≥15% after volume infusion (responders). A SV increase induced by PLR of ≥15% predicted volume responsiveness with a sensitivity of 81%, specificity of 93%, positive predictive value of 91% and negative predictive value of 85%.

Conclusions

Non-invasive SV measurement and PLR can predict fluid responsiveness in a broad population of medical ICU patients. Less than 50% of ICU patients given fluid boluses were volume responsive.

Continuous cardiac index monitoring: A prospective observational study of agreement between a pulmonary artery catheter and a calibrated minimally invasive technique

INTRODUCTION

Continuous cardiac index (CCI) monitoring can provide information to assist in hemodynamic support. However, pulmonary artery catheters (PAC) pose logistic challenges in acute care settings. We hypothesized that CCI measured with a calibrated minimally invasive technique (LiDCO/PulseCO, UK) would have good agreement with the PAC.

METHODS

We performed a prospective observational study in post-operative cardiac surgery patients. All patients had a PAC with CCI monitoring capability. We connected the LiDCO apparatus to a radial artery line and performed a one-time calibration with a lithium dilution indicator. In order to test the least invasive method possible, we used a peripheral intravenous (IV) line for indicator delivery rather than the conventional central line technique. We recorded paired PAC/LiDCO-PulseCO CCI measurements every minute for 3h. We blinded investigators and clinicians to minimally invasive data with an opaque shield over the monitor. We assessed agreement with Bland-Altman analysis.

RESULTS

We obtained 1485 paired measurements in 8 subjects. The mean CI was 2.9L/min/m(2). By Bland-Altman plot, PAC and LiDCO measurements showed minimal bias (-0.01), but the 95% limits of agreement (+/-2SD) of+/-1.3L/min/m(2) were relatively wide with respect to the mean.

CONCLUSIONS

This calibrated minimally invasive (i.e. radial arterial line and peripheral IV) technique demonstrated low bias compared with CCI measured by PAC. However, the relatively wide confidence limits indicate that differences in the two measurements could still be clinically significant.

Nurse-determined assessment of cardiac output. Comparing a non-invasive cardiac output device and pulmonary artery catheter: a prospective observational study

BACKGROUND

The accurate measurement of Cardiac output (CO) is vital in guiding the treatment of critically ill patients. Invasive or minimally invasive measurement of CO is not without inherent risks to the patient. Skilled Intensive Care Unit (ICU) nursing staff are in an ideal position to assess changes in CO following therapeutic measures. The USCOM (Ultrasonic Cardiac Output Monitor) device is a non-invasive CO monitor whose clinical utility and ease of use requires testing.

OBJECTIVES

To compare cardiac output measurement using a non-invasive ultrasonic device (USCOM) operated by a non-echocardiograhically trained ICU Registered Nurse (RN), with the conventional pulmonary artery catheter (PAC) using both thermodilution and Fick methods.

DESIGN

Prospective observational study.

SETTING AND PARTICIPANTS

Between April 2006 and March 2007, we evaluated 30 spontaneously breathing patients requiring PAC for assessment of heart failure and/or pulmonary hypertension at a tertiary level cardiothoracic hospital.

METHODS

SCOM CO was compared with thermodilution measurements via PAC and CO estimated using a modified Fick equation. This catheter was inserted by a medical officer, and all USCOM measurements by a senior ICU nurse. Mean values, bias and precision, and mean percentage difference between measures were determined to compare methods. The Intra-Class Correlation statistic was also used to assess agreement. The USCOM time to measure was recorded to assess the learning curve for USCOM use performed by an ICU RN and a line of best fit demonstrated to describe the operator learning curve.

RESULTS

In 24 of 30 (80%) patients studied, CO measures were obtained. In 6 of 30 (20%) patients, an adequate USCOM signal was not achieved. The mean difference (+/-standard deviation) between USCOM and PAC, USCOM and Fick, and Fick and PAC CO were small, -0.34+/-0.52 L/min, -0.33+/-0.90 L/min and -0.25+/-0.63 L/min respectively across a range of outputs from 2.6L/min to 7.2L/min. The percent limits of agreement (LOA) for all measures were -34.6% to 17.8% for USCOM and PAC, -49.8% to 34.1% for USCOM and Fick and -36.4% to 23.7% for PAC and Fick. Signal acquisition time reduced on average by 0.6 min per measure to less than 10 min at the end of the study.

CONCLUSIONS

In 80% of our cohort, USCOM, PAC and Fick measures of CO all showed clinically acceptable agreement and the learning curve for operation of the non-invasive USCOM device by an ICU RN was found to be satisfactorily short. Further work is required in patients receiving positive pressure ventilation.

Invasive monitoring in patients with heart failure

The syndrome of heart failure is characterized by symptoms that are relatively insensitive and nonspecific. Physical diagnosis may be unreliable even in the hands of experienced clinicians, despite the presence of significantly elevated filling pressures or a significantly depressed cardiac output. Instrumentation and devices such as the insertion of a pulmonary artery catheter and the implantable hemodynamic monitor have a major role in the diagnosis and management of cardiovascular disease. They provide a means of measuring intracardiac pressures for point-in-time measurements (cardiac catheterization), short term in an acute situation (insertion of a pulmonary arterial catheter), and, more recently, a long-term assessment increasing our understanding of the nuances of the hemodynamic derangements associated with heart failure and other conditions. With improved ability to accurately assess and monitor filling pressures, clinicians can more precisely adjust therapy with the goal of improving patient symptoms and possibly outcomes.

The right ventricle in sepsis

Right ventricular dysfunction is common in sepsis and septic shock because of decreased myocardial contractility and elevated pulmonary vascular resistance despite a concomitant decrease in systemic vascular resistance. The mainstay of treatment for acute right heart failure includes treating the underlying cause of sepsis and reversing circulatory shock to maintain tissue perfusion and oxygen delivery. Decreasing pulmonary vascular resistance with selective pulmonary vasodilators is a reasonable approach to improving cardiac output in septic patients with right ventricular dysfunction. Treatment for right ventricular dysfunction in the setting of sepsis should concentrate on fluid repletion, monitoring for signs of RV overload, and correction of reversible causes of elevated pulmonary vascular resistance, such as hypoxia, acidosis, and lung hyperinflation.

Assessment of cardiac output changes using a modified FloTrac/Vigileo algorithm in cardiac surgery patients

INTRODUCTION

The FloTrac/Vigileo (Edwards Lifesciences, Irvine, CA, USA) allows pulse pressure-derived cardiac output measurement without external calibration. Software modifications were performed in order to eliminate initially observed deficits. The aim of this study was to assess changes in cardiac output determined by the FloTrac/Vigileo system (FCO) with an initially released (FCOA) and a modified (FCOB) software version, as well as changes in cardiac output from the PiCCOplus system (PCO; Pulsion Medical Systems, Munich, Germany). Both devices were compared with cardiac output measured by intermittent thermodilution (ICO).

METHODS

Cardiac output measurements were performed in patients after elective cardiac surgery. Two sets of data (A and B) were obtained using FCOA and FCOB in 50 patients. After calibration of the PiCCOplus system, triplicate FCO and PCO values were recorded and ICO was determined in the supine position and cardiac output changes due to body positioning were recorded 15 minutes later (30 degrees head-up, 30 degrees head-down, supine). Student's t test, analysis of variance and Bland-Altman analysis were calculated.

RESULTS

Significant changes of FCO, PCO and ICO induced by body positioning were observed in both data sets. For set A, DeltaFCOA was significantly larger than DeltaICO induced by positioning the head down. For set B, there were no significant differences between DeltaFCOB and DeltaICO. For set A, increased limits of agreement were found for FCOA-ICO when compared with PCO-ICO. For set B, mean bias and limits of agreement were comparable for FCOB-ICO and PCO-ICO.

CONCLUSIONS

The modification of the FloTrac/Vigileo system resulted in an improved performance in order to reliably assess cardiac output and track the related changes in patients after cardiac surgery.