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Year in review 2005: Critical Care – cardiology
Timothy Gatheral, E David Bennett
Critical Care , 2006, DOI: 10.1186/cc4983
Abstract: This review article summarizes original research papers in cardiology and critical care published in 2005 in Critical Care. The papers are grouped into topics for ease of reference.The volume of distribution of intravenous glucose can be used to estimate central extracellular fluid volume and cardiac preload. Ishihara and colleagues [1] assessed the utility of standard arterial blood gas/glucose analyzers found in the intensive care unit (ICU) in accurate calculation of this volume. Previous work by the group [2] demonstrated that injection of a small bolus of glucose (5 g) followed by serial measurements of glucose concentration from arterial samples allowed calculation of the initial distribution volume of glucose (IDVG). This calculated volume was independent of pre-injection glucose concentration and concomitant infusions of glucose and/or insulin. Animal studies by the group showed a close correlation between IDVG and intrathoracic blood volume, implying clinical utility as a marker of cardiac preload [3]. Their recent study [1] used preinjectate and 3 min glucose concentrations to derive approximated IDVG. The approximated IVDG was shown to correlate well with original IDVG (the calculated volume using their original multi-sampling methodology), although the two values are not interchangeable. This paper suggests a simple way to derive cardiac preload utilizing standard techniques and equipment. Further research is needed to assess the accuracy of haemodynamic data provided by this modified technique and its practical application in the ICU.Wiesenack and coworkers [4] examined the use of a novel pulmonary artery catheter (PAC) technique to assess fluid responsiveness. A rapid response thermistor at the tip of the modified PAC allows near continuous measurement of right ventricular ejection fraction and derivation of continuous right ventricular end-diastolic volume (CEDV). Previous studies [5-7] suggested good correlation between right ventricular end-diastoli
Year in review 2011: Critical Care - cardiology
Daniel De Backer, Diego Orbegozo Cortés
Critical Care , 2012, DOI: 10.1186/cc11826
Abstract: We review key research papers in intensive care cardiology published during 2011 in Critical Care. Related studies published in other journals are also discussed, whenever appropriate.Inotropic agents are used to increase oxygen delivery in the perioperative setting but their impact on mortality is not well defined. In a retrospective study including 1,326 cardiac surgery patients, those exposed to inotropes had, as expected, a higher unadjusted mortality rate than those patients not exposed [1]. After adjustment, inotrope exposure was still associated with increased hospital mortality and renal dysfunction. A propensity score-matched analysis yielded similar results. A limitation of this trial is that this type of analysis only takes into account measured variables, but other factors may play a role. Postoperative inotrope exposure may thus be associated with worse outcomes, but this should be tested in interventional trials.Should nonadrenergic inotropic agents be preferred? A meta-analysis evaluated the effects of levosimendan, versus control, in patients after percutaneous or surgical cardiac revascularization [2]. The meta-analysis included 729 patients from 17 studies. Levosimendan increased the cardiac index. Compared with controls, levosimendan treatment was associated with a mortality reduction after coronary revascularization (odds ratio = 0.40, 95% confidence interval (CI) = 0.21 to 0.76) and a reduction in the length of ICU stay. An important limitation of this analysis is that most of the studies included were small sized, and that there was an important heterogeneity in dosing and time of administration of levosimendan as well as in drugs used in the control arms. This potentially beneficial effect of levosimendan should be evaluated in a large-scale randomized trial.Another meta-analysis evaluated the renal effects of carperitide, an atrial natriuretic peptide, and nesiritide, a B-type natriuretic peptide (BNP) [3]. The systematic review included 15 s
Year in review 2006: Critical Care – cardiology
Nawaf Al-Subaie, David Bennett
Critical Care , 2007, DOI: 10.1186/cc5978
Abstract: Successful use of central venous oxygen saturation (ScvO2) in the management of early sepsis [1] has led to interest in the use of this variable in high-risk patients who are undergoing major surgery, in whom the concept of goal-directed therapy is well established [2-4]. The collaborative study group on perioperative ScvO2 monitoring has conducted a multicentre pilot study to assess the incidence of low ScvO2 in high-risk surgical patients and its impact on outcome in terms of postoperative complications. Takala and coworkers [5] included all patients satisfying two or more of the criteria proposed by Shoemaker and coworkers [2], who were undergoing major surgery, defined as an intra-abdominal or retroperitoneal procedure with an expected duration of at least 90 min. In the 60 patients studied, low perioperative ScvO2 was associated with a greater risk for complications, with a mean value of 73% for discriminating between patients who did and those who did not develop complications (72% sensitivity and 61% specificity). This is in close agreement with values observed in healthy volunteers [6] and, more importantly, with the 8-hour postoperative mean ScvO2 of 75% seen in the complication-free patients in the optimization study conducted by Pearse and coworkers [7].The group was successful in establishing grounds for an interventional trial with ScvO2 as a therapeutic goal, within the context of other physiological targets, in perioperative settings in which a value of 75% is targeted with intravenous fluids and inotropes. Until such a study has been completed, use of this physiological variable in the perioperative setting should be considered with care [8].Sander and colleagues [9] were first to report the wide discrepancy between cardiac output measured using new arterial waveform analysis hardware that is claimed not to require any calibration [10,11] (Flotrac sensor and Vigileo monitor; Edwards Lifesciences, Irvine, CA, USA) and cardiac output measured using the
Year in review 2008: Critical Care - cardiology
Luigi Camporota, Marius Terblanche, David Bennett
Critical Care , 2009, DOI: 10.1186/cc8025
Abstract: Cardiac troponins (cTns) are highly sensitive and specific biological markers of myocardial damage. Elevated cTn is an independent predictor of adverse outcome and correlates with intensive care unit (ICU) and hospital lengths of stay among critically ill patients, regardless of the mechanism causing its rise [1-3]. However, because ICU patients often have increased cTn for reasons other than overt myocardial infarction (MI), raised cTn may be attributed to other conditions, and therefore the true incidence of myocardial damage in ICU may be underestimated.Lim and colleagues [4] screened patients admitted to ICU by using cTn and electrocardiograms (ECGs) to determine the incidence of elevated cTn and MI and to assess whether these findings influence prognosis. In this study, patients were classified as having MI in the presence of elevated cTn and ECG evidence supporting a diagnosis of MI. Among 103 patients, 35.9% had a confirmed MI whereas 14.6% had an elevated cTn only. Patients with an MI or with elevated cTn without ECG changes had a longer duration of mechanical ventilation and ICU stay and higher ICU and hospital mortality rates compared with patients with no cTn elevation (odds ratio 27.3). Lim and colleagues [4] found that screening cTn measurements and 12-lead ECGs detected MI at a higher rate than clinical diagnosis alone, suggesting that the true incidence and associated mortality of MI in ICU patients are underestimated.Increased levels of brain natriuretic peptide (BNP) and the biologically inactive N-terminal pro-BNP (NT-proBNP) are associated with impaired left ventricular (LV) function and ischaemia, pulmonary embolism (PE) and chronic obstructive pulmonary disease [5].Coutance and colleagues [6] conducted a meta-analysis of studies in patients with acute PE to assess the prognostic value of elevated BNP or NT-proBNP levels to predict short-term overall mortality, PE-specific mortality and the occurrence of serious pre-defined adverse events. The st
Year in review 2010: Critical Care - neurocritical care
Michael T Scalfani, Michael N Diringer
Critical Care , 2011, DOI: 10.1186/cc10423
Abstract: Several important contributions to the field of neurocritical care were published in Critical Care during 2010. These articles can be gathered into six key areas: diagnostic criteria, delirium and encephalopathy, predicting neurologic outcome after cardiac arrest, subarachnoid hemorrhage (SAH) and outcome from neurocritical care.Favorable outcome from bacterial meningitis requires rapid diagnosis and immediate initiation of antibiotic therapy [1], yet distinguishing between bacterial and nonbacterial meningitis can sometimes prove difficult. The use of cerebrospinal fluid (CSF) lactate, as opposed to conventional tests (such as CSF glucose, CSF/plasma glucose ratio, CSF protein concentration, and CSF leukocyte count), has been investigated in a number of studies to distinguish between bacterial and nonbacterial meningitis.Huy and coworkers performed a literature review and meta-analysis to evaluate the usefulness of CSF lactate concentration for this purpose [2]. From the 25 studies they identified, the authors concluded that CSF lactate alone had a high degree of accuracy in distinguishing between bacterial and nonbacterial meningitis and performs better than the conventional tests routinely used. CSF lactate was found to be less useful if its concentration was low, but when elevated it was helpful, especially if the diagnosis was otherwise inconclusive. This suggests that any elevation in CSF lactate concentration above normal for the assay used could be employed as a diagnostic marker despite the difference in cut-off values caused by variance in methods, instruments and hospital laboratories. While the authors conclude CSF lactate is a useful marker to distinguish between bacterial and nonbacterial meningitis, it is not meant to replace conventional tests as they are necessary to diagnose meningitis. Rather, interpretation of lactate alone is a better discriminator between bacterial and nonbacterial meningitis than conventional tests. As a result, measurements o
Year in review 2010: Critical Care - infection
Leonardo Pagani, Arash Afshari, Stephan Harbarth
Critical Care , 2011, DOI: 10.1186/cc10425
Abstract: Infections remain among the most important concerns in critically ill patients. Early and reliable diagnosis of infection still poses difficulties in this setting but also represents a crucial step toward an appropriate anti-microbial therapy that avoids the perils of excessive antibiotic exposure. Increasing antimicrobial resistance challenges established approaches to the optimal management of infections in the intensive care unit (ICU). Rapid infection diagnosis, antibiotic dosing and optimization through pharmacologic indices, progress in the implementation of effective antimicrobial stewardship programs, and management of fungal infections are some of the most relevant issues in this special patient population. Here, we briefly review the results from selected studies published on those topics in 2010 and take a special interest in articles published in Critical Care. Other important subjects like H1N1 influenza virus infection and prevention of nosocomial infection were discussed in last year's review in Critical Care [1] and will be summarized only briefly.Since they detect viable microorganisms that can be further characterized by molecular or biochemical techniques, blood cultures are still considered the gold standard to diagnose bloodstream infection (BSI) and to identify the species and determine their antimicrobial susceptibility. However, blood cultures are far from being an ideal gold standard as they often provide results with delay, are incomplete, and may not reflect all microbiological evidence important for clinical decision making [2]. Recent technological advances such as the development of fully automated instruments and the application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) have reduced identification time to 4 hours, once blood cultures have become positive [3]. Various technologies based on nucleic acid extraction (nucleic acid testing) from positive blood cultures hold some promise [4].
Year in review 2010: Critical Care - respirology
Vito Fanelli, Haibo Zhang, Arthur S Slutsky
Critical Care , 2011, DOI: 10.1186/cc10541
Abstract: Treatment of acute respiratory failure is one of the most difficult challenges in intensive care unit (ICU) management. The most important advance in decreasing mortality in patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) has been the use of a low-tidal volume, lung protective ventilation strategy [1]. As such, there has been extensive research to explore the mechanisms of ALI in order to develop novel therapeutic approaches. Here, we review the key respiratory failure papers that appeared last year in Critical Care.Ventilation and perfusion mismatch, as a consequence of lung injury, leads to hypoxemia and can lead to hypercapnia. A previous study demonstrated that elevated values of dead-space fraction (Vd/Vt) are associated with increased risk of death in patients with ARDS [2].Siddiki and colleagues [3] examined the utility of bedside calculation of pulmonary Vd/Vt in predicting the prognosis of patients with ALI/ARDS. The goal of the authors was to calculate Vd/Vt by using variables, such as minute ventilation (VE) and the arterial tension of carbon dioxide (PaCO2), that are readily available at the bedside. The authors used the rearranged alveolar gas equation: Vd/Vt = 1 - [(0.86 × VCO2est)/VE × PaCO2], where VCO2est represents the estimated carbon dioxide production derived from the modified Harris-Benedict equation. Data from two large databases of approximately 2,000 patients in total were used to calculate the Vd/Vt on days 1 and 3 of admission. A contingency analysis showed that higher Vd/Vt values were associated with higher mortality. For example, Vd/Vt values of less than 0.4 and greater than 0.8 were associated with hospital mortality rates of about 20% and 50%, respectively. This relationship was valid after adjustment for Acute Physiology and Chronic Health Evaluation III (APACHE III) score, presence of shock, hypoxemia, and positive end-expiratory pressure (PEEP).De Robertis and colleagues [4] employed two techniques t
Year in review 2010: Critical Care - cardiac arrest and cardiopulmonary resuscitation
Jeffery C Metzger, Alexander L Eastman, Paul E Pepe
Critical Care , 2011, DOI: 10.1186/cc10540
Abstract: In 2010, a number of papers were published in the field of cardiac arrest and cardiopulmonary resuscitation (CPR). Critical Care provided us with some innovative and important data within these fields of research. This review will summarize some of the notable data published in 2010 and focus on papers published in Critical Care. For example, we discuss the latest research in therapeutic hypothermia after cardiac arrest and also review the effects of bystander-initiated cardiopulmonary resuscitation (BCPR), the role of hypercapnea in near-death experiences (NDEs) during cardiac arrest, markers of endothelial injury after CPR, and the use of cell-free plasma DNA as a marker to predict outcome after CPR.While the idea of therapeutic hypothermia is not new by any means (dating back to its recommended use by Hippocrates for wounded patients [1]), therapeutic hypothermia has been shown for almost a decade to decrease mortality and improve outcomes after cardiac arrest [2,3]. In 2010, we continued to learn about this life-saving therapeutic modality.Several studies looked at the mechanisms of cooling patients. One study looked at the use of an external shower of water (2°C) which achieved a median rate of cooling of 3°C per hour [4]. Another study showed that the Arctic Sun device (Medivance, Inc., Louisville, CO, USA) cooled, on average, 54 minutes faster than other external measures such as ice packets and blankets [5], whereas yet another study [6] compared endovascular cooling with external cooling and showed that endovascular cooling led to more time in the target temperature range, less temperature fluctuation, and more control during rewarming. It is currently recommended that cooling be achieved as soon as possible [6]. In a study in Critical Care, ?kulec and colleagues [7] looked at the effectiveness of infusing 15 to 20 mL/kg of 4°C saline intravenously in the pre-hospital environment and found an average decrease in the tympanic temperature of 1.4°C over the co
Year in review 2010: Critical Care - multiple organ dysfunction and sepsis
Etienne de Montmollin, Djillali Annane
Critical Care , 2011, DOI: 10.1186/cc10359
Abstract: Multiple organ failure, or multiple organ dysfunction syndrome (MODS), was defined by the 1991 Consensus Conference of the American College of Chest Physicians and the Society of Critical Care Medicine as 'the presence of altered organ functions in an acutely ill patient such that homeostasis cannot be maintained without intervention' [1]. Septic shock is the main cause of MODS in intensive care units, and the intensity of MODS is correlated directly to mortality [2]. Furthermore, MODS is the main cause of death in patients with severe sepsis, representing 43.1% of patients in a recent retrospective study [3]. Our aim was to review the relevant findings of research articles that were published in 2010 in Critical Care and that focused on advances in the understanding of MODS physiopathology, diagnostic and prognostic marker evaluation, and novel therapy strategies.It is now well established that the correction of macrovascular hemodynamic parameters is not sufficient to prevent MODS in sepsis and that persistent microvascular alteration is associated with the development of organ dysfunction and death [4]. The endothelium plays a central role in microvascular dysfunction and sepsis physiopathology, regulating vasomotor tone, cellular trafficking, coagulation, and local balance between proand anti-inflammatory mediators [5].In a prospective single-center study of 221 patients admitted with a clinical suspicion of infection to an emergency department, Shapiro and colleagues [6] investigated the association between endothelial cell signaling activation during sepsis at the time of emergency department consultation and the subsequent severity of organ dysfunction. They demonstrated that circulating levels of biomarkers of endothelial activation such as soluble fms-like tyrosine kinase-1 (sFlt-1), plasminogen activator inhibitor-1 (PAI-1), soluble E-selectin, soluble intercellular adhesion molecule-1 (sICAM-1), and soluble vascular cell adhesion molecule-1 (sVCAM-1) were
Year in review 2007: Critical Care – cardiology
Luigi Camporota, Marius Terblanche, David Bennett
Critical Care , 2008, DOI: 10.1186/cc7007
Abstract: Mixed venous oxygen saturation (SvO2) and central venous oxygen saturation (ScvO2) – measured from the superior vena cava (SVC) – are used as indicators of adequacy of oxygen supply to the tissues. However, obtaining SvO2 requires the insertion of a pulmonary artery catheter (PAC), which is invasive and is associated with an increased risk of complications [1]. ScvO2 has been used as a surrogate for SvO2, and targeting ScvO2 in the treatment of patients with severe sepsis is associated with a significant survival benefit [2]. For this reason, the measurement of ScvO2 is now part of the 6-hour sepsis bundle and is recommended by the Surviving Sepsis Campaign guidelines [3]. However, some questions remain: Is ScvO2 an accurate reflection of SvO2? How well do they correlate? What is the mechanism accounting for the observed differences between the two parameters [4-8]?Generally, ScvO2 is approximately 3% to 5% higher than SvO2 as oxygen saturation (SO2) decreases as blood travels from the SVC to the pulmonary artery (PA). The gradient varies considerably among individuals, depending on the particular disease state and on the value of SvO2 [9]. The gradient in SO2 and lactate [Lac] between SVC and PA (ΔSO2 and Δ[Lac], respectively) may develop as blood from the SVC mixes with blood draining from the inferior vena cava (IVC) and/or from the heart's venous system [6].To test this hypothesis, Gutierrez and colleagues [10] conducted a prospective observational study in nine haemodynamically stable adults without intracardiac defects or significant valvular disease who underwent right heart catheterisation for mild-to-moderate pulmonary hypertension. The authors found a significant mean ΔSO2 of 4.4% and a Δ[Lac] of 0.16 mmol/L. The lower values in SO2 and [Lac] measured in the PA could not be explained by the mixing of blood from the IVC with blood from the SVC, as hypothesised, since SO2 and [Lac] were similar in the IVC and SVC. The fact that the greatest decrease in SO2 a
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