Echocardiography: a help in the weaning process

Atrial Fibrillation on Intensive Care Unit Admission Independently Increases the Risk of Weaning Failure in Nonheart Failure Mechanically Ventilated Patients in a Medical Intensive Care Unit: A Retrospective Case-Control Study

Atrial fibrillation (AF) is one of the most frequent arrhythmias in clinical practice. Previous studies have reported the influence of AF on patients with heart failure (HF). The effect of AF on the non-HF critically ill patients in a medical intensive care unit (ICU) remains largely unclear. The study aimed to investigate the impact of AF presenting on ICU admission on the weaning outcome of non-HF mechanically ventilated patients in a medical ICU.A retrospective observational case-control study was conducted over a 1-year period in a medical ICU at Taipei Veterans General Hospital, a tertiary medical center in north Taiwan. Non-HF mechanically ventilated patients who were successful in their spontaneous breathing trial and underwent ventilator discontinuation were enrolled. The primary outcome measure was the ventilator status after the first episode of ventilator discontinuation.A total of 285 non-HF patients enrolled were divided into AF (n = 62) and non-AF (n = 223) groups. Compared with the non-AF patients, the AF patients were significantly associated with old age (P = 0.002), a higher rate of acute respiratory distress syndrome causing respiratory failure (P = 0.015), a higher percentage of sepsis before liberation from mechanical ventilation (MV) (P = 0.004), and a higher serum level of blood urea nitrogen on the day of liberation from MV (P = 0.003). Multivariate logistic regression analysis demonstrated that AF independently increased the risk of weaning failure [adjusted odds ratio (AOR), 3.268; 95% confidence interval (CI), 1.254-8.517; P = 0.015]. Furthermore, the AF patients were found to be independently associated with a high rate of ventilator dependence (log rank test, P = 0.026), prolonged total ventilator use (AOR, 1.979; 95% CI, 1.032-3.794; P = 0.040), increased length of ICU stay (AOR, 2.256; 95% CI, 1.049-4.849; P = 0.037), increased length of hospital stay (AOR, 2.921; 95% CI, 1.363-6.260; P = 0.006), and increased ICU mortality (AOR, 4.143; 95% CI, 1.381-12.424; P = 0.011).AF on ICU admission is an independent risk factor for weaning failure and significantly associated with poor hospital outcome in non-HF mechanically ventilated patients in a medical ICU.

Interpreting diaphragmatic movement with bedside imaging, review article

The diaphragm is the most important muscle of respiration. At equilibrium, the load imposed on the diaphragmatic muscles from transdiaphragmatic pressure balances the force generated by diaphragmatic muscles. However, procedural and nonprocedural thoracic and abdominal conditions may disrupt this equilibrium and impair diaphragmatic function. Diaphragmatic dysfunction is associated with respiratory insufficiency and poor outcome. Therefore, rapid diagnosis and early intervention may be useful. Ultrasound imaging provides quick and accurate bedside assessment of the diaphragm. Various imaging techniques have been suggested, using 2-dimensional and M-mode technology. Diaphragm viewing depends on the degree of robe movement, determined by the angle of incidence of the ultrasound beam and by the direction of probe movement. In this review, we will discuss the function of the diaphragm focusing on clinically important anatomical and physiological properties of the diaphragm. We will review the literature regarding various sonographic techniques for diaphragm assessment. We will also explore the evidence for the role of the tidal displacement of subdiaphragmatic organs as a surrogate for diaphragm movement.

Ultrasonography evaluation during the weaning process: the heart, the diaphragm, the pleura and the lung

PURPOSE

On a regular basis, the intensivist encounters the patient who is difficult to wean from mechanical ventilatory support. The causes for failure to wean from mechanical ventilatory support are often multifactorial and involve a complex interplay between cardiac and pulmonary dysfunction. A potential application of point of care ultrasonography relates to its utility in the process of weaning the patient from mechanical ventilatory support.

METHODS

This article reviews some applications of ultrasonography that may be relevant to the process of weaning from mechanical ventilatory support.

RESULTS

The authors have divided these applications of ultrasonography into four separate categories: the assessment of cardiac, diaphragmatic, and lung function; and the identification of pleural effusion; which can all be evaluated with ultrasonography during a dynamic process in which the intensivist is uniquely positioned to use ultrasonography at the point of care.

CONCLUSIONS

Ultrasonography may have useful application during the weaning process from mechanical ventilatory support.

Ultrasonic evaluation of the heart

PURPOSE OF REVIEW

To discuss the role of echocardiography for the hemodynamic evaluation of critically ill patients.

RECENT FINDINGS

In addition to its crucial role in evaluating heart abnormalities as in the classical cardiological approach, echocardiography is now frequently used by intensivists for noninvasive hemodynamic evaluation of the critically ill patient. Using echocardiography, it is possible to measure cardiac output, intravascular pressures and volumes, systolic and diastolic function of both ventricles, and preload responsiveness. This not only allows characterization of the precise nature of hemodynamic alterations in patients with circulatory and respiratory failure, but also provides guidance for hemodynamic optimization and optimization of ventilatory settings. There are now many data showing how echocardiography can be useful in detecting otherwise unrecognized myocardial depression in sepsis and right ventricular dysfunction in mechanically ventilated patients. The main limitation of echocardiography for hemodynamic monitoring is its intermittent nature. Hence, echocardiography is often combined with other monitoring devices, allowing continuous measurement of flow and triggering new echocardiographic evaluations.

SUMMARY

Echocardiography has now become an important tool for hemodynamic evaluation of the critically ill patient. Echocardiography should be performed in most patients with circulatory and respiratory failure.

Passive leg raising performed before a spontaneous breathing trial predicts weaning-induced cardiac dysfunction

PURPOSE

Weaning-induced cardiac dysfunction is more likely to occur if the heart does not tolerate the changes in loading conditions induced by spontaneous breathing trial (SBT). We hypothesized that the presence of cardiac preload independence before an SBT is associated with weaning failure related to cardiac dysfunction.

METHODS

We included 30 patients after a first failed 1-h T-tube SBT who had a transpulmonary thermodilution already in place. Preload independence [no increase in the pulse contour analysis-derived cardiac index ≥10 % during passive leg raising (PLR)] was assessed before the second SBT. Failure of the SBT related to cardiac dysfunction was defined by an increase in pulmonary artery occlusion pressure above 18 mmHg at the end of the SBT associated with clinical intolerance.

RESULTS

Fifty-seven SBTs were analyzed. The SBT failed in 46 cases. Overall, 31 failed SBTs were associated with weaning-induced cardiac dysfunction. During PLR, the cardiac index did not change in cases of failed SBTs with cardiac dysfunction, whereas it significantly increased in the other cases: 4 % (interquartile range, IQR 0-5) vs. 12 % (IQR 11-15), respectively. If PLR did not increase the cardiac index by more than 10 % before the SBT, the occurrence of SBT failure related to cardiac dysfunction was predicted with a sensitivity of 97 % [95 % confidence interval (CI) 83-100], specificity of 81 % (95 % CI 61-93) and area under the receiver-operating characteristic curve of 0.88 (95 % CI 0.78-0.98).

CONCLUSIONS

Preload independence assessed by a negative PLR test performed before an SBT predicts weaning failure related to cardiac dysfunction.

Pressure support-ventilation versus spontaneous breathing with "T-Tube" for interrupting the ventilation after cardiac operations

Objective

To compare pressure-support ventilation with spontaneous breathing through a T-tube for interrupting invasive mechanical ventilation in patients undergoing cardiac surgery with cardiopulmonary bypass.

Methods

Adults of both genders were randomly allocated to 30 minutes of either pressure-support ventilation or spontaneous ventilation with "T-tube" before extubation. Manovacuometry, ventilometry and clinical evaluation were performed before the operation, immediately before and after extubation, 1h and 12h after extubation.

Results

Twenty-eight patients were studied. There were no deaths or pulmonary complications. The mean aortic clamping time in the pressure support ventilation group was 62 ± 35 minutes and 68 ± 36 minutes in the T-tube group (P=0.651). The mean cardiopulmonary bypass duration in the pressure-support ventilation group was 89 ± 44 minutes and 82 ± 42 minutes in the T-tube group (P=0.75). The mean Tobin index in the pressure support ventilation group was 51 ± 25 and 64.5 ± 23 in the T-tube group (P=0.153). The duration of intensive care unit stay for the pressure support ventilation group was 2.1 ± 0.36 days and 2.3 ± 0.61 days in the T-tube group (P=0.581). The atelectasis score in the T-tube group was 0.6 ± 0.8 and 0.5 ± 0.6 (P=0.979) in the pressure support ventilation group. The study groups did not differ significantly in manovacuometric and ventilometric parameters and hospital evolution.

Conclusion

The two trial methods evaluated for interruption of mechanical ventilation did not affect the postoperative course of patients who underwent cardiac operations with cardiopulmonary bypass.

Weaning-induced cardiac dysfunction: where are we today?

INTRODUCTION

The concept of weaning-induced cardiac dysfunction emerged 26 years ago with the publication of a clinical study conducted by François Lemaire and collaborators.

OBJECTIVES

One objective of this article is to remember the results and the historical context under which our pivotal study was conducted. Another objective is to review some of the subsequent studies that aimed to analyze the underlying mechanisms, to noninvasively detect the cardiac origin of weaning failure, and to propose specific therapies enabling weaning success.

CONCLUSION

Weaning-induced cardiac dysfunction has become an established cause of weaning failure. Underlying mechanisms may differ from one patient to another. Important progress has already been made in its diagnosis thanks to relevant clinical research studies. Ongoing and future technological advances in ultrasonography and in biomarker research should certainly help in diagnosing weaning induced-pulmonary edema and in identifying the main mechanisms responsible for its development. Progress on appropriate therapeutic options on an individual basis is still expected.

Difficult-to-wean: High index of suspicion

PATIENT

Female, 57 FINAL DIAGNOSIS: Syryngomyelia • cervical

SYMPTOMS

Acute respiratory insufficiency Medication: - Clinical Procedure: - Specialty: Pulmonology.

OBJECTIVE

Rare disease.

BACKGROUND

Failed planned extubation occurs in a minority of patients with acute respiratory failure requiring invasive mechanical ventilation. In patients presenting with acute respiratory failure with no identifiable cardiopulmonary causes, uncommon conditions, such as cervical spondylotic myelopathy, should be considered. In very rare instances, when cervical spondylotic myelopathy and syringomyelia present concomitantly, they can be devastating.

CASE REPORT

A 57-year-old woman visited the emergency room (ER) after feeling unwell for several days. She was brought to the ER with acute respiratory distress and obtunded state with GCS of 6/15. She was hypotensive and agonally breathing. Her initial neurologic evaluation was unrevealing. Based on these findings, she was intubated. Over the next several days, she was difficult to wean from the ventilator and had persistent respiratory acidosis. After a short-lived extubation, the patient was again re-intubated. This time the neurologic evaluation showed decreased movements of all muscle groups against gravity and forces, with generalized weakness. An MRI of the brain and cervical spine demonstrated moderate degenerative disc disease and syringomyelia extending from C2 to C7 level. The patient underwent de-compression laminectomy. After failing several weaning trials, she underwent bronchoscopically-assisted tracheotomy.

CONCLUSIONS

Acute cardiopulmonary and intensive care unit-acquired neuromuscular conditions have been attributed as a major cause of difficult weaning and extubation. Failure to identify and correct other rare combinations (such as cervical degenerative disc disease and syringomyelia) may cause acute respiratory failure and subsequent failure to wean and extubation, resulting in high rates of mortality and morbidity.

Lung Ultrasound Predicts Interstitial Syndrome and Hemodynamic Profile in Parturients with Severe Preeclampsia

Background:

The role of lung ultrasound has never been evaluated in parturients with severe preeclampsia. The authors’ first aim was to assess the ability of lung ultrasound to detect pulmonary edema in severe preeclampsia. The second aim was to highlight the relation between B-lines and increased left ventricular end-diastolic pressures.

Methods:

This prospective cohort study was conducted in a level-3 maternity during a 12-month period. Twenty parturients with severe preeclampsia were consecutively enrolled. Both lung and cardiac ultrasound examinations were performed before (n = 20) and after delivery (n = 20). Each parturient with severe preeclampsia was compared with a control healthy parturient. Pulmonary edema was determined using two scores: the B-pattern and the Echo Comet Score. Left ventricular end-diastolic pressures were assessed by transthoracic echocardiography.

Results:

Lung ultrasound detected interstitial edema in five parturients (25%) with severe preeclampsia. A B-pattern was associated to increased mitral valve early diastolic peak E (116 vs. 90 cm/s; P = 0.05) and to increased E/E’ ratio (9.9 vs. 6.6; P < 0.001). An Echo Comet Score of greater than 25 predicted an increase in filling pressures (E/E’ ratio >9.5) with a sensitivity and specificity of 1.00 (95% CI, 0.69 to 1.00) and 0.82 (95% CI, 0.66 to 0.92), respectively.

Conclusions:

In parturients with severe preeclampsia, lung ultrasound detects both pulmonary edema and increased left ventricular end-diastolic pressures. The finding of a B-pattern should restrict the use of fluid. However, these preliminary results are associations from a single sample. They need to be replicated in a larger, definitive study.

Weaning failure: my heart is not up to it

Weaning patients from mechanical ventilation has been compared to a cardiac stress test. Weaning failure (WF) from a cardiac origin can be common in patients with limited cardiac reserve. Diuretic and vasodilator therapies are indicated for WF due to excessive preload, afterload, or myocardial ischemia. Alteration in intrathoracic pressure and lung volumes may also impact weaning process in a patient with poor cardiac function. Noninvasive ventilation decreases cardiac stress load and should be utilized in weaning patients with poor cardiac reserves. In fact, positive pressure therapy is now the standard of care for treating a patient with acute pulmonary edema and to decrease afterload (Frazier et al. Biol Res Nurs 2000; 1(4): 253-264; Pinsky MR. Chest 2005; 128(5 Suppl 2): 592S-597S.). Recently, biomarkers and echocardiography have been utilized to assess weaning success during spontaneous breathing trials. In this article, we describe the physiological alterations in cardiac and pulmonary systems during the weaning process and its impact on weaning outcome.

Doppler echocardiography in shocked patients

PURPOSE OF REVIEW

To reiterate the necessity of integrating echocardiography in the management of shocked patients and to propose a step-by-step functional evaluation of hemodynamics proven to optimize hemodynamic monitoring and to adapt the treatment.

RECENT FINDINGS

Echocardiography has become the cornerstone to hemodynamic monitoring. By providing real-time images, echocardiography has the advantage over 'blind' technologies of an excellent diagnostic performance and of quick provision of information about the pathophysiology of circulatory failure. Critical care echocardiography (CCE) has been defined as echocardiography performed and interpreted by intensivists themselves, 7/7 and 24/24, at the bedside. Basic CCE is mainly a diagnostic approach, allowing quick and focused examination of cardiac function. Advanced CCE is the core of functional hemodynamic monitoring. It is based not only on transthoracic echocardiography but also strongly on transesophageal echocardiography, a very useful approach in ventilated patients. However, this monitoring is discontinuous. A single-use 72-h indwelling transesophageal probe was recently tested, allowing functional hemodynamic monitoring more continuously.

SUMMARY

Echocardiography has become a hemodynamic monitoring technique used worldwide. It allows to make a quick and simple diagnosis of typical hemodynamic situations, by means of basic CCE, and also to achieve real functional hemodynamic monitoring, through advanced CCE.

Ventricular diastolic abnormalities in the critically ill

PURPOSE OF REVIEW

Left-ventricular diastolic dysfunction is associated with various conditions frequently encountered in ICU patients. Due to prolonged relaxation and increased left-ventricular stiffness, patients with diastolic dysfunction are at high risk of developing abrupt pulmonary venous congestion. The present review describes the clinical spectrum of left-ventricular diastolic abnormalities in ICU patients.

RECENT FINDINGS

Left-ventricular diastolic dysfunction is associated with a preserved ejection fraction in half of the patients presenting with acute pulmonary edema. These patients may have dramatic presentation, such as flash pulmonary edema during a hypertensive crisis. Left-ventricular diastolic dysfunction is frequently involved in patients who fail extubation and may trigger weaning pulmonary edema. Sepsis and myocardial ischemia may also be associated with left-ventricular diastolic dysfunction. The diagnosis of left-ventricular diastolic dysfunction practically relies on two-dimensional and Doppler echocardiography. Further large-scale clinical studies are needed to better characterize the prevalence, the clinical relevance and time-course of left-ventricular diastolic dysfunction in ICU patients.

SUMMARY

Left-ventricular diastolic dysfunction accounts for a growing proportion of cardiogenic pulmonary edema and weaning failure in ICU patients. It may be reversible when induced by sepsis or myocardial ischemia. Its prognostic value in the ICU settings remains to be further investigated.

Focused critical care echocardiography

OBJECTIVE

Portable ultrasound is now used routinely in many ICUs for various clinical applications. Echocardiography performed by noncardiologists, both transesophageal and transthoracic, has evolved to broad applications in diagnosis, monitoring, and management of critically ill patients. This review provides a current update on focused critical care echocardiography for the management of critically ill patients.

METHOD

Source data were obtained from a PubMed search of the medical literature, including the PubMed "related articles" search methodology.

SUMMARY AND CONCLUSIONS

Although studies demonstrating improved clinical outcomes for critically ill patients managed by focused critical care echocardiography are generally lacking, there is evidence to suggest that some intermediate outcomes are improved. Furthermore, noncardiologists can learn focused critical care echocardiography and adequately interpret the information obtained. Noncardiologists can also successfully incorporate focused critical care echocardiography into advanced cardiopulmonary life support. Formal training and proctoring are important for safe application of focused critical care echocardiography in clinical practice. Further outcomes-based research is urgently needed to evaluate the efficacy of focused critical care echocardiography.

Year in review 2012: Critical Care--Cardiology

In this review I discuss key research papers in cardiology and intensive care published in Critical Care during 2012 with related studies published in other journals quoted whenever appropriate. These studies are grouped into the following categories: cardiovascular therapies, mechanical therapies, pathophysiologic mechanisms, hemodynamic monitoring, ultrasound in respiratory failure, microcirculation, and miscellaneous.

Usefulness of combined bedside lung ultrasound and echocardiography to assess weaning failure from mechanical ventilation: a suggestive case*

OBJECTIVE

Recognition of the cardiac origin of weaning failure is a crucial issue for successful discontinuation of mechanical ventilation. Bedside lung ultrasound and echocardiography have shown a potential in predicting weaning failure. Objective of this report was to describe the case of a patient repeatedly failing to wean from mechanical ventilation, where the combined use of lung ultrasound and echocardiography during a spontaneous breathing trial uncovered an unexpected cause of the failure.

DESIGN

Case report.

SETTING

General ICU of a university teaching hospital.

PATIENTS

Single case, abdominal surgery postoperative patient, not predicted to experience a difficult weaning.

INTERVENTIONS

Cardiovascular therapy adjustments consistent with lung ultrasound and echocardiography findings acquired during spontaneous breathing trials.

MEASUREMENTS AND MAIN RESULTS

All patient's standard hemodynamic and respiratory parameters, datasets from comprehensive lung ultrasound and echocardiographic examinations, and pertinent data from biochemistry exams, were collected during two spontaneous breathing trials. Data from beginning and end of each of the two ultrasound monitored weaning trials, and from the end of the successful weaning trial following therapy and the previously failed one, were analyzed and qualitatively compared. Lung ultrasound performed at the end of the failed spontaneous breathing trial showed a pattern consistent with increased extravascular lung water (diffuse, bilateral, symmetrical, homogeneous sonographic interstitial syndrome). Concurrent echocardiography diagnosed left ventricular diastolic failure. Ultrasound findings at the end of the successful weaning trial showed normalization of the lung pattern and improvement of the echocardiographic one. The patient eventually returned to spontaneous respiration and was discharged from the ICU.

CONCLUSIONS

The use of bedside lung ultrasound and echocardiography disclosed left ventricular diastolic dysfunction as unexpected cardiogenic cause of weaning failure and lead to subsequent correct patient management.

The decision to extubate in the intensive care unit

The day of extubation is a critical time during an intensive care unit (ICU) stay. Extubation is usually decided after a weaning readiness test involving spontaneous breathing on a T-piece or low levels of ventilatory assist. Extubation failure occurs in 10 to 20% of patients and is associated with extremely poor outcomes, including high mortality rates of 25 to 50%. There is some evidence that extubation failure can directly worsen patient outcomes independently of underlying illness severity. Understanding the pathophysiology of weaning tests is essential given their central role in extubation decisions, yet few studies have investigated this point. Because extubation failure is relatively uncommon, randomized controlled trials on weaning are underpowered to address this issue. Moreover, most studies evaluated patients at low risk for extubation failure, whose reintubation rates were about 10 to 15%, whereas several studies identified high-risk patients with extubation failure rates exceeding 25 or 30%. Strategies for identifying patients at high risk for extubation failure are essential to improve the management of weaning and extubation. Two preventive measures may prove beneficial, although their exact role needs confirmation: one is noninvasive ventilation after extubation in high-risk or hypercapnic patients, and the other is steroid administration several hours before extubation. These measures might help to prevent postextubation respiratory distress in selected patient subgroups.

Weaning from the ventilator and extubation in ICU

PURPOSE OF REVIEW

The decision to extubate is a crucial moment for intubated patients. In most cases, the transition to spontaneous breathing is uneventful, but in some patients, it implies a more challenging decision. Both extubation delay and especially the need for reintubation are associated with poor outcomes. We aim to review the recent literature on weaning and to clarify the role of certain interventions intending to help in this process.

RECENT FINDINGS

Cardiac dysfunction is probably one of the most common causes of weaning failure. Several studies have evaluated the ability of B-natriuretic peptides and echocardiographic tools to predict weaning outcome due to cardiac origin, attempting to prevent its failure. Noninvasive ventilation may have a potential benefit in preventing respiratory failure after extubation of hypercapnic patients, although more studies are needed to define a target population.

SUMMARY

Current research is focusing on preventing extubation failure, especially in the most challenging cases. The use of weaning protocols - written or computerized - attempts to early identify patients who are able to breathe spontaneously and to hasten extubation, resulting in better outcomes. Nevertheless, individualized care is needed in the most vulnerable patients, trying to prompt weaning without exposing patients to unnecessary risks.

Sepsis-induced cardiomyopathy

Myocardial dysfunction is one of the main predictors of poor outcome in septic patients, with mortality rates next to 70%. During the sepsis-induced myocardial dysfunction, both ventricles can dilate and diminish its ejection fraction, having less response to fluid resuscitation and catecholamines, but typically is assumed to be reversible within 7-10 days. In the last 30 years, It´s being subject of substantial research; however no explanation of its etiopathogenesis or effective treatment have been proved yet. The aim of this manuscript is to review on the most relevant aspects of the sepsis-induced myocardial dysfunction, discuss its clinical presentation, pathophysiology, etiopathogenesis, diagnostic tools and therapeutic strategies proposed in recent years.

Review article: Clinical impact of non-cardiologist-performed transthoracic echocardiography in emergency medicine, intensive care medicine and anaesthesia

There is increased realisation of the emerging role of point-of-care transthoracic echocardiography (TTE) as 'ultrasound-assisted examination', given the low sensitivity of clinical examination for cardiovascular pathologies and the time-critical nature of these pathologies. There is evidence that point-of-care TTE provides higher accuracy in patient assessment and management, with potential prognostic impact by assessing the severity of cardiac dysfunction and response to treatment. Point-of-care TTE is increasingly used by non-cardiologists, as a diagnostic, screening or monitoring tool. The literature shows that TTE identifies new clinical findings, and conversely can accurately rule out clinically important pathologies. Recent reports have examined more advanced ultrasound devices and patients in the critical care settings of emergency medicine, intensive care and anaesthesia. The diagnostic capability of new portable devices is improving rapidly and outdating its predecessors, thereby improving confidence in echocardiography findings.

Clinical review: Respiratory monitoring in the ICU - a consensus of 16

Monitoring plays an important role in the current management of patients with acute respiratory failure but sometimes lacks definition regarding which 'signals' and 'derived variables' should be prioritized as well as specifics related to timing (continuous versus intermittent) and modality (static versus dynamic). Many new techniques of respiratory monitoring have been made available for clinical use recently, but their place is not always well defined. Appropriate use of available monitoring techniques and correct interpretation of the data provided can help improve our understanding of the disease processes involved and the effects of clinical interventions. In this consensus paper, we provide an overview of the important parameters that can and should be monitored in the critically ill patient with respiratory failure and discuss how the data provided can impact on clinical management.

Natriuretic peptide-driven fluid management during ventilator weaning: a randomized controlled trial

RATIONALE

Difficult weaning from mechanical ventilation is often associated with fluid overload. B-type natriuretic peptide (BNP) has been proposed as a tool for predicting and detecting weaning failure of cardiovascular origin.

OBJECTIVES

To investigate whether fluid management guided by daily BNP plasma concentrations improves weaning outcomes compared with empirical therapy dictated by clinical acumen.

METHODS

In a randomized controlled multicenter study, we allocated 304 patients to either a BNP-driven or physician-driven strategy of fluid management during ventilator weaning. To standardize the weaning process, patients in both groups were ventilated with an automatic computer-driven weaning system. The primary end point was time to successful extubation.

MEASUREMENTS AND MAIN RESULTS

In the BNP-driven group, furosemide and acetazolamide were given more often and in higher doses than in the control group, resulting in a more negative median (interquartile range) fluid balance during weaning (-2,320 [-4,735, 738] vs. -180 [-2,556, 2,832] ml; P < 0.0001). Time to successful extubation was significantly shorter with the BNP-driven strategy (58.6 [23.3, 139.8] vs. 42.4 [20.8, 107.5] h; P = 0.034). The BNP-driven strategy increased the number of ventilator-free days but did not change length of stay or mortality. The effect on weaning time was strongest in patients with left ventricular systolic dysfunction. The two strategies did not differ significantly regarding electrolyte imbalance, renal failure, or shock.

CONCLUSIONS

Our results suggest that a BNP-driven fluid management strategy decreases the duration of weaning without increasing adverse events, especially in patients with left ventricular systolic dysfunction. Clinical trial registered with www.clinicaltrials.gov (NCT00473148).

Failed weaning from mechanical ventilation and cardiac dysfunction

Failure to transition patient from controlled mechanical ventilation to spontaneous breathing trials (SBTs) in a timely fashion is associated with significant morbidity and mortality in the intensive care unit. In addition, weaning failures are common in patients with limited cardiac reserves. Recent advances in cardiac echocardiography and laboratory measurement of serum biomarkers to assess hemodynamic response to SBT may provide additional information to guide clinicians to predict weaning outcome.

Early and simple detection of diastolic dysfunction during weaning from mechanical ventilation

Weaning from mechanical ventilation imposes additional work on the cardiovascular system and can provoke or unmask left ventricular diastolic dysfunction with consecutive pulmonary edema or systolic dysfunction with inadequate increase of cardiac output and unsuccessful weaning. Echocardiography, which is increasingly used for hemodynamic assessment of critically ill patients, allows differentiation between systolic and diastolic failure. For various reasons, transthoracic echocardiographic assessment was limited to patients with good echo visibility and to those with sinus rhythm without excessive tachycardia. In these patients, often selected after unsuccessful weaning, echocardiographic findings were predictive for weaning failure of cardiac origin. In some studies, patients with various degrees of systolic dysfunction were included, making evaluation of the diastolic dysfunction to the weaning failure even more difficult. The recent study by Moschietto and coworkers included unselected patients and used very simple diastolic variables for assessment of diastolic function. They also included patients with atrial fibrillation and repeated echocardiographic examination only 10 minutes after starting a spontaneous breathing trial. The main finding was that weaning failure was not associated with systolic dysfunction but with diastolic dysfunction. By measuring simple and robust parameters for detection of diastolic dysfunction, the study was able to predict weaning failure in patients with sinus rhythm and atrial fibrillation as early as 10 minutes after beginning a spontaneous breathing trial. Further studies are necessary to determine whether appropriate treatment tailored according to the echocardiographic findings will result in successful weaning.

Left ventricular diastolic dysfunction in the intensive care unit: trends and perspectives

Heart failure with a normal or nearly normal left ventricular (LV) ejection fraction (HFNEF) may represent more than 50% of heart failure cases. Although HFNEF is being increasingly recognized, there is a relative lack of information regarding its incidence and prognostic implications in intensive care unit (ICU) patients. In the ICU, many factors related to patient's history, or applied therapies, may induce or aggravate LV diastolic dysfunction. This may impact on patients' morbidity and mortality. This paper discusses methods for assessing LV diastolic function and the feasibility of their implementation for diagnosing HFNEF in the ICU.

Transthoracic Echocardiography with Doppler Tissue Imaging predicts weaning failure from mechanical ventilation: evolution of the left ventricle relaxation rate during a spontaneous breathing trial is the key factor in weaning outcome

Introduction

There is growing evidence to suggest that transthoracic echocardiography (TTE) should be used to identify the cardiac origin of respiratory weaning failure. The aims of our study were: first, to evaluate the ability of transthoracic echocardiography, with mitral Doppler inflow E velocity to annular tissue Doppler Ea wave velocity (E/Ea) ratio measurement, to predict weaning failure from mechanical ventilation in patients, including those with atrial fibrillation; and second, to determine whether the depressed left ejection fraction and/or diastolic dysfunction participate in weaning outcome.

Methods

The sample included patients on mechanical ventilation for over 48 hours. A complete echocardiography was performed just before the spontaneous breathing trial (SBT) and 10 minutes after starting the SBT. Systolic dysfunction was defined by a left ventricle ejection fraction under 50% and relaxation impairment by a protodiastolic annulus mitral velocity Ea under or equal to 8 cm/second.

Results

A total of 68 patients were included. Twenty failed the weaning process and the other 48 patients succeeded. Before the SBT, the E/Ea ratio was higher in the failed group than in the successful group. The E/Ea measured during the SBT was also higher in the failed group. The cut-off value, obtained from receiver operating characteristics (ROC) curve analysis, to predict weaning failure gave an E/Ea ratio during the SBT of 14.5 with a sensitivity of 75% and a specificity of 95.8%. The left ventricular ejection fraction did not differ between the two groups whereas Ea was lower in the failed group. Ea increased during SBT in the successful group while no change occurred in the failed group.

Conclusions

Measurement of the E/Ea ratio with TTE could predict weaning failure. Diastolic dysfunction with relaxation impairment is strongly associated with weaning failure. Moreover, the impossibility of enhancing the left ventricle relaxation rate during the SBT seems to be the key factor of weaning failure. In contrast, the systolic dysfunction was not associated with weaning outcome.

Year in review 2010: Critical Care--Cardiology

We review key research papers in cardiology and intensive care published during 2010 in Critical Care and quote related studies published in other journals if appropriate. Papers were grouped into the following categories: cardiovascular therapies, biomarkers, hemodynamic monitoring, cardiovascular diseases, and microcirculation.

New insights into weaning from mechanical ventilation: left ventricular diastolic dysfunction is a key player

PURPOSE

To investigate the diagnostic performance of Doppler echocardiography (DE) in predicting the outcome of weaning from mechanical ventilation in patients without overt cardiac disease.

METHODS

Fifty critical care noncardiac patients who fulfilled predetermined criteria for weaning underwent DE before and at the end of spontaneous breathing trial (pre-SBT/end-SBT, respectively). "Conventional" mitral inflow analysis and "advanced" DE parameters [tissue Doppler imaging (TDI)-derived mitral/tricuspid annular velocities and color M-mode Doppler velocity of propagation (V p)] were used to assess left ventricular (LV) diastolic function/filling pressures. Weaning was considered successful if patients had been extubated after successful SBT and sustained spontaneous breathing for more than 48 h.

RESULTS

Twenty-eight patients (56%) failed weaning: 23 patients failed SBT and 5 required reintubation within 48 h. Weaning failure was associated with the degree of LV diastolic dysfunction at pre-SBT (P = 0.01). Patients who failed weaning presented evidence of increased LV filling pressures at pre-SBT, by demonstrating increased E/E m and E/V p ratios compared with patients with successful outcome (P ≤ 0.004); pre-SBT values of lateral E/E m greater than 7.8 and E/V p greater than 1.51 predicted weaning failure with an area under the curve, sensitivity (%), and specificity (%) of 0.86, 79, and 100, and 0.74, 75, and 73, respectively. Lateral E/E m was the only factor independently associated with weaning failure before SBT; OR (95% CI) 5.62 (1.17-26.96), P = 0.03.

CONCLUSIONS

Our findings suggest that LV diastolic dysfunction is significantly associated with weaning outcome in critically ill patients with preserved LV systolic function. An E/E m ratio greater than 7.8 may identify patients at high risk of weaning failure.

Echocardiographic hemodynamic monitoring in the critically ill patient

Echocardiography has shown to be an essential diagnostic tool in the critically ill patient's assessment. In this scenario the initial fluid therapy, such as it is recommended in the actual clinical guidelines, not always provides the desired results and maintains a considerable incidence of cardiorrespiratory insufficiency. Echocardiography can council us on these patients' clinical handling, not only the initial fluid therapy but also on the best-suited election of the vasoactive/ inotropic treatment and the early detection of complications. It contributes as well to improving the etiological diagnosis, allowing one to know the heart performance with more precision. The objective of this manuscript is to review the more important parameters that can assist the intensivist in theragnosis of hemodynamically unstable patients.

Echocardiographic evaluation during weaning from mechanical ventilation

INTRODUCTION

Echocardiographic, electrocardiographic and other cardiorespiratory variables can change during weaning from mechanical ventilation.

OBJECTIVES

To analyze changes in cardiac function, using Doppler echocardiogram, in critical patients during weaning from mechanical ventilation, using two different weaning methods: pressure support ventilation and T-tube; and comparing patient subgroups: success vs. failure in weaning.

METHODS

Randomized crossover clinical trial including patients under mechanical ventilation for more than 48 h and considered ready for weaning. Cardiorespiratory variables, oxygenation, electrocardiogram and Doppler echocardiogram findings were analyzed at baseline and after 30 min in pressure support ventilation and T-tube. Pressure support ventilation vs. T-tube and weaning success vs. failure were compared using ANOVA and Student's t-test. The level of significance was p<0.05.

RESULTS

Twenty-four adult patients were evaluated. Seven patients failed at the first weaning attempt. No echocardiographic or electrocardiographic differences were observed between pressure support ventilation and T-tube. Weaning failure patients presented increases in left atrium, intraventricular septum thickness, posterior wall thickness and diameter of left ventricle and shorter isovolumetric relaxation time. Successfully weaned patients had higher levels of oxygenation.

CONCLUSION

No differences were observed between Doppler echocardiographic variables and electrocardiographic and other cardiorespiratory variables during pressure support ventilation and T-tube. However cardiac structures were smaller, isovolumetric relaxation time was larger, and oxygenation level was greater in successfully weaned patients.

Hemodynamic changes during weaning: can we assess and predict cardiac-related weaning failure by transthoracic echocardiography?

Cardiac-related failure of weaning from mechanical ventilation is an important reason for prolonged mechanical ventilation, intensive care unit treatment, and increased morbidity and mortality. When transthoracic echocardiography (TTE) is routinely performed before a weaning trial, patients at high risk of cardiac-related failure can be detected by low left ventricular (LV) ejection fraction, diastolic dysfunction, and elevated LV filling pressure. During the weaning trial, a further increase of LV filling pressure and progression of diastolic failure can be observed by repeated TTE. Owing to certain limitations concerning patients and methodology, TTE cannot be employed in every patient and invasive hemodynamic monitoring is still mandatory in selected patients with repetitive weaning failure.