Clinical significance of pulmonary artery occlusion pressure

Expert consensus document: Echocardiography and lung ultrasonography for the assessment and management of acute heart failure

Echocardiography is increasingly recommended for the diagnosis and assessment of patients with severe cardiac disease, including acute heart failure. Although previously considered to be within the realm of cardiologists, the development of ultrasonography technology has led to the adoption of echocardiography by acute care clinicians across a range of specialties. Data from echocardiography and lung ultrasonography can be used to improve diagnostic accuracy, guide and monitor the response to interventions, and communicate important prognostic information in patients with acute heart failure. However, without the appropriate skills and a good understanding of ultrasonography, its wider application to the most acutely unwell patients can have substantial pitfalls. This Consensus Statement, prepared by the Acute Heart Failure Study Group of the ESC Acute Cardiovascular Care Association, reviews the existing and potential roles of echocardiography and lung ultrasonography in the assessment and management of patients with acute heart failure, highlighting the differences from established practice where relevant.

The Routine Use of the Pulmonary Artery Catheter Should Be Abandoned

The pulmonary artery catheter (PAC) is the most common method of measuring cardiac output in cardiac surgery. However, its use has always been questioned in terms of survival benefit, specifically with regard to the accuracy of its measurements and its invasive nature, with the potential for serious complications. In this review we aimed to develop a clear understanding of the pitfalls of the use of PAC, and discuss its risks and available alternatives. We conclude that there is no indication for the routine use of PAC such that clinicians should carefully consider the clinical risks and benefits on a patient by patient basis.

Functional hemodynamic monitoring

Functional hemodynamic monitoring is the assessment of the dynamic interactions of hemodynamic variables in response to a defined perturbation. Recent interest in functional hemodynamic monitoring for the bedside assessment of cardiovascular insufficiency has heightened with the documentation of its accuracy in predicting volume responsiveness using a wide variety of monitoring devices, both invasive and noninvasive, and across multiple patient groups and clinical conditions. However, volume responsiveness, though important, reflects only part of the overall spectrum of functional physiologic variables that can be measured to define the physiologic state and monitor response to therapy.

Temporal evolution of acute respiratory distress syndrome definitions

OBJECTIVE

to review the evolution of acute respiratory distress syndrome (ARDS) definitions and present the current definition for the syndrome.

DATA SOURCE

a literature review and selection of the most relevant articles on ARDS definitions was performed using the MEDLINE®/PubMed® Resource Guide database (last ten years), in addition to including the most important articles (classic articles) that described the disease evolution.

DATA SYNTHESIS

the review included the following subjects: introduction; importance of definition; description of the first diagnostic criterion and subsequently used definitions, such as acute lung injury score; definition by the American-European Consensus Conference, and its limitations; description of the definition by Delphi, and its problems; accuracy of the aforementioned definitions; description of most recent definition (the Berlin definition), and its limitations; and practical importance of the new definition.

CONCLUSIONS

ARDS is a serious disease that remains an ongoing diagnostic and therapeutic challenge. The evolution of definitions used to describe the disease shows that studies are needed to validate the current definition, especially in pediatrics, where the data are very scarce.

Pulmonary artery occlusion pressure may overdiagnose pulmonary artery hypertension in sickle cell disease

BACKGROUND

A high prevalence of Pulmonary Hypertension (PH) in sickle cell disease (SCD) has been reported in several studies. However, few studies that describe the hemodynamics have actually measured pulmonary artery occlusive pressure (PAOP). Furthermore, even PAOP has been shown to be unreliable in discriminating pulmonary artery hypertension from pulmonary venous hypertension. We prospectively examined the accuracy of PAOP using simultaneous left ventricular end diastolic pressure (LVEDP) measurement as the gold standard.

HYPOTHESIS

In patients with SCD, PAOP may not reflect LVEDP leading to over-diagnosis of PAH.

METHODS

We prospectively examined hemodynamic data on 26 patients with SCD, at a large academic center, from 2009 through 2011. These patients underwent simultaneous PAOP and LVEDP measurements.

RESULTS

We tested 106 adult SCD patients with 2-D Echocardiography for evaluation of PH. Of the 106 patients, 43 (41%) were found to have a tricuspid regurgitant jet velocity ≥ 2.5 m/sec. Of these 43, 26 patients underwent right heart catheterization (RHC) and simultaneous measurement of LVEDP. Twelve patients among the 106 (11.1%) patients were found to have PH. Eight of these (7.5 %) had PAH by PAOP criteria but only 4/106 (3/7%) had PAH by LVEDP criteria. PAOP significantly underestimated the LVEDP in both the PH group and group with normal hemodynamics (p=0.00004). BNP, and creatinine levels significantly increased in PAH group (p< 0.02, 0.01, 0.03). PAOP misclassified 50% of patients in this sickle cell disease cohort. In conclusion, PAOP may underestimate LVEDP in sickle cell patients with pulmonary hypertension and can lead to misclassification.

Supporting hemodynamics: what should we target? What treatments should we use?

Assessment and monitoring of hemodynamics is a cornerstone in critically ill patients as hemodynamic alteration may become life-threatening in a few minutes. Defining normal values in critically ill patients is not easy, because 'normality' is usually referred to healthy subjects at rest. Defining 'adequate' hemodynamics is easier, which embeds whatever pressure and flow set is sufficient to maintain the aerobic metabolism. We will refer to the unifying hypothesis proposed by Schrier several years ago. Accordingly, the alteration of three independent variables - heart (contractility and rate), vascular tone and intravascular volume - may lead to underfilling of the arterial tree, associated with reduced (as during myocardial infarction or hemorrhage) or expanded (sepsis or cirrhosis) plasma volume. The underfilling is sensed by the arterial baroreceptors, which activate primarily the sympathetic nervous system and renin-angiotensin-aldosterone system, as well as vasopressin, to restore the arterial filling by increasing the vascular tone and retaining sodium and water. Under 'normal' conditions, therefore, the homeostatic system is not activated and water/sodium excretion, heart rate and oxygen extraction are in the range found in normal subjects. When arterial underfilling occurs, the mechanisms are activated (sodium and water retention) - associated with low central venous oxygen saturation (ScvO₂) if underfilling is caused by low flow/hypovolemia, or with normal/high ScvO₂ if associated with high flow/hypervolemia. Although the correction of hemodynamics should be towards the correction of the independent determinants, the usual therapy performed is volume infusion. An accepted target is ScvO₂ >70%, although this ignores the arterial underfilling associated with volume expansion/high flow. For large-volume resuscitation the worst solution is normal saline solution (chloride load, strong ion difference = 0, acidosis). To avoid changes in acid-base equilibrium the strong ion difference of the infused solution should be equal to the baseline bicarbonate concentration.

Predictors of pulmonary edema formation during fluid loading in the critically ill with presumed hypovolemia*

OBJECTIVES

It is largely unknown why extravascular lung water may increase during fluid loading in the critically ill with presumed hypovolemia. In this study we evaluated the hemodynamic predictors of such an increase.

DESIGN

A prospective observational study.

PATIENTS

Sixty-three presumed hypovolemic mechanically ventilated patients (22 septic and 41 nonseptic patients).

INTERVENTION

Fluid loading with saline or colloid fluids guided by (changes in) cardiac filling pressures.

MEASUREMENTS AND MAIN RESULTS

Before and after fluid-loading, hemodynamic and respiratory variables were recorded, including variables obtained by transpulmonary dilution such as cardiac index, pulmonary blood volume index, and extravascular lung water. Baseline parameters and change in parameters were compared between patients with a change in extravascular lung water <10% and patients with a change in extravascular lung water ≥ 10%. Predictive values for change in extravascular lung water ≥ 10% were evaluated. Baseline cardiac index and pulmonary blood volume index were higher, whereas change in cardiac index, change in pulmonary blood volume index, and change in PaO2/FIO2 ratio were lower in patients with a change in extravascular lung water ≥ 10% than in patients with a change in extravascular lung water <10%. The change in extravascular lung water correlated to baseline cardiac index (r = 0.17; p = .001), baseline pulmonary blood volume index (r = 0.15; p = .001), change in pulmonary blood volume index (r = 0.16; p < .001), and change in PaO2/FIO2 ratio (r = 0.13; p = .004). In multiple logistic regression analysis baseline cardiac index, baseline pulmonary blood volume index, the change in cardiac index, change in pulmonary blood volume index, and change in PaO2/FIO2 ratio individually contributed to prediction of a change in extravascular lung water ≥ 10%, independent of the presence of sepsis, pulmonary vascular permeability, and cardiac filling pressures. A change in extravascular lung water ≥ 10% was predicted by baseline cardiac index (77% sensitivity, 98% specificity) and pulmonary blood volume index (92% sensitivity, 68% specificity), and by change in cardiac index (69% sensitivity, 59% specificity), change in pulmonary blood volume index (77% sensitivity, 82% specificity), and change in PaO2/FIO2 ratio (77% sensitivity, 66% specificity).

CONCLUSION

Extravascular lung water increase during fluid loading in the critically ill is predicted by a plateau of cardiac function and pulmonary vascular filling at baseline, rather than by pulmonary vascular permeability and filling pressures. Increasing extravascular lung water is further reflected by a decrease of PaO2/FIO2 ratio. These observations may help preventing pulmonary fluid overloading.

[Assessment of cardiovascular preload and response to volume expansion]

Volume expansion is used in patients with hemodynamic insufficiency in an attempt to improve cardiac output. Finding criteria to predict fluid responsiveness would be helpful to guide resuscitation and to avoid excessive volume effects. Static and dynamic indicators have been described to predict fluid responsiveness under certain conditions. In this review we define preload and preload-responsiveness concepts. A description is made of the characteristics of each indicator in patients subjected to mechanical ventilation or with spontaneous breathing.

Effect of balloon inflation volume on pulmonary artery occlusion pressure in patients with and without pulmonary hypertension

BACKGROUND

Pulmonary artery occlusion pressure (PAOP) is used to differentiate patients with pulmonary hypertension (PH) associated with left-sided heart disease from other etiologies. Technical errors in the measurement of PAOP are common and lead to incorrect classification of the etiology of PH. We investigated the agreement among PAOP measurements obtained from both pulmonary arteries with balloon full (1.5 mL) and half (0.75 mL) inflation in patients undergoing right-sided heart catheterization for suspected PH.

METHODS

Thirty-seven patients suspected or known to have PH who underwent right-sided heart catheterization were included. Seventy-six percent had PH (mean pulmonary arterial pressure > 25 mm Hg). The validity of the measurements was assessed by using five preestablished criteria based on hemodynamic, fluoroscopic, and gasometric data. For each patient, the measurement that most likely represented the left atrial pressure was labeled "best PAOP."

RESULTS

Seventy percent of all the PAOP measurements met at least four of the five preestablished criteria for validity. In patients with PH (n = 28), the mean ± SE PAOP was 23.1 ± 2 and 19.1 ± 2 mm Hg for balloon full and half inflation, respectively, in the right pulmonary artery and 23.54 ± 2 and 19.07 ± 2 mm Hg for balloon full and half inflation, respectively, in the left pulmonary artery (P = .05). Bland-Altman analysis revealed lower bias and narrower limits of agreement with balloon half inflation. Wedge angiography showed that some balloon inflations failed to occlude upstream flow, whereas others had collateral vessels draining after the occlusion.

CONCLUSIONS

PAOP can be falsely elevated in patients with PH according to the balloon inflation volume. Balloon half inflation was safe and correlated with higher precision and lower bias in the PAOP measurements.

Static measures of preload assessment

This article focuses on static methods for determining preload, specifically pressure and volumetric indices measured at the bedside. The underlying ventricular function will determine where the patient is located on Frank-Starling ventricular function curve and the patient's response to a fluid challenge. The proper interpretation and use of such measures, coupled with an understanding of their limitations and knowledge of alternative methods, is necessary to guide properly volume resuscitation in the critically ill.

Transpulmonary thermodilution-derived cardiac function index identifies cardiac dysfunction in acute heart failure and septic patients: an observational study

INTRODUCTION

There is limited clinical experience with the single-indicator transpulmonary thermodilution (pulse contour cardiac output, or PiCCO) technique in critically ill medical patients, particularly in those with acute heart failure (AHF). Therefore, we compared the cardiac function of patients with AHF or sepsis using the pulmonary artery catheter (PAC) and the PiCCO technology.

METHODS

This retrospective observational study was conducted in the medical intensive care unit of a university hospital. Twelve patients with AHF and nine patients with severe sepsis or septic shock had four simultaneous hemodynamic measurements by PAC and PiCCO during a 24-hour observation period. Comparisons between groups were made with the use of the Mann-Whitney U test. Including all measurements, correlations between data pairs were established using linear regression analysis and are expressed as the square of Pearson's correlation coefficients (r2).

RESULTS

Compared to septic patients, AHF patients had a significantly lower cardiac index, cardiac function index (CFI), global ejection fraction, mixed venous oxygen saturation (SmvO2) and pulmonary vascular permeability index, but higher pulmonary artery occlusion pressure. All patients with a CFI less than 4.5 per minute had an SmvO2 not greater than 70%. In both groups, the CFI correlated with the left ventricular stroke work index (sepsis: r2 = 0.30, P < 0.05; AHF: r2 = 0.23, P < 0.05) and cardiac power (sepsis: r2 = 0.39, P < 0.05; AHF: r2 = 0.45, P < 0.05).

CONCLUSIONS

In critically ill medical patients, assessment of cardiac function using transpulmonary thermodilution technique is an alternative to the PAC. A low CFI identifies cardiac dysfunction in both AHF and septic patients.

Acute respiratory distress syndrome 40 years later: time to revisit its definition

OBJECTIVE

Acute respiratory distress syndrome is a common disorder associated with significant mortality and morbidity. The aim of this article is to critically evaluate the definition of acute respiratory distress syndrome and examine the impact the definition has on clinical practice and research.

DATA SOURCES

Articles from a MEDLINE search (1950 to August 2007) using the Medical Subject Heading respiratory distress syndrome, adult, diagnosis, limited to the English language and human subjects, their relevant bibliographies, and personal collections, were reviewed.

DATA SYNTHESIS

The definition of acute respiratory distress syndrome is important to researchers, clinicians, and administrators alike. It has evolved significantly over the last 40 years, culminating in the American-European Consensus Conference definition, which was published in 1994. Although the American-European Consensus Conference definition is widely used, it has some important limitations that may impact on the conduct of clinical research, on resource allocation, and ultimately on the bedside management of such patients. These limitations stem partially from the fact that as defined, acute respiratory distress syndrome is a heterogeneous entity and also involve the reliability and validity of the criteria used in the definition. This article critically evaluates the American-European Consensus Conference definition and its limitations. Importantly, it highlights how these limitations may contribute to clinical trials that have failed to detect a potential true treatment effect. Finally, recommendations are made that could be considered in future definition modifications with an emphasis on the significance of accurately identifying the target population in future trials and subsequently in clinical care.

CONCLUSION

How acute respiratory distress syndrome is defined has a significant impact on the results of randomized, controlled trials and epidemiologic studies. Changes to the current American-European Consensus Conference definition are likely to have an important role in advancing the understanding and management of acute respiratory distress syndrome.

Hemodynamic evaluation and monitoring in the ICU

Hemodynamic monitoring, a cornerstone in the management of the critically ill patient, is used to identify cardiovascular insufficiency, its probable cause, and response to therapy. Still it is difficult to document the efficacy of monitoring because no device improves outcome unless coupled to a treatment that improves outcome. Several clinical trials have consistently documented that preoptimization for high-risk surgery patients treated in the operating room and early (< 12 h) goal-directed resuscitation in septic patients treated in the emergency department reduce morbidity, mortality, and resource use (costs) when the end points of resuscitation were focused on surrogate measures of adequacy of global oxygen delivery (Do2). The closer the resuscitation is to the insult, the greater the benefit. When resuscitation was started after ICU admission in high-risk surgical patients, reduced length of stay was also seen. The focus of these monitoring protocols is to establish a mean arterial pressure > 65 mm Hg and then to increase Do2 to 600 mL/min/m2 within the first few minutes to hours of presentation. To accomplish these goals, hemodynamic monitoring focuses more on measures of cardiac output and mixed venous oxygen saturation to access adequacy of resuscitation efforts than on filling pressures. Although these protocols reduce mortality and morbidity is selected high-risk patient groups, the widespread use of monitoring-driven treatment protocols has not yet happened, presumably because all studies have been single-center trials using a single, proprietary blood flow-monitoring device. Multicenter trials are needed of early goal-directed therapies for all patients presenting in shock of various etiologies and when the protocol and not the monitoring device is the primary variable.

Prognostic values of B-type natriuretic peptide in severe sepsis and septic shock

OBJECTIVE

To investigate the changes in B-type natriuretic peptide concentrations in patients with severe sepsis and septic shock and to investigate the value of B-type natriuretic peptide in predicting intensive care unit outcomes.

DESIGN

Prospective observational study.

SETTING

General intensive care unit.

PATIENTS

Forty patients with severe sepsis or septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

B-type natriuretic peptide measurements and echocardiography were carried out daily for 10 consecutive days. In-hospital mortality and length of stay were recorded. The admission B-type natriuretic peptide concentrations were generally increased (747 +/- 860 pg/mL). B-type natriuretic peptide levels were elevated in patients with normal left ventricular systolic function (568 +/- 811 pg/mL), with sepsis-related reversible cardiac dysfunction (630 +/- 726 pg/mL), and with chronic cardiac dysfunction (1311 +/- 1097 pg/mL). There were no significance changes in B-type natriuretic peptide levels over the 10-day period. The daily B-type natriuretic peptide concentrations for the first 3 days neither predicted in-hospital mortality nor correlated with length of intensive care unit or hospital stay.

CONCLUSION

B-type natriuretic peptide concentrations were increased in patients with severe sepsis or septic shock regardless of the presence or absence of cardiac dysfunction. Neither the B-type natriuretic peptide levels for the first 3 days nor the daily changes in B-type natriuretic peptide provided prognostic value for in-hospital mortality and length of stay in this mixed group of patients, which included patients with chronic cardiac dysfunction.

Practical issues of hemodynamic monitoring at the bedside

The hemodynamic monitoring of a surgical patient acquires a major relevance in high-risk patients and those suffering from surgical diseases associated with hemodynamic instability, such as hemorrhagic or septic shock. This article reviews the fundamental physiologic principles needed to understand hemodynamic monitoring at the bedside. Monitoring defines stability, instability, and response to therapy. The major hemodynamic parameters measured and derived from invasive hemodynamic monitoring, such as arterial, central venous, and pulmonary catheterization, are discussed, as are its clinical indications, benefits, and complications. The current clinical data relevant to hemodynamic monitoring are reviewed and discussed.

Let us use the pulmonary artery catheter correctly and only when we need it

OBJECTIVE

To clarify the issues related to the use of the pulmonary artery catheter within a rational clinical perspective.

RESULTS

Barriers include a) increased patient risk of pulmonary artery catheter placement; b) ability to measure similar variables via central venous catheterization, echocardiography, or other less invasive techniques; c) increased cost; d) inaccurate measurements; e) incorrect interpretation and application of pulmonary artery catheter-derived variables; and f) lack of proven benefit of pulmonary artery catheter use in the overall management of patients.

INTERPRETATION

a) The risks are mainly due to insertion of a central catheter, not a pulmonary artery catheter; b) continuous monitoring of left ventricular filling pressures, pulmonary vascular pressures, and mixed venous oxygen saturation is a unique feature; c) additional costs are minimal relative to the cost of intensive care; d) measurement errors require ongoing programmatic educational efforts; e) pulmonary artery catheter-derived data need to be used within the context of a defined treatment protocol; and f) no monitoring device, no matter how simple or sophisticated, will improve patient-centered outcomes unless coupled with a treatment that, itself, improves outcome.

CONCLUSION

A treatment protocol for the use of pulmonary artery catheter-derived variables is proposed that could serve as a basis for a prospective clinical trial.

Ventilator-associated lung injury in patients without acute lung injury at the onset of mechanical ventilation

OBJECTIVE

Although ventilation with small tidal volumes is recommended in patients with established acute lung injury, most others receive highly variable tidal volume aimed in part at normalizing arterial blood gas values. We tested the hypothesis that acute lung injury, which develops after the initiation of mechanical ventilation, is associated with known risk factors for ventilator-induced lung injury such as ventilation with large tidal volume.

DESIGN

Retrospective cohort study.

SETTING

Four intensive care units in a tertiary referral center.

PATIENTS

Patients who received invasive mechanical ventilation for > or = 48 hrs between January and December 2001.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The main outcome of interest, acute lung injury, was assessed by independent review of daily digital chest radiographs and arterial blood gases. Ventilator settings, hemodynamics, and acute lung injury risk factors were extracted from the Acute Physiology and Chronic Health Evaluation III database and the patients' medical records. Of 332 patients who did not have acute lung injury from the outset, 80 patients (24%) developed acute lung injury within the first 5 days of mechanical ventilation. When expressed per predicted body weight, women were ventilated with larger tidal volume than men (mean 11.4 vs. 10.4 mL/kg predicted body weight, p <.001) and tended to develop acute lung injury more often (29% vs. 20%, p =.068). In a multivariate analysis, the main risk factors associated with the development of acute lung injury were the use of large tidal volume (odds ratio 1.3 for each mL above 6 mL/kg predicted body weight, p <.001), transfusion of blood products (odds ratio, 3.0; p < 0.001), acidemia (pH < 7.35; odds ratio, 2.0; p =.032) and a history of restrictive lung disease (odds ratio, 3.6; p =.044).

CONCLUSIONS

The association between the initial tidal volume and the development of acute lung injury suggests that ventilator-associated lung injury may be an important cause of this syndrome. Height and gender should be considered when setting up the ventilator. Strong consideration should be given to limiting large tidal volume, not only in patients with established acute lung injury but also in patients at risk for acute lung injury.

Intraoperative monitoring during vascular surgery

The principal objectives of intraoperative monitoring are to improve perioperative outcome, facilitate surgery and reduce adverse events, using continuously collected data of cardiopulmonary,neurologic and metabolic function to guide pharmacologic and physiologic therapy. Although sophisticated and reliable apparatus may be used to collect these data they are useless, or even harmful, without proper interpretation. This article provides a comprehensive overview of recent publications on the history,philosophy, and semantics of monitoring.