Combined thermodilution and two-dimensional echocardiographic evaluation of right ventricular function during respiratory support with PEEP

Cardiopulmonary interactions in left heart failure

The primary impact of ventilation and ventilatory efforts on left ventricular (LV) function in left ventricular dysfunction relate to how changes in intrathoracic pressure (ITP) alter the pressure gradients for venous return into the chest and LV ejection out of the chest. Spontaneous inspiratory efforts by decreasing ITP increase both of these pressure gradients increasing venous blood flow and impeding LV ejection resulting in increased intrathoracic blood volume. In severe heart failure states when lung compliance is reduced, or airway resistance is increased these negative swings in ITP can be exacerbated leading to LV failure and acute cardiogenic pulmonary edema. By merely reversing these negative swings in ITP by the use of non-invasive continuous positive airway pressure (CPAP), these profoundly detrimental forces can be immediately reversed, and cardiovascular stability can be restored in moments. This forms the clinical rationale for the immediate use of CPAP for the treatment of acute cardiogenic pulmonary edema. Increasing ITP during positive pressure ventilation decreases the pressure gradients for venous return and LV ejection decreasing intrathoracic blood volume. In a hypovolemic patient even with LV dysfunction this can result in hypotension due to inadequate LV preload. Minor increases in ITP as occur using pressure-limited positive-pressure ventilation primarily reverse the increased LV afterload of negative swings in ITP and if fluid overload was already present, minimally alter cardiac output. The effect of changes in lung volume on LV function are related primarily to its effects on right ventricular (RV) function through changes in pulmonary vascular resistance and overdistention (hyperinflation). In acute lung injury with alveolar collapse, positive pressure ventilation may reduce pulmonary vascular resistance if alveolar recruitment predominates. Hyperinflation, however, impedes diastolic filling while simultaneously increasing pulmonary vascular resistance. Thus, increasing lung volume can reduce RV afterload by reversing hypoxic pulmonary vasoconstriction or increase afterload by overdistention. Hyperinflation can also impede RV filling. All of these processes can be readily identified at the bedside using echocardiography.

The increase in cardiac output induced by a decrease in positive end-expiratory pressure reliably detects volume responsiveness: the PEEP-test study

BACKGROUND

In patients on mechanical ventilation, positive end-expiratory pressure (PEEP) can decrease cardiac output through a decrease in cardiac preload and/or an increase in right ventricular afterload. Increase in central blood volume by fluid administration or passive leg raising (PLR) may reverse these phenomena through an increase in cardiac preload and/or a reopening of closed lung microvessels. We hypothesized that a transient decrease in PEEP (PEEP-test) may be used as a test to detect volume responsiveness.

METHODS

Mechanically ventilated patients with PEEP ≥ 10 cmH₂O ("high level") and without spontaneous breathing were prospectively included. Volume responsiveness was assessed by a positive PLR-test, defined as an increase in pulse-contour-derived cardiac index (CI) during PLR ≥ 10%. The PEEP-test consisted in reducing PEEP from the high level to 5 cmH₂O for one minute. Pulse-contour-derived CI (PiCCO2) was monitored during PLR and the PEEP-test.

RESULTS

We enrolled 64 patients among whom 31 were volume responsive. The median increase in CI during PLR was 14% (11-16%). The median PEEP at baseline was 12 (10-15) cmH₂O and the PEEP-test resulted in a median decrease in PEEP of 7 (5-10) cmH₂O, without difference between volume responsive and unresponsive patients. Among volume responsive patients, the PEEP-test induced a significant increase in CI of 16% (12-20%) (from 2.4 ± 0.7 to 2.9 ± 0.9 L/min/m², p < 0.0001) in comparison with volume unresponsive patients. In volume unresponsive patients, PLR and the PEEP-test increased CI by 2% (1-5%) and 6% (3-8%), respectively. Volume responsiveness was predicted by an increase in CI > 8.6% during the PEEP-test with a sensitivity of 96.8% (95% confidence interval (95%CI): 83.3-99.9%) and a specificity of 84.9% (95%CI 68.1-94.9%). The area under the receiver operating characteristic curve of the PEEP-test for detecting volume responsiveness was 0.94 (95%CI 0.85-0.98) (p < 0.0001 vs. 0.5). Spearman's correlation coefficient between the changes in CI induced by PLR and the PEEP-test was 0.76 (95%CI 0.63-0.85, p < 0.0001).

CONCLUSIONS

A CI increase > 8.6% during a PEEP-test, which consists in reducing PEEP to 5 cmH₂O, reliably detects volume responsiveness in mechanically ventilated patients with a PEEP ≥ 10 cmH₂O. Trial registration ClinicalTrial.gov (NCT 04,023,786). Registered July 18, 2019. Ethics Committee approval CPP Est III (N° 2018-A01599-46).

Development of an integrated model of cardiovascular and pulmonary physiology for the evaluation of mechanical ventilation strategies

We describe the development of an integrated cardiovascular and pulmonary model for use in the investigation of novel mechanical ventilation strategies in the intensive care unit. The cardiac model includes the cardiac chambers, the pulmonary circulation and the systemic circulation. The modeling of complex mechanisms for vascular segments, time varying elastance functions of cardiovascular components and the effect of vascular resistances, in health and disease under the influence of mechanical ventilation is investigated. The resulting biomedical simulator can aid in understanding the underlying pathophysiology of critically-ill patients and facilitate the development of more effective therapeutic strategies for evaluation in clinical trials.

Modern Protective Ventilation Strategies: Impact upon the Right Heart

‘Protective ventilation’ for acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) is a major advance in intensive care medicine. However, components of protective ventilation expose the right heart to challenges. Acute cor pulmonale (ACP), patent foramen ovale (PFO) and right ventricular failure (RVF) are recognised complications that could potentially reduce the benefit of protective ventilation. We sought to determine the rates of ACP, PFO and RVF in critically ill adults undergoing protective ventilation with ARDS/ALI and to identify their impact on mortality and critical illness acuity. A comprehensive search of electronic databases including Medline (OVID, EmBase) and CINAHL (EBSCO) was undertaken, including Cochrane Library and international registries, between January 1991 and December 2011. A systematic review identified a total of 248 articles; 27 were reviewed in full and 22 studies were included. All 22 included studies were observational or quasi-experimental with no randomised, controlled trials available. ACP was present in 16–100%, PFO 1.3–22.0% and RVF 9.6–26.0%. Neither ACP nor PFO was associated with an adverse effect on mortality and ACP seemed reversible in survivors; however both ACP and PFO were associated with prolonged need for ICU support. RVF was variously associated with no increase in mortality to an odds ratio 5.1 for death in multivariate analysis. There was marked heterogeneity in the studies included, explaining the range of observed values. Recommendations for future research and practice were produced. Modern protective ventilation during ARDS has been shown to exert inconsistent effects on the right heart which may be of clinical significance. Further research is needed to determine these effects better.

Predicting fluid responsiveness with transthoracic echocardiography is not yet evidence based

An essential part of intensive care is to accurately identify fluid responders among patients with circulatory failure. Over the past few years, new techniques have been assessed for rapid and non-invasive prediction of fluid responsiveness. As transthoracic echocardiography (TTE) is becoming an integrated tool in the intensive care unit, this systematic review examined studies evaluating the predictive value of TTE for fluid responsiveness. In October 2012, we searched Pubmed, EMBASE and Web of Science for studies evaluating the predictive value of TTE-derived variables for fluid responsiveness defined as change in thermodilution cardiac output or stroke volume after a fluid challenge or a passive leg raising test. The use of thermodilution was used as inclusion criterion because it is the only method validated to show the change in cardiac output or stroke volume, which defines fluid responsiveness. Of the 4294 evaluated citations, only one study fully met our inclusion criteria. In this study, the predictive value of variations in inferior vena cava diameter (> 16%) for fluid responsiveness was moderate with sensitivity of 71% [95% confidence interval (CI) 44-90], specificity of 100% (95% CI 73-100) and an area under the receiver operating curve of 0.90 (95% CI 0.73-0.98). Only one study of TTE-based methods fulfilled the criteria for valid assessment of fluid responsiveness. Before recommending the use of TTE in predicting fluid responsiveness, proper evaluation including thermodilution technique as the gold standard is needed.

Point of care cardiac ultrasound applications in the emergency department and intensive care unit--a review

The use of point of care echocardiography by non-cardiologist in acute care settings such as the emergency department (ED) or the intensive care unit (ICU) is very common. Unlike diagnostic echocardiography, the scope of such point of care exams is often restricted to address the clinical questions raised by the patient's differential diagnosis or chief complaint in order to inform immediate management decisions. In this article, an overview of the most common applications of this focused echocardiography in the ED and ICU is provided. This includes but is not limited to the evaluation of patients experiencing hypotension, cardiac arrest, cardiac trauma, chest pain and patients after cardiac surgery.

Perioperative management of pulmonary hypertension in children with critical heart disease

OPINION STATEMENT

Pulmonary hypertension (PHTN) is common to a variety of conditions occurring in infants and children presenting to the intensive care unit. A fundamental understanding of the response of the right ventricle to an increase in afterload and the clinical syndromes responsible for PHTN is essential for managing patients with PHTN and critical heart disease. There are important distinguishing features between PHTN syndromes, and although one form of PHTN may predominate, often more than one mechanism of PHTN is contributing to the pathophysiologic state. Thus, it is imperative to tailor therapies accordingly in order to optimize outcomes.

Pathophysiology of right ventricular failure in pulmonary hypertension

This review focuses on right ventricular anatomy and function and the significance of ventricular interdependence in the response of the right ventricle to an increase in afterload. This is followed by a discussion of the pathophysiology of right ventricular failure in pulmonary arterial hypertension as well as in other clinical syndromes of pulmonary hypertension. Pulmonary hypertension is common in critically ill children and is associated with several conditions. Regardless of the etiology, an increase in right ventricular afterload leads to a number of compensatory changes in cardiovascular physiology. These changes are not altogether intuitive and require an understanding of right ventricular physiology and ventricular interdependence to optimize the care of these patients.

Impact of acute hypercapnia and augmented positive end-expiratory pressure on right ventricle function in severe acute respiratory distress syndrome

PURPOSE

To evaluate the effects of acute hypercapnia induced by positive end-expiratory pressure (PEEP) variations at constant plateau pressure (P (plat)) in patients with severe acute respiratory distress syndrome (ARDS) on right ventricular (RV) function.

METHODS

Prospective observational study in two academic intensive care units enrolling 11 adults with severe ARDS (PaO(2)/FiO(2) <150 mmHg at PEEP >5 cmH(2)O). We compared three ventilatory strategies, each used for 1 h, with P (plat) at 22 (20-25) cmH(2)O: low PEEP (5.4 cmH(2)O) or high PEEP (11.0 cmH(2)O) with compensation of the tidal volume reduction by either a high respiratory rate (high PEEP/high rate) or instrumental dead space decrease (high PEEP/low rate). We assessed RV function (transesophageal echocardiography), alveolar dead space (expired CO(2)), and alveolar recruitment (pressure-volume curves).

RESULTS

Compared to low PEEP, PaO(2)/FiO(2) ratio and alveolar recruitment were increased with high PEEP. Alveolar dead space remained unchanged. Both high-PEEP strategies induced higher PaCO(2) levels [71 (60-94) and 75 (53-84), vs. 52 (43-68) mmHg] and lower pH values [7.17 (7.12-7.23) and 7.20 (7.16-7.25) vs. 7.30 (7.24-7.35)], as well as RV dilatation, LV deformation and a significant decrease in cardiac index. The decrease in stroke index tended to be negatively correlated to the increase in alveolar recruitment with high PEEP.

CONCLUSIONS

Acidosis and hypercapnia induced by tidal volume reduction and increase in PEEP at constant P (plat) were associated with impaired RV function and hemodynamics despite positive effects on oxygenation and alveolar recruitment ( ClinicalTrials.gov #NCT00236262).

Cardiopulmonary interaction

OBJECTIVE

To highlight and review the physiology and pathophysiology of cardiopulmonary interaction in the critically ill pediatric patient.

DATA SOURCE

A MEDLINE-based literature source. OUTLINE OF REVIEW: This review is divided into two sections: 1) The physiologic basis of cardiopulmonary interaction, and 2) critical clinical conditions in which cardiac and/or pulmonary dysfunction impact each other in the provision of adequate oxygen delivery. The physiology section focuses on the original research identifying fundamental volume-pressure and pressure-flow relationships and then proceeds to discuss how changes in intrathoracic pressure and lung volume affect ventricular loading conditions. The clinical section chooses several common scenarios in which this normal physiology is altered and an understanding of the impact of these physiologic aberrations on cardiac and/or pulmonary function is required to make sound management decisions.

CONCLUSIONS

Improving oxygen transport balance is the primary goal in the management of children with life-threatening disorders. To optimize the opportunity for a successful outcome, the intensivist must understand the complex relationship between the cardiac and pulmonary systems in the effort to provide sufficient oxygen to meet the body's metabolic demands. Furthermore, the application of therapies separately designed to support the function of the heart and the function of the lungs may be synergistic or antagonistic, further complicating the management scheme. We conclude that this review will encourage the reader to pursue further literature or perhaps engage in further research related to this often underappreciated but vital interplay between cardiac and pulmonary functions.

Right ventricular dysfunction

PURPOSE OF REVIEW

Until recently the right ventricle's role in myocardial dynamics has not been fully appreciated. This article provides an overview of the pathophysiology, imaging and management of right ventricular dysfunction.

RECENT FINDINGS

That levosimendan may promote right ventricular function opens new avenues for treatment. In addition there are existing therapies such as phosphodiesterase inhibitors and nitric oxide, which offer yet further modalities to improve outcome in right ventricular failure. How these drugs are used, in combination or alone, in conjunction with ventilatory and cardiovascular strategies has not been evaluated in multicentred randomized controlled trials.

SUMMARY

Acute right ventricular dysfunction is relatively common. There is a lack of convincing evidence in favour of any single treatment modality. Imaging methods now permit a more accurate evaluation of the right ventricle and its function. Combining treatments may offer significant advantages and the imaging and monitoring available allows real-time assessment of the response to intervention. This article illustrates how incomplete our knowledge of this condition and its management within the critical care setting is and reinforces previous calls for suitably designed trials to evaluate and develop guidelines for existing strategies and therapeutic agents.

Effects of levosimendan on right ventricular afterload in patients with acute respiratory distress syndrome: a pilot study

OBJECTIVE

Acute respiratory distress syndrome (ARDS) is frequently associated with increased pulmonary vascular resistance and thus with systolic load of the right ventricle. We hypothesized that levosimendan, a new calcium sensitizer with potential pulmonary vasodilator properties, improves hemodynamics by unloading the right ventricle in patients with ARDS.

DESIGN

Prospective, randomized, placebo-controlled, pilot study.

SETTING

Twenty-two-bed multidisciplinary intensive care unit of a university hospital.

PATIENTS

Thirty-five patients with ARDS in association with septic shock.

INTERVENTIONS

Patients were randomly allocated to receive a 24-hr infusion of either levosimendan 0.2 microg/kg/min (n = 18) or placebo (n = 17). Data from right heart catheterization, cardiac magnetic resonance, arterial and mixed venous oxygen tensions and saturations, and carbon dioxide tensions were obtained before and 24 hrs after drug infusion.

MEASUREMENTS AND MAIN RESULTS

At a mean arterial pressure between 70 and 80 mm Hg (sustained with norepinephrine infusion), levosimendan increased cardiac index (from 3.8 +/- 1.1 to 4.2 +/- 1.0 L/min/m) and decreased mean pulmonary artery pressure (from 29 +/- 3 to 25 +/- 3 mm Hg) and pulmonary vascular resistance index (from 290 +/- 77 to 213 +/- 50 dynes/s/cm(5)/m(2); each p < .05). Levosimendan also decreased right ventricular end-systolic volume and increased right ventricular ejection fraction (p < .05). In addition, levosimendan increased mixed venous oxygen saturation (from 63 +/- 8 to 70 +/- 8%; p < .01).

CONCLUSIONS

This study provides evidence that levosimendan improves right ventricular performance through pulmonary vasodilator effects in septic patients with ARDS. A large multiple-center trial is needed to investigate whether levosimendan is able to improve the overall prognosis of patients with sepsis and ARDS.

Fluid responsiveness in spontaneously breathing patients: A review of indexes used in intensive care

OBJECTIVE

In spontaneously breathing patients, indexes predicting hemodynamic response to volume expansion are very much needed. The present review discusses the clinical utility and accuracy of indexes tested as bedside indicators of preload reserve and fluid responsiveness in hypotensive, spontaneously breathing patients.

DATA SOURCE

We conducted a literature search of the MEDLINE database and the trial register of the Cochrane Group.

STUDY SELECTION

Identification of reports investigating, prospectively, indexes of fluid responsiveness in spontaneously breathing critically ill patients. All the studies defined the response to fluid therapy after measuring cardiac output and stroke volume using the thermodilution technique. We did not score the methodological quality of the included studies before the data analysis.

DATA EXTRACTION

A total of eight prospective clinical studies in critically ill patients were included. Only one publication evaluated cardiac output changes induced by fluid replacement in a selected population of spontaneously breathing critically ill patients.

DATA SYNTHESIS

Based on this review, we can only conclude that static indexes are valuable tools to confirm that the fluid volume infused reaches the cardiac chambers, and therefore these indexes inform about changes in cardiac preload. However, respiratory variation in right atrial pressure, which represents a dynamic measurement, seems to identify hypotension related to a decrease in preload and to distinguish between responders and nonresponders to a fluid challenge.

CONCLUSIONS

Further studies should address the question of the role of static indexes in predicting cardiac output improvement following fluid infusion in spontaneously breathing patients.

Continuous assessment of right ventricular ejection fraction: new pulmonary artery catheter versus transoesophageal echocardiography

In 25 cardiac surgical patients, right ventricular ejection fraction was continuously measured with a new pulmonary artery catheter and transoesophageal echocardiography, scanning the 'fractional area change' in a standardised transatrial cross section area. Measurements were recorded at three predefined time points (pre-, intra-, and postoperatively). Both methods were compared using the Bland-Altman analysis. Comparing right ventricular ejection fraction values obtained from the pulmonary artery catheter with those assessed by transoesophageal echocardiography, bias was -3.7%, with a precision of 30.9%. Bias and precision significantly improved when the heart rate was less than 100 beats.min(-1), pulmonary artery pressures were low and cardiac performance adequate. In conclusion, the new continuous pulmonary artery catheter system appears to be a valid and useful bedside monitoring device in the haemodynamic management of critically ill patients.

Determination of right ventricular function by transesophageal echocardiography: impact of proximal right coronary artery stenosis

STUDY OBJECTIVE

To investigate whether transesophageal echocardiography (TEE) can provide accurate information on right ventricular (RV) function in patients with right coronary artery (RCA) stenosis, given that a decrease in blood supply from the RCA may invalidate the use of single 2-D echocardiography imaging plane as a guide to RV function.

DESIGN

Prospective, nonblinded study.

SETTING

University hospital.

PATIENTS

30 adult patients undergoing elective cardiac or vascular procedures.

INTERVENTIONS

Patients were classified into two groups according to the presence or absence of the proximal RCA (segment 1 or 2) stenosis. Group A patients had no obstructive lesions in the proximal RCA (n = 15). Group B patients had 75% or greater obstructive lesions in the proximal RCA (n = 15).

MEASUREMENTS AND MAIN RESULTS

After induction of anesthesia, RV function was evaluated by both fast-response thermodilution pulmonary artery catheter and TEE. Transesophageal echocardiography-derived RV fractional area change (FAC) and tricuspid annular plane systolic excursion ratio (TAPSE ratio) were compared with thermodilution-derived RV ejection fraction (EF) using linear regression analysis. Transesophageal echocardiography-derived RV end-diastolic area (EDA) was compared with thermodilution-derived end-diastolic volume (EDV). Both methods showed a good correlation in RV, EDV, and EF in Group A, but no correlations in Group B.

CONCLUSIONS

Transesophageal echocardiography does not provide reliable information on RVEF and EDV when proximal RCA stenosis is present.

Fluid responsiveness in mechanically ventilated patients: a review of indices used in intensive care

OBJECTIVE

In mechanically ventilated patients the indices which assess preload are used with increasing frequency to predict the hemodynamic response to volume expansion. We discuss the clinical utility and accuracy of some indices which were tested as bedside indicators of preload reserve and fluid responsiveness in hypotensive patients under positive pressure ventilation.

RESULTS AND CONCLUSIONS

Although preload assessment can be obtained with fair accuracy, the clinical utility of volume responsiveness-guided fluid therapy still needs to be demonstrated. Indeed, it is still not clear whether any form of monitoring-guided fluid therapy improves survival.

Why protect the right ventricle in patients with acute respiratory distress syndrome?

Even a slight increase in pulmonary vascular resistance can overload a normal right ventricle, which ejects blood through a low-pressure circuit. In a clinical setting, a persistent increase in pulmonary vascular resistance produces acute cor pulmonale. From an echocardiographic point of view, may be defined as the combination of a paradoxical septal motion, reflecting systolic overload, with right ventricular enlargement, reflecting diastolic overload. In patients with acute respiratory distress syndrome, this complication reflects the severity of the pulmonary disease involving the microvasculature but may also be caused or exacerbated by an aggressive ventilatory strategy. In the past, conventional respiratory support used in acute respiratory distress syndrome to obtain normocapnia was associated with a poor prognosis and a high frequency of acute cor pulmonale, suggesting some relation between the two findings. This prognosis has greatly improved with protective ventilation. At the same time, the incidence of acute cor pulmonale has diminished in acute respiratory distress syndrome, and the prognosis of this specific complication has also improved, suggesting that the right ventricle may develop some adaptation against persistent overload. Past lessons, however, have taught us that this potential may be limited and lead us to recommend right ventricular protection during mechanical ventilation.

Mathematical coupling does not explain the relationship between right ventricular end-diastolic volume and cardiac output

OBJECTIVE

To evaluate the clinical significance of mathematical coupling on the correlation between cardiac output and right ventricular end-diastolic volume (RVEDV) through measurement of cardiac output by two independent techniques.

DESIGN

Prospective, observational study.

SETTING

Surgical intensive care unit in a level 1 trauma center.

PATIENTS

Twenty-eight critically ill surgical patients who received mechanical ventilation and hemodynamic monitoring with a pulmonary artery catheter.

INTERVENTIONS

A pulmonary artery catheter designed to measure right ventricular ejection fraction (RVEF) and cardiac output by the intermittent bolus thermodilution (TDCO) method and continuous cardiac output by the pulsed thermal energy technique was placed. A computerized data logger was used to collect data simultaneously from the RVEF/TDCO system and the continuous cardiac output system.

MEASUREMENTS AND MAIN RESULTS

Two hundred forty-nine data sets from 28 patients were compared. There is statistical correlation between TDCO and continuous cardiac output measurements (r = 0.95, p < 0.0001) with an acceptable bias (-0.11 L/min) and precision (+/-0.74 L/min). The correlation was maintained over a wide range of cardiac outputs (2.3-17.8 L/min). There is a high degree of correlation between RVEDV and both TDCO (r = 0.72, p < 0.0001) and independently measured continuous cardiac output (r = 0.68, p < 0.0001). These correlation coefficients are not statistically different (p = 0.15).

CONCLUSIONS

The continuous cardiac output technique accurately approximates cardiac output measured by the TDCO method. RVEDV calculated from TDCO correlates well with both TDCO and independently measured continuous cardiac output. Because random measurement errors of the two techniques differ, mathematical coupling alone does not explain the correlation between RVEDV estimates of preload and cardiac output.

Myocardial dysfunction associated with proinflammatory cytokines after esophageal resection

Proinflammatory cytokines have been implicated in mediating myocardial dysfunction associated with major surgery. We investigated the profile of proinflammatory cytokines and the association of cytokine levels with myocardial function after esophagectomy. We studied 12 patients who underwent subtotal esophagectomy. One patient died of multiple organ failure. This patient had the largest interleukin-6 (IL-6) level of all the subjects. IL-6 levels increased from 14.9 +/- 8.7 pg/mL to 498.4 +/- 294.3 pg/mL (P < 0.05) at 6 h postoperatively. Interleukin-8 (IL-8) levels also significantly increased postoperatively. Right ventricular ejection fraction (RVEF) decreased from 44% +/- 1% to 36% +/- 2% (P < 0.05) and 37% +/- 2% (P < 0.05) at 6 h and 12 h postoperatively. Stroke volume index (SVI) decreased significantly at the end of operation and at 6 h and 12 h postoperatively. The changes of RVEF and SVI showed an independent negative correlation with the IL-6 level (r = -0.70, P < 0.001 and r = -0.62, P < 0.001, respectively). In contrast, the change of RVEF and SVI was not correlated with the IL-8 level. Esophagectomy is associated with transient depression of myocardial function. IL-6 may contribute to this postoperative myocardial dysfunction.

IMPLICATIONS

We examined the association between myocardial function and proinflammatory cytokines after esophagectomy. Interleukin-6 may be the cytokine that most sensitively reflects the postoperative myocardial dysfunction.

Effect of the mechanical ventilatory cycle on thermodilution right ventricular volumes and cardiac output

The purpose of this study was to evaluate right ventricular (RV) loading and cardiac output changes, by using the thermodilution technique, during the mechanical ventilatory cycle. Fifteen critically ill patients on mechanical ventilation, with 5 cmH(2)O of positive end-expiratory pressure, mean respiratory frequency of 18 breaths/min, and mean tidal volume of 708 ml, were studied with help of a rapid-response thermistor RV ejection fraction pulmonary artery catheter, allowing 5-ml room-temperature 5% isotonic dextrose thermodilution measurements of cardiac index (CI), stroke volume (SV) index, RV ejection fraction (RVEF), RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) indexes at 10% intervals of the mechanical ventilatory cycle. The ventilatory modulation of CI and RV volumes varied from patient to patient, and the interindividual variability was greater for the latter variables. Within patients also, RV volumes were modulated more by the ventilatory cycle than CI and SV index. Around a mean value of 3.95 +/- 1.18 l. min(-1). m(-2) (= 100%), CI varied from 87.3 +/- 5.2 (minimum) to 114.3 +/- 5.1% (maximum), and RVESV index varied between 61.5 +/- 17.8 and 149.3 +/- 34.1% of mean 55.1 +/- 17.9 ml/m(2) during the ventilatory cycle. The variations in the cycle exceeded the measurement error even though the latter was greater for RVEF and volumes than for CI and SV index. For mean values, there was an inspiratory decrease in RVEF and increase in RVESV, whereas a rise in RVEDV largely prevented a fall in SV index. We conclude that cyclic RV afterloading necessitates multiple thermodilution measurements equally spaced in the ventilatory cycle for reliable assessment of RV performance during mechanical ventilation of patients.

Anesthetic considerations for patients with severe emphysematous lung disease

The pathophysiology, medical and surgical management of emphysema have been reviewed as a foundation to the physiological goals and principles of anesthetic management of patients with emphysema. An understanding of the cardiovascular and respiratory consequences of emphysema combined with anesthesia, PPV, and thoracic surgery is essential to achieving the challenging physiological goals of providing anesthesia, positive pressure and one-lung ventilation, and postoperative analgesia in a manner consistent with rapid postoperative extubation, hemodynamic stability, adequate gas exchange, and minimal barotrauma for this population of patients.

Right atrial pressure predicts hemodynamic response to apneic positive airway pressure

OBJECTIVE

To evaluate if the preexistant filling state, assessed by right atrial pressure (RAP), pulmonary artery occlusion pressure (PAOP), and right ventricular end-diastolic volume index (EDVI), would define the subsequent hemodynamic effects of increases in airway pressure (Paw).

DESIGN

Prospective open clinical study.

SETTING

Postoperative intensive care unit, university hospital.

PATIENTS

Twenty-two consecutive ventilator-dependent patients with mild to severe acute lung injury with Murray scores (scoring infiltrates on chest radiograph, oxygenation index, lung compliance, and the level of positive end-expiratory pressure) ranging from 0.5 to 3.0 without history of preexisting cardiopulmonary disease.

INTERVENTIONS

Paw varied during apnea from 0 to 10, 20, and 30 cm H2O using inspiratory hold maneuvers of 15 secs.

MEASUREMENTS AND MAIN RESULTS

Cardiac index and right ventricular ejection fraction were measured by the thermodilution technique. We made measurements in triplicate using manual injection of iced saline. Right ventricular volumes were calculated. Increasing Paw induced variable changes in cardiac index among subjects (+6% to -43% change from baseline 0 cm H2O Paw values), which correlated with percentage changes in both stroke index (r2 = .89) and right ventricular EDVI (r2 = .75), whereas heart rate and right ventricular ejection fraction did not change. The change in cardiac index from 0 to 30 cm H2O Paw correlated with baseline values for RAP, PAOP, and right ventricular EDVI (r2 = .68, .43, and .34, respectively, p < 0.01). Increases in RAP correlated with lung compliance if baseline RAP was >10 mm Hg but did not if it was < or =10 mm Hg. Similarly, patients with baseline RAP < or =10 mm Hg had a greater decrease in cardiac index than patients with a RAP >10 mm Hg (for 30 cm H2O Paw: -30% +/- 9% vs. -8% +/- 7%, p < .01).

CONCLUSIONS

Apneic positive Paw decreased cardiac output mainly by reducing venous return. From the investigated filling variables, RAP was most sensitive in predicting the hemodynamic response, followed by PAOP and right ventricular EDVI. Patients with RAP < or =10 mm Hg, if subjected to aggressive positive pressure ventilation, are at risk of hemodynamic deterioration and organ hypoperfusion.

Effects of continuous positive airway pressure on cardiac volumes in patients with ischemic and dilated cardiomyopathy

The effects of continuous positive airway pressure (CPAP) on left (LV) and right ventricular (RV) volumes in patients with congestive heart failure (CHF) have not been studied. We hypothesized that CPAP would cause greater reductions in cardiac volumes in CHF patients with idiopathic dilated cardiomyopathy (IDC) than in those with ischemic cardiomyopathy (IsC), because their ventricles are more compliant. The effects of a 30-min CPAP application at 10 cm H(2)O on RV and LV end-diastolic (EDV) and end-systolic volumes (ESV), determined by radionuclide angiography, were therefore tested in 22 patients with CHF due to IsC (n = 13) or IDC (n = 9). CPAP-induced reductions in LVEDV, LVESV, RVEDV, and RVESV were significantly greater (p < 0.05) in the IDC than in the IsC group. Whereas in the IsC group CPAP caused no significant changes in LV or RV volumes, in the IDC group it induced significant reductions in RVEDV (527 +/- 77 ml to 354 +/- 50 ml, p = 0.03) and RVESV (400 +/- 78 ml to 272 +/- 54 ml, p = 0.04) that were greater than any reductions in LVEDV and LVESV. We conclude that CPAP causes greater short-term reductions in RV and LV volumes in CHF patients with IDC than in those with IsC, and that among patients with IDC, CPAP causes greater reductions in RV than in LV volumes.

Cyclic changes in right ventricular output impedance during mechanical ventilation

In a context such as acute respiratory distress syndrome, where optimum tidal volume and airway pressure levels are debated, the present study was designed to differentiate the right ventricular (RV) consequences of increasing lung volume from those secondary to increasing airway pressure during tidal ventilation. The study was conducted by combined two-dimensional echocardiographic and Doppler studies in 10 patients requiring mechanical ventilation in the controlled mode because of acute respiratory failure. Continuous monitoring of airway pressure on echocardiographic and Doppler recordings provided accurate timing of each cardiac event during the respiratory cycle, with particular attention being paid to end-expiratory and end-inspiratory atrial diameters, RV dimensions, and pulmonary artery and tricuspid flow estimated by the velocity-time integral (PA(VTI) and T(VTI), respectively). At baseline, lung inflation during the inspiratory phase of mechanical ventilation produced a drop in PA(VTI) from 14.3 +/- 2.6 cm at end expiration to 11.3 +/- 2.1 cm at end inspiration. This drop occurred without reduction in right atrial diameter or in RV diastolic dimensions. It was not preceded but was followed by a decrease in T(VTI), thus confirming an increase in RV outflow impedance. Manipulation of tidal volume without changing airway pressure and manipulation of airway pressure without changing tidal volume demonstrated that tidal volume, but not airway pressure, was the main determinant factor of RV afterloading during mechanical ventilation.

Pulmonary artery catheterization and esophageal doppler monitoring in the ICU

The clinical assessment of cardiac performance and ventricular preload is notoriously unreliable in critically ill patients. Consequently, a number of technologies have been developed to provide the clinician with indexes of cardiovascular function to assist in therapeutic decision making. Foremost among these is the pulmonary artery catheter (PAC). Indeed, the PAC has largely shaped the practice of modern critical care. Yet, the information provided by the PAC is largely misunderstood, and its efficacy is never proven. Recently, continuous esophageal Doppler monitoring has emerged as an alternative to pulmonary artery catheterization. This paper evaluates the clinical utility of the PAC and esophageal Doppler monitoring in assessing the hemodynamic status of ICU patients.

Preload assessment in patients with an open abdomen

BACKGROUND

Intra-abdominal hypertension and abdominal compartment syndrome cause significant morbidity and mortality in surgical and trauma patients. Maintenance of intravascular preload and use of open abdomen techniques are essential. The accuracy of pulmonary artery occlusion pressure (PAOP) and central venous pressure (CVP) in patients with intra-abdominal hypertension has been questioned.

METHODS

Twenty surgical and trauma patients with intra-abdominal hypertension requiring open abdominal decompression were monitored using volumetric thermodilution pulmonary artery catheters. Hemodynamic, oxygenation, inspiratory, and intravesicular pressure measurements were collected prospectively. PAOP, CVP, and right ventricular end-diastolic volume index (RVEDVI) were compared as estimates of preload status.

RESULTS

Multiple regression analysis demonstrated that cardiac index correlated significantly better with RVEDVI (r = 0.69) than with PAOP (r = -0.27) or CVP (r = -0.28) during resuscitation after open abdominal decompression (p < 0.0001).

CONCLUSION

RVEDVI is superior to PAOP and CVP as an estimate of preload status in patients with an open abdomen.

Continuous cardiac output and mixed venous oxygen saturation monitoring

Continuous assessment of cardiac output and SVO2 in the critically ill may be helpful in both the monitoring variations in the patient's cardiovascular state and in determining the efficacy of therapy. Commercially available continuous cardiac output (CCO) monitoring systems are based on the pulsed warm thermodilution technique. In vitro validation studies have demonstrated that this method provides higher accuracy and greater resistance to thermal noise than standard bolus thermodilution techniques. Numerous clinical studies comparing bolus with continuous thermodilution techniques have shown this technique similarly accurate to track each other and to have negligible bias between them. The comparison between continuous thermal and other cardiac output methods also demonstrates good precision of the continuous thermal technique. Accuracy of continuous oximetry monitoring using reflectance oximetry via fiberoptics has been assessed both in vitro and in vivo. Most of the studies testing agreement between continuous SVO2 measurements and pulmonary arterial blood samples measured by standard oximetry have shown good correlation. Continuous SVO2 monitoring is often used in the management of critically ill patients. The most recently designed pulmonary artery catheters are now able to simultaneously measure either SVO2 and CCO or SVO2 and right ventricular ejection fraction. This ability to view simultaneous trends of SVO2 and right ventricular performance parameters will probably allow the clinician to graphically see the impact of volume loading or inotropic therapy over time, as well as the influence of multiple factors, including right ventricular dysfunction, on SVO2. However, the cost-effectiveness of new pulmonary artery catheters application remains still questionable because no established utility or therapeutic guidelines are available.

Right ventricular end-diastolic volume index as a predictor of preload status in patients on positive end-expiratory pressure

OBJECTIVE

To evaluate the clinical utility of right ventricular end-diastolic volume index (RVEDVI) and pulmonary artery occlusion pressure (PAOP) as measures of preload status in patients with acute respiratory failure receiving treatment with positive end-expiratory pressure.

DESIGN

Prospective, cohort study.

SETTING

Surgical intensive care unit in a Level I trauma center/university hospital.

PATIENTS

Sixty-four critically ill surgical patients with acute respiratory failure.

INTERVENTIONS

All patients were treated for acute respiratory failure with titrated levels of positive end-expiratory pressure (PEEP) with the goal of increasing arterial oxygen saturation to > or =0.92, reducing FIO2 to <0.5, and reducing intrapulmonary shunt to < or =0.2. Serial determinations of RVEDVI, PAOP, and cardiac index (CI) were recorded.

MEASUREMENTS AND MAIN RESULTS

Two hundred-fifty sets of hemodynamic variables were measured in 64 patients. The level of PEEP ranged from 5 to 50 cm H2O (mean 12+/-9 [SD] cm H2O). At all levels of PEEP, CI correlated significantly better with RVEDVI than with PAOP. At levels of PEEP > or =15 cm H2O, CI was inversely correlated with PAOP, but remained positively correlated with RVEDVI.

CONCLUSIONS

CI correlates significantly better with RVEDVI than PAOP at all levels of PEEP up to 50 cm H2O. RVEDVI is a more reliable predictor of volume depletion and preload recruitable increases in CI, especially in patients receiving higher levels of PEEP where PAOP is difficult to interpret.

Does positive end-expiratory pressure ventilation improve left ventricular function? A comparative study by transesophageal echocardiography in cardiac and noncardiac patients

STUDY OBJECTIVES

Positive end-expiratory pressure (PEEP) has been proposed to improve cardiac output in patients with left ventricular (LV) dysfunction. This study was designed to compare quantitative global and regional LV performance in response to PEEP in patients with normal and poor LV function.

DESIGN

A prospective clinical trial.

SETTING

Adult medical ICU in a university hospital.

PATIENTS

Twelve critically ill patients requiring respiratory support and divided into two groups according to baseline transesophageal echocardiographic (TEE) measurements: normal LV dimensions and fractional area of contraction (FAC=61+/-5%) (n=7) and dilated cardiomyopathy with reduced FAC (21+/-1%) (n=5).

MEASUREMENTS AND RESULTS

All patients were studied when two successive levels of PEEP (best PEEP as the highest value of respiratory compliance and high PEEP as best PEEP+10 cm H2O) were applied. Global systolic LV performance and quantitative regional wall motion analysis performed by the centerline method were assessed on the TEE transgastric short-axis view. End-systolic wall stress (ESWS) was used as a reliable indication of LV afterload. PEEP reduced LV dimensions asymmetrically in both groups of patients and septolateral diameter significantly decreased without affecting global LV systolic performance. Additionally, high PEEP produced a significant impairment in septal kinetics as evidenced by the centerline method. High PEEP also decreased ESWS for all patients (-27% in normal group and -23% in cardiac group, p<0.05) without significant improvement in global systolic LV performance (FAC: +2% in normal group and +0% in cardiac group; not significant).

CONCLUSIONS

PEEP cannot be recommended routinely to improve LV performance in patients with severe dilated cardiomyopathy.

Haemodynamic response during initiation of non-invasive positive pressure ventilation in COPD patients with acute ventilatory failure

The aim of this study was to check non-invasively the acute haemodynamic effects of non-invasive positive pressure ventilation (NPPV) initiation in patients with chronic obstructive pulmonary disease (COPD) and acute ventilatory failure (AVF). Nineteen consecutive COPD patients with AVF were evaluated clinically and echocardiographically during spontaneous breathing with O2 supplementation and during NPPV plus O2. NPPV was administered with a scheduled inspiratory pressure of 15 cmH2O and an expiratory pressure of 4 cmH2O, via facial mask. Arterial blood gas improved significantly (pH and PaCO2; P < 0.001) during NPPV administration in all patients; none had hypotension or acute arrhythmia. Doppler echocardiographic evaluation was feasible in most of the patients (16/18). With reference to baseline values, no significant changes in pulmonary artery pressures and cardiac output (CO) were observed by Doppler echocardiography in most patients. Only four patients (21%) showed a significant reduction (> 15%) of CO during NPPV. No correlation was found between decreased CO and baseline data, but three patients showing CO reduction had poor tolerance to mask ventilation and did not improve respiratory rate during NPPV. It was concluded that the initiation of NPPV by facial mask does not alter haemodynamics acutely in most COPD patients with AVF, but individual patients may experience reduction in CO in spite of adequate oxygen saturation levels. This suggests that caution should be used when applying pre-determined and fixed pressures during NPPV. Monitoring haemodynamics by Doppler echocardiography may be useful for early detection of haemodynamic alterations due to NPPV application in patients with AVF.

Measurement of right ventricular performance during apnea in patients with acute lung injury

BACKGROUND

Mechanical ventilation resulted in increased, decreased or unchanged end-diastolic volumes together with either profoundly decreased or unchanged right ventricular ejection fraction (RVEF). The goal of our study was, therefore, to evaluate the effects of positive end-expiratory pressure on measurements of RVEF performed during apneic periods with different levels of positive end-expiratory pressure.

METHODS

Fifteen consecutive patients suffering from acute lung injury after major surgery or trauma were included. Measurements were performed during 15 seconds of apnea at airway pressure levels of 0 (baseline), 10, 20, and 30 cm H2O. Cardiac output and RVEF were determined using the thermodilution technique.

RESULTS

Lung inflation to an airway pressure of 30 cm H2O caused a 22 +/- 14% decrease of cardiac output resulting from a 20 +/- 14% decrease of stroke volume index. The decrease of stroke volume index was induced by a 17 +/- 11% decrease of right ventricular end-diastolic volume index, while RVEF remained virtually unchanged (0.49 +/- 0.10 vs. 0.47 +/- 0.12 at 0 and 30 cm H2O, respectively). Relative changes of cardiac output were closely correlated with changes of right ventricular end-diastolic volume index (p < 0.05, r2 = 0.78).

CONCLUSIONS

Right ventricular systolic function was well maintained despite substantially decreased end-diastolic volumes. In our study, during apneic conditions, higher levels of positive end-expiratory pressure did not worsen RVEF in patients with acute lung injury. The proposed technique of apneic lung inflation may serve as an alternative approach to obtain comparable measurements of RV function in patients with acute lung injury.

Right ventricular function before and after percutaneous balloon mitral valvuloplasty

Aim of this study was to evaluate right ventricular performance in patients with mitral stenosis and its modification by balloon valvuloplasty. Right ventricular volumes of 24 patients with postrheumatic mitral stenosis were determined by thermodilution 1 or 2 days before and 1 or 2 days after valvuloplasty. Right ventricular ejection fraction at rest was 43 (36-47)% (median and interquartile range). Right ventricular end-diastolic volume was 100 (86-119) ml/m2. Supine bicycle exercise (50 Watt) reduced right ventricular ejection fraction to 30 (29-37)% (P < 0.0001) and increased right ventricular end-diastolic volume to 124 (112-141) ml/m2 (P < 0.0001). At rest, right ventricular ejection fraction correlated inversely with pulmonary vascular resistance (r = -0.64, P < 0.0001), while no significant correlation with mitral valve area was found. Valvuloplasty increased right ventricular ejection fraction at rest to 48 (44-50)% (P < 0.005), and during exercise to 42 (38-45)% (P < 0.0001). This improvement of right ventricular ejection fraction correlated inversely with the value of this parameter before valvuloplasty (r = -0.88, P < 0.0001) and with the gain in stroke volume (r = 0.57, P < 0.01). The right ventricular function curve, disturbed before commissurotomy, was reestablished by the procedure. In conclusion, at the here investigated stage of mitral stenosis right ventricular function is reversibly impaired. This is predominantly caused by the hemodynamic consequences of the valvular defect and not by an impairment of right ventricular myocardial function.

The new pulmonary arterial catheters. Right ventricular ejection fraction and continuous cardiac output

The flow-directed pulmonary artery catheter is the mainstay of hemodynamic monitoring in critically ill and injured patients. During its 25-year history, the catheter has been modified to measure mixed venous oxygen saturation, right ventricular ejection fraction, and recently, continual thermodilution cardiac output. The clinical application of the new generations of pulmonary artery catheters is reviewed in this article.

Transesophageal echocardiography

This article presents an overview of the benefits and efficacy of transesophageal echocardiography (TEE) in the critically ill patient. The echocardiographic evaluation of ventricular function both regional and global, is discussed with special emphasis on ischemic heart disease; assessment of preload, interrogation of valvular heart disease (prosthetic and native) and its complications; endocarditis and its complications; intracardiac and extracardiac masses, including pulmonary embolism; aortic diseases (e.g., aneurysan, dissection, and traumatic tears); evaluation of patent foramen ovale and its association with central and peripheral embolic events; advancements in computer technology; and finally, the effect of TEE on critical care.

Pulmonary vascular resistance and right ventricular function in morbid obesity in relation to gastric bypass surgery

STUDY OBJECTIVE

To investigate right ventricular function (RVF) during gastric bypass surgery in morbidly obese patients. To study the influence of obstructive sleep apnea syndrome on hemodynamics and RVF as a preoperative evaluation in morbidly obese patients.

DESIGN

Prospective study.

SETTING

Surgical patients at a university hospital.

PATIENTS

14 morbidly obese patients undergoing gastric bypass surgery.

INTERVENTIONS

Hemodynamic changes and RVF were investigated using a thermodilution ejection fraction volumetric catheter and the REF-1 computer.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic parameters and RVF were measured: (1) before induction of anesthesia, awake, (2) after induction of anesthesia, (3) after opening the abdomen, and (4) after closing the abdomen. Esophageal pressure was measured in the midesophagus after induction of anesthesia with a camino catheter and its device. Morbidly obese patients with obstructive sleep apnea syndrome had significantly lower PaO2, higher PaCO2, and higher pulmonary artery (PA) pressure and pulmonary vascular resistance (PVR) compared with patients without sleep apnea (p < 0.05). However, there were no significant differences in heart rate, mean blood pressure, pulmonary capillary wedge pressure (PCWP), right ventricular ejection fraction (RVEF), and right ventricular end-diastolic volume. During gastric bypass procedure, PA pressure, PCWP, and PVR decreased significantly after opening the abdomen (p < 0.05). There were no significant changes in RVEF and cardiac index during gastric bypass procedure.

CONCLUSION

The presence of chronic hypoxemia and hypercarbia in our morbidly obese patients with obstructive sleep apnea syndrome while awake, causes significant increases in PA pressure and PVR. We also demonstrated that RVEF did not change significantly during gastric bypass procedure despite significant decreases in PA pressure, PCWP, and PVR after opening the abdomen. This decrease in PA pressure and PVR may be caused by decreases in pleural pressure reflected by a concomitant decrease in esophageal pressure.

The effects of positive end-expiratory pressure of intrapulmonary shunt and ventilatory deadspace in nonhypoxic trauma patients

Controversy exists regarding the routine use of positive end-expiratory pressure (PEEP) in mechanically ventilated patients. We hypothesized that nonhypoxic patients receiving 5-cm H2O PEEP would have improved shunt and PaO2/F10(2) ratios (P/F), without an increased dead space to tidal volume ratio (VD/VT) versus patients receiving no PEEP. Forty-four trauma patients were randomized to receive 5-cm H2O PEEP (PEEP) or 0-cm H2O PEEP (ZEEP). Shunt VD/VT and P/F were measured at 0, 12, 24, 36, and 48 hours after intubation and after extubation. PEEP and ZEEP comparisons used Student's t test and the General Linear Models procedure. Shunt was significantly increased at t = 0 and at extubation in the PEEP group. At extubation, the PEEP group demonstrated significantly higher VD/VT and poorer P/F ratios. After correction for baseline values, no statistically significant differences were noted in spite of a trend toward worsening pulmonary function in all measured parameters. These results suggest that routine use of 5-cm H2O PEEP in mechanical ventilated trauma patients is not necessary.