Right ventricular function and positive pressure ventilation in clinical practice: from hemodynamic subsets to respirator settings

[Perioperative management of patients with systemic scleroderma]

Systemic sclerosis (SSc) is an auto-immune disease characterized by vasculopathy and the combination of microangiopathy and tissue collagen deposit leading to skin, digestive, pulmonary, myocardial and renal injuries. These repercussions could be challenging for anesthesiologists and associated with difficulties in airway management, and occurrence of congestive right heart failure or acute kidney crisis. The aim of this review is to review the physiopathology and the progression of the SSc, as well as to provide a strategy of perioperative management of these patients.

Use of systolic pressure variation to predict the cardiovascular response to mini-fluid challenge in anaesthetised dogs

Systolic pressure variation (SPV), the maximum variation in systolic pressure values following a single positive pressure breath delivered by controlled mechanical ventilation (CMV), is highly correlated with volaemia in dogs. The aim of this study was to determine an SPV value that would indicate when fluid administration would be beneficial in clinical practice. Twenty-six client-owned dogs were anaesthetised, following which CMV with a peak inspiratory pressure (PIP) of 8 cmH2O was applied. After SPV measurement and recording of heart rate (HR) and blood pressure (BP), 3 mL/kg fluid were administered, then HR and BP were recorded again. Dogs exhibiting a 10% decrease in HR and/or an increase in BP were defined as responders, and their SPV pre-bolus was analysed retrospectively. SPV values > 4 mmHg or >4.5% predicted haemodynamic improvement in dogs with normal cardiovascular function, with a sensitivity of 90% and a specificity of 87%. The area under the curve receiver operating characteristic value for SPV was 0.931 mmHg (95% confidence interval, CI, 0.76-0.99 mmHg) and 0.944% (95% CI 0.78-0.99%). It is proposed that SPV values > 4.5% in dogs with a normal cardiovascular function, anaesthetised with isoflurane in oxygen and air, and on CMV (PIP 8 cmH2O), can be used to predict a cardiovascular response (>10% increase in mean arterial BP and/or >10% decrease in heart rate).

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Intensive care management of pulmonary hypertension

Pulmonary hypertension (PH) in the Intensive Care Unit (ICU) may be due to preexisting pulmonary vascular lung disease, liver disease, or cardiac diseases. PH also may be caused by critical illnesses, such as acute respiratory distress syndrome (ARDS), acute left ventricular dysfunction and pulmonary embolism, or may occur after cardiac or thoracic surgery.

Regardless of the underlying cause of PH, the final common pathway for hemodynamic deterioration and death is RV failure, which is the most challenging aspect of patient management. Therapy is thus aimed at acutely relieving RV overload by decreasing PVR and reversing RV failure with pulmonary vasodilators and inotropes.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Perioperative management in patients with pulmonary hypertension

Patients with pulmonary hypertension (PH) are being encountered more commonly in the perioperative period and this trend is likely to increase as improvements in the recognition, management, and treatment of the disease continue to occur. Management of these patients is challenging due to their tenuous hemodynamic status. Recent advances in the understanding of the patho-physiology, risk factors, monitoring, and treatment of the disease provide an opportunity to reduce the morbidity and mortality associated with PH in the peri-operative period. Management of these patients requires a multi-disciplinary approach and meticulous care that is best provided in centers with vast experience in PH.

In this review, we provide a detailed discussion about oerioperative strategies in PH patients, and give evidence-based recommendations, when applicable.

Acute right heart syndrome: Rescue treatment with inhaled nitric oxide

Acute right heart syndrome is a common occurrence in intensive care units and is associated with a poor prognosis. There is lack of understanding of the involved pathophysiology, standard diagnostic protocols and treatment guidelines. Management goals include ensuring adequate right ventricle (RV) filling, maximizing RV contraction and reducing RV afterload. We describe a 39-year-old female with acute decompensated right heart failure secondary to multiple causes. She was managed with inhaled nitric oxide. Her condition improved, which was evident by a decrease in her pulmonary artery systolic pressure on serial echocardiography, decreased requirement of vasopressors and successful weaning from the ventilator.

Cardiogenic Shock and the ICU Patient

Cardiogenic shock is one of the most important complications of acute myocardial infarction (MI) and acute left ventricular failure (LVF). It threatens the life of 5–10% of patients with ST-segment elevation myocardial infarction (STEMI) particularly in the presence of inappropriately low peripheral vascular resistance. Cardiogenic shock results in poor tissue perfusion, end-organ damage and carries a high mortality risk. The goal of therapy is to prevent end-organ dysfunction and severe metabolic derangement by raising mean arterial blood pressure, which is achieved with the use of inotropes and vasopressors, often at the expense of tachycardia, elevated myocardial oxygen consumption and extended myocardial ischaemia. Current therapeutic approaches include early coronary artery revascularisation (which has significantly improved the survival rate), fluid resuscitation, inotropic support and mechanical circulatory support using intra-aortic balloon pumps or ventricular assist devices. In this article, we review the pathophysiology, diagnosis and management of cardiogenic shock.

Effects of fluid load on cardiovascular function during stepwise lung recruitment manoeuvre in healthy dogs

The aim of this study was to evaluate the effects of a stepwise lung recruitment manoeuvre (RM) on cardiac output (CO) in mechanically ventilated dogs, with or without a previous fluid load. Eight healthy adult Beagle dogs were enrolled in a prospective crossover study. Following sedation with dexmedetomidine and methadone, anaesthesia was induced with propofol and maintained with isoflurane. CO (thermodilution method) and direct arterial blood pressure were monitored. The dogs were mechanically ventilated in a volume-controlled mode (tidal volume, VT = 10 mL/kg; positive end-expiratory pressure [PEEP] = 0 cm H2O) until normocapnia was achieved (end tidal CO2 35-45 mmHg). The RM was then performed in a pressure-controlled mode, with progressive increases of the PEEP and end-inspiratory pressure of 5 cm H2O, until 15 cm H2O and 30 cm H2O were reached, respectively. After the RM, the ventilatory mode was returned to volume-control, and the PEEP was sequentially decreased to 10, 5 and 0 cm H2O. Baseline ventilation was maintained for 30 min. Next, 10 mL/kg of lactated Ringer's solution was administered within 10 min, prior to a second RM. The CO was determined before each RM (baseline) and at each pressure step. A repeated measures ANOVA test was used to compare data. Compared to baseline, CO decreased during the RM in both groups. However, there was a significantly higher CO during the second RM at the highest pressure step (P<0.05) and during all decreasing pressure steps (P<0.05). In conclusion, a previous crystalloid fluid load could reduce the impact of a RM on CO in healthy dogs.

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.

Evaluation of the right ventricular ejection fraction during classic orthotopic liver transplantation without venovenous bypass

BACKGROUND

Right ventricular (RV) function is sensitive to changes in cardiac loading conditions, and RV dysfunction may contribute to hemodynamic instability during orthotopic liver transplantation (OLT). Thus, we evaluated RV function and its role in hemodynamic instability during classic OLT without venovenous bypass (VVB).

METHODS

Thirty patients undergoing classic OLT without VVB were studied. Right ventricular ejection fraction (RVEF) was measured using a modified pulmonary artery catheter. Hemodynamic data were recorded at pre-determined time points: T0, baseline; T1-T3: 5, 15, and 30 min after clamping; T4-T7: 5, 15, 30, and 120 min after reperfusion; T8 and T9: 24 and 48 h after surgery.

RESULTS

The baseline RVEF was lower than normal value. RVEF decreased significantly from T1 to T4 and returned to baseline beginning at T5. At 24 and 48 h after surgery, RVEF was higher than baseline value. RVEF was correlated with stroke volume index and post-reperfusion syndrome during OLT. Compared to the low MELDs group, RVEF in the high MELDs group was lower at T1, T2, and T4.

CONCLUSIONS

Right ventricular function was compromised during the anhepatic and early reperfusion stages in patients undergoing classic OLT without VVB, particularly in the high MELD score patients. Close monitoring of RV function in these patients should be considered.

Pericardial disease--anatomy and function

Imaging of patients with suspected or known pericardial disease remains challenging. Echocardiography is the first-line investigation for pericardial disease but it has specific limitations in terms of its abilities to visualise the pericardium fully and to identify extracardiac pathology. Cardiac cross-sectional imaging by both MRI and CT has developed significantly and now has an important role in the investigation of pericardial disease. This article examines the appearances of both healthy and diseased pericardium using CT and MRI. The typical imaging findings across a wide range of conditions are illustrated and the roles of CT and MRI are reviewed. The relative merits and weaknesses of each modality are explored and the specific functional techniques that are available are introduced.

Hemodynamic consequences of auto-PEEP

Auto-positive end-expiratory pressure (PEEP) is a common but frequently unrecognized problem in critically ill patients. It has important physiologic consequences and can cause shock and cardiac arrest. Treatment consists of relieving expiratory airflow obstruction and reducing minute ventilation delivered by positive pressure ventilation. Sedation and fluid management are important adjunctive therapies. This analytic review discusses the prevalence, pathophysiology, and hemodynamic consequences of auto-PEEP and an approach to its treatment.

Respiratory physiology and the impact of different modes of ventilation on the photoplethysmographic waveform

The photoplethysmographic waveform sits at the core of the most used, and arguably the most important, clinical monitor, the pulse oximeter. Interestingly, the pulse oximeter was discovered while examining an artifact during the development of a noninvasive cardiac output monitor. This article will explore the response of the pulse oximeter waveform to various modes of ventilation. Modern digital signal processing is allowing for a re-examination of this ubiquitous signal. The effect of ventilation on the photoplethysmographic waveform has long been thought of as a source of artifact. The primary goal of this article is to improve the understanding of the underlying physiology responsible for the observed phenomena, thereby encouraging the utilization of this understanding to develop new methods of patient monitoring. The reader will be presented with a review of respiratory physiology followed by numerous examples of the impact of ventilation on the photoplethysmographic waveform.

Feasibility of right ventricular longitudinal systolic function evaluation with transthoracic echocardiographic indices derived from tricuspid annular motion: a preliminary study in acute respiratory distress syndrome

INTRODUCTION

Assessment of right ventricular (RV) function in patients with acute respiratory distress syndrome (ARDS) remains challenging. Transthoracic echocardiographic (TTE) indices based on longitudinal systolic RV function are now considered as a reliable evaluation of RV function. We investigated feasibility of two methods in ARDS patients.

METHODS

Prospective observational study. TTE was performed after 12-36 hours of mechanical ventilation. Feasibility of tricuspid annular motion (S(t) ), tricuspid annular plane systolic excursion (TAPSE) was compared to usual two-dimensional (2D) study: fractional area change (RV(FAC) ) and ratio of right to left ventricular end-diastolic area (RVEDA/LVEDA).

RESULTS

Fifty patients were investigated, with TTE possible in all but two patients. Feasibility was 62% for RV(FAC), 72% for RVEDA/LVEDA, and 96% for TAPSE and S(t). RV dilatation (RVEDA/LVEDA ≥ 0.60) was found in 16 patients, including 4 patients with acute cor pulmonale. A longitudinal RV dysfunction (TAPSE < 12 mm or S(t) < 11.5 cm/sec) was suspected in 30% of patients. Relation between both longitudinal indices was modest (r(2) = 0.36, P < 0.001). TAPSE (but not S(t) ) was found poorly related to RV(FAC) (r(2) = 0.27, P = 0.03). Both indices were related to LV function (S(t) : r(2) = 0.27, TAPSE: r(2) = 0.17, both P < 0.05).

CONCLUSION

Despite a superior feasibility than 2D study, our results suggest that both indices may not bring identical information to echo study. TAPSE may be more adapted to ICU use than S(t) . Both should be further investigated in terms of analysis of RV function and ventricular interdependence. Their relations with LV function may limit their use as sole markers of RV function in this population.

Cardiogenic shock in ACS. Part 1: prediction, presentation and medical therapy

Ischemic cardiogenic shock is a complex, self-perpetuating pathological process that frequently causes death irrespective of medical therapy. Early definition of coronary anatomy is a pivotal step towards survival. Those destined to develop shock are likely to have three-vessel or left main stem disease with previously impaired left ventricular function. Early reperfusion of the occluded artery can limit infarct size, but ischemia-reperfusion injury or the 'no-reflow' phenomenon can preclude improvement in myocardial contractility. Emergence of shock depends upon the volume of ischemic myocardium, stroke volume, and peripheral vascular resistance. If cytokine release triggers the systemic inflammatory response, systemic vascular resistance falls and inadequate coronary perfusion pressure heralds the downward spiral. Survival depends on early recognition of shock, followed by aggressive targeted treatment of left, right, or biventricular failure. The goal is to prevent end-organ dysfunction and severe metabolic derangement by raising mean arterial pressure, which is achieved with inotropes and vasopressors, often at the expense of tachycardia, elevated myocardial oxygen consumption, and extended ischemia. The value of intra-aortic balloon counter-pulsation is now questioned in patients with advanced shock. When mean arterial pressure is <55 mmHg with serum lactate >11 mmol/l, death is likely and mechanical circulatory support becomes the only chance for survival.

[Respiratory and hemodynamic changes during lung recruitment maneuvering through progressive increases and decreases in PEEP level]

OBJECTIVE

To evaluate the respiratory and hemodynamic changes during lung recruitment maneuvering (LRM) through stepwise increases and decreases in PEEP level.

DESIGN AND SETTING

A retrospective study in a 17-bed ICU was carried out.

PATIENTS

Twenty-one patients with acute respiratory failure and bilateral pulmonary infiltration.

INTERVENTION

LRM was carried out, consisting of stepwise increases in PEEP (4 cmH(2)O every 3 minutes), with fixed ventilation pressure, until reaching a maximal value of 36 cmH(2)O PEEP (ascending branch), followed by progressive decreases in PEEP (2 cmH(2)O every 3 minutes) until establishing the open-lung PEEP at the value associated to maximum respiratory compliance (Crs) (descending branch). Continuous hemodynamic monitoring was performed using an esophageal echodoppler probe.

RESULTS

Crs gradually decreased in the ascending branch of the LRM, and progressively increased surpassing the initial value after establish the open-lung PEEP in the descending branch, reducing the ventilation pressure and increasing the SpO(2)/FiO(2) ratio. Hemodynamic changes primarily consisted of a fall in cardiac output and left ventricular preload, together with an increased heart rate and cardiac contractility. At comparable levels of PEEP and mean airway pressure, these changes were more pronounced during the descending branch of the LRM.

CONCLUSIONS

1) LRM increased Crs, improving oxygenation and decreasing ventilation pressure; 2) the main hemodynamic consequence was the drop in cardiac output and left ventricular preload; and 3) the unequal hemodynamic derangement in both branches, at the same level of PEEP and mean airway pressure, showed that, along with intrathoracic pressure, other factor such as Crs and hypercapnia may have influenced the hemodynamic consequences of this type of LRM.

Effect of the alveolar recruitment manoeuvre on haemodynamic parameters in patients with acute respiratory distress syndrome: relationship with oxygenation

BACKGROUND AND OBJECTIVE

Although the alveolar recruitment manoeuvre (ARM) is considered to be an optimal method of recruiting collapsed alveoli in a short period, the haemodynamic effects of the ARM have not been investigated. The aim of this study was to assess whether the ARM causes haemodynamic instability in patients with ARDS, and any relationship this might have with arterial oxygenation.

METHODS

Twenty-eight patients with ARDS (16 responders and 12 non-responders), who were admitted to the medical intensive care unit of a university-affiliated hospital, were enrolled in the study. ARM, using the extended sigh method, was performed within 48 h of the onset of ARDS. Haemodynamic parameters were measured at baseline, during the ARM, and at 2 min, 30 min and 1 h after the ARM.

RESULTS

Responders and non-responders showed no significant changes in blood pressure or cardiac index during or after ARM. Mean pulmonary artery pressure (MPAP), pulmonary vascular resistance index (PVRI) and right ventricular stroke work index (RVSWI) were transiently increased compared with baseline, in responders and non-responders. During and after ARM, the systemic vascular resistance index was significantly higher in non-responders than in responders.

CONCLUSIONS

Some haemodynamic parameters (MPAP, PVRI and RVSWI) changed significantly during ARM. However, these haemodynamic changes were minimal, transient and probably have no clinical significance.

N-terminal pro-brain natriuretic peptide as a marker of right ventricular dysfunction after open-lung approach in patients with acute lung injury/acute respiratory distress syndrome

PURPOSE

The purpose of the study was to evaluate the utility of N-terminal pro-brain natriuretic peptide (NT-proBNP) as a marker of right ventricular (RV) dysfunction after open-lung approach (OLA) in patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS).

MATERIALS AND METHODS

Twenty-seven patients with ALI/ARDS underwent OLA (2-minute steps of fixed pressure-controlled ventilation with progressive positive end-expiratory pressure levels up to 30 cm H(2)O, followed by stepwise decrement of positive end-expiratory pressure level by 2 cm H(2)O). Patients who showed a PaO(2)/FiO(2) increase of more than 50% from baseline were defined as responders. Plasma NT-proBNP levels were taken immediately before OLA and 2 and 6 hours later. A minimum 30% increase in NT-proBNP level from baseline was considered significant.

RESULTS

Right-over-left ventricular stroke work ratio and its percentage change did not differ between responders and nonresponders, whereas these values were higher in patients showing NT-proBNP increase (P < .05). The NT-proBNP percentage change correlated with right-over-left ventricular stroke work ratio percentage change (r = 0.83), pulmonary vascular resistance (r = 0.81), and RV ejection fraction (r = -0.79) and correlated with plateau pressure in nonresponders only (r = 0.82).

CONCLUSIONS

In patients with ALI/ARDS, intraindividual NT-proBNP changes correlated with RV afterload following OLA, thereby serving as a potential marker for RV dysfunction after OLA.

Medical and surgical treatment of acute right ventricular failure

Acute right ventricular (RV) failure is a frequent and serious clinical challenge in the intensive care unit. It is usually seen as a consequence of left ventricular failure, pulmonary embolism, pulmonary hypertension, sepsis, acute lung injury or after cardiothoracic surgery. The presence of acute RV failure not only carries substantial morbidity and mortality, but also complicates the use of commonly used treatment strategies in critically ill patients. In contrast to the left ventricle, the RV remains relatively understudied, and investigations of the treatment of isolated RV failure are rare and usually limited to nonrandomized observations. We searched PubMed for papers in the English language by using the search words right ventricle, right ventricular failure, pulmonary hypertension, sepsis, shock, acute lung injury, cardiothoracic surgery, mechanical ventilation, vasopressors, inotropes, and pulmonary vasodilators. These were used in various combinations. We read the abstracts of the relevant titles to confirm their relevance, and the full papers were then extracted. References from extracted papers were checked for any additional relevant papers. This review summarizes the general measures, ventilation strategies, vasoactive substances, and surgical as well as mechanical approaches that are currently used or actively investigated in the treatment of the acutely failing RV.

Acute lung injury and acute respiratory distress syndrome

Every year, more information accumulates about the possibility of treating patients with acute lung injury or acute respiratory distress syndrome with specially designed mechanical ventilation strategies. Ventilator modes, positive end-expiratory pressure settings, and recruitment maneuvers play a major role in these strategies. However, what can we take from these experimental and clinical data to the clinical practice? In this article, we discuss substantial options of mechanical ventilation together with some adjunctive therapeutic measures, such as prone positioning and inhalation of nitric oxide.

[Anaesthesia and right ventricular failure]

OBJECTIVE

The purpose of this review was to present an update of the anaesthesic management in patients with right ventricular failure (RVF).

DATA SOURCES

All references obtained from the medical database Medline related to the area and more specifically during the last five years were reviewed.

DATA SYNTHESIS

The preanaesthesic visit leads to identify the etiology of RVF, to evaluate the functional reserve of the patient, to plan complementary exams and to inform the patients about the risks associated with the perioperative period. During the peroperative period, the monitoring depends of the severity of the illness; however the invasive monitoring of the systemic blood pressure seems always necessary. Any hemodynamic instability should be avoided during the peri-operative period. Since the risk of death is maximal in the first days after the anaesthesia, the patient is ideally managed in intensive care during this period.

CONCLUSION

Right ventricular failure is often mis-estimated. However, the perioperative morbidity and mortality of patients with RVF are important. In the perioperative period, the anaesthesiologist should identify patients at risk of right ventricular failure in order to adapt their management.

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).

Effect of lung recruitment on pulmonary, systemic, and ductal blood flow in preterm infants

OBJECTIVE

To determine the effect of lung recruitment on pulmonary, systemic, and ductal blood flow in preterm infants treated with primary high-frequency ventilation (HFV).

STUDY DESIGN

Thirty-four infants (median gestational age, 28 weeks) were included in this prospective cohort study. Changes in oxygenation in response to stepwise changes in the continuous distending pressure (CDP) were used to monitor lung recruitment during HFV. For each individual patient, the opening pressure (CDPo), closing pressure (CDPc), and optimal pressure (CDPopt) were determined. Ultrasound measurements of right ventricular output (RVO), superior vena cava (SVC), and ductus arteriosus (DA) flow were performed at the start of recruitment (CDPs), CDPo, and CDPopt.

RESULTS

Increasing the CDP from 8 (CDPs) to 20 (CDPo) cmH(2)O resulted in a decreased RVO (mean difference, -17%; 95% CI, -24, -10%) and unchanged SVC flow and ductal shunting. Transient low RVO and SVC flow values at CDPo were seen in 3 and 2 infants, respectively.

CONCLUSIONS

Lung recruitment during HFV in preterm infants does not appear to result in clinically relevant changes in pulmonary, systemic, and ductal blood flow.

The right ventricle in sepsis

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

Bench-to-bedside review: ventilatory abnormalities in sepsis

In septic patients increased central drive and increased metabolic demands combine to increase energy demands on the ventilatory muscles. This occurs at a time when energy supplies are limited and energy production hindered, and it leads to an energy supply-demand imbalance and often ventilatory failure. Problems related to contractile function of the ventilatory muscles also contribute, especially when the clinical course is prolonged. The increased ventilatory activity increases interactions between the ventilatory and cardiovascular systems, and when ventilatory muscles fail and mechanical ventilatory support is required a new set of problems emerges. In this review I discuss factors related to ventilatory muscle failure, giving emphasis to mechanical and supply demand aspects. I also review the implications of changes in ventilatory patterns for heart-lung interactions.

Echocardiography practice, training and accreditation in the intensive care: document for the World Interactive Network Focused on Critical Ultrasound (WINFOCUS)

Echocardiography is increasingly used in the management of the critically ill patient as a non-invasive diagnostic and monitoring tool. Whilst in few countries specialized national training schemes for intensive care unit (ICU) echocardiography have been developed, specific guidelines for ICU physicians wishing to incorporate echocardiography into their clinical practice are lacking. Further, existing echocardiography accreditation does not reflect the requirements of the ICU practitioner. The WINFOCUS (World Interactive Network Focused On Critical UltraSound) ECHO-ICU Group drew up a document aimed at providing guidance to individual physicians, trainers and the relevant societies of the requirements for the development of skills in echocardiography in the ICU setting. The document is based on recommendations published by the Royal College of Radiologists, British Society of Echocardiography, European Association of Echocardiography and American Society of Echocardiography, together with international input from established practitioners of ICU echocardiography. The recommendations contained in this document are concerned with theoretical basis of ultrasonography, the practical aspects of building an ICU-based echocardiography service as well as the key components of standard adult TTE and TEE studies to be performed on the ICU. Specific issues regarding echocardiography in different ICU clinical scenarios are then described. Obtaining competence in ICU echocardiography may be achieved in different ways - either through completion of an appropriate fellowship/training scheme, or, where not available, via a staged approach designed to train the practitioner to a level at which they can achieve accreditation. Here, peri-resuscitation focused echocardiography represents the entry level--obtainable through established courses followed by mentored practice. Next, a competence-based modular training programme is proposed: theoretical elements delivered through blended-learning and practical elements acquired in parallel through proctored practice. These all linked with existing national/international echocardiography courses. When completed, it is anticipated that the practitioner will have performed the prerequisite number of studies, and achieved the competency to undertake accreditation (leading to Level 2 competence) via a recognized National or European examination and provide the appropriate required evidence of competency (logbook). Thus, even where appropriate fellowships are not available, with support from the relevant echocardiography bodies, training and subsequently accreditation in ICU echocardiography becomes achievable within the existing framework of current critical care and cardiological practice, and is adaptable to each countrie's needs.

[Pulmonary hypertension and right ventricular failure in critical care medicine]

The management of pulmonary hypertension and right ventricular failure in hemodynamically unstable patients is one of the most challenging situations in critical care medicine. Inadequate therapy, e.g. aggressive fluid resuscitation or invasive ventilation, may even harm patients with pulmonary hypertension. Identifying the underlying etiology therefore remains the primary focus for initiating successful management of patients with decompensated pulmonary hypertension and right ventricular failure. Pulmonary embolism requires immediate restoration of pulmonary vascular patency. The body of evidence from studies is scarce and favors dobutamine, NO inhalation, and intravenous prostacyclin. However, the use of other vasoactive substances, inotropes, and supportive measures has been successful in individual patients; it should be guided by the expected effects on the pulmonary vasculature or right ventricle, and should be adapted to the patient's concomitant diseases.

Cardiovascular effects of mechanical ventilation and weaning

Because of their anatomic position in the closed thoracic cavity, the heart and lungs interact during each ventilation cycle. The application of mechanical ventilation and subsequent removal changes normal ventilatory mechanics and produces alterations in cardiac preload and afterload that influence global hemodynamic state and delivery of oxygen and nutrients. Adverse cardiovascular responses to mechanical ventilation and weaning from ventilation include hemodynamic alterations and instability, myocardial ischemia, autonomic dysfunction, and cardiac dysrhythmias. Clinicians must have a clear understanding of the cardiovascular effects of mechanical ventilation and weaning so they may anticipate, recognize, and effectively manage negative effects and improve patient outcomes.

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.

Echocardiographic assessment of pulmonary artery occlusion pressure in ventilated patients: a transoesophageal study

Background

Non-invasive evaluation of left ventricular filling pressure has been scarcely studied in critically ill patients. Accordingly, we prospectively assessed the ability of transoesophageal echocardiography (TEE) Doppler to predict an invasive pulmonary artery occlusion pressure (PAOP) ≤ 18 mmHg in ventilated patients.

Methods

During two consecutive 3-year periods, TEE Doppler parameters were compared to right heart catheterisation derived PAOP used as reference in 88 ventilated patients, haemodynamically stable and in sinus rhythm (age: 63 ± 14 years; simplified acute physiologic score (SAPS) II: 45 ± 12). During the initial period (protocol A), threshold values of pulsed-wave Doppler parameters to predict an invasive PAOP ≤ 18 mmHg were determined in 56 patients. Derived Doppler values were prospectively tested during the subsequent period (protocol B) in 32 patients.

Results

In protocol A, Doppler parameters had similar area under the receiver operating characteristic (ROC) curve. In protocol B, mitral E/A ≤ 1.4, pulmonary vein S/D > 0.65 and systolic fraction > 44% best predicted an invasive PAOP ≤ 18 mmHg. Lateral E/E' ≤ 8.0 or E/Vp ≤ 1.7 predicted a PAOP ≤ 18 mmHg with a sensitivity of 83% and 80%, and a specificity of 88% and 100%, respectively. Areas under ROC curves of lateral E/E' and E/Vp were similar (0.91 ± 0.07 vs 0.92 ± 0.07: p = 0.53), and not significantly different from those of pulsed-wave Doppler indices.

Conclusion

TEE accurately predicts invasive PAOP ≤ 18 mmHg in ventilated patients. This further increases its diagnostic value in patients with suspected acute lung injury/acute respiratory distress syndrome.

Management strategies for patients with pulmonary hypertension in the intensive care unit

OBJECTIVE

Pulmonary hypertension may be encountered in the intensive care unit in patients with critical illnesses such as acute respiratory distress syndrome, left ventricular dysfunction, and pulmonary embolism, as well as after cardiothoracic surgery. Pulmonary hypertension also may be encountered in patients with preexisting pulmonary vascular, lung, liver, or cardiac diseases. The intensive care unit management of patients can prove extremely challenging, particularly when they become hemodynamically unstable. The objective of this review is to discuss the pathogenesis and physiology of pulmonary hypertension and the utility of various diagnostic tools, and to provide recommendations regarding the use of vasopressors and pulmonary vasodilators in intensive care.

DATA SOURCES AND EXTRACTION

We undertook a comprehensive review of the literature regarding the management of pulmonary hypertension in the setting of critical illness. We performed a MEDLINE search of articles published from January 1970 to March 2007. Medical subject headings and keywords searched and cross-referenced with each other were: pulmonary hypertension, vasopressor agents, therapeutics, critical illness, intensive care, right ventricular failure, mitral stenosis, prostacyclin, nitric oxide, sildenafil, dopamine, dobutamine, phenylephrine, isoproterenol, and vasopressin. Both human and animal studies related to pulmonary hypertension were reviewed.

CONCLUSIONS

Pulmonary hypertension presents a particular challenge in critically ill patients, because typical therapies such as volume resuscitation and mechanical ventilation may worsen hemodynamics in patients with pulmonary hypertension and right ventricular failure. Patients with decompensated pulmonary hypertension, including those with pulmonary hypertension associated with cardiothoracic surgery, require therapy for right ventricular failure. Very few human studies have addressed the use of vasopressors and pulmonary vasodilators in these patients, but the use of dobutamine, milrinone, inhaled nitric oxide, and intravenous prostacyclin have the greatest support in the literature. Treatment of pulmonary hypertension resulting from critical illness or chronic lung diseases should address the primary cause of hemodynamic deterioration, and pulmonary vasodilators usually are not necessary.

Variation in natriuretic peptides and mitral flow indexes during successful ventilatory weaning: a preliminary study

OBJECTIVE

To assess the cardiac consequences of successful respiratory weaning using the variations of circulating B-type and atrial natriuretic peptides (BNP, ANP) and Doppler mitral flow.

DESIGN

A prospective preliminary observational study.

SETTING

A 14-bed medical ICU in a French university hospital.

PATIENTS

Thirty-one patients undergoing a spontaneous breathing trial on a T-tube.

INTERVENTIONS

Circulating BNP and ANP levels and Doppler-derived E/A ratio and deceleration time of the E wave were measured before and 1 h after disconnection.

RESULTS

BNP levels increased from 299 pg/ml (range 56-1079) to 412 pg/ml (147-1324) (p=0.02) in patients with systolic left ventricular dysfunction, decreased from 98 pg/ml (25-337) to 45 pg/ml (38-180) (p=0.04) in patients with right ventricular dilation and remained unchanged in patients with neither of these cardiac abnormalities. Overall ANP levels increased from 33 pg/ml to 67 pg/ml (p<0.001) regardless of ventricular function. The E/A ratio increased from 0.91 (0.66-3.56) to 1.17 (0.5-4.76), (p=0.01), after disconnection, whereas deceleration time of E wave decreased from 185 ms (120-280) to 160 ms (70-206) (p=0.02).

CONCLUSION

During successful weaning from mechanical ventilation ANP levels increase in all patients whereas changes in BNP levels depend on underlying cardiac function. Changes in Doppler mitral flow indexes following ventilator disconnection suggest an increase in left-ventricular filling pressure.