François Kerbaul

Effects of levosimendan versus dobutamine on pressure load-induced right ventricular failure.

Objective:A transient increase in pulmonary arterial (PA) pressure can persistently depress right ventricular (RV) contractility. We investigated the effects of dobutamine and levosimendan on RV-PA coupling in this model of RV failure. Design:Prospective, controlled, randomized animal study. Setting:University research laboratory. Subjects:Fifteen anesthetized dogs. Interventions:Transient (90-min) PA constriction to induce persistent RV failure. Random assignment to dobutamine 5 and 10 &mgr;g/kg/min or levosimendan 12 &mgr;g/kg for 10 mins followed by 0.1 and 0.2 &mgr;g/kg/min. Measurements and Main Results:We measured PA distal resistance and proximal elastance by pressure-flow relationships and vascular impedance. We measured RV contractility by the end-systolic pressure-volume relationship (Ees), PA effective elastance by the end-diastolic to end-systolic relationship (Ea), and RV-PA coupling efficiency by the Ees/Ea ratio. PA constriction persistently increased PA resistance and elastance, increased Ea from 0.95 ± 0.07 to 3.01 ± 0.28 mm Hg/mL, decreased Ees from 1.17 ± 0.09 to 0.58 ± 0.07 mm Hg/mL, and decreased Ees/Ea from 1.26 ± 0.09 to 0.22 ± 0.03 (p < .05). Dobutamine did not affect pulmonary hemodynamics, markedly increased RV contractility, and improved RV-PA coupling. Levosimendan decreased PA resistance and elastance, increased RV contractility, and restored RV-PA coupling. Compared with dobutamine, levosimendan decreased RV afterload and therefore better restored RV-PA coupling at similar inotropic state. Conclusions:A transient increase in PA pressure persistently worsens PA hemodynamics, RV contractility, RV-PA coupling, and cardiac output. Levosimendan restores RV-PA coupling better than dobutamine because of similar inotropic effects and additional pulmonary vasodilatory effects.

Effects of levosimendan on acute pulmonary embolism-induced right ventricular failure.

Objective:Repeated episodes of pulmonary embolism can persistently increase pulmonary arterial pressure and depress right ventricular contractility. We investigated the effects of levosimendan on right ventricular-pulmonary arterial coupling in this model of right ventricular failure. Design:Prospective, controlled, randomized animal study. Setting:University research laboratory. Subjects:Fourteen anesthetized piglets. Interventions:Repeated acute pulmonary embolisms were induced with autologous blood clots to induce persistent right ventricular failure. Animals were randomly assigned to a control or levosimendan group. Levosimendan 20 &mgr;g/kg was administered in 10 mins followed by 0.2 &mgr;g/kg/min or same volumes of isotonic saline. Measurements and Main Results:Pulmonary artery distal resistance and proximal elastance by pressure-flow relationships and vascular impedance were measured. We noted right ventricle contractility by the end-systolic pressure-volume relationship (Ees), pulmonary artery effective elastance by the end-diastolic to end-systolic relationship (Ea), and right ventricular-pulmonary arterial coupling efficiency by the Ees/Ea ratio. The gradual pulmonary artery embolism increased pulmonary artery resistance and elastance, increased Ea from 1.01 ± 0.17 to 5.58 ± 0.37 mm Hg/mL, decreased Ees from 1.75 ± 0.12 to 1.29 ± 0.20 mm Hg/mL, and decreased Ees/Ea from 1.74 ± 0.20 to 0.24 ± 0.09. Compared with placebo, levosimendan decreased pulmonary arterial elastance and characteristic impedance. Right ventricular-pulmonary arterial coupling was restored by both an increase in right ventricular contractility and a decrease in right ventricular afterload. Conclusions:A gradual increase in pulmonary artery pressure induced by pulmonary embolism persistently worsens pulmonary artery hemodynamics, right ventricular contractility, right ventricular-pulmonary arterial coupling, and cardiac output. Levosimendan restores right ventricular-pulmonary arterial coupling better than placebo, because of combined pulmonary vasodilation and increased right ventricular contractility.

Prolonged overcirculation-induced pulmonary arterial hypertension as a cause of right ventricular failure

AIMS Three-month chronic systemic-to-pulmonary shunting in growing piglets has been reported as an early pulmonary arterial hypertension (PAH) model with preserved right ventricular (RV) function. We sought to determine whether prolonged shunting might be associated with more severe PAH and RV failure. METHODS AND RESULTS Fourteen growing piglets were randomized to a sham operation or the anastomosis of the left innominate artery to the pulmonary arterial trunk. Six months later, the shunt was closed and the animals underwent haemodynamic evaluation followed by tissue sampling for pathobiological assessment. Prolonged shunting had resulted in increased mean pulmonary artery pressure (22 ± 2 versus 17 ± 1 mmHg) and pulmonary arteriolar medial thickness, while cardiac output was decreased. However, RV-arterial coupling was markedly deteriorated, with a ~50% decrease in the ratio of end-systolic to pulmonary arterial elastances (Ees/Ea). Lung tissue expressions of endothelin-1, angiopoietin-1, and bone morphogenetic protein receptor-2 were similarly altered compared with previously observed after 3-month shunting. At the RV tissue level, pro-apoptotic ratio of Bax-to-Bcl-2 expressions and caspase-3 activation were increased, along with an increase in cardiomyocyte size, while expressions in voltage-gated potassium channels (Kv1.5 and Kv2.1) and angiogenic factors (angiopoietin-2 and vascular endothelial growth factor) were decreased. Right ventricular expressions of pro-inflammatory cytokines [interleukin (IL)-1α, IL-1β, tumour necrosis factor-α (TNF-α)] and natriuretic peptide precursors (NPPA and NPPB) were increased. There was an inverse correlation between RV Ees/Ea and pro-apoptotic Bax/Bcl-2 ratios. CONCLUSIONS Prolonged left-to-right shunting in piglets does not further aggravate pulmonary vasculopathy, but is a cause of RV failure, which appears related to an activation of apoptosis and inflammation.

Combination of histopathological and electromyographic patterns can help to evaluate functional outcome of critical ill patients with neuromuscular weakness syndromes

IntroductionThe aim of the study was to describe patterns of neuromuscular weakness using a combination of electromyography and histology, and to evaluate functional outcome in patients following complicated cardiovascular surgery.MethodsFifteen adults requiring long-term mechanical ventilation (>15 days) following cardiovascular surgery associated with postoperative complications were prospectively included. Electrophysiological and histological analyses (muscle and nerve) were performed when failure to wean from mechanical ventilation associated with peripheral neuromuscular weakness was noticed. Functional disability was evaluated 12 months after surgery.ResultsSix patients had a predominantly axonal neuropathy, six presented with myopathy, and three patients had a combination of axonal neuropathy and myopathy. All of them presented with acute tetraparesis and failure to wean from mechanical ventilation. All of the study patients who received corticosteroids exhibited a myopathic pattern (with or without axonopathic changes) but never an axonopathic pattern only. Only two of the eight survivors at 12 months were not ambulatory. These two patients had no detectable compound muscle action potential on electrophysiological examination.ConclusionThe combination of electromyographic evaluation and neuromuscular histological abnormalities could help to identify the type and severity of neuromuscular weakness, in turn helping to evaluate the patients potential functional prognosis.

Expression of the serotonin 1b receptor in experimental pulmonary hypertension

The pathogenesis of pulmonary arterial hypertension (PAH) remains uncertain. Both the serotonin and endothelin (ET) systems are believed to be involved. Recent studies pointed to the importance of the serotonin 2B receptor as a limiting step. The current authors investigated the lung tissue expression of serotonin receptors and of the serotonin transporter (5‐HTT) by real-time-quantitative polymerase chain reaction in chronic overcirculation-induced PAH in growing piglets, with and without treatment with the dual ET receptor blocker bosentan. Pulmonary haemodynamic changes were described by pulmonary arterial impedance spectra. Three months after the surgical anastomosis of the left subclavian artery to the pulmonary arterial trunk, there was a shift of the impedance spectra to higher ratios of pressure and flow moduli, with increases in both 0 Hz impedance and characteristic impedance, and these changes were completely prevented by bosentan therapy. There was an increase in the expression of the serotonin 1B receptor. There was no change in the expression of the 5‐HTT, and of the serotonin 2B, 1D, and 4 receptors. The overexpression of the serotonin 1B receptor was partially prevented by bosentan therapy. The present authors conclude that this early pulmonary arterial hypertension model is characterised by an endothelin receptor-dependent increased expression of the serotonin 1B receptor.

Mobile Extracorporeal Membrane Oxygenation Unit Expands Cardiac Assist Surgical Programs

BACKGROUND Extracorporeal membrane oxygenation (ECMO) is an effective technique to provide emergency mechanical circulatory or respiratory assistance in critically ill patients. A Mobile Remote Cardiac Assist unit was created to implant ECMO in patients from outside our institution and bring them back in our intensive care unit for follow-up when stabilized. This study was undertaken to evaluate the feasibility and the preliminary results of this procedure. METHODS Between March 2006 and June 2008, 38 consecutive patients with acute cardiac or respiratory failure were implanted with percutaneous ECMO. The logistic concerns, indications, complications, and outcomes of these patients were analyzed. RESULTS There were no logistic or technical problems during the round trip or ECMO implantation. Mean distance from our intensive care unit was 68 km (1 to 230). Maximal time limit between the phone call and implantation was 90 minutes. The indications were fulminant myocarditis, pharmacologic suicide attempt, acute myocardial infarction, postpartum cardiopathy, end-stage cardiomyopathy, with left ventricular ejection fraction of 0.19 ± 0.05 (n = 32), or acute respiratory distress syndrome without cardiac failure (n = 6). Patients received a percutaneous venoarterial femoral ECMO with immediate reperfusion of the limb or venovenous ECMO for isolated lung failure. Seventeen patients (45%) were successfully weaned from ECMO after 9.4 ± 8.7 days. Four patients (11%) were transplanted. One patient was switched to a left ventricular assist device and was then successfully transplanted. Twenty-one patients (55%) survived to hospital discharge. CONCLUSIONS The Mobile Cardiac Assist unit allowed emergency implantation of ECMO support in remote institutions without any logistic or technical problems.

Isoflurane and desflurane impair right ventricular-pulmonary arterial coupling in dogs

Background:Halogenated anesthetics depress left ventricular function, but their effects on the right ventricle have been less well studied. Therefore, the authors studied the effects of isoflurane and desflurane on pulmonary arterial (PA) and right ventricular (RV) properties at baseline and in hypoxia. Methods:Right ventricular and PA pressures were measured by micromanometer catheters, and PA flow was measured by an ultrasonic flow probe. PA mechanics were assessed by flow–pressure relations and by impedance spectra derived from flow and pressure waves. RV contractility was assessed by end-systolic elastance (Ees), RV afterload was assessed by effective PA elastance (Ea), and RV–PA coupling efficiency was assessed by the Ees:Ea ratio. Anesthetized dogs were randomly assigned to increasing concentrations (0.5, 1, and 1.5 times the minimum alveolar concentration) of isoflurane (n = 7) or desflurane (n = 7) in hyperoxia (fraction of inspired oxygen, 0.4) and hypoxia (fraction of inspired oxygen, 0.1). Results:Isoflurane and desflurane had similar effects. During hyperoxia, both anesthetics increased PA resistance and characteristic impedance, increased Ea (isoflurane, from 0.82 to 1.44 mmHg/ml; desflurane, from 0.86 to 1.47 mmHg/ml), decreased Ees (isoflurane, from 1.09 to 0.66 mmHg/ml; desflurane, from 1.10 to 0.72 mmHg/ml), and decreased Ees:Ea (isoflurane, from 1.48 to 0.52; desflurane, from 1.52 to 0.54) in a dose-dependent manner (all P < 0.05). Hypoxia increased PA resistance, did not affect characteristic impedance, increased afterload, and increased contractility. During hypoxia, isoflurane and desflurane had similar ventricular effects as during hyperoxia. Conclusions:Isoflurane and desflurane markedly impair RV–PA coupling efficiency in dogs, during hyperoxia and hypoxia, both by increasing RV afterload and by decreasing RV contractility.

Is there any benefit to adding intravenous ketamine to patient-controlled epidural analgesia after thoracic surgery? A randomized double-blind study

OBJECTIVES Thoracic surgery is associated with severe acute postoperative pain, leading to pulmonary complications and hyperalgesia-induced chronic pain. Thoracic patient-controlled epidural analgesia is also considered as the gold-standard postoperative analgesia. As previously described in major digestive surgery, combination with low-dose intravenous (i.v.) ketamine could potentiate epidural analgesia and facilitate pulmonary function recovery following thoracotomy. METHODS In a randomized, double-blind trial, 60 patients scheduled to undergo thoracotomy were included. All patients received a thoracic epidural catheter placed before surgery, and standardized general anaesthesia. They were allocated to two groups to receive either an i.v. bolus of ketamine at induction, followed by a continuous infusion during surgery and the first 48 h postoperatively, or an i.v. placebo (a saline solution under the same infusion modalities). Cumulative epidural ropivacaine consumption, postoperative pain scores (patient self-rated numeric pain intensity scale), analgesic rescue consumption, residual pain, haemodynamics and respiratory recovery function were recorded from 12 h to 3 months. Data were expressed as mean ± standard deviation or median ± interquartile range (25-75%). The comparisons between ketamine and placebo groups were performed using χ(2) or Fishers exact tests for frequencies, and Mann-Whitney tests for quantitative variables. RESULTS Epidural ropivacaine consumption was similar between groups during the first 48 postoperative hours. Postoperative pain scores and spirometric parameters were not significantly different between groups. But the incidence of postoperative nausea was significantly increased in patients owning to the ketamine group. Finally, the incidence of residual pain was similar between groups at 1 and 3 months following thoracotomy. CONCLUSIONS Adding i.v. ketamine did not potentiate epidural analgesia neither to reduce acute and chronic postoperative pain nor to improve pulmonary dysfunction following thoracic surgery. Pain scores were low in both groups, mainly because of an optimized analgesia provided by the patient-controlled epidural mode, and might explain this lack of benefit in adding i.v. ketamine.

Endogenous endothelins and nitric oxide in hypoxic pulmonary vasoconstriction

The effects of endothelin receptor blockade on the pulmonary circulation have been reported variably, possibly in relation to a more or less important associated release of endogenous nitric oxide (NO). The aim of this study was to test whether endothelin antagonism would inhibit hypoxic pulmonary vasoconstriction, and if it would not, then would it do so after NO synthase inhibition. Hypoxic pulmonary vasoconstriction (HPV) was evaluated in anesthetised dogs by the increase in the mean pulmonary artery pressure (Ppa) minus occluded Ppa (Ppao) gradient in response to hypoxia (inspiratory oxygen fraction of 0.1) at constant pulmonary blood flow. Bosentan, an endothelin A and B receptor antagonist, did not affect baseline Ppa, Ppao or systemic arterial pressure (Psa) and did not alter HPV (n=8). The NO synthase inhibitor NGnitro‐l‐arginine (l‐NA) did not affect baseline Ppa and Ppao, but increased Psa and enhanced HPV (n=12). The addition of bosentan in these dogs did not affect baseline Ppa or Ppao, but decreased Psa and inhibited HPV. Exhaled NO was decreased by l‐NA and by bosentan and abolished by l‐NA+bosentan (n=9). The authors conclude that endogenous nitric oxide is released by, and opposes the vasoconstricting effects of, endothelins in vivo, reducing systemic blood pressure and limiting hypoxic pulmonary vasoconstriction.

Myocardial inflammation in experimental acute right ventricular failure: Effects of prostacyclin therapy.

BACKGROUND Acute transient pulmonary hypertension may induce a state of persistent right ventricular (RV) failure. We hypothesized that this could be related to an activation of inflammatory processes and reduced by prostacyclin therapy. METHODS Sixteen dogs were assigned to a 90-minute pulmonary artery banding (n = 8), or to a sham operation (n = 8). Hemodynamic variables were measured 30 minutes after banding release. This was repeated in 7 dogs with pulmonary artery banding-induced RV failure, followed by a 60-minute epoprostenol infusion. After euthanasia of the animals, myocardial tissue was sampled. RESULTS Persistent RV failure was associated with increased myocardial expression of interleukin (IL)-1β, IL-6, monocyte chemoattractant protein 1, pro-inflammatory IL-6/IL-10, and neutrophil and macrophage infiltration, whereas heme oxygenase 1 expression was decreased. These changes were observed in RV and to a lesser extent in the left ventricle (LV). In the RV only, expressions of prostacyclin synthase and anti-inflammatory IL-10 and IL-33 decreased and vascular cell adhesion molecule expression increased, whereas macrophage inflammatory protein-1α and intercellular adhesion molecule 1 expressions remained unchanged. After epoprostenol infusion, there was decreased expression of IL-1β, macrophage inflammatory protein-1α, and vascular cell adhesion molecule 1 and increased IL-10 expression in the RV and the LV, whereas monocyte chemoattractant protein-1 decreased in the RV only. Epoprostenol infusion resulted in decreased RV IL-6/IL-10 and pro-apoptotic Bax/Bcl-2, together with decreased RV neutrophil and RV and LV macrophage infiltration. The RV ratio of end systolic-to-pulmonary arterial elastances was inversely correlated to RV IL-6/IL-10, macrophage, and neutrophil infiltration, and to RV heme oxygenase-1 and IL-33 expression. CONCLUSIONS Acute afterload-induced persistent RV failure is associated with an activation of inflammatory processes, which are limited by epoprostenol.