The effects of levosimendan and glibenclamide on circulatory and metabolic variables in a canine model of acute hypoxia

Pressure Overload and Right Ventricular Failure: From Pathophysiology to Treatment

Right ventricular failure (RVF) is often caused by increased afterload and disrupted coupling between the right ventricle (RV) and the pulmonary arteries (PAs). After a phase of adaptive hypertrophy, pressure-overloaded RVs evolve towards maladaptive hypertrophy and finally ventricular dilatation, with reduced stroke volume and systemic congestion. In this article, we review the concept of RV-PA coupling, which depicts the interaction between RV contractility and afterload, as well as the invasive and non-invasive techniques for its assessment. The current principles of RVF management based on pathophysiology and underlying etiology are subsequently discussed. Treatment strategies remain a challenge and range from fluid management and afterload reduction in moderate RVF to vasopressor therapy, inotropic support and, occasionally, mechanical circulatory support in severe RVF.

Levosimendan in the light of the results of the recent randomized controlled trials: an expert opinion paper

Despite interesting and unique pharmacological properties, levosimendan has not proven a clear superiority to placebo in the patient populations that have been enrolled in the various recent multicenter randomized controlled trials. However, the pharmacodynamic effects of levosimendan are still considered potentially very useful in a number of specific situations.Patients with decompensated heart failure requiring inotropic support and receiving beta-blockers represent the most widely accepted indication. Repeated infusions of levosimendan are increasingly used to facilitate weaning from dobutamine and avoid prolonged hospitalizations in patients with end-stage heart failure, awaiting heart transplantation or left ventricular assist device implantation. New trials are under way to confirm or refute the potential usefulness of levosimendan to facilitate weaning from veno-arterial ECMO, to treat cardiogenic shock due to left or right ventricular failure because the current evidence is mostly retrospective and requires confirmation with better-designed studies. Takotsubo syndrome may represent an ideal target for this non-adrenergic inotrope, but this statement also relies on expert opinion. There is no benefit from levosimendan in patients with septic shock. The two large trials evaluating the prophylactic administration of levosimendan (pharmacological preconditioning) in cardiac surgical patients with poor left ventricular ejection fraction could not show a significant reduction in their composite endpoints reflecting low cardiac output syndrome with respect to placebo. However, the subgroup of those who underwent isolated CABG appeared to have a reduction in mortality. A new study will be required to confirm this exploratory finding.Levosimendan remains a potentially useful inodilator agent in a number of specific situations due to its unique pharmacological properties. More studies are needed to provide a higher level of proof regarding these indications.

Levosimendan in pulmonary hypertension and right heart failure

Pulmonary hypertension is a multifactorial disease with a high morbidity and mortality. Right ventricular function is the most important predictor of morbidity and mortality in patients suffering from pulmonary hypertension, but currently there are no approved treatments directly supporting the failing right ventricle. Levosimendan is a calcium sensitizing agent with inotropic, pulmonary vasodilatory, and cardioprotective properties. Given its pharmacodynamic profile, levosimendan could be a potential novel agent for the treatment of right ventricular failure caused by pulmonary hypertension. The aim of this review is to provide an overview of the current knowledge on the effects of levosimendan in pulmonary hypertension and right heart failure.

Effect of Topical Iloprost and Nitroglycerin on Gastric Microcirculation and Barrier Function during Hemorrhagic Shock in Dogs

BACKGROUND

Topical drug application is used to avoid systemic side effects. The aim of this study was to analyze whether locally applied iloprost or nitroglycerin influence gastric mucosal perfusion, oxygenation, and barrier function during physiological and hemorrhagic conditions.

METHODS

In repeated experiments, 5 anesthetized dogs received iloprost, nitroglycerin, or normal saline during physiological and hemorrhagic (-20% blood volume) conditions. Macro- and microcirculatory variables were recorded continuously. Gastric barrier function was assessed via translocation of sucrose into the blood.

RESULTS

During hemorrhage, gastric mucosal oxygenation decreased from 77 ± 4 to 37 ± 7%. This effect was attenuated by nitroglycerin (78 ± 6 to 47 ± 13%) and iloprost (82 ± 4 to 54 ± 9%). Sucrose plasma levels increased during hemorrhage from 7 ± 4 to 55 ± 15 relative amounts. This was alleviated by nitroglycerin (5 ± 8 to 29 ± 38 relative amounts). These effects were independent of systemic hemodynamic variables.

CONCLUSIONS

During hemorrhage, topical nitroglycerin and iloprost improve regional gastric oxygenation without affecting perfusion. Nitroglycerin attenuated the shock-induced impairment of the mucosal barrier integrity. Thus, local drug application improves gastric microcirculation without compromising systemic hemodynamic variables, and it may also protect mucosal barrier function.

Absolute and trend accuracy of a new regional oximeter in healthy volunteers during controlled hypoxia

BACKGROUND:

Traditional patient monitoring may not detect cerebral tissue hypoxia, and typical interventions may not improve tissue oxygenation. Therefore, monitoring cerebral tissue oxygen status with regional oximetry is being increasingly used by anesthesiologists and perfusionists during surgery. In this study, we evaluated absolute and trend accuracy of a new regional oximetry technology in healthy volunteers.

METHODS:

A near-infrared spectroscopy sensor connected to a regional oximetry system (O3^TM, Masimo, Irvine, CA) was placed on the subject’s forehead, to provide continuous measurement of regional oxygen saturation (rSo₂). Reference blood samples were taken from the radial artery and internal jugular bulb vein, at baseline and after a series of increasingly hypoxic states induced by altering the inspired oxygen concentration while maintaining normocapnic arterial carbon dioxide pressure (Paco₂). Absolute and trend accuracy of the regional oximetry system was determined by comparing rSo₂ against reference cerebral oxygen saturation (Savo₂), that is calculated by combining arterial and venous saturations of oxygen in the blood samples.

RESULTS:

Twenty-seven subjects were enrolled. Bias (test method mean error), standard deviation of error, standard error of the mean, and root mean square accuracy (A_RMS) of rSo₂ compared to Savo₂ were 0.4%, 4.0%, 0.3%, and 4.0%, respectively. The limits of agreement were 8.4% (95% confidence interval, 7.6%–9.3%) to −7.6% (95% confidence interval, −8.4% to −6.7%). Trend accuracy analysis yielded a relative mean error of 0%, with a standard deviation of 2.1%, a standard error of 0.1%, and an A_RMS of 2.1%. Multiple regression analysis showed that age and skin color did not affect the bias (all P > 0.1).

CONCLUSIONS:

Masimo O3 regional oximetry provided absolute root-mean-squared error of 4% and relative root-mean-squared error of 2.1% in healthy volunteers undergoing controlled hypoxia.

The role of Levosimendan in cardiopulmonary resuscitation

Although initial resuscitation from cardiac arrest (CA) has increased over the past years, long term survival rates remain dismal. Epinephrine is the vasopressor of choice in the treatment of CA. However, its efficacy has been questioned, as it has no apparent benefits for long-term survival or favorable neurologic outcome. Levosimendan is an inodilator with cardioprotective and neuroprotective effects. Several studies suggest that it is associated with increased rates of return of spontaneous circulation as well as improved post-resuscitation myocardial function and neurological outcome. The purpose of this article is to review the properties of Levosimendan during cardiopulmonary resuscitation (CPR) and also to summarize existing evidence regarding the use of Levosimendan in the treatment of CA.

Hypothermia improves oral and gastric mucosal oxygenation during hypoxic challenges

BACKGROUND

Therapeutic hypothermia, used primarily for protective effects after hypoxia, improves oral and gastric mucosal microvascular oxygenation (μHbO₂) during additional haemorrhage. Therefore, we questioned whether hypothermia likewise improves μHbO₂ during hypoxic challenges. Since both hypothermia and hypoxia reduce cardiac output (e.g. by myofilament Ca(2+) desensitization), and modulate vasomotor tone via K(+) ATP channels, we hypothesized that the Ca(2+) sensitizer levosimendan and K(+) ATP channel blocker glibenclamide would support the cardiovascular system.

METHODS

The effects of mild hypothermia (34°C) on μHbO₂ during hypoxia [Formula: see text] were analysed in a cross-over study on five anaesthetized dogs and compared with normothermia (37.5°C) and hypoxia. During hypothermia, but before hypoxia, glibenclamide (0.2 mg kg(-1)) or levosimendan (20 µg kg(-1)+0.25 µg kg(-1) min(-1)) was administered. Systemic haemodynamic variables, gastric and oral mucosal microvascular oxygenation (reflectance spectrophotometry), and perfusion (laser Doppler flowmetry) were recorded continuously. Data are presented as mean (sem), P<0.05.

RESULTS

Hypoxia during normothermia reduced gastric μHbO₂ by 27 (3)% and oral μHbO₂ by 28 (3)% (absolute change). During hypothermia, this reduction was attenuated to 16 (3)% and 13 (1)% (absolute change). This effect was independent of microvascular flow that did not change during hypoxia and hypothermia. Additional administration of levosimendan during hypothermia restored reduced cardiac output but did not change flow or μHbO₂ compared with hypothermia alone. Glibenclamide did not exert any additional effects during hypothermia.

CONCLUSIONS

Hypothermia attenuates the decrease in μHbO₂ during additional hypoxic challenges independent of systemic or regional flow changes. A reduction in cardiac output during hypothermia is prevented by Ca(2+) sensitization with levosimendan but not by K(+) ATP channel blockade with glibenclamide.

Monitoring tissue oxygenation by near infrared spectroscopy (NIRS): background and current applications

Conventional cardiovascular monitoring may not detect tissue hypoxia, and conventional cardiovascular support aiming at global hemodynamics may not restore tissue oxygenation. NIRS offers non-invasive online monitoring of tissue oxygenation in a wide range of clinical scenarios. NIRS monitoring is commonly used to measure cerebral oxygenation (rSO(2)), e.g. during cardiac surgery. In this review, we will show that tissue hypoxia occurs frequently in the perioperative setting, particularly in cardiac surgery. Therefore, measuring and obtaining adequate tissue oxygenation may prevent (postoperative) complications and may thus be cost-effective. NIRS monitoring may also be used to detect tissue hypoxia in (prehospital) emergency settings, where it has prognostic significance and enables monitoring of therapeutic interventions, particularly in patients with trauma. However, optimal therapeutic agents and strategies for augmenting tissue oxygenation have yet to be determined.

From system to organ to cell: oxygenation and perfusion measurement in anesthesia and critical care

Maintenance or restoration of adequate tissue oxygenation is a main goal of anesthesiologic and intensive care patient management. Pathophysiological disturbances which interfere with aerobic metabolism may occur at any stage in the oxygen cascade from atmospheric gas to the mitochondria, and there is no single monitoring modality that allows comprehensive determination of "the oxygenation". To facilitate early detection of tissue hypoxia (or hyperoxia) and to allow a goal directed therapy targeted at the underlying problem, the anesthesiologist and intensive care physician require a thorough understanding of the numerous determinants that influence cellular oxygenation. This article reviews the basic physiology of oxygen uptake and delivery to tissues as well as the options to monitor determinants of oxygenation at different stages from the alveolus to the cell.

Levosimendan inhibits release of reactive oxygen species in polymorphonuclear leukocytes in vitro and in patients with acute heart failure and septic shock: a prospective observational study

Introduction

Levosimendan is an extensively investigated inodilator showing also cardioprotective and antiinflammatory effects. The aim of our study was to explore the influence of levosimendan on polymorphonuclear leucocytes (PMN), a main source of reactive oxygen species, in vitro and in patients with acute heart failure or septic myocardial depression.

Methods

PMN isolated from healthy volunteers were incubated with levosimendan in vitro. After stimulation with N-formyl-Met-Leu-Phe (fMLP) or phorbol 12-myristate 13-acetate (PMA) respiratory burst was quantified using a fluorescent dye. Apoptosis and expression of cell adhesion molecules of PMN were measured by flow cytometry. For determination of in vivo effects patients with acute heart failure (n = 16) or septic cardiac failure (n = 9) receiving levosimendan treatment were enrolled consecutively. PMN were isolated to measure respiratory burst activity before treatment as well as one and two hours after initiation of levosimendan administration. Furthermore inflammatory, hemodynamic and renal function parameters were obtained.

Results

In vitro, levosimendan suppressed respiratory burst activity in fMLP or PMA stimulated PMN in a dose dependent manner by 30 ± 11% (P < 0.001) at 100 ng/mL and by 27 ± 17% (P < 0.001) at 1000 ng/mL respectively. Markers of apoptosis and PMN cell adhesion molecule expression remained unaffected by levosimendan treatment.

In vivo, levosimendan treatment for two hours resulted in a significant reduction of PMA stimulated oxidative burst by 45% (P < 0.01) and fMLP stimulated oxidative burst by 49% (P < 0.05) in patients with acute heart failure. In patients suffering from septic shock levosimendan treatment decreased oxidative burst activity in unstimulated, fMLP and PMA stimulated PMN by 48% (P < 0.05), 46% (P < 0.01) and 43% (P < 0.01) respectively.

Conclusions

Levosimendan appears to exert distinct immunomodulatory effects by decreasing oxidative burst activity of PMN. This property might contribute to the previously described cardioprotective effects of the drug.