Time-dependent cardioprotection with calcium antagonism and experimental studies with clevidipine in ischemic-reperfused pig hearts: part II

Therapeutic hypothermia for acute myocardial infarction: a narrative review of evidence from animal and clinical studies

Myocardial infarction (MI) is the leading cause of death from coronary heart disease and requires immediate reperfusion therapy with thrombolysis, primary percutaneous coronary intervention, or coronary artery bypass grafting. However, myocardial reperfusion therapy is often accompanied by cardiac ischemia/reperfusion (I/R) injury, which leads to myocardial injury with detrimental consequences. The causes of I/R injury are unclear, but are multifactorial, including free radicals, reactive oxygen species, calcium overload, mitochondria dysfunction, inflammation, and neutrophil-mediated vascular injury. Mild hypothermia has been introduced as one of the potential inhibitors of myocardial I/R injury. Although animal studies have demonstrated that mild hypothermia significantly reduces or delays I/R myocardium damage, human trials have not shown clinical benefits in acute MI (AMI). In addition, the practice of hypothermia treatment is increasing in various fields such as surgical anesthesia and intensive care units. Adequate sedation for anesthetic procedures and protection from body shivering has become essential during therapeutic hypothermia. Therefore, anesthesiologists should be aware of the effects of therapeutic hypothermia on the metabolism of anesthetic drugs. In this paper, we review the existing data on the use of therapeutic hypothermia for AMI in animal models and human clinical trials to better understand the discrepancy between perceived benefits in preclinical animal models and the absence thereof in clinical trials thus far.

The Current Role of Clevidipine in the Management of Hypertension

Acute hypertension, which may damage blood vessels, causes irreversible organ damage to the vasculature, central nervous system, kidney, and heart. Clevidipine, the first third-generation calcium channel antagonist approved by the Food and Drug Administration (FDA) in the past 20 years, is an ultra-short-acting calcium channel blocker that inhibits L-type calcium channels with high clearance and low distribution, can be rapidly metabolized into the corresponding inactive acid, and is rapidly hydrolyzed into inactive metabolites by esterase in arterial blood. Clevidipine is the same as nicardipine in that the main physiological effect is vasodilation and the main target is the arterial system, which has a limited effect on capacitor vessels. Unlike nitroglycerin, clevidipine has a limited effect on preload. In contrast to other direct-acting vasodilators, clevidipine has an ultra-short half-life due to metabolism by nonspecific blood and tissue esterases. Clevidipine trials conducted in adult populations have proven that it can rapidly control blood pressure in cardiac surgery situations and that adverse reactions to clevidipine are similar to those with other antihypertensive agents. In recent years, clinical trials have shown that clevidipine has excellent blood pressure-lowering capability in patients with acute neurological injury (hemorrhage, stroke, and subarachnoid and acute intracerebral hemorrhage), those  undergoing coronary artery bypass graft or spinal surgery, and in those with cerebral aneurysm/pheochromocytoma, acute heart failure, acute aortic syndromes, or renal insufficiency with severe hypertension, and it is equivalent to commonly used blood pressure-lowering medicines such as nicardipine or nitroglycerin. However, there is a lack of large-scale clinical trial data on the efficacy and safety of clevidipine in children during the perioperative period.

Pharmacological management of hypertensive emergencies and urgencies: focus on newer agents

INTRODUCTION

Hypertensive crises are categorized as hypertensive emergencies and urgencies depending on the presence of acute target-organ damage; the former are potentially life-threatening medical conditions, requiring urgent treatment under close monitoring. Although several short-acting intravenous antihypertensive agents are approved for this purpose, until recently little evidence from proper trials on the relative merits of different therapies was available.

AREAS COVERED

This article discusses in brief the pathophysiology, epidemiology and diagnostic approach of hypertensive crises and provides an extensive overview of established and emerging pharmacological agents for the treatment of patients with hypertensive emergencies and urgencies.

EXPERT OPINION

Agents such as sodium nitroprusside, nitroglycerin and hydralazine have been used for many years as first-line options for patients with hypertensive emergencies, although their potential adverse effects and difficulties in use were well known. With time, equally potent and less toxic alternatives, including nicardipine, fenoldopam, labetalol and esmolol are increasingly used worldwide. Recently, clevidipine, a third-generation dihydropyridine calcium-channel blocker with unique pharmacodynamic and pharmacokinetic properties was added to our therapeutic armamentarium and was shown in clinical trials to reduce mortality when compared with nitroprusside. In view of such evidence, a change in pharmacological treatment practices for hypertensive crises toward newer and safer agents is warranted.

Hypertensive emergencies: an update

PURPOSE OF REVIEW

Systemic hypertension (HTN) is a common medical condition affecting over 1 billion people worldwide. One to two percent of patients with HTN develop acute elevations of blood pressure (hypertensive crises) that require medical treatment. However, only patients with true hypertensive emergencies require the immediate and controlled reduction of blood pressure with an intravenous antihypertensive agent.

RECENT FINDINGS

Although the mortality from hypertensive emergencies has decreased, the prevalence and demographics of this disorder have not changed over the last 4 decades. Clinical experience and reported data suggest that patients with hypertensive urgencies are frequently inappropriately treated with intravenous antihypertensive agents, whereas patients with true hypertensive emergencies are overtreated with significant complications.

SUMMARY

Despite published guidelines, most patients with hypertensive crises are poorly managed with potentially severe outcomes.

Clevidipine : a state-of-the-art antihypertensive drug under the scope

INTRODUCTION

Clevidipine butyrate is the first intravenous antihypertensive drug to be approved by the FDA over the last decade. This medication is approved for use in the USA, Australia and New Zealand, but is still pending for approval in Europe. It is a new agent that might change the current management for severe acute hypertension in the critical care, emergency and perioperative areas.

AREAS COVERED

This systematic review summarizes the pharmacological and clinical characteristics of this third-generation dihydropyridine intravenous calcium channel blocker, and was done using the literature available from the first publication in 1999 up until now, including the pivotal trials that led to its approval.

EXPERT OPINION

This agent is arterially selective, has an ultrashort half-life, with no CYP-mediated interactions with other medications and is easily titratable. These characteristics place it in a unique category compared with other commonly used antihypertensives. Clevidipine butyrate reaches target systolic blood pressure in more than 90% of patients, within 30 min. It has a low incidence of adverse reactions and is generally well tolerated. The main goal of this review is to provide healthcare providers with a comprehensive appraisal of this promising medication.

Clevidipine for severe hypertension in patients with renal dysfunction: a VELOCITY trial analysis

Introduction. Acute and severe hypertension is common, especially in patients with renal dysfunction (RD). Clevidipine is a rapidly acting (t½∼1 min) intravenous (IV) dihydropyridine calcium-channel blocker metabolized by blood and tissue esterases and may be useful in patients with RD. The purpose of this analysis was to assess the safety and efficacy of clevidipine in patients with RD. Methods. VELOCITY, a multicenter open-label study of severe hypertension, enrolled 126 patients with persistent systolic blood pressure (SBP) >180 mmHg. Investigators pre-specified a SBP initial target range (ITR) for each patient to be achieved within 30 min. Blood pressure monitoring was by cuff. Clevidipine was infused via peripheral IV at 2 mg/h for at least 3 min, then doubled every 3 min as needed to a maximum of 32 mg/h (non-weightbased treat-to-target protocol). Per protocol, clevidipine was continued for at least 18 h (96 h maximum). RD was diagnosed and reported as an end-organ injury by the investigator and was defined as requiring dialysis or an initial creatinine >2.0 mg/dl. Primary endpoints were the percentage of patients within the ITR by 30 min and the percentage below the ITR after 3 min of clevidipine infusion. Results. Of the 24 patients with moderate to severe RD, most (13/24) were dialysis dependent. Forty-six percent were male, with mean age 51 >14 years; 63% were black and 96% had a hypertension history. Median time to achieve the ITR was 8.5 min. Almost 90% of patients reached the ITR in 30 min without evidence of overshoot and were maintained on clevidipine through 18 h. Most patients (88%) transitioned to oral antihypertensive therapy within 6 h of clevidipine termination. Conclusions. This report is the first demonstrating that clevidipine is safe and effective in RD complicated by severe hypertension. Prolonged infusion maintained blood pressure within a target range and allowed successful transition to oral therapy.

Clevidipine for the treatment of severe hypertension in adults

BACKGROUND

Intravenous antihypertensive agents are used when immediate control of blood pressure (BP) is required, including during the perioperative cardiac surgery period. Controlling postoperative BP is challenging because of the need to adequately reduce BP while maintaining appropriate end-organ perfusion. Clevidipine is an intravenous, ultra-short-acting, third-generation dihydropyridine calcium channel antagonist with selectivity for arteriolar vasodilatation. It is approved by the US Food and Drug Administration for the treatment of severe hypertension.

OBJECTIVE

This paper reviews the clinical pharmacology, pharmacokinetic and pharmacodynamic properties, tolerability, and clinical efficacy of clevidipine.

METHODS

To minimize selection bias, each author conducted an independent search for English-language publications indexed on MEDLINE and International Pharmaceutical Abstracts through January 2010 using the term clevidipine. All identified prospective, randomized and nonrandomized Phase III trials were included in the review.

RESULTS

Seven Phase III trials were identified in which clevidipine was compared with baseline, placebo, or other intravenous antihypertensive agents in the settings of severe hypertension (1 study), preoperative cardiac surgery (1), perioperative cardiac surgery (1), and postoperative cardiac surgery (4). In a multicenter, randomized, double-blind, placebo-controlled study of the efficacy of clevidipine in treating preoperative hypertension, the mean reduction from baseline in mean arterial pressure was 31.2% with clevidipine and 11.2% with placebo (P < 0.001). In a randomized, open-label, prospective study involving separate comparisons of clevidipine with nitroglycerin, sodium nitroprusside, and nicardipine, the median total AUC for digression in systolic BP from the predetermined target range differed significantly between clevidipine and nitroglycerin (4.14 vs 8.87 mm Hg . min/h; respectively, P < 0.001) and between clevidipine and sodium nitroprusside (4.37 vs 10.5 mm Hg . min/h; P = 0.003), but not between clevidipine and nicardipine (1.76 and 1.69 mm Hg . min/h). Another study found no significant difference in efficacy in controlling BP during the 3-hour study period between clevidipine and sodium nitroprusside (AUC for mean [SD] arterial pressure, 106 [25] and 101 [28] mm Hg . min/h, respectively). Adverse events in these studies included atrial fibrillation (13.0%-36.1% clevidipine vs 12.0% placebo), nausea (5.0%-21.0% vs 12.0%, respectively), fever (19.0% vs 13.7%), insomnia (12.0% vs 6.1%), and acute renal failure (9.0% vs 2.0%). In the studies reviewed, only 1 case of chest discomfort in the setting of severe hypertension was considered a serious adverse event related to clevidipine therapy.

CONCLUSION

In the Phase III trials reviewed, clevidipine was effective in controlling BP in the settings of perioperative cardiac surgery and severe hypertension and was associated with minimal adverse effects.

Intravenous clevidipine for management of hypertension

Hypertension remains one of the most prevalent diseases affecting our society, and its complications lead the list of causes of mortality all over the world. Most efforts to control the disease are unsuccessful, failing in at least two-thirds of affected patients, despite the availability of multiple drugs for its treatment. The limited number of medications available for aggressive management of hypertensive crises has intensified the search for novel drugs that can achieve a rapid decrease in blood pressure without increasing the possible complications. Clevidipine is a novel, vasculoselective, dihydropyridine calcium channel blocker characterized by a very fast onset and offset of action. Metabolism of clevidipine does not occur in the liver or kidneys, and thus there are no restrictions to using clevidipine in patients with hepatic or renal dysfunction. This agent has been widely used to reduce blood pressure when oral therapy is not appropriate, and its use in the perioperative setting has been shown to be beneficial. This manuscript reviews the key characteristics of clevidipine and its role in the management of acute hypertension.

RNAi targeting ryanodine receptor 2 protects rat cardiomyocytes from injury caused by simulated ischemia-reperfusion

The effects of a small interfering RNA targeting ryanodine receptor 2 (si-Ryr2) on cardiomyocytes injury following a simulated ischemia-reperfusion (I/R) were investigated. Pretreated with si-Ryr2 or ryanodine, primary cultures of neonatal rat cardiomyocytes were subjected to a protocol of simulated I/R. Compared with control, the cytosolic Ca(2+) concentration ([Ca(2+)](i)) and the generation of reactive oxygen species (ROS) was significantly augmented after I/R. Concomitant with these, cell injury assessed by Annexin V/PI staing, mitochondria membrane potential (DeltaPsim) and the leakage of lactic dehydrogenase (LDH) and creatine phosphokinase (CPK) were aggravated. Si-Ryr2 treatment reduced [Ca(2+)](i) and ROS generation and protected the cardiomyocytes from subsequent I/R injury, as evidenced by stable DeltaPsim and decreased Annexin V(+) PI(-) staing and enzymes release. Moreover, si-Ryr2 exerted more effective protection on I/R injury compared to ryanodine. The present study demonstrated for the first time that in neonatal cardiomyocytes, si-Ryr2 reduces cell death associated with attenuating [Ca(2+)](i) and ROS production. Furthermore, we attempt to speculate that si-Ryr2 excel ryanodine in Ryr2 function research of cardioprotection.

Perioperative hypertension: a review of current and emerging therapeutic agents

Perioperative hypertension is a common problem encountered by anesthesiologists, surgeons, internists, and intensivists. Surprisingly, no randomized, placebo-controlled studies exist that show that the treatment of perioperative hypertension reduces morbidity or mortality. Nevertheless, perioperative hypertension requires careful management. While sodium nitroprusside and nitroglycerin are commonly used to treat these conditions, these agents are less than ideal. Intravenous beta blockers and calcium channel blockers have particular appeal in this setting.

Clevidipine Butyrate Injectable Emulsion

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Treatment of acute severe hypertension: current and newer agents

Approximately 72 million people in the US experience hypertension. Worldwide, hypertension may affect as many as 1 billion people and be responsible for approximately 7.1 million deaths per year. It is estimated that approximately 1% of patients with hypertension will, at some point, develop a hypertensive crisis. Hypertensive crises are further defined as either hypertensive emergencies or urgencies, depending on the degree of blood pressure elevation and presence of end-organ damage. Immediate reduction in blood pressure is required only in patients with acute end-organ damage (i.e. hypertensive emergency) and requires treatment with a titratable, short-acting, intravenous antihypertensive agent, while severe hypertension without acute end-organ damage (i.e. hypertensive urgency) is usually treated with oral antihypertensive agents. The primary goal of intervention in a hypertensive crisis is to safely reduce blood pressure. The appropriate therapeutic approach of each patient will depend on their clinical presentation. Patients with hypertensive emergencies are best treated in an intensive care unit with titratable, intravenous, hypotensive agents. Rapid-acting intravenous antihypertensive agents are available, including labetalol, esmolol, fenoldopam, nicardipine and sodium nitroprusside. Newer agents, such as clevidipine and fenoldopam, may hold considerable advantages to other available agents in the management of hypertensive crises. Sodium nitroprusside is an extremely toxic drug and its use in the treatment of hypertensive emergencies should be avoided. Similarly, nifedipine, nitroglycerin and hydralazine should not to be considered first-line therapies in the management of hypertensive crises because these agents are associated with significant toxicities and/or adverse effects.

Perioperative hypertension management

Perioperative hypertension is commonly encountered in patients that undergo surgery. While attempts have been made to standardize the method to characterize the intraoperative hemodynamics, these methods still vary widely. In addition, there is a lack of consensus concerning treatment thresholds and appropriate therapeutic targets, making absolute recommendations about treatment difficult. Nevertheless, perioperative hypertension requires careful management. When treatment is necessary, therapy should be individualized for the patient. This paper reviews the pharmacologic agents and strategies commonly used in the management of perioperative hypertension.

New therapeutic perspectives with clevidipine: an ultra-short-acting intravenous Ca2+channel blocker

Intravenous antihypertensive agents are used in clinical situations in which the immediate, precise control of blood pressure is a clinical necessity. Clevidipine is a new, vascular-selective, dihyrdopyridine Ca(2+) channel blocker, which exerts its hemodynamic effects through selective arterial vasodilation without effects on the venous circulation. Because it is a potent coronary vasodilator, reduction in mean arterial pressure does not impair coronary perfusion. The unique properties of clevidipine include an ultra-short pharmacodynamic duration of action and a half-life after intravenous administration of approximately 2 min, resulting in very rapid onset and offset of antihypertensive effects. In clinical trials performed in patients undergoing cardiac surgery, clevidipine proved superior to nitroprusside and nitroglycerin in maintaining blood pressure within predetermined ranges during the perioperative period. Its safety profile is comparable to nicardipine and nitroglycerin and, in one study, was associated with reduced 30-day mortality compared with nitroprusside. Clevidipine constitutes a useful addition to available intravenous agents and could prove particularly valuable in circumstances that require the ability to rapidly terminate the blood pressure-lowering effects of administered agents.

Hypertensive crises: challenges and management

Hypertension affects > 65 million people in the United States and is one of the leading causes of death. One to two percent of patients with hypertension have acute elevations of BP that require urgent medical treatment. Depending on the degree of BP elevation and presence of end-organ damage, severe hypertension can be defined as either a hypertensive emergency or a hypertensive urgency. A hypertensive emergency is associated with acute end-organ damage and requires immediate treatment with a titratable short-acting IV antihypertensive agent. Severe hypertension without acute end-organ damage is referred to as a hypertensive urgency and is usually treated with oral antihypertensive agents. This article reviews definitions, current concepts, common misconceptions, and pitfalls in the diagnosis and management of patients with acutely elevated BP as well as special clinical situations in which BP must be controlled.

Current diagnosis and management of hypertensive emergency

The appropriate and timely evaluation and treatment of patients with severely elevated blood pressure is essential to avoid serious adverse outcomes. Most importantly, the distinction between a hypertensive emergency (crisis) and urgency needs to be made. A sudden elevation in systolic (SBP) and/or diastolic blood pressure (DBP) that is associated with acute end organ damage (cardiovascular, cerebrovascular, or renal) is defined as a hypertensive crisis or emergency. In contrast, acute elevation in SBP and/or DBP not associated with evidence of end organ damage is defined as hypertensive urgency. In patients with a hypertensive emergency, blood pressure control should be attained as expeditiously as possible with parenteral medications to prevent ongoing and potentially permanent end organ damage. In contrast, with hypertensive urgency, blood pressure control can be achieved with the use of oral medications within 24-48 hours. This paper reviews the management of hypertensive emergencies.

Pharmacodynamic, Pharmacokinetic and Clinical Effects of Clevidipine, an Ultrashort-Acting Calcium Antagonist for Rapid Blood Pressure Control

Clevidipine is an ultrashort-acting vasoselective calcium antagonist under development for short-term intravenous control of blood pressure. Studies in animals, healthy volunteers and patients have demonstrated the vascular selectivity and rapid onset and offset of antihypertensive action of clevidipine, a synthetic 1,4-dihydropyridine that inhibits L-type calcium channels. Clevidipine has a high clearance (0.05 L/min/kg) and is rapidly hydrolyzed to inactive metabolites by esterases in arterial blood. Its half-life in patients undergoing cardiac surgery is less than one min. Unlike sodium nitroprusside, a drug commonly used for the short-term control of blood pressure, which dilates both arterioles and veins, clevidipine reduces blood pressure through a selective effect on arterioles. As documented in animals and in cardiac surgical patients, clevidipine reduces peripheral resistance without any undesirable effect on cardiac filling pressure. It increases stroke volume and cardiac output. In anesthetized patients undergoing cardiac surgery clevidipine, unlike sodium nitroprusside, does not increase heart rate. In addition of having a favorable hemodynamic profile, suitable for rapid control of blood pressure, clevidipine protects against ischemia/reperfusion injuries, which are not uncommon during major surgery. In anesthetized pigs, clevidipine reduced infarct size after 45 min-long myocardial ischemia by 40%. In rats, renal function and splanchnic blood flow were better maintained when blood pressure was reduced with clevidipine than with sodium nitroprusside. Clevidipine was well tolerated in Phases I and II of clinical trials that included more than 300 individuals/patients. Since there are no known compounds with similar pharmacodynamic and pharmacokinetic properties in clinical development, it is anticipated that clevidipine, a compound tailored to the needs of anesthesiologists, has the potential to become a drug of choice for controlling blood pressure during surgical procedures.

Failure to demonstrate myocardial protective effects of the ultra short-acting calcium antagonist clevidipine in a closed-chest reperfusion porcine model

Restoration of myocardial perfusion is essential in acute myocardial infarction for the salvaging of myocardial tissue. However, reperfusion per se can provoke myocardial necrosis within the jeopardized tissue. Yet, no intervention has been successfully applied to the clinical situation in this matter. Clevidipine, an ultra-short acting calcium antagonist, has, in open-chest animal models, shown to reduce the extent of reperfusion injury. In the present study we intended to reproduce those findings in a closed-chest porcine model with a clinically applicable set up. Pigs were subjected to balloon occlusion of the left anterior descending coronary artery (LAD) for 45 minutes. During 25 minutes, starting 1 minute prior to reperfusion, clevidipine, Intralipid, or saline was infused antegradely into the endangered myocardium. As no significant effects on infarct size were achieved, the model was modified. In a second phase, different anesthesias were evaluated addressing the same issue. Nonetheless no significant effects on infarct size were observed. Different techniques of occluding LAD, in an open-chest model, were investigated in a third phase, and revealed no significant differences between the techniques. However, when comparing all the closed- versus open-chest models, significant reduction in infarct size by the use of clevidipine was only obtained in the open-chest models. We could not demonstrate any significant myocardial protective effect with clevidipine in our porcine, closed-chest, acute infarct, and reperfusion model. However, in a modified open-chest model we obtained significant reduction in infarct size. Further studies are required to explain the discrepancies.