Nitroprusside-related cyanide poisoning. Time (long past due) for urgent, effective interventions

Catecholamine-induced hypertensive crises: current insights and management

Phaeochromocytomas and paragangliomas (PPGLs) release catecholamines leading to catecholamine-induced hypertensive (CIH) crises, with blood pressure greater than or equal to 180/120 mm Hg. CIH crises can be complicated by tachyarrhythmias, hypotension, or life-threatening target organ damage while treatment remains undefined, often requiring co-management between endocrinologists and cardiologists. Furthermore, biochemical diagnosis of a PPGL as a cause of a CIH crisis can be difficult to identify or confounded by comorbid conditions, potentially resulting in misdiagnosis. Here, we combine relevant evidence, 60 years of collective clinical experience, insights derived from assessing over 2600 patients with PPGL, and supplementary outcomes from 100 patients (treated at the National Institutes of Health) with a CIH crisis to inform diagnosis and treatment of CIH crises. Recognising that disparities exist between availability, cost, and familiarity of various agents, flexible approaches are delineated allowing for customisation, given institutional availability and provider preference. A CIH crisis and its complications are readily treatable with available drugs, with effective intervention defining an avenue for mitigating consequent morbidity and mortality in patients with PPGL.

Pharmacological management of malignant hypertension

INTRODUCTION

According to current guidelines, malignant hypertension is one of the emergencies in hypertension. The definition requires the presence of bilateral retinal hemorrhages or exudates, with or without papilledema, acute heart failure and acute deterioration in renal function in severe hypertension. Patients with malignant hypertension are characterized by pronounced target organ damage, including structural and functional cardiac abnormalities and renal insufficiency.

AREAS COVERED

Knowledge of the available treatment options is extremely important as we know that we only have a limited time to reduce blood pressure. There are only four drugs dedicated to immediate blood pressure lowering in patients with malignant hypertension, including 'first-line' and alternative drugs. Our review aims to discuss all those drugs and gives practical suggestions on how to properly use them.

EXPERT COMMENTARY

The decision of which drug to use depends on numerous factors including the clinical indications, pharmacokinetics, toxicity and drug interactions. Furthermore, frequently, more than one of the recommended drugs is required for the successful lowering of the patient's blood pressure.

Cardiovascular dysfunction associated with neurodegeneration in an experimental model of Parkinson's disease

Patients with Parkinson's disease (PD) exhibit both motor and non-motor symptoms. Among the non-motor symptoms, cardiovascular autonomic dysfunction is frequently observed. Here, we evaluated baroreflex function, vascular reactivity and neuroanatomical changes in brainstem regions involved in the neural control of circulation in the 6-hydroxydopamine (6-OHDA) model of PD. Male Wistar rats received a bilateral injection of 6-OHDA or vehicle into the striatum. After 61days, baroreflex function and vascular reactivity were assessed. The 6-OHDA and vehicle groups showed similar increases in mean arterial pressure (MAP) in response to phenylephrine (PE). However, the bradycardia observed in the vehicle group was blunted in the 6-OHDA-treated rats. Injection of sodium nitroprusside (SNP) decreased hypotension, tachycardia and vascular relaxation in 6-OHDA-treated rats. Bilateral intrastriatal 6-OHDA led to massive degeneration of tyrosine hydroxylase (TH)-immunoreactive neurons in the substantia nigra and to reductions in the numbers of A1/C1 and A5 catecholaminergic neurons while sparing A2 neurons within the nucleus of the solitary tract (NTS). 6-OHDA-treated rats also showed decreases in Phox2b-expressing neurons in the NTS and in choline acetyltransferase (ChAT) immunoreactivity in the nucleus ambiguus. Altogether, our data suggest that this model of PD includes neuroanatomical and functional changes that lead to cardiovascular impairment.

Endothelial nitric oxide synthase in the microcirculation

Endothelial nitric oxide synthase (eNOS, NOS3) is responsible for producing nitric oxide (NO)--a key molecule that can directly (or indirectly) act as a vasodilator and anti-inflammatory mediator. In this review, we examine the structural effects of regulation of the eNOS enzyme, including post-translational modifications and subcellular localization. After production, NO diffuses to surrounding cells with a variety of effects. We focus on the physiological role of NO and NO-derived molecules, including microvascular effects on vessel tone and immune response. Regulation of eNOS and NO action is complicated; we address endogenous and exogenous mechanisms of NO regulation with a discussion of pharmacological agents used in clinical and laboratory settings and a proposed role for eNOS in circulating red blood cells.

Poly-s-nitrosated albumin as a safe and effective multifunctional antitumor agent: characterization, biochemistry and possible future therapeutic applications

Nitric oxide (NO) is a ubiquitous molecule involved in multiple cellular functions. Inappropriate production of NO may lead to disease states. To date, pharmacologically active compounds that release NO within the body, such as organic nitrates, have been used as therapeutic agents, but their efficacy is significantly limited by unwanted side effects. Therefore, novel NO donors with better pharmacological and pharmacokinetic properties are highly desirable. The S-nitrosothiol fraction in plasma is largely composed of endogenous S-nitrosated human serum albumin (Mono-SNO-HSA), and that is why we are testing whether this albumin form can be therapeutically useful. Recently, we developed SNO-HSA analogs such as SNO-HSA with many conjugated SNO groups (Poly-SNO-HSA) which were prepared using chemical modification. Unexpectedly, we found striking inverse effects between Poly-SNO-HSA and Mono-SNO-HSA. Despite the fact that Mono-SNO-HSA inhibits apoptosis, Poly-SNO-HSA possesses very strong proapoptotic effects against tumor cells. Furthermore, Poly-SNO-HSA can reduce or perhaps completely eliminate the multidrug resistance often developed by cancer cells. In this review, we forward the possibility that Poly-SNO-HSA can be used as a safe and effective multifunctional antitumor agent.

Chemical and metabolomic screens identify novel biomarkers and antidotes for cyanide exposure

Exposure to cyanide causes a spectrum of cardiac, neurological, and metabolic dysfunctions that can be fatal. Improved cyanide antidotes are needed, but the ideal biological pathways to target are not known. To understand better the metabolic effects of cyanide and to discover novel cyanide antidotes, we developed a zebrafish model of cyanide exposure and scaled it for high-throughput chemical screening. In a screen of 3120 small molecules, we discovered 4 novel antidotes that block cyanide toxicity. The most potent antidote was riboflavin. Metabolomic profiling of cyanide-treated zebrafish revealed changes in bile acid and purine metabolism, most notably by an increase in inosine levels. Riboflavin normalizes many of the cyanide-induced neurological and metabolic perturbations in zebrafish. The metabolic effects of cyanide observed in zebrafish were conserved in a rabbit model of cyanide toxicity. Further, humans treated with nitroprusside, a drug that releases nitric oxide and cyanide ions, display increased circulating bile acids and inosine. In summary, riboflavin may be a novel treatment for cyanide toxicity and prophylactic measure during nitroprusside treatment, inosine may serve as a biomarker of cyanide exposure, and metabolites in the bile acid and purine metabolism pathways may shed light on the pathways critical to reversing cyanide toxicity.

The NO donor sodium nitroprusside: evaluation of skeletal muscle vascular and metabolic dysfunction

The nitric oxide (NO) donor sodium nitroprusside (SNP) may promote cyanide-induced toxicity and systemic and/or local responses approaching maximal vasodilation. The hypotheses were tested that SNP superfusion of the rat spinotrapezius muscle exerts 1) residual impairments in resting and contracting blood flow, oxygen utilization (VO(2)) and microvascular O(2) pressure (PO(2)mv); and 2) marked hypotension and elevation in resting PO(2)mv. Two superfusion protocols were performed: 1) Krebs-Henseleit (control 1), SNP (300 μM; a dose used commonly in superfusion studies) and Krebs-Henseleit (control 2), in this order; 2) 300 and 1200 μM SNP in random order. Spinotrapezius muscle blood flow (radiolabeled microspheres), VO(2) (Fick calculation) and PO(2)mv (phosphorescence quenching) were determined at rest and during electrically-induced (1 Hz) contractions. There were no differences in spinotrapezius blood flow, VO(2) or PO(2)mv at rest and during contractions pre- and post-SNP condition (control 1 and control 2; p>0.05 for all). With regard to dosing, SNP produced a graded elevation in resting PO(2)mv (p<0.05) with a reduction in mean arterial pressure only at the higher concentration (p<0.05). Contrary to our hypotheses, skeletal muscle superfusion with the NO donor SNP (300 μM) improved microvascular oxygenation during the transition from rest to contractions (PO(2)mv kinetics) without precipitating residual impairment of muscle hemodynamic or metabolic control or compromising systemic hemodynamics. These data suggest that SNP superfusion (300 μM) constitutes a valid and important tool for assessing the functional roles of NO in resting and contracting skeletal muscle function without incurring residual alterations consistent with cyanide accumulation and poisoning.

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.

Syntheses, structures, and photochemistry of manganese nitrosyls derived from designed Schiff base ligands: potential NO donors that can be activated by near-infrared light

Two manganese nitrosyls, namely, [Mn(SBPy(3))(NO)](ClO(4))(2) (1) and [Mn(SBPy(2)Q)(NO)](ClO(4))(2) (2), have been synthesized by using designed pentadentate Schiff base ligands N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-aldimine (SBPy(3)) and N,N-bis(2-pyridyl methyl)amine-N-ethyl-2-quinoline-2-aldimine (SBPy(2)Q). Reaction of NO(g) with [Mn(SBPy(3))(MeOH)](ClO(4))(2) and [Mn(SBPy(2)Q)(EtOH)](ClO(4))(2) in MeCN affords 1 and 2, respectively, in good yields. Narrow-width peaks in the (1)H NMR spectra and strong nu(NO) at 1773 cm(-1) (of 1) and 1759 cm(-1) (of 2) confirm a strongly coupled {low-spin Mn(II)-NO*}formulation for both these {Mn-NO}(6) nitrosyls. In MeCN, 1 exhibits two strong absorption bands with lambda(max) at 500 and 720 nm. These bands red shift to 550 and 785 nm in case of 2 because of substitution of the pyridyl-imine moiety of SBPy(3) with quinolyl-imine moiety in the SBPy(2)Q ligand frame. Exposure of solutions 1 and 2 to near-infrared (NIR) light (780 nm, 5 mW) results in rapid bleaching of the orange and fuchsia solutions, and free NO is detected in the solutions by an NO-sensitive electrode. The high quantum yield values (Phi) of 1 (0.580 +/- 0.010, lambda(irr) = 550 nm, MeCN) and 2 (0.434 +/- 0.010, lambda(irr) = 550 nm, MeCN) and in particular their sensitivity to NIR light of 800-950 nm range strongly suggest that these designed manganese nitrosyls could be used as NIR light-triggered NO donors.

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.

Evaluation of Sodium Nitroprusside Toxicity in Pediatric Cardiac Surgical Patients

Background:

Sodium nitroprusside (SNP) is often used in postoperative pediatric cardiac surgical patients. Cyanide toxicity may occur with the use of SNP. There is a paucity of literature describing dosing parameters or physical signs and symptoms of toxicity with SNP.

Objective:

To determine the incidence of cyanide toxicity in postoperative pediatric cardiac surgical patients treated with SNP and identify dosing parameters and physical signs and symptoms that may predict elevated cyanide concentrations.

Methods:

Medical records of patients who received SNP in the pediatric cardiac intensive care unit from January 2002 through December 2002 were identified and evaluated for cyanide and thiocyanate levels, dosing, and signs and symptoms of toxicity. Patients were included if they had received SNP after cardiac surgery, were 18 years of age or less, and had at least one cyanide or thiocyanate level determined while receiving therapy. Patients were excluded if they had received sodium thiosulfate. The Mann-Whitney U test was used to determine significant differences in mean dose, duration of infusion, renal function, serum lactate, and acid-base status between groups with elevated or nonelevated levels. Logistic regression and receiver operator curve were used to determine variables associated with elevated levels. Relationships between signs and symptoms of toxicity and elevated levels were evaluated with Fisher's exact test.

Results:

Cyanide concentrations were in the toxic range in 7 of 63 (11%) patients. Patients with elevated concentrations had significantly higher mean dose, cumulative dose, and acid-base excess values. Elevated cyanide levels were independently predicted by mean dose, cumulative dose, and acid-base excess values, and a dose of 1.8 μg/kg/min predicted an elevated cyanide concentration with 89% sensitivity and 88% specificity. Adverse events were not reliable predictors of elevated cyanide levels.

Conclusions:

Mean dose of SNP is the best predictor of elevated cyanide levels. Adverse events commonly associated with cyanide toxicity may not be reliable indicators of elevated cyanide concentrations.

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.

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.

Cardiopulmonary Bypass, Hemolysis, and Nitroprusside-Induced Cyanide Production

BACKGROUND

Cyanide toxicity is a complication of sodium nitroprusside administration. Cardiac surgery may increase the risk of cyanide toxicity, because hemolysis during cardiopulmonary bypass (CPB) may catalyze the release of free cyanide from sodium nitroprusside.

METHODS

We obtained serial blood specimens from 25 cardiac surgical patients during CPB. Plasma specimens were analyzed for free hemoglobin concentration and ability to generate free cyanide anion upon exposure to sodium nitroprusside.

RESULTS

Hemolysis based on plasma-free hemoglobin concentration increased over time during CPB at an average rate of 0.27 mg x dL(-1) x min(-1) (P < 0.001). The concentration of free cyanide generated by the addition of sodium nitroprusside to the plasma samples was directly related to the plasma-free hemoglobin concentration (P < 0.001).

CONCLUSION

CPB-associated hemolysis and free hemoglobin release accelerated the immediate release of free cyanide from sodium nitroprusside. These in vitro findings suggest that cardiac surgical patients may be at increased risk of cyanide toxicity in response to the perioperative administration of sodium nitroprusside.

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.

Exploring an Optimum Intra/Postoperative Management Strategy for Acute Hypertension in the Cardiac Surgery Patient

An estimated 50% of patients undergoing routine cardiac surgery require intravenous antihypertensive therapy to manage life-threatening arterial bleeding, myocardial ischemia, or cardiac failure in the perioperative period. Managing hypertension in this setting can be challenging because of the need to reduce blood pressure while maintaining adequate end organ perfusion. Hypotensive episodes can increase the risk of cardiac complications and end organ hypoperfusion, particularly in patients whose underlying cardiovascular disease has altered autoregulation of blood flow. To decrease the risk of hypertensive or hypotensive episodes, blood pressure is monitored continuously, and short-acting intravenous antihypertensive agents are administered in an effort to target a mean arterial pressure generally within 20% of the patient's baseline value. Efforts to optimize end organ perfusion and avoid recognized adverse drug effects may influence the choice of antihypertensive agents. The ideal agent for postoperative hypertension should have a rapid onset of action, be highly vascular selective, and be rapidly reversible. In addition, it should be safe, with little risk of overshoot hypotension or adverse drug reaction. Precise management of arterial pressure in the perioperative period has the potential to improve clinical outcome by avoiding hypotensive episodes, ensuring adequate end organ perfusion, decreasing the risk of adverse drug effects, and serving as a bridge to definitive long-term therapy for essential hypertension.

Toxicology in the critically ill patient

Intoxications present in many forms including: known drug overdose or toxic exposure, illicit drug use, suicide attempt, accidental exposure, and chemical or biological terrorism. A high index of suspicion and familiarity with toxidromes can lead to early diagnosis and intervention in critically ill, poisoned patients. Despite a paucity of evidence-based information on the management of intoxicated patients, a rational and systematic approach can be life saving.

Clinical review: the management of hypertensive crises

Hypertension is an extremely common clinical problem, affecting approximately 50 million people in the USA and approximately 1 billion individuals worldwide. Approximately 1% of these patients will develop acute elevations in blood pressure at some point in their lifetime. A number of terms have been applied to severe hypertension, including hypertensive crises, emergencies, and urgencies. By definition, acute elevations in blood pressure that are associated with end-organ damage are called hypertensive crises. Immediate reduction in blood pressure is required only in patients with acute end-organ damage. This article reviews current concepts, and common misconceptions and pitfalls in the diagnosis and management of patients with acutely elevated blood pressure.

Nitric oxide-releasing drugs

Pharmacological compounds that release nitric oxide (NO) have been useful tools for evaluating the broad role of NO in physiology and therapeutics. NO deficiency has been implicated in the genesis and evolution of several disease states. Both medical needs and commercial opportunities have fostered attempts to modulate NO in the human body for therapeutic gain. Strategies for NO modulation encompass antiinflammatory, sexual dysfunction, and cardiovascular indications. Apart from newly developed drugs, several commonly used cardiovascular drugs exert their beneficial action, at least in part, by modulating the NO pathway. This review discusses the fundamental pharmacological properties and mechanisms of action of NO-releasing drugs. Some of these compounds may enter in the clinical arena providing important therapeutic benefits in human diseases.

Current concepts in the management of hypertensive crisis: emergencies and urgencies

Hypertensive emergencies and hypertensive urgencies represent a large percentage of major medical emergencies and have the potential of producing serious organ damage or death if not treated promptly and selectively. Several classifications of antihypertensive agents are discussed, with emphasis on selecting agents appropriate for patients' hypertension manifestations and comorbid situations. Epidemiology and evaluation of hypertension, as well as common pharmacokinetics of several common and new oral and parenteral antihypertensive agents, are described. Special nursing considerations of medication administration and gerontology concepts are included.

The diagnosis and management of hypertensive crises

Severe hypertension is a common clinical problem in the United States, encountered in various clinical settings. Although various terms have been applied to severe hypertension, such as hypertensive crises, emergencies, or urgencies, they are all characterized by acute elevations in BP that may be associated with end-organ damage (hypertensive crisis). The immediate reduction of BP is only required in patients with acute end-organ damage. Hypertension associated with cerebral infarction or intracerebral hemorrhage only rarely requires treatment. While nitroprusside is commonly used to treat severe hypertension, it is an extremely toxic drug that should only be used in rare circumstances. Furthermore, the short-acting calcium channel blocker nifedipine is associated with significant morbidity and should be avoided. Today, a wide range of pharmacologic alternatives are available to the practitioner to control severe hypertension. This article reviews some of the current concepts and common misconceptions in the management of patients with acutely elevated BP.

Diagnosis and management of hypertensive emergencies

It has been estimated that approximately 600,000 to 800,000 Americans will develop a hypertensive crisis (Calhoun and Oparil, 1990). Although such numbers represent only about 1% of the estimated 60 million Americans with hypertension, hypertensive crisis often constitutes a major medical emergency, necessitating a focused, assertive, and reasoned therapeutic intervention. When such patients are seen in the emergency department or in a physician's office with a critical elevation in blood pressure (BP), appropriate and efficacious management is essential to avoid catastrophic injury to vital target organs, including the central nervous system, the heart, and the kidneys. Delays in initiating effective therapy or, equally important, overzealous therapy leading to a too-rapid reduction in BP can produce severe complications involving these target organs. This article reviews the spectrum of clinical syndromes that comprise hypertensive emergencies, highlighting 2 to illustrate the complexities of clinical presentation and management. The newly advocated treatment guidelines based on the category of acute severe hypertension (including asymptomatic hypertensive urgencies) are also considered, as are therapeutic strategies utilizing currently available antihypertensive agents.

Treatment of hypertension in the perioperative patient

OBJECTIVE

To review studies and drug therapy relating to the treatment of hypertension in perioperative patients.

DATA SOURCES

Articles were selected from a MEDLINE search (1966-August 1998), and several textbooks on hypertension and surgery were reviewed. In addition, bibliographies of all articles and textbook chapters were studied for articles not found in the computerized searches.

STUDY SELECTION

Clinical studies involving hypertension in the perioperative setting were included. The initial search was limited to studies conducted in humans and published in English.

DATA EXTRACTION

Information regarding drug therapy was reviewed and guidelines were constructed for managing surgical patients with acute blood pressure elevations.

DATA SYNTHESIS

Although nitroprusside and nitroglycerin, with their short onset of action and duration of effect, are indicated for hypertensive emergencies, a variety of agents are available for hypertensive urgencies. An algorithm that can be used as a template for the development of intrainstitutional guidelines is provided.

CONCLUSIONS

Due to the scarcity of comparative trials, decisions involving agents for the treatment of perioperative hypertension must often be made based on combined efficacy, toxicity, cost, and convenience considerations.

Tailored therapy using dobutamine and nitroglycerin in advanced heart failure

In 29 patients with advanced heart failure, therapy tailored to hemodynamic goals was attempted using an initial infusion of dobutamine and nitroglycerin (the latter in those with pulmonary hypertension) followed by escalating doses of oral vasodilators. In the 23 patients who were weaned from inodilator therapy, significant improvements in hemodynamic parameters and a low 90-day hospital readmission rate were documented.

Intravenous nicardipine in the treatment of postoperative arterial hypertension

BACKGROUND

Calcium entry blockers are commonly used in the management of postoperative hypertension. The hemodynamic and blood gas effects of nicardipine, a dihydropyridine derivative available intravenously, were studied in patients after abdominal aortic surgery.

METHODS

Sixteen patients (66 +/- 8 years) who developed arterial hypertension (mean arterial pressure, > 90 mmHg) after abdominal aortic aneurysm reconstruction were studied. Fourteen patients had already been treated with a sodium nitroprusside infusion, the doses of which were maintained constant (mean dose: 1.42 +/- 1.04 micrograms/kg/min). Hemodynamic and blood gas data were collected at baseline, 15 minutes, and 45 minutes after a slow bolus administration of 3 to 5 mg of nicardipine.

RESULTS

After the nicardipine administration, mean arterial pressure decreased from 101 +/- 11 to 83 +/- 11 mmHg (p < 0.001), and the cardiac index acutely increased from 3.96 +/- 0.74 to 4.57 +/- 0.83 L/min/m2 (p < 0.05). Systemic vascular resistance significantly decreased. There were no significant changes in heart rate, stroke volume, cardiac filling pressures, pulmonary artery pressures, pulmonary vascular resistance, left ventricular stroke work, or right ventricular stroke work. One patient developed acute pulmonary edema, associated with a dramatic increase in cardiac filling pressures, and electrocardiographic signs of myocardial ischemia. Nicardipine administration was also associated with an acute reduction in Pao2 from 85.0 +/- 12.1 mmHg to 70.3 +/- 9.2 mmHg (p < 0.001), associated with an increase in venous admixture from 21.7% +/- 3.2% to 28.0% +/- 5.2% (p < 0.01). Oxygen delivery increased moderately and oxygen extraction decreased, but oxygen consumption was unchanged.

CONCLUSION

This study confirms the excellent efficacy of nicardipine in the management of postoperative hypertension, but underlines the risk of poor cardiac tolerance in patients after major surgery. Although oxygen delivery to the cells is usually well preserved, nicardipine can also significantly after blood oxygenation by increasing ventilation/perfusion mismatch.

Randomized, prospective trial of fenoldopam vs sodium nitroprusside in the treatment of acute severe hypertension. Fenoldopam Study Group

OBJECTIVE

To compare the safeties and efficacies of IV fenoldopam (FNP) vs sodium nitroprusside (NTP) in severe acute hypertension.

METHODS

A prospective, randomized, open-label, multicenter international trial, at 24 academic medical centers, was conducted. The participants were adult patients (21-80 years of age) who had supine diastolic blood pressures (DBPs) > or = 120 mm Hg, were capable of written informed consent, and did not have selected exclusion criteria. The subjects were randomized to either FNP or NTP therapy; DBP was titrated to 95-110 mm Hg, or a maximum reduction of 40 mm Hg for very high pressures. Infusions were maintained for at least six hours, then the patients were weaned off the IV therapy and oral medication was started. Measurements included BP, heart rate, and duration of study drug infusion and frequency of side effects or complications.

RESULTS

A total of 183 patients (90 FNP, 93 NTP) were enrolled. Fifteen patients from each arm were excluded from efficacy analysis due to protocol violation. There was no significant difference in baseline characteristics. The two antihypertensive agents were equivalent in controlling and maintaining DBP. Systolic blood pressure (SBP) was reduced to a slightly greater degree for the NTP-treated patients during the initial (0.5-1-hr) study period, and both SBP and DBP were reduced more for the FNP-treated patients in the subset receiving infusions during the 12-24-hour period. The adverse effect profiles of the drugs were similar, as were the times to achieve target pressure, with no clinically relevant difference.

CONCLUSIONS

For patients who had acute severe hypertension, FNP and NTP were equivalent in terms of efficacy and acute adverse events. Because of a unique mechanism of action, FNP may have advantages in selected subsets of patients. Further studies may be indicated in patient populations with pure "hypertensive emergencies."

Sodium nitroprusside: twenty years and counting

SNP remains an effective, reliable, and commonly used drug for the rapid reduction of significant arterial hypertension regardless of the etiology, for afterload reduction in the face of low CO when blood volume is normal or increased, and for intraoperative induced hypotension. After establishing indwelling arterial monitoring, an initial infusion rate of 0.3-0.5 micrograms.kg-1.min-1 is begun with titration as needed up to 2.0 micrograms.kg-1.min-1. Higher rates for brief periods of time (10 min) are acceptable. The use of alternative drugs to reduce the dose or shorten the duration of infusion should be considered when the 2.0 micrograms.kg-1.min-1 range is exceeded (Table 1). SNP should not be used by individuals unfamiliar with its potency and metabolic pathways, as the many reports of adverse reactions testify. Careful attention to infusion rates, particularly in patients at risk for depleted thiosulfate stores, is mandatory, and the use of other drugs in conjunction with or instead of SNP should always be considered. As with many therapeutic interventions, SNP requires careful administration to appropriately selected patients by a clinician who knows its inherent hazards. Despite its toxicity, SNP is popular because it is often the most (in some cases, the only) effective drug in some difficult clinical circumstances.

The role of serotonin blockers in cardiac anesthesia

In the complex setting of cardiac surgery and cardiopulmonary bypass, several potent mediators are released that by interacting may cause clinical syndromes like coronary ischemia, systemic hypertension, pulmonary hypertension, and renal failure. One of the mediators is serotonin, released from aggregating platelets, and causing vasoconstriction by activating S2-serotonergic receptors, particularly in patients with an impaired endothelial function, as in atherosclerosis. The most important available specific S2-serotonergic receptor antagonist is ketanserin. If administered during or after cardiac surgery, ketanserin lowers systemic and pulmonary blood pressure, and improves peripheral and pulmonary perfusion without causing reflex tachycardia or an increase in pulmonary shunt fraction.

Advances in pharmacotherapy: treatment of hypertensive crisis

A hypertensive crisis can be caused by many factors. Frequently, the mechanism involved is complex and highly variable among patients. Without drug therapy, this condition is associated with very high mortality and morbidity. There are a number of oral and intravenous hypotensive agents available, which can effectively control blood pressure in a hypertensive crisis. The relative advantages and disadvantages of each treatment option is discussed.