Sustained hemodynamic improvement during long-term therapy with levodopa in heart failure: role of plasma catecholamines

Palliative Care for Advanced Heart Failure in a Department of Veterans Affairs Regional Hospice Program: Patient Selection, a Treatment Protocol, and Clinical Course

BACKGROUND

Palliative care for advanced heart failure (HF) is generally recommended. However, few reports have focused on the particulars of treatment, or the clinical course of HF on a specific treatment regimen.

OBJECTIVE

Palliation adequate to allow patients to avoid HF admission and die at home.

METHODS

Patients from a veterans administration regional practice with multiple, recent hospital admissions were enrolled in community hospice programs. Treatment of HF with reduced left ventricular ejection fraction (HFrEF) included guidelines-directed medical therapy, digoxin, opioids, and oral bumetanide (with metolazone as needed) rather than intravenous diuretics. Levodopa (l-dopa) was added when conventional therapy failed to control symptoms. HF with preserved EF was also treated with bumetanide and opioids.

RESULTS

Thirty male veterans, 23 of them with HFrEF, had 90 HF admissions in the 6 months before enrollment, and 3 HF admissions during follow-up of at least 14 months. Twenty-one patients died, 18 of them at home; 14 died within 5 months, and the rest lived much longer. Failure to improve with initial therapy predicted early death. Results were similar for those with reduced and preserved left ventricular ejection fraction. L-dopa was started in 13 patients and tolerated by 8 patients; functional class improved and B-type natriuretic peptide declined after treatment.

CONCLUSIONS

With this treatment protocol, there were few HF admissions and patients were able to die at home. It can be used as a guide to therapy, or as an approach that can be tested with additional study.

Effects of levodopa therapy on global left ventricular systolic function in patients with Parkinson disease

OBJECTIVES

Since levodopa was identified as an efficient therapeutic option in Parkinson disease (PD), great success has been achieved in the course and treatment of the disease. However, L‑dopa-related side effects limit the therapeutic use in some patients. The aim of this study was to evaluate the effects of L‑dopa therapy on left ventricular global systolic function via speckle tracking method.

METHODS

In this study, 55 patients with PD under L‑dopa/dopa decarboxylase inhibitor therapy were compared with 30 age- and sex-matched control subjects. Conventional transthoracic echocardiography was performed in the left lateral position by two experienced operators in accordance with generally accepted guidelines. Left ventricular systolic function was analyzed by speckle tracking method using global longitudinal strain (GLS) and global circumferential strain (GCS) imaging.

RESULTS

Adequate echocardiographic imaging for the evaluation of global longitudinal strain and global circumferential strain could be achieved in 55 of the patients. LVEF (left ventricular ejection fraction), GLS and GCS values were found to be similar between the patients with PD under L‑dopa therapy and the control group (62 ± 3.5 % vs 61 ± 4 %, p < 0.05; -19.46 ± 2.3 vs -19.4 ± 3.2, p < 0.05; and -18.60 ± 3.5 vs -18.22 ± 3.2, p < 0.05 respectively.)

CONCLUSION

Levodopa therapy has no unfavorable effect on left ventricular systolic function in patients with PD.

Dopamine in heart failure and critical care

Dopamine is widely used in critical care to prevent renal function loss. Nevertheless sufficient evidence is still lacking of reduction in end points like mortality or renal replacement therapy. Dopaminergic treatment in chronic heart failure (CHF) has provided an example of unexpected adverse outcome. Pharmacoepidemiological data. Provide additional evidence, finding excess mortality in current ibopamine users (relative risk 2.03 in NYHA I-II CHF, 1.37 in NYHA III-IV), while no relation was found with antiarrhythmic use. In critical care, studies after infrarenal aortic surgery or during septic shock, respectively, failed to find, expected specific renal effects of dopamine. Effects on splanchnic flow mainly depend on baseline flow levels. The implications of recently documented unwanted effects of dopamine, like reduced ventilation and oxygenation during hypoxia, are discussed. In conclusion, controlled clinical trials remain mandatory to assess the overall clinical effects of dopamine in critical care.

Renal effects of L-DOPA in heart failure

We examined whether low-dose L-DOPA treatment induces natriuresis and diuresis in patients with congestive heart failure who have cardiac decompensation despite treatment with digoxin, a diuretic, and an angiotensin-converting enzyme inhibitor and who respond acutely to intravenously infused dopamine. In a randomized, double-blind, placebo-controlled crossover study, 11 patients with severe congestive heart failure received L-DOPA (0.10 g, p.o., t.i.d., for 1 day and then 0.25 g, p.o., t.i.d., for 2 days after a washout period of > or = 1 day), with assessments of plasma and urinary levels of catechols, urinary volume, and sodium content, and clinical and laboratory measures of improvement of congestive heart failure. L-DOPA elicited short-term, dose-related increases in urinary volume and sodium excretion. At the 0.10-g dose, L-DOPA increased plasma L-DOPA levels and urinary L-DOPA excretion by about fivefold, whereas at the 0.25-g dose, L-DOPA increased plasma and urinary L-DOPA by >50-fold. Twenty-four-hour urinary dopamine excretion increased by about fivefold after the low dose of L-DOPA and approximately 50-fold after the high dose. The results demonstrate that oral L-DOPA treatment can produce beneficial natriuretic and diuretic effects in selected patients with congestive heart failure. The bioavailability of oral L-DOPA appears to vary with the dose. These results support findings from previous studies about beneficial cardiac functional effects of L-DOPA in patients with refractory heart failure.

Hemodynamic and clinical effects of oral levodopa in children with congestive heart failure

OBJECTIVES

This study was undertaken to evaluate the safety, efficacy and pharmacodynamic variables of oral levodopa in pediatric patients with congestive heart failure refractory to standard therapy.

BACKGROUND

Therapeutic options for children with congestive cardiomyopathies are limited to digoxin, diuretic agents and angiotensin-converting enzyme inhibitors. Previous work in adults with congestive heart failure has shown a short-term effectiveness of levodopa and improvement of cardiac function.

METHODS

Baseline two-dimensional and M-mode echocardiography, surface electrocardiography, Holter monitoring and exercise testing, when applicable, were performed. Levodopa was administered in a dose escalation scale from 8 mg/kg body weight per dose to 20 mg/kg per dose over 3 days with concomitant metoclopramide and pyridoxine. Catecholamine levels at initiation of the trial and throughout dose escalation were measured, with echocardiographic and electrocardiographic correlation. After 24-h drug washout, cardiac catheterization was performed both before and after administration of levodopa.

RESULTS

Between February 1992 and December 1995, nine children (age 10 +/- 1.7 years, weight 27.8 +/- 4.3 kg) were enrolled in this study. At cardiac catheterization, serum dopamine levels rose from 108.5 +/- 59.2 pg/ml to 1,375.8 +/- 567.9 pg/ml (p = 0.03) at 100 +/- 14.8 min after levodopa administration without a significant change in serum norepinephrine or epinephrine levels. Paralleling these increases, there were significant changes in the cardiac index (1.7 +/- 0.3 to 3.2 +/- 0.7 liters/min per m2), stroke volume index (16.1 +/- 3.2 to 31.2 +/- 7.0 ml/m2 per min), oxygen consumption (138.6 +/- 24.4 to 188.3 +/- 30.8 ml/min per m2) and systemic vascular resistance (36.8 +/- 8 to 21.9 +/- 5.5 indexed Wood's units; all p < 0.01). There was a significant reversal of the daily fluid volume output/input ratio from 0.8 +/- 0.1 to 1.2 +/- 0.1 (p < 0.01). Levodopa administration was complicated by hypertension or tachycardia, or both, requiring a dose reduction in three patients, and by significant gastrointestinal distress in one. There was sustained symptomatic improvement a median of 19.5 months after drug initiation in seven of the patients.

CONCLUSIONS

These preliminary data support the hemodynamic value of oral levodopa in the treatment of severe congestive heart failure in children.

A randomized crossover trial of levodopa in congestive heart failure

BACKGROUND

The short- and long-term effects of levodopa (L-dopa), an oral dopaminergic prodrug, were assessed in patients with severe left ventricular dysfunction.

METHODS AND RESULTS

Initially, 26 patients were included in the study group. After clinical, radiographic, and radionuclide examination, each patient underwent right heart catheterization (Swan-Ganz thermodilution catheter). Plasma noradrenaline levels were measured. In two patients, a favorable hemodynamic response to L-dopa was not observed, another two required permanent pacemaker implantation. These four patients were excluded from the study. Two patients required permanent pacemaker implantation. The remaining 22 patients with favorable hemodynamic response to L-dopa (increase in cardiac index, stroke volume index, reduction in total systemic resistance) were randomized in a nonblinded fashion to the conventional (11 patients) or conventional plus L-dopa (11 patients) treatment groups. During the study period, two patients, one from each group, died. They were excluded from the analysis. The final analyzed study group consisted of 20 men, aged 33-69, in New York Heart Association functional class IV (9 patients) and III (11 patients). The cause of congestive heart failure was primary dilated cardiomyopathy in 11 patients and ischemic heart disease in 9 patients. After 3 months' treatment, all patients were crossed over. Clinical, radiographic, radionuclide, and hemodynamic evaluation was repeated at the end of the 3-month treatment period. After 3 months of therapy with L-dopa in each group (covariance analysis), there was improvement in clinical, radiographic (relative heart volume, -128 mL/m2), radionuclide (left ventricular ejection fraction, +4.6; right ventricular ejection fraction, +4.8%), hemodynamic (mean pulmonary wedge pressure, -8 mmHg; total systemic resistance, -1.8 Wu; total pulmonary resistance, -3.5 Wu), and neurohumoral (noradrenaline, -218 pg/mL) measures.

CONCLUSIONS

The addition of L-dopa to conventional therapy has beneficial short- and long-term effects in patients with severe left ventricular dysfunction.

Inotropic therapy for the failing myocardium

Congestive heart failure (CHF) is a common clinical entity with diverse causes. Patients may present with acute decompensation or have a more indolent course, with diminishing exercise tolerance and increasing dyspnea. The management of this clinical entity traditionally has focused on restricting fluid intake, decreasing dietary sodium, decreasing afterload with vasodilatory agents, and supporting the failing myocardium with agents which produce a positive inotropic response. In the acutely decompensated patient, short-term therapy with positive inotropics is clearly beneficial. The role of long-term inotropic therapy for chronic CHF remains less clear. A number of clinical trials have recently evaluated the effects of long-term therapy on morbidity and mortality, with disappointing results. For a number of the newer, nonglycocide oral positive inotropics, at doses of drug which produce measurable hemodynamic improvement, increased mortality in treatment groups has been unacceptably high. Ironically, patients with worse left ventricular dysfunction show the most clinical improvement, but have the highest increased mortality. However, as with digoxin, there is some evidence that employing lower doses of drug that do not produce measurable improvement in hemodynamic parameters may result in both improved clinical state and decreased mortality. This review discusses the role of both oral and intravenous inotropic agents, discusses the difficulty in translating short-term hemodynamic improvement into long-term clinical benefit, and presents a rationale for the use of lower-dose inotropic therapy to improve long-term clinical outcome.

Clinical efficacy of ibopamine in patients with chronic heart failure

Ibopamine, the most widely studied dopaminergic drug for the treatment of chronic heart failure, appears to have beneficial hemodynamic, renal, and neurohormonal effects in this setting. Angiotension-converting enzyme (ACE) inhibitors have become the recommended standard treatment for chronic heart failure; however, some patients may benefit from additional drugs to improve their symptoms and functional capacity. Ibopamine may be effective as an additive drug for patients with chronic heart failure. It is also possible that ibopamine will improve survival in these patients. Large-scale trials are needed to assess the effects on morbidity and mortality when ibopamine is added to ACE inhibitors, diuretics, and possibly digitalis.

Neurohormonal and hemodynamic effects of ibopamine

Ibopamine is the prodrug of epinine or N-methyl dopamine. Ibopamine stimulates the DA1 and DA2 dopaminergic receptors, the beta 1 and beta 2 adrenoceptors, and the alpha 1 and alpha 2 adrenoceptors. Ibopamine has varying degrees of affinity for these various families, being the highest for the dopamine receptors and the lowest for the alpha adrenergic receptors. In the clinical setting, there is a dose-related hemodynamic and neurohormonal response. In patients with heart failure (HF), low doses appear to exert beneficial neurohormonal, hemodynamic, and renal effects, without increased inotropic effects. However, at higher doses (> 200 mg) ibopamine exerts effects that do not appear to be clinically useful in long-term treatment of chronic HF. Several small trials have suggested a benefit of ibopamine on exercise performance in patients with mild to moderate HF. On the basis of these studies, ibopamine is now being used in Europe to treat patients with mild to moderate congestive heart failure (CHF). At doses of 100 or 200 mg/t.i.d., there has been no evidence of significant safety problems. Ibopamine may have a role in the treatment of patients with more severe left ventricular dysfunction who remain symptomatic despite therapy with diuretics and angiotensin-converting enzyme (ACE) inhibitors. Preliminary data suggest the drug is well tolerated in this setting and can decrease sympathetic stimulation. Large placebo-controlled trials will assess the benefits of the optimal dose of the drug when added to ACE-inhibitor therapy, and the effect on survival.

Sympathetic dysfunction in heart failure

CHF is a common, complex and life-threatening clinical syndrome. It is widely accepted that enhanced peripheral vascular tone plays a major role in the pathophysiology of CHF. Increased activity of the sympathetic nervous system is one of the most important factors responsible for the increased afterload in CHF. This increase in sympathetic activity occurs early in the course of development of CHF. Efferent sympathetic activity is distributed in a non-uniform way in CHF, with significant increases to the heart and kidney but normal activity to some other organs such as the lung. Increased renal sympathetic activity contributes significantly to altered neural haemodynamics, sodium and water retention, and modulation of the actions of other vasoactive hormones. The regional alteration in sympathetic activity may be largely responsible for the changes in resting regional blood flow to different organs in CHF and the maldistribution of blood flow that occurs during the stress of exercise. Disordered function of cardiovascular reflexes is observed in CHF and may contribute to disordered sympathetic function. In CHF there are significant interactions between the sympathetic nervous system and other humoral systems such as the renin-angiotensin system, AVP, ANP, endothelin and renal DA. The various drugs used in the treatment of CHF have different effects on sympathetic activity: digitalis and ACE inhibitors tend to suppress activity while diuretics may have the opposite effect. Following cardiac transplantation, there is a prompt return of sympathetic function towards normal, although the heart may remain significantly denervated for a long time, with gradual reinnervation. Cyclosporin therapy tends to increase sympathetic activity and this may contribute to post-transplant hypertension.

Inotropic therapy of the failing myocardium

The clinical syndrome of congestive heart failure remains a therapeutic dilemma and challenge for the physician in 1992. This is a disease process that appears to be increasing in frequency and continues to carry an unacceptably high mortality rate. For years it has been well recognized that the combination of digoxin, Lasix and vasodilator therapy improved symptoms in these patients and decreased hospitalization, but did not increase survival. It was not until 1986 that the combination of digoxin, Lasix, Isordil, and hydralazine was shown to increase survival. Further significant improvement in quality of life and survival has recently been established in three large clinical trials, and it is now safe to say that the standard of care for symptomatic congestive heart failure in 1992 is digoxin, furosemide, and an ACE inhibitor, with the survival trials favoring the ACE inhibitor enalapril. The IV inotropic drug dobutamine remains the mainstay of pharmacological therapy for the treatment of severely refractory heart failure. Unfortunately, the phosphodiesterase inhibitors--amrinone, milrinone, and enoximone--have demonstrated unacceptable clinical side effects and have been withdrawn from further clinical study. In spite of these promising developments, the mortality and morbidity of congestive heart failure remains unacceptably high, and continued investigation in the new fields of pharmacology and the pathophysiology of congestive heart failure still must be aggressively pursued.

Effects of dopaminergic agents on cardiac and renal function in normal man and in patients with congestive heart failure

Dopamine is an effective drug in the management of acute congestive heart failure. Its beneficial action is due to both cardiovascular--peripheral vasodilation and positive inotropy--and renal effects. Dopexamine is one of the newer dopamine agonists. Like dopamine, however, it can only be administered intravenously, and its value in the chronic treatment of congestive heart failure is limited. For this reason, dopamine analogs were developed with oral bioavailability, including levodopa, fenoldopam and biopamine. Although both levodopa and fenoldopam have shown beneficial hemodynamic effects, these agents cannot be recommended for general use in patients with congestive heart failure. Levodopa frequently causes side effects, especially nausea, and fenoldopam induces an increase in neurohumoral activity, which limits its long-term efficacy. Ibopamine has vasodilatory, mild inotropic and diuretic properties and it lowers plasma norepinephrine levels. Since ibopamine is usually well tolerated, it appears to have the most interesting profile of these oral dopaminergic agents.

Effects of acute and chronic ibopamine administration on resting and exercise hemodynamics, plasma catecholamines and functional capacity of patients with chronic congestive heart failure

The effects of acute and chronic ibopamine treatment on resting and exercise hemodynamics, exercise capacity and plasma catecholamines were evaluated in 25 patients with chronic heart failure, using a double-blind, parallel, placebo-controlled design. During 2 months of therapy with either placebo or ibopamine (100 mg, 3 times daily), 1 patient was withdrawn from each group for worsening heart failure, New York Heart Association functional class improved in 4 patients on ibopamine and in 1 on placebo, and furosemide dose could be decreased in 4 on ibopamine and in no patient on placebo. Acute ibopamine administration induced, in comparison with placebo, a significant increase of cardiac and stroke volume indexes both at rest and peak exercise, with a reduction of systemic vascular resistance. These hemodynamic changes were maintained also after chronic therapy, with no evidence of tolerance development. Exercise capacity (evaluated as peak exercise duration and oxygen consumption, and ventilatory threshold) did not significantly change. Resting and peak exercise norepinephrine plasma levels were significantly reduced after both acute and chronic ibopamine administration. Thus, the hemodynamic and neurohumoral effects of ibopamine make this drug potentially useful for the chronic treatment of congestive heart failure.

Current status of non-digitalis positive inotropic drugs

Considerable effort and resources have been directed at the development and study of positive inotropic drugs over the past 10-15 years. Much has been learned about the physiology and pharmacology of myocardial contraction, the application of agents to augment contractility, and, importantly, the general and specific limitations of positive inotropic therapy. Studies on acute inotropic intervention have now shown that a drug's ability to augment overall cardiac performance is heavily dependent on its effects on vasculature, vascular control, and ventricular-vascular coupling. The clinical research on new agents has served to remind us how difficult it is to formulate the "ideal" positive inotropic or cardiovascular support drug for the critical care setting. The vast effort to develop a chronically and orally administrable drug to replace or even supplement digitalis has generally been disappointing. The dopaminergic agents (e.g., ibopamine, levodopa) act primarily via vasodilation and their effectiveness and role in managing heart failure remain unresolved. The initial excitement about the phosphodiesterase III inhibitors (e.g., amrinone, milrinone, enoximone) has been tempered by the results of large well-designed trials indicating variable effectiveness and a prominent adverse effect profile. During long-term oral administration none of these agents has been shown to improve clinical status or exercise capacity beyond that achieved by digoxin, when administered either separately or in combination with digoxin. The Prospective Randomized Milrinone Survival Evaluation (PROMISE) trial, showing that repeated oral administration of milrinone can increase mortality in heart failure, is having a devastating effect on the further development of this class of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Medical management of chronic heart failure: inotropic, vasodilator, or inodilator drugs?

On the basis of pathophysiologic mechanisms, the medical therapy of today for chronic heart failure is reviewed. The advantages and disadvantages of the vasodilator drugs and the inotropic drugs are presented. Finally, the therapeutic value of the inodilator drugs, which combine the central myocardial effects of positive inotropic agents with those of peripheral vasodilators, is discussed. In particular, the orally available dopaminergic agents, such as ibopamine, which interact with beta-receptors in the heart (mediating a positive inotropic effect) as well as with dopaminergic receptors in the peripheral vessels (mediating a systemic vasodilator effect) and in the kidneys (potentiating the natriuretic effect of diuresis), seem to be an advancement in the modern medical therapy of chronic heart failure. Data are shown during long-term treatment with ibopamine, in which the sustained clinical benefit in heart failure was not diminished, despite a decrease of the adrenergic receptors in blood cells. Dopamine plasma concentration was permanently normalized during long-term treatment. The discrepancy between clinical improvement and the measured adrenergic downregulation may be due to the interference of the inodilator with neurohormonal systems at multiple sites and is probably independent of receptor activation. It is suggested that the biosynthesis of noradrenaline is improved by increasing intracellular dopamine transport.

Development of dopaminergic drugs for the chronic treatment of congestive heart failure

1. The search of orally active dopaminergic drugs for the chronic treatment of congestive heart failure has followed two different approaches. 2. On the one hand, a selective DA-1 receptor agonist, such as fenoldopam, has been investigated as an agent developed for the stimulation of vascular and tubular DA-1 receptors in the kidney. On the other hand, orally active prodrugs were synthetized with the aim of mimicking the full pattern of dopaminergic and adrenergic actions of intravenous dopamine. 3. Ibopamine, the diisobutyric ester of N-methyldopamine, has shown effects comparable to those of dopamine in various animal models and in clinical investigations. Furthermore, patients suffering from mild or severe congestive heart failure were shown to benefit from ibopamine treatment in a number of therapeutic trials. 4. Limited experience is currently available on other prodrugs, such as docarpamine and Sim 2055, i.e. the 4-0-phosphate ester of N-methyldopamine. The latter is an analogue of ibopamine designed for a preferential delivery of N-methyldopamine in the kidney. 5. Based upon some additional studies with levodopa, the results suggest that a combination of DA-1 and DA-2 agonistic activity is a desirable feature of a new drug, since it appears suitable to provide vasodilation while counteracting the neurohumoral abnormality of congestive heart failure.

Clinical relevance of long-term therapy with levodopa and orally active dopamine analogues in patients with chronic congestive heart failure

Beneficial effects of long-term treatment with dopamine analogues in patients with congestive heart failure may result from their vasodilating properties, in particular from renal artery vasodilation. Oral application of levodopa results in increased dopamine plasma levels and can improve cardiac performance and renal function in patients with congestive heart failure. A daily levodopa dosage of at least 4 g appears to a prerequisite for long-term response to the drug. Because of frequent side effects including nausea, vomiting, and dyskinesia at this dosage, the clinical usefulness of levodopa seems to be limited to a minority of patients. Ventricular arrhythmias have been shown to increase significantly during long-term levodopa therapy, probably due to stimulation of myocardial beta receptors. Increased ventricular arrhythmias or significant central nervous side effects have not been observed after administration of ibopamine and fenoldopam, which are orally active analogues of dopamine. Both agents exhibit potent arterial vasodilating properties and have been shown to increase cardiac performance in patients with congestive heart failure after short-term administration. The long-term beneficial effects of ibopamine and fenoldopam in the treatment of congestive heart failure have not yet been clarified. However, available results are encouraging and warrant further clinical evaluation of these agents, as well as the development of new analogues of dopamine, in particular of potent vascular dopamine agonists.

The use of levodopa, an oral dopamine precursor, in congestive heart failure

The successful treatment of congestive heart failure with intravenous dopamine in the acute setting has prompted investigation into the development and use of oral dopamine analogs. The administration of dopamine can lead to an improvement in myocardial pump performance through a combination of afterload reduction and augmented contractile state. The ingestion of levodopa, an oral dopamine precursor, is associated with sustained hemodynamic and clinical improvement in patients with congestive heart failure. Improvements in hemodynamic performance correlated with the generation of substantial amounts of dopamine. Current research efforts are directed at developing oral dopamine analogs that exhibit improved bioavailability and do not traverse the blood-brain barrier.

Systemic and coronary hemodynamic and neurohumoral effects of levodopa in chronic congestive heart failure

Systemic and neurohumoral effects of oral levodopa were evaluated in 17 patients with severe chronic heart failure. The maximum mean dopamine level achieved after 1.5 g of oral levodopa was 19.6 +/- 16.4 ng/ml. At peak dopamine level, cardiac index increased by 14% from baseline (1.95 +/- 0.55 to 2.27 +/- 0.45 liters/min/m2, p less than 0.05), stroke volume index increased by 14% (22.4 +/- 6.0 to 25.9 +/- 5.8 ml/min/m2, p less than 0.01). There was a trend toward reduced systemic vascular resistance of 13% (1,773 +/- 769 to 1,535 +/- 432 dynes.s.cm-5, p = 0.08). There was no significant change from baseline in heart rate, mean arterial pressure, right atrial pressure, pulmonary capillary wedge pressure, pulmonary vascular resistance and rate-pressure product. In addition, as the arterial dopamine level increased there was a concomitant decrease in plasma norepinephrine level that was sustained for the period of observation. In a subgroup of 8 patients, there was no change in coronary sinus blood flow, myocardial oxygen consumption, myocardial oxygen extraction, lactate extraction and transmyocardial release of catecholamines after levodopa. These findings suggest that oral levodopa, 1.5 g, can improve left ventricular function without adversely affecting myocardial energetics and catecholamine balance.

Vasodilator and inotropic drugs for the treatment of chronic heart failure: distinguishing hype from hope

During the past 10 years, more than 80 orally active vasodilator and inotropic agents have been tested in the clinical setting to evaluate their potential utility in the treatment of chronic heart failure. Although the initial reports of all of these drugs suggested that each represented a major therapeutic advance, only three agents--digoxin, captopril and enalapril--have produced consistent long-term hemodynamic and clinical benefits in these severely ill patients. Most of the other drugs that have been tested have not (to date) distinguished themselves from placebo therapy in large-scale, controlled trials, even though these agents produce hemodynamic effects that closely resemble those seen with digitalis and the converting-enzyme inhibitors. These observations suggest that the hemodynamic derangements that characteristically accompany the development of left ventricular dysfunction cannot be considered to be the most important pathophysiologic abnormality in chronic heart failure. Although cardiac contractility is usually depressed in this disease, positive inotropic agents do not consistently improve the clinical status of these patients. Similarly, although the systemic vessels are usually markedly constricted, drugs that ameliorate this vasoconstriction do not consistently relieve symptoms, enhance exercise capacity or prolong life. Hence, correction of the central hemodynamic abnormalities seen in heart failure may not necessarily provide a rational basis for drug development, and future advances in therapy are likely to evolve only by attempting to understand and modify the basic physiologic derangements in this disorder.

Dopamine and new dopamine analogs: receptors and clinical applications

Division of dopamine (DA) receptors and alpha- and beta-adrenoceptors into two subtypes provides a pharmacological basis for the clinical use of DA and new DA receptor agonists in anesthesia and critical care medicine. First, differential receptor activation explains why three distinct cardiovascular and renal responses can be obtained at low, medium, and high infusion rates of DA. Low infusion rates, in which DA1 and DA2 receptors are activated, are being increasingly used to improve renal perfusion and to treat oliguric states. The medium dose range (activation of beta1-adrenoceptors) is used for treatment of heart failure. The high dose range (activation of alpha-adrenoceptors) is used for treatment of shock. Second, selective DA1 and relatively selective DA2 agonists and agonists with different combinations of DA and receptor activity other than DA have been synthesized and are being investigated for the treatment of congestive heart failure and hypertension. Some of these compounds could have advantages over DA for acute therapy. Future availability of these drugs in anesthesia and critical care settings will depend to a great extent on input from anesthesiologists concerning potential new uses and willingness to conduct clinical investigations.