Comparative hemodynamic effects of dopamine and dobutamine in patients with acute cardiogenic circulatory collapse

Beneficial Effects of Ketone Ester in Patients With Cardiogenic Shock: A Randomized, Controlled, Double-Blind Trial

BACKGROUND

Cardiogenic shock (CS) is a life-threatening condition with sparse treatment options. The ketone body 3-hydroxybutyrate has favorable hemodynamic effects in patients with stable chronic heart failure. Yet, the hemodynamic effects of exogenous ketone ester (KE) in patients with CS remain unknown.

OBJECTIVES

The authors aimed to assess the hemodynamic effects of single-dose enteral treatment with KE in patients with CS.

METHODS

In a double-blind, crossover study, 12 patients with CS were randomized to an enteral bolus of KE and isocaloric, isovolumic placebo containing maltodextrin. Patients were assessed with pulmonary artery catheterization, arterial blood samples, echocardiography, and near-infrared spectroscopy for 3 hours following each intervention separated by a 3-hour washout period.

RESULTS

KE increased circulating 3-hydroxybutyrate (2.9 ± 0.3 mmol/L vs 0.2 ± 0.3 mmol/L, P < 0.001) and was associated with augmented cardiac output (area under the curve of relative change: 61 ± 22 L vs 1 ± 18 L, P = 0.044). Also, KE increased cardiac power output (0.07 W [95% CI: 0.01-0.14]; P = 0.037), mixed venous saturation (3 percentage points [95% CI: 1-5 percentage points]; P = 0.010), and forearm perfusion (3 percentage points [95% CI: 0-6 percentage points]; P = 0.026). Right (P = 0.048) and left (P = 0.017) ventricular filling pressures were reduced whereas heart rate and mean arterial and pulmonary arterial pressures remained similar. Left ventricular ejection fraction improved by 4 percentage points (95% CI: 2-6 percentage points; P = 0.005). Glucose levels decreased by 2.6 mmol/L (95% CI: -5.2 to 0.0; P = 0.047) whereas insulin levels remained unaltered.

CONCLUSIONS

Treatment with KE improved cardiac output, biventricular function, tissue oxygenation, and glycemic control in patients with CS (Treatment With the Ketone Body 3-hydroxybutyrate in Patients With Cardiogenic Shock [KETO-SHOCK1]; NCT04642768).

"Assessing the hemodynamic impact of various inotropes combination in patients with cardiogenic shock with Non-ST elevation myocardial infarction -the ANAPHOR study"

BACKGROUND

Various inotropic agents/vasopressors combinations are used in patients of cardiogenic shock. We performed this study to observe hemodynamic effects of various inotrope/vasopressor combinations in patients with NSTEMI cardiogenic shock (CS) at tertiary cardiac centre METHODS AND MATERIALS: Of 3832 NSTEMI, we studied 59 consecutive such patients with CS who hadn't undergone revascularization in the first 24 h in a prospective, open label, observational study. Group 1 comprised of background Dopamine with Noradrenaline titration(N = 38), Group 2 had background Dobutamine and Noradrenaline titration(N = 15) and Group 3 comprised of triple combination of Dopamine, Noradrenaline & Adrenaline(N = 6).

RESULTS

The mean change in hemodynamic parameters between these groups from baseline to 24 h showed no statistical difference. Cardiac output(CO), mean arterial pressure(MAP), central venous pressure(CVP) and cardiac power output(CPO) in group 2 were favorable at 6 and 24 h compared to baseline but mean change was insignificant as compared to others. In group 3, the increase in MAP was significant. IABP use did not change CO, CPO or SVR in any group except lower dosages of Dobutamine (49%) in IABP group. Lower in-hospital mortality in group 2 compared to others (P = 0.004) may be reflective of sicker patients in group 1 and 3.

CONCLUSION

The mean changes in hemodynamic parameters were not significant between all groups. All regimes of inotropes when selected as per clinical indication in CS with ACS resulted in similar hemodynamic effects. The mortality difference may not truly be reflective of regimes rather reflect sicker patients in the higher mortality group.

Vasoactive pharmacologic therapy in cardiogenic shock: a critical review

BACKGROUND

Cardiogenic shock (CS) is an acute complex condition leading to morbidity and mortality. Vasoactive medications, such as vasopressors and inotropes are considered the cornerstone of pharmacological treatment of CS to improve end-organ perfusion by increasing cardiac output (CO) and blood pressure (BP), thus preventing multiorgan failure.

OBJECTIVE

A critical review was conducted to analyze the currently available randomized studies of vasoactive agents in CS to determine the indications of each agent and to critically appraise the methodological quality of the studies.

METHODS

PubMed database search was conducted to identify randomized controlled trials (RCTs) on vasoactive therapy in CS. After study selection, the internal validity of the selected studies was critically appraised using the three-item Jadad scale.

RESULTS

Nine studies randomized 2388 patients with a mean age ranged between 62 and 69 years, were identified. Seven of studies investigated CS in the setting of acute myocardial infarction (AMI). The studies evaluated the comparisons of norepinephrine (NE) vs. dopamine, epinephrine vs. NE, levosimendan vs. dobutamine, enoximone or placebo, and nitric oxide synthase inhibitors (NOSi) vs. placebo. The mean Jadad score of the nine studies was 3.33, with only three studies of a score of 5.

CONCLUSIONS

The evidence from the studies of vasoactive agents in CS carries uncertainties. The methodological quality between the studies is variable due to the inherent difficulties to conduct a study in CS. Vasopressors and inotropes continue to have a fundamental role given the lack of pharmacological alternatives.

Inotropic Agents and Vasopressors in the Treatment of Cardiogenic Shock

BACKGROUND

Worldwide, cardiogenic shock (CS) is the leading cause of death in patients admitted with an acute myocardial infarction (AMI). CS is characterised by reduced cardiac output secondary to systolic dysfunction which can lead to multi-organ failure. The mainstay of medical treatment in CS are inotropes and vasopressors to improve cardiac output. However, current clinical guidelines do not direct clinicians as to which agents to use and in what combinations. This article aims to review the current evidence on the management of CS with a major focus on the use of inotropes and vasopressors.

METHOD

A literature review was conducted analysing published literature from the following databases: PubMed, MedLine, Cochrane Library and Embase, as well as a manual search of articles that were deemed relevant. Relevant articles were identified by using keywords such as "cardiogenic shock".

RESULTS

Literature was assessed to review the use of inotropes and vasopressors in CS. Dopamine and adrenaline were associated with increased mortality and arrhythmias. Dobutamine was associated with an improvement in cardiac output, at the determinant of causing arrhythmias. Conversely, noradrenaline was associated with a lower likelihood of arrhythmias and most importantly decreased mortality in CS. Compared to other inotropes, levosimendan appears to have a better safety profile and is associated with decreased mortality in CS, particularly when combined with a vasopressor. Our literature review suggests that treatment combination of the inotrope levosimendan with the vasopressor noradrenaline may be the most effective management option in CS.

Syndromes of Acute Left Ventricular Failure

The syndrome of acute left ventricular failure, manifesting as pulmonary edema and/or cardiogenic shock, occurs in many different clinical settings, has many different causes, and variable treatment strategies. Most commonly it is seen as a complication of acute myocardial infarction where loss of myocardial tissue results in ineffective systolic performance of the left ventricle. Urgent percutaneous transluminal coronary angioplasty may have a significant impact on outcome in this setting. Other complicating events following myocardial infarction may also precipitate left ventricular failure including papillary muscle dysfunction and ventricular septal defect. The syndrome of acute left ventricular failure is also commonly seen in patients with chronic congestive cardiac failure whereby myocardial infarction, arrhythmia and even minor increases in salt intake can precipitate acute decompensation. Other conditions such as fulminant myocarditis, bacterial endocarditis and disease processes characterized by diastolic dysfunction can all cause acute left ventricular failure. Moreover, cardiac function may be depressed in septic shock by the presence of cardiodepressant factors. In summary, acute left ventricular failure is a syndrome with a diverse etiology. Specific diagnosis of the particular cause is crucial to appropriate management.

Diagnosis and Management of Acute Congestive Heart Failure in the Intensive Care Unit

Congestive heart failure has emerged as an important public health problem in the United States and is pres ently the number one Diagnostic Related Group for inpatients over the age of 65. Patients admitted to an intensive care or coronary care unit because of de compensated heart failure are frequently older and frequently have multiple serious medical problems. In addition to standard intensive care practices, it is often important to characterize systolic and diastolic proper ties qualitatively with echocardiography. Hemodynamic monitoring is essential for patients with hypotension, oliguria, or questionable left ventricular filling pressures. A combination of loop diuretics, intravenous vaso dilators, and inotropic agents will often be necessary to correct severe underlying hemodynamic abnormalities, and an understanding of basic left ventricular systolic and diastolic function is essential to the optimal use of these potent agents. Manipulation of loading conditions and contractile state are important considerations, and pharmacological interventions should be targeted to ward specific abnormalities in individual patients. Once patients are stabilized, switching to orally active inotro pic and vasodilator agents can usually be accomplished over a 24-hour period, allowing for a total stay of 48 to 72 hours in the intensive care unit.

Congestive heart failure (CHF) is rapidly becoming a public health problem of major proportions [1- 5]. As the American population continues to age, we can expect greater numbers of patients to be admitted to intensive care units (ICUs) and coro nary care units (CCUs) with progressive decompen sation of previously stable CHF. Our current ap proaches to the diagnosis and management of acute heart failure are summarized; however, the care of such patients must always be highly individualized.

Pulmonary Hypertension in the Intensive Care Unit

Pulmonary hypertension occurs as the result of disease processes increasing pressure within the pulmonary circulation, eventually leading to right ventricular failure. Patients may become critically ill from complications of pulmonary hypertension and right ventricular failure or may develop pulmonary hypertension as the result of critical illness. Diagnostic testing should evaluate for common causes such as left heart failure, hypoxemic lung disease and pulmonary embolism. Relatively few patients with pulmonary hypertension encountered in clinical practice require specific pharmacologic treatment of pulmonary hypertension targeting the pulmonary vasculature. Management of right ventricular failure involves optimization of preload, maintenance of systemic blood pressure and augmentation of inotropy to restore systemic perfusion. Selected patients may require pharmacologic therapy to reduce right ventricular afterload by directly targeting the pulmonary vasculature, but only after excluding elevated left heart filling pressures and confirming increased pulmonary vascular resistance. Critically-ill patients with pulmonary hypertension remain at high risk of adverse outcomes, requiring a diligent and thoughtful approach to diagnosis and treatment.

Pharmacotherapy Update on the Use of Vasopressors and Inotropes in the Intensive Care Unit

This paper summarizes the pharmacologic properties of vasoactive medications used in the treatment of shock, including the inotropes and vasopressors. The clinical application of these therapies is discussed and recent studies describing their use and associated outcomes are also reported. Comprehension of hemodynamic principles and adrenergic and non-adrenergic receptor mechanisms are salient to the appropriate therapeutic utility of vasoactive medications for shock. Vasoactive medications can be classified based on their direct effects on vascular tone (vasoconstriction or vasodilation) and on the heart (presence or absence of positive inotropic effects). This classification highlights key similarities and differences with respect to pharmacology and hemodynamic effects. Vasopressors include pure vasoconstrictors (phenylephrine and vasopressin) and inoconstrictors (dopamine, norepinephrine, and epinephrine). Each of these medications acts as vasopressors to increase mean arterial pressure by augmenting vascular tone. Inotropes include inodilators (dobutamine and milrinone) and the aforementioned inoconstrictors. These medications act as inotropes by enhancing cardiac output through enhanced contractility. The inodilators also reduce afterload from systemic vasodilation. The relative hemodynamic effect of each agent varies depending on the dose administered, but is particularly apparent with dopamine. Recent large-scale clinical trials have evaluated vasopressors and determined that norepinephrine may be preferred as a first-line therapy for a broad range of shock states, most notably septic shock. Consequently, careful selection of vasoactive medications based on desired pharmacologic effects that are matched to the patient's underlying pathophysiology of shock may optimize hemodynamics while reducing the potential for adverse effects.

Inotropes

Inotropes have been fundamental to resuscitation of acute cardiogenic shock for decades. Heart failure and cardiogenic shock, in severe cases, are syndromes characterized in many patients by a reduction in myocardial contractile force. While inotropes successfully increase cardiac output, their use has been plagued by excessive mortality due to increased tachycardia and myocardial oxygen consumption leading to arrhythmia and myocardial ischemia. There is a pressing need for new inotropic agents that avoid these harmful effects. This review describes the mechanism of action and the clinical utility of some of the older inotropic agents, which are still commonly used, and provides an update for physicians on the development of newer inotropic drugs. The field is rapidly changing, and it is likely that new agents will be designed that improve systolic performance without necessarily increasing the myocardial oxygen consumption.

Inotropic agents and vasodilator strategies for acute myocardial infarction complicated by cardiogenic shock or low cardiac output syndrome

BACKGROUND

The recently published German-Austrian S3 Guideline for the treatment of infarct related cardiogenic shock (CS) revealed a lack of evidence for all recommended therapeutic measures.

OBJECTIVES

To determine the effects in terms of efficacy, efficiency and safety of cardiac care with inotropic agents and vasodilator strategies versus placebo or against each other for haemodynamic stabilisation following surgical treatment, interventional therapy (angioplasty, stent implantation) and conservative treatment (that is no revascularization) on mortality and morbidity in patients with acute myocardial infarction (AMI) complicated by CS or low cardiac output syndrome (LCOS).

SEARCH METHODS

We searched CENTRAL, MEDLINE (Ovid), EMBASE (Ovid) and ISI Web of Science, registers of ongoing trials and proceedings of conferences in January 2013. Reference lists were scanned and experts in the field were contacted to obtain further information. No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials in patients with AMI complicated by CS or LCOS.

DATA COLLECTION AND ANALYSIS

Data collection and analysis were performed according to the published protocol. All trials were analysed individually. Hazard ratios (HRs) and odds ratios with 95% confidence intervals (CI) were extracted but not pooled because of high heterogeneity between the control group interventions.

MAIN RESULTS

Four eligible, very small studies were identified from a total of 4065 references. Three trials with high overall risk of bias compared levosimendan to standard treatment (enoximone or dobutamine) or placebo. Data from a total of 63 participants were included in our comparisons, 31 were treated with levosimendan and 32 served as controls. Levosimendan showed an imprecise survival benefit in comparison with enoximone based on a very small trial with 32 participants (HR 0.33; 95% CI 0.11 to 0.97). Results from the other similarly small trials were too imprecise to provide any meaningful information about the effect of levosimendan in comparison with dobutamine or placebo. Only small differences in haemodynamics, length of hospital stay and the frequency of major adverse cardiac events or adverse events overall were found between study groups.Only one small randomised controlled trial with three participants was found for vasodilator strategies (nitric oxide gas versus placebo) in AMI complicated by CS or LCOS. This study was too small to draw any conclusions on the effects on our key outcomes.

AUTHORS' CONCLUSIONS

At present there are no robust and convincing data to support a distinct inotropic or vasodilator drug based therapy as a superior solution to reduce mortality in haemodynamically unstable patients with CS or low cardiac output complicating AMI.

Dobutamine-norepinephrine, but not vasopressin, restores the ventriculoarterial matching in experimental cardiogenic shock

We assessed the hemodynamic effects of guideline therapy in experimental cardiogenic shock and compared this treatment with a combination containing an alternative vasopressor (arginine vasopressin, AVP). Our hypothesis was that combined dobutamine-norepinephrine still is the superior inopressor therapy assessed by ventriculoarterial matching in both systole and diastole. Cardiogenic shock (CS) was induced by coronary microembolization in 16 pigs. Dobutamine (Dobu, 2ug/kg/min) alone and combined with either norepinephrine (NE, 100 ng/kg/min) or the pure vasopressor AVP (0.001 u/kg/min) were infused. In CS, Dobu increased cardiac output (CO) and central venous oxygen saturation (SVO₂) from 74 ± 3 mL/kg and 37 ± 2% to 103 ± 8 mL/kg and 49 ± 3%. Adding NE resulted in a further improvement of CO (125 ± 9 mL/kg) and SVO₂ (59 ± 4%) because of an increased heart rate and contractility with minimal change in systemic vascular resistance. Also, energy transfer from the ventricle to the arterial system was restored partly by Dobu and was normalized by supplementing NE. In contrast, supplemental AVP further worsened the shock state by decreasing CO (70 ± 6 mL/kg) and SVO₂ (45 ± 5%) compared with Dobu alone. Combined Dobu-NE has an efficient hemodynamic profile in CS. A pure afterload increasing substance used in acute ischemic CS aggravates the shock state by causing a ventriculoarterial mismatch despite its use in combination with an inotropic compound.

Effects of dobutamine on left ventriculoarterial coupling and mechanical efficiency in acutely ischemic pigs

This study investigated the effects of dobutamine on left ventriculoarterial (VA) coupling and mechanical efficiency in acutely ischemic pigs. Experiments were performed in 12 pigs in which vascular properties, including peripheral resistance (R2), compliance (C), and arterial elastance (Ea), were estimated with a windkessel model, and left ventricular (LV) function by the slope (Ees) of the end-systolic pressure-volume relationship (ESPVR) and stroke work (SW). VA coupling was defined as Ees/Ea, and mechanical efficiency as SW/pressure-volume area (PVA). In all animals, the left anterior descending coronary artery was ligated after basal measures. The animals were then randomly divided into 2 groups: group CTRL (n = 6) was followed for 180 minutes without other intervention, whereas group DOBU (n = 6) was infused with dobutamine (5 microg x kg(-1) x min(-1)) starting after T60 measures. Coronary occlusion induced a rightward shift of ESPVR and a decrease in Ees from 3.67 +/- 0.33 to 1.92 +/- 0.20 mm Hg x mL(-1), while Ea changed from 3.33 +/- 0.56 to 4.65 +/- 0.29 mm Hg x mL, R2 from 1.72 +/- 0.30 to 2.38 +/- 0.16 mm Hg x s x mL(-1), and C from 0.78 +/- 0.16 to 0.46 +/- 0.08 mL x mm Hg(-1). This altered VA coupling from 1.22 +/- 0.11 to 0.44 +/- 0.07. SW decreased from 4056 +/- 223 to 2372 +/- 122 mm Hg x mL, and PVA and SW/PVA decreased from 5575 +/- 514 to 4830 +/- 317 mm Hg x mL, and from 0.76 +/- 0.04 to 0.49 +/- 0.03, respectively. In group DOBU, dobutamine restored Ees and the position of ESPVR to baseline values, while Ea decreased to 3.39 +/- 0.34 mm Hg x mL(-1) because of an R2 decrease to 1.60 +/- 0.24 mm Hg x s x mL(-1). VA coupling was restored. SW and PVA increased to 3833 +/- 180 mm Hg x mL and to 7498 +/- 442 mm Hg x mL, respectively, while SW/PVA was unchanged. In ischemic pigs, dobutamine restored VA coupling through an increase in LV contractility and decrease in arterial elastance as a result of peripheral vasodilatation. However, myocardial oxygen consumption was increased, and mechanical efficiency impaired.

Role of nonglycosidic inotropic agents: indications, ethics, and limitations

Nonglycosidic inotropic agents have been used for the short-term management of low output states and hypotension complicating acute myocardial infarction for several years. Without adequate reperfusion of the ischemic myocardium, inotropic agents are seldom effective in producing sustained hemodynamic responses. Furthermore, the potential exists for enhancement of ischemia and extension of myocardial necrosis. Thus, inotropic and vasopressors therapy should be regarded as temporary supportive treatment in patients with acute coronary syndrome and should be discontinued as soon as feasible. Parenteral sympathomimetic agents, usually dobutamine, and phosphodiesterase inhibitors, usually milrinone, are used for the management of exacerbations of chronic systolic heart failure. Although hemodynamics, and occasionally clinical status, improve, such therapy is associated with increased mortality and can potentially hasten a patient's demise. Nonparenteral sympathomimetics, such as ibopamine, phosphodiesterase-III inhibitors, such as milrinone and enoximone, calcium-sensitizing agents, such as pimobendan, and other novel inotropic agents, such as vesnarinone, all increase mortality of patients with chronic heart failure. Furthermore, newer noninotropic agents, such as B-natriuretic peptide, have been introduced for treatment of decompensated heart failure. New nonpharmacologic devices, such as biventricular pacing, are available for the treatment of advanced heart failure. Thus, indications for the use of presently available nonglycosidic inotropic agents are limited and should be considered only for short-term therapy or when no other treatment is available.

The effectiveness and relative effectiveness of intravenous inotropic drugs acting through the adrenergic pathway in patients with heart failure-a meta-regression analysis

AIMS

To review systematically the use of intravenous (IV) inotropic agents acting through the adrenergic signalling pathway, compared with placebo or an active agent, in patients with heart failure.

METHODS

Studies investigating the use of intravenous inotropes in patients with heart failure published between 1966 and 2000 were identified using MEDLINE, the Cochrane register and Embase databases. Reference lists from relevant papers and reviews were hand searched for further papers. In total, 21 trials, that included 632 patients receiving IV inotropic drugs, placebo or non-treatment control, were identified. Drugs of the following classes were included, the beta-agonists; dobutamine, high-dose (>2.5 microg/kg/min) dopamine, dopexamine and the phosphodiesterase (PDE) inhibitors; amrinone, milrinone, enoximone and toborinone. Sixteen trials (474 patients) contributed data from acute invasive haemodynamic studies of symptomatically severe heart failure. Five trials (158 patients) were based on intermittent inotropic therapy in an outpatient context.

RESULTS

With few exceptions, trials of intravenous inotropic agents were small and often failed to report clinically important outcomes. Compared to placebo, intravenous inotropic agents acting through the adrenergic system tended to increase mortality (odds ratio 1.50 (95% CI=0.51 to 3.92) but this did not reach significance and insufficient data were available to determine whether symptoms improved. There appeared to be little difference in the effect of beta-agonists compared to PDE inhibitors on patient outcomes but this could be attributed to the paucity of data.

CONCLUSIONS

Intravenous inotropic agents acting through the adrenergic pathway are often used in patients with worsening heart failure to achieve arbitrary haemodynamic targets. Our analyses show that there is very little evidence that such treatment improves symptoms or patient outcomes and may not be safe. This highlights the need for further well designed randomised clinical trials.

Evaluation and management of acutely decompensated chronic heart failure in the emergency department

A wide range of patients with symptomatic heart failure seek treatment in the emergency department. While there is no single approach to the diversity of patients with acutely decompensated heart failure, certain overarching principles apply. For patients with acute pulmonary edema or cardiogenic shock, the first priority must be rapid stabilization and treatment of reversible problems. For patients with less dramatic presentations, a more systematic search for precipitating factors may be required. Therapy, in general, is directed at reversing dyspnea and/or hypoxemia caused by pulmonary edema, improving systemic perfusion, and reducing myocardial oxygen demand. While morphine and diuretics still have their traditional roles, vasodilators and inotropic agents play an increasingly important part in the modern pharmacologic approach to decompensated heart failure in the emergency department. After evaluation and stabilization in the emergency department, most patients will require hospital admission, although a subset of low-risk patients may be appropriate for discharge to home following a period of observation. Strategies to optimize emergency department care are likely to have an impact upon patient outcomes and upon resource utilization. (c)2001 by CHF, Inc.

Effect of a catecholamine-induced increase in cardiac output on extravascular lung water

OBJECTIVE

To determine the influence of dopamine- and dobutamine-induced increases in cardiac output on the extravascular lung water in an experimental model of pulmonary edema.

DESIGN

Animal experimental study.

SETTING

Animal experimental laboratory of a tertiary hospital.

SUBJECTS

Mixed-race pigs (n = 20) weighing 28-32 kg.

INTERVENTIONS

After the animals were anesthetized and tracheotomized, they were injected with 0.1 mL/kg of oleic acid, producing a pulmonary edema by increased permeability. The animals then were randomized into two groups: Group I (n = 10) received no medication to alter cardiac output and remained on mechanical ventilation during the 240 mins of the experiment; group II (n = 10) received a continuous infusion of dopamine and dobutamine to produce a cardiac output increase of >or=30% the basal value and underwent the same mechanical ventilation regimen as group I.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic and respiratory variables were measured at 0 (baseline) and 30, 60, 120, 180, and 240 mins after the infusion of oleic acid. At 30 mins, the cardiac output of group II (5.40 +/- 0.94 L/min) was significantly (p < .005) higher than that of group I (3.65 +/- 1.02 L/min), and a similar significant increase was recorded at all measurement times until the end of the experiment. The mean pulmonary arterial pressure was similar in both groups except that at 240 mins it was significantly higher in group I (normal cardiac output) than in group II (high cardiac output; 34.9 +/- 7.9 mm Hg vs. 27.2 +/- 3.8 mm Hg, p = .01). The extravascular lung water was calculated by gravimetric method after the death of the animal. The extravascular lung water of group I (13.8 +/- 3.6 mL/kg) did not significantly differ from that of group II (11.5 +/- 4.0 mL/kg).

CONCLUSIONS

An increase in cardiac output experimentally produced by the infusion of dopamine and dobutamine does not modify the amount of extravascular lung water.

Myocardial high-energy phosphate metabolism in patients with stable chronic dilated cardiomyopathy under a dobutamine-induced prolonged mild workload

BACKGROUND

The myocardial phosphocreatine (PCr) to beta-adenosine triphosphate ratio measured by phosphorus 31 nuclear magnetic resonance spectroscopy, which is analogous to energy reserve, is one of the important clinical predictors in patients with dilated cardiomyopathy (DCM). However, it may vary with the cardiac workload.

METHOD

The myocardial PCr to beta-adenosine triphosphate ratio was measured before and during a 5 and 10 microgram/kg/min infusion of dobutamine in 7 patients with DCM and in 8 normal patients. Dobutamine infusion was kept constant for 50 minutes in each stage. Myocardial contractility and ventricular size were determined by echocardiography with the same protocol.

RESULTS

This ratio was unchanged from 1.5 +/- 0.4 to 1.8 +/- 0.6 in the low-dose stage and stable (1.7 +/- 0.3) in the high-dose stage in patients with DCM. The heart rate and the mean rate of circumferential fiber shortening increased dose dependently both in patients with DCM and in patients without.

CONCLUSION

These results demonstrate that constant loading of dobutamine for hours is tolerated without deterioration of myocardial metabolic function by patients with nonischemic DCM. We concluded that the high-energy phosphate metabolism of stable patients with cardiomyopathy is stable if the workload is temporary and weak. This implies the possibility that mild exercise can be tolerated in patients with heart failure.

Parenteral inotropic support for advanced congestive heart failure

Parenterally administered positive inotropic agents remain an important component of the therapeutics of cardiac dysfunction and failure. Dobutamine, a catechol, remains the prototype of this drug group, but recently has been joined by the phosphodiesterase III inhibitor, milrinone. Compared with dobutamine, milrinone has greater vasodilating-unloading properties. The catecholamine, dopamine, is often used as a parenteral positive inotrope; but at moderate to high dose, it evokes considerable systemic vasoconstriction. At lower doses, dopamine appears to augment renal function. Levosimendan and toborinone, new compounds with several mechanisms of action, are under active clinical investigation and review for approval. Parenteral positive inotropic therapy is indicated for short-term (hours to days) treatment of cardiovascular decompensation secondary to ventricular systolic dysfunction, low-output heart failure. More prolonged or continuous infusion of one of these agents may be necessary as a "pharmacologic bridge" to cardiac transplantation, another definitive intervention, or more advanced, intense medical therapy. An occasional patient will require a continuous infusion via indwelling venous catheter and portable pump, simply to be able to be discharged from the hospital setting and function in the home environment. Intermittent parenteral inotropic therapy for chronic heart failure has provoked considerable controversy and passion among cardiologists and heart failure specialists; an attempt is made to present this topic in an objective manner.

The role of the vasculature in regulating venous return and cardiac output: historical and graphical approach

PURPOSE

To review the physiology of cardiac output regulation by the peripheral vasculature. This will enable the clinician to understand and manage the complex circulatory changes in various forms of shock, and in other common altered circulatory states encountered in anaesthetic practice.

SOURCE

Articles were obtained from a Medline review (1966 to present; search terms: shock, venous return, cardiac output) and a hand search (Index Medicus). Other sources include review articles, personal files, and textbooks.

PRINCIPAL FINDINGS

At steady state, cardiac output is equal to venous return (VR). Venous return depends on mean systemic pressure (PMS), which is the pressure in the peripheral vasculature driving blood flow to the heart, right atrial pressure (PRA), and the resistance to venous return (RV). When considering VR, PRA is the downstream pressure to VR, and not simply an indirect measure of the volume status. The pressure gradient for VR is, therefore, PMS-PRA, and in a system obeying Ohm's Law, [formula: see text] Shock and other altered circulatory states cause changes in both VR and cardiac function. The circulation can be conveniently described by a venous return and a cardiac output curve. By drawing these curves for each clinical situation, a clear understanding of the altered circulatory state is obtained, and treatment options can be clearly defined.

CONCLUSION

The peripheral circulation controls cardiac output in many clinical conditions. Manipulation of the peripheral circulation is as important to the successful treatment of shock and other altered circulatory states, as is the manipulation of cardiac output.

Effect of dialysis on exogenous dopamine in haemodialysed critically ill patients

A sensitive and specific high performance liquid chromatographic method (HPLC) was developed for measuring dopamine (DA) in human plasma samples. Dihydroxybenzylamine (DHBA) was employed as an internal standard. Following solvent extraction and separation on a C18 ion-pairing reversed phase column, the drug was detected by a fluorescence detector with excitation and emission wavelengths of 233 nm and 345 nm, respectively. This method was employed to evaluate dopamine dialysability in seven haemodialysed patients under continuous infusion of a positive inotropic agent. Results showed a high dialyser extraction ratio averaging 38.3%, but a low dialysis clearance of 67 ml/min. The fraction removed by dialysis is 2.5%. We concluded that haemodialysis has little effect on dopamine blood levels, and consequently on drug pharmacokinetics, when the drug is delivered to haemodialysed patients under intravenous infusion.

Cardiogenic shock: thrombolysis or angioplasty?

Cardiogenic shock (CGS) occurs in 3 to 20% of patients presenting with acute myocardial infarction (MI), and it generally involves dysfunction of at least 40% of the total myocardial mass. Prior to the advent of balloon angioplasty and thrombolysis, in-hospital mortality was greater than 75%. This mortality rate has been consistent in reported series despite the advent of cardiac intensive care units, vasopressor, inotropic, and vasodilator therapy. Intra-aortic balloon counterpulsation therapy provides hemodynamic improvement, and it may provide some mortality benefit when used in conjunction with appropriate revascularization. Survival studies have shown that patency of the infarct-related artery is a strong predictor of survival. No randomized trials have been completed to examine which reperfusion therapy best treats this emergent situation. Subgroup analysis of large scale, multicenter trials, although underpowered, has shown no improvement in mortality with use of thrombolytic agents, leading many to advise use of mechanical intervention. In patients who present with acute MI with contraindications to thrombolysis, primary angioplasty is the treatment of choice. At selected centers, primary angioplasty is comparable to or better than thrombolytic therapy for patients presenting with acute MI, with or without CGS. Studies examining angioplasty in patients with CGS have shown high procedural success rates (75%) and reduced in-hospital mortality (44%), particularly in those patients with successful revascularization. Emergency bypass surgery may improve survival, but it is costly, unavailable to many, and often leads to excessive delays in therapy. If available, we believe that primary angioplasty is the treatment of choice for patients with CGS.

Electrophysiologic and proarrhythmic effects of intravenous inotropic agents

Intravenous inotropic agents promote increased myocardial contractility via elevation of myocyte calcium concentrations, a mechanism that is also known to promote the development of cardiac arrhythmias. The purpose of this article is to review the electrophysiologic effects and relative potential for proarrhythmia associated with dobutamine, dopamine, and the phosphodiesterase inhibitors amrinone and milrinone. Dobutamine increases sinoatrial node automaticity and decreases atrial and atrioventricular (AV) node refractoriness and AV nodal conduction time. The drug also decreases ventricular refractoriness in both healthy and ischemic myocardium. Dobutamine has been shown to increase heart rate in a dose-related fashion in animals and in humans. In humans, dobutamine has been reported to induce ventricular ectopic activity (VEA) in 3% to 15% of patients, although VEAs are often asymptomatic, requiring no intervention. Ventricular tachycardia (VT) associated with dobutamine appears to occur rarely. Patients with underlying arrhythmias or heart failure or those receiving excessive doses of dobutamine are at greatest risk for proarrhythmia. Dopamine increases automaticity in Purkinje fibers and has a biphasic effect on action potential duration. Dopamine has been reported to induce atrial or ventricular arrhythmias in animals. In humans, dopamine may be associated with dose-related sinus tachycardia but has also been reported to cause VEA, which is usually asymptomatic. Dopamine-associated VT appears to occur rarely. Dopamine produces greater elevations in heart rate or frequency of ventricular premature beats at a given value of cardiac index than does dobutamine. The phosphodiesterase inhibitors amrinone and milrinone increase conduction through the AV node and decrease atrial refractoriness. Intravenous administration of these drugs may result in sinus tachycardia in some patients and has been reported to cause VEA, which is often asymptomatic, in up to 17% of patients. VT has also been reported in association with short-term use of intravenous phosphodiesterase inhibitors. In summary, intravenous inotropic agents may be associated with proarrhythmic effects in some patients. The primary arrhythmias reported are sinus tachycardia and VEA, although other supraventricular or ventricular arrhythmias have been reported less commonly. However, clinically significant proarrhythmic effects associated with these agents appear to occur rarely, and, at conventional doses, intravenous inotropic agents are relatively safe with respect to proarrhythmic effects.

Proarrhythmic effects of intravenous vasopressors

OBJECTIVE

To review the electrophysiologic properties and the in vitro, ex vivo, animal, and human data regarding proarrhythmic effects of intravenous vasopressors.

DATA SOURCES

A comprehensive (MEDLINE) search (1960-1994) was conducted for dopamine, epinephrine, norepinephrine, phenylephrine, and methoxamine.

STUDY SELECTION

In vitro and ex vivo studies and investigations performed in animals or humans reporting electrophysiologic and/or proarrhythmic effects of the above intravenous vasopressors were selected. A comprehensive search of all human studies involving these agents was conducted to reveal any proarrhythmic effects that may have been reported. In addition, case reports of proarrhythmic effects associated with these agents were reviewed.

DATA EXTRACTION

Data regarding electrophysiologic and proarrhythmic effects of these agents were extracted from in vitro, ex vivo, animal, and human studies. Because few studies with the specific purpose of investigating proarrhythmic effects of vasopressors have been performed in humans, all studies involving these drugs for evaluation of hemodynamic effects, clinical efficacy, or other endpoints in humans were reviewed. In addition, data were extracted from case reports of proarrhythmic effects associated with these agents.

DATA SYNTHESIS

Dopamine increases automaticity in Purkinje fibers and has a biphasic effect on action-potential duration. Dopamine has caused both atrial and ventricular tachyarrhythmias in animals. Human data have revealed dose-related sinus tachycardia, with few reports of clinically significant ventricular arrhythmias. Epinephrine shortens sinus cycle length, increases atrial and ventricular automaticity, promotes atrioventricular nodal conduction, and decreases ventricular effective refractory period (ERP). It is well known to induce ventricular fibrillation and decrease the ventricular fibrillation threshold (VFT) in ex vivo models as well as intact animals. In humans, epinephrine may cause dose-related sinus tachycardia, supraventricular arrhythmias, or, more commonly, ventricular arrhythmias. Norepinephrine increases automaticity of the sinoatrial node, atria, and ventricles; promotes atrioventricular nodal conduction; and decreases ventricular ERP. In vitro/ex vivo and animal data have shown that norepinephrine significantly decreases VFT. Although electrophysiologic studies suggest that norepinephrine may be proarrhythmic, few supporting data exist in humans. Phenylephrine demonstrates differential electrophysiologic effects in atrial and ventricular tissue. Most data suggest that phenylephrine causes prolongation of the ventricular ERP. Rather than being proarrhythmic, phenylephrine may be protective against arrhythmias. The drug elevates VFT in dogs. In humans, phenylephrine effectively terminates supraventricular tachycardias and may be protective against ventricular arrhythmias. Like phenylephrine, methoxamine elevates the repetitive extrasystolic, atrial, and ventricular fibrillatory thresholds. Methoxamine also may have antiarrhythmic effects because of alpha-receptor stimulation and reflex vagal activity. Despite the relatively low risk of arrhythmogenicity associated with intravenous vasopressors, patients should be monitored for potential proarrhythmic effects and appropriate action taken as necessary. Critically ill patients often have concurrent conditions, electrolyte disturbances, and underlying arrhythmias that predispose them to a higher risk of vasopressor proarrhythmic effects.

CONCLUSIONS

Controlled data supporting the proarrhythmic potential of intravenous vasopressors in humans are lacking. Sinus tachycardia, asymptomatic ventricular ectopic activity, and other ventricular or supraventricular arrhythmias have been reported in association with dopamine and epinephrine. Phenylephrine and methoxamine have been associated with sinus bradycardia, but otherwise may be antiarrhythmic. Intravenous vasopressors appear relatively safe w

Solid phase extraction and high performance liquid chromatographic determination of dobutamine in plasma of dialysed patients

An isocratic reversed-phase high performance liquid chromatographic method has been developed for th e determination of dobutamine in the plasma of dialysed patients. A solid phase extraction method with a Sep-Pak C18 cartridge was used to isolate the drug and isoxsuprine (internal standard) from plasma. The separation was carried out on an ODS-Hypersil column with 0.1 M phosphate buffer:acetonitrile:methanol (72:20:8 v/v/v) as the mobile phase. The recovery of dobutamine added to plasma by the extraction procedure was 87 +/- 2.3% (mean +/- SD). The accuracy and reproducibility of the method were within acceptable limits over the concentration range 0-1000 ng/mL. Quantification was by fluorescence detection at 275 nm excitation and 310 nm emission wavelengths with a detection limit of 5 ng/mL for dobutamine. This procedure was applied to ascertain the pharmacokinetics of dobutamine infusion in nine patients with cardiogenic shock and end-stage renal disease undergoing haemodialysis.

Cardiogenic shock: elements of etiology, diagnosis, and therapy

Cardiogenic shock usually is the result of marked depression in myocardial function. Rapid recognition and stabilization are essential if the patient is to survive. A variety of cardiovascular conditions can lead to cardiogenic shock; the most common of these is acute myocardial infarction. Once stabilization of the cardiogenic shock patient has been effected, hemodynamic monitoring and definitive therapy should be attempted if appropriate. Intra-aortic balloon counterpulsation is effective in stabilizing these patients temporarily. Definitive therapy may include surgical or catheterization interventions. Mortality, even under the best of circumstances, remains high.

Pathogenesis and management of acute heart failure and cardiogenic shock: role of inotropic therapy

Patients with acute heart failure or cardiogenic shock following myocardial infarction have a high mortality. The first priority is to salvage any remaining viable myocardium, either by thrombolytic agents or, if necessary, by coronary angioplasty. A mechanical cause for the heart failure or shock needs to be excluded. Thereafter, the optimal therapeutic regimen needs to be chosen on the basis of each patient's hemodynamic profile. Patients can be broadly classified into three groups: (1) patients with a high left ventricular filling pressure (> 18 mm Hg) and a cardiac index < 2.2 L/min/m2 but systolic arterial pressure > 100 mm Hg; (2) patients with a systolic arterial pressure < 90 mm Hg, left ventricular filling pressure > 18 mm Hg, and cardiac index < 2.2 L/min/m2; and (3) patients with an elevated right ventricular filling pressure (> 10 mm Hg) and cardiac index < 2.2 L/min/m2 and a systolic arterial pressure < 100 mm Hg. Patients in the first subset usually require the use of vasodilator therapy and/or dobutamine. The choice of inotropic agent in patients in the second hemodynamic subset depends on the degree of systemic hypotension; dopamine is usually preferred initially because it increases arterial pressure in addition to improving cardiac output. Once the systemic blood pressure has been stabilized, dobutamine can be substituted for superior augmentation of cardiac output and its additional beneficial effects on the left ventricular filling pressure. Norepinephrine may be indicated in cases of severe systemic hypotension. Patients in hemodynamic subset 3, ie, right ventricular infarction, are treated with volume expansion and dobutamine. Use of nonpharmacologic means of circulatory support, eg, intra-aortic balloon pump or left ventricular assist device may also be required in any of these subsets.

Combined dose ratios of dopamine and dobutamine and right ventricular performance after cardiac surgery

The effect of combined administration of different dose ratios of dobutamine (DB) and dopamine (DA) (DB/DA ratio of 1:1; 1.5:0.5; 2:0; 0.5:1.5; and 0:2), with the added dose kept constant (10 micrograms/kg/min-20 micrograms/kg/min), on right ventricular function (measured by the thermal washout method with the aid of a rapid-response thermistor) was determined in ten patients after cardiac surgery (between 12 and 24 h after surgery). The following values represent the mean +/- SD of DB only and of the DB/DA-equal combination vs DA only. The DB/DA-equal or DB-dominant combination increased the right ventricular ejection fraction vs DA only (0.39 +/- 0.12 [p less than 0.01] and 0.37 +/- 0.11 [p less than 0.05], respectively, vs 0.32 +/- 0.12) and the stroke volume index (43 +/- 12 ml/m2 [p less than 0.01] and 41 +/- 15 ml/m2, respectively, vs 38 +/- 14 ml/m2) and decreased right ventricular end-diastolic pressure (RVEDP) (10 +/- 4 mm Hg [p less than 0.01] and 11 +/- 4 mm Hg [p less than 0.05], respectively, vs 13 +/- 5 mm Hg) and pulmonary capillary wedge pressure (10 +/- 4 mm Hg [p less than 0.01] and 12 +/- 5 mm Hg [p less than 0.05], respectively, vs 14 +/- 6 mm Hg) to the same degree as DB alone. The DB/DA-equal or DB-dominant combination did not induce tachycardia (heart rate, 105 +/- 11 [p less than 0.05] and 95 +/- 14 beats per minute, respectively, vs 90 +/- 17 beats per minute) or have any effect on the right ventricular end-diastolic volume index (RVEDVI) (115 +/- 30 ml/m2 and 117 +/- 33 ml/m2, respectively, vs 127 +/- 42 ml/m2). Moreover, the diastolic parameters of the right ventricle (the ratio of RVEDVI/RVEDP: 15 +/- 8 [p less than 0.05] and 13 +/- 7, ml/mm Hg/m2, respectively, 11 +/- 5 ml/mm Hg/m2) decreased as the ratio of DA increased. This change in the diastolic properties of the right ventricle might have been caused by release of norepinephrine in the myocardium by DA or by improved coronary perfusion with DB. The DB/DA-equal and DB-dominant combinations were superior to DB or DA alone and to the DA-dominant combination in obtaining enhanced right ventricular performance.

Effects of a twenty-four-hour milrinone infusion in patients with severe heart failure and cardiogenic shock as a function of the hemodynamic initial condition

The systemic and pulmonary arterial hemodynamics of 40 patients with severe congestive heart failure were determined during a 24-hour infusion of milrinone (0.5 micrograms/kg/min) after a loading dose of 50 micrograms/kg. A subgroup (n = 18) with severe cardiac pump dysfunction and three patients in cardiogenic shock were analyzed separately; their hemodynamic response was compared with that of the total group (n = 40). After 15 minutes of intravenous therapy with milrinone, the total group (n = 40) showed an increase of 65% in cardiac index; in the subgroup (n = 18) cardiac index increased by 94% after 15 minutes and by 106% after 30 minutes. Likewise, pulmonary capillary wedge pressure decreased after 30 minutes in both the total group (n = 40) and the subgroup (n = 18). The heart rate showed an overall tendency to decrease. The systolic blood pressure tended upward and remained statistically unchanged in the total group, whereas in the subgroup in which pressure was initially low, there was an increase in the systolic pressure after 1 hour and a further increase after 24 hours. Mean arterial pressure also rose in this subgroup. The early improvement in all measured hemodynamic parameters was sustained throughout the 24-hour infusion period. Development of tolerance was not observed, nor were any clinically symptomatic side effects or symptomatic arrhythmias. Thus intravenous milrinone is a safe medication for the rapid and prolonged improvement in hemodynamics, specifically in patients with severely restricted cardiac pumping function.

Phosphodiesterase III inhibition or adrenoreceptor stimulation: milrinone as an alternative to dobutamine in the treatment of severe heart failure

High levels of endogenous plasma catecholamines in patients with severe congestive heart failure induce a down-regulation of the myocardial beta-adrenoreceptors and thus cause adrenoreceptor agonists, such as dobutamine, to be less effective in the treatment of these patients. Phosphodiesterase III inhibitors work independent of adrenoreceptor activity and plasma catecholamine levels; thus these agents are likely to be more effective in the treatment of severe heart failure. The present study compares both the initial and late hemodynamic effects of dobutamine and milrinone during sequentially administered 24-hour infusions. Twenty patients with severe heart failure (New York Heart Association class III, n = 4; New York Heart Association class IV, n = 16) were investigated. Dobutamine could be administered at the prescribed maximum dose of 15 micrograms/kg/min for 24 hours in only 15 of 20 patients. In three patients the dose was reduced or dobutamine infusion completely stopped because of a drug-related increase in heart rate greater than 140 beats/min. Another 2 of 20 patients showed no hemodynamic improvement over 3 hours at the maximum dose of 15 micrograms/kg/min. Dobutamine administration was also discontinued in these patients on account of the existing unfavorable hemodynamic condition, and therapy with intravenous milrinone was started. All 20 patients responded to milrinone without side effects, although comparison of the hemodynamic effects during a 24-hour infusion was possible in only 15 patients. The 15 patients studied over both observation periods experienced an increase in heart rate from 88.8 to 105.6 beats/min (+ 1 hour; p less than or equal to 0.001) when receiving dobutamine but had no increase with milrinone. Stroke volume increased during dobutamine infusion from 19.3 to 28.9 ml/m2 (+49.6%) after 1 hour and then fell continuously to 25.2 ml/m2 after 12 hours; during milrinone therapy, stroke volume increased from 18.8 to 31.2 ml/m2 (+66%; p less than or equal to 0.001) and remained at this level until the end of the infusion (30.2 ml/m2). Pulmonary capillary wedge pressure (PCWP) decreased (p less than or equal to 0.001) immediately during milrinone therapy from 26.5 to 16.2 mm Hg after 30 minutes and stabilized at 20.1 mm Hg after 24 hours. During dobutamine infusion PCWP showed a delayed decrease from 27.8 to 19.0 mm Hg after 6 hours and subsequently rose to 22.7 mm Hg after 24 hours.(ABSTRACT TRUNCATED AT 400 WORDS)

Acute positive inotropic intervention: the catecholamines

The catecholamines remain a major therapeutic group in intensive cardiac care; this group of compounds evokes a positive inotropic response and vascular effects ranging from vasoconstriction to little net effect to vasodilatation. Hemodynamics and clinical guidelines now allow a proper selection of the optimal catecholamine. Additional mechanisms of action and a better understanding of the clinical application of this important drug group are continuing to unfold.

Comparison of the haemodynamic effects of dopexamine and dobutamine in patients with severe congestive heart failure

Dopexamine hydrochloride is a novel compound with properties of DA1-dopaminergic and beta 2-adrenergic receptor agonism and neuronal noradrenaline uptake inhibition. It has been shown to produce beneficial renal and haemodynamic effects in patients with severe heart failure. We compared the haemodynamic effects of dopexamine (0.5 to 6 micrograms/kg/min) with those of dobutamine (5 to 25 micrograms/kg/min) in 9 patients with severe congestive heart failure. The two drugs were similar in their effects at peak infusion rates: heart rate increased (dopexamine 87 +/- 17 to 100 +/- 14; dobutamine 91 +/- 18 to 103 +/- 17 min-1), cardiac index increased (dopexamine 1.7 +/- 0.5 to 2.8 +/- 1.1; dobutamine 1.8 +/- 0.5 to 3.0 +/- 1.1 l.min-1.m-2) and systemic vascular resistance decreased (dopexamine 1553 +/- 221 to 1117 +/- 432; dobutamine 1721 +/- 347 to 1280 +/- 433 dyne.s.cm-5). Neither drug affected pulmonary artery wedge pressure (dopexamine 24 +/- 6 to 22 +/- 6; dobutamine 25 +/- 9 to 24 +/- 10 mm Hg). Dopexamine had significantly lower peak effects on left ventricular stroke work index (dopexamine 20 +/- 9, dobutamine 27 +/- 15 g.m.m-2, P less than 0.05) and cardiac power output (dopexamine 0.71 +/- 0.36, dobutamine 0.93 +/- 0.46 W, P less than 0.05). These haemodynamic effects, due largely to vasodilatation but with some contributory positive inotropy, indicate that dopexamine will be useful in the acute treatment of congestive heart failure.

Dobutamine: ten years later

Dobutamine is a commonly used positive inotrope for the short-term management of heart failure. It is commercially available as a 50:50 mixture of two isomers with unique effects on alpha- and beta adrenergic receptors. In dosages of 2-15 micrograms/kg/minute, dobutamine has been shown to increase cardiac output (mainly through stroke volume), reduce systemic vascular resistance, lower central venous and pulmonary artery wedge pressures, improve renal blood flow, and relieve signs and symptoms of congestive heart failure. At higher dosages it can increase heart rate and induce arrhythmias. Recent evidence indicates that effects of dobutamine last long after the drug has been eliminated from the plasma, and some work has been done on ambulatory use of this agent. Dobutamine has been used successfully in several circumstances, such as after cardiac surgery, in patients with myocardial infarction, and in various shock states. An understanding of the pathophysiology of the underlying disorder is important in deciding which catecholamine to use. With this in mind, monotherapy or combination therapy with inodilators such as dobutamine, or inopressors like dopamine will follow logically.

Comparison of hemodynamic and oxygen transport effects of dopamine and dobutamine in critically ill surgical patients

Hemodynamic and oxygen transport effects of dopamine and dobutamine were studied in a series of 25 critically ill postoperative general surgical patients by a prospective, randomized crossover design after maximal response to fluids had been obtained. Dopamine increased MAP, HR, CI, PvO2, DO2, and Qsp while decreasing PaO2. Dobutamine increased HR, CI, SI, stroke work, DO2, VO2, and Qsp while decreasing PAWP and SVRI and PVRI. In general, the effects of the two drugs were greater in patients in the first 72 hours after surgery. The effects of dobutamine on flow and oxygen transport were greater than those of dopamine, especially in the early postoperative period. The effects were smaller and not significant in patients more than three days after surgery, as well as in those with sepsis, respiratory failure, renal failure, age over 65 years, and hyperdynamic states, in part because of the small number of patients in each group. These data are consistent with the hypothesis that the beta 2-adrenergic action of dobutamine vasodilates the previously constricted peripheral circulation, enhances tissue perfusion by improving micro-circulatory flow distribution, and improves DO2 and VO2.

The effect of dobutamine on myocardial performance and high-energy phosphate metabolism at different stages of heart failure in cardiomyopathic hamsters: a 31P MRS study

Dobutamine has been shown to exert disparate clinical effects in patients with cardiomyopathy and heart failure. This study evaluated the effects of dobutamine on hemodynamics and energetics in isolated, perfused myopathic hamster hearts at a moderate and advanced stage of heart failure. Biochemical changes were correlated with left ventricular developed pressure, coronary flow, and myocardial oxygen consumption. During dobutamine treatment left ventricular developed pressure increased in the control and moderate heart failure group 28.0 +/- 1.0% and 114.2 +/- 11.6%, respectively. Myocardial oxygen consumption increased 50.1 +/- 9.1% and 45.5 +/- 16.0%, respectively. There were no significant changes of left ventricular developed pressure and myocardial oxygen consumption in the advanced heart failure group. Inorganic phosphate (Pi) increased in the control group from 6.8 +/- 0.5 to 11.4 +/- 1.2 mmol (p less than 0.005) and in the advanced heart failure group from 10.4 +/- 1.1 to 15.3 +/- 1.2 mmol (p less than 0.01). Phosphocreatine (PCr) and beta-ATP (adenosine triphosphate) decreased in the control group from 12.2 +/- 0.4 to 8.7 +/- 0.7 mmol (p less than 0.001) and 10.4 +/- 0.8 to 7.7 +/- 0.7 mmol (p less than 0.02), respectively. PCr/Pi ratio, reflecting mitochondrial function, fell in the control and advanced heart failure group from 1.84 +/- 0.14 to 0.84 +/- 0.14 (p less than 0.02) and 0.81 +/- 0.16 to 0.37 +/- 0.08 (p less than 0.03), respectively. Thus in cardiomyopathic hamsters dobutamine improved mechanical performance and thermodynamic efficiency in moderate stages of heart failure by improving mitochondrial activity, but did not improve mechanical performance in an advanced stage of heart failure. These experiments provide into the disparate clinical effects of dobutamine at various stages of heart failure.

Practical use of duplex Doppler analysis of the renal vasculature in critically ill patients

Duplex doppler examination of blood flow in renal interlobar arteries was analysed in twelve critically ill patients before and during low-dose dopamine infusion (2 micrograms/kg/min). Renal vasodilatation and increased blood flow were observed with dopamine, confirming results with indirect or invasive techniques. The doppler ultrasound technique is entirely non-invasive, is simple and quick to carry out, provides instant results, and will allow tailoring of inotropic support in critically ill patients to provide optimum renal blood flow.

Management of myocardial infarction shock: current status

Major advances have occurred over the last two decades in the management of myocardial infarction shock, increasing the overall in-hospital survival rate from approximately 15% to more than 50% at the present time with aggressive methods of interventional cardiology. The widespread use of intravenous thrombolytic therapy during the early hours of myocardial infarction has resulted in a decreasing incidence of shock with first myocardial infarctions. Three mechanisms bring about cardiogenic shock: (1) extensive aggregate systolic left ventricular dysfunction, (2) extensive right ventricular infarction, and (3) mechanical defects of the left and/or right ventricles attendant to ischemic dysfunction or rupture. To permit survival in cardiogenic shock, even with maximally aggressive therapy, diagnostic evaluation must be carried out concurrently with clinical stabilization of the patient. IABC is the mainstay for supporting the patient in shock during further efforts at diagnosis and definitive therapy. Definitive therapy for cardiogenic shock may include percutaneous transluminal coronary angioplasty, emergent bypass surgery, or repair of a mechanical defect. This report details the current status of knowledge with respect to pathogenesis, recognition, and definitive treatment of myocardial infarction shock.

Inotropic, vascular and neuroendocrine effects of dopexamine hydrochloride and comparison with dobutamine

Dopexamine hydrochloride is a novel beta 2- and dopaminergic-receptor agonist proposed for intravenous therapy in patients with congestive heart failure. To gain a clearer knowledge of its efficacy relative to other agents, intravenous infusions of dopexamine hydrochloride (4 micrograms/kg/min) and dobutamine (10 micrograms/kg/min) were administered to 10 patients with congestive heart failure (ejection fraction less than 0.4). Both agents increased stroke volume and cardiac indexes to a similar degree, and both decreased systemic vascular resistance, with a trend toward a greater decrease with dopexamine hydrochloride. Although dobutamine had no significant effect on left ventricular systolic pressure, dopexamine hydrochloride caused a decrease from 121 +/- 8 to 110 +/- 7 mm Hg (p less than 0.01). Both dobutamine and dopexamine hydrochloride increased peak rate of left ventricular pressure development (dP/dt), and there was a trend to a greater increase with dobutamine (control 1,043 +/- 102 mm Hg/s; dobutamine 1,340 +/- 142 mm Hg/s; dopexamine hydrochloride 1,213 +/- 120 mm Hg/s, p = 0.067 vs dobutamine). Plasma norepinephrine levels increased only with dopexamine hydrochloride (+49%, p less than 0.05). Plasma renin activity increased with both agents (dobutamine +38%, p less than 0.06; dopexamine hydrochloride +41%, p less than 0.05). Dobutamine and dopexamine hydrochloride, therefore, improve cardiac function by way of both vasodilator and inotropic mechanisms. At the doses administered, dopexamine hydrochloride relies on a greater systemic vasodilator effect than dobutamine to achieve and increase in left ventricular performance. Increased levels of endogenous catecholamines may contribute to the increased inotropic state with dopexamine hydrochloride.

[Indications for inotropic agents in cardiac surgery]

Inotropic drugs are widely used before, during and after cardiac surgery. Besides the old well known inotropic drugs, new sympathomimetic drugs and phosphodiesterase inhibitors are available. They can be used alone or in combination. The choice of drug is difficult to make and depends, for one part, on the side-effects of each drug. Before surgery, they are required for patients who present with cardiogenic shock while waiting for emergency repair of their lesion. During surgery, inotropic drugs are used before, during and after using cardiopulmonary bypass. After surgery, they are used to treat low cardiac output states. A decision algorithm is suggested, but it is modified by personal clinical experience, aetiological patterns and pharmacological data. Therapeutic doses must be adjusted according to haemodynamic data. Physiological controls are required, such as venous return and heart rate. Mechanical assistance devices must not be forgotten, especially after myocardial reperfusion and weaning from extracorporeal circulation.