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

Inotropic Agents: Are We Still in the Middle of Nowhere?

Inotropes are prescribed to enhance myocardial contractility while vasopressors serve to improve vascular tone. Although these medications remain a life-saving therapy in cardiovascular clinical scenarios with hemodynamic impairment, the paucity of evidence on these drugs makes the choice of the most appropriate vasoactive agent challenging. As such, deep knowledge of their pharmacological and hemodynamic effects becomes crucial to optimizing hemodynamic profile while reducing the potential adverse effects. Given this perspective, it is imperative for cardiologists to possess a comprehensive understanding of the underlying mechanisms governing these agents and to discern optimal strategies for their application across diverse clinical contexts. Thus, we briefly review these agents' pharmacological and hemodynamic properties and their reasonable clinical applications in cardiovascular settings. Critical interpretation of available data and the opportunities for future investigations are also highlighted.

Response of hypotensive dogs to dopamine hydrochloride and dobutamine hydrochloride during deep isoflurane anesthesia

OBJECTIVE

To evaluate the dose-related cardiovascular and urine output (UrO) effects of dopamine hydrochloride and dobutamine hydrochloride, administered individually and in combination at various ratios, and identify individual doses that achieve target mean arterial blood pressure (MAP; 70 mm Hg) and cardiac index (CI; 150 mL/kg/min) in dogs during deep isoflurane anesthesia.

ANIMALS

10 young clinically normal dogs.

PROCEDURES

Following isoflurane equilibration at a baseline MAP of 50 mm Hg on 3 occasions, dogs randomly received IV administration of dopamine (3, 7, 10, 15, and 20 microg/kg/min), dobutamine (1, 2, 4, 6, and 8 microg/kg/min), and dopamine-dobutamine combinations (3.5:1, 3.5:4, 7:2, 14:1, and 14:4 microg/kg/min) in a crossover study. Selected cardiovascular and UrO effects were determined following 20-minute infusions at each dose.

RESULTS

Dopamine caused significant dose-dependent responses and achieved target MAP and CI at 7 microg/kg/min; dobutamine at 2 microg/kg/min significantly affected only CI values. At any dose, dopamine significantly affected UrO, whereas dobutamine did not. Target MAP and CI values were achieved with a dopamine-dobutamine combination at 7:2 microg/kg/min; a dopamine-related dose response for MAP and dopamine- and dobutamine-related dose responses for CI were identified. Changes in UrO were associated with dopamine only.

CONCLUSIONS AND CLINICAL RELEVANCE

In isoflurane-anesthetized dogs, a guideline dose for dopamine of 7 microg/kg/min is suggested; dobutamine alone did not improve MAP. Data regarding cardiovascular and UrO effects indicated that the combination of dopamine and dobutamine did not provide greater benefit than use of dopamine alone in dogs.

Selecting a Vasopressor Drug for Vasoplegic Shock After Adult Cardiac Surgery: A Systematic Literature Review

The choice of vasopressors to treat vasodilatory shock after cardiac surgery is a matter of controversy. We have systematically reviewed the literature and found that the data are insufficient to guide choice of agent. However, we found sufficient evidence that when a target blood pressure can not be achieved with a single agent, addition of another is more likely to help achieve the blood pressure target. We also found that there is no evidence that vasopressors induce organ ischemia. Finally, the lack of high quality data indicate that large multicenter trials are needed in this field.

Bench-to-bedside review: Inotropic drug therapy after adult cardiac surgery -- a systematic literature review

Many adult patients require temporary inotropic support after cardiac surgery. We reviewed the literature systematically to establish, present and classify the evidence regarding choice of inotropic drugs. The available evidence, while limited in quality and scope, supports the following observations; although all β-agonists can increase cardiac output, the best studied β-agonist and the one with the most favourable side-effect profile appears to be dobutamine. Dobutamine and phosphodiesterase inhibitors (PDIs) are efficacious inotropic drugs for management of the low cardiac output syndrome. Dobutamine is associated with a greater incidence of tachycardia and tachyarrhythmias, whereas PDIs often require the administration of vasoconstrictors. Other catecholamines have no clear advantages over dobutamine. PDIs increase the likelihood of successful weaning from cardiopulmonary bypass as compared with placebo. There is insufficient evidence that inotropic drugs should be selected for their effects on regional perfusion. PDIs also increase flow through arterial grafts, reduce mean pulmonary artery pressure and improve right heart performance in pulmonary hypertension. Insufficient data exist to allow selection of a specific inotropic agent in preference over another in adult cardiac surgery patients. Multicentre randomized controlled trials focusing on clinical rather than physiological outcomes are needed.

Life-threatening complications of systemic sclerosis

Pulmonary arterial hypertension is common in patients with SSc. Fig. 1 shows the diagnostic and therapeutic approach to PAH in SSc. Doppler echocardiography may suggest the diagnosis, but RHC is necessary to confirm PAH and to measure vasoreactivity. Therapy is directed at the underlying connective tissue disease. Vasoreactive patients often benefit from therapy with high-dose calcium-channel [figure: see text] blockers, but most patients are not vasoreactive. Intravenous epoprostenol and oral endothelin-1 receptor antagonists improve hemodynamic measurements and symptoms in SSc-associated PAH. The therapy of right ventricular failure is focused on vasodilators, inotropes, and diuretics with careful attention to avoiding systemic hypotension. The scleroderma pulmonary-renal syndrome and the scleroderma renal crisis are distinct syndromes with different clinical presentations, histopathologic manifestations, treatments, and outcomes. The scleroderma pulmonary renal syndrome is an autoimmune vasculitis of kidney and lung associated with normal blood pressure. Treatment is supportive, and prognosis is dismal. In contrast, scleroderma renal crisis is associated with systemic hypertension, onion skinning of afferent arterioles, and response to ACE inhibition and renal replacement therapy. Pericardial effusions are common but only occasionally lead to tamponade. Esophageal dysmotility is often associated with aspiration, leading to pulmonary fibrosis, pneumonia, or ARDS. Diffuse bowel involvement may result in pseudo-obstruction, bacterial overgrowth, or malabsorption. Prokinetic agents, antibiotics, and parenteral nutrition may be required.

Right ventricular injury in young swine: effects of catecholamines on right ventricular function and pulmonary vascular mechanics

Acute right ventricular (RV) injury is commonly encountered in infants and children after cardiac surgery. Empiric medical therapy for these patients results from a paucity of data on which to base medical management and the absence of animal models that allow rigorous laboratory testing. Specifically, exogenous catecholamines have unclear effects on the injured right ventricle and pulmonary vasculature in the young. Ten anesthetized piglets (9-12 kg) were instrumented with epicardial transducers, micromanometers, and a pulmonary artery flow probe. RV injury was induced with a cryoablation probe. Dopamine at 10 microg/kg/min, dobutamine at 10 microg/kg/min, and epinephrine (EP) at 0.1 microg/kg/min were infused in a random order. RV contractility was evaluated using preload recruitable stroke work. Diastolic function was described by the end-diastolic pressure-volume relation, peak negative derivative of the pressure waveform, and peak filling rate. In addition to routine hemodynamic measurements, Fourier transformation of the pressure and flow waveforms allowed calculation of input resistance, characteristic impedance, RV total hydraulic power, and transpulmonary vascular efficiency. Cryoablation led to a stable reproducible injury, decreased preload recruitable stroke work, and impaired diastolic function as measured by all three indices. Infusion of each catecholamine improved preload recruitable stroke work and peak negative derivative of the pressure waveform. Dobutamine and EP both decreased indices of pulmonary vascular impedance, whereas EP was the only inotrope that significantly improved transpulmonary vascular efficiency. Although all three inotropes improved systolic and diastolic RV function, only EP decreased input resistance, decreased pulmonary vascular resistance, and increased transpulmonary vascular efficiency.

Continuous home ambulatory intravenous inotropic drug therapy in severe heart failure: safety and cost efficacy

Some patients with dilated cardiomyopathy who are inotrope dependent but remain well by undergoing infusions can be managed by ambulatory infusions at home. We report our results in 20 patients awaiting heart transplantation, unable to be weaned from intravenous inotropic therapy on 2 or more occasions, but who were well while receiving inotropes and received home ambulatory infusions. The patients were treated with ACE inhibitors, digoxin, diuretics, vasodilators, close electrolyte management, and low-dose amiodarone for those with more than four-beat ventricular tachycardia. Infusions were delivered by a tunneled subclavian catheter and syringe driver. Thirteen patients received dopamine, four received dobutamine, and three received both. Mean duration of inotropic therapy was 5 months with 70% of the time spent as an outpatient. Eleven patients received transplants, two remain on the waiting list, and seven died after being removed from the list because of general deterioration or renal dysfunction. There were no sudden deaths. Actuarial survival was 71% at 3 months, which is not less than that expected for an inotrope-dependent population. All patients with idiopathic dilated cardiomyopathy survived to transplantation. In contrast, all three with right heart failure caused by pulmonary vascular disease and four of seven with ischemic cardiomyopathy died. Inpatient days were reduced by 70%, leading to considerable cost savings. Home ambulatory inotropic therapy is safe, cost-effective, best suited to those with idiopathic dilated cardiomyopathy, and dramatically reduces inpatient hospital duration.

Heart failure--outlooks and strategies for treatment

The outlook in heart failure patients with a dilated cardiomyopathy has improved dramatically over the past ten years. The availability of many excellent drugs apart from angiotensin II converting enzyme inhibitors (ACEI) has contributed to this. The best current survival rates reported are, however, in association with deliberate optimisation of haemodynamic parameters and incorporation of functional testing to monitor disease progression. These practises could well be adopted more widely in Australia and New Zealand. Surgical options for heart failure continue to expand, but apart from heart transplantation, remain somewhat experimental.

Renal dose dopamine does not alter the response to beta-adrenergic stimulation by isoproterenol in healthy human volunteers

OBJECTIVES

To determine if renal dose dopamine (3 microg/kg/min) alters the heart rate (HR) by itself, or if a dopamine infusion alters the HR response to bolus doses of the beta-adrenergic agonist isoproterenol in healthy human subjects.

DESIGN

Prospective study.

SETTING

Clinical laboratory of a university-affiliated academic medical center.

SUBJECTS

A total of 15 healthy nonpregnant women and men aged 21 to 44 years.

INTERVENTIONS

Subjects were monitored continuously with bedside ECG, pulse oximetry, and ambulatory ECG recording to measure the maximal HR response to separate injections of 10, 20, and 30 ng/kg of isoproterenol, given before, during, and after the infusion of 3 microg/kg/min of dopamine.

MEASUREMENTS AND MAIN RESULTS

Dopamine in the absence of isoproterenol did not alter baseline HR significantly (62.7+/-2.2 beats/min without dopamine; 65.4+/-2.2 with dopamine; p=0.15). All three doses of isoproterenol increased HR significantly above baseline, both in the presence and absence of dopamine (p<0.001). Dopamine infusion resulted in a higher HR following isoproterenol only for the 20-ng/kg dose. The incremental increases in HR, defined as the difference between peak HR following isoproterenol and baseline HR, were not increased during dopamine infusion for any of the doses of isoproterenol. Nausea was reported by 5 of the 15 subjects during the dopamine infusion.

CONCLUSIONS

In healthy human subjects, infusion of 3 microg/kg/min of dopamine does not significantly increase the HR when combined with beta-adrenergic stimulation using isoproterenol, suggesting neither an additive nor antagonistic interaction between the two drugs. While our study did not demonstrate an increase in HR in healthy subjects, the risk of increasing the chronotropic response to beta-adrenergic inotropic medications with "renal dose" dopamine in critically ill patients needs to be investigated. The frequency of nausea during dopamine infusion also may influence consideration of using dopamine to augment splanchnic blood flow and renal function in conscious patients.