Distinct modulation of myocardial performance, energy metabolism, and [Ca2+]i transients by positive inotropic drugs in normal and severely failing hamster hearts

The present study compared the effects of amrinone, dobutamine, dibutyryl cAMP, digoxin, and isoproterenol on mechanical performance, the high energy phosphate metabolites, and the [Ca2+]i transients in normal and cardiomyopathic hamster hearts with severe heart failure. In normal hearts dobutamine, dibutyryl cAMP, and isoproterenol increased left ventricular developed pressure, while amrinone and digoxin did not. However, the amplitude of [Ca2+]i transients was augmented with all drugs. Diastolic [Ca2+]i level was increased with dobutamine and lowered with dibutyryl cAMP and isoproterenol. In cardiomyopathic hearts with severe heart failure, left ventricular developed pressure, the amplitude of [Ca2+]i transients, the phosphorylation potential, and [cAMP]i were significantly depressed and left ventricular end-diastolic pressure and diastolic [Ca2+]i were significantly elevated when compared with normal hearts. Amrinone, dibutyryl cAMP, and isoproterenol improved mechanical performance while increasing [cAMP]i and the amplitude of [Ca2+]i transients, and decreasing diastolic [Ca2+]i. On the other hand, with dobutamine and digoxin diastolic [Ca2+]i was further increased and mechanical performance deteriorated with digoxin. Thus, distinct differences exist in modulation of mechanical performance, high-energy phosphate metabolism, and [Ca2+]i transients by positive inotropic drugs between normal and cardiomyopathic hearts with severe heart failure.

Reversal of 'refractory septic shock' by infusion of amrinone and angiotensin II in an anthracycline-treated patient

A 53-year-old granulocytopenic woman with malignant lymphoma treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy, including doxorubicin (Adriamycin) and autologues bone marrow transplantation, presented in the clinical state of "refractory septic shock" caused by Escherichia coli. Despite inotropic treatment with dopamine, dobutamine, and norepinephrine infusion, the patient's condition did not improve, but during treatment with amrinone and angiotensin II infusion, the septic shock was reversed. The patient was monitored with a pulmonary artery catheter and underwent repeated echocardiographic examinations. Antibiotic treatment with thienamycin and floxacillin was given. The initial reduction in cardiac performance in this patient may be explained by a state of true down-regulation of the myocardial beta-receptors. Apparently these beta-receptors were bypassed via the enzymatic action of amrinone upon cyclic monoadenosine phosphate. This is, to our knowledge, the first doxorubicin-treated patient with septic shock refractory to conventional vasopressor therapy whose condition reversed by inotropic treatment with amrinone and angiotensin II. This treatment may prove to be an alternative choice for patients developing "refractory septic shock" unresponsive to treatment with norepinephrine, dobutamine, and dopamine.

[Hemodynamic effects of amrinone on patients with moderate and severe cardiac dysfunction after open heart surgery]

Hemodynamic effects of amrinone and the changes in pulmonary shunt were studied in patients for open heart surgery. Eighteen patients were allocated into two groups (group L, H) on the first day of surgery. Group L consisted of 10 patients who received moderate-dose catecholamine (DOA + DOB < 12 micrograms.kg-1.min-1) and group H consisted of 8 patients who needed high-dose catecholamine (DOA + DOB > or = 12 micrograms.kg-1.min-1) to maintain normal hemodynamics. After baseline measurement, amrinone infusion was started and the dose was increased by every 2 hours (5, 10, 20 micrograms.kg-1.min-1). At dose of 20 micrograms.kg-1.min-1, cardiac index increased significantly in group L but not in group H. SVRI and PVRI decreased by dose related fashion in both groups. Systemic arterial pressure was unaltered in group L while it decreased significantly in group H. PaO2 decreased and pulmonary shunt increased in both groups. These results suggest that inotropic response of amrinone depends on the basal level of myocardial contractility although vasodilative property and the effect on the pulmonary shunt are almost similar in both groups.

Amrinone improves survival in hemorrhagic shock

Amrinone is a noncatecholamine inotropic agent used clinically in the management of heart failure. The purpose of this study was to determine if intravenous (i.v.) infusion of amrinone has beneficial effects during resuscitation from experimental hemorrhagic shock. Effectiveness was defined as significantly improved survival rate. Mean arterial pressure (MAP) and tissue oxygen tension (pO2) were measured to assess the physiologic effects of amrinone. Two separate randomized and blinded survival trials were conducted. In each trial, rats were randomly assigned to either a control group (n = 10) or an experimental group (n = 10). All animals were bled 27 ml/kg over 2 minutes and maintained in shock for 45 minutes before resuscitation. Resuscitation in placebo (control) animals was with 54 ml/kg (2 times the hemorrhage volume) Lactated Ringer's solution over 1 hour, whereas resuscitation in drug-treated animals was with a 0.75 mg/kg bolus amrinone over 3 minutes followed by 54 ml/kg Lactated Ringer's solution and 5 ug/kg/min infusion over 1 hour. Results were that resuscitation with amrinone significantly increased MAP, tissue pO2, and survival over resuscitation with Lactated Ringer's alone (P < 0.05). In both trials, survival rates increased by more than 66 per cent in the amrinone groups.

Thyrotoxicosis factitia in a post-aortocoronary bypass patient

A 52-yr-old man presented with an evolving myocardial infarction and unstable angina. Previously, he had undergone aortocoronary bypass surgery for triple vessel disease and at that time was diagnosed as hypothyroid. He had been refractory to thyroxine treatment and now required 0.3 mg thyroxine daily. On admission, he was hypertensive, tachycardic and found to be thyrotoxic secondary to excess thyroid hormone ingestion. Treatment with iopanoic acid was started. Despite medical therapy he continued to have unstable angina. Coronary angiography confirmed further triple vessel disease with blockage to his previous grafts. He was taken to surgery for coronary revascularization. On arriving in the intensive care unit he developed a thyroid storm. His temperature increased from 36.5 to 39.5 degrees C requiring a cooling blanket and cold irrigation down a nasogastric tube. An esmolol infusion was started to control his persistent tachycardia but this depressed his myocardial contractility. He required amrinone and noradrenaline infusions as further inotropic support. For sedation and muscle relaxation, intravenous propofol infusion and doxacurium were given. Over the following 20 hr the patient's condition stabilized. In conclusion, we describe the use of a short-acting beta blocker to avoid compromising an impaired myocardium during a thyroid storm which we could stop if the patient's cardiac condition deteriorated. In addition, amrinone, a phosphodiesterase inhibitor, was our inotrope of choice as it does not act on the already blocked beta adrenergic system.

[Effects of amrinone on left ventricular function following open heart surgery--analysis with left ventricular pressure volume loops]

The effects of Amrinone on cardiac function soon after extracorporeal circulation (ECC) were studied in 5 patients including mitral valvuloplasty, VSD closure, Fontan operation and coronary AV fistel closure. In all patients, left ventricular volume load decreased postoperatively. To evaluate the efficacy, we obtained left ventricular pressure-volume loops (P-V loop) before and after ECC and after intravenous administration of Amrinone (1 mg/kg) following ECC. P-V loops were produced by measuring left ventricular pressure using a Miller catheter which was retrogradely advanced from the ascending aorta into the left ventricle and by measuring left ventricular diameter to calculate left ventricular volume with Teichholtz' formula. Although no apparent difference of Emax was recognized before and after ECC, Emax increased from 3.2 +/- 2.5 mmHg/cm3 to 5.9 +/- 4.7 mmHg/cm3 after the administration of Amrinone. The left ventricular "systolic" pressure-volume area (PVA) which is the sum of stroke work (SW) and elastic potential energy decreased from 34.4 +/- 16.4 gm to 30.9 +/- 17.8 gm after Amrinone. No difference was also recognized in left ventricular end-diastolic pressure. Ejection fraction increased from 50 +/- 17.5% to 56.1 +/- 17.3%. These results suggested that Amrinone could improve the left ventricular function without prominent change in myocardial oxygen consumption immediately after open heart surgery.

Treatment of virus-induced myocardial injury with a novel immunomodulating agent, vesnarinone. Suppression of natural killer cell activity and tumor necrosis factor-alpha production

Controversy still exists concerning the therapy for viral myocarditis which manifests a wide variety of clinical symptoms. Vesnarinone, a quinolinone derivative that was developed as a positive inotropic agent with complex actions, including phosphodiesterase inhibition and cation channel modification, has recently been confirmed to improve the prognosis of patients with chronic heart failure. However, the precise mechanism of this beneficial effect is not yet clearly understood. In this study, using a murine model of acute viral myocarditis resulting from encephalomyocarditis virus infection, survival and myocardial damage were markedly improved by treatment with vesnarinone. In contrast, survival was not improved by treatment with amrinone, a phosphodiesterase inhibitor. Although vesnarinone did not inhibit viral replication or protect myocytes from viral direct cell injury, it did inhibit the increase in natural killer cell activity after viral infection. On the other hand, amrinone failed to inhibit natural killer cell activity. Both vesnarinone and amrinone suppressed the production of tumor necrosis factor-alpha. Therefore, we postulate that vesnarinone exerted its beneficial effects through an inhibition of natural killer cell activity, and that it serves as an immunomodulator providing new therapeutic possibilities for the treatment of viral myocarditis and/or immunological disorders.

An amrinone bolus prior to weaning from cardiopulmonary bypass improves cardiac function in mitral valve surgery patients

This double-blind, randomized study was performed to assess the effectiveness of a single bolus dose of 2 mg/kg of amrinone given during cardiopulmonary bypass (CPB) to patients undergoing mitral valve surgery. Outcome variables were hemodynamic function and the number and amount of vasopressors or inotropes required to wean from CPB. In amrinone-treated patients, cardiac index (CI) increased significantly by 48 +/- 14% following CPB (T3) versus 10 +/- 10% for placebo-treated patients (P = 0.029). Similarly, on arrival in the intensive care unit (T4), CI was increased by 52 +/- 20% in amrinone patients versus 8 +/- 8% for placebo patients (P = 0.04). There was a corresponding decrease in systemic vascular resistance index of 47 +/- 6% at T3 in the amrinone patients versus 10 +/- 14% in placebo patients (P = 0.001), and a decrease of 30 +/- 7% at T4 versus an increase of 10 +/- 22% for the placebo patients (P = 0.036). There was no difference in other measured hemodynamic variables. While on CPB, mean arterial pressure at 5 minutes following administration of the study drug was decreased in amrinone patients by 20 +/- 4% versus 4 +/- 3% in placebo patients (P = 0.005), but was no different at 10 and 15 minutes. There were no statistically significant differences in the number of patients who required supplemental inotropes or vasopressors either during CPB, following separation from CPB, or upon arrival in the ICU. Thus, amrinone improved CI without changing pulmonary vascular resistance or the requirement for supplemental inotropes or vasopressors in patients undergoing elective mitral valve surgery.

The role of amrinone in treating heart failure during and after coronary artery surgery supported by cardiopulmonary bypass

Amrinone and dobutamine compare favorably in the treatment of chronic congestive heart failure. There is increasing evidence that amrinone alone or in combination with a catecholamine may be used with considerable success in treating patients who are difficult to wean from cardiopulmonary bypass or who have a low cardiac output syndrome after coronary artery bypass grafting surgery. Amrinone increases intramyocardial cyclic adenosine monophosphate and exerts positive inotropic activity in addition to being a potent vasodilator. It may also improve diastolic function by increasing sarcoplasmic reticulum reuptake of calcium during diastole. It has been administered to patients prior to weaning from cardiopulmonary bypass and has improved hemodynamics and oxygen transport. When compared with dobutamine as primary treatment for depressed myocardial function in patients being weaned from cardiopulmonary bypass after coronary artery bypass grafting surgery, it was more effective in achieving primary treatment objectives. Patients given dobutamine had a higher incidence of myocardial infarction, ventricular fibrillation, supraventricular tachyarrhythmias, sinus tachycardia, and hypertension compared to those given amrinone. It is concluded that amrinone compares favorably with dobutamine and may even be superior when used as primary treatment for treating myocardial depression in patients having coronary artery surgery supported by cardiopulmonary bypass.

Labetalol overdose successfully treated with amrinone and alpha-adrenergic receptor agonists

Circulatory collapse and obtundation occurred in a 37-year-old woman following an iatrogenic overdose of labetalol. Conventional therapy with glucagon and alpha-adrenergic receptor-stimulating agents was ineffective in raising the patient's cardiac output or improving her mental status despite increasing the arterial pressure. The administration of amrinone was temporally associated with significant increases in the cardiac output accompanied by improved mental status. This case suggests that amrinone may be effective adjunctive therapy for beta-adrenergic receptor blocker overdoses by reversing their negative inotropic effects.

[Changes in oxygen delivery and consumption in different stages of chronic cor pulmonale]

To observe the changes of oxygen dynamic status in the development of chronic cor pulmonale, we studied early chronic cor pulmonale (group A, 13 cases), late chronic cor pulmonale in remission stage (group B, 15) and late chronic cor pulmonale in acute exacerbation stage (group C, 10) with Swan-Ganz thermodilution catheter and arterial and mixed venous blood gas analysis for detecting the oxygen delivery (DO2) and consumption (VO2). In group C, amrinone was given intravenously (15 micrograms.kg-1/min) and the examinations were repeated. DO2 (465 +/- 72 ml.min-1/m2) and VO2 (114 +/- 11 ml.min-1/m2) were at low level of normal range. No correlation was noted between them (r = 0.282, P > 0.05) in group A. It is suggested that the patient of early stage was in low oxygen delivery and consumption and no tissue oxygen deficit existed. In group B, DO2 and VO2 increased (592 +/- 111 and 145 +/- 32 ml.min-1/m2 respectively, P < 0.05 versus group A) but no significant correlation was found (r = 0.189, P > 0.05). Hence, the body of the patient was in high metabolic status and no tissue oxygen deficit existed in remission stage. DO2 and VO2 in group C (622 +/- 150, 139 +/- 44 ml.min-1/m2 respectively) were similar to those in group B (P < 0.05). After amrinone administration, a significant correlation was found between DO2 and VO2 (r = 0.39, P < 0.05). It is suggested that in the exacerbation stage, the patient's body was in highly metabolic status, the oxygen delivery-consumption compensation mechanism failed, and tissue oxygen deficit existed.

Effects of amrinone and dobutamine on PGF2 alpha-induced pulmonary hypertension in dogs

The hemodynamic benefits and pulmonary vascular selectivity of amrinone, dobutamine and amrinone + dobutamine were assessed in a canine model of vasoconstrictive pulmonary hypertension. Dogs were equipped with central and peripheral catheters and with an electromagnetic flow probe placed around the ascending aorta for the measurement of cardiac function. Through a laparotomy, an arteriovenous fistula was created between the abdominal aorta and the inferior vena cava. Gradual opening of this fistula, which permitted construction of pressure-flow curves (mean pulmonary artery pressure over the cardiac index, PAP/CI), was utilized to identify the pulmonary vascular effects of amrinone and dobutamine. PGF2 alpha, prostaglandin derivative, induced stable pulmonary hypertension along with significant reduction in CI. The resultant pulmonary hypertension translated into a significant increase in both the slope and pressure intercept of the PAP/CI curve. The bipyridine derivative, amrinone, did not reverse the CI reduction observed with PGF2 alpha: both mean arterial pressure and PAP were decreased as was the intercept of the PAP/CI curve. Dobutamine, a beta-agonist, reversed the CI decline elicited by PGF2 alpha but the elevated pulmonary pressure remained unaffected; dobutamine reduced the slope of the PAP/CI curve. When combined, amrinone and dobutamine demonstrated additive beneficial hemodynamic effects and improved lung perfusion. Their additive effects were also indicated by data on the PAP/CI curve: both the slope and the pressure intercept were significantly reduced. These results suggest that amrinone and dobutamine interact at different sites of the pulmonary vasculature and that their association might be beneficial in vasoconstrictive pulmonary hypertension although no significant pulmonary vascular selectivity could be observed.

Amrinone in cardiac surgical patients with left-ventricular dysfunction. A prospective, randomized placebo-controlled trial

STUDY OBJECTIVE

To evaluate the efficacy of amrinone for facilitating weaning from cardiopulmonary bypass (CPB).

DESIGN

Prospective, randomized, double-blind, placebo-controlled trial with epinephrine as "rescue" therapy.

SETTING

Operating room of a large, metropolitan tertiary-care center.

PATIENTS

Thirty-nine patients with preoperative left ventricular dysfunction undergoing cardiac surgery. Thirty-three patients underwent aortocoronary bypass grafting; six patients underwent valve replacement for severe mitral or aortic regurgitation.

INTERVENTIONS

Patients received either amrinone (1.5 mg/kg loading dose plus 10 micrograms/kg/min maintenance infusion; n = 20) or placebo (n = 19) in a randomized double-blind fashion shortly (median, 10.5 min; range, 2 to 24 min) before separation from CPB. Inotropic drugs (other than the study drug) were withheld prior to separation from CPB unless safety considerations demanded that the protocol be broken. Patients who could not be weaned from CPB, as well as those with a cardiac index of 2.2 L/min/m2 or less after weaning from CPB, received epinephrine (60 to 120 ng/kg/min) by infusion.

MEASUREMENTS AND RESULTS

Fourteen of 19 patients receiving placebo but only 1 of the 20 patients receiving amrinone (p = 0.00001) required epinephrine infusion to separate from bypass. The cardiac index of 4 patients receiving placebo (but no patients with amrinone) failed to exceed 2.2 L/min/m2 despite epinephrine infusion, requiring the protocol to be broken (p < 0.08). Blood concentrations of amrinone determined (only in the amrinone group) after separation from CPB confirmed that the dosage of amrinone produced an effective blood concentration. Fourteen of 19 patients receiving placebo and 17 of 20 patients receiving amrinone required an infusion of phenylephrine titrated to maintain systolic blood pressure less than 90 mm Hg. Seven patients (four with amrinone and three with placebo) required antiarrhythmic drug therapy. The outcome at 3 months was similar in the 2 groups.

CONCLUSIONS

Amrinone by itself is an effective agent to facilitate weaning from CPB, and therapy with amrinone reduced the need for individualized titration of epinephrine. Amrinone is as effective as individualized titration of epinephrine (after CPB) to improve cardiac function. Patients in the group receiving amrinone had no greater need for vasoconstricting agents than did patients in the group receiving placebo; however, proactive administration of amrinone before separation from CPB appears to offer no greater benefit to high-risk patients than selective administration of drugs (epinephrine) only to those patients who demonstrate the need for drug support at the time of weaning.

Pharmacologic reduction of pretransplantation pulmonary vascular resistance predicts outcome after pediatric heart transplantation

Pulmonary hypertension leading to donor right ventricular dysfunction remains a major risk factor associated with poor outcome after heart transplantation. This study evaluated a pretransplantation protocol to assess pulmonary vascular resistance index and its response to pharmacologic modulation. Cardiac catheterization was performed in 25 patients (mean age, 8.6 years [range, 1 to 17 years]; mean weight, 27.3 kg [range, 8.1 to 54 kg]) with end-stage heart failure. Mean pulmonary artery and capillary wedge pressures and cardiac index were measured in the baseline state and during administration of 100% oxygen, dobutamine at 10 micrograms/kg/min, and nitroprusside at 1 to 4 micrograms/kg/min. Transpulmonary pressure gradient and pulmonary vascular resistance index were calculated. In 22 survivors, hemodynamics were reassessed 1 and 4 weeks after transplantation. The mean cardiac index significantly increased (2.2 to 3.2 L/min/m2); transpulmonary pressure gradient (12.7 to 9.6 mm Hg) and pulmonary vascular resistance index (6.2 to 3.0 units/m2) decreased during the drug study. In 12 patients with a baseline pulmonary vascular resistance index of more than 6 units/m2, 10 survived heart transplantation. This study shows that pharmacologic reduction of the pulmonary vascular resistance index in the pretransplantation protocol predicts reduced pulmonary vascular resistance index and a favorable outcome after heart transplantation.

Effect of amrinone during group B Streptococcus-induced pulmonary hypertension in piglets

Intravenous infusion of group B Streptococcus (GBS) into neonatal animals produces pulmonary hypertension, ventilation/perfusion (VA/Q) mismatch, and an increase in serum levels of thromboxane B2 (TxB2) and tumor necrosis factor (TNF) alpha. The vasodilator amrinone (amr) is a cGMP-inhibited phosphodiesterase inhibitor and is reported to inhibit thromboxane A2 and TNF production. We hypothesized that infusion of amr would cause pulmonary vasodilation and reduce serum TxB2 and TNF levels in piglets with late phase GBS-induced pulmonary hypertension. The effect of amr on gas exchange was also determined. A continuous infusion of GBS was administered for 5 hr to 4 groups of anesthetized, mechanically ventilated neonatal piglets. An amr bolus of 8 mg/kg was given at 4 hr followed by a 1 hr continuous infusion of either 10 or 20 micrograms/kg/min of amr (amr 10 and amr 20, respectively). Control piglets received a bolus and 1 hr infusion of amr carrier. The infusion of amr, but not of carrier reversed late phase GBS-induced pulmonary hypertension. Piglets infused with amr 20 showed transient selective pulmonary vasodilation, based on a reduced ratio of pulmonary to systemic vascular resistance (PVR/SVR ratio) value at 30 min but not at 1 hr, compared to pre-amr treatment values. The PVR/SVR ratio values for amr 10 and control group did not change after treatment with either amr or carrier. Treatment with amr 10 or 20 did not decrease serum TxB2 or TNF levels or increase VA/Q mismatch.(ABSTRACT TRUNCATED AT 250 WORDS)

Amrinone therapy for severe pulmonary hypertension and biventricular failure after complicated valvular heart surgery

We report two cases in which amrinone was used effectively, in addition to the conventional sympathomimetic drug, for the emergence from cardiopulmonary bypass following complicated valvular heart surgery in patients who had severe pulmonary hypertension and biventricular failure. Amrinone was used in combination with isoproterenol in one and dopamine in the other case. The clinical changes were brought about by a 21.5 percent and 53.5 percent decrease in pulmonary blood pressure and pulmonary vascular resistance, respectively. Concomitantly, the mean systemic blood pressure was increased by 50 percent, whereas heart rate decreased by 17.5 percent. This report demonstrates that amrinone can be life-saving in patients with biventricular failure and severe pulmonary hypertension not responding to conventional beta-adrenergic and vasodilator drug therapy.

Beneficial effect of amrinone on the size of acute regional ischemia in isolated rabbit hearts

The effect of inotropes on myocardial ischemia is difficult to predict because they may influence the determinants of myocardial O2 demand and O2 supply differently. Several PDE-inhibitors have been reported to possess antiischemic properties related to their hemodynamic and O2-sparing effects. To assess whether PDE-inhibitors also possess direct cardioprotective properties, the effects of amrinone (2.5 x 10(-5) mol/L) in comparison to isoproterenol (5 x 10(-9) mol/L) and ouabain (1.5 x 10(-7) mol/L) were studied in isolated rabbit hearts perfused according to Langendorff at a constant pressure (70 cmH2O) and electrically driven at a constant pacing rate. Regional ischemia was induced by coronary artery ligation and quantified by epicardial NADH fluorescence. All substances significantly increased the actively developed left ventricular pressure to a similar extent (+20%) (P < 0.05). Coronary flow was significantly decreased by ouabain (-15%) and significantly increased by isoproterenol (+25%) and particularly by amrinone (+50%) (P < 0.05). Neither ouabain nor isoproterenol significantly changed the intensity or the distribution pattern of NADH fluorescence, whereas the size of the ischemic zone was significantly reduced by amrinone (-25%) (P < 0.05). The PDE-inhibitor amrinone was shown to possess a direct cardioprotective effect by improving myocardial perfusion and O2 supply in isolated rabbit hearts.

Hemodynamic effects of amrinone and colloid administration in children following cardiac surgery

Amrinone was used as the sole vasoactive medication in 9 of 14 children (aged 5 months to 8.25 years) given the drug following open repair of congenital cardiac lesions. Four children received a concomitant dopamine infusion and one infant had the infusion stopped after 5 hours for low mean arterial pressure (49 mmHg). In the 10 children receiving only amrinone, cardiac index increased 21% (range, 0 to 94%) after a total loading dose of 4.5 mg/kg given over 1 hour. Four of 14 patients (29%) required dopamine infusions to maintain mean arterial pressure over 55 mmHg and in these children cardiac index increased from baseline and was maintained during the amrinone infusion. Preload was held constant by administration of whole blood or plasmanate during amrinone loading; a decrease in systemic vascular resistance index was seen resulting in a stable arterial blood pressure. Minimal chronotropic effect was seen and no arrhythmias occurred. The sole child with postoperative pulmonary hypertension had a beneficial decrease in pulmonary artery pressure, increase in cardiac index, and stable systemic blood pressure during amrinone use. Cardiac index changes during amrinone loading in these children were variable and less clearly related to serum levels than reported in adults. Pharmacokinetic analysis in 12 children showed a clearance of 3.4 mL/min/kg, a volume of distribution of 1.65 L/kg, and an elimination half-life of 5.75 hours. Decreases in platelet counts were seen in 6 children and platelet transfusion was needed in 1; thus, serial platelet counts should be monitored.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined inotropic effects of amrinone and epinephrine after cardiopulmonary bypass in humans

Amrinone, a phosphodiesterase inhibitor, and epinephrine, an alpha- and beta-adrenergic receptor agonist, are inotropic drugs used during cardiac surgery to reverse myocardial depression after cardiopulmonary bypass. However, these drugs have not been compared separately, or in combination, in this patient population. We hypothesized that the combination might have complementary actions in improving myocardial function. We, therefore, compared amrinone, epinephrine, and the combination of amrinone and epinephrine in a randomized, blinded, placebo-controlled study in patients undergoing coronary artery bypass grafting. Forty patients with ejection fractions > 0.45 were studied. Right ventricular ejection fraction pulmonary artery catheters and radial arterial catheters were inserted before fentanyl-midazolam anesthesia. After separation from bypass, patients received either a placebo (n = 20) or amrinone bolus (1.5 mg/kg, n = 20) at time 0 and a placebo (n = 20) or epinephrine (30 ng.kg-1.min-1, n = 20) infusion at time 5 min. This resulted in four study groups, n = 10 in each group. Data were collected every 2.5 min for 10 min. Epinephrine, amrinone, and the combination of both drugs significantly increased cardiac output, stroke volume, O2 delivery, and left ventricular stroke work. The increase in stroke volume (P < 0.05) was 12 +/- 6, 16 +/- 4, and 30 +/- 4 mL/beat with epinephrine, amrinone, and the combination of amrinone and epinephrine, respectively. The amrinone-epinephrine combination increased stroke volume as much as the sum of amrinone and epinephrine given separately. Systemic vascular resistance and pulmonary vascular resistance decreased with amrinone and amrinone-epinephrine, but not with epinephrine. Epinephrine increased mean arterial and mean pulmonary arterial pressures. Right ventricular ejection fraction did not significantly increase (P = 0.09) with epinephrine, but increased significantly with amrinone (0.45 to 0.53, P = 0.01), and with the combination (0.43 to 0.55, P = 0.006). These data indicate that amrinone and epinephrine effectively increase myocardial performance during cardiac surgery. Right ventricular function especially was improved with amrinone and the combination of amrinone and epinephrine. The combined effects of amrinone and epinephrine may be useful in patients recovering from the ischemia and reperfusion injury resulting from coronary artery bypass grafting.

Early intervention of inotropic support in facilitating weaning from cardiopulmonary bypass: the New England Deaconess Hospital experience

The current article reviews the therapeutic advantages and disadvantages of early inotropic intervention prior to separation from cardiopulmonary bypass (CPB). Background information is provided on predictors of failure to wean as well as the multiple etiologies and consequences of the "failed wean" from CPB. Advantages of early inotropic intervention include (1) increased contractility, (2) resolution/prevention of ischemia, (3) attainment of therapeutic levels of drug, (4) minimization of inotropic side effects while on CPB, (5) avoidance of mechanical intervention (intra-aortic balloon pump), (6) dilatation of the internal mammary artery, and (7) prevention of the "failed wean". Disadvantages of early inotropic intervention include (1) unnecessary drug usage, (2) tachycardia/arrhythmias, (3) hyper/hypotension, (4) metabolic disturbances (hyperglycemia), (5) coagulation disorders, (6) need for additional drugs to treat side effects, (7) possible myocardial damage, and (8) additional costs. A brief review of this institution's preference for amrinone follows, including its pharmacology, side effects, and dosing prior to separation from CPB. Due to the large percentage of patients with diabetes mellitus undergoing cardiac surgery at our institution (approximately 30% to 40%) a synopsis of special inotropic considerations for this patient population is included.

Selecting an inotrope for the cardiac surgery patient

Although a wide variety of positive inotropic agents have been administered to cardiac surgery patients, few of them have been carefully studied in controlled clinical trials, in surgical patient populations. The limited data available suggest that one of the more widely used agents, calcium, may lack efficacy and possibly inhibit the actions of catecholamines. Dopamine, dobutamine, and dopexamine are highly effective agents, but more prone to produce tachycardia than epinephrine. Amrinone is an effective agent by itself, but is especially useful in combination with a beta-adrenergic agonist for patients with severe left-ventricular dysfunction.

Inotropic support of the heart that fails to successfully wean from cardiopulmonary bypass: the Montreal Heart Institute experience

The selection of an appropriate therapeutic regimen, especially in patients with preexisting cardiac dysfunction prior to surgery, is a crucial element for successful separation from cardiopulmonary bypass (CPB). At the present time there are no definitive studies to determine which treatment modality, or combination of treatments, is optimal in this patient population. A brief review of the literature is presented to answer the following questions: (1) Should inotropic support be administered in anticipation of failure to wean from CPB? and (2) Which inotrope or combination of drugs is best? There is no evidence at present that the prophylactic administration of inotropes to assist separation from CPB may result in damaging effects to the myocardium in humans. Inasmuch as tachycardia is avoided and coronary perfusion pressure is maintained within the normal range, prophylactic inotropes may be of benefit to patients with preexisting myocardial dysfunction during weaning from CPB by allowing a smoother separation and a shorter time on CPB. While no specific drug has been proven superior, the use of phosphodiesterase inhibitors as part of the regimen to provide inotropic support in these patients may exert a beneficial effect on myocardial ischemia and reperfusion injury. Prophylactic support of the circulation during separation from CPB, especially with phosphodiesterase inhibitors, may be indicated in this specific patient population as part of the strategy to ensure maximal preservation of myocardial function.

A comparison of combined amrinone and glucagon therapy to glucagon alone for cardiovascular depression associated with propranolol toxicity in a canine model

Multiple inotropic agents may be required to improve hypotension associated with beta-blocker toxicity. This study compared combined amrinone and glucagon therapy to glucagon alone and saline control for the treatment of propranolol-induced cardiovascular depression in a canine model. Six animals were pretreated with 10 mg/kg of propranolol intravenously (i.v.), which resulted in significant depression in heart rate (HR), cardiac output (CO), mean arterial pressure (MAP), and maximal left ventricular change in pressure over time (dP/dt max) (P < .0001). Each canine received i.v. amrinone (4 mg/kg) plus glucagon (20 micrograms/kg) therapy during a 2-minute period after propranolol infusion was completed. Cardiovascular parameters were monitored at 1, 6, 11, 21, and 31 minutes after treatment was rendered. Results were compared with those of a previous study, consisting of six animals that received glucagon therapy alone (20 mg/kg) and six controls (normal saline only) in an identical protocol. The addition of i.v. amrinone to glucagon therapy did not increase significantly, HR, CO, stroke volume, or dP/dt max compared with glucagon alone. Total systemic peripheral resistance was reduced significantly during 31 minutes of observation after the administration of combined therapy compared with the control; glucagon alone also reduced systemic peripheral resistance at 1 and 6 minutes. At all time periods except 1 minute of observation there was a significant reduction in MAP when comparing combined therapy with that of glucagon therapy alone. In this model, the addition of amrinone to glucagon therapy seems to have a detrimental effect on the ability of glucagon to increase MAP resulting from propranolol toxicity.

Use of amrinone and glucagon in a case of calcium channel blocker overdose

Hypotension resulting from calcium channel blocker ingestion often is refractory to standard therapeutic modalities. Amrinone and glucagon have been used separately and in combination with other agents in the treatment of calcium channel blocker overdose. We report the successful use of both amrinone and glucagon in the treatment of a 30-year-old woman who ingested 3.6 g of verapamil and presented with refractory hypotension. The use of the two agents together may provide improved inotropic support with minimal increases in myocardial oxygen consumption. In this case, the combination of amrinone and glucagon was safe and effective in the management of the hemodynamic instability associated with calcium channel blocker overdose.