Pharmacology of bipyridine phosphodiesterase III inhibitors

Pressure Overload and Right Ventricular Failure: From Pathophysiology to Treatment

Right ventricular failure (RVF) is often caused by increased afterload and disrupted coupling between the right ventricle (RV) and the pulmonary arteries (PAs). After a phase of adaptive hypertrophy, pressure-overloaded RVs evolve towards maladaptive hypertrophy and finally ventricular dilatation, with reduced stroke volume and systemic congestion. In this article, we review the concept of RV-PA coupling, which depicts the interaction between RV contractility and afterload, as well as the invasive and non-invasive techniques for its assessment. The current principles of RVF management based on pathophysiology and underlying etiology are subsequently discussed. Treatment strategies remain a challenge and range from fluid management and afterload reduction in moderate RVF to vasopressor therapy, inotropic support and, occasionally, mechanical circulatory support in severe RVF.

Intravenous milrinone for treatment of delayed cerebral ischaemia following subarachnoid haemorrhage: a pooled systematic review

Small trials have demonstrated promising results utilising intravenous milrinone for the treatment of delayed cerebral ischaemia (DCI) after subarachnoid haemorrhage (SAH). Here we summarise and contextualise the literature and discuss the future directions of intravenous milrinone for DCI. A systematic, pooled analysis of literature was performed in accordance with the PRISMA statement. Methodological rigour was analysed using the MINORS criteria. Extracted data included patient population; treatment protocol; and clinical, radiological, and functional outcome. The primary outcome was clinical resolution of DCI. Eight hundred eighteen patients from 10 single-centre, observational studies were identified. Half (n = 5) of the studies were prospective and all were at high risk of bias. Mean age was 52 years, and females (69%) outnumbered males. There was a similar proportion of low-grade (WFNS 1-2) (49.7%) and high-grade (WFNS 3-5) (50.3%) SAH. Intravenous milrinone was administered to 523/818 (63.9%) participants. Clinical resolution of DCI was achieved in 375/424 (88%), with similar rates demonstrated with intravenous (291/330, 88%) and combined intra-arterial-intravenous (84/94, 89%) therapy. Angiographic response was seen in 165/234 (71%) receiving intravenous milrinone. Hypotension (70/303, 23%) and hypokalaemia (31/287, 11%) were common drug effects. Four cases (0.5%) of drug intolerance occurred. Good functional outcome was achieved in 271/364 (74%) patients. Cerebral infarction attributable to DCI occurred in 47/250 (19%), with lower rates in asymptomatic spasm. Intravenous milrinone is a safe and feasible therapy for DCI. A signal for efficacy is demonstrated in small, low-quality trials. Future research should endeavour to establish the optimal protocol and dose, prior to a phase-3 study.

Comparison of Enoximone, Amrinone, or Levosimendan Enriched St. Thomas’ Hospital Cardioplegic Solutions Used for Myocardial Preservation in Isolated Guinea Pig Hearts

Myocardial contractile function after cardioplegic arrest is often depressed and an ideal cardioplegic solution has not been developed yet. The aim of this study was to assess the efficacy of phosphodiesterase III inhibitors, amrinone and enoximone, and levosimendan, a novel Ca2+ sensitizing agent, on recovery of hearts after normothermic cardioplegic arrest when added to the St. Thomas’ hospital cardioplegic solution. In the control group, isolated guinea pig hearts were perfused in Langendorff apparatus and arrested with standard St. Thomas’ solution. In other groups, amrinone (10-5 mol.L-1), levosimendan (10-5 mol.L-1), or enoximone (10-4 mol.L-1) were added to the cardioplegic solution. In all hearts, intraventricular pressure, +dp/dtmax, -dp/dtmax, area under pressure-time curve, heart rate, coronary flow, lactate dehydrogenase and creatine kinase enzyme leakage, and oxygen consumption were measured. In the enoximone group, contractility force and +dp/dtmax, were found to be significantly high in the reperfusion and inotropic periods in comparison with other groups (p<0.05). -dp/dtmax and area under contractility-time curve values were significantly high in inotropic period in enoximone group (p<0.05). No statistically significant difference was noted in other groups. Cardioplegic solution enrichment with enoximone augmented mechanic functions in reperfusion period. No positive effect of amrinone or levosimendan was observed in this study.

Inotropic effects of a single intravenous recommended dose of pimobendan in healthy dogs

We investigated the effects of an injectable pimobendan solution (0.15 mg/kg) on cardiac function in healthy dogs. Fifteen dogs were divided into placebo, intravenous pimobendan injection, and subcutaneous pimobendan injection groups. In the placebo, the heart rate, systolic and end-diastolic left ventricular pressure (LVPs and LVEDP), and peak positive (max dP/dt) and negative (min dP/dt) first derivatives of the left ventricular pressure did not change for 60 min. After the intravenous pimobendan injection, LVEDP decreased significantly within 5 min, while the max dP/dt increased, and the effects continued until 60 min. In comparison, there were no hemodynamic changes after the subcutaneous pimobendan injection. This study demonstrates that injectable pimobendan induced a rapid inotropic effect and decreased the LVEDP in dogs.

Postoperative management of heart failure in pediatric patients

Low cardiac output syndrome (LCOS) is a well-described entity occurring in 25-65% of pediatric patients undergoing open-heart surgery. With judicious intensive care management of LCOS, most patients have an uncomplicated postoperative course, and within 24 h after cardiopulmonary bypass, the cardiac function returns back to baseline. Some patients have severe forms of LCOS not responsive to medical management alone, requiring temporary mechanical circulatory support to prevent end-organ injury and to decrease myocardial stress and oxygen demand. Occasionally, cardiac function does not recover and heart transplantation is necessary. Long-term mechanical circulatory support devices are used as a bridge to transplantation because of limited availability of donor hearts. Experience in usage of continuous flow ventricular assist devices in the pediatric population is increasing.

Intensive symptom control of opioid-refractory dyspnea in congestive heart failure: Role of milrinone in the palliative care unit

OBJECTIVE

We describe an exemplary case of congestive heart failure (CHF) symptoms controlled with milrinone. We also analyze the benefits and risks of milrinone administration in an unmonitored setting.

METHOD

We describe the case of a patient with refractory leukemia and end-stage CHF who developed severe dyspnea after discontinuation of milrinone. At that point, despite starting opioids, she had been severely dyspneic and anxious, requiring admission to the palliative care unit (PCU) for symptom control. After negotiation with hospital administrators, milrinone was administered in an unmonitored setting such as the PCU. A multidisciplinary team approach was also provided.

RESULTS

Milrinone produced a dramatic improvement in the patient's symptom scores and performance status. The patient was eventually discharged to home hospice on a milrinone infusion with excellent symptom control.

SIGNIFICANCE OF RESULTS

This case suggests that milrinone may be of benefit for short-term inpatient administration for dyspnea management, even in unmonitored settings and consequently during hospice in do-not-resuscitate (DNR) patients. This strategy may reduce costs and readmissions to the hospital related to end-stage CHF.

Management of Right Heart Failure in the Intensive Care Unit

Right heart failure is a clinical syndrome of various causes that commonly involves failure of the right ventricle (RV). The hemodynamic hallmark of the syndrome is increasing central venous pressure and worsening cardiac output with a rising RV end-diastolic pressure. When dealing with RV failure, clinicians must assess and optimize the intravascular volume state, support RV contractility, and address any pathologic elevations of afterload so that systemic perfusion is preserved. Despite these measures, there may still be a need to offer rescue interventions to the failing RV in carefully selected patients.

Milrinone and esmolol decrease cardiac damage after resuscitation from prolonged cardiac arrest

BACKGROUND

Long-term survival after cardiac arrest (CA) due to shock-refractory ventricular fibrillation (VF) is low. Clearly, there is a need for new pharmacological interventions in the setting of cardiopulmonary resuscitation (CPR) to improve outcome. Here, hemodynamic parameters and cardiac damage are compared between the treatment group (milrinone, esmolol and vasopressin) and controls (vasopressin only) during resuscitation from prolonged CA in piglets.

METHODS

A total of 26 immature male piglets were subjected to 12-min VF followed by 8-min CPR. The treatment group (n=13) received i.v. (intravenous) boluses vasopressin 0.4 U/kg, esmolol 250 μg/kg and milrinone 25 μg/kg after 13 min, followed by i.v. boluses esmolol 375 μg/kg and milrinone 25 μg/kg after 18 min and continuous esmolol 15 μg/kg/h infusion during 180 min reperfusion, whereas controls (n=13) received equal amounts of vasopressin and saline. A 200 J monophasic counter-shock was delivered to achieve resumption of spontaneous circulation (ROSC) after 8 min CPR. If ROSC was not achieved, another 200 J defibrillation and bolus vasopressin 0.4 U/kg would be administered in both groups. Direct current shocks at 360 J were applied as one shot per minute over maximally 5 min. Hemodynamic variables and troponin I as a marker of cardiac injury were recorded.

RESULTS

Troponin I levels after 180 min reperfusion were lower in the treatment group than in controls (P<0.05). The treatment group received less norepinephrine (P<0.01) and had greater diuresis (P<0.01). There was no difference in survival between groups.

CONCLUSION

The combination of milrinone, esmolol and vasopressin decreased cardiac injury compared with vasopressin alone.

Cerebral vasospasm

Cerebral vasospasm causes delayed ischemic neurologic deficits after aneurysmal subarachnoid hemorrhage. This is a well-established clinical entity with significant associated morbidity and mortality. The underlying patholphysiology is highly complex and poorly understood. Large-vessel vasospasm, autoregulatory dysfunction, inflammation, genetic predispositions, microcirculatory failure, and spreading cortical depolarization are aspects of delayed neurologic deterioration that have been described in the literature. This article presents a perspective on cerebral vasospasm, as guided by the literature to date, specifically examining the mechanism, diagnosis, and treatment of cerebral vasospasm.

Current options for the management of aneurysmal subarachnoid hemorrhage-induced cerebral vasospasm: a comprehensive review of the literature

OBJECTIVES

Cerebral vasospasm is one of the leading causes of morbi-mortality following aneurysmal subarachnoid hemorrhage. The aim of this article is to discuss the current status of vasospasm therapy with emphasis on endovascular treatment.

METHODS

A comprehensive review of the literature obtained by a PubMed search. The most relevant articles related to medical, endovascular and alternative therapies were selected for discussion.

RESULTS

Current accepted medical options include the oral nimodipine and 'triple-H' therapy (hypertension, hypervolemia and hemodilution). Nimodipine remains the only modality proven to reduce the incidence of infarction. Although widely used, 'triple-H' therapy has not been demonstrated to significantly change overall outcome after cerebral vasospasm. Indeed, both induced hypervolemia and hemodilution may have deleterious effects, and more recent physiologic data favor normovolemia with induced hypertension or optimization of cardiac output. Endovascular options include percutaneous transluminal balloon angioplasty (PTA) and intra-arterial (IA) infusion of vasodilators. Multiple case reports and case series have been encountered in the literature using different drug regimens with diverse mechanisms of action. Compared with PTA, IA drug infusion has the advantages of distal penetration and a better safety profile. Its main disadvantages are the more frequent need for repeat treatments and its systemic hemodynamic repercussions. Alternative options using intraventricular/cisternal drug therapy and flow augmentation strategies have also shown possible benefits; however, their use is not yet as well established.

CONCLUSION

Blood pressure or cardiac output optimization should be the mainstay of hyperdynamic therapy. Endovascular treatment appears to have a positive impact on neurological outcome compared with the natural history of the disease. The role of intraventricular therapy and flow augmentation strategies in association with medical and endovascular treatment may, in the future, play a growing role in the management of patients with severe refractory vasospasm.

Population pharmacokinetics of olprinone in healthy male volunteers

BACKGROUND

Olprinone decreases the cardiac preload and/or afterload because of its vasodilatory effect and increases myocardial contractility by inhibiting phosphodiesterase III.

PURPOSE

The objective of this study was to characterize the population pharmacokinetics of olprinone after a single continuous infusion in healthy male volunteers.

METHODS

We used 500 plasma concentration data points collected from nine healthy male volunteers for the study. The population pharmacokinetic analysis was performed using the nonlinear mixed effect model (NONMEM®) software.

RESULTS

The time course of plasma concentration of olprinone was best described using a two-compartment model. The final pharmacokinetic parameters were total clearance (7.37 mL/minute/kg), distribution volume of the central compartment (134 mL/kg), intercompartmental clearance (7.75 mL/minute/kg), and distribution volume of the peripheral compartment (275 mL/kg). The interindividual variability in the total clearance was 12.4%, and the residual error variability (exponential and additive) were 22.2% and 0.129 (standard deviation). The final pharmacokinetic model was assessed using a bootstrap method and visual predictive check.

CONCLUSION

We developed a population pharmacokinetic model of olprinone in healthy male adults. The bootstrap method and visual predictive check showed that this model was appropriate. Our results might be used to develop the population pharmacokinetic model in patients.

Platelet cAMP and cGMP Phosphodiesterases

Platelets respond to a wide variety of exogenous agonists that bind to distinct receptors on the platelet surface resulting in the intracellular generation of second messengers or the opening of ion channels, setting off a cascade of events leading to both physical and functional changes in the platelet. The cyclic nucleotides, cyclic adenosine 3'5'-monophosphate (CAMP) and cyclic guanosine 3'5'-monophosphate (cGMP) initiate a sequence of intracellular events that modulate many of these reactions in the platelet.

Pulmonary vascular and right ventricular dysfunction in adult critical care: current and emerging options for management: a systematic literature review

INTRODUCTION

Pulmonary vascular dysfunction, pulmonary hypertension (PH), and resulting right ventricular (RV) failure occur in many critical illnesses and may be associated with a worse prognosis. PH and RV failure may be difficult to manage: principles include maintenance of appropriate RV preload, augmentation of RV function, and reduction of RV afterload by lowering pulmonary vascular resistance (PVR). We therefore provide a detailed update on the management of PH and RV failure in adult critical care.

METHODS

A systematic review was performed, based on a search of the literature from 1980 to 2010, by using prespecified search terms. Relevant studies were subjected to analysis based on the GRADE method.

RESULTS

Clinical studies of intensive care management of pulmonary vascular dysfunction were identified, describing volume therapy, vasopressors, sympathetic inotropes, inodilators, levosimendan, pulmonary vasodilators, and mechanical devices. The following GRADE recommendations (evidence level) are made in patients with pulmonary vascular dysfunction: 1) A weak recommendation (very-low-quality evidence) is made that close monitoring of the RV is advised as volume loading may worsen RV performance; 2) A weak recommendation (low-quality evidence) is made that low-dose norepinephrine is an effective pressor in these patients; and that 3) low-dose vasopressin may be useful to manage patients with resistant vasodilatory shock. 4) A weak recommendation (low-moderate quality evidence) is made that low-dose dobutamine improves RV function in pulmonary vascular dysfunction. 5) A strong recommendation (moderate-quality evidence) is made that phosphodiesterase type III inhibitors reduce PVR and improve RV function, although hypotension is frequent. 6) A weak recommendation (low-quality evidence) is made that levosimendan may be useful for short-term improvements in RV performance. 7) A strong recommendation (moderate-quality evidence) is made that pulmonary vasodilators reduce PVR and improve RV function, notably in pulmonary vascular dysfunction after cardiac surgery, and that the side-effect profile is reduced by using inhaled rather than systemic agents. 8) A weak recommendation (very-low-quality evidence) is made that mechanical therapies may be useful rescue therapies in some settings of pulmonary vascular dysfunction awaiting definitive therapy.

CONCLUSIONS

This systematic review highlights that although some recommendations can be made to guide the critical care management of pulmonary vascular and right ventricular dysfunction, within the limitations of this review and the GRADE methodology, the quality of the evidence base is generally low, and further high-quality research is needed.

Effect of vasodilation by milrinone, a phosphodiesterase III inhibitor, on vasospastic arteries after a subarachnoid hemorrhage in vitro and in vivo: effectiveness of cisternal injection of milrinone

OBJECTIVE

Cerebral vasospasm remains a major cause of morbidity and mortality. Milrinone, a bipyridine phosphodiesterase III inhibitor, is a potent member of the inodilator class of cardiac agents for vasospasm and is injected intra-arterially or intracisternally. There have been no studies investigating the duration of action (context-sensitive half-life) of milrinone for vasospasm or the most effective route of administration (intra-arterial versus intracisternal). We examined the effects of intracisternal and intra-arterial injection of milrinone on chronic cerebral vasospasm in dogs.

METHODS

A double-hemorrhage canine model was used. In a preliminary isometric tension study of canine vasospastic basilar arteries, the vasodilatory effects of milrinone were examined 7 days after an initial injection of blood. Milrinone was injected intracisternally (0.1 mg, 0.47 mmol/L) or intra-arterially (0.3 mg/kg, 1.2 mmol/L), and angiograms were performed 30, 60, 120, 180, 240, 300, and 360 minutes later on day 7.

RESULTS

Milrinone produced concentration-dependent vasodilation and was effective intracisternally, resulting in significant dilation until 180 minutes after injection and a tendency for dilation until 240 minutes. The effect of intra-arterial injection was not as significant compared with an intracisternal injection, resulting in significant dilation only at 180 minutes after intra-arterial injection.

CONCLUSION

Intracisternal injection of milrinone was more effective than intra-arterial injection for chronic cerebral vasospasm in dogs because intracisternal injection produced a higher concentration in vasospastic arteries (0.034-0.068 mmol/L intracisternally versus 0.016 mmol/L intra-arterially).

Effects of low-dose milrinone on weaning from cardiopulmonary bypass and after in patients with mitral stenosis and pulmonary hypertension

The phosphodiesterase inhibitor milrinone is usually preferred in patients with pulmonary hypertension and myocardial dysfunction after cardiopulmonary bypass. We investigated the effects of low-dose milrinone on pulmonary hypertension in the immediate pre- and postoperative period. Forty-seven patients were randomized to the control and milrinone groups. All patients had mean pulmonary artery pressure greater than 30 mmHg and pulmonary capillary wedge pressure greater than 20 mmHg and were candidates for mitral valve replacement for rheumatic mitral stenosis. Twenty-four patients received a loading dose of milrinone 25 microg/kg(-1) during weaning from cardiopulmonary bypass, followed by a maintenance dose of 0.25 microg/kg(-1)/min(-1) to the end of the surgery. Cardiac output and other hemodynamic variables were noted at induction, weaning from bypass, and postoperative 1 h. Pulmonary artery pressure, capillary wedge pressure, and central venous pressure were significantly lower in the milrinone group during weaning after cardiopulmonary bypass, while other variables were roughly similar. However, patients in the control group required higher doses of vasodilators, inotropes, and antiarrhythmic agents. Mean arterial pressure in the milrinone group was significantly lower at 1 h postoperatively than in the control group; however, the patients did not need many more vasopressors. Fluid restriction and diuretic agent use were more significant in the control group. Systemic arterial hypotension and vasopressor requirements with milrinone use at inotropic doses were not observed at the doses used for the study. A total of 21.7% of the patients in the control group required vasopressors in the perioperative period. Both groups demonstrated similar hematologic variables except that the hemoglobin level in the control group was significantly lower during postoperative days 1 and 7. Low-dose milrinone for a short-term during weaning from cardiopulmonary bypass may be used in patients with mitral stenosis and pulmonary hypertension for its effects on pulmonary artery pressures, less inotropic and vasopressor requirements, and fluid balance.

Effect of Combining Phosphodiesterase III Inhibitors With St Thomas Hospital’s Solution Used as Transplantation Preservative Solution in Isolated Rat Hearts

Improved preservation of the harvested heart with attenuation of the reperfusion injury is important for successful outcomes of cardiac transplantations. The most commonly used cardioplegic solution, to prevent ischemic changes has been St Thomas' Hospital cardioplegic solution (STHCS). However, it is neither ideal nor sufficient to prevent myocardial ischemia and reperfusion injury. Phosphodiesterase inhibitors can attenuate the damage due to the injuries of ischemia and reperfusion. In this study we sought to enrich STHCS with a phosphodiesterase inhibitor to improve preservation of cardiac functions. The harvested hearts of 24 rats were divided into four groups. All hearts were mounted on a Langendorff perfusion system. After a stabilization period, cardiac arrest was maintained by STHCS. The hearts were stored in STHCS alone or with milrinone, amrinone, or enoximone for 6 hours. The reperfusion was maintained using a modified Tyrode's solution. All hearts were compared for their preischemic and postischemic left ventricular developed pressure, +dp/dtmax, -dp/dtmax, duration of systole, ejection time, and time to reach peak systolic pressure. Coronary effluent was collected for lactate dehydrogenase (LDH) measurements. The initial values for all metrics were comparable between the groups. During the postreperfusion period, all hearts showed lower peak systolic pressures than the initial values. Although the amrinone group seemed to have higher values, the 25-minute result was at the border of significance and the 30-minute value, significantly higher. All hearts showed far lower results of maximum changes in contractility during the time period (+dp/dtmax) versus the initial values; comparisons between groups were not significant. For the parameter of maximum changes in relaxation during the time period (-dp/dtmax), while other hearts showed lower results, the amrinone group displayed values comparable to the initial ones after 20 minutes. Comparisons between groups were insignificant. While other hearts had comparable values for time of systole, the hearts applied with milrinone reached these values after 15 minutes. Group comparison for time of ejection revealed that the results at 5-minute postreperfusion were higher in the enoximone and the amrinone groups than the milrinone group. Postreperfusion 5-minute results were higher in the enoximone and the amrinone groups than the milrinone group for time to reach peak systolic pressure. LDH levels were lowest in the amrinone group. In conclusion, our study revealed that adding phosphodiesterase inhibitors to STHCS improved peak systolic pressure and maximum changes in relaxation during the time period (-dp/dtmax, mm Hg/s). It also decreased the LDH leakage, which corresponded to the degree of ischemic tissue damage. Amrinone seemed to result in more favorable results, which may be attributed to its additional effects on inflammation, including those on cytokines and leukocyte aggregation.

Levosimendan or Milrinone in the Type 2 Diabetic Patient With Low Ejection Fraction Undergoing Elective Coronary Artery Surgery

OBJECTIVES

The purpose of this study was to compare the hemodynamic profiles and the postoperative insulin requirements in 2 groups of type 2 diabetic patients with depressed myocardial function who underwent elective surgery for coronary artery disease and who received levosimendan or milrinone for postcardiopulmonary bypass low-output syndrome.

DESIGN

Randomized controlled trial.

SETTING

The Chest Diseases Hospital, Safat, Kuwait.

PARTICIPANTS

Type 2 diabetic patients undergoing elective surgery for coronary artery disease.

INTERVENTIONS

Fourteen patients and 16 patients received levosimendan and milrinone infusions, respectively, for treatment of the low-output syndrome.

MEASUREMENTS AND MAIN RESULTS

The hemodynamic, mixed venous oxygen saturation, oxygen extraction ratios, arterial lactate concentrations, and postoperative insulin infusion rates were serially documented for the first 48 hours after the diagnosis. The cardiac index and mixed venous oxygen saturation were significantly higher in the levosimendan group. The pulmonary capillary wedge pressure, systemic vascular resistance, and oxygen extraction ratios were significantly higher in the milrinone treatment group. The insulin requirements were similar for both of the treatment groups.

CONCLUSIONS

Levosimendan was more efficient than milrinone for treating the hemodynamic manifestations of the postcardiopulmonary bypass low-output syndrome. However, all the values in the milrinone treatment group were normalized. In this small population, both treatment groups had similar postoperative insulin requirements.

Effects of Olprinone on Myocardial Ischemia-Reperfusion Injury in Dogs

We investigated the effect of olprinone on canine myocardial pump function and myocardial damage after ischemia-reperfusion injury. Three dogs of the experimental group were given olprinone (Olprinone group) and another 3 dogs were served as control (Intact group). All animals were occluded left anterior descending artery for 60 min, followed by 6 hr of reperfusion. In the experiment, hemodynamics, infarct area, creatine kinase and troponin-I were measured. Olprinone infusion induced significantly high cardiac output value and significantly low values in left ventricular end diastolic pressure and systemic vascular resistance index after reperfusion. Also, olprinone tend to attenuate the infarct area, creatine kinase and troponin-I.

In-hospital mortality in patients with acute decompensated heart failure requiring intravenous vasoactive medications: an analysis from the Acute Decompensated Heart Failure National Registry (ADHERE)

OBJECTIVES

We sought to compare the in-hospital mortality of patients with acute decompensated heart failure (ADHF) who were receiving parenteral treatment with one of four intravenous vasoactive medications.

BACKGROUND

There are limited data regarding the effects of the choice of intravenous vasoactive medication on in-hospital mortality in patients hospitalized with ADHF.

METHODS

This was a retrospective analysis of observational patient data from the Acute Decompensated Heart Failure National Registry (ADHERE), a multicenter registry designed to prospectively collect data on each episode of hospitalization for ADHF and its clinical outcomes. Data from the first 65,180 patient episodes (October 2001 to July 2003) were included in this analysis. Cases in which patients received nitroglycerin, nesiritide, milrinone, or dobutamine were identified and reviewed (n = 15,230). Risk factor and propensity score-adjusted odds ratios (ORs) for in-hospital mortality were calculated.

RESULTS

Patients who received intravenous nitroglycerin or nesiritide had lower in-hospital mortality than those treated with dobutamine or milrinone. The risk factor and propensity score-adjusted ORs for nitroglycerin were 0.69 (95% confidence interval [CI] 0.53 to 0.89, p < or = 0.005) and 0.46 (94% CI 0.37 to 0.57, p < or = 0.005) compared with milrinone and dobutamine, respectively. The corresponding values for nesiritide compared with milrinone and dobutamine were 0.59 (95% CI 0.48 to 0.73, p < or = 0.005) and 0.47 (95% CI 0.39 to 0.56, p < or = 0.005), respectively. The adjusted OR for nesiritide compared with nitroglycerin was 0.94 (95% CI 0.77 to 1.16, p = 0.58).

CONCLUSIONS

Therapy with either a natriuretic peptide or vasodilator was associated with significantly lower in-hospital mortality than positive inotropic therapy in patients hospitalized with ADHF. The risk of in-hospital mortality was similar for nesiritide and nitroglycerin.

Enhanced Vasodilatory Responses to Milrinone in Catecholamine-Precontracted Small Pulmonary Arteries

Beta-adrenergic agonists (e.g., epinephrine [E] and norepinephrine [NE]) and phosphodiesterase-III inhibitors (e.g., milrinone) are often used in combination to augment ventricular function in the perioperative period. In the myocardium, milrinone acts synergistically with beta-adrenergic agonists to increase contractility. However, the potential interaction between catecholamines with combined alpha- and beta-adrenergic activity and milrinone in the pulmonary circulation has not been determined. We evaluated the vasodilatory effects of milrinone and nitroglycerine on large elastic and small muscular porcine pulmonary vascular rings precontracted with catecholamines with beta-adrenergic agonist activity (E and NE), the alpha-adrenergic agonist phenylephrine, and a nonadrenergic agonist, the thromboxane analog U46619. In small pulmonary arteries, the vasorelaxation with milrinone was significantly enhanced in rings precontracted with E or NE compared with those precontracted with phenylephrine or U46619. However, in large pulmonary arteries, the vasorelaxation with milrinone was similar in all vessel rings and was not influenced by the agonist used to induce precontraction. In marked contrast, the vasorelaxant responses to nitroglycerine were not altered by the specific agonist used for precontraction in either small or large pulmonary vascular rings. Thus, the pulmonary vascular effects of milrinone are enhanced when combined with drugs with beta-adrenoreceptor agonist activity. The vasodilatory interactions exhibited by phosphodiesterase-III inhibitors and the catecholamines NE and E suggest that their combined use might be beneficial in circumstances in which ventricular dysfunction and increased pulmonary vascular resistance occur.

IMPLICATIONS

This study demonstrated that milrinone had enhanced vasodilator effects when combined with drugs with beta-adrenoreceptor agonist activity in small pulmonary artery segments removed from pigs.

Mechanisms involved in the antiplatelet activity of 8-methyl-4-(1-piperazinyl)-7-(3-pyridinylmethoxy)-2H-1-benzopyran-2-one (RC414)

The effect on human platelets of 8-methyl-4-(1-piperazinyl)-7-(3-pyridinylmethoxy)-2H-1-benzopyran-2-one (RC414) was tested in vitro by measuring aggregation induced by several agonists, cAMP and cGMP levels, cAMP phosphodiesterase and PKC activities and [Ca2+]i. The RC414 effect on nitric oxide production was also evaluated. RC414 in a dose-dependent manner inhibited aggregation both in platelet rich plasma and in washed platelets. It was particularly effective in platelets challenged by collagen, ADP and thrombin: IC50 values are 0.51 +/- 0.12 microM, 0.98 +/- 0.36 microM and 1.00 +/- 0.15 microM, respectively. RC414 increased cAMP levels, through the specific inhibition of the cAMP high affinity phosphodiesterase (IC50 = 1.73 +/- 0.35 microM). RC414 reduced [Ca2+]i transients and PKC activation induced by thrombin. In addition RC414 was able to increase nitric oxide formation involving the stimulation of constitutive nitric oxide synthase enzyme. In conclusion, RC414 exerts its powerful anti-platelet activity by increasing cAMP intracellular levels and nitric oxide formation.

Haemodynamic effects of a milrinone infusion without a bolus in patients undergoing off-pump coronary artery bypass graft surgery

The haemodynamic effects of a continuous infusion of milrinone without an initial bolus dose were evaluated in patients undergoing off-pump coronary artery bypass graft surgery. After internal mammary artery harvest, milrinone 0.5 microg.min(-1).kg(-1) (29 patients) or a normal saline infusion (33 patients) was started and continued until all graft anastomoses were completed. Haemodynamic variables were recorded before application of the tissue stabiliser, at 1, 3, 5 and 10 min after the application of the stabiliser, and after its removal. The administration of a milrinone infusion was associated with a smaller decrease in cardiac output and mixed venous oxygen saturation during all the coronary artery anastomoses, with no severe complications and a decreased dose of norepinephrine infused to maintain systemic arterial pressure.

Postoperative management in patients with complex congenital heart disease

Life-threatening problems occur in the neonate and infant after cardiac surgery because of the interplay of diminished cardiac output (CO), increased metabolic demand, inflammatory responses to cardiopulmonary bypass, and maladaptive responses to stress. Therefore, the postoperative management of patients with complex congenital heart defects is directed at optimization of oxygen delivery to maintain end-organ function and promote wound healing. Traditionally, assessment of circulation in the postoperative congenital heart patient has depended on indirect assessment of CO using parameters such as blood pressure, pulses, capillary refill, and urine output. Because of the limitations of indirect and observer-dependent assessment of CO, we rely on objective measures of tissue oxygen levels for the complex postoperative patient. We have found that continuous monitoring of the mixed venous saturation (SvO2) allows for identification of acute changes in systemic oxygen delivery and frequently precedes other indicators of decreased CO. The postoperative patient can be expected to have a period of decreasing CO, and the need for intervention should be anticipated because critical low output syndrome will develop in a subset of patients. Strategies for postoperative care are developed based on the diagnosis and procedure, but optimizing SvO2 is a consistent goal. A uniform approach to airway maintenance, vascular access, and drug infusions, all universal concerns during the perioperative period, minimizes the potential for these predictable and necessary interventions to result in morbidity or mortality. Management of the postoperative single ventricle patient targets stabilization of the systemic vascular resistance through the use of vasodilators to improve systemic perfusion and simplify ventilator management. Management of any individual patient should be driven by objective analysis of available data and must include efforts to re-evaluate the treatment plan as well as to identify unanticipated problems.

Milrinone Reduces Cerebral Vasospasm After Subarachnoid Hemorrhage of WFNS Grade IV or V

The preventative effect of cisternal irrigation with milrinone against vasospasm was evaluated in 12 patients with subarachnoid hemorrhage (SAH) of World Federation of Neurosurgical Societies grade IV or V treated between September 1999 and September 2000. All aneurysms were clipped or embolized within 72 hours of the onset of SAH. Inlet and outlet tubes were placed in either the supratentorial cisternal space, lateral ventricle, or spinal subarachnoid space. Lactated Ringer solution containing urokinase (120 IU/ml), ascorbic acid (3.5 mg/ml), and milrinone (3.6 microg/ml) was continuously infused at 30 ml/hr for as long as 2 weeks. Angiographical vasospasm was detected in only two of the 11 patients who received milrinone irrigation and underwent postoperative angiography. Vasospasm may have resulted from irrigation obstruction associated with pneumocephalus in one patient and clot in the sylvian fissure in the other patient. The outcome of the milrinone irrigation therapy was significantly better than that of the conventional therapy. This study suggests that cisternal irrigation with milrinone is safe and effective, and reduces the occurrence of vasospasm in patients with poor grade aneurysmal SAH.

Effects of milrinone on hemodynamics and regional blood flow in the hypoxic dog

Milrinone, a therapeutic agent for acute congestive heart failure, has both inotropic and vasodilatory effects, but investigations of these effects of milrinone were almost all conducted under normoxia, and few reports have investigated how milrinone affects the hemodynamics and redistribution of regional blood flow under severe hypoxia. By using colored microspheres, we investigated how milrinone affects hemodynamics and the redistribution of regional blood flow under severe hypoxia. Twelve healthy mongrel dogs were divided into 2 groups. The milrinone group was infused with milrinone cumulatively at 25, 75 and 250 microg/kg for 5 min each. The intact group was infused with saline instead of milrinone. We measured the hemodynamics and cerebrum, cerebellum and kidney blood flow in both groups. Both groups were inspired with 10% oxygen. Milrinone induced significant decrease in mean pulmonary artery and pulmonary vascular resistance, compared with the intact group. In both groups slight decreases in mean arterial pressure, systemic vascular resistance and double-product were seen. In regional blood flow, milrinone-induced increases in blood flow were seen in the cerebrum, cerebellum, and especially in the kidneys. Milrinone's vasodilatory effects were sufficient even under hypoxia. And milrinone increased regional blood flow slightly in the cerebrum and cerebellum, and significantly in the kidneys. These results suggested that milrinone protects against hypoxia-induced organ damage especially in the kidneys. In addition, milrinone is very potent in improving severe congested hemodynamics which complicates hypoxic pulmonary vasoconstriction.

Effects of phosphodiesterase III inhibition on length-dependent regulation of myocardial function in coronary surgery patients

BACKGROUND

Phosphodiesterase III inhibitors increase myocardial contractility and decrease left ventricular (LV) afterload. We studied whether these effects altered LV response to an increase in cardiac load and affected length-dependent regulation of myocardial function.

METHODS

Before the start of cardiopulmonary bypass, a high-fidelity pressure catheter was positioned in the left ventricle and the left atrium in 10 coronary surgery patients. LV response to an increased cardiac load, caused by leg elevation, was assessed during baseline conditions and after administration of milrinone at a dose of 20 micrograms kg-1 over 15 min. Effects on contraction were measured by changes in maximal rate of pressure development (dP/dtmax). Effects on relaxation were assessed by analysis of changes in maximum rate of pressure decrease and by analysis of the load dependency of myocardial relaxation (R = slope of the relation between the time constant of isovolumic relaxation and end systolic pressure).

RESULTS

Milrinone increased dP/dtmax but measures of relaxation were unaltered. Leg elevation had more effect on measures of contraction and relaxation after milrinone than at baseline. The relationship between R and changes in dP/dtmax shifted downwards and to the right with milrinone, whereas the relationship between R and changes in end diastolic pressure (EDP) shifted downwards and to the left.

CONCLUSIONS

This suggests that milrinone improved contraction, reduced the load dependency of LV pressure decrease, and reduced the change in EDP after leg elevation.

Milrinone versus dobutamine in heart failure subjects treated chronically with carvedilol

OBJECTIVE

To compare the efficacy of milrinone and dobutamine in patients chronically treated with carvedilol.

BACKGROUND

Milrinone and dobutamine are used to manage decompensated heart failure, but their efficacy in patients on beta-blocker therapy was unknown.

METHODS

Twenty patients with decompensated heart failure were prospectively enrolled. Inotropic responses to milrinone (12.5, 25 or 50 microg/kg bolus infusions) or dobutamine (5, 10, 15 or 20 microg/kg/min infusions) were evaluated by right-heart catheterization.

RESULTS

Milrinone increased cardiac index (2.0-2.6 l/min/m2, P=0.0001) without significantly altering heart rate (70-75 bpm, P=0.19). Milrinone decreased mean pulmonary artery pressure (36-29 mm Hg, P=0.0001), pulmonary capillary wedge pressure (24-18 mm Hg, P=0.0001) and mean arterial blood pressure (78-75 mm Hg, P=0.0002). Left ventricular stroke volume index increased in the milrinone group (31-35 ml/beat/m2, P=0.0001). Dobutamine produced an increase in cardiac index (2.4-3.3 l/min/m2, P=0.0001) only at doses that are not typically used to treat heart failure (15-20 microg/kg/min). At these doses, dobutamine increased heart rate (68-82 bpm, P=0.008), mean systemic pressure (90-117 mm Hg, P=0.0001) and mean pulmonary artery pressure (21-30 mm Hg, P=0.001). Dobutamine did not alter left ventricular stroke volume index or pulmonary capillary wedge pressure.

CONCLUSIONS

Dobutamine and milrinone have different hemodynamic effects in patients treated chronically with carvedilol. These differences should be considered when selecting inotropic therapy for decompensated heart failure.

Milrinone for the treatment of cerebral vasospasm after subarachnoid hemorrhage: report of seven cases

OBJECTIVE

The intra-arterial infusion of papaverine has been used for dilation of spastic cerebral vessels after aneurysmal subarachnoid hemorrhage, although its efficacy is controversial. Milrinone is an inotropic drug that dilates vessels by phosphodiesterase inhibition in a mechanism similar to that of papaverine. We examined the effects of intra-arterial and subsequent intravenous administration of milrinone on patients with symptomatic cerebral vasospasm.

METHODS

Seven patients with cerebral vasospasm were enrolled in this study. Milrinone was delivered intra-arterially via catheter at a rate of 0.25 mg/min. The total delivered dose was between 2.5 and 15 mg. Radiological measurement of the middle cerebral artery diameter and cerebral blood flow was carried out before and after arterial infusion. Intravenous treatment followed at 0.50 or 0.75 microg/kg/min for up to 2 weeks from the onset of subarachnoid hemorrhage.

RESULTS

Dilation of the vasospastic vessels occurred in all patients. The rate of cerebral blood flow was calculated in six patients and was increased in all. Subsequent intravenous infusion was effective in preventing a recurrence of symptomatic vasospasm in four of the seven patients.

CONCLUSION

It is suggested that milrinone was effective and safe for the treatment of cerebral vasospasm after subarachnoid hemorrhage in the patients in this series. Intra-arterial infusion with adjunctive intravenous infusion holds promise as a clinically advantageous treatment regimen.

Amrinone in pediatric refractory septic shock: An open-label pharmacodynamic study

OBJECTIVE: To investigate the short-term hemodynamic effects of amrinone in pediatric patients with refractory septic shock. DESIGN: Open-label, clinical trial. SETTING: Pediatric intensive care unit. PATIENTS: Nine patients admitted with a diagnosis of septic shock receiving stable doses of vasopressors and inotropes. INTERVENTIONS: Pediatric patients with septic shock and a pulmonary artery catheter were treated with amrinone in a stepwise fashion at 5, 10, and 15 &mgr;g/kg/min. MEASUREMENTS AND MAIN RESULTS: Heart rate, blood pressure, cardiac index, rate pressure product, systemic vascular resistance index, pulmonary vascular resistance, oxygen delivery, and oxygen consumption were measured at baseline and 90 mins after each amrinone dose. The addition of amrinone increased cardiac index (p <.05) and oxygen delivery (p <.05) without increasing the rate pressure product. Decreases were observed in systemic vascular resistance index (p <.05) and pulmonary vascular resistance (p <.05). No significant changes were seen in heart rate, blood pressure, or oxygen consumption. CONCLUSIONS: In this short-term, dose-response study in children with refractory septic shock, amrinone improved cardiac index and oxygen delivery in pediatric patients with refractory septic shock without increasing myocardial work.

Pharmacology of inotropic agents in infants and children

Inotropic agents are drugs which increase the stroke work of the heart at a given pre-load and after-load. All of these agents work through a final common pathway involving the modulation of calcium interactions with various myocardial contractile proteins. The agents employed with pediatric patients include the cardial glycosides, catecholamine beta-agonists and the selective phosphodiesterase III inhibitors. Digoxin is the prototypic cardiac glycoside which has a long history of safe and effective use in infants and children. Its utility in improving right ventricular dysfunction in patients with cor pulmonale leading to biventricular dysfunction makes it ideally suited to the pediatric population. Monitoring digoxin pharmacokinetics in infants is confounded by the presence of an endogenous digoxin-like substance. Nevertheless, the drug is well suited for subacute and chronic myocardial support. In contrast, the catecholamines are the drugs of choice for acute intervention. Their pharmacokinetics permit rapid dosing titration. In infants and children the greatest experience has been accrued with dopamine, a mixed alpha- and beta-agonist but both epinephreine and norepinephrine are being used with increasing frequency as the need for drugs with increased potency and pressor activity becomes more common. The phosphodiesterase inhibitors amrinone and milrinone are the newest additions to our therapeutic armamentarium. In addition to their modest inotropic effects, amrinone and to a greater extent, milrinone offer significant pulmonary vasodilatation as part of their therapeutic package. These effects occur with little or any impact on myocardial oxygen consumpton while their lusitropic effects enhance relaxation in hypertrophied ventricular muscle. Of the two agents milrinone is probably preferred due to its greater therapeutic index and shorter elimination half-life. All of these agents remain important tools in the care of critically ill infants and children. The rational use of these drugs based upon their pharmacokinetic and pharmacodynamic properties is essential to achieve their optimal effects.

Hemodynamic effects of milrinone during weaning from cardiopulmonary bypass: comparison of patients with a low and high prebypass cardiac index

OBJECTIVE

To compare the hemodynamic effects of milrinone during weaning from cardiopulmonary bypass (CPB) in patients with a low pre-CPB cardiac index (CI) <2.5 L/min/m2) and in patients with a high pre-CPB CI (> or =2.5 L/min/m2).

DESIGN

Prospective, randomized, double-blind study.

SETTING

University hospital.

PARTICIPANTS

Forty-eight patients scheduled for elective coronary artery bypass graft surgery.

INTERVENTION

Patients were divided into 4 groups: (1) low pre-CPB CI/placebo, (2) low pre-CPB CI/milrinone, (3) high pre-CPB CI/placebo, and (4) high pre-CPB CI/milrinone. Patients received a loading dose of 20 microg/kg of milrinone followed by an infusion of 0.2 microg/kg/min or placebo 15 minutes before the anticipated weaning time.

MEASUREMENTS AND MAIN RESULTS

In the low pre-CPB CI/ placebo group, low CIs and high systemic vascular resistances (SVRs) were observed after CPB. High doses of dopamine and dobutamine were needed, and infusion of epinephrine was used in 5 of the 12 patients for hemodynamic support. Milrinone improved CI and reduced SVR in the low pre-CPB CI/milrinone group. Norepinephrine was needed to maintain an adequate systemic blood pressure in 6 of the 12 patients, however. In the high pre-CPB CI/placebo group, satisfactory CIs and SVRs were observed during weaning from CPB with low doses of dopamine and dobutamine. Milrinone significantly increased CI and decreased SVR in the high pre-CPB CI/milrinone group: 10 of the 12 patients had CIs above the upper limit of normal, and 7 patients had SVRs below the lower limit of normal.

CONCLUSION

Milrinone was effective during weaning from CPB in patients with a low pre-CPB CI. Milrinone in combination with norepinephrine was a good alternative to epinephrine for the treatment of myocardial dysfunction after CPB.

Milrinone improves arterial oxygenation in dogs with acute lung injury induced by oleic acid

The aim of the study was to investigate effects of milrinone on pulmonary permeability in dogs with acute lung injury induced by oleic acid. To induce acute lung injury, we administered 0.08 mg/kg of oleic acid to 19 adult mongrel dogs and then measured hemodynamic parameters and performed blood gas analysis. An injection of oleic acid depressed the mean arterial pressure, cardiac index, and arterial oxygenation. Dogs were divided into three groups: six received a bolus of milrinone (50 microg/kg) followed by a continuous (0.5 microg/kg/min, low-dose), seven received a bolus (100 microg/kg) followed by a continuous (1.0 microg/kg/min; i.e., a low-dose twice; high-dose), and six no milrinone (control). Milrinone administration improved the cardiac index and arterial oxygenation and simultaneously depressed the intrapulmonary shunt fraction and the extravascular thermal lung water as extravascular water content of the lung. These changes produced by milrinone are different according to the doses. In conclusion, milrinone acts on the capillary endothelium and inhibits an accumulation in the extravascular water content of the lung, which may induce an improvement in arterial oxygenation. Milrinone may also improve arterial oxygenation through an inhibition of platelet aggregation and chemical mediators that are released from platelets. The latter mechanism also may improve arterial oxygenation, and the exact property responsible for causing the effect of milrinone has not yet been identified.

Tolerability of extended duration intravenous milrinone in patients hospitalized for advanced heart failure and the usefulness of uptitration of oral angiotensin-converting enzyme inhibitors

Milrinone is a phosphodiesterase inhibitor that has been shown to improve hemodynamic parameters in patients with class III to IV heart failure when administered intravenously for < or =48 hours. This study examines the tolerability of long-term intravenous milrinone therapy and assesses its utility in allowing upward titration of oral vasodilator agents. A retrospective review of hospital records identified 63 patients who underwent hemodynamic monitoring and received intravenous milrinone for >24 hours in a critical care setting. Hemodynamics and medications were recorded before and after 24 hours of milrinone therapy. Additional medications, as well as any adverse events, were recorded throughout milrinone therapy. The mean dose of milrinone was 0.43 +/- 0.10 microg/kg/min, with a mean duration of 12 +/- 15 days (range 1 to 70). Therapy was continued for >48 hours in 89% of patients. After 24 hours of milrinone therapy, patients exhibited significant improvements in pulmonary artery pressures, pulmonary capillary wedge pressures, and cardiac index. When compared with baseline, significantly more patients received angiotensin-converting enzyme (ACE) inhibitors after 24 hours of milrinone and at the end of milrinone therapy (67% vs 86%, p <0.01). Likewise, significantly more patients also received oral hydralazine and/or nitrates at the end of milrinone therapy (38% vs 65%, p <0.01) when compared with baseline. The mean doses of most oral medications at the 3 time periods were similar. The ACE inhibitor dose was significantly higher at the end of milrinone therapy when compared with baseline, and hydralazine dose was significantly higher at the end of therapy when compared with 24 hours. Few adverse effects were noted, with only 10% of patients experiencing symptomatic ventricular tachycardia and 2 patients with significant hypotension requiring discontinuation of the drug. The adverse events were similar in the group of patients who received milrinone for > or =7 days compared with the entire cohort. Milrinone was well tolerated over the long term in a controlled inpatient setting, and allowed uptitration of oral vasodilator therapy.

Pharmacological strategies for improving diastolic dysfunction in the setting of chronic pulmonary hypertension

BACKGROUND

Right ventricular (RV) hypertrophy is an adaptive process that occurs in the setting of chronic pulmonary hypertension (CPH) and can lead to alterations in normal RV diastolic properties. This study was designed to investigate the effects of NO and milrinone on RV diastolic dysfunction in the setting of CPH and RV hypertrophy by use of a canine model of monocrotaline pyrrole (MCTP)-induced CPH.

METHODS AND RESULTS

Sixteen mongrel dogs (22 to 24 kg) were used. Animals underwent percutaneous pulmonary artery (PA) catheterization to measure pulmonary hemodynamics before and 8 weeks after injection of 3 mg/kg MCTP (n=8) or placebo (control, n=8). Eight weeks after injection, all hearts were instrumented with a PA flow probe, sonomicrometric dimension transducers, and micromanometers. Data were collected at baseline and after both NO and milrinone administration. Diastolic properties were quantified by use of the end-diastolic pressure-volume relationship and the time constant of ventricular isovolumic relaxation. Eight weeks after injection, significant increases in the PA pressure and pulmonary vascular resistance were observed in MCTP dogs. Significant worsening of RV diastolic function occurred in association with significant increases in the ratio of RV dry weight to LV+septal dry weight. NO and milrinone administration both led to significant improvements in RV diastolic properties.

CONCLUSIONS

In the setting of MCTP-induced CPH, significant worsening of RV diastolic function was observed in association with significant increases in the ratio of RV dry weight to LV+septal dry weight, suggesting that these changes are partially due to RV hypertrophy. The significant improvement in RV diastolic properties after both NO and milrinone administration suggests that these agents may be effective forms of pharmacological therapy for improving RV diastolic dysfunction in the setting of CPH.

Protein synthesis-dependent potentiation by thyroxine of antiviral activity of interferon-gamma

We have studied the prenuclear signal transduction pathway by which thyroid hormone potentiates the antiviral activity of human interferon-gamma (IFN-gamma) in HeLa cells, which are deficient in thyroid hormone receptor (TR). The action of thyroid hormone was compared with that of milrinone, which has structural homologies with thyroid hormone. L-Thyroxine (T4), 3,5,3'-L-triiodothyronine (T3), and milrinone enhanced the antiviral activity of IFN-gamma up to 100-fold, a potentiation blocked by cycloheximide. The 5'-deiodinase inhibitor 6-n-propyl-2-thiouracil did not block the T4 effect. 3,3',5,5'-Tetraiodothyroacetic acid prevented the effect of T4 but not of milrinone. The effects of T4 and milrinone were blocked by inhibitors of protein kinases C (PKC) and A (PKA) and restored by PKC and PKA agonists; only the effect of T4 was blocked by genistein, a tyrosine kinase inhibitor. In separate models, milrinone was shown not to interact with nuclear TR-beta. T4 potentiation of the antiviral activity of IFN-gamma requires PKC, PKA, and tyrosine kinase activities but not traditional TR.

Involvement of cyclic GMP in the mode of action of a new antithrombotic agent PCA-4230; inhibition of the platelet cyclic GMP dependent phosphodiesterase

The effect of PCA-4230, a new dihydropyridine derivative with a potent antithrombotic activity, on cyclic nucleotide phosphodiesterase in platelets was studied. PCA-4230 inhibited (54%) cyclic GMP hydrolytic activity of a platelet cytosolic fraction, whereas it did not affect that of cyclic AMP. Results suggested that PCA-4230 inhibited a cyclic GMP-dependent phosphodiesterase, known as cGB PDE or type V, on a purified enzyme from rabbit platelets by a non-competitive-uncompetitive type inhibition. In addition, PCA-4230 potentiated the increase in both cyclic GMP and cyclic AMP levels evoked by sodium nitroprusside. Furthermore, PCA-4230 and forskolin caused a synergistic effect in cyclic AMP, and also potentiated the phosphorylation of 50 kDa and 22 kDa proteins, reported as substrates of cyclic GMP- and cyclic AMP-dependent protein kinases that are related to the inhibition of platelet functions. Finally, PCA-4230 also potentiated the forskolin- and sodium nitroprusside-inhibited serotonin release evoked by thrombin, probably related to the increased cyclic nucleotide level.

Milrinone improves pulmonary hemodynamics and right ventricular function in chronic pulmonary hypertension

BACKGROUND

Right ventricular failure after cardiac transplantation is commonly related to preexisting recipient pulmonary hypertension. This study was designed to investigate the effects of intravenous milrinone on pulmonary hemodynamic indices and right ventricular function in a canine model of monocrotaline pyrrole-induced chronic pulmonary hypertension.

METHODS

Eight mongrel dogs underwent pulmonary artery catheterization to measure right-sided hemodynamic indices before and 6 weeks after a right atrial injection of monocrotaline pyrrole. Six weeks after injection, all hearts were instrumented with a pulmonary artery flow probe, ultrasonic dimension transducers, and micromanometers. Data were collected at baseline and after milrinone infusion.

RESULTS

Six weeks after monocrotaline pyrrole injection, significant increases in the pulmonary artery pressure and pulmonary vascular resistance were observed. Milrinone led to significant increases in right ventricular function as well as significant improvements in pulmonary vascular resistance, pulmonary blood flow, and left ventricular filling.

CONCLUSIONS

This investigation demonstrates the well-known hemodynamic and inotropic effects of milrinone which, in the setting of monocrotaline pyrrole-induced pulmonary hypertension, were also associated with significant increases in pulmonary blood flow and left ventricular filling.

Prevention of chronic cerebral vasospasm in dogs with milrinone

OBJECTIVE

Delayed cerebral ischemia resulting from vasospasm is a major cause of morbidity and death in patients with aneurysmal subarachnoid hemorrhage. Milrinone, because it inhibits Type IV cyclic adenosine monophosphate-specific phosphodiesterase enzyme in both cardiac and vascular smooth muscle, is a powerful inotrope and vasodilator, but it has little effect on heart rate or blood pressure. Because of these properties, milrinone is an attractive potential therapy after subarachnoid hemorrhage. The purpose of the present study was to investigate the effect of milrinone on chronic experimental cerebral vasospasm.

METHODS

A double-hemorrhage canine model of vasospasm was used to study the efficacy of milrinone. Angiographic vasospasm and systemic hemodynamics were compared in a treatment group of animals that received a loading dose of milrinone (0.05 mg/kg, intravenously) and then slow-release (0.05 microgram/kg/min) milrinone pellets (n = 10) and a control group that received placebo pellets (n = 9), over an 8-day period after the initial subarachnoid hemorrhage. The hemorrhage was created by injection of 4 ml of autologous, nonheparinized, arterial blood into the cisterna magna on Days 1 and 3. Hemodynamic measurements, including cardiac output determinations, were made on Days 0, 1, 3, 6, and 8 with a pulmonary artery catheter, and angiographic vasospasm was assessed on Day 8 by comparison with baseline angiograms.

RESULTS

Treatment with milrinone caused no significant changes in systemic hemodynamics. Angiographic vasospasm, however, was significantly reduced in the Day 8 angiograms for the treated group, compared with the control group (98.28 +/- 14.06 and 67.89 +/- 13.06% of original vessel cross-sectional area, respectively; P < 0.001).

CONCLUSION

Milrinone is effective in preventing chronic cerebral vasospasm in a canine model of experimental chronic cerebral vasospasm. This effect is independent of changes in systemic hemodynamics. Milrinone and related drugs warrant further investigation for the treatment of cerebral vasospasm.

Hemodynamic effects of i.v. milrinone lactate in pediatric patients with septic shock. A prospective, double-blinded, randomized, placebo-controlled, interventional study

STUDY OBJECTIVE

To determine the hemodynamic effects of i.v. milrinone lactate in pediatric patients with nonhyperdynamic septic shock. Specifically we tested the hypothesis that i.v. milrinone would increase cardiac index by 20% and decrease systemic vascular resistance index by 20% during a 2-h study period.

DESIGN

Prospective, double-blinded, randomized, placebo-controlled, descriptive, interventional study.

SETTING

Twenty-six-bed pediatric ICU at Children's Medical Center of Dallas and a 10-bed pediatric trauma ICU at Parkland Memorial Hospital.

PATIENTS/PARTICIPANTS

Twelve patients (age range, 9 months to 15 years) with nonhyperdynamic septic shock despite administration of catecholamines (cardiac index [CI] normal [3.5 to 5.5 L/min/m2] or low [< or =3.5 L/min/m2]; systemic vascular resistance index [SVRI] normal [800 to 1,600 dyne.s.cm5/m2] or high [> or =1,600 dyne.s.cm5/m2]; and pulmonary capillary wedge pressure [PCWP] normal [8 to 12 mm Hg] or higher) with clinical signs of poor perfusion were enrolled, randomized, and treated in a blinded fashion with i.v. milrinone and placebo.

INTERVENTIONS

Patients were randomized into two groups. Group A received a loading dose of 50 micrograms/kg i.v. of milrinone followed by a continuous i.v. infusion of 0.5 microgram/kg/min while group B received an equal volume loading dose and continuous infusion of placebo. After 2 h, group A received an equal-volume loading dose followed by a continuous infusion of placebo while the milrinone infusion continued, while group B received a 50 micrograms/kg loading dose of milrinone followed by a continuous infusion of 0.5 microgram/kg/min while the placebo infusion remained. Outcome variable were measured at baseline, 0.5, 1.0, 2.0, 2.5, 3.0, and 4.0 h. Echocardiographic measurements were taken at baseline, hour 2, and hour 4 in all subjects. No changes in other inotropic or mechanical ventilatory support were allowed during the study period.

MEASUREMENTS AND MAIN RESULTS

Milrinone significantly increased CI, stroke volume index (SVI), right and left ventricular stroke work index, and oxygen delivery (Do2) at 0.5, 1.0, and 2.0 h postloading dose (p < 0.05) while significantly decreasing SVRI, pulmonary vascular resistance index, and mean pulmonary arterial pressure at 0.5, 1.0, and 2.0 h postloading dose (p < 0.05). No clinically or statistically significant changes in heart rate, systolic and diastolic BP, mean systemic arterial pressure, or PCWP were observed during milrinone treatment compared to placebo.

CONCLUSIONS

CI, SVI, and Do2 significantly increased while SVRI significantly decreased when compared to placebo after i.v. administration of milrinone to pediatric patients with nonhyperdynamic septic shock. No adverse effects were observed. In a volume-resuscitated pediatric patient with septic shock, when administered in addition to catecholamines, milrinone will improve cardiovascular function.

Comparison of two different loading doses of milrinone for weaning from cardiopulmonary bypass

OBJECTIVE

To compare the hemodynamic effects, pharmacokinetic profiles, and the need for vasoactive agents between a low (20 micrograms/kg during 15 minutes [group 1; n = 10]) and a high (40 micrograms/kg during 15 minutes [group 2; n = 10]) loading dose of milrinone.

DESIGN

Prospective, randomized, double-blind.

SETTING

University hospital.

PARTICIPANTS

Twenty patients scheduled for elective coronary artery surgery.

INTERVENTIONS

Weaning from CPB was achieved using a strict protocol. After atrioventricular pacing at 90 beats per minute and preload optimalization, a first weaning attempt was started with only calcium and nitroglycerin as support. If this attempt was unsuccessful (cardiac index < 2L/min/m2), CPB was reinitiated and weaning level 2 was prepared, consisting of inotropic support with milrinone. Patients received either the low (group 1) or the high (group 2) loading dose of milrinone. After the end of the loading dose, a continuous infusion of milrinone of 0.5 micrograms/kg/min was started in both groups.

MEASUREMENTS AND MAIN RESULTS

Both groups were comparable regarding preoperative and intraoperative data. Hemodynamic data were comparable in both groups at each time of measurement (p = 0.941). The need for vasoactive medication (norepinephrine [NE]) in order to keep mean arterial pressure > or = 50 mm Hg was significantly higher in group 2 (p = 0.004). Need for NE during the loading infusion was 9.6 +/- 4.9 micrograms (mean +/- SEM) in group 1 and 41.6 +/- 7.6 micrograms in group 2 (p = 0.004). Need for NE during the immediate post-CPB period was also higher in group 2 (16.0 +/- 10.4 micrograms in group 1 and 232.5 +/- 82.8 micrograms in group 2 (p = 0.002)). Plasma clearance of milrinone after CPB was less in both groups than in healthy volunteers. However, clearance of milrinone was significantly higher in group 2 (p = 0.006), and consequently, half-life of milrinone was significantly less in group 2 (p = 0.007).

CONCLUSIONS

The present results demonstrate that when milrinone is used during weaning from CPB, a loading dose of 20 micrograms/kg provided to similar hemodynamic support a loading dose of 40 micrograms/kg. The need for vasoconstrictive medication was significantly less in the group with the low loading dose.

Ischemia-dependent efficacy of phosphodiesterase inhibition

To evaluate the inotropic efficacy of phosphodiesterase inhibition in hearts with and without ischemic injury, 27 sheep were evaluated sonomicrometrically during incremental volume loading on right heart bypass. Contractility was assessed with the preload recruitable stroke work relationship. Active relaxation rate was estimated using the time constant of isovolumic pressure decay (tau). For nonischemic assessment, groups 1 and 2 (n = 6 each) underwent 45 minutes of vented perfusion after which milrinone was administered to group 1; group 2 served as nonischemic controls. There was no detectable increase in preload recruitable stroke work or decrement in tau after milrinone administration. Groups 3 and 4 underwent 15 minutes of 37 degrees C ischemia (aortic cross-clamping) followed by 30 minutes of vented reperfusion. Milrinone was then administered to group 3 (n = 7); group 4 (n = 8) served as ischemically injured controls. Inotropic and lusitropic effects were present (group 3 preload recruitable stroke work: 35.4 +/- 5.8 mJ.beat-1.100 g-1.mL-1 before milrinone to 49.5 +/- 4.4 mJ.beat-1.100 g-1.mL-1 after milrinone [p < 0.05]; group 3 tau: 51.8 +/- 5.5 ms before milrinone to 32.2 +/- 2.5 ms after milrinone [p < 0.02]). Although milrinone restored contractility and increased the rate of active relaxation in the postischemic hearts, there was no detectable inotropic effect in nonischemic hearts. In this model, milrinone augments contractility and relaxation in postischemic myocardium but offers little inotropic benefit in non-ischemically injured hearts.

The use of intravenous milrinone in chronic symptomatic ischemic heart disease

To evaluate the antiischemic effects of intravenous milrinone, 20 patients with angiographically proved coronary artery disease and stable angina were studied at rest and during exercise under control conditions and after an intravenous loading injection of milrinone (50 micrograms/kg/10 min) followed by an infusion with 0.5 micrograms/kg/min. Hemodynamic parameters, epinephrine, norepinephrine, and atrial natriuretic factor were assessed. Control ergometry revealed ischemia; however, during exercise with intravenous milrinone, ischemia was eliminated. Because of unloading effects, there was also a significant decrease in ST segment depression (p less than 0.001). Heart rate increased significantly (p less than 0.001) at rest but increased significantly less after exercise testing (p less than 0.001). The changes in mean arterial pressure, cardiac output, and myocardial oxygen consumption during exercise were not significantly different between the milrinone and control phase. Intravenous milrinone delayed the onset of angina (p less than 0.001) and significantly shortened the duration of anginal attacks (p less than 0.05); exercise duration in the milrinone phase was longer than in the control phase (p = 0.051). Because of vasodilatation, a mild secondary increase in norepinephrine was observed during the milrinone phase, and there was a significantly smaller increase in atrial natriuretic factor during exercise while receiving milrinone as a result of preload reduction (p less than 0.05). Intravenous milrinone produced beneficial hemodynamic and antiischemic effects in patients with coronary artery disease, stable angina, and reproducible ST segment depression probably by enhancing myocardial contractility and reducing preload and afterload.