Role of reflex sympathetic withdrawal in the hemodynamic response to an increased inotropic state in patients with severe heart failure

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.

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.

The role of phosphodiesterase inhibitors in heart failure

Myocardial contractility is dependent on available intracellular calcium and this can be enhanced by increasing intracellular cyclic adenosine monophosphate. One way of achieving this is by inhibiting the phosphodiesterase III enzyme. Over the last 15 years, a number of new drugs with this mechanism of action have been studied in man and have been found not only to have a positive inotropic action on the heart but also a vasodilating action on peripheral blood vessels. This combination of effects produces favourable haemodynamic improvement in patients with chronic heart failure. While some smaller studies showed that this did translate into an improvement in symptoms and functional capacity, a large well-designed and controlled clinical trial showed that survival was decreased when milrinone was used in target daily doses of 40 mg. For this reason, chronic long-term oral therapy with phosphodiesterase III inhibitors is not currently being actively pursued. They may still have a role as acute short-term therapy in severely ill patients who do not respond adequately to optimal standard drug therapy. Milrinone has been one of the most widely studied drugs in this regard. Even during short-term administration, its use should be closely monitored for any evidence of an increase in ventricular arrhythmias or decrease in ventricular function.

Acute effects of intravenous phosphodiesterase inhibition in chronic heart failure: simultaneous pre- and afterload reduction with a single agent

Intravenous phosphodiesterase inhibition with milrinone is known to have a beneficial effect on haemodynamics in chronic heart failure. Its effect on lower limb capacitance vessels has not been previously investigated. We have studied the effect of intravenous milrinone in 10 patients with severe chronic heart failure. Thirty minutes after commencement of treatment mean cardiac index had risen by 26% and pulmonary artery wedge pressure, systemic vascular resistance and right atrial pressure had fallen by 51, 24 and 89%, respectively (p less than 0.05 for all changes). These changes were maintained for the 2 h observation period with no evidence of tolerance and were accompanied by a 17% increase in venous volume (p less than 0.01) and a 42% increase in ejection fraction (p less than 0.001) at 30 min; at 120 min the improvement in ejection fraction had been maintained and a further increase in venous volume to 38% above baseline was evident. The increase in venous volume was strongly correlated with the decrease in mean pulmonary artery wedge pressure and mean right atrial pressure at 30 min and 2 h (r = -0.80 and -0.69 for mean pulmonary artery wedge pressure, r = -0.88 and -0.56 for mean right atrial pressure). Milrinone therefore has clinically important venodilating properties, in addition to its known effects as an arterial vasodilator and a positive inotrope.

Sympathoinhibitory responses to digitalis glycosides in heart failure patients. Direct evidence from sympathetic neural recordings

Digitalis glycosides exert both excitatory and inhibitory autonomic actions in animals and produce vasoconstriction in normal humans but produce vasodilation in heart failure patients. To determine whether or not these contrasting vascular responses are due to differing autonomic actions of the drug, we compared the responses to intravenous administration of Cedilanid-D (0.02 mg/kg) in eight normal subjects (mean age, 23 +/- 1 years) and eight patients with moderate-to-severe heart failure (mean age, 52 +/- 5 years, NYHA Class III-IV). Hemodynamics and efferent sympathetic nerve activity to muscle (MSNA) were measured during 5-minute periods before (control) and 20 minutes after drug administration. In the heart failure patients, Cedilanid-D significantly increased systolic and pulse pressures, whereas mean arterial pressure was unchanged. There was a decrease in right atrial pressure and a tendency for a decrease in pulmonary artery diastolic pressure with a slowing of heart rate. Cardiac index increased by 24 +/- 7%. Short-term administration of digitalis in these heart failure patients produced a fall in forearm vascular resistance (from 37.6 +/- 8.2 to 31.8 +/- 8.1 units, p less than 0.05) and an early, profound, and sustained decrease in MSNA (from 831.0 +/- 118.4 to 474.4 +/- 103.6 units/100 heart beats, p less than 0.01). Digitalis glycosides produced different vascular and MSNA responses in the normal subjects. In the normal volunteers, the drug significantly increased systolic, mean, and pulse pressures and decreased central venous pressure and heart rate. Despite the significant increase in arterial pressure, there was no change in forearm vascular resistance (from 11.7 +/- 1.0 to 12.7 +/- 1.0 units, p = NS) or MSNA (from 494.8 +/- 88.5 to 369.1 +/- 60.5 units/100 heart beats, p = NS), suggesting a sympathoexcitatory response in normal subjects. To determine whether or not the digitalis-induced sympathoinhibition in the heart failure patients was simply due to an inotropic effect (stimulation of inhibitory cardiac mechanoreceptors), we studied the responses of seven additional patients with heart failure before and during administration of dobutamine (3.4 +/- 0.4 micrograms/kg/min). Dobutamine produced a 34 +/- 3% increase in cardiac index, no significant change in systemic arterial pressures, a decrease in pulmonary artery diastolic and right atrial pressures, and no change in heart rate or forearm vascular resistance (from 30.2 +/- 4.3 to 26.5 +/- 4.7 units, p = NS).(ABSTRACT TRUNCATED AT 400 WORDS)

Observations on the intracoronary administration of milrinone and dobutamine to patients with congestive heart failure

A direct intracoronary infusion technique was used to characterize the mechanisms of action of milrinone, a new phosphodiesterase inhibitor. Because of the small quantity of drug infused, it is possible to achieve a therapeutic concentration of drug in the heart with little or no systemic accumulation. Because loading conditions are largely unaffected during intracoronary drug infusion, it is possible to use left ventricular +dP/dt as a convenient measure of changes in contractility. Intracoronary milrinone infusion caused a dose-related increase in +dP/dt associated with a substantial improvement in left ventricular pump function. In addition, there is a small decrease in heart rate, which appeared to be secondary to reflex withdrawal of sympathetic tone, since it was associated with a decrease in plasma norepinephrine. Measurement of forearm vascular resistance and forearm venous capacitance by plethysmography indicated that although there was no significant decrease in forearm vascular resistance during intracoronary drug infusion, there was a small increase in venous capacitance. Subsequent intravenous administration of milrinone caused a substantial further improvement in left ventricular pump function, associated with a substantial decrease in left- and right-sided cardiac filling pressures and forearm vascular resistance, and an increase in forearm venous capacitance. These findings suggest that reflex sympathetic withdrawal may contribute to the venous dilation that occurs with milrinone, but that the major effects of milrinone on vascular tone are due to a direct vascular action of the drug. Intracoronary infusion of dobutamine has also demonstrated a substantial decrease in the inotropic response to beta-adrenergic stimulation in patients with congestive heart failure, presumably because of down-regulation of beta-adrenergic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)