[Hemodynamic effects of intravenous clonidine in patients with acute myocardial infarction]

Abstract

To assess the hemodynamic effects of Clonidine in hypertensive patients (pts) with an acute myocardial infarction (AMI), we administered the drug to 12 such patients either in a single bolus (75--150 micrograms in 5 min - 8 pts) or by continuous infusion (0.4--5 micrograms/min - 4 pts). Hemodynamic measurements were obtained by means of a Swan-Ganz thermodilution catheter, before and 60 min after the administration of the drug. Clonidine did not significantly affected Heart Rate (from 80.5 +/- 3.9 to 78.4 +/- 5.9 beats/min), Mean Pulmonary Arterial Pressure (from 18.6 +/- 1.7 to 15.1 +/- 1 mmHg), Mean Pulmonary Wedge Pressure (from 12.5 +/- 1.1 to 10.6 +/- 0.7 mmHg), central Venous Pressure (from 4 +/- 0.8 to 3 +/- 0.9 mmHg), Cardiac Index (from 2.6 +/- 0.07 to 2.6 +/- 0.7 L/min/m2), Stroke Volume (from 65.2 +/- 2.8 to 68.5 +/- 5.5 ml/b). Conversely Mean Arterial Pressure fell significantly from 127 +/- 3.1 to 96.2 +/- 7.2 mmHg (P less than 0.001). Left Ventricular Systolic Work Index was reduced from 62.3 +/- 3.3 to 50.4 +/- 4.4 gm/beats/m2 (P less than 0.025), Total Systemic Resistances from 1888 +/- 50 to 1412 +/- 117 dyne sec cm-5 (P less than 0.005) and Tension Time Index from 3536 +/- 495 to 2389 +/- 385 x 10(3) mmHg x sec/min (p less than 0.05). Clonidine is a safe and useful drug to obtain a fall of high blood pressure often complicating AMI, without depressing left ventricular performance, as suggested by no significant changes of CI, WP and LVSWI. The reduction of TTI suggests a beneficial effect on the balance between myocardial oxygen delivery and demand. Clonidine is a hypotensive drug which can be safely used in patients with AMI, without depressing the left ventricular performance.