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.


METHODS
Prospective, randomized, double-blind.


METHODS
University hospital.


METHODS
Twenty patients scheduled for elective coronary artery surgery.


METHODS
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.


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.
De Hert
S G
SG
Department of Anesthesiology, University Hospital Antwerp, Belgium.
Moens
M M
MM
Jorens
P G
PG
Delrue
G L
GL
DePaep
R J
RJ
Vermeyen
K M
KM
D001283:Atrioventricular Node; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000627:therapeutic use; D002302:Cardiac Output / Q000187:drug effects; D002304:Cardiac Pacing, Artificial; D002315:Cardiopulmonary Bypass; D002316:Cardiotonic Agents / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D001026:Coronary Artery Bypass; D017558:Elective Surgical Procedures; D005260:Female; D006207:Half-Life; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D020105:Milrinone; D005996:Nitroglycerin / Q000627:therapeutic use; D009638:Norepinephrine / Q000008:administration & dosage / Q000627:therapeutic use; D011446:Prospective Studies; D011728:Pyridones / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D014665:Vasodilator Agents / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics
D002316:Cardiotonic Agents; D011728:Pyridones; D014665:Vasodilator Agents; D005996:Nitroglycerin; D020105:Milrinone; D002118:Calcium; D009638:Norepinephrine