A dopamine infusion decreases propofol concentration during epidural blockade under general anesthesia.
OBJECTIVE
It is common clinical practice to use dopamine to manage the reduction in blood pressure accompanying epidural blockade. As propofol is a high-clearance drug, propofol concentrations can be influenced by cardiac output (CO). The purpose of the present study was to investigate the effects of dopamine infusions on propofol concentrations administered by a target-controlled infusion system during epidural block under general anesthesia.


METHODS
12 patients undergoing abdominal surgery were enrolled in this study. Anesthesia was induced with propofol and vecuronium 0.1 mg.kg(-1), and maintained using 67% nitrous oxide, sevoflurane in oxygen and constant infusion of propofol. Propofol was administered to all subjects via target-controlled infusion to achieve a propofol concentration at 6.0 microg.mL(-1) at intubation and 2.0 microg.mL(-1) after intubation. Before and after the administration of 10 mL of 1.5% mepivacaine from the epidural catheter and dopamine infusion at 5 microg.kg(-1).min(-1), CO and effective liver blood flow (LBF) were measured using indocyanine green. Blood propofol concentration was also determined using high-performance liquid chromatography.


RESULTS
At one hour after epidural block and dopamine infusion, CO was significantly increased from 4.30 +/- 1.07 L.min(-1) to 5.82 +/- 0.98 L.min(-1) (P < 0.0001), and effective LBF was increased 0.75 +/- 0.17 L.min(-1) to 0.96 +/- 0.18 L.min(-1) (P < 0.0001). Propofol concentration was significantly decreased from 2.13 +/- 0.24 microg.mL(-1) to 1.59 +/- 0.29 microg.mL(-1) (P < 0.0001).


CONCLUSIONS
Propofol concentrations decrease with an increase in CO, suggesting the possibility of inadequate anesthetic depth following catecholamine infusion during propofol anesthesia.
Takizawa
Daisuke
D
Department of Anesthesiology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi City 371-8511, Japan.
Nishikawa
Koichi
K
Sato
Eri
E
Hiraoka
Haruhiko
H
Yamamoto
Koujirou
K
Saito
Shigeru
S
Horiuchi
Ryuya
R
Goto
Fumio
F
D000368:Aged; D000767:Anesthesia, Epidural; D000768:Anesthesia, General; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage / Q000493:pharmacokinetics*
D004298:Dopamine; D015742:Propofol