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A dopamine infusion decreases propofol concentration during epidural blockade under general anesthesia

[Une perfusion de dopamine diminue la concentration de propofol pendant le bloc péridural sous anesthésie générale]

Daisuke Takizawa, MD^*,, Koichi Nishikawa, MD PhD^*, Eri Sato, MD^*,, Haruhiko Hiraoka, MD PhD^*, Koujirou Yamamoto, PhD, Shigeru Saito, MD PhD^*, Ryuya Horiuchi, PhD and Fumio Goto, MD PhD^*

^* From the Departments of Anesthesiology, and
Clinical Pharmacology, Gunma University Graduate School of Medicine, Maebashi, Japan.

Address correspondence to: Dr. Koichi Nishikawa, Department of Anesthesiology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi City 371-8511, Japan. Phone: 81-27-220-8454; Fax: 81-27-220-8473; E-mail: nishikaw{at}med.gunma-u.ac.jp

Purpose: 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 µg·mL^–1 at intubation and 2.0 µg·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 µg·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 µg·mL^–1 to 1.59 ± 0.29 µg·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.

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