脊骨随鎮痛機構におけるノルエピネフリンの役割

抄録

We investigated the effects on systemic blood pressure of adding norepinephrine (NE) to epidural anesthesia, and the duration of the analgesia. Blood pressure changes were significantly minimized by adding NE (5μg/ml) to mepivacaine, compared with plain mepivacaine in senior (over 65 years old) patients. Plasma NE levels increased significantly during NE-added epidural anesthesia. NE levels in cerebrospinal fluid (CSF) increased at 15 min and 30 min after epidural administration. The duration of anesthesia was significantly longer in patients who received NE-added bupivacaine.
We also investigated the effects of adding epinephrine and norepinephrine to dibucaine on the duration of spinal anesthesia and on the CSF catecholamine (CA) levels. The CSF-free NE level was 0.104 ± 0.028 ng/ml at the pre-anesthetic stage. Then it increased to 5.0 ng/ml and 1000ng/ml respectively 2 min after 1 μg or 50 μg of NE with dibucaine administration. The duration of sensory and motor blockade was significantly prolonged by 2.5μg of NE with dibucaine, but was not changed by 2.5 μg of epinephrine with dibucaine.
These data suggest that, in epidural anesthesia, NE absorbed into the blood stream helps to maintain blood pressure, and NE passed into CSF may be useful in prolonging the analgesic action of local anesthetics. In spinal anesthesia, a small added dose of NE, 2.5 μg, was enough to prolong the anesthesia. The amount of CA added to spinal anesthetic solutions should be severely restricted to prevent ischemic damage to the spinal cord.