SPINAL-CORD BLOOD-FLOW AFTER INTRATHECAL INJECTION OF ROPIVACAINE ANDBUPIVACAINE WITH OR WITHOUT EPINEPHRINE IN RATS

Background: Ropivacaine is a new local anaesthetic available for spina l and epidural anaesthesia. When new drugs are being introduced for sp inal application, their effect on spinal cord blood flow (SCBF) should be studied for safety and toxicological aspects. In the present study , SCBF was studied after intrathecal (i.t.) application of ropivacaine and bupivacaine with and without epinephrine. Method: SCBF was measur ed continuously in spontaneously breathing, enflurane/N2O anaesthetize d rats, using laser-Doppler er flowmetry technique. The spinal cord wa s exposed by laminectomy at the L-1-L-2 level, and a laser-Doppler pro be was placed over the dorsal horn, allowing on-line registration of S CBF in a tissue hemisphere of 1-2 mm. Relative changes in SCBF were th en measured on-line after i.t, administration of increasing doses of r opivacaine, bupivacaine or bupivacaine with epinephrine. Results: Ropi vacaine and bupivacaine decreased SCBF in a dose-dependent manner. In contrast, the reduction in SCBF produced by bupivacaine + epinephrine (Bupi+Epi) was equal for all doses of bupivacaine. The order of magnit ude of SCBF decreases was Bupi + Epi >ropivacaine>bupivacaine. The max imal decrease in SCBF at the highest concentration given (10 mg/ml) wa s 37+/-6% for ropivacaine, 27+/-7% for bupivacaine and 40+/-6% for bup ivacaine + epinephrine. Conclusion: Ropivacaine and bupivacaine produc e a dose-related, transient decrease in SCBF following i.t. administra tion in anaesthetized rats. However, the decrease in SCBF produced by both ropivacaine and bupivacaine was less than that produced by bupiva caine, when epinephrine was added in a concentration of 5 mu g/ml. The se results suggest that ropivacaine, like bupivacaine, may be used for spinal anaesthesia without important effects on SCBF.