[Evaluation of dopamine and dobutamine for use in circulatory depression associated with induced total spinal block]

We carried out total spinal block (T.S.B.) in adult mongrel dogs with 0.5 ml.kg-1 of 2% lidocaine, and compared the effects of dopamine (DOA) and dobutamine (DOB) to correct the circulatory depression produced by T.S.B. HR, MAP, LV dp/dt max. and CI decreased significantly by T.S.B. under continuous infusion of 2.5 mcg.kg-1.min-1 of both DOA and DOB. During DOA infusion these circulatory values decreased significantly compared with those of control period, while during DOB infusion they were unchanged. MAP, LV dp/dt max. and CI decreased significantly by T.S.B. under 5 mcg.kg-1.min-1 of DOA infusion, while influence was hardly observed by T.S.B. under DOB infusion. From the results, it is concluded that DOB is more effective than DOA to correct the circulatory depression by T.S.B., and in order to correct it more than 5 mcg.kg-1.min-1 of DOA and approx. 2.5 mcg.kg-.min-1 of DOB are necessary.