Effect of epidural anesthesia on sympathetic nerve activities.

background:The sympathetic nerve blockade by epidural anesthesia dilates peripheral vessels and induceshypotension. The sympathetic nerve activity in The unblocked area may induce The fall of hand skintemperature and toe pulse amplitude. To estimate compensatory sympathetic excitation in theunblocked area,我们方法直接cardiac（CSNA）和renal sympathetic nerve activities(RSNA) simultaneouslyduring thoracic(TEA) or lumbar epidural anesthesia(LEA) in cat . methods：The cats were divided into three groups；6 cats in the TEA group received an epidural catheter at T4,6 cats in the LEA group at L1，and 3 cats in the LEA plus denervation group at L1 following sino-aortic and vagal denervations. 3 cats in the LEA plus denervation group at L1 following sino-aortic and vagal denervations.Heart rate(HR), mean arterial pressure(MAP)， CSNA，and RSNA were measured repeatedly for 30 min after a single dose of 0.1ml / kg <-1> of 1% lidocainevia the epidural catheter.Results：In the TEA group, HR decreased to 91%, MAP decreased to 87%, CSNA decreased to 26%，RSNA increased to 144% from 100% of the control values. In the LEA group, HR decreased to 93%，MAP decreased to 87%, CSNA increased to 164%and RSNA decreased to 30%. In the LEA plus denervation group, HR decreased to 93%，MAP decreased to 73%, and RSNA decreased to 42%, but CSNA unchanged.Conclusion：sympathetic nerve activity in The unblocked area increased in relation to hypotension duringthoracic or lumbar epidural anesthesia. This sympathetic excitation disappeared during lumbarepidural anesthesia following sino-aortic and vagal denervations. The compensatory excitation of Thesympathetic nerves results from the baroreceptor reflex to hypotension induced by epiduralanesthesia。

Background : The sympathetic nerve blockade by epidural anesthesia dilates peripheral vessels and induces hypotension. The sympathetic nerve activity in the unblocked area may induce the fall of hand skin temperature and toe pulse amplitude. To estimate compensatory sympathetic excitation in the unblocked area, we measured directly cardiac(CSNA) and renal sympathetic nerve activities(RSNA) simultaneously during thoracic(TEA) or lumbar epidural anesthesia(LEA) in cats.Methods : The cats were divided into three groups ; 6 cats in the TEA group received an epidural catheter at T4,6 cats in the LEA group at L1, and 3 cats in the LEA plus denervation group at L1 following sino-aortic and vagal denervations. Heart rate(HR), mean arterial pressure(MAP), CSNA, and RSNA were measured repeatedly for 30 min after a single dose of 0.1ml・kg^<-1> of 1% lidocaine via the epidural catheter.Results : In the TEA group, HR decreased to 91%, MAP decreased to 87%, CSNA decreased to 26%, and RSNA increased to 144% from 100% of the control values. In the LEA group, HR decreased to 93%, MAP decreased to 87%, CSNA increased to 164%, and RSNA decreased to 30%. In the LEA plus denervation group, HR decreased to 93%, MAP decreased to 73%, and RSNA decreased to 42%, but CSNA unchanged.Conclusion : The sympathetic nerve activity in the unblocked area increased in relation to hypotension during thoracic or lumbar epidural anesthesia. This sympathetic excitation disappeared during lumbar epidural anesthesia following sino-aortic and vagal denervations. The compensatory excitation of the sympathetic nerves results from the baroreceptor reflex to hypotension induced by epidural anesthesia.