Effect of axillary blockade on regional cerebral blood flow during static handgrip

Regional cerebral blood flow (rCBF) was determined at rest and during static handgrip before and after regional blockade with lidocaine. A fast rotating single photon emission computer tomograph system with 133Xe inhalation was used at orbitomeatal plane (OM) +2.5 and +6.5 cm in eight subjects. Median handgrip force during the control study was 41 (range 24-68) N, which represented 10% of the initial maximal voluntary contraction (MVC) and was 24 (18-36) N after axillary blockade (P less than 0.05), which represented 21% of the new MVC. During static handgrip, the rating of perceived exertion was 14 (10-16) exertion units before and 18 (15-20) after blockade (P less than 0.05). Hemispheric mean CBF did not change during handgrip. However, premotor rCBF increased from 55 (44-63) to 60 (50-69) ml.100 g-1.min-1 (P less than 0.05) and motor sensory rCBF from 57 (46-65) to 63 (55-71) ml.100 g-1.min-1 (P less than 0.05) to both the ipsilateral and contralateral sides during handgrip before, but not after, axillary blockade. There was no change in rCBF to other regions of the brain. Regional anesthesia with lidocaine did not alter resting rCBF. However, despite a greater sense of effort during static handgrip, there was no increase in rCBF after partial sensory and motor blockade. Thus bilateral activation occurs in the premotor and motor sensory cortex during static handgrip, and this activation requires neural feedback from the contracting muscles.