A rat model of nerve stimulator-guided brachial plexus blockade

Lower jaw-to-forepaw rapid and delayed reorganization in the rat forepaw barrel subfield in primary somatosensory cortex

We used the forepaw barrel subfield (FBS), that normally receives input from the forepaw skin surface, in rat primary somatosensory cortex as a model system to study rapid and delayed lower jaw-to-forepaw cortical reorganization. Single and multi-unit recording from FBS neurons was used to examine the FBS for the presence of "new" lower jaw input following deafferentations that include forelimb amputation, brachial plexus nerve cut, and brachial plexus anesthesia. The major findings are as follows: (1) immediately following forelimb deafferentations, new input from the lower jaw becomes expressed in the anterior FBS; (2) 7-27 weeks after forelimb amputation, new input from the lower jaw is expressed in both anterior and posterior FBS; (3) evoked response latencies recorded in the deafferented FBS following electrical stimulation of the lower jaw skin surface are significantly longer in both rapid and delayed deafferents compared to control latencies for input from the forepaw to reach the FBS or for input from lower jaw to reach the LJBSF; (4) the longer latencies suggest that an additional relay site is imposed along the somatosensory pathway for lower jaw input to access the deafferented FBS. We conclude that different sources of input and different mechanisms underlie rapid and delayed reorganization in the FBS and suggest that these findings are relevant, as an initial step, for developing a rodent animal model to investigate phantom limb phenomena.

Establishment of ultrasound-guided stellate ganglion block in rats

Background

A novel protocol for accurate stellate ganglion block under ultrasound guidance was designed in rats. This technique raises the success rate of stellate ganglion block and reduces the incidence of brachial plexus and vagus nerve block.

Methods

Fifty-six Sprague-Dawley were randomly divided into an ultrasound-guided group (n = 28) and a blind technique group (n = 28). The rats in the blind technique group were injected with 1.5% lidocaine mixed with methylene blue after signs of brachial plexus stimulation were elicited. The lateral side of the cephalic brachial vein was located under the first rib, where lidocaine was injected into the rats in the ultrasound-guided group. The up-and-down sequential method of Dixon was used to determine the minimum effective volume for stellate ganglion block in rats. Furthermore, we calculated the required operative duration of the two methods and observed the difference in the lidocaine diffusion range between the two groups.

Results

The minimum effective volume for stellate ganglion block in the ultrasound-guided group was 0.040 ml, and the 95% CI was 0.026-0.052 ml. In the blind technique group, the minimum effective volume was 0.639 ml, and the 95% CI was 0.490-0.733 ml. Within the 95% CI of the lowest effective volume, the incidence of brachial plexus block as a complication of stellate ganglion block under ultrasound guidance was 10.00%.

Conclusion

Stellate ganglion block under ultrasound guidance is more accurate than blind detection, which the incidence of complications of stellate ganglion block under ultrasound guidance was significantly lower than under blind detection; the rate of methylene blue staining in the vagus nerve was significantly lower under ultrasound guidance.

Anatomorphometry of the brachial plexus under high-definition system: an experimental study in rats

PURPOSE

To study the anatomorphometry of the plexus brachialis (PB) of rats under a high-definition video system.

METHODS

Ten male Wistar rats discarded from other research that did not interfere in the morphology of the animal, respecting the principle of reduction, were used. All animals were submitted to the same protocol. Initially, the cervical region was shaved. The animals were placed in a dorsal position. A single elbow-to-elbow incision was performed and dissection started at the deltopectoral sulcus. The procedures were performed under a video system. To measure the structures, the Image J software was used.

RESULTS

All the PB evaluated originated from the C5-T1 spinal nerves. C5 and C6 converged to form the truncus superior, the root of C7 originated the truncus medius, and the confluence of C8 and T1 originated the truncus inferior. It was found the union of C7, C8, and T1 to form truncus inferomedialis instead of separate medial and inferior truncus. C8 (1.31 mm) was the thickest root, the truncus inferior (1.80 mm) and the nerve radialis (1.02 mm), were the thickest.

CONCLUSIONS

The anatomy of the PB is comparable to humans, admitting variations. The videomagnification system is useful to perform microsurgical dissection.