A. Onda et al., Effects of lidocaine on blood flow and endoneurial fluid pressure in a ratmodel of herniated nucleus pulposus, SPINE, 26(20), 2001, pp. 2186-2191
Study Design. An experimental study was conducted to evaluate the effects o
f lidocaine on nucleus pulposus-induced pathophysiologic changes.
Objectives. To investigate the effects of lidocaine on blood flow in the hi
nd paws and endoneurial fluid pressure in the dorsal root ganglia in a rat
model of herniated nucleus pulposus, and to clarify the therapeutic mechani
sms of nerve root infiltration.
Summary of Background Data. It has been shown experimentally that applicati
on of nucleus pulposus to the nerve roots increases endoneurial fluid press
ure and decreases blood flow in the dorsal root ganglia and the correspondi
ng hind paw. These changes are thought to be an important pathogenic mechan
ism associated with sciatica caused by disc herniation. Nerve root infiltra
tion is one of the nonoperative effective therapies for radiculopathy. caus
ed by disc herniation. However, the therapeutic mechanisms still are unknow
n.
Methods. For this study, 21 Sprague-Dawley rats were used. Autologous nucle
us pulposus was applied to the nerve root with a piece of Spongel containin
g lidocaine (lido group) or physiologic saline solution (control group). In
Series 1 of this study (Blood Flow in the Hind Paw), blood flow in the cor
responding hind paws was monitored continuously using a laser Doppler flowm
eter before application of the test solutions, and every 5 minutes thereaft
er for an additional 3 hours in both the control (n = 5) and lido (n = 5) g
roups. In Series 2 of this study (Endoneurial Fluid Pressure in the Dorsal
Root Ganglion), endoneurial fluid pressure was recorded with a servo-null m
icropipette system using glass micropipettes before and 3 hours after appli
cation of the test solutions in both the control (n = 6) and lido (n = 5) g
roups. After measurements, dorsal root ganglia were assessed for histology.
Results. In Series 1, blood flow in the corresponding hind paw in the contr
ol group showed significant reduction as compared with that of the Lido gro
up, starting about 90 minutes after application (P < 0.01-0.05). Hind paw b
lood flow in the lido group did not show any reduction during measurements.
In Series 2, the value of andoneurial fluid pressure in the lido group 3 h
ours after application was significantly lower than in the control group (P
< 0.01). Interstitial (endoneurial) edema in the dorsal root ganglion in t
he lido group appeared to be qualitatively less than in the control group.
Conclusions. The data indicate that lidocaine reduces the pathophysiologic
changes in the dorsal root ganglion and hind paws induced by nucleus pulpos
us. These effects of lidocaine may relate to the mechanisms underlying the
therapeutic effects of nerve root infiltration.