ABSTRACT
Motor systems operate over a range of frequencies and relative timing (phase). We studied the contribution of the hyperpolarization-activated inward current (Ih) to frequency and phase in the pyloric rhythm of the stomatogastric ganglion (STG) of the crab, Cancer borealis as temperature was altered from 11°C to 21°C. Under control conditions, the frequency of the rhythm increased monotonically with temperature, while the phases of the pyloric dilator (PD), lateral pyloric (LP), and pyloric (PY) neurons remained constant. When we blocked Ih with cesium (Cs+) PD offset, LP onset, and LP offset were all phase advanced in Cs+ at 11°C, and the latter two further advanced as temperature increased. In Cs+ the steady state increase in pyloric frequency with temperature diminished and the Q10 of the pyloric frequency dropped from ~1.75 to ~1.35. Unexpectedly in Cs+, the frequency displayed non-monotonic dynamics during temperature transitions; the frequency initially dropped as temperature increased, then rose once temperature stabilized, creating a characteristic "jag". Interestingly, these jags were still present during temperature transitions in Cs+ when the pacemaker was isolated by picrotoxin, although the temperature-induced change in frequency recovered to control levels. Overall, these data suggest that Ih plays an important role in the ability of this circuit to produce smooth transitory responses and persistent frequency increases by different mechanisms during temperature fluctuations.
ABSTRACT
OBJECTIVES: To assess the incidence of complications of fluoroscopically guided caudal epidural injections. DESIGN: A retrospective cohort design study in which chart review was performed on patients, who presented with radiculopathy and received fluoroscopically guided caudal epidural steroid injections. All injections were performed consecutively over a 12-mo period. An independent observer reviewed medical charts, which included a 24-hr post procedure telephone call by an ambulatory surgery center nurse, who asked a standardized questionnaire about complications after the injections. Physician follow-up office notes 1 to 3 wk after injection along with epidurograms were reviewed. RESULTS: The charts of 139 patients, who received 257 injections, were reviewed. Complications per injection included 12 episodes of insomnia the night of the injection (4.7%), 9 transient nonpositional headaches that resolved within 24 hr (3.5%), 8 increased back pain (3.1%), 6 facial flushing (2.3%), 2 vasovagal reactions (0.8%), 2 episodes of nausea (0.8%), and 1 increased leg pain (0.4%). No dural punctures occurred. CONCLUSIONS: No major complications occurred. The incidence of minor complications was 15.6% per injection. All reactions resolved without morbidity and no patient required hospitalization.
