Evaluation of epidural sensory block by thermal stimulation, laser stimulation, and recording of somatosensory evoked potentials.
ABSTRACT The existence of differential sensory block during epidural analgesia has been confirmed by some authors and disputed by others. This study attempts to elucidate this issue by using quantitative methods for evaluation of sensory block.
A single epidural injection of 20 mL 0.5% bupivacaine with epinephrine was administered at the L1-T12 level in 11 male volunteers. Sensory block was evaluated by two qualitative (pinprick and light touch) and two quantitative methods (thermal stimulation with Thermotest [Somedic, Stockholm, Sweden] and argon laser stimulation). For measurement of motor block in the lower extremities and in the rectus abdominis muscle, quantitative methods were used. Sensory block was also assessed by somatosensory evoked potentials recorded during electrical and laser stimulation at the most cranial analgesic dermatome (loss of sharpness in pinprick perception) and the anesthetic dermatome L2 (loss of light touch perception).
The zone of anesthesia was smaller than the zone of any other investigated variable. The cranial spread of analgesia and motor block was lower than that of laser-assessed block. Partial block of laser perception and thermal perception lasted longer than analgesia and motor block. No consistent segmental or temporal differences were found between the Thermotest and laser methods. During epidural block, prolongation of latencies and reduction in amplitudes of somatosensory evoked potentials produced at the most cranial analgesic dermatome did not differ significantly from those produced at the anesthetic dermatome.
No differential block of small nerve fibers was found during epidural analgesia by Thermotest and argon laser stimulation. Recording of somatosensory evoked potentials did not demonstrate significant difference between responses from the sites with most superficial and with most intense sensory block.
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ABSTRACT: The purpose of the present study is to investigate the anesthetic effect of reduced doses of spinal bupivacaine with epidural top ups in comparison with those of spinal bupivacaine and to determine the adequate doses of drugs used during lower extremity surgeries. SIXTY ADULT PATIENTS WERE RANDOMIZED TO THREE DIFFERENT TECHNIQUE GROUPS: S group (10 mg of spinal bupivacaine), SE1 group (7.5 mg of spinal bupivacaine + epidural 1.5% lidocaine 10 ml) or SE2 group (5 mg of spinal bupivacaine + epidural 1.5% lidocaine 10 ml). The level of sensory block, modified Bromage motor scores (MBS), systolic blood pressure and heart rate were recorded for 30 min following anesthesia. Peak sensory block height and MBS, time for sensory regression to L1 and motor recovery to MBS 1, side effects and operator's satisfaction were noted. The levels of peak sensory block were similar among the groups (P > 0.05). For the SE2 group, the regression to the L1 dermatome was faster (P = 0.004) and the maximum MBS was lower (P = 0.001) than that of the other two groups. Motor block recovery to MBS 1 was faster for the SE1 and SE2 groups than for the S group (P < 0.001). The operator's satisfaction scores of the SE2 group were lower than those of the other two groups (P = 0.019). During combined spinal-epidural anesthesia, 7.5 mg of spinal bupivacaine and epidural 1.5% lidocaine 10 ml produced faster motor recovery than did 10 mg of spinal bupivacaine in patients undergoing lower extremity surgeries.Korean journal of anesthesiology 01/2014; 66(1):28-33. DOI:10.4097/kjae.2014.66.1.28
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ABSTRACT: Adequate treatment of cancer pain remains a significant clinical problem. To reduce side effects of treatment, intrathecal and epidural routes of administration have been used where appropriate to reduce the total dose of agent administered while achieving regional control. Resiniferatoxin (RTX), an ultrapotent capsaicin analog, gives long-term desensitization of nociception via C-fiber sensory neurons. We evaluate here the analgesic effect on rats of epidurally administered RTX, using latency of response to a thermal stimulus in unrestrained animals. Results were compared with those for systemically administered RTX. Vehicle or graded doses of RTX were injected subcutaneously (s.c.) or through an indwelling lumbar (L4) epidural catheter as a single dose. Both routes of application of RTX produced profound thermal analgesia, reaching a plateau within 4-6 h and showing no restoration of pain sensitivity over 7 days. Vehicle was without effect. For the epidural route, the effect was selective as expected for the targeted spinal cord region, whereas the subcutaneous administration of RTX had a generalized analgesic effect. At doses yielding a tripling of back paw withdrawal latency, epidural treatment was 25-fold more effective than the subcutaneous route of application. Consistent with the regional selectivity of the lumbar epidural route, the front paws showed no more effect than by systemic RTX treatment. Binding experiments with [3H]RTX provided further evidence of the segmental desensitization induced by epidural RTX. We conclude that epidural administration of RTX at the lumbar spinal level produces profound, long-lasting, segmental analgesia to C-fiber mediated pain in the rat.Brain Research 10/1999; 840(1-2):92-8. DOI:10.1016/S0006-8993(99)01763-1 · 2.83 Impact Factor
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ABSTRACT: We arranged a mini-invasive surgical approach for implantation of paddle electrodes for SCS under spinal anesthesia obtaining the best paddle electrode placement and minimizing patients' discomfort. We describe our technique supported by neurophysiological intraoperative monitoring and clinical results. 16 patients, affected by neuropathic pain underwent the implantation of paddle electrodes for spinal cord stimulation in lateral decubitus under spinal anesthesia. The paddle was introduced after flavectomy and each patient confirmed the correct distribution of paresthesias induced by intraoperative test stimulation. VAS and patients' satisfaction rate were recorded during the followup and compared to preoperative values. No patients reported discomfort during the procedure. In all cases, paresthesias coverage of the total painful region was achieved, allowing the best final electrode positioning. At the last followup (mean 36.7 months), 87.5% of the implanted patients had a good rate of satisfaction with a mean VAS score improvement of 70.5%. Spinal cord stimulation under spinal anesthesia allows an optimal positioning of the paddle electrodes without any discomfort for patients or neurosurgeons. The best intraoperative positioning allows a better postoperative control of pain, avoiding the risk of blind placements of the paddle or further surgery for their replacement.The Scientific World Journal 04/2012; 2012:201053. DOI:10.1100/2012/201053 · 1.73 Impact Factor