A comparison of motor stimulation threshold in ultrasound-guided interscalene brachial plexus block for arthroscopic shoulder surgery: a randomized trial.

BACKGROUND: As the use of ultrasound for regional anesthesia has increased, many studies have examined the distribution of local anesthetic and the location of the needle tip. Nevertheless, the relationship between motor stimulation threshold and distribution of local anesthetic is unclear. The aim of this study was to compare block onset time, distribution of local anesthetic, and location of the needle tip at two different motor stimulation thresholds, i.e., 0.2 and 0.5 mA, used in combination with ultrasound guidance. METHODS: This study included 94 patients undergoing arthroscopic shoulder surgery with ultrasound-guided interscalene brachial plexus block (ISBPB) plus nerve stimulation. Patients were randomized into two groups for the ISBPB procedure, i.e., when an evoked motor response was obtained at a current intensity of either 0.2 mA (Group 0.2) or 0.5 mA (Group 0.5). Block onset time, location of the needle tip, and distribution of local anesthetic were assessed. RESULTS: A response was elicited at the appropriate motor stimulation threshold in 88 patients (Group 0.2 = 43; Group 0.5 = 45). Block failure occurred in only three patients, all of whom were in Group 0.5. The mean [standard deviation (SD)] of block onset time was 8.0 (4.1) min in Group 0.2 and 11.4 (5.9) min in Group 0.5 [mean difference, 3.4 min; 95% confidence interval (CI), 1.2 to 5.9; P = 0.003]. The needle tip was located at a intraplexus position in 33 (77%) patients in Group 0.2 and in 15 (33%) patients in Group 0.5 (difference in proportion, 43%; 95% CI, 23 to 59; P < 0.001). The intramuscular spreading of local anesthetic occurred in 0 (0%) patients in Group 0.2 and in 8 (18%) patients in Group 0.5 (difference in proportion, 18%; 95% CI, 6 to 31; P = 0.007). CONCLUSION: The onset time of the block was significantly faster with a motor stimulation threshold of 0.2 mA than with a threshold of 0.5 mA.

Fluoroscopic analysis of lumbar epidural contrast spread after retrograde interlaminar ventral epidural injection (RIVEI).

BACKGROUND: Retrograde interlaminar ventral epidural injection (RIVEI) may hypothetically be more effective if the catheter is placed at the ventrocaudal aspect of the exiting nerve. We tested that hypothesis by measuring ventral and dorsal epidural contrast flow during RIVEI. METHODS: To perform RIVEI, a 17 G Tuohy needle was inserted to access the epidural space. A 19 G epidural catheter was inserted and advanced through the needle, passing in a caudal direction to the lower aspect of the contralateral pedicle. Fluoroscopic images were recorded at 1.5 ml increments of contrast. Based on the images of contrast dispersal, the extent of contrast spreading was assessed in 82 patients. RESULTS: All 82 patients (100%) injected with 3.0 ml contrast medium demonstrated ventral epidural spreading. Mean spreading level from the catheter tip was 2.21 ± 0.93 with 3.0 ml of contrast. Spreading to the superior aspect of the supra-adjacent intervertebral disc was observed in 67/82 (81.7%) of RIVEIs with 3.0 ml of contrast injected into the ventral epidural space. We found that 3.0 ml of contrast reached the inferior aspect of the infra-adjacent intervertebral disc in 95.1% (78/82) of RIVEIs performed. CONCLUSIONS: Our findings imply that a one-level RIVEI may be sufficient in situations where a two-level injection would currently be used.

Minimum current requirement for confirming the localization of an epiradicular catheter placement.

BACKGROUND: Based on the necessity to confirm the epiradicular catheter misplacement, epiradicular threshold current for the confirmation of catheter tip localization is required. METHODS: Thirty-four adult patients with low extremity radiating pain were to receive epiradicular catheterization at the lumbosacral level. The epidural space was accessed percutaneously in cranial to caudal direction. A metal coil-reinforced epidural catheter was inserted and advanced caudolaterally toward the target neural foramen until the catheter tip was located below the bisection of pedicle. The electrical stimulation was performed after catheter placement in epidural and epiradicular space. Using the constant current nerve stimulator, the stimulating current was increased from 0 to 5 mA (pulse width of 0.3 ms; frequency of 2 Hz) until adequate motor contraction was evident. The threshold current for motor response with epidural space (EDmA) and epiradicular space (ERmA) placement were recorded upon electrical stimulation. In addition, the threshold charge for motor response with epidural (EDnC) and epiradicular (ERnC) placement were recorded. RESULTS: Of 34 catheters intentionally placed in the epiradicular space, ERmA was 0.53 ± 0.48 mA. The ERnC was significantly lower than EDnC (P < 0.05). The EDmA and ERmA were below 1 mA in 3 patients and above 1 mA in 4 patients, respectively. CONCLUSIONS: We conclude that, threshold current for motor response seems to be lower for epiradicular compared with epidural placement, although we were not able to directly investigate the epidural threshold current. The threshold current of epiradicular space overlap that in the epidural space.

Ultrasound-guided greater occipital nerve block for patients with occipital headache and short term follow up.

BACKGROUND: The greater occipital nerve (GON) block has been frequently used for different types of headache, but performed with rough estimates of anatomic landmarks. Our study presents the values of the anatomic parameters and estimates the effectiveness of the ultrasound-guided GON blockade. METHODS: The GON was detected using ultrasound technique and distance from external occipital protuberance (EOP) to GON, from GON to occipital artery and depth from skin to GON was measured in volunteers. Patients with occipital headache were divided into two groups (ultrasound-guided block: group S, conventional blind block: group B) and GON block was performed. The same parameters were measured on group S and VAS scores were assessed at pretreatment, 1 week and 4 weeks after treatment on both groups. RESULTS: The GON had distance of 23.1 ± 3.4 mm (right) and 20.5 ± 2.8 mm (left) from EOP to GON. Its depth below the skin was 6.8 ± 1.5 mm (right) and 7.0 ± 1.3 mm (left). The distance from GON to occipital artery was 1.5 ± 0.6 mm (right) and 1.2 ± 0.6 mm (left) in volunteers. Initial VAS score of group S and group B patients were 6.4 ± 0.2 and 6.5 ± 0.2. VAS score of 4 weeks after injection were 2.3 ± 0.2 on group S and 3.8 ± 0.3 on group B (P = 0.0003). CONCLUSIONS: The parameters measured in this study should be useful for GON block and ultrasound-guided blockade is likely to be a more effective technique than blind blockade in occipital headache treatment.

A randomized controlled trial of radiofrequency denervation of the ramus communicans nerve for chronic discogenic low back pain.

OBJECTIVE: The objective of this study was to determine the efficacy of percutaneous radiofrequency (RF) thermocoagulation of the ramus communicans nerve in patients suffering from chronic discogenic low back pain. METHODS: Forty-nine patients who suffered chronic discogenic low back pain at only 1 painful vertebral level, and whose pain continued after undergoing intradiscal electrothermal annuloplasty (IDET), were randomly assigned to 1 of 2 treatment groups. The lesion group (n = 26) received RF thermocoagulation of the ramus communicans nerve. Patients in the control group (n = 23) received an injection of lidocaine without radiofrequency. Visual analog scale (VAS) pain scores, analgesic requirements, SF-36 subscales, and the overall patient satisfaction with the procedure were tabulated. RESULTS: The average follow-up period was 4 months. The patient-reported VAS pain scores were significantly lower (P < 0.05) in the lesion group. The scores of the RF lesion group improved by a mean increase of 11.3 points (P < 0.05) on the SF-36 bodily pain subscale, and by a mean increase of 12.4 points on the physical function subscale (P < 0.05). In a follow-up analysis within the RF lesion group, VAS pain scores improved by a mean reduction of 3.32 (P = 0.001). The scores improved by a mean increase of 14.5 points (P = 0.005) on the SF-36 bodily pain subscale and 15.2 points(P = 0.002) on the physical function subscale within the RF lesion group. One patient in the lesion group complained of mild lower limb weakness, but he completely recovered at postoperative 15 days without any serious problems. DISCUSSION: In patients with chronic discogenic low back pain, percutaneous RF denervation of the ramus communicans nerve should be considered as a treatment option.