Perineural Administration of Dexmedetomidine in Axillary Brachial Plexus Block Provides Safe and Comfortable Sedation: A Randomized Clinical Trial.

Dexmedetomidine prolongs the duration of regional block while its systemic sedative effect when administered perineurally is unknown. We aimed to evaluate the systemic sedative effect of perineural dexmedetomidine in patients after axillary brachial plexus block (ABPB). This single-blinded prospective randomized control trial included 80 patients undergoing wrist surgery receiving ABPB. Patients were randomized into two groups - Control group (CG, N = 40) and dexmedetomidine group (DG, N = 40). Both groups received ABPB with 20 ml of 0.5% Bupivacaine and 10 ml of 2% Lidocaine. Additionally, patients in DG received 100 mcg of dexmedetomidine perineurally. Depth of sedation was evaluated using Narcontrend Index (NI) and Ramsay Sedation Scale (RSS) immediately after ABPB and in several time points up to 120 min. Duration of block as well as patient satisfaction with sedation was evaluated using a postoperative survey. Our results showed that NI and RSS statistically differed between groups, presenting a deeper level of sedation during the first 90 min in DG compared to controls, P < 0.001. In the first 10 to 60 min after ABPB the median RSS was 4 (IQR within median) and median NI was 60 (IQR 44-80) in DG group, in contrast to CG patients where median RSS was 2 (IQR within median) and median NI was 97 (IQR 96-98) throughout surgery. The level of sedation became equal in both groups 90 and 120 min after ABPB when the median NI value was 98 (97-99) in DG and 97.5 (97-98) in CG, P = 0.276, and the median RSS was 2 (IQR within median) in both groups, P = 0.128. No significant intergroup differences in hemodynamic or respiratory parameters were found. Patients in DG expressed satisfaction with sedation and 86.5% noted that the sensation was similar to ordinary sleep. In DG mean duration of motor block was 13.5 ± 2.1 h and sensory block was 12.7 ± 2.8 h which was significantly longer compared to CG 6.3 ± 1.5 h, P < 0.001 and 6.4 ± 1.8 h, P < 0.001. We found that beside prolongation of analgesia, perineural administration of dexmedetomidine might provide rather safe and comfortable sedation with no significant effect on hemodynamic or respiratory stability and yields a high level of patient satisfaction.

A randomized, observer-blinded determination of the median effective volume of local anesthetic required to anesthetize the sciatic nerve in the popliteal fossa for stimulating and nonstimulating perineural catheters.

BACKGROUND AND OBJECTIVES: Stimulating perineural catheters are developed to overcome technical problems of nonstimulating catheters, but their efficacy remains controversial. However, no volume-response study has compared success rates between stimulating and nonstimulating catheters. This study of stimulating versus nonstimulating catheters compares the minimal effective volume required to successfully block the sciatic nerve in 50% of patients scheduled for unilateral hallux valgus repair. METHODS: Patients underwent unilateral sciatic nerve block in the popliteal fossa with mepivacaine 1.5%, using either a stimulating (STIM group) or a nonstimulating (NONSTIM group) popliteal catheter. The volume of mepivacaine started at 20 mL and was increased or decreased by increments of 2 mL in subsequent patients, depending on the efficacy of the block in the previous patient, using the technique of up-down sequential allocation described by Dixon (Neurosci Biobehav Rev. 1991;15:47-50). Minimum effective volumes of local anesthetic were calculated using the formula of Dixon. Efficacy of block was defined by a complete sensory-motor block in the cutaneous distributions of the sciatic nerve associated with a pain-free surgery. RESULTS: Twenty-four patients were included in each group. Median effective volume blocking the sciatic nerve was significantly lower (P < 0.05) in the STIM group (2.7 mL; 95% confidence interval, 0.5-4.9 mL) compared with the NONSTIM group (16.6 mL; 95% confidence interval, 15.2-18.0 mL). CONCLUSION: Stimulating popliteal catheters dramatically decrease the volume required to block the sciatic nerve in 50% of patients, compared with nonstimulating catheters.

Ultrasound- or nerve stimulation-guided wrist blocks for carpal tunnel release: a randomized prospective comparative study.

BACKGROUND AND OBJECTIVES: We hypothesized that ultrasound-guided wrist blocks may be faster to perform, and may increase success rate, compared with nerve stimulation-guided wrist blocks. METHODS: Sixty patients undergoing ambulatory endoscopic carpal tunnel release were randomly allocated to receive median and ulnar nerve blocks using either sensory-motor nerve stimulation (n = 30) or ultrasound guidance (n = 30). Four mL of mepivacaine 1.5% was injected around each nerve. Performance time and onset time of complete sensory block were assessed. RESULTS: Median time to perform both median (ultrasound, 55 [48-60] vs. nerve stimulation, 100 [65-150] seconds, P = .002) and ulnar (ultrasound, 57 [50-70] vs. nerve stimulation, 80 [60-105] seconds, P = .02) nerve blocks were significantly shorter in the ultrasound group. Onset time of complete sensory block in the median (ultrasound, 370 [278-459] vs. nerve stimulation, 254 [230-300] seconds, P = .02) and ulnar (ultrasound, 367 [296-420] vs. nerve stimulation, 241 [210-300] seconds, P = .01) nerve areas were shorter in the nerve stimulation group. The success rate was 93% in both groups. CONCLUSIONS: This randomized prospective study demonstrates that ultrasound-guided wrist nerve blocks are as efficient as those performed with nerve stimulation.

Spinal anaesthesia and the use of anticoagulants.

This chapter addresses the increasing incidence of spinal haematoma after central neuraxis anaesthesia in patients receiving drugs that affect coagulation. Administration of low-molecular-weight heparins in the perioperative period is highlighted because these drugs remain the 'gold standard' for prophylaxis against deep-vein thrombosis. The performance of spinal anaesthesia in patients already receiving antiplatelet drugs is discussed--as well as special warnings in such a setting. In addition, issues such as those concerning the administration of unfractionated heparin, anti-vitamin K drugs or new antiplatelet and antithrombotic medications are addressed. Finally, specific recommendations regarding each class of drug are defined in order to avoid the occurrence of a rare but catastrophic event such as spinal haematoma.

[Regional anesthesia for lumbar microdiscectomy]. / Anesthésie locorégionale pour cure microchirurgicale des hernies discales lombaires.

GOAL OF THE STUDY: Lumbar microdiscectomy surgery is already performed under spinal anesthesia (SA) in many institutions. The aim of this study is to compare the quality of analgesia and recovery after SA when compared to general anesthesia (GA) after lumbar microdiscectomy surgery. METHODS: Following light sedation, SA is performed with the patient in the left lateral decubitus position, one to two levels above the herniated disc level. Isobaric 0.5% bupivacaine 3-3.5 ml was injected intrathecally followed by wound infiltration with 15 ml of bupivacaine with 1/200 000 epinephrine prior to surgical incision. RESULTS: Despite randomization, we found significantly more females in the GA group. Pain scores at 4 and 8 h postoperatively were lower in SA group as well as total analgesic consumption during the first 24 h. Postoperative recovery including time to drinking, eating and walking were more rapid after SA when compared to GA. During the postoperative period, the incidence of urinary retention was comparable between groups but the occurrence of postoperative nausea and vomiting was significantly higher in the GA group. Moreover, the overall patient's and surgeon's satisfaction were significantly better in the SA group. CONCLUSION: SA associated to wound infiltration using bupivacaine is an interesting alternative to general anesthesia for outpatient lumbar microdiscectomy surgery.