Spinal or Intravenous Dexmedetomidine for Spinal Anesthesia with Chloroprocaine in Ambulatory Knee Arthroscopies: A Double-Blind Randomized Trial.

PURPOSE: Chloroprocaine provides spinal anesthesia for day-case surgery lasting up to 40 minutes. Intravenous and spinal dexmedetomidine can prolong spinal anesthesia, but no data are available for the combination with chloroprocaine. This double-blind randomized controlled trial compares chloroprocaine with spinal or intravenous dexmedetomidine regarding block characteristics, micturition, and discharge times. PATIENTS AND METHODS: After ethical approval and informed consent, 135 patients scheduled for knee arthroscopy were randomized to receive either 40mg spinal chloroprocaine (Chloro-group), 40mg chloroprocaine with 5 mcg spinal dexmedetomidine (Spinal Dex-group) or 40mg chloroprocaine with 0.5 mcg/kg IV dexmedetomidine (IV DEXgroup). Block characteristics, hemodynamic variables and the use of analgesics were registered. Voiding and discharge times were noted. A scoring system was used for micturition problems and sedation. Transient neurological symptoms (TNS) and other late side effects were evaluated after one week. RESULTS: Demographic data were similar between groups. Block onset times and intensity of motor block were comparable between groups. The time to L2 and Bromage 1 regression was prolonged in the SpinalDEx-group by approximately 30 minutes compared to the other groups (p < 0.01). First voiding as well as discharge from the hospital was prolonged in the Spinal Dex-group by approximately 40 minutes p < 0.01. There was no significant difference between groups regarding treatment of hypotension, sedation, micturition problems or the use of postoperative analgesics (P > 0.8). One patient experienced TNS. CONCLUSION: Intrathecal but not intravenous (0.5 mcg/kg) dexmedetomidine can prolong chloroprocaine (40mg) spinal anesthesia when surgery is expected to last over 40 minutes. Despite a similar incidence of adverse effects, this also led to a postponed hospital discharge time.

Levobupivacaine Consumption in Automated Intermittent Bolus in Ultrasound Guided Subparaneural Sciatic Nerve Catheters: A Prospective Double-Blind Randomized Trial.

PURPOSE: Continuous sciatic nerve blocks have proven benefits for postoperative analgesia after foot surgery. However, the optimal mode of administration remains a point of debate. Ultrasound guided subparaneural injection accelerates onset time and increases duration after a single shot sciatic nerve block. This double blind prospective randomized trial compares the 48-hour local anesthetic (LA) dose consumption of an automated intermittent bolus technique to a continuous infusion regimen in a subparaneural sciatic nerve catheter after hallux valgus surgery. PATIENTS AND METHODS: Patients scheduled for hallux valgus surgery were randomized to receive either a continuous infusion of levobupivacaine 0.125% at 5mL/h (group A) or an intermittent automated bolus of 9.8 mL every 2 hours with a background of 0.1 mL/h (group B), both with a PCA bolus of 6 mL and lockout of 30 minutes. The 48 hour LA consumption, PCA boluses, Numeric Rating Scale (NRS), satisfaction and return of normal sensation were recorded. RESULTS: Sixteen patients were excluded because of protocol violation or technical problems and 42 patients remained for analysis. The 48 hour ropivacaine consumption was higher in group A (293 ±60 mL) than group B (257±33 mL). The median and highest NRS scores and patient satisfaction were not statistically different between groups. Normal sensation returned after 75 ± 22 hours (group A) and 70 ± 17 hours (group B). CONCLUSION: Programmed bolus administration in subparaneural sciatic nerve catheters reduces LA consumption 48 hours after surgery with equal analgesia and patient satisfaction. Return of sensation is variable and can last more than 75 hours.

A low dose of three local anesthetic solutions for interscalene blockade tested by thermal quantitative sensory testing: a randomized controlled trial.

This randomized double-blind controlled trial compared the block characteristics of three low-dose local anesthetics at different roots in an ultrasound-guided interscalene block, using thermal quantitative sensory testing for assessing the functioning of cutaneous small nerve fibres. A total of 37 adults scheduled to undergo shoulder arthroscopy were randomized to receive 5 mL of either 0.5% levobupivacaine with and without epinephrine 1/200,000 or 0.75% ropivacaine in a single-shot interscalene block. Thermal quantitative sensory testing was performed in the C4, C5, C6 and C7 dermatomes. Detection thresholds for cold/warm sensation and cold/heat pain were measured before and at 30 min, 6, 10 and 24 h after infiltration around C5. The need for rescue medication was recorded. No significant differences between groups were found for any sensation (lowest P = 0.28). At 6 h, the largest differences in sensory thresholds were observed for the C5 dermatome. The increase in thresholds were less in C4 and C6 and minimal in C7 for all sensations. The analgesic effect lasted the longest in C5 (time × location mixed model P < 0.001 for all sensory tests). The time to rescue analgesia was significantly shorter with 0.75% ropivacaine (P = 0.02). The quantitative sensory findings showed no difference in intensity between the local anesthetics tested. A decrease in block intensity, with minimal changes in pain detection thresholds, was observed in the roots adjacent to C5, with the lowest block intensity in C7. A clinically relevant shorter duration was found with 0.75% ropivacaine compared to the other groups. Trial registration NCT 02691442.

Effects of Stellate Ganglion Block on Analgesia Produced by Cervical Paravertebral Block as Established by Quantitative Sensory Testing: A Randomized Controlled Trial.

Objective: To use quantitative sensory testing (QST) to assess whether a stellate ganglion block (SGB) modulates the analgesia induced by cervical paravertebral block (CPVB). Design: A prospective double-blind randomized controlled trial. Setting: Department of Anesthesia, Antwerp University Hospital, October 2011 to December 2015. Subjects: Twenty-eight adults scheduled for arthroscopy of a nonfractured shoulder were enrolled. Methods: Participants were randomly assigned to receive either single CPVB (5 mL of levobupivacaine 0.5%) or combined CPVB + SGB (5 mL and 3 mL of levobubivacaine 0.5%, respectively). The detection thresholds for cold/warm sensations and cold/heat pain were established using thermal QST on the C4-C7 dermatomes before local anesthetic infiltration and at 0.5, 6, 10, and 24 hours thereafter. Our primary outcome was the time course of QST thresholds for the different neurosensitive/nociceptive modalities. As secondary and tertiary outcomes, we evaluated the degree of motor block and the time to first administration of rescue analgesics. Results: We randomized 20 patients. There were no significant differences in the detection thresholds for the neurosensitive/nociceptive modalities, motor block, or timing for rescue analgesics between the groups (P = 0.15-0.94). All patients with CPVB + SGB exhibited Horner's signs, whereas patients in the CPVB group did not exhibit these signs; however, this does not exclude sympathetic block. Conclusions: We were unable to demonstrate any analgesic benefit of CPVB + SGB in arthroscopic shoulder surgery. It is therefore not unreasonable to suppose that pain from soft tissue injuries without bony lesions is transmitted mainly by somatic nerves with no or only minimal involvement of the sympathetic nervous system.

Thermal quantitative sensory testing to assess the sensory effects of three local anesthetic solutions in a randomized trial of interscalene blockade for shoulder surgery.

PURPOSE: This study investigated whether quantitative sensory testing (QST) with thermal stimulations can quantitatively measure the characteristics of an ultrasound-guided interscalene brachial plexus block (US-ISB). METHODS: This was a prospective randomized trial in patients scheduled for arthroscopic shoulder surgery under general anesthesia and US-ISB. Participants and observers were blinded for the study. We assigned the study participants to one of three groups: 0.5% levobupivacaine 15 mL, 0.5% levobupivacaine 15 mL with 1:200,000 epinephrine, and 0.75% ropivacaine 15 mL. We performed thermal QST within dermatomes C4, C5, C6, and C7 before infiltration and 30 min, six hours, ten hours, and 24 hr after performing the US-ISB. In addition, we used QST, a semi-objective quantitative testing method, to measure the onset, intensity, duration, extent, and functional recovery of the sensory block. We also measured detection thresholds for cold/warm sensations and cold/heat pain. RESULTS: Detection thresholds for all thermal sensations within the ipsilateral C4, C5, C6, and C7 dermatomes increased rapidly (indicating the development of a hypoesthetic state) and reached a steady state after 30 min. This lasted for approximately ten hours and returned to normal detection thresholds by 24 hr. There were no differences detected between the three groups at 24 hr when we compared warm sensation thresholds on one dermatome. Visual inspection of the pooled results per dermatome suggests the ability of QST to detect clinically relevant differences in block intensity per dermatome. CONCLUSIONS: Quantitative sensory testing can be useful as a method for detecting the presence and characteristics of regional anesthesia-induced sensory block and may be used for the evaluation of clinical protocols. The three local anesthetic solutions exhibited a similar anesthetic effect. The results support the use of QST to assess block characteristics quantitatively under clinical research conditions. This trial was registered at Clinicaltrals.gov, NCT02271867.