Summary

Background and objective: Adenosine infusions have been shown to reduce requirements of anaesthetics, to decrease the need for postoperative analgesics and to attenuate hyperaesthesia related to neuropathic pain. We decided to investigate the effects, beneficial or otherwise, of an adenosine infusion administered during surgery. A brachial plexus block was used to produce anaesthesia for the surgery.

Methods: Sixty adults undergoing upper extremity surgery were included in the study. Brachial plexus block was performed via an axillary approach with lidocaine 1.25% and epinephrine 1/200 000 (40 mL). Patients were randomly assigned to two groups. During surgery, saline (control) or adenosine 80 μg kg min was infused intravenously in a double-blind fashion for 1 h. Visual analogue scores every 4 h, analgesic consumption, time to first spontaneous pain sensation, time to first rescue analgesic and adverse effects were noted during the first 24 h.

Results: Vital signs were stable in both groups throughout surgery. During the adenosine infusion, one patient fainted while another complained of palpitations and tightness of the chest; both patients were excluded from further analyses. The time to first sensation of pain was significantly longer in the adenosine group compared to the control group (438 ± 387 vs. 290 ± 227 min, P = 0.02). The time to first rescue analgesic, the visual analogue scale scores and analgesic consumption in the postoperative period were similar.

Conclusions: In patients undergoing surgery with an axillary plexus block, a perioperative adenosine infusion prolongs the duration of postoperative analgesia to some extent. However, the time to first rescue analgesic, total analgesic requirements and pain scores were unchanged; the risk of potentially serious adverse effects is high. This therapy cannot be recommended.

Summary

Background and objective: It has been suggested that dexamethasone potentiates the sensory block produced by bupivacaine when both drugs are loaded in microspheres. The aim of the study was to evaluate the effect of dexamethasone on the brachial plexus block obtained with plain bupivacaine and bupivacaine-loaded microspheres.

Methods: Dexamethasone alone (Group 5) or added to plain bupivacaine (75 mg) with (Groups 3 and 4) and without pH correction (Group 2) was compared with plain bupivacaine (75 mg; Group 1). The effect of a small dose of dexamethasone (0.42 mg) was then evaluated on the brachial plexus block obtained with bupivacaine (750 mg) as bupivacaine-loaded microspheres (Group 6). Dexamethasone was added either in the suspending medium (Group 7) or incorporated with bupivacaine into microspheres (Group 8). The motor block was evaluated in a plexus brachial sheep model.

Results: Dexamethasone alone did not produce any motor block. When added to plain bupivacaine without pH correction, complete motor block could not be obtained. When the pH was corrected, addition of dexamethasone to plain bupivacaine seemed to delay the onset of motor block and did not prolong its duration, and it had no effect on the pharmacokinetics of bupivacaine. With bupivacaine-loaded microspheres, the duration of complete motor block was reduced when a small dose of dexamethasone was added in the suspending medium. However, the duration of motor block was significantly prolonged when dexamethasone was incorporated with bupivacaine into microspheres.

Conclusions: Despite the delayed onset of motor block, the incorporation of dexamethasone in bupivacaine-loaded microspheres dramatically increases the duration of action (700 ± 485–5160 ± 2136 min), which could be clinically relevant when such a drug-delivery system will be available.

Summary

Background and objective: Ropivacaine used for axillary plexus block provides effective motor and sensory blockade. Varying clinical dosage recommendations exist. Increasing the dosage by increasing the concentration showed no improvement in onset. We compared the behaviour of a constant dose of ropivacaine 150 mg diluted in a 30, 40 or 60 mL injection volume for axillary (brachial) plexus block.

Methods: A prospective, randomized, observer-blinded study on patients undergoing elective hand surgery was conducted in a community hospital. Three groups of patients with a constant dose of ropivacaine 150 mg, diluted in 30, 40 or 60 mL NaCl 0.9%, for axillary plexus blockade were compared for onset times of motor and sensory block onset by assessing muscle strength, two-point discrimination and constant-touch sensation.

Results: Increasing the injection volume of ropivacaine 150 mg to 60 mL led to a faster onset of motor block, but not of sensory block, in axillary plexus block, compared with 30 or 40 mL volumes of injection.

Conclusions: The data show that the onset of motor, but not of sensory block, is accelerated by increasing the injection volume to 60 mL using ropivacaine 150 mg for axillary plexus block. This may be useful for a more rapid determination of whether the brachial plexus block is effective. However, when performing surgery in the area of the block, sensory block onset seems more important.