The investigators will conduct a prospective, randomized, double-blinded study using an axillary brachial plexus block in patients undergoing elective surgery of the distal forearm and hand to characterize and describe the pharmacokinetics of bupivacaine associated with perineural dexamethasone. The pharmacokinetic analysis will be performed by measuring bupivacaine plasma levels at different time intervals after the blockade (15, 30, 45, 60, and 90 minutes), allowing comparison between 2 different groups: Bupivacaine (B) and Bupivacaine-dexamethasone (BD). Thus, the hypothesis is that plasma levels of bupivacaine during the first 90 minutes after a blockade are lower in the presence of perineural dexamethasone, suggesting a decrease, at least initially, in systemic absorption from the injection site.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
20
Patients will receive a total volume of 30 ml of bupivacaine 0.5% in an axillary block with a double puncture.
Patients will receive a total volume of 30 ml of bupivacaine 0.5% with Dexamethasone 4 mg in an axillary block with a double puncture.
Hospital Clínico Universidad de Chile
Santiago, Metropolitan, Chile
Maximum plasma concentration (Cmax) of bupivacaine
Maximum plasmatic level of bupivacaine
Time frame: 0 to 90 minutes after the ending time of local anesthetic injection
Plasmatic concentration of bupivacaine at 15 minutes
Plasmatic level of bupivacaine 15 minutes after local anesthetic injection (ng/ml)
Time frame: 15 minutes after the ending time of local anesthetic injection
Plasmatic concentration of bupivacaine at 30 minutes
Plasmatic level of bupivacaine 30 minutes after local anesthetic injection (ng/ml)
Time frame: 30 minutes after the ending time of local anesthetic injection
Plasmatic concentration of bupivacaine at 45 minutes
Plasmatic level of bupivacaine 45 minutes after local anesthetic injection (ng/ml)
Time frame: 45 minutes after the ending time of local anesthetic injection
Plasmatic concentration of bupivacaine at 60 minutes
Plasmatic level of bupivacaine 60 minutes after local anesthetic injection (ng/ml)
Time frame: 60 minutes after the ending time of local anesthetic injection
Plasmatic concentration of bupivacaine at 90 minutes
Plasmatic level of bupivacaine 90 minutes after local anesthetic injection (ng/ml)
Time frame: 90 minutes after the ending time of local anesthetic injection
Time to obtain the maximum plasma concentration of bupivacaine (Tmax)
Time in minutes in which the maximum plasmatic level of bupivacaine is reached
Time frame: 0 to 90 minutes after the ending time of local anesthetic injection
Area under the curve of plasma concentration versus time at 90 minutes (AUC90)
Area under the curve at 90 minutes
Time frame: 0 to 90 minutes after the ending time of local anesthetic injection
Sensory and motor block score
The sensorimotor block will be assessed every 5 minutes until 30 minutes after the end of local anesthetic injection using a 16-point composite score evaluating sensory and motor block of musculocutaneous, medium, radial, and ulnar nerves. Sensation will be assessed with ice in each nerve territory with a 0 to 2 point scale. 0= no block, patients can feel cold; 1= analgesic block, the patient can feel touch but not cold; 2= anesthetic block, the patient cannot feel cold or touch. The motor function will be assessed for each nerve with a 0 to 2 points scale where 0= no motor block; 1= paresis; 2= paralysis. Successful blocks at 30 minutes correlate with a final score ( sum of all individual sensory and motor scores) of at least 14 points out of 16.
Time frame: 30 minutes after the ending time of local anesthetic injection
Block onset time
Time required to reach a minimal sensorimotor composite score of 14 points out of a maximum of 16 points. The sensorimotor score is described in outcome 9.
Time frame: 30 minutes after the ending time of local anesthetic injection
Incidence of successful block
Percentage of blocks with a minimal sensorimotor composite score of 14 points out of a maximum of 16 points at 30 minutes after the injection
Time frame: 30 minutes after the ending time of local anesthetic injection
Motor block duration
The elapsed period in minutes between the ending time of the local anesthetic injection and the time of return of hand and fingers movement.
Time frame: 48 hours after the ending time of local anesthetic injection
Sensory block duration
The elapsed period in minutes between the ending time of the local anesthetic injection and the time of the return of hand and fingers sensation
Time frame: 48 hours after the ending time of local anesthetic injection
Analgesic block duration
The elapsed period in minutes between the ending time of the local anesthetic injection and the time of the first sensation of pain in the surgical area
Time frame: 48 hours after the ending time of local anesthetic injection
Intensity of pain during block procedure
Evaluated with the Numeric Rating Scale for Pain. This scale is graduated from 0 to 10 points. A 0-point score represents the absence of pain, and a 10-points score represents the worst imaginable pain. Patients will be asked to rate their pain verbally with this scale. The blinded assessor will register the score reported.
Time frame: During the execution of the nerve blockade
Block performance time
Sum of: 1- the acquisition time of the ultrasonographic image. and 2- the time to perform the block itself (from the skin anesthesia to the end of local anesthetic injection)
Time frame: From the skin anesthesia to the end of local anesthetic injection
Incidence of nerve block side effects
Determined by the presence of paresthesia, local anesthetic systemic toxicity, vascular puncture after the block.
Time frame: From the skin anesthesia to the end of local anesthetic injection
Persistent neurologic deficit
Presence of persistent sensory or motor postoperative deficit.
Time frame: 7 days after surgery
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