Dexametasone Versus Dexametasone Plus Dexmedetomidine in Nerve Blocks

A Randomized Comparison Between Perineural Dexamethasone and Perineural Mixture of Dexamethasone-Dexmedetomidine as Adjuvants for Ultrasound-Guided Infraclavicular Block

This study will compare perineural dexamethasone 2mg and perineural mixture of dexamethasone 2mg plus dexmedetomidine 50mcg DX plus DXD as adjuvants to local anesthetics for ultrasound-guided infraclavicular brachial plexus blocks (ICBs). The protocol is designed as a superiority trial and hypothesizes that the mixture of both drugs results in longer block duration. Furthermore, since analgesic and sensory duration can be influenced by the intake of pain medications and surgical trauma to small cutaneous nerves, respectively, motor block duration was selected as the main outcome to better target the action of both adjuvants on the brachial plexus.

With the approval of Ethics Committee of the Hospital Clínico Universidad de Chile, a total of 50 patients undergoing upper extremity surgery (elbow and below) will be recruited. Recruitment will be carried out by an investigator not involved in patient care in the preoperative clinic or during routine preoperative visits. All ICBs will be supervised by one of the coauthors and conducted preoperatively in an induction room. After skin disinfection and draping, the ICB will be performed with a previously described technique. In both groups, a proven 90% effective volume of 35 mL of local anesthetic solution will be injected. As LA solution, it will be used a mixture of lidocaine 1.0%-bupivacaine 0.25% with epinephrine 5 µ/mL. The injectate will be slowly injected through the block needle. Patients will be randomized to receive the study drug, either PN 2 mg dexamethasone or a combination of PN 2 mg dexamethasone with 50 ug dexmedetomidine, mixed with the above-mentioned LA solution. A research assistant (licensed anesthesiologist) will prepare the local anesthetic solutions and will add the study drug following the randomization order. The operator, patient and investigator assessing the block will be blinded to group allocation. The primary outcome will be the duration of the motor block (defined as the temporal interval between the end of LA injection through the block needle and the return of movement to the hand and fingers) for patients with successful ICBs. Patients will be provided with a data sheet and asked to record the time at which motor function returns. An investigator blinded to group allocation will collect this data sheet in person (inpatients) or by phone (outpatients) on postoperative day 1.

A research assistant (licensed anesthesiologist) will prepare the local anesthetic solutions and will add the study drug following the randomization order. The operator, patient and investigator assessing the block will be blinded to group allocation.

Addition of dexamethasone plus dexmedetomidine to local anesthetics in infraclavicular brachial plexus block

dexamethasone 2 mg will be added to the local anesthetic used to block the cords of the brachial plexus with an infraclavicular approach.

A mixture of dexamethasone 2mg with dexmedetomidine 50mcg will be added to the local anesthetic used to block the cords of the brachial plexus with an infraclavicular approach.

The elapsed period in minutes between the ending time of the local anesthetic injection and the time of return of hand and fingers movement

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

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

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)

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 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 7.

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.

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

Ability to proceed with surgery without the need for intravenous narcotics, general anesthesia, rescue blocks or local anesthesia infiltration by the surgeon

Determined by the presence of paresthesia, local anesthetic systemic toxicity, vascular puncture, Horner syndrome or hoarseness after the block.

Presence of low respiratory rates (lower than 8 breaths per minute) or persistent oxygen requirements (pulse oximetry lower than 90% without supplementary oxygen). The respiratory rate and pulse oximetry are continuously measured intra- and post-operatively (in the post-anesthetic care unit) as a standard of care with a multiparameter monitor. Alarms are set to alert when predetermined levels are reached

Defined as a heart rate lower than 50 beats per minute. The heart rate is continuously measured intra- and post-operatively (in the post-anesthetic care unit) as a standard of care with a multiparameter monitor. Alarms are set to alert when predetermined levels are reached

Mean arterial pressure lower than 60 mmHg. The blood pressure is measured intra- and post-operatively (in the post-anesthetic care unit) as a standard of care with a multiparameter monitor. Alarms are set to alert when predetermined levels are reached

Persistent sedation after surgery using Ramsay sedation scale. The scale has 6 points from 1 to 6. A higher score represents a more sedated patient. 1= anxious, agitated or restless; 2= co-operative, oriented and tranquil; 3= responds to command only; 4= brisk response to light pain or loud auditory stimulus; 5= sluggish response to light pain or loud auditory stimulus; 6= no response.

Presence of persistent sensory or motor postoperative deficit. The patients will be contacted by telephone and inquired about any sensory or motor deficit in the operated extremity.

Inclusion Criteria: American Society of Anesthesiologists classification 1-3 Body mass index between 20 and 35 Exclusion Criteria: Adults who are unable to give their own consent Pre-existing neuropathy (assessed by history and physical examination) Coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4 or prothrombin time ≥ 50) Renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine ≥ 100) Hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases ≥ 100) Allergy to local anesthetics (LAs) Pregnancy Prior surgery in the infraclavicular region Chronic pain syndromes requiring opioid intake at home

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