Efficacy and Safety Study of Dexmedetomidine as an Additive to Local Anesthetics in Shoulder Surgery

Peripheral nerve blocks are used throughout the world in lieu of general anesthesia and, more commonly, to provide analgesia and opioid sparing in the postoperative course. Long acting local anesthetics, such as ropivacaine, can provide analgesia for 11.5 ± 5 hours. This leads to many patients reporting their first pain in the evening and nighttime hours when access to healthcare providers and support is most limited. A number of additives to local anesthetics have been studied in humans with limited success. Recent work by a group in Michigan found a dose dependent increase in the duration of analgesia to a thermal stimulus when dexmedetomidine was added to ropivacaine for sciatic nerve blocks in rat.

The goal of the study is to investigate the safety and efficacy of dexmedetomidine added to ropivacaine for interscalene brachial plexus nerve block for shoulder surgery in humans. Provided the initial safety can be established, the trial will continue to evaluate secondary goals including the duration of analgesia, onset of sensory and motor blockade, and opioid-induced side effects. Tertiary outcomes will include subject satisfaction.

Inclusion criteria

• ASA I-III adult subjects
• Age 18-75
• Elective shoulder surgery
• Plan for interscalene brachial plexus block combined with general anesthesia
• Interscalene block
• Willingness to be contacted postoperatively for brief (5-10min) phone call questionnaires
• Written informed consent

Exclusion criteria

• Age < 18
• Age > 75
• Inability to understand protocol due to language barrier; difficulty with German language
• Chronic pain requiring daily opioids > 15 mg oral morphine equivalents (equals oral usage of > 10 mg oxycodone/daily; > 5 mg methadone/day; > 4 mg hydromorphone/day)
• Moderate (NRS pain score > 5) daily average pain
• Daily use of gabapentin, pregabalin, tricyclic antidepressant, serotonin- norepinephrine reuptake inhibitor, tramadol
• Hypersensitivity to amide local anesthetics
• History of hypersensitivity or allergic reaction to clonidine or dexmedetomidine
• Uncontrolled anxiety
• Schizophrenia or bipolar disorder
• Preexisting nerve damage (sensory or motor) in the extremity to be blocked
• Peripheral neuropathy
• Significant cardiovascular disease (second (Mobitz II type) or third degree heart block, congestive heart failure, chronic heart failure NYHA III-IV, symptomatic coronary artery disease CSS III-IV)
• BMI > 35
• Uncontrolled diabetes (blood sugar > 250 recorded in last 30 days or HbA1c > 7.5%)
• Chronic clonidine therapy (clonidine patch - Catapres or clonidine tablets)
• Hepatic Impairment (CHILD B or higher)
• Renal Impairment (creatinin > 2.0 mg/dl)
• Ongoing drug or alcohol abuse
• Pregnancy
• Prisoners