The Effects of Dexamethasone on the Duration of Sciatic Nerve Blocks

The Effects of Dexamethasone on the Duration of Sciatic Nerve Blocks

Dexamethasone is a commonly used steroid. This medication has been used for many years by physicians for many different indications. Recent articles, multiple case reports, and experience at this institution have indicated that dexamethasone successfully prolongs the effective duration of local anesthetics for regional blocks. This can cause a significant reduction in postoperative pain and the decreased need for postoperative narcotics. Although other adjuncts can be used for prolonging nerve blocks, epinephrine causes local vasoconstriction which can cause ischemia and nerve damage in a large nerve such as the sciatic nerve.Dexamethasone will not cause this problem and yet could prolong the duration of a sciatic nerve block. Therefore, the goal of this study is to prospectively evaluate the effectiveness of dexamethasone, both locally through the nerve block and systemically via IV administration, in prolonging the effective duration of local anesthetics when used in sciatic nerve blocks.

Inclusion Criteria:

• Age 18-80 yrs, male or female subjects.
• Subjects must be scheduled to undergo total knee arthroplasty under general anesthesia with consent for a femoral and sciatic nerve block post operatively for pain control.
• American Society of Anesthesiology Class 1,2,3,or 4.
• Capable of speaking and understanding English sufficiently to provide written informed consent and able to respond when asked.
• Weight > or equal to 60kg.

Exclusion Criteria:

• Any allergies or hypersensitivity to ropivacaine or dexamethasone.
• Subject is on chronic steroids preoperatively for any reason.
• History of chronic pain syndrome (i.e. CPRS, Lumbar radiculopathy).
• History of documented or stated nerve damage or neuropathy to the surgical lower extremity.
• Contraindication to placement of sciatic nerve block.
• Sciatic block placement failure.
• Subject mistakenly receives steroids intraoperatively.