Effect of Spinal Ketorolac on Mechanical Hypersensitivity After a Total Hip Replacement

Effect of Intrathecal Ketorolac on Mechanical Hypersensitivity After Total Hip Arthroplasty

Chronic pain in patients following total hip replacement seems to be a significant problem. Previous research has shown that more effective pain management in the early postoperative period may decrease the incidence of the development of chronic pain states.

This study will evaluate whether ketorolac (a non steroidal anti-inflammatory drug) given into the spinal fluid before surgery will reduce the area of sensitivity (or pain to light touch) following surgery. Patients will be monitored during their postoperative hospital stay and then contacted by telephone at 8 weeks and 6 months after surgery and questioned about any pain they are having at their surgical site. Patients that are still experiencing pain at 6 months will be asked to return to the medical center for the study staff to assess their pain or sensitivity at the surgical site.

Surgery results in hypersensitivity to mechanical stimuli surrounding the wound and in a subset of patients, also results in chronic pain. The purpose of the study is to test whether intrathecal ketorolac, by selectively and effectively blocking cyclooxygenase in the spinal cord, will reduce hypersensitivity surrounding the surgical wound in patients with high risk for developing chronic pain after surgery. We have chosen to study patients having total hip arthroplasty (THA) because chronic pain seems to be a significant problem after surgery. We will sample cerebrospinal fluid (CSF) prior to injection of the study medication for subsequent prostaglandin E2 (PGE2) analysis in each patient. We will also assess each patient at 48 hours after their surgery for hypersensitivity at their surgical site.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status I, II, III
• > Age 18
• Primary unilateral total hip arthroplasty under spinal anesthesia

Exclusion Criteria:

• Known allergy to study medication
• Weight > 300 pounds
• Obstructive sleep apnea
• Patients with severe renal (kidney) or hepatic (liver) disease, allergy to ketorolac, amino amide local anesthetic, or contraindications to spinal anesthesia
• Patients on dialysis for kidney failure or patients that are jaundice or have a diagnosis of liver failure
• Patients routinely taking narcotic pain medications for pain other than their primary hip pain
• Patients that are taking Lyrica (pregabalin) or Gabapentin (neurontin) for the treatment of seizures