In patients undergoing hip replacement surgery, using a special wound catheter to infuse local anesthetic directly into the hip joint provides significant and lasting improvements in postoperative pain control, reports a study in the February issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).
By stopping pain at the source, continuous wound infusion with local anesthetic produces lower pain scores, reduced morphine use, and less nausea and vomiting, according to the new research. "Moreover, a positive effect on superficial and deep wound pain was still present three months later," write Dr Jose Aguirre and colleagues of Balgrist University Hospital Zurich, Switzerland.
Continuous Wound Infusion Reduces Pain after Hip Surgery
The study included 76 patients undergoing minimally invasive hip arthroplasty surgery. In all patients, a specially designed wound catheter was placed into the hip joint during the operation. In one group, the catheter was used to infuse ropivacaine, a local anesthetic drug, into the joint at the end of the procedure and for 48 hours afterward. The other group received continuous wound infusion with an inactive placebo solution.
Both groups had patient-controlled morphine available for pain relief. The two groups were compared in terms of pain scores and amount of morphine used.
Patients receiving continuous wound infusion with ropivacaine had better pain control during the first 48 hours after surgery, with lower scores for pain at rest and pain with motion. This was reflected by a significant reduction in morphine use, especially on the day after surgery. Overall, patients in the ropivacaine group used 36 percent less morphine than those in the placebo group.
The ropivacaine group also had less postoperative nausea and vomiting -- a common side effect of morphine -- and were more satisfied with their pain management. None of the patients had toxic levels of ropivacaine in their bloodstream.
Continuous wound infusion with ropivacaine reduced pain not only in the days after the operation, but also in subsequent weeks and months. Three months after surgery, patients in the ropivacaine group had lower scores for wound pain, including both superficial and deep pain.
Pain is a significant problem for patients undergoing hip replacement surgery. Instilling local anesthetic directly into the wound is increasingly recognized as an effective part of "multimodal" (combination) approaches to pain control after various types of surgery. The new study is the first to specifically evaluate the effects of continuous wound infusion with modern minimally invasive hip arthroplasty techniques.
The results suggest that continuous wound infusion with ropivacaine significantly improves pain control after hip replacement surgery. What's more, better pain control in the days after surgery may reduce problems with wound pain in the weeks and months after the operation. Dr Aguirre and colleagues suggest further studies to evaluate continuous wound infusion with different kinds of drugs known to affect "central sensitization" to pain.
"Wound catheters are very inexpensive and highly effective," comments Dr. Steven L. Shafer of Columbia University, Editor-in-Chief of Anesthesia & Analgesia. "This is an important advance in providing high quality pain relief with minimal cost."
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