Discuss the options for postoperative pain control after total hip arthroplasty. Discuss the use of a lumbar plexus block

Discuss the options for postoperative pain control after total hip arthroplasty. Discuss the use of a lumbar plexus block.

Patient-controlled analgesia with morphine sulfate or fentanyl is always a good option in the patient who received general anesthesia. For those who are to receive a spinal anes-thetic, the addition of long-acting morphine can provide up to 24 hours of pain relief. This requires appropriate monitor-ing for delayed respiratory depression. An epidural catheter allows for excellent pain relief with an infusion of an opioid either with or without local anesthetic. The latter should be discontinued prior to the initiation of physical therapy.

Lumbar plexus blocks may be performed to provide postoperative comfort. The lower portion of the lumbar plexus consists of the femoral, obturator, and lateral cuta-neous femoral nerves. The lateral cutaneous femoral nerve provides sensation to the area of the skin incision.

The lumbar plexus block is performed prior to the ini-tiation of anesthesia with the patient in the lateral decubi-tus position, in a fetal posture, and with the side to be blocked facing upward. A 10 cm insulated needle attached to a nerve stimulator is inserted approximately 4 cm lateral to the spinous process of L₄ until movement of the quadri-ceps muscle is elicited. Injection of local anesthetic should only be done when the quadriceps muscle still responds between 0.5 and 1.0 milliamps. Response above a current of 1.0 milliamp may indicate needle placement too far from the plexus and below 0.5 milliamp may represent epidural or intrathecal placement. A test dose of local anesthetic is administered to assess for those possibilities. Either a long-acting local anesthetic, such as ropivacaine with epinephrine, can be injected through the needle or a catheter can be inserted for long-term use.