Patients who receive a single-injection nerve block when undergoing surgery for an ankle fracture frequently experience “rebound pain” as the block wears off. According to the results of a study presented at the 2015 annual meeting of the Orthopaedic Trauma Association, use of a continuous infusion of regional anesthetic can not only alleviate rebound pain but also reduce the need for narcotic analgesia following surgery.

According to David Y. Ding, MD, of the Hospital for Joint Diseases, who presented the results, regional anesthesia has been successful in controlling pain in the immediate postoperative period and has a number of advantages over general anesthesia, including avoidance of airway interventions, lower incidence of postoperative nausea and vomiting, and shorter stays in a postanesthesia care unit (PACU).

However, he noted, “Patients who receive a single-injection nerve block will experience significantly increased pain 12 to 24 hours after surgery, compared to patients without blocks. Although rebound pain can be controlled with early narcotic administration, it can cause significant discomfort to the patient and may even result in the patient’s returning to the emergency department for pain control.”

This prospective randomized clinical trial involved 44 patients who underwent open reduction and internal fixation of unstable ankle fractures. Preoperatively, patients were randomized to one of two anesthetic protocols: general anesthesia/sedation with a single-shot peripheral nerve block (SSB group, n = 21) versus general anesthesia/sedation with a continuous peripheral nerve block using a continuous infusion pump (CIP group, n = 23).

Patients were excluded if they were younger than 18 years of age; on chronic opioid medication; or had a history of opioid abuse, a neurologic condition that could interfere with pain sensation, or multiple injuries requiring treatment. The surgeon and anesthesiologist were blinded to the randomization until the day of surgery. Patients did not learn which group they were in until after the surgery.

Operative sedation was given using a combination of midazolam (1–4 mg) and fentanyl (25–100 mcg). Patients in both groups received an ultrasound-guided, popliteal sciatic nerve block. For both groups, 20 mL of 2 percent lidocaine with 1:200,000 epinephrine plus 20 mL of 0.5 percent bupivacaine with 1:300,000 epinephrine was injected around the nerve. Those in the CIP group received an indwelling catheter secured at the skin.

“If a medial incision was necessary for the surgical reduction, we performed a saphenous nerve block using 10 mL of 2 percent lidocaine with 1:200,000 epinephrine,” Dr. Ding explained.

After surgery, patients were taken to the PACU, and patients in the CIP group began receiving a continuous infusion of 0.2 percent ropivacaine through the catheter at a rate of 8 mL/hour with discharge instructions to self-discontinue the catheter 48 hours after surgery. Patients who experienced breakthrough pain in the PACU were treated with intravenous fentanyl and oxycodone/acetaminophen as needed. All patients were discharged home with a prescription for oxycodone/acetaminophen 5/325 mg with instructions to take 1 to 2 tablets every 4 to 6 hours as needed for pain.

Postoperative pain and satisfaction ratings were assessed using the Visual Analog Scale (VAS) prior to discharge from the PACU. Time to discharge and amount of pain medication taken in the PACU were recorded. Additionally, patients were contacted 8, 12, 24, 48, and 72 hours after surgery to assess their pain scale and pain medication intake. Patients were seen for routine postoperative follow-up visits at 2, 6, 12, and 24 weeks after surgery. At these times, patients were assessed for pain, residual neurological symptoms, and signs of infection and satisfaction.

The average total amount of fentanyl received in the PACU was lower in the CIP group (22.8 mcg) compared to the SSB group (44.1 mcg). There was no significant difference in the average number of oxycodone/acetaminophen pills taken before discharge.

In the early postoperative period, mean VAS pain scores were lower in the CIP group at 8, 12, 24, 48, and 72 hours after surgery, but the difference was significant only at 12 hours. Additionally, patients in the CIP group took significantly fewer pain pills in the first 72 hours after surgery when compared to those in the SSB group (mean 14.9 vs. 20.0; P = 0.036). No significant differences were found in the satisfaction ratings between the groups 72 hours postoperatively.

On follow-up, patients in the CIP group reported lower VAS pain scores at 2 and 6 weeks after surgery. However, only the difference at 6 weeks was statistically significant. There were no differences between the groups in terms of reported neurologic symptoms or satisfaction. There were no complications or infections in either group.

“Our results show a significant decrease in the amount of postoperative narcotics required as well as decreased rebound pain when patients undergoing ankle fracture surgery were managed with the sustained-delivery nerve block anesthesia,” Dr. Ding said. “Although no significant differences were noted in side effects between the two groups, reducing the narcotic used postoperatively has been shown to reduce complications such as nausea, vomiting, respiratory depression, ileus, and narcotic-induced hypotension,” he added.

Preventing the rebound
Previous studies have documented the “rebound effect”—a phenomenon that occurs after a single shot of local anesthesia has worn off and before patients reach their oral pain medication equilibrium. Typically, patients are counseled to start taking oral pain medications 1 to 2 hours before the block wears off—ideally when they start regaining sensation in the limb.

“Yet, patients are often reluctant to take narcotics when they are not yet in pain,” Dr. Ding said. “Additionally, the block’s duration is variable and, depending on the time of surgery, may diminish when the patient is sleeping. As a result, initiation of timely oral pain medication may be difficult to manage.”

Continuous peripheral nerve blocks function in multiple ways, decreasing both baseline and dynamic pain, as well as analgesic requirements, Dr. Ding said. “They can also decrease joint inflammation and inflammatory markers, sleep disturbances, other opioid-related side effects, and the incidence of postsurgical chronic pain.

“We did not see any major adverse side effects of the CIP such as infection of the catheter, catheter irritation, and infiltration,” he continued. “The only minor side effect was early catheter removal in eight patients, all around the 24-hour period, primarily due to spontaneous, accidental discontinuation during sleep. Because the catheters had been functioning for 24 hours, we were still able to see the maintenance of regional anesthesia throughout the rebound pain period. Although not the intention of our study, this may indicate that sustained delivery of the regional anesthesia is only necessary for 24 hours. By then, the patient has recovered from the initial insult of the surgery and is well maintained on oral analgesics.”

A limitation of the study was the lack of a catheter control to enable blinding of patients, Dr. Ding said. Although the surgeon and data collectors were blinded to the randomization, patients were aware postoperatively because the single shot group was not discharged with a CIP. “We could have placed an indwelling catheter with sterile normal saline infusion,” said Dr. Ding, “but we did not want to expose patients to the unnecessary additional risks of catheter malfunction or infiltration.”

Coauthors with Dr. Ding are Arthur Manoli III, BS; David K. Galos, MD; Sudheer Jain, MD; and Nirmal C. Tejwani, MD. One or more of the authors reported potential conflicts of interest; visit www.aaos.org/disclosure to learn more.

Terry Stanton is a senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

• Advantages for using regional rather than general anesthesia for ankle fracture surgery include avoidance of airway interventions, lower incidence of postoperative nausea and vomiting, and shortened stays in a postanesthesia care unit.
• The popliteal sciatic nerve block achieves effective initial pain relief but is associated with rebound pain 12 to 24 hours after surgery.
• The study compared patients with ankle fracture receiving only the single nerve block versus those who also received a continuous infusion of anesthetic postoperatively.
• Those with the continuous infusion had significantly less rebound pain and consumed less opioid medication postoperatively.