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Departments of *Anesthesiology and Pain Management and
Orthopedic Surgery, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
Address correspondence to Paul F. White, PhD, MD, FANZCA, Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9068. Address e-mail to paul.white{at}utsouthwestern.edu No reprints will be available.
| Abstract |
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IMPLICATIONS: A continuous infusion of bupivacaine 0.25% (versus saline) at the popliteal fossa by using a simple elastomeric pump is an effective method of decreasing postoperative pain, reducing the opioid analgesic requirement, and increasing patient satisfaction with pain management after orthopedic surgery involving the foot and ankle. More importantly, the use of the continuous sciatic nerve block in the popliteal fossa facilitated an earlier discharge after lower extremity surgery.
| Introduction |
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In a recently published study, Ilfeld et al. (12) demonstrated that the use of a continuous popliteal sciatic nerve block with an electronic pump for pain control after lower extremity surgery decreased pain, opioid use, and side effects while improving overall patient satisfaction. Although reports describing the successful use of CPNB techniques for pain control after major orthopedic procedures in the ambulatory setting are very encouraging (912), there have also been reports describing technical difficulties related to pump malfunctions, as well as misplaced, displaced, and obstructed catheters (1315). In the study by Ilfeld et al. (12), 30% of the patients required unscheduled phone calls after discharge. A recent report by Capdevila et al. (16) found that the use of disposable elastomeric pumps for CPNB was associated with fewer technical problems and greater patient satisfaction than electronic pumps. Similarly, comparative evaluation of electronic versus nonelectronic patient-controlled analgesic (PCA) devices demonstrated that the use of a nonelectronic device was associated with fewer programming errors and greater patient and nurse satisfaction (17). Therefore, additional studies are needed to evaluate the effect of CPNB by using nonelectronic devices on clinically important patient outcome variables after orthopedic surgery (e.g., pain scores, hospital discharge, resumption of normal activities, and patient satisfaction).
We designed a prospective, randomized, placebo-controlled study to assess the benefits of a CPNB after surgery involving the foot and ankle by using a disposable, nonelectronic (elastomeric) device. We hypothesized that the use of a continuous popliteal perineural block with bupivacaine 0.25% would improve pain management after these orthopedic procedures. We also examined patient outcome with respect to their satisfaction with pain management and the quality of their recovery.
| Methods |
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In the preoperative holding area, patients completed a baseline pain assessment by using an 11-point verbal rating scale (VRS), with 0 = no pain to 10 = worst pain imaginable. After standard noninvasive monitors were applied, midazolam 12 mg IV and fentanyl 50150 µg IV were administered for sedation and analgesia, respectively, before the nerve block procedure was performed. An attending anesthesiologist (GDS) experienced in performing popliteal nerve blocks for lower extremity surgery performed all the block procedures by using a modification of the original technique of Singelyn et al. (2) as described by Brown (18).
The patients were placed in the prone position, and the popliteal crease was identified. The cephalo-lateral quadrant was identified, and local skin infiltration was performed by using 1% lidocaine at a point 5 cm above the popliteal crease and 1 cm lateral (Fig. 1A). The Stimuplex HNS11 peripheral nerve stimulator (B. Braun Medical Inc., Bethlehem, PA) was connected to an insulated 18-gauge Tuohy needle; an appropriate motor response was initially achieved by using a 1.0-mA current and was then decreased to 0.5 mA. A total of 30 mL of 0.25% bupivacaine was injected through the needle in all cases. A 20-gauge epidural catheter was inserted approximately 23 cm beyond the tip of the needle, and after the needle was removed, the catheter was carefully secured in place (Fig. 1B). Before entering the operating room (OR), patients were assigned to one of two study groups according to a computer-generated randomization number table. The control group received an infusion of 0.9% saline, and the bupivacaine group received an infusion of generic bupivacaine 0.25% at 5 mL/h for up to 48 h after surgery by using a disposable elastomeric pump (C-blocTM PNB system; I-Flow Corp., Lake Forest, CA) connected to the catheter. The pump reservoir contained 270 mL of the study drug (either 0.9% saline or 0.25% bupivacaine) and was filled by a hospital OR pharmacist who was not directly involved in the study.
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On awakening from general anesthesia, patients were transferred to the postanesthesia care unit (PACU). Patients were asked to evaluate the severity of their pain on the 11-point VRS at 1, 2, 4, 8, 24, 48, and 72 h after surgery. Patients with severe pain (VRS scores
6) in the PACU were administered 1- to 2-mg IV bolus doses of morphine and were started on PCA morphine, 1- to 2-mg bolus doses on demand with a 5- to 10-min lockout interval. Patients complaining of moderate pain (VRS >3 and <6) were treated with morphine, 1- to 2-mg IV boluses, until acceptable pain relief was achieved (VRS <3). Patients with VRS pain scores of 23 received an oral opioid-containing analgesic (e.g., hydrocodone [5 mg] and acetaminophen [500 mg]). If patients complained of nausea or experienced repeated episodes of vomiting or retching, they were treated with dolasetron 12.5 mg IV, and if the emetic symptoms persisted, promethazine 6.25-mg IV boluses were administered to a total dose of 25 mg.
Postoperative side effects (e.g., pain, dizziness, nausea, and vomiting) and the requirements for rescue analgesic and antiemetic drugs were recorded, along with the duration of stay in the PACU. If the patients pain was adequately controlled (VRS <3) in the PACU with oral analgesic medication, he or she was considered to be eligible for discharge home on the day of surgery. However, the decision to discharge a patient home after surgery was made by the orthopedic surgeon (JSE) when the patient had achieved specific discharge criteria (e.g., satisfactory pain control with oral analgesics and the ability to mobilize safely with or without assistance devices as assessed by a physical therapist). The patients were carefully instructed in the management of the C-bloc device by an orthopedic nurse before and again after the operation. The catheter was removed by the patients at home when the reservoir was empty.
All patients were asked to record use of oral pain medication and side effects in a diary. Follow-up telephone evaluations were performed by a blinded observer (TI) at 24 h, 48 h, 72 h, and 1 wk after surgery to determine the number of doses of oral analgesic medications consumed after discharge and the occurrence of any side effects (e.g., dizziness, weakness, urinary retention, ileus, and nausea and/or vomiting). Patient satisfaction with postoperative pain management and the quality of the recovery was assessed at 24 h after surgery by using a 100-point VRS, with 1 = poor to 100 = excellent. Patients who rated their satisfaction with pain management as >95 (on the 100-point VRS) were considered to have "complete" satisfaction with their pain control. Finally, the patients also evaluated their maximal (peak) postoperative pain by using the 11-point VRS at 24 h after surgery.
An a priori power analysis suggested that minimum group sizes of 9 would be necessary to detect a 60% reduction in the postoperative pain scores in the bupivacaine group (assuming a mean pain score of 5 and an SD of 2 in the control group), with a power of 0.8 and an
of 0.05. Data analysis was performed with StatView for Windows Version 5.0.1 (SAS Institute, Cary, NC). Normally distributed continuous data were analyzed with one-way analysis of variance, and continuous data not normally distributed were analyzed by a Kruskal-Wallis analysis of variance. Postoperative pain scores were analyzed by a repeated-measures analysis of variance. Means were analyzed with a Type III sum of squares analysis of variance where model = treatment. Categorical data and frequencies were analyzed with the
2 test with Yates continuity correction or Fishers exact test, where appropriate. Data are presented as mean ± SD, median (interquartile range), and numbers or percentages. A P value <0.05 was considered statistically significant.
| Results |
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| Discussion |
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In reviewing the existing literature on the use of CPNB for painful orthopedic procedures involving the distal lower extremity (2,79,12), various research groups have reported improved pain control and opioid-sparing effects. However, many of the early studies involving CPNB techniques failed to include a placebo (control) group. In a well controlled study by Capdevila et al. (3) involving patients undergoing major knee surgery, it was reported that the use of a CPNB technique facilitated the rehabilitation process. The current study involving patients undergoing major foot and ankle surgery also suggested that the use of a CPNB could facilitate the recovery process by allowing some patients to be discharged home on the day of surgery. Importantly, this study confirmed the recent placebo-controlled study by Ilfeld et al. (12), which also demonstrated an improvement in patient satisfaction with postoperative pain management and overall quality of recovery when a CPNB was used after outpatient surgery involving the foot and ankle.
In a case report, Lierz et al. (21) reported the successful infusion of a local anesthetic over six days in an ambulatory patient, without complications. In addition, Tuominen et al. (22) demonstrated that the use of a 0.25% bupivacaine infusion over 24 hours after shoulder surgery provided effective analgesia and was not associated with detectable (>0.05 µg/mL) serum bupivacaine levels. However, the local anesthetic infusion was interrupted in 6 of the 24 patients because of "a failure of catheter function." Although the current study demonstrated that a 0.25% bupivacaine infusion was effective over 48 hours in both inpatients and outpatients (who were discharged home within 24 hours after foot and ankle procedures), valid concerns regarding patient safety, as well as the efficacy of these techniques when used outside the hospital, will need to be addressed in larger-scale studies (1315).
A major concern regarding the use of CPNB relates to the ability to maintain the catheter in the correct position as patients increase their physical activity in the postdischarge period. Problems with catheter displacement were observed after ambulation in the first four patients enrolled in this study (two in each treatment group), necessitating a modification in the procedure used for securing the catheter in the popliteal fossa (Fig. 1B). Inadvertent catheter dislodgements were also reported in 2 of the 30 cases in the recently published study by Ilfeld et al. (12). Other concerns regarding the use of this technique outside the hospital relate to the potential for local anesthetic toxicity and complications secondary to the residual sensory and motor block (14). The lack of high-pressure or occlusion alarms in the disposable nonelectronic elastomeric infusion pump delivery systems may reduce the number of unscheduled phone calls when these devices are used outside the hospital. However, this may also allow catheter occlusions to go undetected with the elastomeric infusion systems. Another potential disadvantage in using a simple constant-rate elastomeric infusion system for CPNB is the inability to adjust the infusion rates or to administer bolus doses of the local anesthetic to treat inadequate analgesia.
It has been suggested that the use of a larger initial dose of bupivacaine (e.g., 3545 mL) in combination with a vasoconstrictor (e.g., epinephrine) and/or other adjuvants (e.g., clonidine or ketorolac) may achieve a comparable opioid-sparing effect and patient satisfaction without the need for a continuous local anesthetic infusion in the postdischarge period. Furthermore, the addition of an on-demand PCA bolus feature (so-called patient-controlled perineural administration of local anesthesia) may have improved the quality of analgesia produced by the CPNB and further reduced the opioid analgesic requirement (13,16). Although Singelyn et al. (5) failed to demonstrate any advantage of a PCA technique over a continuous infusion after total hip arthroplasty procedures, other investigators have reported that supplementing a CPNB with intermittent bolus doses can lead to further improvement in pain control and, thereby, facilitate the rehabilitation process (13).
Although both groups received the same dose of the local anesthetic before the induction of general anesthesia, the administration of the local anesthetic infusion (versus saline) during the operation resulted in an opioid-sparing effect during surgery. These data also suggest that the saline infusion may have diluted the initial 30-mL dose of bupivacaine and reduced its local analgesic efficacy. The additional 812 mL of 0.25% bupivacaine received during the operation appears to have improved the quality of the block. However, the primary benefit of this CPNB technique was related to improved postoperative analgesia, including a reduction in postoperative opioid requirements and opioid-related side effects (e.g., nausea and vomiting). In addition, the CPNB may allow even more painful orthopedic procedures to be performed on an ambulatory (or short-stay) basis in the future. However, further controlled studies are needed to determine the cost benefit of using this local analgesic technique. Although 80% of the patients receiving the local anesthetic infusion reported being aware of a tingling sensation in their lower extremity, it failed to adversely affect their ability to ambulate or their satisfaction with the pain management technique. The tingling sensation may have been related, in part, to postoperative tissue swelling.
This study supports the findings of Singelyn et al. (2), Chelly et al. (8), and Ilfeld et al. (12), in which electronic pumps were used to provide CPNB after foot and/or ankle surgery. The use of a disposable, nonelectronic device may facilitate the use of CPNB outside the hospital. Analogous to the findings of Klein et al. (911), who successfully used disposable pumps to administer continuous local anesthetic infusions after outpatient orthopedic procedures involving both the upper and lower extremities, we observed no complications related to this CPNB technique. Although this nonelectronic delivery system reduced flexibility with respect to dosage changes, it simplified the technique and reduced the risk of programming errors and unscheduled phone calls to respond to alarms (16,17). Further studies are needed to determine the optimal local anesthetic (e.g., lidocaine, bupivacaine, or ropivacaine), concentration (e.g., 0.125%, 0.25% or 0.5% bupivacaine), and infusion rate (e.g., 2.5, 5, or 10 mL/h) for CPNB techniques. Using a CPNB as part of a multimodal analgesic regimen should further enhance both the safety and efficacy of pain management in the ambulatory setting (23).
In conclusion, continuous popliteal nerve block with an elastomeric pump infusing bupivacaine 0.25% at rate of 5 mL/h decreases postoperative pain and the need for opioid analgesic medication and improves patient satisfaction with pain management after painful orthopedic procedures involving the foot and ankle.
| Acknowledgments |
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| References |
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