Continuous Peripheral Nerve Blockade as Postoperative Analgesia for Open Treatment of Calcaneal Fractures

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1 ORIGINAL ARTICLE Continuous Peripheral Nerve Blockade as Postoperative Analgesia for Open Treatment of Calcaneal Fractures Kenneth J. Hunt, MD,* Thomas F. Higgins, MD,* Cory V. Carlston, MD,* Jeffrey R. Swenson, MD,* J. Edward McEachern, MD,* and Timothy C. Beals, MD* Objective: To examine the cost and efficacy of methods of general and regional anesthetic for postoperative pain control after open repair of intra-articular calcaneal fractures. We compared singleinjection popliteal fossa blocks and continuous infusion popliteal fossa blocks with drug delivered through a catheter from an infusion pump (CPNB) to general or spinal anesthetic alone in terms of hospital charges, length of hospital stay, and postoperative oral and intravenous narcotic use, antiemetic use, and safety. Design: Retrospective review. Setting: University Level I regional trauma center and associated orthopaedic surgery center. Patients/Participants: Charts were reviewed for all patients undergoing open treatment of calcaneal fractures during a 9-year period. One hundred six of 203 met study inclusion criteria. Intervention: All patients received either general or spinal anesthetic. Patients additionally received preoperative singleinjection popliteal fossa blocks, CPNB, or no regional block. Outcome Measurements: Data were compared from each group for total hospital cost, length of stay, operating room times, narcotic use, postoperative nausea, and hospital readmission. Eighteen patients from the CPNB group who were discharged within 24 hours of surgery were examined in a subgroup analysis of ambulatory treatment. Results: There were no significant differences between the control group and the two regional anesthesia groups in total hospital cost, length of stay, narcotic use, or antiemetic use. However, subgroup analysis demonstrated that ambulatory CPNB patients had significantly lower total hospital costs and narcotic use compared with the remaining CPNB patients. There were no block-related complications. None of the short-stay patients required urgent medical attention or readmission after discharge. Conclusions: CPNB through an infusion pump may allow patients undergoing open treatment of calcaneal fractures to be safely Accepted for publication July 13, From the Departments of *Orthopaedic Surgery; and Anesthesia, University of Utah, Salt Lake City, UT. The authors have no conflicts of interest as it relates to this study. No research support was received in support of this manuscript. Reprints: Timothy C. Beals, MD, University of Utah, Department of Orthopaedic Surgery, University Orthopaedic Center, 590 Wakara Way, Salt Lake City, UT ( Timothy.beals@hsc.utah.edu). Copyright Ó 2010 by Lippincott Williams & Wilkins discharged within 24 hours with a concomitant decrease in healthcare costs. These data suggest that this method of postoperative pain management might be applied to other patients with major foot and ankle trauma and/or reconstructive procedures and that wider use of continuous peripheral nerve blocks may lead to a reduction in healthcare costs. Key Words: calcaneus fracture, regional anesthesia, cost analysis (J Orthop Trauma 2010;24: ) INTRODUCTION Open treatment of calcaneus fractures can result in significant postoperative pain. 1 The use of single-shot nerve blocks (SSNB) and continuous peripheral nerve block (CPNB) techniques have gained popularity as an adjunct to intraoperative and postoperative pain control in foot and ankle procedures as a result of improvements in injection techniques and simplified infusion systems. These types of peripheral nerve blocks may facilitate earlier hospital discharge, reduce postoperative pain and nausea, and perhaps reduce hospital costs. The issue of hospital charges is becoming increasingly important because rising healthcare costs are projected to present a major challenge for both private and governmental payers in the next several decades. 2 This concern has increased the need for orthopaedic providers to understand the economic impact of various therapies. 3,4 Orthopaedic providers attempt to control costs through various interventions, including shortening the period of postoperative hospitalization. 5,6 For example, retrospective analyses in total knee arthroplasty have demonstrated that CPNB is associated with shorter hospital stays and reduced hospital charges and costs without compromising patient outcomes or increasing morbidity. 6,7 Specialty-focused hospitals have shown superior outcomes with reduced total costs for knee and hip arthroplasty. 8 However, data are needed to determine the influence of peripheral nerve blocks on hospital costs in other orthopaedic subspecialties, including lower extremity trauma and foot and ankle reconstruction. The goal of this retrospective, case control study is to compare the use of CPNB or SSNB with general or spinal anesthesia only in patients undergoing open treatment of intraarticular calcaneal fractures. Primary outcome variables include total hospital costs and length of hospital stay J Orthop Trauma Volume 24, Number 3, March 2010

2 J Orthop Trauma Volume 24, Number 3, March 2010 Postoperative Analgesia for Treating Calcaneal Fractures Secondary outcomes include oral and intravenous narcotic use, antiemetic use, and adverse events related to the block. We hypothesized that the addition of CPNB to the postoperative pain control regimen results in reduced hospital costs, shorter hospital stays, and safe ambulatory stays in appropriate patients compared with SSNB or general or spinal anesthesia alone. PATIENTS AND METHODS This study was approved by the University Institutional Review Board. All patients 18 years of age and older who presented through our emergency department, or to our clinic by referral from an outside institution, and subsequently underwent open treatment for intra-articular fractures of the calcaneus between 1997 and 2006 were eligible. Patients were excluded if they had other extremity injuries that would result in significant postoperative pain, lengthen the hospital stay, or were treated surgically for other injuries during the same hospital stay. All patients who offered a history of chronic regional pain syndrome predating their calcaneal fracture or patients who had evidence of peripheral vascular disease on history or physical examination were also excluded from the study group. All patients underwent open reduction and internal fixation of an intra-articular calcaneal fracture at one of two hospitals at our institution: the university hospital trauma center or the freestanding university orthopaedic center. All procedures were performed by either a fellowship-trained foot and ankle specialist (TCB) or a fellowship-trained orthopaedic traumatologist (TFH). Both surgeons were equally involved in the last 6 years of the treatment period; one surgeon (TCB) performed all included procedures before Similar surgical technique was used by each surgeon performing open reduction and laterally based plate fixation through an open lateral approach. Each surgeon contributed approximately the same number of patients to the overall study group. All patients underwent spinal or general anesthesia at the discretion of the staff anesthesiologist. Patients received no regional anesthesia (control), a single-injection popliteal fossa nerve block (SSNB), or continuous popliteal fossa nerve blockade with an indwelling catheter (CPNB). The decision to use one of these three options was made by the attending anesthesiologist in consultation with the attending surgeon and was based in part on the availability of SSNB or CPNB. Some patients were not offered outpatient blocks based on subjective judgments by the surgeon of patient compliance or cognition. For patients in the SSNB or CPNB group, nerve blocks were placed using ultrasound guidance; the sciatic nerve was identified in the proximal popliteal fossa between the biceps femoris and the semimebranosus/semitendinosus muscles. Under dynamic ultrasound visualization, an 18-gauge, thinwalled needle was advanced into the space between the biceps femoris and semimebranosus/semitendinosus muscles, approximately 1.0 cm medial to the sciatic nerve. The injection of local anesthetic was observed in real time to document adequate distribution around the nerve. In CPNB patients, catheters were then placed through the 18-gauge thin-walled needle after the initial injection of 30 ml 0.5% preservativefree bupivicaine with 1:200,000 epinephrine. The catheter was attached to a disposable fixed-rate elastomeric infuser (Baxter Infusor LV; Baxter, Deerfield, IL) filled with a volume of 250 ml of plain, preservative-free 0.25% bupivicaine set to infuse at 5 ml/hr. The connections and patency of the catheter were assessed by hand injection at the time the catheter was attached. Patients with CPNB were educated regarding the possibility of increased sensation after the transition phase between the initial bolus of 20 to 30 ml 0.5% bupivicaine and subsequent infusion of a lower concentration of a more dilute solution in the CPNB (5 ml/hr of 0.25% bupivicaine). A subset of 18 patients in the CPNB group were discharged from the hospital within 24 hours of admission with an ambulatory catheter and infuser (this fourth group is hereafter referred to as AMB) provided that they met appropriate discharge criteria as described in the modified Aldrete score. 9 Catheters were removed in CPNB patients after 48 hours. This was done either in the hospital by a healthcare professional or at home by a friend or family member who had received instructions from the block team. All ambulatory catheter patients were given telephone access to our staff anesthesiologist (JRS) for any questions or concerns. Over half of control group patients were treated before 2000, because this is the time period when peripheral blocks became widely available at our institution as an adjunct to intraoperative and postoperative analgesia. Ninety-one percent of surgical cases included in our analysis (91%) were performed at the university trauma center with the remainder occurring at the orthopaedic center. Hospital and billing records were obtained and each patient s hospital stay was evaluated for length of hospital stay and total hospital charges (inflation adjusted to 2006 dollars). The hospital chargemaster was used to reprice all cases to the 2006 level using the then-current costs for each aspect of the case. For example, operating room time was repriced to the 2006 per minute costs and implants at the then-current costs. If aggregate costs were used because detail data were not available, then the hospitalwide year-on-year increase in costs as a percentage of total was used to adjust to 2006 data. Intravenous and oral narcotic use through postoperative Day 1 was acquired from each patient s medication record and converted to morphine equivalents for analysis using accepted conversion standards from the pharmacology and anesthesia literature. 10,11 Postoperative nausea (estimated by antiemetic use, also recorded through postoperative Day 1, number of urgent visits or readmissions within 48 hours of discharge, and nerve block complications were also recorded. Surgeon professional fees were not included in our analysis because they were comparable for all patients. Although patients in the CPNB and SSNB groups had minor additional anesthesia professional fees for block administration, anesthesia professional fees were likewise excluded, because the additional amounts were small and inconsistently billed. Statistical Methods and Data Analysis Sample size calculations were derived by power analysis (alpha level 0.05, power of 0.8) based on the primary hypothesis that administration of CPNB would be associated with decreased hospitalization costs compared with SSNB or general or spinal anesthesia alone. Normality of distribution q 2010 Lippincott Williams & Wilkins 149

3 Hunt et al J Orthop Trauma Volume 24, Number 3, March 2010 was determined using commercially available software (Version 6.0; StatView, Cary, NC). Differences between groups were determined using a single-tailed analysis of variance test. A P value of less than 0.05 was considered statistically significant. In addition to statistical tests of the three groups, we performed a subgroup analysis separating out the AMB group. Ambulatory and 24-hour discharges were not attempted until the surgeons and anesthesiologists had become very comfortable with outpatient CPNBs; thus, the majority of patients in the AMB group were treated in the latter part of the study. The purpose of this subgroup analysis was to assess the potential cost savings and effectiveness of the short stay (outpatient or less than 24-hour stay) treatment of these injuries with SSNB or CPNB. The AMB subgroup was compared with the remaining groups both as part of the CPNB and as a separate group. Single-tailed analysis of variance was used for this subgroup comparison analysis as well with the parameters outlined previously. RESULTS A total of 203 patients underwent open treatment of a calcaneus fracture during the study period with 106 meeting our inclusion criteria. The majority of those excluded were multiple trauma patients with other serious injuries that precluded mobilization in a manner that would allow proper comparison and testing of the fundamental hypotheses. The control group included 17 patients, the SSNB group included 27 patients, and the CPNB included 62 patients. On subgroup analysis, the AMB group included 18 patients from the CPNB group. Nine of the AMB patients underwent surgery at our orthopaedic center, and nine were treated at the university hospital. There were no differences in demographic variables among the three groups or between the AMB subgroup and the remaining groups (Table 1). Total Hospital Charges There was no difference in total hospital charges among the three groups. However, on subgroup analysis, the ambulatory catheter patients had significantly lower total hospital charges compared with the other groups (Fig. 1). Total hospital charges for the nine ambulatory catheter patients who underwent surgery at the orthopaedic center were significantly lower than average charges for all of the CPNB patients undergoing surgery at the university hospital (P, 0.05). However, when comparing these nine patients only with the nine AMB patients treated at the university hospital, there was TABLE 1. Patient Demographic Variables* Control SSNB CPNB Patients Age Sex (male/female) 15/2 24/3 51/9 *There were no statistically significant differences between groups with respect to age or sex. SSNB, single-shot nerve block; CPNB, continuous peripheral nerve block. no significant difference in total charges between the two facilities. Length of Stay The CPNB group showed a shorter length of hospital stay compared with control and SSNB patients, but this difference was not statistically significant. On subgroup analysis, AMB patients had significantly shorter stays than each of the other groups. There were no significant differences in hospital stay when comparing CPNB or SSNB with control subjects (Fig. 2). Operating Room Times Total time in the operating room was significantly higher in the CPNB group compared with control subjects with a trend toward higher times compared with the SSNB group (Fig. 3A). On subgroup analysis, the CPNB group excluding AMB patients still experienced significantly longer operative times than all other groups (Fig. 3B). Narcotic Use Patients from the CPNB group used significantly less intravenous narcotics compared with controls and SSNB patients; however, there were no differences in oral narcotic use among the three groups (Fig. 4A). On subgroup analysis, both the ambulatory catheter group and the CPNB group used significantly less intravenous narcotics compared with the other groups, and the ambulatory catheter patients used significantly less oral narcotics than all other groups. The CPNB and SSNB groups used more oral narcotics than both control subjects and AMB patients, although neither difference was statistically significant (Fig. 4B). Postoperative Nausea There was no significant difference in antiemetic use among the three treatment groups. Hospital Readmission None of the patients in the ambulatory catheter group required urgent medical attention or readmission after discharge. There were no complications with any of the blocks administered to patients in the SSNB, CPNB, or AMB groups. DISCUSSION Pain management after calcaneus fracture and calcaneus fracture repair is a challenging problem for treating physicians. This series tracks the evolution at our institution in perioperative pain management for patients undergoing open treatment for a calcaneus fracture. The surgical method of care remained essentially unchanged during this period of time. All of the patients in this cohort underwent open surgical repair of calcaneal fractures; patients treated with percutaneous or limited open approaches were not included in our analysis. This study aims to examine the impact of changes in the perioperative pain management on costs and postoperative care. We found no differences in total hospital charges comparing CPNB with SSNB and control subjects. However, hospital charges were reduced by 30% in ambulatory catheter q 2010 Lippincott Williams & Wilkins

4 J Orthop Trauma Volume 24, Number 3, March 2010 Postoperative Analgesia for Treating Calcaneal Fractures FIGURE 1. Total hospital charges. Amounts are inflation adjusted to 2006 dollars. The asterisk indicates significant difference between ambulatory catheter group and all other groups (P, 0.05). No significant differences were found between the other groups. patients compared with control subjects. As our methods evolved, the use of CPNB through an infusion pump allowed selected patients undergoing open treatment of calcaneal fractures to be safely discharged to home within 24 hours of hospital admission. Length of hospital stay was reduced with use of CPNB. Both intravenous and oral narcotic use on the first postoperative day were also reduced in ambulatory catheter patients. Ambulatory CPNB may apply to treatment of patients with other major foot and ankle trauma and/or reconstructive procedures with substantial reduction in hospital costs. Cost Reduction With Continuous Peripheral Nerve Block In their retrospective analysis of 20 patients who underwent total knee arthroplasty with the use of ambulatory CPNB, Ilfeld et al 6 showed a 34% decrease in hospital costs for patients discharged home on postoperative Day 1 compared with their historic controls (average of 4-day hospital stay). This meant a savings of more than $2600 per patient. They estimated that almost two thirds of the savings came from hospital room and board costs. 6 This is comparable to our findings of a 30% reduction in hospital charges with the use of ambulatory CPNB. We also noted a 63% reduction in hospital room and board charges with AMB patients compared with control subjects and a 25% reduction in room and board charges in the nonambulatory CPNB group compared with control subjects. Therefore, one would expect overall charges to be lower for CPNB patients. However, the charges associated with increased operating room time for the catheter placement, especially early in the CPNB group, likely offset the reduced inpatient costs, yielding no significant difference in total hospital charges between the CPNB group and control subjects. On an issue related to total costs, the CPNB group had a shorter length of hospital stay compared with control and SSNB patients, but this difference failed to achieve statistical significance (P = 0.06). Perhaps as we get larger sample numbers, this difference will reveal itself more definitively. The Impact of a Regional Anesthesia Service During the course of this study, the department of anesthesia at our institution developed a regional block service that was not present in the earliest part of the study. This addition allowed patients to undergo a block in a separate FIGURE 2. Length of hospital stay reported in number of days. The asterisk indicates significant difference between ambulatory catheter group and all other groups (P, 0.05). There were no other significant differences between groups. The continuous peripheral nerve block (CPNB) group showed a trend toward shorter length of stay compared with the single-shot nerve block (SSNB) group and control subjects (P, 0.06). q 2010 Lippincott Williams & Wilkins 151

5 Hunt et al J Orthop Trauma Volume 24, Number 3, March 2010 FIGURE 3. Operating room time reported in minutes. (A) Group analysis. The asterisk indicates significant difference between continuous peripheral nerve block (CPNB) and control subjects (P, 0.05). (B) Subgroup analysis. The asterisk indicates significant difference between CPNB and all other) groups (P, 0.05). block room before being transported to the operating room. Eventually, we began sending appropriate patients home with an indwelling catheter with instructions on how to safely remove it at the appropriate time. Before the regional block team began placing the catheters in the block room, indwelling catheters had been placed in the operating room by the anesthesia staff. This likely explains the prolonged operating room times in CPNB inpatients compared with CPNB ambulatory patients, all of whom received their blocks before transport to the operating room. Given that 37.5% of total hospital costs in our study were from operating room charges, the development of a regional anesthesia service is at least partially responsible for the reduction in the hospital costs in the AMB group by removing the time associated with block placement from the operating room time. As our perioperative pain regimen evolved throughout the time period of this study, it remains important to understand how the mechanics of treatment affected the cost. The initial learning curve of regional anesthesia may make the intergroup differences less notable than were anticipated. However, the current methodology (ie, the progression of our protocol to include ambulatory CPNB and limited use of inhalational gases) demonstrates the significant reduction in costs that we anticipated. It is important to note that the transition to this safe, cost-reducing method took several years to attain. Furthermore, many of the patients in the CPNB group who were treated earlier in the study period were administered blocks by anesthesia staff with a broad range of experience. The wide variation in narcotic requirements in these patients may be attributed to some variability in the accuracy of block placement and effectiveness. Transition of Care Open treatment of calcaneal fractures provides a unique model for fracture care financial analysis because the majority of definitive procedures often occur weeks after the initial injury and hospitalization, taking place during a separate hospital stay. This allowed us to separate out costs tied to the initial hospitalization and associated injuries. It may be reasonable to assume that the primary factor extending q 2010 Lippincott Williams & Wilkins

6 J Orthop Trauma Volume 24, Number 3, March 2010 Postoperative Analgesia for Treating Calcaneal Fractures FIGURE 4. Narcotic use through 36 hours. Reported in morphine equivalents. (A) Group analysis. The continuous peripheral nerve block (CPNB) group used significantly fewer intravenous narcotics compared with the other groups (P, 0.05). (B) Subgroup analysis. Both the ambulatory catheter group and the CPNB groups used significantly fewer intravenous narcotics compared with the other groups (P, 0.05). previous hospital stays after open reduction and internal fixation of the calcaneus was poor pain control and resulting delayed mobilization. The improved pain control provided by CPNB allows patients a more rapid transition to care at home by family members, reducing costs of inpatient care. Our data demonstrate that there is no substantial increase in readmissions or postoperative complications in patients discharged with CPNB. The potential for complications associated with swelling and noncompliance by treating calcaneus fractures on an outpatient basis was not taken lightly by the senior surgeons. Those patients selected for ambulatory treatment were carefully chosen and do not represent a randomized crosssection of those patients undergoing calcaneal fracture open reduction and internal fixation. There is an openly acknowledged selection bias on the part of the operating surgeons, because some patients were not offered the possibility of ambulatory treatment for their own protection. The Effectiveness of Continuous Peripheral Nerve Block Various CPNB techniques are being used to treat patients undergoing painful surgical procedures to the lower extremity A recent meta-analysis of 19 clinical trials 18 that included 603 patients demonstrated that CPNB provided superior postoperative analgesia compared with opioids with fewer opioid-related side effects (nausea, vomiting, sedation, pruritis, and so on). Consistent with previous studies, the present study demonstrates a significant reduction in intravenous narcotic use in CPNB patients compared with control subjects and those with SSNB. However, use of oral narcotics was similar among the three treatment groups. The early protocol for both control and SSNB patients included intravenous narcotics through patient-controlled analgesia with few prescribed oral agents until the time of discharge. However, the protocol changed with CPNB to include oral q 2010 Lippincott Williams & Wilkins 153

7 Hunt et al J Orthop Trauma Volume 24, Number 3, March 2010 narcotics with intravenous narcotics for breakthrough pain only. The consumption of oral narcotics in the present study included the period of time after the catheter was discontinued in CPNB patients, but not AMB patients. This may account for the similarity in oral narcotic use among the three groups. We were unable to accurately determine oral narcotic use in patients after discharge. Logically, the remarkable reduction in oral and intravenous narcotic use in AMB patients was in part the result of their short hospital stays. It should be noted that our methodology was insufficient to determine the number of oral narcotic pills used after hospital discharge; a significant difference in the oral dose used may exist between groups. Safety and Complications of Nerve Blocks The introduction of continuous regional anesthetic infusion through mechanical and electronic delivery systems have allowed patients to be discharged from the hospital with the catheter in place, safely increasing the duration of pain control. 12,13,19,20 In their study of 224 patients discharged with popliteal fossa catheters for ambulatory CPNB after lower extremity procedures, Swenson et al 12 reported two nerve injuries (0.8%) and only five interventions (2.2%) for patient education (one), equipment malfunction (one), or inadequate pain control (three). Both nerve injuries resolved completely within 6 weeks and were managed during regular clinic hours. 12 Grant et al 20 reported on 228 patients who underwent CPNB for ambulatory surgery, none of whom developed neurologic complications. Zaric et al 21 also reported no adverse events associated with a continuous nerve block in 63 patients undergoing foot surgery. None of the patients in our study receiving CPNB through a popliteal fossa catheter had complications associated with the nerve block. Potential Study Limitations The evolution of care over the course of this study made the comparison of these two groups possible. The transition of care techniques over the course of this study is graphically illustrated in Figure 5. This change over time does create two groups that are essentially chronologically separate. However, the injury patterns, operative techniques, and other aspects of these cases were essentially unchanged over this time period, which suggests that these comparisons should be valid. Certainly a prospectively randomized trial would be more conclusive, but the clinical experience of the senior surgeons over the last decade would no longer permit them to randomize patients into a general anesthetic alone group. However, a prospectively controlled evaluation of patients treated with our current protocol may further elucidate findings on clinical and functional outcomes, pain medication use, and patient satisfaction with the anesthetic technique. The selection bias inherent in judging some patients candidates for ambulatory treatment has been acknowledged. Notably, these decisions were completely independent of funding status and based more on assumptions about cognition, compliance, and assistance available at home. Oral narcotic use was tracked only for the first day, and a longer recording period would be ideal. However, attempts to accurately record the use of outpatient narcotics would be fraught with doubt and imprecision. We opted to sacrifice some recorded length of treatment in exchange for accurate and verifiable data. CONCLUSION Continuous popliteal fossa blockade is safe and valuable adjunct to the postoperative pain control regimen in patients undergoing operative treatment for calcaneal fractures. Although we did not identify differences in total hospital charges with the use of continuous nerve blocks, there was a significant reduction in total hospital charges as we transitioned to ambulatory discharges. This method allowed appropriate patients to be safely discharged within 24 hours of FIGURE 5. Type of regional anesthesia used tracked over the time course of the study q 2010 Lippincott Williams & Wilkins

8 J Orthop Trauma Volume 24, Number 3, March 2010 Postoperative Analgesia for Treating Calcaneal Fractures surgery. Our series had no readmissions or major early complications in ambulatory CPNB patients. This novel practice reduced hospital charges by 30%, or $4000 per patient compared with control subjects. The safe and effective use of CPNBs for appropriate patients may lead to a substantial reduction in overall medical costs. Further investigation into patient outcomes and satisfaction are needed. REFERENCES 1. Cooper J, Benirschke S, Sangeorzan B, et al. Sciatic nerve blockade improves early postoperative analgesia after open repair of calcaneus fractures. J Orthop Trauma. 2004;18: Orszag PR, Ellis P. Addressing rising health care costs a view from the Congressional Budget Office. N Engl J Med. 2007;357: Brauer CA, Rosen AB, Olchanski NV, et al. Cost utility analyses in orthopaedic surgery. J Bone Joint Surg Am. 2005;87: Soohoo NF, Sharifi H, Kominski G, et al. Cost-effectiveness analysis of unicompartmental knee arthroplasty as an alternative to total knee arthroplasty for unicompartmental osteoarthritis. J Bone Joint Surg Am. 2006;88: Munin MC, Rudy TE, Glynn NW, et al. Early inpatient rehabilitation after elective hip and knee arthroplasty. JAMA. 1998;279: Ilfeld BM, Mariano ER, Williams BA, et al. Hospitalization costs of total knee arthroplasty with a continuous femoral nerve block provided only in the hospital versus on an ambulatory basis: a retrospective, case control, cost-minimization analysis. Reg Anesth Pain Med. 2007;32: Ilfeld BM, Gearen PF, Enneking FK, et al. Total knee arthroplasty as an overnight-stay procedure using continuous femoral nerve blocks at home: a prospective feasibility study. Anesth Analg. 2006;102: Cram P, Vaughan-Sarrazin MS, Wolf B, et al. A comparison of total hip and knee replacement in specialty and general hospitals. J Bone Joint Surg Am. 2007;89: Awad IT, Chung F. Factors affecting recovery and discharge following ambulatory surgery. Can J Anaesth. 2006;53: Nissen LM, Tett SE, Cramond T, et al. Opioid analgesic prescribing and use an audit of analgesic prescribing by general practitioners and The Multidisciplinary Pain Centre at Royal Brisbane Hospital. Br J Clin Pharmacol. 2001;52: McCaffery M, Pasero C. Pain: Clinical Manual. St. Louis: Mosby; Swenson J, Bay N, Loose E, et al. Outpatient management of continuous peripheral nerve catheters placed using ultrasound guidance: an experience in 620 patients. Anesth Analg. 2006;103: Ilfeld B, Morey T, Wang R, et al. Continuous popliteal sciatic nerve block for postoperative pain control at home. Anesthesiology. 2002;97: Klein S, Greengrass R, Gleason D, et al. Major ambulatory surgery with continuous regional anesthesia and a disposable infusion pump. Anesthesiology. 1999;91: Klein S, Grant S, Greengrass R, et al. Interscalene brachial plexus block with a continuous catheter insertion system and a disposable infusion pump. Anesth Analg. 2000;91: Klein S, Nielsen K, Martin A, et al. Interscalene brachial plexus block with continuous intraarticular infusion of ropivacaine. Anesth Analg. 2001;93: White P, Issioui T, Skrivanek G, et al. The use of a continuous popliteal sciatic nerve block after surgery involving the foot and ankle: does it improve the quality of recovery? Anesth Analg. 2003;97: Richman JM, Liu SS, Courpas G, et al. Does continuous peripheral nerve block provide superior pain control to opioids? A meta-analysis. Anesth Analg. 2006;102: Chelly JE, Delaunay L, Williams B, et al. Outpatient lower extremity infusions. Best Pract Res Clin Anaesthesiol. 2002;16: Grant SA, Nielsen KC, Greengrass RA, et al. Continuous peripheral nerve block for ambulatory surgery. Reg Anesth Pain Med. 2001;26: Zaric D, Boysen K, Christiansen J, et al. Continuous popliteal sciatic nerve block for outpatient foot surgery a randomized, controlled trial. Acta Anaesthesiol Scand. 2004;48: q 2010 Lippincott Williams & Wilkins 155