Abstract
Background:
The utility of a femoral nerve block as an adjunct for pain management has been recognized for various surgical techniques but has yet to be examined in the preoperative setting as an adjunct to general anesthesia for improved postoperative pain control in hip arthroscopic surgery.
Purpose:
To evaluate the safety and efficacy of a preoperative femoral nerve block for postoperative pain control in patients undergoing hip arthroscopic surgery.
Study Design:
Cohort study; Level of evidence, 3.
Methods:
A retrospective chart review of 108 consecutive hip arthroscopic surgery cases (in 103 patients) was carried out. All patients underwent arthroscopic surgery under a general anesthetic with or without a preoperative femoral nerve block. Groups were compared with respect to patient sex, age, and body mass index (BMI); physical status classification according to the American Society of Anesthesiologists (ASA); procedure performed; operative time; total intraoperative morphine-equivalent dose; pain scores (0-10 scale) recorded at 0, 15, 30, 45, and 60 minutes postoperatively in the post-anesthesia care unit (PACU); total morphine-equivalent dose in the PACU; presence of nausea or vomiting in the PACU; time to discharge from the PACU; oxycodone consumption in the surgical day care unit (SDCU); and maximal patient-reported pain score in the SDCU.
Results:
Twelve cases were excluded from the analysis for a total of 96 cases (in 92 patients). Forty patients had general anesthesia alone (group A), and 56 patients had a preoperative femoral nerve block before the induction of general anesthesia (group B). There was no significant difference between the groups with regard to sex, age, weight, height, BMI, ASA classification, or type of procedure performed. Patients who received a femoral nerve block also received a significantly lower total intraoperative morphine-equivalent dose than did those patients who did not receive a block. Postoperative patient-reported pain scores were lower at all time points for the femoral nerve block group; however, a statistical significance was seen only at the 60-minute postoperative time point. Patients who did not receive a block had significantly higher morphine-equivalent doses in the PACU. There was no difference in the rates of nausea and vomiting and time to discharge from the PACU between the 2 groups. Oxycodone consumption in the SDCU was similar between the groups, but the femoral nerve block group had significantly lower maximal patient-reported pain scores in the SDCU. Two patients in the general anesthesia group were admitted to the hospital postoperatively because of inadequate postoperative pain control. No complications were noted in any patient with regard to the femoral nerve block.
Conclusion:
A preoperative femoral nerve block is a relatively safe procedure that may decrease the requirement for intraoperative morphine while providing effective postoperative pain control in patients undergoing hip arthroscopic surgery.
Hip arthroscopic surgery is a developing technique that is gaining popularity for its diagnostic and therapeutic role in the management of adolescent and adult hip disorders.3,28,29,41,44 This procedure is frequently associated with considerable postoperative pain, which occurs despite the common practice of injecting the joint and portal entry sites with a local anesthetic at the conclusion of the procedure, combined with the use of perioperative opioids.3,4,30 Narcotic consumption in the setting of increased postoperative pain is often associated with numerous patient-related side effects, including increased costs associated with prolonged hospital stays and unplanned admissions for pain management.12,50 More recently, regional anesthesia has provided an alternative to standard general anesthesia and has been effective in decreasing both postoperative narcotic consumption and the time to discharge after both trauma and elective surgical procedures.10,20,25,33 Prospective trials have illustrated the effectiveness of regional anesthesia and outlined its potential for superior postoperative pain control and recovery from surgery.16,23,51
Pain after hip arthroscopic surgery can arise from a number of different locations and origins, not limited to the arthroscopic portal entry sites, the acetabular labrum after debridement or repair, the femoral neck or acetabular rim after osteochondroplasty, or simply the intraoperative traction used throughout the arthroscopic evaluation of the joint. 30 The hip joint capsule derives innervation from the femoral nerve, obturator nerve, sciatic nerve, nerve to the quadratus femoris, and the superior gluteal nerve. Although this complex network of sensory innervation is well understood, the contribution of each of these nerves to postoperative pain after hip arthroscopic surgery is not well defined. Furthermore, the articular branches of the femoral nerve have been suggested as a predominant contributor to hip joint innervation and are therefore expected to significantly contribute to postoperative pain after hip arthroscopic surgery.7,9
The utility of a femoral nerve block as an adjunct for pain management in knee surgery has been examined extensively. # Its effectiveness has been recognized in both total knee replacement and anterior cruciate ligament reconstruction.32,40 Fournier et al 18 evaluated the effect of a single shot of a femoral nerve block on postoperative analgesia in prosthetic hip surgery and found a short-term benefit during the first few postoperative hours. More recently, Ward et al 48 evaluated the utility of a postoperative femoral nerve block in pain control after hip arthroscopic surgery. In this study, 45 patients who underwent hip arthroscopic surgery were randomized to receive either intravenous narcotics or a femoral nerve block in the post-anesthesia care unit (PACU) for pain scores of ≥7. On the basis of all criteria studied (quality of pain relief, length of stay in the PACU, side effects, and patient satisfaction), the authors determined a femoral nerve block to be an excellent alternative to routine narcotic pain medication in patients undergoing hip arthroscopic surgery.
To our knowledge, no study has examined the utility of a preoperative femoral nerve block in association with general anesthesia for postoperative pain control after hip arthroscopic surgery. The purpose of this study was to evaluate its safety, efficacy, and utility through a number of variables in patients undergoing hip arthroscopic surgery. We hypothesized that patients who received a preoperative femoral nerve block in addition to standard general anesthesia before hip arthroscopic surgery would have decreased intraoperative morphine dosing, decreased postoperative pain scores, decreased morphine consumption in the PACU, an earlier discharge time from the PACU, decreased narcotic consumption in the surgical day care unit (SDCU), and a lower pain rating before discharge from the hospital.
Materials and Methods
After appropriate Research Ethics Board approval from our institution, a retrospective chart review of 108 consecutive hip arthroscopic surgery cases (in 103 patients) at a single academic center between January 26, 2010 and July 9, 2012 was undertaken. The procedures were performed by 1 of 2 orthopaedic surgeons (authors L.M. and D.B.W.) with advanced fellowship training in hip arthroscopic surgery. The single inclusion criterion was the completion of an arthroscopic hip procedure under general anesthesia with or without the addition of a preoperative single-injection femoral nerve block performed under ultrasound guidance before the induction of general anesthesia. Twelve cases were excluded from the analysis for a total of 96 cases (in 92 patients). Reasons for exclusion included the use of additional regional perioperative anesthesia (spinal [n = 2], paravertebral [n = 1], and iliohypogastric [n = 1] blocks), use of a postoperative femoral nerve block (n = 1), and missing or incomplete chart information required for our analysis including details of anesthetic drug doses (n = 4) or missing or incomplete postoperative pain scores (n = 3).
At approximately the midway point of our study period, preoperative femoral nerve blocks were initiated at our institution and routinely administered to patients undergoing hip arthroscopic surgery in an attempt to minimize perioperative pain. Of the 96 hip arthroscopic surgery cases analyzed, 40 patients received only general anesthesia (group A), while 56 patients received a preoperative femoral nerve block before the induction of general anesthesia (group B). These 2 groups of patients were used for comparison. All femoral nerve block procedures were performed by a staff anesthesiologist using ultrasound guidance. Once the needle tip was satisfactorily positioned in the direct vicinity of the nerve by ultrasound, between 15 and 25 mL of ropivacaine (0.33%-0.75%) was injected in 5-mL aliquots to achieve circumferential spread around the femoral nerve. After surgery, all patients were transferred to the PACU and then to the SDCU. Patients were discharged home when they met the institutional discharge criteria for ambulatory surgery.1,2
Demographic data were collected for all patients, including age, sex, height, weight, body mass index (BMI), physical status classification according to the American Society of Anesthesiologists (ASA), procedure performed, and operative time. Study data collected included the total intraoperative morphine-equivalent dose; pain scores (0-10 scale) recorded at 0, 15, 30, 45, and 60 minutes postoperatively in the PACU; total morphine-equivalent dose in the PACU; presence of nausea or vomiting in the PACU; time to discharge from the PACU; oxycodone consumption in the SDCU; and maximal patient-reported pain score (0-10) in the SDCU.
Groups A and B were compared via χ2 analyses for the categorical variables of sex, procedure type (percentage of patients undergoing osteochondroplasty), and presence of nausea or vomiting in the PACU. A χ2 analysis was also used to compare the distribution of patients by ASA classification for the 2 groups. Independent-sample Student t tests were used to compare the means for all continuous variables for the 2 groups. A P value <.05 was considered to be significant. All data collection and statistical analyses were performed by the lead author (A.P.D.) and were done so in compliance with institutional ethical requirements.
Results
A total of 108 consecutive hip arthroscopic surgery cases were performed at our institution between January 26, 2010 and July 9, 2012, of which 96 were included in our study. Of these patients, 40 had standard general anesthesia alone (group A) via a combination of anesthetic agents. Fifty-six patients had general anesthesia combined with a preoperative femoral nerve block (group B). Patients were separated based on the presence or absence of a preoperative femoral nerve block before the induction of general anesthesia.
Demographic Data
The general anesthesia group consisted of 22 male and 18 female patients, with a mean age of 34.18 ± 13.30 years. The mean BMI was 25.99 kg/m2. Twenty-four patients had an ASA classification of I, 14 patients had an ASA classification of II, and 2 patients had an ASA classification of III. Thirty-eight patients underwent osteochondroplasty for femoroacetabular impingement, 1 patient underwent loose body removal, and 1 patient underwent labral debridement without osteochondroplasty.
The femoral nerve block group consisted of 37 male and 19 female patients, with a mean age of 33.07 ± 11.57 years. The mean BMI was 25.42 kg/m2. Forty-one patients had an ASA classification of I, and 15 patients had an ASA classification of II. Fifty-one patients underwent osteochondroplasty for femoroacetabular impingement, 1 patient underwent loose body removal, and 4 patients underwent a labral-only procedure without osteochondroplasty.
There was no significant difference between the 2 groups with regard to sex (P = .27), age (P = .67), BMI (P = .52), ASA classification (P = .14), and type of procedure performed (P = .47) (Table 1).
Demographic Data a
ASA, American Society of Anesthesiologists; BMI, body mass index.
Intraoperative Data
The total intraoperative morphine-equivalent doses were significantly different between the 2 groups, with the general anesthesia group receiving a significantly higher intraoperative morphine-equivalent dose than the femoral nerve block group (8.05 ± 5.36 mg vs 2.72 ± 4.36 mg; P < .0001) (Table 2).
Outcome Measures a
Values are expressed as the mean unless otherwise specified. PACU, post-anesthesia care unit; SDCU, surgical day care unit.
Statistically significant (P < .05).
Postoperative Data
Postoperatively, patients in the general anesthesia group had higher mean patient-reported pain scores (0-10 scale) than those in the femoral nerve block group at 0, 15, 30, and 45 minutes after admission to the PACU; however, there was no significant difference between the means at these time points (3.51 vs 2.60 [P = .19]; 4.10 vs 3.33 [P = .29]; 4.55 vs 3.63 [P = .15]; and 4.15 vs 3.16 [P = .09], respectively). At 60 minutes after admission to the PACU, patients in the general anesthesia group had a significantly higher mean pain score than those in the femoral nerve block group (3.68 vs 2.48; P = .02) (Table 2).
Patients in the general anesthesia group received a significantly higher mean morphine-equivalent dose in the PACU than those in the femoral nerve block group (4.00 mg vs 2.04 mg; P = .025). Thirteen patients in group A (32.5%) and 23 in group B (41.1%) experienced postoperative nausea or vomiting (P = .39). There was no difference in time to discharge from the PACU between the 2 groups (81.53 ± 26.07 minutes vs 85.96 ± 29.79 minutes; P = .44) (Table 2).
After admission to the SDCU, there was no significant difference in oxycodone consumption between the 2 groups, with the general anesthesia group receiving a mean of 9.88 ± 5.13 mg and the femoral nerve block group receiving a mean of 8.21 ± 5.83 mg (P = .14). The mean maximal patient-reported pain score in the SDCU was significantly higher in the patients who received general anesthesia compared with those who received a femoral nerve block (4.95 vs 3.95; P = .018) (Table 2).
Of note, 2 patients in the general anesthesia group were admitted to our inpatient facilities overnight for pain management. Both admissions were unplanned and as a result of inadequate pain control in the PACU and SDCU after their elective procedures. These admissions prompted the use of a preoperative nerve block in patients undergoing hip arthroscopic surgery in an attempt to improve perioperative pain control. None of the patients who received a preoperative nerve block were admitted after their procedure. No complications were noted in any patient with regard to the femoral nerve block.
Discussion
The number of hip arthroscopic surgery cases performed by orthopaedic surgeons has increased dramatically over the past few years. 13 The minimally invasive nature of the procedure has made it the preferred treatment for various hip conditions and has enabled its application in an ambulatory setting. Unlike arthroscopic surgery in other joints, procedures on the hip may portend more significant pain because of the extensive innervation of the joint as well as the extensive bone resection that can be required as part of the procedure.
A recent study by Ward et al 48 illustrated the utility of a postoperative femoral nerve block as an adjunct to standard general anesthesia for pain control after hip arthroscopic surgery. Previous studies have also demonstrated the effectiveness of a femoral nerve block as an adjunctive measure for pain relief in patients with femoral neck fractures.5,17,21 Although the exact contributions of the various nerves are not entirely understood, the results of these studies support a significant involvement of the femoral nerve, particularly in terms of its contribution to postoperative pain.
The purpose of our retrospective review was to evaluate the potential utility of a preoperative femoral nerve block before hip arthroscopic surgery to reduce postoperative pain, a technique that has not yet been described in the literature. Reducing intraoperative and postoperative opioid consumption, postoperative pain scores, and opioid-related side effects are established benefits of preincisional nerve blocks.35,38 This is of immediate relevance to hip arthroscopic surgery performed on an outpatient basis as poorly controlled postoperative pain, postoperative nausea and vomiting, and excessive sedation constitute the most common causes of failure to discharge ambulatory surgery patients. 37 Further potential advantages of preoperative nerve blocks include a reduction in the surgical neuroendocrine stress response 8 and a decrease in central nervous system sensitization, thus reducing the incidence of persistent postoperative pain. 14 Furthermore, a preoperative procedure avoids the need for a postoperative injection in the proximity of the operative site and incisions.
Patients in our review who received a preoperative femoral nerve block also received significantly lower doses of intraoperative morphine. This finding, however, did not translate into significantly lower rates of postoperative nausea and vomiting or decreased times to discharge. This is not an uncommon finding, as earlier evidence indicates that current discharge guidelines and clinical pathways have not been able to implement accelerated routes that capitalize on the benefits of regional anesthesia techniques. 31 Postoperative pain scores in the PACU were lower for patients in the femoral nerve block group at all time points and significantly lower at 60 minutes postoperatively (Figure 1). Additionally, the maximal patient-reported pain score before discharge from the SDCU was significantly lower in patients who received a block. The trends seen in our data illustrate the potential effectiveness of a preoperative femoral nerve block in reducing postoperative pain scores. Reducing postoperative pain could potentially translate into reduced narcotic consumption, fewer opioid-related side effects, earlier ambulation after the procedure, earlier discharge times, lower admission rates for postoperative pain control, improved patient satisfaction, and overall improved cost-effectiveness of the procedure. However, further prospective randomized studies are required.
Patient-reported pain scores for each group by the number of minutes after admission to the post-anesthesia care unit (PACU). Values are expressed as mean ± standard error of the mean.
Our results are limited by the retrospective nature of this review. No standard femoral nerve block protocol was employed; the local anesthetic concentration and dose used for the block were at the discretion of the staff anesthetist performing the block, which may have resulted in some patients receiving a stronger postoperative analgesic effect than others. Furthermore, intraoperative anesthetic medications and doses used, including antiemetic prophylactic medications, were determined on an individual basis by the anesthetist performing the case and varied considerably between patients. While most patients received some form of antiemetic prophylaxis during surgery, the dosing, combination, and timing of the various medications used were different for every patient, which may have influenced the pain scores and rates of postoperative nausea and vomiting. The absence of data beyond the first postoperative day also limits the effect of this retrospective review.
The decision to implement a routine preoperative nerve block should be based on conclusive data from adequately powered prospective randomized trials. A prospective randomized controlled trial comparing preoperative femoral nerve blocks to standard general anesthesia with postoperative narcotics is currently underway at our institution to further evaluate the effect of femoral nerve blocks on postoperative pain control in patients undergoing hip arthroscopic surgery. This study has illustrated the potential benefit of a preoperative nerve block in postoperative pain control and has been used in a pretrial power analysis to determine group sizes for the prospective trial.
