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Effectiveness of Femoral Nerve Blockade for Pain Control After Total Knee Arthroplasty
RESEARCH
Effectiveness of Femoral Nerve Blockade for Pain Control After Total Knee Arthroplasty Victor M. Duarte, BA, RN, RNFA Wendy M. Fallis, PhD, RN Dean Slonowsky, PhD Kwadwo Kwarteng, MSc Colin K. L. Yeung, BSc
Control of postoperative pain is a major concern for patients undergoing total knee arthroplasty (TKA). The purpose of this study was to investigate pain control and opioid use, as well as length of stay, ambulation time, antiemetic use, and degree of mobilization for patients undergoing total knee arthroplasty, comparing those receiving femoral nerve block (FNB) to those receiving no femoral nerve block. Using retrospective patient record data, 133 subjects from an acute care community hospital in western Canada were split into three groups: no FNB (control group, n ⫽ 49), single-shot FNB (n ⫽ 33), and continuous FNB (n ⫽ 51). There was a statistically significant improvement in pain control on day of surgery for the FNB group compared with the no-FNB group, and reduction in opioid usage on days 0, 1, and 2 in the continuous FNB group compared with the no-FNB and single-shot group. Also noted was a statistically significant reduction in antiemetic use in the FNB compared with the no-FNB group on the day after surgery. This study is in accordance with earlier studies that support continuous FNB as an effective method for achieving postoperative pain control and reducing opioid use for patients undergoing TKA. © 2006 by American Society of PeriAnesthesia Nurses.
FOR PATIENTS undergoing total knee arthroplasty (TKA), also known as total knee replacement, control of postoperative pain is a major concern. There are numerous methods used for
pain control, with each method having its own perceived benefits and shortcomings.1,2 Morphine is given frequently as the primary analgesic; however, the use of morphine is
Victor M. Duarte, BA, RN, RNFA, is an Anesthesia Nurse Clinician, Victoria General Hospital, Winnipeg, Manitoba, and Adjunct Lecturer in the Faculty of Medicine, Department of Anesthesia, University of Manitoba, Winnipeg, Manitoba; Wendy M. Fallis, PhD, RN, is Director, Clinical Institute of Applied Research and Education, Victoria General Hospital, and Adjunct Professor, Faculty of Nursing, University of Manitoba, Winnipeg, Manitoba; Dean Slonowsky, PhD, is Assistant Professor of Statistics, University of Manitoba, Winnipeg, Manitoba, Canada; Kwadwo Kwarteng, MSc, is a PhD student, University of Louisville, Louisville, KY; and Colin K. L. Yeung, BSc, is a medical student, University of Manitoba, Winnipeg, Manitoba, Canada. Funding for this project was provided by the Victoria General Hospital Medical Staff Council and the Victoria General Hospital Foundation, and was also partially supported by National Science and Engineering Research Council. Address correspondence to Victor Duarte, BA, RN, RNFA, 2340 Pembina Hwy, Winnipeg, Manitoba R2T 2E8, Canada; e-mail address: [email protected]. © 2006 by American Society of PeriAnesthesia Nurses. 1089-9472/06/2105-0003$32.00/0 doi:10.1016/j.jopan.2006.05.011 Journal of PeriAnesthesia Nursing, Vol 21, No 5 (October), 2006: pp 311-316
311
312
associated with side effects that compromise both patient comfort and safety.3 Alternative pain control measures are sought to avoid such a situation. The following hypothesis was tested in the present study. There are significant differences postoperatively between patients receiving TKA who receive femoral nerve block (FNB) (continuous or single) compared with those receiving patient-controlled analgesia (PCA) only for pain control with the following variables: use of opioids, pain control, antiemetic use, time until ambulation, degree of mobilization, and length of hospital stay.
Methodology The study was conducted in a 233-bed acute care community hospital in western Canada. Medical charts for 143 patients who had undergone elective TKA were reviewed. Approval for this study was received from the facility and the University of Manitoba Research Ethics Board (REB). Consent from patients to access their medical records was waived by the REB. Power analysis revealed that a minimum sample of 30 subjects in each of the FNB groups and non-FNB group was required to achieve a power of greater than 90% based on standard deviation reported2 for morphine use. The level of significance was set at 0.05. Data were collected through retrospective medical chart reviews of patients who had undergone a TKA during the fiscal year of 2000-2001. Pertinent data from patient charts were transcribed onto data collection forms. Data from these forms were then entered into a Microsoft Excel 97 (Redmond, WA) spreadsheet and subsequently analyzed using SAS Statistical Software (v. 8.2, SAS Institute, Cary, NC). All patients undergoing elective TKA were included. However, patients were excluded if they had undergone knee revision surgery, emergency knee replacements (due to trauma), any contraindications to the regional or anes-
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thetic technique, or pre-existing neurologic deficits in the lower extremities. Patients who were unable to comprehend pain scales or use a PCA device, or who were discharged beyond seven postoperative days as a result of complications unrelated to the initial diagnosis also were excluded. Data analysis involved statistical tests for comparison of three groups (continuous, single, and no FNB). Pain was assessed using pain scores as reported by patients using a visual analog scale (VAS) with scores ranging from 0 to 5, a scale used by the facility at that time (0 no pain; 5 the highest amount of pain). The highest pain score reported on the patient analgesia flow sheet for each postoperative day was recorded. Opioid use was defined as the amount of morphine or morphine equivalent recorded in milligrams that was provided to the patient via any route. Frequency of antiemetics given was used as an indicator of nausea/vomiting.1 Ambulation was defined as the act of making the operative knee moveable and of restoring the power of motion in the joint to the point where the patient is ambulating. Days to ambulation was recorded as the first day of ambulation with or without walking aids after TKA. Mobilization was defined as the return of function of the operative joint and was indicated by the number of degrees of range of motion (ROM) that the patient achieved on the continuous passive motion machine. Initial comparisons of the three groups on demographic variables, previous experiences with TKA surgery, and presurgery medications were undertaken to determine if the groups were similar. No differences were noted among the three groups on any of these variables, indicating that subsequent analysis of outcome variables was appropriate. After the initial comparisons, outcome measures were analyzed daily up to seven days postoperatively (day 0 ⫽ day of surgery), coinciding with the seven-day care map used by the facility for
FEMORAL NERVE BLOCKADE FOR PAIN CONTROL
this patient population. Comparisons were made between the three groups on the following variables: amount of opioids used (all narcotics were converted to morphine equivalent),4 length of stay (LOS), pain scores (VAS), frequency of antiemetics used, number of days to ambulation, maximum degree of mobilization, and achieved range of motion. Because outcome variables deviated significantly from the normality assumption, the Kruskal-Wallis test was used for quantitative variables and chi-square tests of association were used for categoric variables. If significant differences among three groups were identified, post-hoc testing would be used to compare each two groups for differences. In addition, for outcome variables that could be dichotomized, estimates of the odds ratios were determined. Type I error was controlled by using ␣ ⫽ .017 in chi-square tests of multiple comparisons. All patients had spinal block with epimorph. For patients receiving FNB, the following standard anesthetic procedure was used. Patients were placed in a supine position with legs extended. The point of injection was identified using the surface landmarks. A line was drawn connecting the pubic tubercle and the anterior superior iliac spine, which marks the inguinal ligament, palpating the femoral artery below the inguinal ligament.5 The initial insertion was 1 cm below the inguinal ligament and lateral to the femoral artery. A small amount of 1% lidocaine was used to create a skin wheal at the injection point for patient comfort. The insulated needle (Pajunk 19.5 G ⫻ 50 mm, facet-tip) was inserted immediately lateral to the femoral artery pulse at the femoral crease and advanced at a 60-degree angle posterior and cephalic. Once the desired needle endpoint placement was obtained, determined by stimulation of quadriceps and patella of approximately 0.40 mA on a nerve stimulator (Pajunk, MultiStim VARIO Nerve Stimulator), 30 mL of local anesthetic (10 mL 1% ropivacaine mixed with 20 mL of carbonated 2% lidocaine) was
313
then injected after aspiration. After the initial dose of local anesthetic was injected, a Pajunk 20-G ⫻ 50-cm Polyamid catheter with stylet was then threaded through the insulated needle into the femoral nerve sheath.6 The needle was then removed. The catheter was taped into place using sterile strips, and a sterile dressing was applied. This same technique was used for the single-shot FNB, but no catheter was inserted. After surgery, all patients were transferred to the PACU, and then to an inpatient ward. Immediately after surgery, the three groups started identical physical therapy regimens. Patients in the continuous FNB group had the catheter removed on day 2.
Results Of the 143 patients who had undergone elective TKA surgery, 10 patients were excluded from the study. These 10 patients developed complications (not related to the particular anesthetic procedure administered) and had to be taken off the usual seven-day care map. Of the remaining 133 subjects, 49 had no FNB, 33 had a single-shot FNB, and 51 had a continuous FNB. Various observations were recorded for each subject from day of surgery (day 0) to postoperative day 7. Statistical tests confirmed homogeneity of subjects among the three treatments groups on demographic variables (sex, age, height, weight, body mass index) (Table 1). Pain scores were dichotomized into two clinically meaningful categories—managed pain (ⱕ2) and unmanaged pain (⬎2)— using a scale of 0 to 5, and the resulting data were analyzed using chi-square tests-of-association. With respect to equivalent morphine use (mg), our tests detected a significant difference among the treatment groups on each of days 0, 1, and 2 (chi-square ⫽ 28.13, P ⬍ .0001; chi-square ⫽ 12.29, P ⫽ .0021; and chi-square ⫽ 10.33, P ⫽ .0057), respectively. On each of these days, Dunn’s non-
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Table 1. Summary Statistics on Demographic Variables (N ⴝ 133)
Sex Male Female Age (y) Mean (SD) Range Height (cm) Mean (SD) Range Weight (kg) Mean (SD) Range BMI Mean (SD) Range
n (%)
Mean (SD)
52 (39.1) 81 (60.9) 69.71 (9.27) 38.0-88.0 166.16 (10.15) 142.2-189.2 84.27 (16.24) 47.7-127.0 30.56 (5.59) 17.6-48.1
Abbreviation: BMI, body mass index.
parametric multiple comparison procedure revealed a significant difference between the no-block and continuous FNB groups, and between the single-shot FNB and continuous FNB groups. In particular, there was a significant decrease in morphine consumption by patients on the continuous FNB over patients in the two other treatment groups, as quantified in Table 2. No significant differences were observed in days 3 through 7 (Fig 1).
Mean Morphine (mg)
Variable
25 20 15
Nil Single
10
Continuous
5 0 0
1
2
3
4
5
6
7
8
9
Days
Fig 1. Overall mean amount of equivalent morphine (mg) by group over days. Note: All opioids converted to morphine equivalent.
In contrast, only on day 1 did we detect a significant difference among treatments with respect to frequency of antiemetic use (chisquare ⫽ 7.72, P ⫽ .0211) (Fig 2). Follow-up multiple comparisons contributed this difference to a significantly lower frequency of antiemetic use by continuous FNB subjects over subjects for which no block was administered. Only on day 0 did we detect a significant association between treatment and pain scores (chisquare ⫽ 4.86, P ⫽ .0003) (Fig 3). Follow-up multiple comparisons for day 0 revealed that the proportion of individuals with unmanaged pain was significantly higher among subjects undergoing no block than among continuous FNB subjects (chi-square ⫽ 10.54, P ⫽ .0012). Further analysis using odds ratios indicated that subjects in the no-FNB group were 5.52 times
Table 2. Comparison of Equivalent Morphine Use on Day of Surgery (Day 0) and Postoperative Days 1 and 2
Day 0
No FNB
FNB (single)
6.76 (12.88)
6.09 (12.38) 6.09 (12.38)
Day 1
6.76 (12.88) 17.83 (19.70)
Day 2
17.83 (19.70) 11.74 (12.65) 11.74 (12.65)
ⴱP ⬍ .05.
20.20 (29.34) 20.20 (29.34) 13.62 (14.33) 13.62 (14.33)
FNB (continuous)
1.42 (5.02) 1.42 (5.02) 7.76 (11.83) 7.76 (11.83) 6.55 (7.89) 6.55 (7.89)
Mean Difference
0.67 4.67ⴱ 5.34ⴱ ⫺2.37 12.44ⴱ 10.07ⴱ ⫺1.88 7.07ⴱ 5.18ⴱ
FEMORAL NERVE BLOCKADE FOR PAIN CONTROL 4
3 2.5
Nil
2
Single Continuous
1.5
There was no significant difference among the groups with respect to degree of mobilization on any day. This may be a result of patients being on a care-map, and hence not being pushed beyond the expected norm.
1 0.5 0 0
1
2
3
4
5
6
7
8
9
Days
Fig 2.
Mean frequency of antiemetic use by group over days.
more likely to have unmanaged pain than the single-shot FNB group, and were 3.89 times more likely to have unmanaged pain compared with the continuous FNB group. We noted no significant difference among the three groups regarding LOS (P ⫽ .873), or days to ambulation (P ⫽ .115) and maximum degree of mobilization achieved (P ⫽ .547).
Discussion Similar to Edwards and Wright,7 a highly significant difference in morphine use was found among the three groups on the day of surgery (P ⬍ .0001) as well as on the two days after surgery (day 1, P ⫽ .0021; day 2, P ⫽ .0057) (Fig 1). Follow-up multiple comparisons detected a significant reduction in morphine use by the continuous FNB group over the singleshot FNB and the no-FNB groups on each of days 0, 1, and 2. There was no significant difference between the three groups regarding morphine intake beyond day 2. It should be noted that the femoral nerve catheter was removed from patients in the continuous FNB group on day 2. Regarding antiemetic use, as demonstrated in Figure 2, there was a significant difference among the groups on postoperative day 1 only (P ⫽ .0211). Follow-up analysis attributed this to a significant reduction in antiemetic use in the continuous FNB group over the no-FNB group. On average, individuals in the continuous FNB group used antiemetics 47% less than individuals in the no-FNB group on this day.
On postoperative day 0, there was a significant difference in pain levels among the three groups (Fig 3). As noted in related studies,6 our follow-up multiple comparisons revealed that the no-FNB group had significantly higher levels of unmanaged pain than the single-shot FNB group (P ⫽ .0006) and the continuous FNB group (P ⫽ 0.0012) on this day. However, pain scores for patients in the single-shot FNB compared with the continuous FNB group were not significantly different. Although not significant, it is interesting to note, as demonstrated in Figure 3, that the continuous FNB group experienced the highest levels of unmanaged pain on day 2, the day of nerve block catheter removal. This may be a result of patients having good pain control on days 0 and 1, then having the catheter removed without adequate pain control with oral analgesics. No significant difference in pain scores was observed among the three groups from day 3 onward, a finding that was consistent with the analysis of the other variables.
Conclusion In conclusion, similar to previous findings,1,7-9 this study lends evidence to support the continuous FNB procedure as an effective technique that improves recovery, analgesia, and out70 Percent (%) frequency
Mean frequency
3.5
315
60 50 Nil
40
Single
30
Continuous
20 10 0 0
1
2
3
4
5
6
7
Days
Fig 3. Percent histogram for patients with high (unmanaged) pain scores (>2) by group over days.
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comes of patients after TKA. Specifically, we observed a significant general reduction in morphine use (Fig 1) in the continuous FNB group from the day of surgery to postoperative day 2 compared with the other two techniques. With regards to pain (Fig 3), both the continuous and single-shot FNB groups had significantly less unmanaged pain than the no-FNB group on the day of surgery (day 0). The three groups did not differ significantly on any other day on this variable. Interestingly, on postoperative day 2, the single-shot FNB group appeared to have better control of unmanaged pain than the continuous FNB group (Fig 3). Indeed, although it is not statistically significant, subjects in the continuous FNB group were 2.56 times more likely to have unmanaged pain than the single-shot FNB group on this day. This observation should be tempered with the fact that patients in the single-shot FNB group consumed more than double the amount of morphine than the continuous FNB group on day 2, an amount comparable to the no-FNB group (Table 2). Hence, although subjects in the single-shot FNB group had lower levels of unmanaged pain than the continuous FNB group on day 2, this was at the cost of significantly higher morphine intake. The general findings in this study are consistent
with previous studies,6,10-12 indicating that FNB improves analgesia and decreases opioid and antiemetic use after TKR and supports the use of FNB in patients undergoing TKA. Limitations of this study must be noted. First, inaccuracies may have occurred in the collection and recording of the data in patients’ charts, which were outside investigators’ control. Second, the results of this study are applicable to patients who were selected for TKA only and therefore are generalizable only to this population. Last, being a retrospective study, noncomparable information may have been obtained from the different groups, which may arise from health care professionals interpreting information differently, or the study subjects reporting events in a noncomparable manner. However, the study demonstrated that a retrospective chart review, a more economical method of undertaking a study compared with prospective research, supported the findings from other studies. Additional research using randomized control trials in multiple sites is suggested to clearly establish the significance of FNB over other techniques as an effective procedure on TKA recovery.
References 1. Hirst GC, Land SA, Dust WN, et al. Femoral nerve block: Single injection versus continuous infusion for total knee replacement. Reg Anesth. 1996;21:292-297. 2. Singelyn FJ, Deyaert M, Joris D, et al. Effects of intravenous patient-controlled analgesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthroplasty. Anesth Analg. 1998;87: 88-92. 3. Serpell M, Millar F, Thomson M. Comparison of lumbar plexus block versus conventional opioid analgesia after total knee replacement. Anaesthesia. 1991;46:275-277. 4. Librach SL, Squires BP. The Pain Manual: Principles and Issues in Cancer Pain Management. Montreal, Quebec, Canada: Pegasus Healthcare International; 1997:122. 5. Jacques CE. Peripheral Nerve Blocks: A Color Atlas. Philadelphia, Pa: Lippincott, Williams & Wilkins; 1999:96. 6. Dahl JB, Christiansen CL, Daugaard JJ, et al. Continuous blockade of the lumbar plexus after knee surgery⫺ postoperative analgesia and bupivacaine plasma concentrations. Anaesthesia. 1988;43:1015-1018.
7. Edwards ND, Wright EM. Continuous low-dose 3-in-1 nerve blockade for postoperative pain relief after total knee replacement. Anesth Analg. 1992;75:265-267. 8. Capdevila X, Barthelet Y, Biboulet P, et al. Effects of perioperative analgesic technique on the surgical outcome and duration of rehabilitation after major knee surgery [abstract]. Anesthesiology. 1999;91:8-15. 9. Allen HW, Liu SS, Ware PD, et al. Peripheral nerve blocks improve analgesia after total knee replacement surgery. Anesth Analg. 1998;87:93-97. 10. Mulroy MF, Larkin KL, Batra MS, et al. Femoral nerve block with 0.25% or 0.5% bupivacaine improves postoperative analgesia following outpatient arthroscopic anterior cruciate ligament repair. Reg Anesth Pain Med. 2001;26:24-29. 11. Schultz P, Anker-Møller E, Dahl JB, et al. Postoperative pain treatment after open knee surgery: Continuous lumbar plexus block with bupivacaine versus epidural morphine. Reg Anesth. 1991;16:34-37. 12. Wang H, Boctor B, Verner J. The effect of single-injection femoral nerve block on rehabilitation and length of hospital stay after total knee replacement. Reg Anesth Pain Med. 2002;27:139-144.
Effectiveness of Femoral Nerve Blockade for Pain Control After Total Knee Arthroplasty Victor M. Duarte, BA, RN, RNFA Wendy M. Fallis, PhD, RN Dean Slonowsky, PhD Kwadwo Kwarteng, MSc Colin K. L. Yeung, BSc
Control of postoperative pain is a major concern for patients undergoing total knee arthroplasty (TKA). The purpose of this study was to investigate pain control and opioid use, as well as length of stay, ambulation time, antiemetic use, and degree of mobilization for patients undergoing total knee arthroplasty, comparing those receiving femoral nerve block (FNB) to those receiving no femoral nerve block. Using retrospective patient record data, 133 subjects from an acute care community hospital in western Canada were split into three groups: no FNB (control group, n ⫽ 49), single-shot FNB (n ⫽ 33), and continuous FNB (n ⫽ 51). There was a statistically significant improvement in pain control on day of surgery for the FNB group compared with the no-FNB group, and reduction in opioid usage on days 0, 1, and 2 in the continuous FNB group compared with the no-FNB and single-shot group. Also noted was a statistically significant reduction in antiemetic use in the FNB compared with the no-FNB group on the day after surgery. This study is in accordance with earlier studies that support continuous FNB as an effective method for achieving postoperative pain control and reducing opioid use for patients undergoing TKA. © 2006 by American Society of PeriAnesthesia Nurses.
FOR PATIENTS undergoing total knee arthroplasty (TKA), also known as total knee replacement, control of postoperative pain is a major concern. There are numerous methods used for
pain control, with each method having its own perceived benefits and shortcomings.1,2 Morphine is given frequently as the primary analgesic; however, the use of morphine is
Victor M. Duarte, BA, RN, RNFA, is an Anesthesia Nurse Clinician, Victoria General Hospital, Winnipeg, Manitoba, and Adjunct Lecturer in the Faculty of Medicine, Department of Anesthesia, University of Manitoba, Winnipeg, Manitoba; Wendy M. Fallis, PhD, RN, is Director, Clinical Institute of Applied Research and Education, Victoria General Hospital, and Adjunct Professor, Faculty of Nursing, University of Manitoba, Winnipeg, Manitoba; Dean Slonowsky, PhD, is Assistant Professor of Statistics, University of Manitoba, Winnipeg, Manitoba, Canada; Kwadwo Kwarteng, MSc, is a PhD student, University of Louisville, Louisville, KY; and Colin K. L. Yeung, BSc, is a medical student, University of Manitoba, Winnipeg, Manitoba, Canada. Funding for this project was provided by the Victoria General Hospital Medical Staff Council and the Victoria General Hospital Foundation, and was also partially supported by National Science and Engineering Research Council. Address correspondence to Victor Duarte, BA, RN, RNFA, 2340 Pembina Hwy, Winnipeg, Manitoba R2T 2E8, Canada; e-mail address: [email protected]. © 2006 by American Society of PeriAnesthesia Nurses. 1089-9472/06/2105-0003$32.00/0 doi:10.1016/j.jopan.2006.05.011 Journal of PeriAnesthesia Nursing, Vol 21, No 5 (October), 2006: pp 311-316
311
312
associated with side effects that compromise both patient comfort and safety.3 Alternative pain control measures are sought to avoid such a situation. The following hypothesis was tested in the present study. There are significant differences postoperatively between patients receiving TKA who receive femoral nerve block (FNB) (continuous or single) compared with those receiving patient-controlled analgesia (PCA) only for pain control with the following variables: use of opioids, pain control, antiemetic use, time until ambulation, degree of mobilization, and length of hospital stay.
Methodology The study was conducted in a 233-bed acute care community hospital in western Canada. Medical charts for 143 patients who had undergone elective TKA were reviewed. Approval for this study was received from the facility and the University of Manitoba Research Ethics Board (REB). Consent from patients to access their medical records was waived by the REB. Power analysis revealed that a minimum sample of 30 subjects in each of the FNB groups and non-FNB group was required to achieve a power of greater than 90% based on standard deviation reported2 for morphine use. The level of significance was set at 0.05. Data were collected through retrospective medical chart reviews of patients who had undergone a TKA during the fiscal year of 2000-2001. Pertinent data from patient charts were transcribed onto data collection forms. Data from these forms were then entered into a Microsoft Excel 97 (Redmond, WA) spreadsheet and subsequently analyzed using SAS Statistical Software (v. 8.2, SAS Institute, Cary, NC). All patients undergoing elective TKA were included. However, patients were excluded if they had undergone knee revision surgery, emergency knee replacements (due to trauma), any contraindications to the regional or anes-
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thetic technique, or pre-existing neurologic deficits in the lower extremities. Patients who were unable to comprehend pain scales or use a PCA device, or who were discharged beyond seven postoperative days as a result of complications unrelated to the initial diagnosis also were excluded. Data analysis involved statistical tests for comparison of three groups (continuous, single, and no FNB). Pain was assessed using pain scores as reported by patients using a visual analog scale (VAS) with scores ranging from 0 to 5, a scale used by the facility at that time (0 no pain; 5 the highest amount of pain). The highest pain score reported on the patient analgesia flow sheet for each postoperative day was recorded. Opioid use was defined as the amount of morphine or morphine equivalent recorded in milligrams that was provided to the patient via any route. Frequency of antiemetics given was used as an indicator of nausea/vomiting.1 Ambulation was defined as the act of making the operative knee moveable and of restoring the power of motion in the joint to the point where the patient is ambulating. Days to ambulation was recorded as the first day of ambulation with or without walking aids after TKA. Mobilization was defined as the return of function of the operative joint and was indicated by the number of degrees of range of motion (ROM) that the patient achieved on the continuous passive motion machine. Initial comparisons of the three groups on demographic variables, previous experiences with TKA surgery, and presurgery medications were undertaken to determine if the groups were similar. No differences were noted among the three groups on any of these variables, indicating that subsequent analysis of outcome variables was appropriate. After the initial comparisons, outcome measures were analyzed daily up to seven days postoperatively (day 0 ⫽ day of surgery), coinciding with the seven-day care map used by the facility for
FEMORAL NERVE BLOCKADE FOR PAIN CONTROL
this patient population. Comparisons were made between the three groups on the following variables: amount of opioids used (all narcotics were converted to morphine equivalent),4 length of stay (LOS), pain scores (VAS), frequency of antiemetics used, number of days to ambulation, maximum degree of mobilization, and achieved range of motion. Because outcome variables deviated significantly from the normality assumption, the Kruskal-Wallis test was used for quantitative variables and chi-square tests of association were used for categoric variables. If significant differences among three groups were identified, post-hoc testing would be used to compare each two groups for differences. In addition, for outcome variables that could be dichotomized, estimates of the odds ratios were determined. Type I error was controlled by using ␣ ⫽ .017 in chi-square tests of multiple comparisons. All patients had spinal block with epimorph. For patients receiving FNB, the following standard anesthetic procedure was used. Patients were placed in a supine position with legs extended. The point of injection was identified using the surface landmarks. A line was drawn connecting the pubic tubercle and the anterior superior iliac spine, which marks the inguinal ligament, palpating the femoral artery below the inguinal ligament.5 The initial insertion was 1 cm below the inguinal ligament and lateral to the femoral artery. A small amount of 1% lidocaine was used to create a skin wheal at the injection point for patient comfort. The insulated needle (Pajunk 19.5 G ⫻ 50 mm, facet-tip) was inserted immediately lateral to the femoral artery pulse at the femoral crease and advanced at a 60-degree angle posterior and cephalic. Once the desired needle endpoint placement was obtained, determined by stimulation of quadriceps and patella of approximately 0.40 mA on a nerve stimulator (Pajunk, MultiStim VARIO Nerve Stimulator), 30 mL of local anesthetic (10 mL 1% ropivacaine mixed with 20 mL of carbonated 2% lidocaine) was
313
then injected after aspiration. After the initial dose of local anesthetic was injected, a Pajunk 20-G ⫻ 50-cm Polyamid catheter with stylet was then threaded through the insulated needle into the femoral nerve sheath.6 The needle was then removed. The catheter was taped into place using sterile strips, and a sterile dressing was applied. This same technique was used for the single-shot FNB, but no catheter was inserted. After surgery, all patients were transferred to the PACU, and then to an inpatient ward. Immediately after surgery, the three groups started identical physical therapy regimens. Patients in the continuous FNB group had the catheter removed on day 2.
Results Of the 143 patients who had undergone elective TKA surgery, 10 patients were excluded from the study. These 10 patients developed complications (not related to the particular anesthetic procedure administered) and had to be taken off the usual seven-day care map. Of the remaining 133 subjects, 49 had no FNB, 33 had a single-shot FNB, and 51 had a continuous FNB. Various observations were recorded for each subject from day of surgery (day 0) to postoperative day 7. Statistical tests confirmed homogeneity of subjects among the three treatments groups on demographic variables (sex, age, height, weight, body mass index) (Table 1). Pain scores were dichotomized into two clinically meaningful categories—managed pain (ⱕ2) and unmanaged pain (⬎2)— using a scale of 0 to 5, and the resulting data were analyzed using chi-square tests-of-association. With respect to equivalent morphine use (mg), our tests detected a significant difference among the treatment groups on each of days 0, 1, and 2 (chi-square ⫽ 28.13, P ⬍ .0001; chi-square ⫽ 12.29, P ⫽ .0021; and chi-square ⫽ 10.33, P ⫽ .0057), respectively. On each of these days, Dunn’s non-
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314
Table 1. Summary Statistics on Demographic Variables (N ⴝ 133)
Sex Male Female Age (y) Mean (SD) Range Height (cm) Mean (SD) Range Weight (kg) Mean (SD) Range BMI Mean (SD) Range
n (%)
Mean (SD)
52 (39.1) 81 (60.9) 69.71 (9.27) 38.0-88.0 166.16 (10.15) 142.2-189.2 84.27 (16.24) 47.7-127.0 30.56 (5.59) 17.6-48.1
Abbreviation: BMI, body mass index.
parametric multiple comparison procedure revealed a significant difference between the no-block and continuous FNB groups, and between the single-shot FNB and continuous FNB groups. In particular, there was a significant decrease in morphine consumption by patients on the continuous FNB over patients in the two other treatment groups, as quantified in Table 2. No significant differences were observed in days 3 through 7 (Fig 1).
Mean Morphine (mg)
Variable
25 20 15
Nil Single
10
Continuous
5 0 0
1
2
3
4
5
6
7
8
9
Days
Fig 1. Overall mean amount of equivalent morphine (mg) by group over days. Note: All opioids converted to morphine equivalent.
In contrast, only on day 1 did we detect a significant difference among treatments with respect to frequency of antiemetic use (chisquare ⫽ 7.72, P ⫽ .0211) (Fig 2). Follow-up multiple comparisons contributed this difference to a significantly lower frequency of antiemetic use by continuous FNB subjects over subjects for which no block was administered. Only on day 0 did we detect a significant association between treatment and pain scores (chisquare ⫽ 4.86, P ⫽ .0003) (Fig 3). Follow-up multiple comparisons for day 0 revealed that the proportion of individuals with unmanaged pain was significantly higher among subjects undergoing no block than among continuous FNB subjects (chi-square ⫽ 10.54, P ⫽ .0012). Further analysis using odds ratios indicated that subjects in the no-FNB group were 5.52 times
Table 2. Comparison of Equivalent Morphine Use on Day of Surgery (Day 0) and Postoperative Days 1 and 2
Day 0
No FNB
FNB (single)
6.76 (12.88)
6.09 (12.38) 6.09 (12.38)
Day 1
6.76 (12.88) 17.83 (19.70)
Day 2
17.83 (19.70) 11.74 (12.65) 11.74 (12.65)
ⴱP ⬍ .05.
20.20 (29.34) 20.20 (29.34) 13.62 (14.33) 13.62 (14.33)
FNB (continuous)
1.42 (5.02) 1.42 (5.02) 7.76 (11.83) 7.76 (11.83) 6.55 (7.89) 6.55 (7.89)
Mean Difference
0.67 4.67ⴱ 5.34ⴱ ⫺2.37 12.44ⴱ 10.07ⴱ ⫺1.88 7.07ⴱ 5.18ⴱ
FEMORAL NERVE BLOCKADE FOR PAIN CONTROL 4
3 2.5
Nil
2
Single Continuous
1.5
There was no significant difference among the groups with respect to degree of mobilization on any day. This may be a result of patients being on a care-map, and hence not being pushed beyond the expected norm.
1 0.5 0 0
1
2
3
4
5
6
7
8
9
Days
Fig 2.
Mean frequency of antiemetic use by group over days.
more likely to have unmanaged pain than the single-shot FNB group, and were 3.89 times more likely to have unmanaged pain compared with the continuous FNB group. We noted no significant difference among the three groups regarding LOS (P ⫽ .873), or days to ambulation (P ⫽ .115) and maximum degree of mobilization achieved (P ⫽ .547).
Discussion Similar to Edwards and Wright,7 a highly significant difference in morphine use was found among the three groups on the day of surgery (P ⬍ .0001) as well as on the two days after surgery (day 1, P ⫽ .0021; day 2, P ⫽ .0057) (Fig 1). Follow-up multiple comparisons detected a significant reduction in morphine use by the continuous FNB group over the singleshot FNB and the no-FNB groups on each of days 0, 1, and 2. There was no significant difference between the three groups regarding morphine intake beyond day 2. It should be noted that the femoral nerve catheter was removed from patients in the continuous FNB group on day 2. Regarding antiemetic use, as demonstrated in Figure 2, there was a significant difference among the groups on postoperative day 1 only (P ⫽ .0211). Follow-up analysis attributed this to a significant reduction in antiemetic use in the continuous FNB group over the no-FNB group. On average, individuals in the continuous FNB group used antiemetics 47% less than individuals in the no-FNB group on this day.
On postoperative day 0, there was a significant difference in pain levels among the three groups (Fig 3). As noted in related studies,6 our follow-up multiple comparisons revealed that the no-FNB group had significantly higher levels of unmanaged pain than the single-shot FNB group (P ⫽ .0006) and the continuous FNB group (P ⫽ 0.0012) on this day. However, pain scores for patients in the single-shot FNB compared with the continuous FNB group were not significantly different. Although not significant, it is interesting to note, as demonstrated in Figure 3, that the continuous FNB group experienced the highest levels of unmanaged pain on day 2, the day of nerve block catheter removal. This may be a result of patients having good pain control on days 0 and 1, then having the catheter removed without adequate pain control with oral analgesics. No significant difference in pain scores was observed among the three groups from day 3 onward, a finding that was consistent with the analysis of the other variables.
Conclusion In conclusion, similar to previous findings,1,7-9 this study lends evidence to support the continuous FNB procedure as an effective technique that improves recovery, analgesia, and out70 Percent (%) frequency
Mean frequency
3.5
315
60 50 Nil
40
Single
30
Continuous
20 10 0 0
1
2
3
4
5
6
7
Days
Fig 3. Percent histogram for patients with high (unmanaged) pain scores (>2) by group over days.
DUARTE ET AL
316
comes of patients after TKA. Specifically, we observed a significant general reduction in morphine use (Fig 1) in the continuous FNB group from the day of surgery to postoperative day 2 compared with the other two techniques. With regards to pain (Fig 3), both the continuous and single-shot FNB groups had significantly less unmanaged pain than the no-FNB group on the day of surgery (day 0). The three groups did not differ significantly on any other day on this variable. Interestingly, on postoperative day 2, the single-shot FNB group appeared to have better control of unmanaged pain than the continuous FNB group (Fig 3). Indeed, although it is not statistically significant, subjects in the continuous FNB group were 2.56 times more likely to have unmanaged pain than the single-shot FNB group on this day. This observation should be tempered with the fact that patients in the single-shot FNB group consumed more than double the amount of morphine than the continuous FNB group on day 2, an amount comparable to the no-FNB group (Table 2). Hence, although subjects in the single-shot FNB group had lower levels of unmanaged pain than the continuous FNB group on day 2, this was at the cost of significantly higher morphine intake. The general findings in this study are consistent
with previous studies,6,10-12 indicating that FNB improves analgesia and decreases opioid and antiemetic use after TKR and supports the use of FNB in patients undergoing TKA. Limitations of this study must be noted. First, inaccuracies may have occurred in the collection and recording of the data in patients’ charts, which were outside investigators’ control. Second, the results of this study are applicable to patients who were selected for TKA only and therefore are generalizable only to this population. Last, being a retrospective study, noncomparable information may have been obtained from the different groups, which may arise from health care professionals interpreting information differently, or the study subjects reporting events in a noncomparable manner. However, the study demonstrated that a retrospective chart review, a more economical method of undertaking a study compared with prospective research, supported the findings from other studies. Additional research using randomized control trials in multiple sites is suggested to clearly establish the significance of FNB over other techniques as an effective procedure on TKA recovery.
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