|Year : 2021 | Volume
| Issue : 2 | Page : 143-148
Comparison of 0.125% and 0.2% ropivacaine in continuous lumbar plexus block for postoperative analgesia after total hip arthroplasty
Anand Murugesan1, Deepak Gurunathan1, MS Raghuraman2, Daivam Indumathi1, M Thiriloga Sundary1
1 Department of Anaesthesiology and Pain Management, Apollo Hospitals, Chennai, Tamil Nadu, India
2 Department of Anesthesiology, Sree Balaji Medical College and Hospital, Chennai, Tamil Nadu, India
|Date of Submission||05-Mar-2021|
|Date of Decision||26-Apr-2021|
|Date of Acceptance||28-Jun-2021|
|Date of Web Publication||29-Sep-2021|
Dr. M S Raghuraman
Department of Anesthesiology, Sree Balaji Medical College and Hospital, BIHER, Chromepet, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Background: Lower concentrations of ropivacaine in continuous lumbar plexus block (LPB) have not been studied adequately. Thus, we designed this prospective, randomized, comparative study to evaluate the two different concentrations of ropivacaine (0.125% and 0.2%) in continuous LPB for postoperative pain relief following total hip arthroplasty (THA).
Materials and Methods: Fifty patients undergoing THA under standardized subarachnoid block have been randomly allocated to receive a continuous infusion of either 0.125% (Group 1) or 0.2% (Group 2) of ropivacaine in LPB done under the guidance of peripheral nerve stimulator. The primary outcome was consumption of tramadol during the first 24 h and the secondary outcomes were quality of sensory and motor blockade and consumption of ropivacaine.
Results: The total amount of tramadol did not differ significantly (P = 0.442) between the two groups. Furthermore, the duration of sensory and motor blockade did not differ significantly between the two groups. However, the average consumption of ropivacaine was significantly lower in Group 1 when compared to Group 2 (238.80 mg vs. 380.64 mg, P = 0.0001).
Conclusion: Administration of 0.125% of ropivacaine can be a better alternative as it would decrease the total amount of the local anesthetic in continuous LPB.
Keywords: Lumbar plexus block, pain relief, ropivacaine, total hip arthroplasty
|How to cite this article:|
Murugesan A, Gurunathan D, Raghuraman M S, Indumathi D, Sundary M T. Comparison of 0.125% and 0.2% ropivacaine in continuous lumbar plexus block for postoperative analgesia after total hip arthroplasty. Indian Anaesth Forum 2021;22:143-8
|How to cite this URL:|
Murugesan A, Gurunathan D, Raghuraman M S, Indumathi D, Sundary M T. Comparison of 0.125% and 0.2% ropivacaine in continuous lumbar plexus block for postoperative analgesia after total hip arthroplasty. Indian Anaesth Forum [serial online] 2021 [cited 2023 Jun 4];22:143-8. Available from: http://www.theiaforum.org/text.asp?2021/22/2/143/326974
| Introduction|| |
Regional anesthesia has emerged with widespread acceptability among anesthesiologists worldwide. Postoperative pain relief can be provided by systemic opioid and nonopioid analgesic, neuraxial, and peripheral nerve block (PNB) techniques. A wide range of drugs are available for systemic analgesia, but the management of postoperative pain is still challenging for anesthesiologists. An effective postoperative analgesic regimen that is safer, efficacious, with an early recovery profile that provides early ambulation should be the goal.
Pain relief produced by lumbar plexus block (LPB) is one of the most effective methods to manage acute postoperative pain after hip surgeries., Bupivacaine has associated central nervous system and cardiovascular system toxicity with it. This led to the development of newer agents with less toxic potential such as ropivacaine and levobupivacaine. Ropivacaine has the greatest margin of safety among all the local anesthetics (LAs) available. It is nearly identical to bupivacaine with regard to the onset, duration, and quality of the sensory block with a lesser propensity for motor blockade as well as lesser toxicity profile., Continuous PNB provides better postoperative analgesia with lesser opioid-related side effects when compared to the opioid analgesia.
Although a few studies have evaluated the role of continuous LPB in hip arthroplasty,,,,,,, to our knowledge, only one study by Wilson et al. has compared the two different lower concentrations of ropivacaine (0.1% vs. 0.2%). Hence, our study was designed to compare the two lower concentrations of ropivacaine slightly different (0.125% vs. 0.2%) than the doses used in that study by Wilson et al. Besides, we have tested this comparison as a sole method of pain relief unlike Wilson et al., wherein they have provided patient-controlled opioid analgesia also.
| Materials and Methods|| |
After institutional ethical committee approval, this randomized, prospective, double-blind study was carried out between March 2019 and December 2019. Fifty American Society of Anesthesiologists I, II, and III adult patients of either sex between the ages of 18 and 70 years undergoing total hip arthroplasty (THA) surgery were enrolled after the informed consent process. Patients were randomized using block randomization in a 1:1 design into two groups. “Group 1” received 0.125% ropivacaine and “Group 2” received 0.2% ropivacaine concentrations [Flow chart 1].
Patients with infection at the nerve block site, coagulopathy or bleeding disorders, severely hypovolemic patients, those with raised intracranial pressure, sepsis, preexisting neurological deficit, demyelinating disorder, and revision hip arthroplasty surgery were excluded from this study.
A pilot study was conducted with ten patients, five patients in each group. Since the primary objective was to calculate the total amount of tramadol consumption, the mean dose of tramadol consumption was calculated. With two-tailed distribution, the mean dose of tramadol required in group 0.2% and 0.125% ropivacaine was 10 mg, 30 mg respectively. The sample size calculated: 25 cases in each arm. (difference =20 mg, effect size 0.9, level of significance 5%, power 80%, and allocation ratio 1:1).
The formula used for calculation of sample size by the software is: n = 2 × (Zα/2 + Zβ) × σ2/d2
- Zα/2 is the critical value of normal distribution at α/2 (confidence interval of 95%, with the level of significance 5%) =1.96
- Zβ is the critical value of normal distribution at β (for a power of 80%) =0.84
- σ2 = population variance (25)
- d2 is the difference which we want to deduct (20).
N = 2 × ([1.96 + 0.84] × [1.96 + 0.84]) × (25)(25)/(20)(20)
N = 2 × ([2.8] × [2.8]) × ((25) × (25))/(20) × (20) =9800/400 = 24.5
A detailed preanesthetic checkup was done in all patients and the Numerical Rating Scale (NRS) for grading the severity of pain was explained to all patients. Patients were kept nil per oral for at least 6 h. In the operation room, patient identity, consent forms, and fasting status were confirmed.
Under aseptic precautions, the subarachnoid blockade was given with plain 0.5% hyperbaric bupivacaine, dosage depending upon the patient characteristics. The induction of anesthesia was considered when at least the T10 dermatome was anesthetized. The sensory and motor blocks were assessed after the intrathecal injection at 1 and 2 min and then subsequently at 2 min intervals until surgical anesthesia was achieved. Sensory block was assessed by pinprick sensation using a hypodermic needle. Motor blockade was tested by modified Bromage scale (“0 = no block, 1 = inability to raise the extended leg, 2 = inability to flex the knee, and 3 = inability to flex ankle and foot”). The duration of sensory and motor blockade was defined as the interval from intrathecal administration to the point of complete resolution of the sensory block or to the point in which the Bromage score was back to zero, respectively. Heart rate, blood pressure, and oxygen saturation were recorded for every 5 min till the end of the surgery.
Surgery proceeded with the patient in the lateral position. Upon completion of the surgery, the LPB was performed with the patient in the same lateral position. Under all aseptic precautions, the landmarks, namely spinous process and iliac crest, were identified, and under sterile aseptic precautions using the nerve stimulator (Stimuplex® HNS 12 Nerve Stimulator, B. Braun), the nerve block cannula with a needle (Contiplex® Stim, B. Braun) was inserted perpendicular to the skin at 4 cm lateral to the midline at the level of the iliac crest. The nerve block cannula with the needle was advanced to a depth of 6–8 cm, at 1–1.5 mv, at a frequency of 2 Hz until quadriceps muscle contraction was visible. The voltage was brought down to find the contractions at 0.5–1 mv. Any contraction with voltage <0.5 mv indicates that the needle is intraneural and was withdrawn to place it correctly.
The LA solution was prepared according to the group allocation (0.125% or 0.2% of ropivacaine) by the trained staff nurse without revealing the concentration to the anesthesiologist performing the block. Under aseptic conditions, with the peripheral nerve stimulator guidance, 20 ml of LA was administered initially. This was followed by the insertion of the nerve block catheter of 20 G and fixed such that 5 cm of the catheter was in the psoas compartment beyond the noted cannula depth. Ten milliliters of LA was given through the catheter to ensure the optimal flow and hence a total of 30 ml of LA was given. The time of LA administration was noted. The patient was positioned supine and vital parameters were noted.
All patients received 1-g intravenous acetaminophen, every 8 h, as part of multimodal analgesia which was started in the postanesthesia care unit (PACU). Infusion of LA was started in PACU at 6 ml/h. The preparation of LA solution according to the group allocation was done by the staff nurse who would not involve in the monitoring of the parameters to maintain the blinding. The study period starts after the initiation of the infusion. Vital parameters were checked at regular intervals. For a breakthrough pain with NRS score more than or equal to 4, a repeat bolus dosage of 6 ml of LA was given, and the infusion rate increased to 8 ml/h. If the patient complains of pain with an NRS score of more than or equal to 4, even 15–30 min after the repeat bolus dosage, it was treated with an intravenous injection of tramadol 1 mg/kg. The patients were followed up at 3, 6, 9, 12, 18, and 24 h to assess the pain score during rest and movement, opioid consumption, LA consumption, and quality of sensory blockade up to 24 h postoperatively. Any side effects, if present, were documented. The sensory evaluation includes testing the patient's ability to detect the cold sensation using an alcohol swab at the anterior and lateral aspects of the thigh. It was graded using a three-level scale (0 = absent, 1 = decreased, and 2 = intact). The patient's pain was evaluated using the ten-point NRS (0 = no pain and 10 = worst imaginable pain). To assess the sedation secondary to opioid consumption, the Ramsay sedation scoring system was used (“anxious and agitated or restless, or both – 1; cooperative, oriented, and tranquil – 2; response to commands only – 3; exhibits brisk response to a light glabellar tap or loud auditory stimulus – 4; exhibits a sluggish response to a light glabellar tap or loud auditory stimulus – 5; and exhibits no response – 6”).
| Results|| |
Data analysis was carried out in SPSS version 25.0 (IBM, South Asia). Statistical analysis was done by applying the Chi-square test and Student's “t” test to analyze the data. P < 0.05 considered statistically significant. All LPBs were assessed and found to be functional preoperatively. Fifty patients were randomized. Twenty-five received ropivacaine 0.125% (Group 1) and 25 received ropivacaine 0.2% (Group 2). Demographic characteristics did not differ significantly [Table 1].
Quality of sensory block did not differ between the groups postoperatively. All the patients in Group 1 as well as Group 2 had score “0” (absent sensation) in the first 3 h after the surgery. This can be attributed to the combined effect of subarachnoid blockade along with lumbar plexus blockade. Furthermore, after 12 h in postoperative period, all the patients in both the groups had similar profiles in sensory blockade (score 1 – decreased perception of sensation) and did not show any difference between them which could be due to the stabilization of the LA infusion. The sensory scores were comparable at 6 and 9 h (P = 0.774 and 0.733, respectively). Total consumption of tramadol [Table 2] and NRS pain scores at rest as well as at movement [Table 3] and [Table 4] were comparable between the two groups.
The patient's ability to walk during physical therapy at 24 h was similar in both the groups.
The mean duration of infusion at a higher rate of infusion (8 ml/h) was 9.18 h in Group 1 and 9 h in Group 2 (P = 0.896). The total LA requirement included the initial bolus dosage and rescue bolus of LA, followed by infusion at a higher rate. In Group 1, the average consumption of ropivacaine was 238.80 mg with a standard deviation (SD) of 15.564, whereas in Group 2, it was 380.64 mg with a SD of 24.13. The two groups had a significant difference in total LA consumption (P = 0.0001). There was an insignificant difference in vital parameters between the groups. Furthermore, the sedation scores were insignificant between the two groups (P = 1.000).
One patient in the 0.2% ropivacaine group presented 10 days after the procedure with pain in the right lumbar region (on the side of surgery). On further evaluation, it was found that the patient developed a hematoma at the site of lumbar plexus blockade in the muscular plane. It was conservatively managed according to institution protocol.
| Discussion|| |
The purpose of our study was to determine if LPB infusion of 0.125% ropivacaine produces a similar quality of analgesia and early mobilization as do 0.2% ropivacaine. In our study, at 12 h in the postoperative period, all the patients in both the groups had similar profiles in the sensory blockade. Sixty-eight percent of the patients in Group 1 required rescue LA bolus when compared to 64% of the patients in Group 2, and the difference was statistically insignificant. The duration of time for which patients were maintained at a higher rate of ropivacaine infusion of 8 ml/h was also statistically similar (9 h in both the groups). The pain scores during rest and on movement up to 24 h were also similar between both the groups. The only significant difference in both our groups was concerning total LA consumption which was much lower in Group 1 than Group 2. Although the average tramadol consumption was greater in Group 1, it was not a clinically or statistically significant difference (P = 0.442). Wilson et al. also reported that there was no significant difference in sensory blockade between 0.1% ropivacaine and 0.2% ropivacaine infusions. These factors suggest that minor differences in concentration of perineural LA may not play a significant role in the quality of analgesia and mobilization.
Wilson et al. in their study reported that only about 21% in the 0.1% group and 25% in the 0.2% ropivacaine group needed an escalation in infusion rate from 7 ml to 9 ml. This is much lesser than what we observed in our study. This may be because, in that study, the patients were provided a choice of patient-controlled opioid analgesia and there was a chance that patients would have preferred opioids, compared to asking the nurse to increase the LA dosage. Hence, our study is unique in comparing the two lower concentrations of ropivacaine as a sole method. Furthermore, we have performed the LPB at the end of the surgery unlike before subarachnoid block in that study.
Continuous femoral block could affect the early ambulation when compared to the continuous LPB., Similarly, continuous epidural analgesia also compromises the early ambulation with adverse effects too. Ilfeld et al. have observed three incidences of falling of patients in their study in which they have used a continuous infusion of 0.2% ropivacaine in LPB for 4 days. Hence, we believe that 0.125% or 0.1% of ropivacaine might eliminate the chance of falling of patients if it is used for prolonged infusion.
We have not chosen the ultrasound-guided LPB because clear delineation of the lumbar plexus would not be possible in all cases. Karmakar et al. have also observed that identification of lumbar plexus was possible in two-third of the patients in their case series comprising 15 patients, whereas the needle position was confirmed in all cases by nerve stimulation. Recently, periarticular infiltration of LA has been compared with continuous LPB by Johnson et al. They concluded that LPB or periarticular infiltration of liposomal bupivacaine provided superior analgesia when compared with periarticular infiltration of ropivacaine.
In our study, patient satisfaction scores were not recorded. Although pain scores did not differ significantly between the two groups, estimation of patient satisfaction scores would have added more value to the interpretation of results. Individual difference in pain tolerance affects total anesthetic requirement. This bias could not be quantified.
| Conclusion|| |
We conclude that lumbar plexus blockade with 0.125% ropivacaine provides similar analgesia to that of 0.2% ropivacaine after THA surgery. The use of 0.125% concentration has the advantage of requiring a lower total dose of ropivacaine when compared to 0.2% and could be a better alternative.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]