Total knee arthroplasty (TKA), as the most effective surgical method for the treatment of end- stage knee osteoarthritis¹. However, TKA is a highly painful operation, and nearly 80% of patients will have severe, or extreme pain after operation². Insufficient postoperative analgesia will affect the early rehabilitation training of patients, increase the incidence of perioperative joint stiffness and deep venous thrombosis, and increase the hospital stay time³. Therefore, optimal anesthesia and analgesic methods are vital for patients undergoing TKA.

There are many effective methods to relieve postoperative pain, including opioids consumption, epidural analgesia, peripheral nerve block, and periarticular infiltration analgesia^4,5. With the advent of ultrasonography (USG), adductor canal block (ACB) can be administered with a high success rate^6,7 . In recent years, ACB has been successfully used for postoperative pain control after knee surgery⁸. Nonetheless, the duration of single ACB analgesia is limited, and continuous ACB has the risk of catheter displacement, dislodgement, and postoperative falls⁹. Therefore, it can be a choice to prolong the analgesic time of the nerve block and strengthen the analgesic effect through local anesthetic adjuvants in single ACB. Various adjuvants have been reported to be effective to improve the quality of block but it is unclear that which drug is the best adjuvant for local anesthetics¹⁰.

Nalbuphine is a derivative of 14-hydroxymorphine which is a strong analgesic with mixed kagonist and μ antagonist. The analgesic effect of nalbuphine has been found to be equal to the analgesic effect of morphine but unlike it has a ceiling effect on respiration.

Nalbuphine has the potential to maintain or even enhance μ-opioid based analgesic effect while simultaneously mitigating the μ-opioid side effects [11]. Nalbuphine is cardiac stable with onset of action between 2 and 3 min, duration of action of 3-6 h and has minimal side effects in the dose of 0.2-0.4 mg/kg [12, 13]. Because of its safety profile, nalbuphine can beused for pain management in children with burns, neoplastic or haematological diseases.

Despite its known benefits for pain control, nalbuphine has not been studied extensively for its effects as an adjuvant to local anesthetics during brachial plexus blocks. Hence, this study was undertaken to evaluate the effects of Nalbuphine as an adjuvant for Ropivacaine in patients undergoing Total knee replacement surgery with respect to duration of postoperative analgesia, duration of postoperative ambulation and adverse effects.

After obtaining the Institutional Ethical Committee clearance and written informed consent from all patients, the study was conducted.

Sample size: Since we didn’t find any suitable parameter from previous similar studies, we haveused Cohen’s realistic range of Δ , where Δ is Effect size , we used Δ as 0.8 and calculated sample size as 15 each in 2 groups as detailed below: [14]

Total sample size = N

N= 2(Z1-α/2 +Z1-β)2 /𝛥2 + (Z1-α/2)2/4

Where Z1-α/2 is standard error associated with the chosen level of significance withα=50% and confidence interval = 95%

Z1-α/2 =1.96

Where Z1-β = 0.842

Where Δ is effect size, we used as 0.8

Cohen (1998) suggests a realistic range of Δ is from 0.1 to 1.0. A small effect, that is stringent criterion, might be Δ=0.2, a moderate one Δ=0.5 and a large effect that is a liberalcriterion, Δ=0.8.9

N = 2 (7.84) /(0.8)2 + (1.96)2/4 = 24.532 + 0.9604

=25.49 ~ 26

A dropout rate of 10% will be considered Sample size = N + 10% of N

=26+2.6 =28.6

Total sample size will be approximated to 30.

1. Inclusion Criteria:
2. Patients scheduled for elective TKR surgery with American society of anesthesiologist (ASA) Physical status grade I and II.
3. Patient willing to give informed
4. Patients of age group 18-65 years
5. Exclusion Criteria:
6. Known allergy to study drugs
7. Local infection at site
8. Patient in whom nerve block could not be performed as per methodology

METHOD OF COLLECTION OF DATA

Patients admitted to Chamarajanagar Institute of Medical Sciences Hospital, Chamarajanagar undergoing elective unilateral Total knee replacement under spinal Anaesthesia were included in the study. Clearance from the institutional ethical committee was taken before starting the study. Study participants were included in the study by Purposive Sampling technique.

Written informed consent was taken from the study participants before collecting the data. A pre-tested, semi-structured questionnaire was used to collect information on socio-demographic variables and clinical history by interview method. Relevant Laboratory and Radiological investigations were done. Patients were preoperatively assessed, appropriate investigations were done and optimized for surgery. Once patient shifted to operation theatre, patient was connected to multipara monitors and the following parameters like SpO2, electrocardiogram, non-invasive blood pressure were monitored to all patients on their arrival to operation theatre. Once TKR surgery was done, Adductor canal block was performed using ultrasound guidance. 30 patients were randomly allocated into two groups of 15 each by computer generated randomized number. Group R recieved19ml of ropivacaine (0.375%) +1ml normal saline. Group RN received 19ml solution of Ropivacaine (0.375%) with 1ml (10mg) Nalbuphine. Both the patient and investigator were blinded. The person who is not involved in the study prepared the drug mixture for the study groups. The duration of postoperative analgesia was assessed using VAS score.

Statistical Analysis

The data was collected and compiled in MS Excel. Descriptive statistics has been used to present the data. To analyse the data SPSS (Version 26.0) was used. Significance level was fixed as 5% (α = 0.05. Qualitative variables are expressed as frequency and percentages and Quantitative variables are expressed as Mean and Standard Deviation. To compare the mean values between groups, student t-test was used and to compare the proportion between the groups, chi-square test was used.

The mean age of the study participants in the Group R and RN were found to be 54.47+9.44 and 54.27+8.07 years. 60% of the study participants in the Group R were found to be females and 60% of the study participants in the Group RN were found to be males.

53.3% and 60% of the study participants in Group R and RN were found to be ASA grade II.The association was not found to be statistically significant between age, gender, ASA grade and the 2 groups of study participants. The mean SBP of the study participants in the Group R and RN were found to be 130.53+11.47 and 134.80+10.52 mmHg. The mean DBP of the study participants in the Group R and RN were found to be 78.07+5.53 and 77.47+4.80 mmHg. The association was not found to be statistically significant between Blood pressure and the 2 groups of study participants (Table 1). The pulse rate of group RN was found to be higher than group R after adductor block, but statistically significant differences were not found along the different time periods (Figure 1). The mean arterial pressure and respiratoryrate are between the Group R and Group RN were comparable with each other after adductor canal block without any statistical significance (Figure 2 & 3).

The mean duration of sensory block of the study participants in the Group R and RN were found to be 306.67 minutes and 398.67 minutes. P value is 0.000 (p<0.05) which is statistically significant. The duration of sensory block was found tobe higher in the Group RN when compared with Group R. The association was found to be statistically significant between the duration of sensory block and the 2 groups of study participants (Table 2). The pain was assessed by VAS , Score of 4 in group RN were 14 members compared to group R were 7 members . Score of 5 in group RN was 1 member compared to group R was 8 member. ‘p’ value is 0.007 ( p<0.05) which is statistically significant. (Table 2)

TABLE 1: PATIENT CHARACTERISTICS

Figure 1: Pulse rate along different time periods

Figure 2: Mean arterial pressure along different time periods

Figure 3: Respiratory rate along different time periods

TABLE 2: POST-OPERATIVE FOLLOW-UP

Mean distribution of analgesic duration between two groups (N=30)

TABLE 3: Distribution of participants in groups based on VAS score (N= 30)

#Chi- square tests

Figure 4: Mean time duration of analgesia between two groups (N= 30)

Figure 5: Distribution of participants between two groups based on VAS score

Postoperative pain is often overlooked with up to 70% of patients reporting moderate to severe pain following surgery. Pain control is of prime importance in improving the quality of patient care. Regional nerve block techniques offer superior postoperative pain relief and facilitates early ambulation and discharge. Ultrasound guided blocks enables accurate placement of needle thereby improving the success rate and it also reduces the complications due to inadvertent injury to vital structures in landmark based techniques.

Acute postoperative pain following Total Knee Arthroplasty is maximum during the first 24 hours. Various modalities have been adopted to reduce this post-operative pain with NSAIDs, parenteral opioids, central neuraxial analgesia, femoral nerve block, Adductor Canal Block and Local infiltration analgesia with varying results. Among these techniques Adductor canal block is effective and easy to perform with least complications.

We conducted this randomized prospective study to compare the efficacy of Nalbuphine as an adjuvant to Ropivacaine using USG guided ACB block in providing Postoperative pain relief and improving functional outcomes in patients undergoing Total knee arthroplasty done under spinal anesthesia.

In this study we planned to test the hypothesis that Nalbuphine as adjuvant to Ropivacaine using USG guided ACB block would provide superior postoperative analgesia without having any negative impact on the functional outcome in comparison with Ropivacaine alone.

Saphenous nerve, primarily a sensory nerve, is the main nerve that is blocked in the adductor canal at the level of midthigh. Nerve to vastus medialis, medial femoral cutaneous nerve, obturator nerve (articular branches) and medial retinacular nerve also transverse through the adductor canal and have a motor component. Ropivacaine is less lipophilic than Bupivacaine and less likely to penetrate large myelinated fibres. Theoretically, Ropivacaine have lesser motor blockade in ACB, and therefore there would be better ambulation after surgery. We compared the postoperative analgesia between Ropivacaine and Ropivacaine with Nalbuphine using USG guided Adductor canal block over a period of 12 hours. In addition to time of postoperative analgesia, we compared the early mobilization and any side effects associated with drugs. So the present study was undertaken to compare the duration of postoperative analgesia between Ropivacaine and Ropivacaine with Nalbuphine using USG guided ACB. In our study 30 patients were posted for elective TKA surgeries of less then 3 hours duration under spinal anesthesia. As far as ASA physical status was concerned, ASA PS I and II patients were included in the study. After assessing the level of block TKA was done using standard surgical method and use of thigh tourniquet. At the end of the surgery, the patients were given USG guided Adductor canal block based on groups allocated by random numbers.

Group R patients received USG guided ACB using Injection Ropivacaine 0.375% with 1ml normal saline. Group RN patients were given USG guided ACB using Ropivacaine 0.375% with 10mg Nalbuphine. The primary outcome measure that was compared the analgesic duration between both the groups, was the pain scores graded by Visual Analogue Score. Nalbuphine as an adjuvant to Ropivacaine is considered better as prolonged duration of postoperative analgesia, Early mobilization with no functional limitations.

David H Kim et al. compared Adductor canal block with Femoral nerve block for postoperative analgesia after elective TKA surgeries, ACB pain scores at post anesthesia score 6 to 8 hours 1.7 ± 1.9 and FNB score of 0.9±1.8. No side effects in both groups. Post anesthesia dynamometer reading post anesthesia 6 to 8 hours 15.8±7.6 in ACB and 16.2±10.3 in FNB group. They concluded that ACB exhibited early relative sparing of Quadriceps strength and motor recovery was early which helped patients for early mobilization.^[15]

Kampitak W, Tanavalee et al. compared Adductor canal block with Local infiltration Analgesia (LIA) on postoperative analgesia and functional outcome after Total knee arthroplasty. The mean VAS at 6,12,18 postoperative hours in ACB were lower than with LIA group with difference of 1.21 (95% CI=-2.31 to to - 0.1,p=0.034), 1.51(95% CI=-2.76 to -0.27, p=0.018) and 1.4 (95% CI = -2.45 to -0.34, p=0.01) . They concluded that Single injection ACB with multimodal analgesia for TKA was associated with greater reduction of morphine consumption than single injection Local infiltration analgesia. ACB provides superior analgesia and early mobilization after TKA than LIA.^[16]

we concluded that the addition of Nalbuphine as an adjuvant to Ropivacaine after unilateral total knee replacement using ultrasound-guided Adductor canal block prolongs the duration of postoperative analgesia with early ambulation and no adverse effects.

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