The severe pain seen so frequently after orthopaedic surgery is largely a result of the nature of the surgical procedure, which often involves significant muscle and skeletal tissue repair or reconstruction. In addition, many patients who undergo orthopaedic surgery have underlying chronic (persistent) pain, which, if not optimally treated preoperatively, can complicate, and add to the complexity of postoperative pain management [1].

The adverse effects of poorly managed post-operative pain are numerous and can be far-reaching for the orthopaedic patient. On the most basic level, severe pain can diminish the ability to accomplish postoperative goals, such as ambulation and participation in physical therapy, that are crucial to recovery after orthopaedic surgery. The link between poorly managed acute postoperative pain and increased long-term morbidity and mortality further underscores the consequences of poorly managed pain and the importance of providing the best possible pain control in these patients [2].

Four nerves the saphenous, obturator, sciatic, and vastus medialis are blocked by the four-in-one block. For knee and below-knee procedures, it may make things easier and result in greater postoperative analgesia. With this block, the sciatic nerve distribution can be anaesthetized postoperatively after knee procedures while the patient is lying supine [3-4].  

The main advantages we have observed in our practice are easy to perform in supine position (even without frog leg position), no need for separate injection or position change to block the sciatic nerve, relatively safer in experienced hand, good choice for post-op analgesia in below knee surgeries, predominantly sensory blockade in the distribution of sciatic nerve.

We hypothesised that 0.125% bupivacaine with two different doses of dexmedetomidine 0.5µg/kg and 1µg/kg may have different duration of analgesic effect when administered in ultrasound guided 4-in-1 block. Since this block is a relatively new block and only a couple of studies are available in literature, it would be worthwhile to compare the Duration of analgesia of 4-in-1 block with bupivacaine in combination with dexmedetomidine in two doses.

Aım and Objectıves

To compare the Duration of analgesia in ultrasound guided 4-in-1 nerve block with Bupivacaine in Combination with Dexmedetomidine in Two Doses for knee and below knee orthopaedic surgeries.

• Study Area: Department of Anaesthesiology, Dr. R.P.G.M.C. Kangra at Tanda, Himachal Pradesh, India

• Study Population: All consecutive patients in the age group 18-60 years including both genders scheduled for knee and below knee surgery under subarachnoid block (SAB) were enrolled for this study after obtaining written informed consent

• Study Duration: After approval by Institutional Ethics Committee(IEC), this prospective, randomized, double blinded, study was carried out over a period of 18 months including data collection, data organization, presentation, data analysis and data interpretation

• Sample Size: All patients within this duration and fulfilling our inclusion criteria were included in the study. The patients were divided into two groups -group A and group B. For each group, 50 patients were evaluated after randomization

Inclusion Criteria: ASA grade Ⅰ and Ⅱ patients scheduled for knee and below knee surgery under SAB with expected duration of 2 hours were intended in the current study

• BMI 18.5-29.9Kg/m²

Exclusion Criteria

• Patient’s refusal for spinal anaesthesia or 4- in -1 block

• Patients with anatomical deformities

• Patients with coagulopathies and bleeding disorders

• Patients with hypersensitivity to study drugs.

• Patients on anticoagulants

• Local infection at the site where needle for block is to be inserted

• Patients with known bradyarrhythmia, heart block, significant cognitive impairment

• Failure of spinal anaesthesia

Study Design

It was a prospective, randomized, double-blindstudy. The patients undergoing knee and below knee surgery were randomly divided into two groups (A and B). Randomization was achieved by computer-generated random number table. The randomization group assigned was enclosed in a sealed opaque envelope to ensure concealment of allocation sequence. After shifting the patient inside operation theatre, sealed envelope was opened by anaesthesiologist not involved in the study to prepare the drug solution according to allocation. The drug solution made was then made and handed over to the team member giving the block.

Methodology

The study commenced after obtaining institutional scientific review and protocol committee, ethics committee approval and written informed patient’s consent.

The enrolled patients, after fulfilling all the inclusion and exclusion criteria, were divided into 2 groups:

• Group A: received 29ml of 0.125% bupivacaine with 0.5µg/kg dose of dexmedetomidine (1 ml) making it to a total 30ml solution, in USG guided 4-in-1 block

• Group B: received 29ml of 0.125% bupivacaine with 1µg/kg dose of dexmedetomidine (1 ml) making it to a total 30ml solution, in USG guided 4-in-1 block

Anaesthetic Procedure

Pre-anaesthetic assessment was done one day prior to surgery. All patients were explained about the procedure, advantages, and risks of the procedure. The patients were educated about the 11-point Verbal Rating Scale (VRS) where 0 is no pain and 10 is worst imaginable pain. Thereafter written consent was taken and clinical details were recorded in a predesigned proforma.

All the patients were kept nil orally for 8 hours before surgery and pre-medicated with tablet alprazolam 0.25mg and tablet ranitidine 150mg the night before surgery and 2 hours before surgery with a sip of water. In the operation theatre, an 18-gauge intravenous (IV) cannula was secured followed by 0.9% sodium chloride (normal saline [NS]) infusion. After establishing standard anaesthesia monitoring, baseline parameters such as heart rate (HR), non-invasive blood pressure and peripheral oxygen saturation were recorded. Patients were given SAB after cleaning and draping, in sitting position using 26-gauge Quincke spinal needle at L3–L4 interspace with 3.0ml 0.5% hyperbaric bupivacaine after ensuring free flow of cerebrospinal fluid. After confirmation of adequate level (T6) the surgeon was allowed to proceed with thesurgery. All patients were monitored intraoperatively for systolic, diastolic, mean blood pressure, heart rate, and oxygen saturation. Any hypotension episode (defined as a reduction in mean arterial blood pressure> 30% of baseline) was treated with injection ephedrine 6 mg bolus and episodes of bradycardia (HR < 50 beats/min) was treated with injection atropine 0.02mg/kg. After completion of surgery, the patients were shifted to PACU and monitored for the regression of sensory block to T₁₀ level, following which they were given the ultrasound guided 4-in-1 nerve block.

Procedure of the Block

The patient was positioned in supine position with the ipsilateral leg kept in external rotation, slight abduction and knees slightly flexed (frog leg position). The medial femoral condyle wasmarked.

A linear high frequency ultrasound probe, ultrasoundSonositeMicromaxx® (Sonosite®, Bothell, WA, USA) wasused. After skin disinfection with povidone iodine, sterile drapes were applied.The linear probe (8–12 Hz) covered with sterile plastic sheath and with sufficient application of sterilised gel wasplaced over the femoral condyle and vastus medialis muscle identified and scanned proximally. The vastus and sartorius intersection (antero-medial intermuscular septum) were identified and the probe was taken proximal till the superficial femoral artery appears in the adductor hiatus. The probe was then slid slowly proximally till the descending genicularartery branching from superficial femoral artery is visualized in the hiatus. This point was the injection point which is 8-10 cm above the femoral condyle. Under all aseptic precautions, a22-gaugeechogenic needle was used by an ultrasound-guided in-plane from lateral to medial side under to reach perivascular region and after negative aspiration, the test drug was injected to spread around the femoral artery and also in a plane to push the Sartorius muscle up and hence blocking four nerves namely saphenous, obturator, sciatic and nerve to vastus medialis.

Subsequently, each patient was observed for pain, vitals and side effects at hourly intervals as mentioned in the proforma (i.e., 0, 1, 2, 4, 6, 12, 18 and 24 hours) for 24 hours by an anaesthesiologist blinded to group assignment. For the first 24 hours, the protocol for postoperative analgesia consisted of standard orders for injection i.v paracetamol 1gm i.v for VAS > 4followed by injection i.v. diclofenac aqueous solution 1.5mg/kg if pain not relieved with the former. For breakthrough pain, patients were treated with injection i.v. tramadol 0.5mg/kg as and when required. The patients were evaluated for the time to request for first rescue analgesia and Total pain free interval. Time to first rescue analgesia was measured from the time after giving 4 in 1 block to the administration of 1^st rescue analgesic. Total pain free interval was measured from the time after giving SAB to the administration of 1^st rescue analgesic.

Statistical Analysis

The data were recorded into Microsoft® Excel workbook 2019 and exported into SPSS v21.0 (IBM, USA) for statistical analysis. Categorical variables were expressed as frequency, percentage and compared using Chi square test. Quantitative variables were expressed as mean, standard deviation and compared using Student t-test.  p-value <0.05 was considered significant.

Ethical Justification

The study was approved by IEC (HFW-H/DRPGMC/Ethics/2019/221; dated 21/12/2019) at Dr. RPGMC Kangra at Tanda. All the patients were included after they agreed to give their consent.

The present study was aimed to compare the Duration of analgesia in ultrasound guided 4-in-1 nerve block with Bupivacaine in Combination with Dexmedetomidine in Two Doses for knee and below knee orthopaedic surgeries. After Institutional Ethics Committee approval and written informed consent, one hundred and eight patients of ASA I and II category, aged between 18–60 years, were recruited in the study. Eight patients, however, were excluded from the study as per the exclusion criteria. Fifty patients in each group completed the study successfully (Figure-A). 

A total of 100 patients were randomly divided into 2 groups. The groups made have been elaborated as following:

• Group A: 29ml of 0.125% bupivacaine with 0.5µg/kg dose of dexmedetomidine (1ml) making it to a total 30 ml solution, in USG guided 4 in 1 block

• Group B: 29ml of 0.125% bupivacaine with 1µg/kg dose of dexmedetomidine (1ml) making it to a total 30 ml solution, in USG guided 4 in 1 block

In this study, mean age of the participant was 40.64±11.44 years in Group A and 40.12±12.55 years in Group B ranging from 18 years to 60 years. Maximum participant in Group A (n = 18) aged between 41 and 50 years and in Group B (n = 17) were aged between 30 and 40 years. Only 10 participants aged below 30 in both the groups. The study population comprised of 36 males in Group A and 31 males in Group B and 14 females in Group A and 19 females in Group B. There was no significant difference of gender between both groups (p = 0.287) (Table 1).

Table 1: Distribution of Participants According to Socio-Demographic Variables

Table 2: Distribution Of Participants According to ASA Grades And Mean Duration Of Surgery

Table 3: Duration of Analgesic Effect

It was defined as the time interval between the pain free periods after administration of the spinal block to the first rescue analgesic administration. Duration of post-operative analgesia in group A and group B was 666.48±82.45min and 801.96±92.97min respectively. In this study, duration of total pain free period was significantly longer in group B in comparison to group A (p = 0.0001) (Table -3).

Local anaesthetics provide analgesia for limited period of time when used as single injection. To extend the duration of analgesia beyond the operating time, various methods have been used with the aim of prolonging the local anaesthetic action, like continuous infusion of local anaesthetics via indwelling catheters and use of various adjuvants with local anaesthetics [5-6]. 

More and more research into the topic has been made possible by the transition from central neuraxial blocks, such as combination spinal epidural, to regional blocks, such as the femoral, sciatic, adductor, and combined femoral and sciatic for targeting pain-free TKA. As numerous nerves (genicular nerves) from the femoral, obturator, and sciatic nerves supply the knee joint, a thorough yet straightforward method is required for full analgesia postoperatively.

Recently, Roy et al. have proposed technique of ultrasound-guided 4-in-1 block for knee and below knee surgeries.³ This technique has not been studied much in detail. Hence, we compared the Duration of post-operative analgesia of ultrasound-guided 4-in-1 block with bupivacaine in combination with dexmedetomidine in two doses for knee and below knee orthopaedic surgeries for postoperative analgesia.

We have used 0.125% bupivacaine as the use of large doses and high concentrations of local anaesthetics are directly related to higher rates of nerve damage and systemic toxicity [7]. Limiting the dose and concentration of local anaestheticmay reduce this risk. Moura et al. reported that lower doses of bupivacaine is associated with a low risk of motor block and a favourable side effect profile, enabling early patient discharge [8]. 

After ethics approval and patients’ informed consent, we conducted a randomized, prospective study in hundred patients ASA I-II status of either gender in the age group of 20-60 years, scheduled for knee and below knee surgeries under subarachnoid block were divided in two groups. Group A received 29 ml of 0.125% bupivacaine with 0.5µg/kg dose of dexmedetomidine (1ml) making it to a total 30ml solution and group Breceived 29ml of 0.125% bupivacaine with 1µg/kg dose of dexmedetomidine (1ml) making it to a total 30ml solution.

In our study, duration of post-operative analgesia in group A and group B was 666.48±82.45min and 801.96±92.97 min respectively. In this study, duration of analgesic effect was significantly longer in group B in comparison to group A (p = 0.0001).The analgesic efficacy of bupivacaine in combination with dexmedetomidine in peripheral nerve block has been studied in literature and our study also shows similar analgesic benefits in 4 in 1 nerve block .We have no comparable studies due to the recent discovery of our block under study but our results show consistency with the results of Agarwal et al. (2014) who compared the effects of adding dexmedetomidine to a 30 ml solution of 0.325% bupivacaine in supraclavicular brachial plexus block.⁹ Patients were divided into two groups, the control group S and the study group SD. In group S (n = 25), 30ml of 0.325% bupivacaine  + 1ml normal saline; and in group SD (n = 25), 30 ml of 0.325% bupivacaine  + 1ml (100μg) dexmedetomidine were given for supraclavicular brachial plexus block using the peripheral nerve stimulator.The mean duration of analgesia for group SD was 776.4 ± 130.8min, it was 241.4±51.2min for group S. DOA was significantly longer in group SD than group S (p<0.001).Palsule et al. (2017) evaluated the effect of dexmedetomidine as an adjuvant to 0.25% bupivacaine in supraclavicular block [10]. Patients were assigned to one of the following groups alternatively: Group C received BPB with bupivacaine 0.25% (34ml) + normal saline 1ml. Group D received BPB with bupivacaine 0.25% (34ml) + dexmedetomidine 1μg/kg.Duration of analgesia (735.6 vs. 423.6 min, p< 0.001) was longer as compared to control group.

A plethora of studies have shown that α2 agonists, either alone or in combination with local anaesthetics or opiate narcotics, are highly effective in the treatment of short-term pain.Duration of analgesia achieved by dexmedetomidine may be due to block of the hyperpolarization-activated cation current (Ih current) which prevents the nerve from returning from a hyperpolarized state to resting membrane potential for subsequent firing and generation of a new action potential. Ray et al. (2020) compared two doses of dexmedetomidine with local anaesthesia in the brachial plexus block to find out the effectiveness of analgesia and other effects. All patients were separated into two groups, namely Group A (0.5μg/kg dexmedetomidineadded to 20mL of 0.25% bupivacaine) and Group B (1.0μg/kg dexmedetomidineadded to 20mL of 0.25% bupivacaine) [11]. The VAS score was always lesser in Group B using a higher dose of dexmedetomidine up to 12 hours.

The study concluded that duration of total pain free period was significantly longer in group B in comparison to group A. Hence, duration of analgesic effect was significantly more with the use of 1µg/kg dexmedetomidine as an adjunct to 0.125% bupivacaine.

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