Comparative Study Of 0.5% Hyperbaric Levobupivacaine, 0.75% Hyperbaric Ropi-Vacaine And 0.5% Hyperbaric Bupivacaine With Add On Fentanyl In Subarachnoid Block For Lower Limb Surgeries.

Spinal anaesthesia is widely preferred for lower limb orthopaedic surgeries because of its rapid onset, effective sensory blockade, reduced perioperative complications, and good postoperative analgesia. [1,2] Hyperbaric bupivacaine has traditionally been the most commonly used intrathecal local anaesthetic agent; however, it is associated with prolonged motor blockade and increased cardiovascular and central nervous system toxicity. [3,4-7] Levobupivacaine and ropivacaine, the pure S(-) enantiomers developed as safer alternatives, demonstrate lower cardiotoxicity and neurotoxicity while maintaining effective sensory blockade.[8,9] Levobupivacaine provides block characteristics similar to bupivacaine, whereas ropivacaine produces less intense motor blockade with faster recovery, making it useful for ambulatory and lower limb surgeries.[8,9] Addition of intrathecal fentanyl enhances sensory blockade and postoperative analgesia without significantly prolonging motor block. [2] However, limited studies have directly compared hyperbaric ropivacaine, hyperbaric levobupivacaine, and hyperbaric bupivacaine in spinal anaesthesia for lower limb surgeries. Therefore, the present study was undertaken to compare the sensory and motor block characteristics of 0.5% hyperbaric levobupivacaine with fentanyl (25 mcg), 0.75% hyperbaric ropivacaine with fentanyl (25 mcg), and 0.5% hyperbaric bupivacaine with fentanyl (25 mcg) in orthopaedic surgeries under subarachnoid block in terms of onset, highest sensory level, and duration of sensory and motor blockade.

Study design: Prospective, randomized, double-blind interventional study.

Study period: 12 Months

Place of study: Department of Anaesthesiology, Tertiary Care Teaching Hospital.

Study population: Adult patients aged 18–65 years, ASA physical status I–III, undergoing lower limb orthopaedic surgeries under subarachnoid anaesthesia.

Sample size: 195 patients.

Inclusion Criteria:

·         Age 18–65 years.

·         ASA physical status I–III.

·         Scheduled for lower limb orthopaedic surgeries under subarachnoid anaesthesia.

Exclusion Criteria:

·         Refusal for subarachnoid block.

·         Known allergy to local anaesthetic agents.

·         Coagulopathy.

·         Infection at the injection site.

·         Spinal deformity (e.g., scoliosis, kyphoscoliosis).

·         Pre-existing neurological disease.

·         Inability to comprehend sensory and motor block assessment.

·         Failed subarachnoid block requiring conversion to general anaesthesia.

Study Variable:

This prospective, randomized, double-blind interventional study was conducted in the Department of Anaesthesiology of a tertiary care teaching hospital, after obtaining approval from the Institutional Ethics Committee (vide approval number IEC/2023/145, Ref no DMCH/IEC/2023/287 Dated 15 December 2023). It was done according to the principles of the declaration of Helsinki, 2013 and Good Clinical practice guidelines. A total of 195 adult patients aged 18–65 years, belonging to ASA physical status I–III and scheduled for lower limb orthopaedic surgeries under subarachnoid anaesthesia, were included in the study. Patients refusing subarachnoid block , those with known allergy to local anaesthetic agents, coagulopathy, infection at the injection site, spinal deformities (scoliosis, kyphoscoliosis or similar deformities), pre-existing neurological disease, inability to comprehend sensory and motor block assessment, and failed subarachnoid block requiring conversion to general anaesthesia were excluded from the study.

Sample size was calculated using the formula:

where Z_αwas taken as 1.96 at 95% confidence interval and Z_βas 0.842 for 80% power. Based on the findings of Casati et al., the calculated sample size was 59 patients per group. To account for possible dropouts and exclusions, 65 patients were included in each group, making a total sample size of 195 patients.

 All patients underwent detailed pre-anaesthetic evaluation one day prior to surgery. Routine investigations including haemogram and coagulation profile were performed, and standard fasting guidelines according to ASA recommendations were followed. In the operating room, standard monitoring including non-invasive blood pressure, electrocardiography, and peripheral oxygen saturation was established and baseline parameters were recorded. Intravenous access was secured and preloading with intravenous fluids was initiated prior to administration of subarachnoid block.

Patients were randomly allocated into three groups using computer-generated randomization. Allocation concealment was done using sealed envelopes opened by an independent anaesthesiologist responsible for preparation of the study drug. Group B received 2.5 mL of 0.5% hyperbaric bupivacaine with fentanyl 25 mcg (0.5 mL), Group R received 2.5 mL of 0.75% hyperbaric ropivacaine with fentanyl 25 mcg (0.5 mL), and Group L received 2.5 mL of 0.5% hyperbaric levobupivacaine with fentanyl 25 mcg (0.5 mL) intrathecally. The total volume administered in all groups was 3 mL.

A designated anaesthesiologist prepared the study drug in a coded 5 mL syringe and handed it over to another anaesthesiologist administering the block, who remained blinded to the study medication. Under strict aseptic precautions and with the patient in sitting position, local infiltration was performed using 2 mL of 2% lignocaine. A 26-gauge Quincke spinal needle was inserted through the midline approach. After confirmation of free flow of cerebrospinal fluid, the study drug was administered intrathecally at a rate of 0.2 mL/s. Immediately after injection, patients were placed supine with the operating table maintained in a neutral position.

Haemodynamic parameters including heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and peripheral oxygen saturation were recorded at baseline, 2, 4, 6, 8, 10, and 15 minutes after administration of subarachnoid block and subsequently at 15-minute intervals. Sensory block was assessed bilaterally along the midclavicular line using pinprick method with a sterile 26G needle. Surgery was commenced after attainment of sensory block up to T10 dermatome.

The onset of sensory block was defined as the time from intrathecal injection to loss of pain sensation at T10 dermatome. Duration of sensory block was defined as the time interval between intrathecal injection and regression by two dermatomes from the highest sensory level achieved. Motor block was assessed using the Modified Bromage Scale at 2, 4, 6, 8, 10, and 15 minutes and subsequently at 15-minute intervals. The onset of motor block was defined as the time from intrathecal injection to attainment of Grade 1 motor block, while duration of motor block was defined as the time from intrathecal injection until return to Grade 0. Modified Bromage Scale grading was as follows: Grade 0 – full motor function; Grade 1 – unable to raise extended leg but able to flex knee; Grade 2 – unable to flex knee with preserved ankle movement; and Grade 3 – complete motor block.

Patients were monitored intraoperatively for hypotension, bradycardia, and hypoxemia. Hypotension was defined as systolic blood pressure below 90 mmHg or a reduction greater than 20% from baseline and was managed with intravenous fluids and ephedrine 6 mg boluses. Bradycardia, defined as heart rate below 60 beats/minute, was treated using intravenous atropine 0.6 mg. Hypoxemia, defined as peripheral oxygen saturation below 90%, was managed with supplemental oxygen and ventilatory support when required.

In the post-anaesthesia care unit, haemodynamic parameters along with sensory and motor block characteristics were monitored every 15 minutes until complete regression of both blocks. Postoperative pain assessment was performed using the Numerical Rating Scale (NRS), where 0 represented no pain and 10 represented worst imaginable pain. Pain assessment was initiated immediately upon arrival in the post-anaesthesia care unit and repeated hourly for the first six postoperative hours. Intravenous tramadol 100 mg was administered when NRS score exceeded 4, and the time to first analgesic request was documented.

The primary outcomes of the study were onset of sensory block and onset of motor block. Secondary outcomes included highest level and duration of sensory block and duration of motor block.

Data were summarized using mean ± standard deviation, median, range, frequencies, and percentages as appropriate. Normality of distribution was assessed using the Kolmogorov–Smirnov test. Quantitative variables were compared using the Kruskal–Wallis test followed by post hoc Tukey’s test where applicable. Categorical variables were analysed using chi-square test or Fisher’s exact test. A p-value <0.05 was considered statistically significant. Statistical analysis was performed using SPSS version 21 (SPSS Inc., Chicago, IL, USA).

Consort Flow Chart.

Table 1: Baseline characteristics of study participants

Table 2: Comparison of sensory block characteristics among study groups

Table 3: Comparison of motor block characteristics and duration of analgesia among study groups

Table 4: Comparison of adverse effects among study groups

Figure 2a: Comparison of Study Groups According to Onset of Sensory Block (Minutes)

Figure 2b: Comparison of Study Groups According to Duration of Sensory Block (Minutes)

Figure 3a:  Comparison of Study Groups According To Time Required For Onset of Motor Block (Minutes)

Figure 3b: Comparison of Study Groups According to Duration of Motor Block (Minutes)

FIGURE 4a: Trends Of Intra-Operative HR Values In Three Group

Figure 4b: Trends Of Intra-Operative Mean Arterial Pressure (MAP) Values In All Three Groups

A total of 195 patients were enrolled and randomized equally into three groups: Group B (hyperbaric bupivacaine with fentanyl), Group R (hyperbaric ropivacaine with fentanyl), and Group L (hyperbaric levobupivacaine with fentanyl), with 65 patients in each group. The participant recruitment and allocation process is illustrated in Figure 1.

The baseline demographic and clinical characteristics of the study population are summarized in Table 1. The three groups were comparable with respect to demographic profile, ASA grading, BMI, and duration of surgery, with no statistically significant intergroup differences observed (p > 0.05).

Sensory block characteristics among the study groups are presented in Table 2 Fig 2. The mean onset time of sensory block was comparable among the three groups, with no statistically significant difference (p = 0.194). However, duration of sensory block differed significantly among the groups (p = 0.008). Group B demonstrated significantly longer duration of sensory block compared to Group R (p = 0.003), while no significant difference was observed between Group B and Group L (p = 0.516). T6 was the most commonly achieved sensory level in all groups, and no statistically significant difference was observed in the maximum sensory level attained (p = 0.602).

Motor block characteristics and duration of analgesia are summarized in Table 3 Fig 3 . The onset of motor block was comparable among all groups (p = 0.301). Time to complete motor regression was significantly shorter in Group R compared to Group B and Group L (p = 0.001). Similarly, duration of analgesia was significantly shorter in Group R, whereas Groups B and L demonstrated comparable duration of postoperative analgesia.

Adverse effects and haemodynamic parameters are summarized in Table 4 and Figure 4, respectively. No statistically significant intergroup differences were observed with respect to incidence of hypotension, bradycardia, nausea/vomiting, or vasopressor requirement (p > 0.05). Haemodynamic parameters including heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure remained comparable among the three groups throughout the intraoperative and postoperative periods.

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