Subarachnoid block (SAB) remains one of the most widely employed anaesthetic techniques for infra-umbilical procedures owing to its rapid onset, profound sensory and motor blockade, and favorable safety profile. For day-care and short-stay surgeries, an ideal spinal anaesthetic must provide dense yet reversible block with stable hemodynamics, minimal toxicity, and prompt recovery facilitating early ambulation and discharge.[1] Among local anaesthetics, Lignocaine, Bupivacaine, Levobupivacaine, and Ropivacaine have been used intrathecally. With the discontinuation of intrathecal Lignocaine due to transient neurologic symptoms, Bupivacaine became the standard agent because of its prolonged action. However, the racemic mixture of Bupivacaine contains equal parts of the dextro- and levo-isomers, with the former associated with severe cardiotoxic and neurotoxic events. This limitation prompted the development of newer long-acting amide agents-Levobupivacaine (the pure S-enantiomer of Bupivacaine) and Ropivacaine (the S-enantiomer of Propivacaine)-which offer comparable efficacy with improved safety.[2] Levobupivacaine produces sensory and motor blockade characteristics similar to bupivacaine but with less depression of cardiac contractility and fewer central nervous system side effects. Its higher protein binding (≈97 %) and stereoselective affinity for sodium channels contribute to its lower free plasma concentration and reduced systemic toxicity. Ropivacaine, with slightly less lipid solubility, preferentially blocks sensory fibers over large motor fibers, resulting in a differential block advantageous for early mobilization and postoperative analgesia.[3] A key determinant of intrathecal drug spread is baricity-the relative density of the solution compared to cerebrospinal fluid. Hyperbaric solutions, created by adding dextrose, allow more predictable distribution influenced by gravity and patient position, minimizing inter-individual variability. Until recently, both Levobupivacaine and Ropivacaine were available only as isobaric preparations, requiring manual addition of dextrose under sterile conditions. The introduction of commercially prepared hyperbaric Levobupivacaine 0.5% and hyperbaric Ropivacaine 0.75 % has enabled standardized, ready-to-use formulations with consistent performance.[4] Previous studies demonstrate that hyperbaric Levobupivacaine achieves a faster onset and longer duration of sensory and motor block than hyperbaric Ropivacaine, while both maintain hemodynamic stability and low incidence of adverse events[5]. Nevertheless, comparative evidence in infra-umbilical surgery patients remains limited. Hence, this prospective randomized study was undertaken to evaluate the clinical efficacy and safety of hyperbaric Levobupivacaine 0.5% versus hyperbaric Ropivacaine 0.75% administered intrathecally for infra-umbilical surgical procedures, focusing on sensory-motor block characteristics, hemodynamic responses, and peri-operative complications. Aim To compare the clinical efficacy and safety of hyperbaric Levobupivacaine 0.5 % and hyperbaric Ropivacaine 0.75 % in subarachnoid block for infra-umbilical surgeries. Objectives 1. To evaluate and compare the onset, level, and duration of sensory and motor blockade produced by the two study drugs. 2. To assess intra-operative hemodynamic stability and requirement of first rescue analgesia. 3. To observe and compare any adverse effects or complications associated with each drug.

Source of Data: Patients admitted to the Department of Anaesthesiology, Chamarajanagar Institute of Medical Sciences (CIMS), Chamarajanagar, scheduled for elective infra-umbilical surgeries under subarachnoid block. Study Design: A prospective, randomized, double-blinded, comparative study. Study Duration: June 2023 – December 2024 (18 months). Sample Size: 70 patients (35 per group). Inclusion Criteria: • ASA physical status I and II. • Age 18–60 years. • Patients consenting to participate and undergoing elective infra-umbilical surgery under SAB. Exclusion Criteria: • Refusal for spinal anesthesia. • Local infection at puncture site, spine deformity, or raised intracranial pressure. • Known allergy to study drugs. • Coagulopathy, severe cardiac, renal, or hepatic disease. • Pregnancy or ASA > II. Procedure and Methodology: After institutional ethical approval and written informed consent, patients were randomized using a computer-generated sequence and sealed opaque envelopes into two equal groups: Group HL: 3 mL of 0.5 % hyperbaric Levobupivacaine (15 mg). Group HR: 3 mL of 0.75 % hyperbaric Ropivacaine (22.5 mg). Under strict asepsis, lumbar puncture was performed at the L3–L4 interspace in the sitting position using a 25 G Quincke spinal needle. After confirming free CSF flow, the study solution was injected over 10 seconds. The anaesthesiologist recording observations and the patient were both blinded to the drug administered. Monitoring: Baseline heart rate, systolic, diastolic and mean arterial pressures, respiratory rate, and SpO₂ were recorded and repeated every 2 minutes for 10 minutes, every 5 minutes for 30 minutes, then every 10 minutes until completion of surgery. Assessment Parameters: • Sensory block: Time to reach T10 dermatome (pin-prick method), maximum height achieved, and two segment regression. • Motor block: Evaluated using the Modified Bromage Scale (0–3). Onset was time to Bromage 3; duration until return to 0. • Duration of analgesia: Time from injection to first request for rescue analgesia (VAS ≥ 3). • Hemodynamic changes and adverse effects (hypotension, bradycardia, nausea, vomiting, shivering, PDPH) were recorded and treated appropriately. Sample Processing / Drug Preparation: Drugs drawn by an independent anaesthesiologist not involved in data recording; identical syringes ensured blinding. Hyperbaric formulations were used directly without dextrose addition. Data Collection and Statistical Analysis: All data were compiled in a pre-structured proforma. Statistical analysis was performed using SPSS v25. Quantitative variables were expressed as mean ± SD and compared using t-test; qualitative variables were analyzed using Chi-square/Fisher’s exact test. p < 0.05 was considered statistically significant.

Table 1: Baseline profile and safety comparability (N = 70; Group HL n=35, Group HR n=35) Measure Group HL (mean ± SD or n/%) Group HR (mean ± SD or n/%) Effect & test 95% CI p-value Age (years), Mean (SD) 38.54 ± 11.43 42.74 ± 9.89 Mean diff = -4.20; independent t -9.21 to +0.81 0.105 Male sex, n (%) 27 (77.1%) 22 (62.9%) RR = 1.23; χ²=1.70 0.90 to 1.68 0.192 ASA I, n (%) 25 (71.4%) 19 (54.3%) RR = 1.32; χ²=2.20 0.91 to 1.90 0.138 Height (cm), Mean (SD) 167.83 ± 6.98 166.37 ± 7.90 Mean diff = +1.46; t -2.03 to +4.95 NS Weight (kg), Mean (SD) 66.46 ± 6.10 69.43 ± 6.65 Mean diff = -2.97; t -5.96 to +0.02 NS Table 1 presents the demographic and baseline clinical characteristics of the 70 patients enrolled in the study, divided equally between the hyperbaric levobupivacaine (HL) and hyperbaric ropivacaine (HR) groups. The mean age of participants was 38.54 ± 11.43 years in the HL group and 42.74 ± 9.89 years in the HR group, showing no statistically significant difference (p = 0.105; 95% CI = -9.21 to +0.81). Male predominance was observed in both groups-77.1% in HL versus 62.9% in HR-but the difference was not significant (p = 0.192). Similarly, the proportion of ASA I patients was higher in the HL group (71.4%) compared to HR (54.3%), but this difference did not reach statistical significance (p = 0.138). Anthropometric parameters such as height (167.83 ± 6.98 cm vs 166.37 ± 7.90 cm) and weight (66.46 ± 6.10 kg vs 69.43 ± 6.65 kg) were comparable (p > 0.05). Figure 1 Table 2: Onset, level, and duration of sensory & motor blockade (N = 70) Outcome Group HL (mean ± SD or n/%) Group HR (mean ± SD or n/%) Effect & test 95% CI p-value Sensory onset to T10 (min) 2.87 ± 0.46 4.153 ± 0.336 Mean diff = -1.283; t -1.47 to -1.09 <0.001 Two-segment regression (min) 127.29 ± 8.26 95.00 ± 14.04 Mean diff = +32.29; t +26.89 to +37.69 <0.001 Time to first rescue analgesia (min) 341.43 ± 30.60 246.29 ± 34.65 Mean diff = +95.14; t +79.83 to +110.45 <0.001 Motor onset to Bromage M3 (min) 4.49 ± 0.45 5.92 ± 0.46 Mean diff = -1.43; t -1.64 to -1.22 <0.001 Duration of motor block (M3→M0; min) 205.14 ± 18.50 124.70 ± 18.60 Mean diff = +80.44; t +71.75 to +89.13 <0.001 Peak sensory level achieved, n (%) T4: 10 (28.6%); T6: 20 (57.1%); T8: 5 (14.3%) T4: 7 (20.0%); T6: 14 (40.0%); T8: 14 (40.0%) χ² (2 df) - 0.054 (NS) Table 2 summarizes the comparative block characteristics between the two study groups. The mean sensory onset time to reach the T10 dermatome was significantly shorter with hyperbaric levobupivacaine (2.87 ± 0.46 min) than with hyperbaric ropivacaine (4.15 ± 0.34 min) (p < 0.001; 95% CI = -1.47 to -1.09). The two-segment regression time, indicating duration of sensory blockade, was significantly prolonged in the HL group (127.29 ± 8.26 min) compared to the HR group (95.00 ± 14.04 min) (p < 0.001). The duration of analgesia was also markedly longer with HL (341.43 ± 30.60 min) than HR (246.29 ± 34.65 min), demonstrating nearly 95 minutes of additional pain relief (p < 0.001). Motor block onset was faster with HL (4.49 ± 0.45 min) compared to HR (5.92 ± 0.46 min) (p < 0.001), while the duration of motor blockade was substantially prolonged with HL (205.14 ± 18.50 min) versus HR (124.70 ± 18.60 min) (p < 0.001). The maximum sensory level achieved was predominantly at T6 in both groups, though a slightly higher proportion of HL patients attained T4 level; this difference was not statistically significant (p = 0.054). Figure 2 Figure 3 Table 3. Intra-operative stability and analgesia (N = 70) Measure Group HL (mean ± SD) Group HR (mean ± SD) Effect & test 95% CI p-value SpO₂ at 5 min (%) 99.06 ± 0.17 98.91 ± 0.28 Mean diff = +0.15; t +0.04 to +0.26 0.009 SpO₂ at 30 min (%) 99.03 ± 0.18 98.88 ± 0.33 Mean diff = +0.15; t +0.03 to +0.27 0.015 SBP/DBP, HR (baseline→120 min) Comparable across all intervals Comparable across all intervals Repeated comparisons - NS Time to first rescue analgesia (min) 341.43 ± 30.60 246.29 ± 34.65 Mean diff = +95.14; t +79.83 to +110.45 <0.001 Table 3 highlights intra-operative hemodynamic stability and analgesic profile in both groups. Oxygen saturation remained consistently high throughout the surgery in both groups, with only marginal differences at 5 minutes (99.06 ± 0.17 % vs 98.91 ± 0.28 %, p = 0.009) and 30 minutes (99.03 ± 0.18 % vs 98.88 ± 0.33 %, p = 0.015), which were statistically significant but clinically insignificant. Systolic and diastolic blood pressures as well as heart rate remained comparable across all intervals up to 120 minutes (p > 0.05). The time to first rescue analgesia, a reflection of postoperative analgesic duration, was significantly longer in the HL group (341.43 ± 30.60 min) compared to the HR group (246.29 ± 34.65 min) (p < 0.001), reinforcing the prolonged analgesic efficacy of levobupivacaine. Figure 4 Figure 5

Baseline comparability (Table 1). Both cohorts were well matched: age, sex distribution, ASA class, height, and weight showed no statistically significant differences (all p>0.05). This baseline balance reduces confounding and supports causal attribution of downstream differences to the intrathecal agent rather than case-mix. Similar baseline matching has been emphasized in prior randomized comparisons of Levobupivacaine and Ropivacaine, where demographic and ASA parity were shown to be prerequisites for interpreting block kinetics and safety profiles reliably Kumar RA et al., (2020)[6] Sensory kinetics and extent (Table 2). Hyperbaric Levobupivacaine (HL) achieved a faster sensory onset to T10 (mean difference -1.28 min; 95% CI -1.47 to -1.09; p<0.001) and a longer two-segment regression time (+32.29 min; 95% CI +26.89 to +37.69; p<0.001) than hyperbaric Ropivacaine (HR). These findings mirror the pattern reported when the same baricity is used for both drugs: hyperbaric Levobupivacaine tends to have a brisker ascent and more durable sensory block compared with hyperbaric Ropivacaine Gawai SK et al., (2025)[7]. Even in isobaric head-to-heads, Levobupivacaine has shown either faster or comparable onset but consistently longer duration than Ropivacaine. The role of baricity in improving predictability and ceiling level is well described; hyperbaric preparations reduce inter-patient variability versus isobaric forms Sharma R et al., (2025)[8]. The peak level distribution favored higher blocks a bit more often with HL (T4 in 28.6% vs 20.0%), although this just missed conventional significance (χ², p=0.054). Clinically, this sits with the notion that hyperbaric Levobupivacaine can climb higher (position-dependent) yet remain hemodynamically steady in healthy adults Shah B et al., (2025)[9]. Motor characteristics (Table 2). HL produced faster motor onset (-1.43 min; 95% CI -1.64 to -1.22; p<0.001) and a markedly longer motor duration (+80.44 min; 95% CI +71.75 to +89.13; p<0.001). This aligns with the pharmacologic profile of Levobupivacaine (higher protein binding, greater potency) translating to deeper and longer motor block than Ropivacaine when doses are selected for surgical anaesthesia. Conversely, when early mobilization is a priority (e.g., ambulatory settings), Ropivacaine’s relatively shorter motor block is often advantageous Gupta R et al., (2024)[10]. In mixed surgical series using hyperbaric agents, Ropivacaine typically trades some block longevity for a smoother, earlier motor recovery, consistent with our observed 80-minute shorter motor duration in HR Hiwarkar AA et al., (2023)[11]. Analgesia horizon (Tables 2 & 3). Time to first rescue analgesia was ~95 minutes longer with HL (mean difference +95.14 min; 95% CI +79.83 to +110.45; p<0.001). This reinforces the practical benefit of Levobupivacaine for postoperative comfort in infra-umbilical procedures, paralleling prolonged analgesia signals seen in obstetric and non-obstetric cohorts Gupta S et al., (2024)[12]. Where adjuvants (e.g., intrathecal fentanyl) are used, relative differences may narrow, but the direction of effect generally persists-Levobupivacaine longer than Ropivacaine Savio AA et al., (2025)[13]. Hemodynamic stability and oxygenation (Table 3). Systolic/diastolic pressures and heart rate remained comparable across time in both groups, with no clinically relevant divergence-an important safety marker. Minor statistical differences in SpO₂ at 5 and 30 minutes (both +0.15% with HL) were clinically trivial and remained within normal ranges. The hemodynamic neutrality observed here matches randomized data in obstetric populations with cardiovascular vulnerability (pre-eclampsia), where hyperbaric Levobupivacaine delivered stable profiles comparable or superior to Ropivacaine while prolonging analgesia Pahade A et al., (2024)[14]. Comparative trials of hyperbaric Ropivacaine against Bupivacaine likewise show good stability but shorter block persistence Hazarika R et al., (2025)[15].

The present study demonstrated that both hyperbaric Levobupivacaine 0.5% and hyperbaric Ropivacaine 0.75% are effective and safe agents for subarachnoid block in infraumbilical surgeries. However, hyperbaric Levobupivacaine produced a significantly faster onset of sensory and motor blockade, higher and more sustained sensory levels, longer duration of anaesthesia, and prolonged postoperative analgesia compared to hyperbaric Ropivacaine, while maintaining hemodynamic stability throughout the intraoperative period. In contrast, Ropivacaine provided adequate surgical anaesthesia with earlier motor recovery, which may be advantageous for day-care procedures. Both agents were well tolerated, with no reported incidence of hypotension, bradycardia, or other major adverse effects. Thus, hyperbaric Levobupivacaine can be considered a more efficacious alternative when prolonged intraoperative anaesthesia and postoperative pain relief are desired, whereas hyperbaric Ropivacaine remains suitable for shorter surgical durations and early ambulation requirements. LIMITATIONS OF THE STUDY 1. The study was conducted with a relatively small sample size (n = 70), which may limit the generalizability of findings to larger or more diverse populations. 2. The study included only ASA I–II patients; results may differ in higher-risk surgical candidates with cardiovascular or systemic comorbidities. 3. Only infraumbilical surgeries were studied, and results cannot be extrapolated to upper abdominal, thoracic, or obstetric procedures. 4. The study did not include objective postoperative pain scores beyond the first rescue analgesia time, limiting evaluation of the long-term analgesic profile. 5. Serum drug concentrations were not measured; hence, the pharmacokinetic correlation between block characteristics and plasma levels could not be assessed. 6. The influence of patient positioning and CSF characteristics on spread and duration of block was not analyzed.

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