Discussion

Compared with ropivacaine, our study demonstrated that isobaric levobupivacaine provided a longer duration of analgesia with a more rapid onset of sensory and motor blockade. The mean onset of sensory block was significantly faster in Group L (5.98 ± 1.39 minutes) than in Group R (8.31 ± 1.01 minutes). The difference between the two groups was highly statistically significant (p < 0.001), indicating earlier establishment of sensory blockade with intrathecal levobupivacaine. Group L also demonstrated a significantly faster onset of motor block (8.68 ± 1.81 minutes) compared with Group R (11.76 ± 1.42 minutes). The difference was highly statistically significant (p < 0.001), suggesting a more rapid onset of motor blockade with levobupivacaine. The mean duration of sensory block was significantly longer in Group L (268.11 ± 42.9 minutes) than in Group R (160.48 ± 51.74 minutes). The difference was highly statistically significant (p < 0.001), demonstrating prolonged sensory anesthesia with levobupivacaine. The mean duration of motor block was significantly longer in Group L (230.89 ± 48.42 minutes) compared with Group R (136.02 ± 41.62 minutes). The difference was highly statistically significant (p < 0.001), indicating prolonged motor blockade with levobupivacaine. The duration of postoperative analgesia was significantly longer in Group L (275.22 ± 39.54 minutes) than in Group R (207.66 ± 39.34 minutes). The difference was highly statistically significant (p < 0.001), reflecting superior and prolonged postoperative analgesia with levobupivacaine.

Baseline hemodynamic parameters and patient characteristics did not differ significantly between the two groups. No significant adverse effects were observed in either group. Levobupivacaine and ropivacaine are two contemporary amide local anesthetics used to reduce the toxicity associated with bupivacaine [10,11]. Several studies by Lee et al., Kannai et al., and Gautier et al. have demonstrated that levobupivacaine has efficacy comparable to that of bupivacaine and ropivacaine while exhibiting an improved safety profile [11-13]. Numerous studies have compared their clinical efficacy, baricity, and potency at varying doses.

Lee et al. conducted a study comparing bupivacaine, levobupivacaine, and ropivacaine and concluded that levobupivacaine and bupivacaine are equipotent, whereas ropivacaine is only two-thirds as potent as the other two drugs [14]. The greater lipid solubility of levobupivacaine may partially account for its higher potency compared with ropivacaine [15]. Several studies have demonstrated that levobupivacaine has approximately 30% greater potency than ropivacaine [16,17]. Consequently, based on previous studies, we selected concentrations of 5 mg/mL for levobupivacaine and 7.5 mg/mL for ropivacaine while maintaining a constant volume.

Samar et al. reported that the onset of sensory blockade in the levobupivacaine group was significantly faster (6.97 ± 1.82 minutes) than in the ropivacaine group (8.47 ± 2.55 minutes) (p < 0.05) [18]. They also observed that the onset of motor block was 10.27 ± 1.92 minutes in the levobupivacaine group compared with 12.93 ± 2.55 minutes in the ropivacaine group (p < 0.05). Similarly, Patel et al. compared levobupivacaine and ropivacaine for spinal anesthesia and found that the mean onset of sensory block was 4.74 ± 0.828 minutes in the levobupivacaine group and 6.47 ± 0.861 minutes in the ropivacaine group (p < 0.001) [19]. These findings are consistent with those of our study. They also reported that the time to achieve Modified Bromage Scale grade 3 was 6.68 ± 1.147 minutes in the levobupivacaine group and 7.97 ± 0.87 minutes in the ropivacaine group (p < 0.001).

Athar et al., in a study comparing equivalent intrathecal doses of levobupivacaine and ropivacaine, found that the onset of sensory blockade was significantly shorter in the ropivacaine group (13.17 ± 3.02 minutes) than in the levobupivacaine group (20.33 ± 5.31 minutes; p < 0.0001), which contradicts our findings [9]. They also reported that the time to achieve Modified Bromage Scale grade 3 was shorter in the ropivacaine group (7.83 ± 2.84 minutes) than in the levobupivacaine group (12.17 ± 4.09 minutes; p < 0.0001), a finding that differed from previous studies. Our results are therefore not consistent with those of Athar et al., as we observed a faster onset of motor blockade in Group L than in Group R. This discrepancy may be attributable to differences in demographic characteristics, baricity, methodology, or drug dosage. However, apart from the faster onset of sensory block, the other outcomes reported by Athar et al., including the duration of sensory blockade and postoperative analgesia, were longer in the levobupivacaine group than in the ropivacaine group [9]. Govindarao et al. also demonstrated that motor block developed significantly more slowly in patients receiving intrathecal ropivacaine (12.63 ± 3.5 minutes) than in those receiving levobupivacaine (9.03 ± 2.67 minutes) (p = 0.000) [20]. Mantouvalou et al. compared plain ropivacaine, bupivacaine, and levobupivacaine for lower abdominal surgery and concluded that the onset of motor block was significantly earlier in patients receiving bupivacaine than in those receiving ropivacaine and was comparable to that in the levobupivacaine group (p < 0.05) [21].

Several studies have attributed the greater potency of levobupivacaine to its higher lipid solubility compared with ropivacaine [17,18,21,22]. The greater lipid solubility and protein binding reported in previous studies may explain the longer duration of sensory and motor blockade observed in the levobupivacaine group in our study. This suggests that patients in Group L experienced a longer duration of analgesia than those in Group R. The longer duration of sensory blockade is clinically important because it may reduce the need for rescue analgesics and potentially decrease postoperative opioid consumption.

A longer duration of postoperative analgesia is desirable because it may reduce postoperative pain-related stress and improve patient satisfaction. However, prolonged motor blockade is less desirable because it may delay mobilization in ambulatory surgery. Therefore, levobupivacaine may be better suited for procedures of longer expected duration. We did not measure the time to ambulation or the quality of recovery.

Limitations

This was a single-center study, and the study population was limited to ASA physical status I and II patients undergoing elective infraumbilical procedures. This limits the generalizability of the findings to higher-risk populations, emergency surgeries, obstetric cases, or patients with significant cardiovascular instability, in whom hemodynamic responses may differ considerably. Maintenance of drug temperature could be a challenge in tropical countries and may have influenced the study results. Postoperative follow-up was limited to 24 hours. Therefore, late complications, prolonged neurological outcomes, and patient-centered recovery parameters, such as time to ambulation, discharge readiness, and long-term analgesic quality, were not evaluated. Institutional practices, anesthetic technique variations, and perioperative care protocols may also limit the generalizability of the findings. Future studies with larger, multicenter designs, inclusion of high-risk populations, and incorporation of objective monitoring modalities are warranted to validate and extend these findings.