Abstract
Purpose
This study aimed to investigate whether the clinical efficacy and time to first analgesic request following an ultrasound-guided oblique subcostal transversus abdominis plane (USG-guided OSTAP) block vary across different phases of the menstrual cycle in female patients undergoing laparoscopic cholecystectomy.Design
A prospective, randomized, controlled clinical trial.Methods
Eighty adult female participants with regular menstrual cycles (21-35 days) who were not using any hormonal contraceptives were enrolled. Patients on days 8 to 12 after the onset of their last menstruation were assigned to the follicular phase, and those on days 20 to 24 were assigned to the luteal phase. Within each phase, participants were randomly allocated to a block or a control group, yielding four subgroups (n = 20 each): Group F + B (Follicular+Block), Group L + B (Luteal+Block), Group F + C (Follicular+Control), and Group L + C (Luteal+Control). The block groups received 40 mL of 0.25% bupivacaine. Postoperative pain intensity was evaluated using the visual analog scale (VAS) up to 24 hours postoperatively, and time to first analgesic request was recorded.Findings
Pain scores significantly declined in the block intervention subgroups compared to controls. Subgroup analysis revealed that time to first analgesic request was significantly longer, and early postoperative VAS scores were lower in Group F + B compared to Group L + B, suggesting a phase-dependent variation in block efficacy.Conclusions
The ultrasound-guided OSTAP block provides effective postoperative analgesia following laparoscopic cholecystectomy. However, menstrual cycle phase may influence the degree and duration of its analgesic efficacy, as reflected by postoperative pain scores and time to first analgesic request, and should be considered when perioperative pain management strategies are evaluated.