Timing Matters: An Observational Study on Circadian Effects of Spinal Anesthesia in Cesarean Delivery

<b>Background:</b> The timing of anesthesia administration may affect drug efficacy and recovery outcomes. Understanding these variations is important for optimizing anesthetic care. <b>Aim:</b> To assess how spinal anesthesia timing affects block duration, postoperative pain, and CRP and cortisol levels in cesarean deliveries. <b>Methods:</b> Ninety women were divided into three groups based on spinal anesthesia timing: Group A (08:00-16:00), Group B (16:00-00:00), and Group C (00:00-08:00). Standardized spinal anesthesia was administered. Sensory/motor blockade and pain (NRS) were assessed every 10 min. Blood samples for CRP and cortisol were collected preoperatively and at 2, 4, 24, and 48 h post operation. <b>Results:</b> Group C showed shorter sensory and motor blockade than Groups A and B (<i>p</i> < 0.05). The time to first analgesic request was longest in Group A, while Group C reported the highest pain scores (<i>p</i> < 0.05). CRP levels were significantly higher in Group B vs. Group A at 24 and 48 h, and vs. Group C at 48 h (<i>p</i> < 0.05). Group B demonstrated the steepest CRP velocity, indicating a more rapid physiological stress response. BMI differences may have influenced biomarker dynamics. <b>Conclusions:</b> Spinal anesthesia timing significantly impacts block duration, pain experience, and the rate of the physiological stress response. CRP velocity may offer additional insights into perioperative inflammation. Circadian considerations should be integrated into anesthetic planning for cesarean deliveries.