Circadian Timing of Spinal Anaesthesia Affects Analgesia and Inflammatory Response in Cesarean Delivery

Background: The timing of anaesthesia administration may influence both drug efficacy and postoperative recovery, and understanding these temporal variations is essential for optimising anaesthetic management and patient outcomes. In particular, circadian physiology modulates cardiovascular stress responses, immune function, hormonal secretion, and the pharmacokinetics and pharmacodynamics of anaesthetic agents, as well as pain perception, making time of day a potentially important determinant of perioperative outcomes. However, evidence on circadian effects in neuraxial anaesthesia for cesarean delivery remains limited, particularly regarding inflammatory and stress markers, highlighting the need to determine whether anaesthesia administration time affects block characteristics, postoperative pain, and biomarkers such as CRP and cortisol. Aim: To assess how spinal anaesthesia timing affects block duration, postoperative pain, and CRP and cortisol levels in cesarean deliveries.Methods: Ninety women were divided into three groups based on spinal anaesthesia timing: Group A (08:00–16:00), Group B (16:00–00:00), and Group C (00:00–08:00). Standardised spinal anaesthesia was administered. Sensory/motor blockade and pain (NRS) were assessed every 10 minutes. Blood samples for CRP and cortisol were collected preoperatively and at 2, 4, 24, and 48 hours postoperatively. Results: Group C showed shorter sensory and motor blockade than Groups A and B (p