Investigation of the effect of preoperative fasting duration on postoperative shivering and delirium in patients undergoing abdominal surgery in lithotomy position

Objective: To evaluate the effect of different pre-operative fasting durations (8–9 h, 9–10 h, ≥10 h) on postoperative shivering and early delirium in adult patients undergoing abdominal surgery in the lithotomy position. Methods: After institutional ethics approval (TÜTF- GOBAEK 2023/90) , 159 patients were prospectively enrolled (83 % female; mean age 51.4 ± 14.3 years; BMI 25.8 ± 3.9 kg m⁻²). Patients were grouped by fasting duration. Shivering was recorded with the Crossley–Mahajan Scale at 0, 15 and 30 minutes post-operatively, and early delirium was assessed using both the bCAM and Delirium Assessment Scale. Secondary endpoints included intra-operative hypothermia (< 36 °C), blood transfusion, vaso-pressor/inotrope use and anaesthetic technique. Results: Most patients were ASA II (67.9 %). Intra-operative hypothermia occurred in 17 %, blood transfusion in 27.7 %, vaso-pressor/inotrope use in 10.1 %, and combined general + epidural anaesthesia in 13.2 %. Mean shivering score fell from 1.57 ± 0.80 at time zero to 0.35 ± 0.52 at 30 minutes, with no significant difference between fasting groups (p > 0.05). Overall delirium incidence remained low (bCAM 5.7 %, Delirium Assessment Scale 4.4 %) and did not vary with fasting duration (p > 0.05). In contrast, hypothermic patients showed significantly higher shivering scores at all time points (p < 0.001). Delirium rose to 14.3 % with transfusion and 43.8 % with vaso-pressor/inotrope support (both p < 0.01). Combined general + epidural anaesthesia increased bCAM-defined delirium to 19.0 % versus 3.6 % under general anaesthesia alone (p = 0.004). Conclusion: When active warming, fluid optimisation and haemodynamic control are applied, pre-operative fasting length is not an independent predictor of postoperative shivering or early delirium. Conversely, intra-operative hypothermia, transfusion, vaso-pressor/inotrope therapy and combined anaesthesia markedly heighten these risks. Larger multicentre trials are warranted to refine peri-operative safety protocols and fasting guidelines. Keywords: Delirium, Fasting duration, Lithotomy position, Shivering