Evaluation of Anti-Shivering Mechanisms of Ketamine and Tramadol in Patients Undergoing Spinal Anesthesia

Abstract

Background: Perioperative shivering is a common complication during spinal anesthesia, affecting patient comfort and increasing metabolic and cardiovascular stress. Effective prophylactic interventions are necessary to reduce shivering and improve perioperative outcomes. Ketamine and tramadol are pharmacologic agents known to prevent shivering through distinct central mechanisms. Objective: To evaluate and compare the anti-shivering mechanisms of ketamine and tramadol in patients undergoing spinal anesthesia, focusing on incidence, severity, onset, duration of effect, and safety profiles. Methodology:

A prospective, randomized study was conducted at Lady Reading Hospital, Peshawar from January to June 2025. A total of 204 patients aged 18–60 years, ASA I–II, undergoing elective surgery under spinal anesthesia, were enrolled using non-probability convenient sampling. Patients were randomly assigned to receive either low-dose ketamine (Group K, n=102) or tramadol (Group T, n=102) intravenously immediately after spinal anesthesia. Perioperative shivering was graded using a four-point scale (0–3), and hemodynamic parameters and adverse effects were recorded. Data were analyzed using SPSS Version 25.0, with Chi-square and t-tests applied; p ≤0.05 was considered significant.

Results

The mean age of participants was 38.5 ± 12.3 years, with 59.8% males and 40.2% females. In Group K, 76.5% of patients did not experience shivering, compared to 70.6% in Group T. Severe shivering was rare in both groups (2% vs 3.9%). Ketamine had a faster onset (3.8 ± 1.2 min) and longer duration (68.4 ± 12.3 min) of anti-shivering effect than tramadol (onset 6.2 ± 1.5 min, duration 60.5 ± 10.7 min). Minor adverse effects were observed, with ketamine causing mild sedation and occasional hallucinations, and tramadol associated with nausea and vomiting. No serious complications occurred in either group.

Conclusion Both ketamine and tramadol are effective and safe for preventing perioperative shivering in patients undergoing spinal anesthesia. Ketamine demonstrates a slight advantage in terms of faster onset and longer duration, making it a preferred choice when rapid and sustained anti-shivering action is required. Both agents improve patient comfort and perioperative outcomes, supporting their use as prophylactic interventions against shivering.