Comparison of Prophylactic Use of Dexmedetomidine and Ketamine for Prevention of Shivering After Spinal Anesthesia

Spinal anaesthesia is a safe and popular anaesthetic technique for various surgeries. Around 40-60% of the patients under spinal anaesthesia develop shivering.The main causes of shivering intra and postoperatively are temperature loss, decreased sympathetic tone and systemic release of pyrogens. Hypothermia during neuraxial anesthesia develops initially from core to peripheral redistribution of body heat. Redistribution of body heat during spinal or epidural anesthesia typically decreases core body temperature 0.5-1.0 degree Celsius.

Shivering is characterised by involuntary oscillatory contractions of skeletal muscles. Once the body is exposed to cold, it is a physiological response for heat preservation after peripheral vasoconstriction. Postoperative shivering is defined as the fasciculation of the face, jaw or head or muscle hyperactivity, lasting longer than 15 seconds. It is a common and challenging aspect of anaesthesia and targeted temperature modulation because it leads to increase oxygen consumption and increases the risk of hypoxia.

The most frequent complication in postoperative period is shivering which is reported to be between 20-70% after general anaesthesia. The incidence reported in previous studies are 5-65% after general anaesthesia and 30-33% after epidural procedures. The overall shivering incidence in a recent meta-analysis was 34%.

The underlying pathology of shivering is not fully understood yet, therefore the definitive treatment and prevention has not been established till date. Due to its importance as postoperative complication and the lack of available data about aetiology and treatment, this narrative review of the published literature on this topic is essential.

Various pharmacological agents being used for prophylaxis and treatment of post spinal shivering are Opioids like fentanyl, tramadol, pethidine, Anticholinergics like physostigmine, NMDA receptor antagonist like ketamine and the latest being alpha-2 antagonists like clonidine, dexmedetomidine.