Shivering is one of the most frequent complications occurring during or after spinal anesthesia with many side effects. The aim of the present study was to compare between two different doses of ondansetron for anti-shivering effect

Shivering is one of the most frequent complications occurring during or after spinal anesthesia, it affects about 40%-60 % of patients under spinal anesthesia. Intra and Post spinal shivering is distressing for the patients and anesthetist. Shivering may aggravate medical conditions in patients with limited cardiac or respiratory functions. It increases tissue oxygen demand many folds which in turn leads to increase the load on respiratory and cardiac systems to cope with increased aerobic metabolism. Shivering interferes with good patient monitoring by causing artifacts of electrocardiography, invasive and non-invasive blood pressure, pulse oximetry, etc... . Postoperatively shivering may cause discomfort to the patient, increases wound pain by stretching incision, increase the incidence of bleeding and infection.

We aim to compare the prophylactic use of two different doses of ondansetron on the incidence of shivering after spinal anesthesia in patients scheduled for lower limb surgery.

The primary outcome was percentage of patients suffering from shivering after spinal anesthesia, secondary outcomes include any side effects related to both doses.

Inclusion Criteria:

• Age between 18-65 years
• Both sexes
• American Society of Anesthesiologists
• physical status I and II
• scheduled for lower limb surgery under spinal anesthesia

Exclusion Criteria:

• Uncooperative patients
• psychologically unstable patients
• obese patients with BMI >30 preoperative use of ondansetron, or opioids Fever Patients with some clinical conditions like hypo- or hyperthyroidism, Parkinson's disease.