This study will look at the incidence of post-spinal shivering (PSS) among the obstetrics population and will investigate whether higher operation theater (OT) temperature range or/and IV Ondansetron are able to reduce the incidence of PSS. This is a double-blind, randomized, factorial study, patients will be grouped into 4 groups - LP, HP, LO, HO (L= low-temperature range, H= high-temperature range, P= placebo, O=Ondansetron). All patients undergoing cesarean section under spinal anesthesia will be recruited, and it will be conducted in obstetrics OT.

Many studies have been conducted to look at methods to prevent and treat postspinal shivering. However, there is still no clear protocol or gold standard for post-spinal shivering management. This is due to the fact that post-spinal shivering mechanisms are complex and are broadly grouped into thermoregulatory and non-thermoregulatory. Preventive measures that have been studied are broadly classified into pharmacological methods and non-pharmacological methods. For Non-pharmacological method, active warming of the patient by various methods have been found to be effective in preventing PSS. However, there is no study that looks at ways to reduce heat loss hence maintaining normothermia and preventing PSS in patients. Therefore in this study, we will be investigating if higher OT temperature will reduce the incidence of PSS. As for pharmacological methods, many drugs have been studied for examples analgesics (tramadol), opioid receptor agonists (pethidine, fentanyl), cholinesterase inhibitors (physostigmine), N-methyl-D-aspartate receptor antagonists (ketamine, magnesium sulphate), α2-central agonists (clonidine, dexmedetomidine), antiserotonergic (ondansetron) and anti-inflammatory drugs (dexamethasone). Ondansetron is usually used to prevent chemotherapy or radiotherapy-induced nausea vomiting and Post-operative nausea and vomiting. Due to the fact that it is generally a safe drug and has added benefit as an anti-emetics especially for obstetrics population, this drug is chosen to be studied. We will also look at the efficacy of the combined effect of increased OT temperature and prophylaxis ondansetron on preventing PSS.

Inclusion Criteria:

• All elective and emergency obstetric patients who are going for lower segment caesarean section (LSCS) under spinal anaesthesia in UMMC.
• Patient who are given combined spinal epidural anaesthesia (CSE) without epidural local anaesthetic top-up will be included.

Exclusion Criteria:

1. Patients who refused to provide study consent
2. Caesarean section planned under general or epidural anaesthesia or potential conversion to general anaesthesia intraoperatively
3. Royal College of Obstetrics and Gynaecology (RCOG) classification of urgency caesarean section Grade I - Immediate threat to life of woman and child. (29)
4. Patients with psychiatric disorders who are taking selective serotonin reuptake inhibitor (SSRI) and serotonin-noradrenaline reuptake inhibitor (SNRI)
5. Patients who has problems with any types of tremor or involuntary movements and neuromuscular disorders such as Parkinson Disease and muscular dystrophy will be excluded from the study as this will interfere with the clinical interpretation of shivering
6. Patients with history of allergic / hypersensitive reactions towards ondansetron.
7. Patients who received ondansetron intraoperatively as anti-emetics.
8. Recruited patients will be excluded if OT temperature on the day of recruitment does not fulfil the OT temperature range fixed for the study

Parturients going for lower segment cesarean section

All volunteers identity will be kept anonymous. However demographic data, body biometrics, underlying co-morbidities, indications for cesarean section, and study outcomes will be analysed and tabulated for publication purposes.