Palonosetron vs Ondansetron In PONV Prophylaxis Among Idiopathic Scoliosis Patients

The goal of this clinical trial is to compare the effectiveness of two antiemetic drugs, palonosetron and ondansetron, when given alongside dexamethasone as a preventive measure against early and delayed postoperative nausea and vomiting (PONV) in adult and adolescent patients with idiopathic scoliosis undergoing posterior spinal fusion surgery under total intravenous anesthesia (TIVA).

The main questions the study aims to answer are:

* How effective is palonosetron compared to ondansetron, both combined with dexamethasone, in preventing PONV after scoliosis surgery?
* Are there any differences in the need for rescue antiemetics, occurrence of adverse effects related to the study drugs, and patient satisfaction between the two treatment groups?

Participants in the study will be randomly assigned to receive either palonosetron or ondansetron in addition to dexamethasone as part of their anesthesia and antiemetic regimen. The incidence and/ or severity of nausea, vomiting and retching will be assessed at 1 hour, 4 hours, 12 hours, 24 hours and 48 hours after surgery.

BACKGROUND/ JUSTIFICATION Postoperative nausea and vomiting (PONV) is a common complication following surgery and can cause significant morbidity. It occurs in 20-30% of the general population and up to 75-80% in high-risk groups. Children have a higher incidence of PONV compared to adults. PONV can occur at various timeframes after surgery and has clinical and financial consequences, including wound complications, dehydration, and prolonged hospitalization. Prevention and treatment of PONV are crucial for comprehensive perioperative care.

Posterior spinal fusion surgery for idiopathic scoliosis is a complex and painful procedure, increasing the risk of PONV. Various strategies can be employed to mitigate these risks, such as adequate hydration, the use of intravenous antiemetics, avoiding volatile anesthetics, and adopting a multimodal analgesic approach. Dexamethasone and anti-serotonergic drugs like ondansetron are commonly used antiemetics due to their efficacy and safety profiles. Dexamethasone is particularly favored for its long duration of action and pain-reducing effects.

Palonosetron, a second-generation anti-serotonergic drug, has a unique pharmacokinetic profile with a prolonged duration of action. It may be more beneficial for patients on prolonged opioid-based analgesic regimens. However, its higher cost and inconsistent study findings limit its widespread use, especially in scoliosis patients undergoing spinal fusion surgery.

Total intravenous anesthesia (TIVA) is recommended for high-risk PONV patients, as it reduces the emetogenic effect of volatile anesthetics. Propofol, used in TIVA, is itself an effective antiemetic. TIVA with propofol has been shown to be as effective as giving a single antiemetic and can further reduce the risk of PONV when combined with other prophylactic antiemetics.

The standard practice for managing PONV involves the administration of two antiemetics and considering TIVA for high-risk patients. This study aims to compare the effectiveness of palonosetron and ondansetron when administered alongside dexamethasone in scoliosis patients undergoing spinal fusion under TIVA. The study will also evaluate the number of rescue antiemetics needed, assess adverse effects, and measure patient satisfaction.

The study will be randomized and double-blinded, to be conducted in Universiti Malaya Medical Centre (UMMC). The sample size is calculated to be 92 participants, after taking into account a 20% dropout rate. Adult and adolescent idiopathic scoliosis patients undergoing posterior spinal fusion surgery will be eligible for the study. Written informed consent will be obtained from participants or their guardians, and assent will be obtained from adolescent participants. Patients will be randomized to receive either palonosetron or ondansetron along with dexamethasone.

The study will follow standard anesthetic techniques, including TIVA with remifentanil and propofol. Intravenous injections of the study drugs or placebo will be given during surgery, and dexamethasone will be administered as a baseline antiemetic. Morphine will be administered before the end of surgery for pain management.

Eligibility Criteria:
Inclusion Criteria:

* Age of 10 years and above
* American Society of Anaesthesiologists (ASA) I-II Physical Status

Exclusion Criteria:

* History of allergy to serotonin receptor antagonists or dexamethasone
* Obesity with a body mass index (BMI) of 34 and above
* Body weight of less than 30kg
* Active smoker
* History of gastroesophageal reflux disease/ other gastrointestinal diseases associated with vomiting
* History of motion sickness
* History of nausea or vomiting within 24 hours before the surgery
* Administration of antiemetics/ steroids/ psychoactive medications within 24 hours before the surgery
* Require mechanical ventilation postoperatively
* History of cardiac arrhythmias
* Prolonged QT (QTc is prolonged if \> 440ms in men or \> 460ms in women