The aim of the study is to compare antiemetic effects between dexmedetomidine and ondansteron in the first group versus dexamethasone and ondansteron in the second group.

The primary outcome in this study is incidence of postoperative nausea and vomiting after laparoscopic cholecystectomy.

The secondary outcomes are:

• The severity of post operative nausea and vomiting.
• Use of rescue antiemetic drugs.
• Postoperative pain and sedation.

General anesthesia is widely used in several surgeries. It can cause some complications such as postoperative nausea and vomiting (PONV). PONV is more common in general anesthesia than spinal anesthesia. PONV remains an extremely significant challenge due to its complex mechanism, resulting in serious consequences. Therefore an effective way to prevent or arrest PONV is urgently needed as Also, it can cause electrolyte imbalance and aggravate bleeding that delay hospital discharge.

The causes of PONV are multifactorial and can largely be categorized as patient risk factors, anaesthetic technique, and surgical procedure. Antiemetics work on several different receptor sites to prevent or treat PONV.

No single antiemetic pharmaceutical has been provided to be a universal solution to PONV. In general, multimodal combination treatment has superior viability for PONV prophylaxis compared with monotherapy .

Because nausea and vomiting were defined as two separate phe-nomena, studies should report and evaluate the variables distinctly . While since few patients experience vomiting without nausea, the incidence of PONV and postoperative nau¬sea (PON) is fairly similar, thus original papers often do not try to distinguish these variables . So, if PONV but not PON was reported in trails, we considered the PONV variables as a very close substitute for PON; when both PONV and PON were reported simultaneously, we assessed the nausea values. The most com¬monly used time interval to measure the role of antiemetic is 24 hours 6.

Ondansetron is a serotonin receptor antagonist, which is very important in preventing nausea and vomiting due to surgery and chemotherapy; it exhibited an anti-vomiting effect by inhibiting 5-Hydroxytryptamine type 3 (5-HT3) receptors in the vomiting centre .

Dexmedetomidine is a potent and highly selective a2-adrenoceptor agonist, which binds to transmembrane G protein-binding receptor located in the brain and spinal cord. Since nausea and vomit¬ing may be induced by high catecholamine con¬centrations, a decrease of sympathetic tone could explain the antiemetic effect of dexme¬detomidine. Finally, consumption of intraopera¬tive opioids, which increases the risk of PONV , may be reduced through the use of dexmedetomidine It affects the functions of central nervous, circulatory systems and exhibits sedative, analgesic, sympatholytic properties. Recently, the effect of dexmedetomidine on PONV has been the focus of clinical researchers. Nevertheless, controversy about the effectiveness of dexmedetomidine for PONV is still ongoing, for different results reported in associated literature.

Glucocorticoids may exert an antiemetic effect by inhibiting inflammatory mediators and by interacting with serotonin, neurokinin, a-adrenergic receptors, and other receptors. Furthermore, several studies have shown that dexamethasone enhances the antiemetic efficacies of 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists.

Inclusion Criteria:

• 70 Female patients aged between 18 and 65 years
• ASA I or II
• patients scheduled for elective laparoscopic cholecystectomy surgery will be included in this study.

Exclusion Criteria:

• Females above 65 years old.
• patients under 18 years old.
• ASA > II.
• Obesity (BMI>40 kgm2).
• Known hypersensitivity to drugs used in the study protocol.
• Comorbidities that were known to increase the risk of PONV (e.g. vestibular disease).
• Liver or renal dysfunction (liver enzyme or creatinine 1.5 times higher than normal).
• Alcoholism or drug abuse.
• Use of antiemetics and psychotropic drugs or glucocorticoids within 24 h before surgery.

According to APFEL score female is a risk factor for PONV.

The IPD will be available with the principle investigator within 6 months after publishing the study

within 6 months after publishing the study

yasmine162078_pg@med.tanta.edu.eg

Double (Participant, Outcomes Assessor)

• The participants will be kept blind in both groups.
• Outcome assessors will be blinded as they will be anesthesia resident and nurse not participating in the study.