This study aims to investigate the efficacy of oral ondansetron film strips on the incidence of post-spinal shivering in patients undergoing surgeries using spinal anesthesia at Kasr Alainy hospitals, Cairo University.

This prospective, double-blinded, randomized controlled study will be conducted on 50 patients aged from 18 to 65 years of both sexes with ASA I, II who are scheduled for elective surgical procedures under spinal anesthesia in the lower half of the body such as orthopedic, urological, or general surgeries. Patients will be divided into two equal groups: Group (O) will receive oral ondansetron in the form of an oral soluble film 4 mg strip immediately before insertion of IV cannula and group (C) will receive a placebo in the form of an oral peppermint strip immediately before insertion of the IV cannula.

In the anesthesia preparation room and before the insertion of the peripheral IV cannula, patients in group O will receive oral ondansetron in the form of an oral soluble film 4 mg strip (Ondalenz, 4 mg orodispersible films of Nerhadou International Co.) and patients in group C will receive a placebo in the form of an oral peppermint strip (Listerine Cool Mint Pocketpakas).

Following the insertion of a cannula; IV midazolam at a dose of 0.05 mg/kg will be administered intravenously. Then the patient will be transferred immediately to the operating theatre.

On entering the operating room; all patients will be connected to standard ASA monitoring which included electrocardiography (ECG), non-invasive arterial blood pressure (NIBP) including systolic, diastolic, mean arterial blood pressure (MAP) and Oxygen saturation using pulse oximetry.

With the patient sitting on the operating table, the L3-L4 interspace will be identified by identification of Tuffier's line. Under complete aseptic conditions, a dural puncture will be achieved by a 22G pencil-point spinal needle that will be introduced in a paramedian (lateral) approach through the L3-4 intervertebral space. After CSF aspiration and confirmation of correct intrathecal space, 3.5 mL of Sunny Pivacaine 0.5% (hyperbaric bupivacaine 20mg/4mL amp of Sunny pharmaceutical group) plus 25 μg of fentanyl-Hameln (of Sunny pharmaceutical group) will be injected over one minute.

The sensory block will be assessed by a pinprick test and the motor block will be assessed using a modified Bromage scale (0 = no motor block; 1= hip is blocked; 2= hip and knee are blocked; 3= hip, knee, and ankle are blocked). Peak sensory level will be confirmed and if a sensory level < T8 the patient will be excluded. If general anesthesia is needed for any reason, the patient will also be excluded from the study.

The ambient room temperature will be maintained at 24°C. IV fluids will be administered according to the conventional way as follows, hourly maintenance was the sum of A (4x first 10 Kg body weight), B (2x next 10 Kg body weight) and C (1x remaining Kg bodyweight) in addition to deficit (or fasting requirements), that will be hourly maintenance multiplied by the numbers of hours of fasting, half of it will be administered in the first hour and the second half will bne administered during second and third hours of surgery. Balanced crystalloids such as Ringer's lactate or acetate will be preferred over normal saline. Blood loss will be estimated through the surgical field, towels, gauzes and suction jar & will be replaced by crystalloids 1:3 or colloid/blood and blood products 1:1 ratio. All IV fluids will be administered at room temperature. All patients will be covered with surgical drapes from the lower extremities up to the lower chest during the operation. No warming devices will be used. Supplementary oxygen by a face mask will be given to all patients at a rate of 6 L/min.

The tympanic temperature will be monitored and measured by using the Braun ThermoScan 5 Ear Thermometer model IRT 6500. Hypothermia will be defined as a tympanic membrane temperature < 36.5◦ C.

Shivering score will then be assessed according to the Bedside shivering assessment score (BSAS) . If shivering scores ≥ 3, 30 mg of IV pethidine were administered as a rescue dose.

Postoperative:

Patients will be discharged to post anesthesia care unit (PACU). All patients will be monitored in the post-anesthesia care unit (PACU), covered by one cotton blanket over their entire body. The PACU temperature will be maintained at 24ºC.

The adverse effects will be assessed: allergic reaction from the used drugs, complications from the surgery done as:

Hypotension (MAP < 20% of baseline). In case of hypotension, the patients will be managed with intravenous loading with Ringer's lactate and boluses of 10 mg ephedrine IV.

Bradycardia (HR< 60 beats/min). In the case of bradycardia, the patients will be managed with 0.02 mg/kg atropine IV.

Respiratory depression will be considered if the respiratory rate is less than 10 breaths per minute and oxygen saturation (SpO2) was < 92% for 30 or more seconds.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status I, II.
• Patients underwent elective surgical procedures under spinal anesthesia in the lower half of the body such as orthopedic, urological, or general surgeries.

Exclusion Criteria:

• Patient refusal.
• Morbid obese patients or those who were not candidates for spinal anesthesia.
• Pregnant females.
• Patients with comorbidities such as severe cardiopulmonary, severe hepatic or renal diseases, thyroid disorders, and convulsions.
• Uncooperative patients and patients with psychological disorders.
• Patients on regular ondansetron or other antiemetics.
• Patients taking selective serotonin reuptake inhibitors.
• Patients with allergy to 5-HT3 receptor antagonist drugs.
• Patients receiving saddle spinal block.
• In surgeries less than 1 h or longer than 3 hours duration.