Effect of Ondansetron on Spinal-induced Hypotension for Percutaneous Nephrolithotomy

This study aims to assess the effect of Ondansetron on spinal induced hypotension when bupivacaine and dexmedetomidine are used intrathecally during spinal anesthesia for percutaneous nephrolithotomy.This prospective randomized double-blinded study will be carried out at Urology and Nephrology center, Mansoura University after approval of Institutional Research Board, Faculty of Medicine, Mansoura University. Written informed consents will be obtained from participants after explanation of the used drug and its possible consequences.

Basal readings for blood pressure, heart rate, and ECG analysis and oxygen saturation will be recorded before the start of spinal anesthesia.

Upon arrival to OR, wide bore intravenous access (20 gauge cannula) will be secured for preoperative fluid preloading (10 ml/kg ringer solution intravenously).All patients will be monitored for non-invasive blood pressure (BP), Heart rate (HR) , ECG and pulse oximetry , measurements will be recorded every 5 min for first 30 minutes then every 15 min till the end of surgery .Patients will be randomly divided into two groups, using a computer generated random table;

• Group S:patients will be injected with 10 ml normal saline intravenous 5 min before spinal anesthesia
• Group O:patients will be injected with 4mg Ondansetron diluted with normal saline IV 5 minutes before spinal anesthesia Spinal anesthesia will be delivered in the sitting position under complete aseptic condition using 25-gauge spinal needle (quinckle type), the needle will be advanced at level L 4-5 or L 3 - 4. After a clear flow of CSF, 3ml 0.5 % hyperbaric bupivacaine (15mg)will be injected followed by 5 Mcg dexmedetomidine in insulin syringe diluted to 1ml .After anesthesia, patients will be positioned supine immediately, sensory level will be assessed each 2 minutes by pinprick test, a sensory block at T4-6 will be considered sufficient to start surgery.o BP, HR and oxygen saturation will be recorded every 5 minutes for first 30 minutes then every 15 minutes till the end of surgery. Hypotension will be defined as a decrease blood pressure more than 20% of basal BP or decrease systolic than 90 mmHg and will be treated with IV ephedrine (5mg bolus). Bradycardia will be defined as heart rate less than 50 beat / min and will be treated with IV atropine (0.5mg).The maximum level of sensory block will be assessed every 2 minutes till reaching maximum level of sensory block by pin prick test or cold sensation using alcohol swab.The incidence of ECG changes(dysrhythmia, ST changes).The incidence of pruritus.The incidence of nausea and /or vomiting.Postoperative data( HR, BP, SPo2) will be measured every 15 minutes for 2 hours.

Inclusion criteria

• Patients scheduled for PCNL surgery.
• ASA classification I or II

Exclusion criteria

• Patient refusal
• Contraindication to spinal anesthesia.
• Known allergy to Ondansetron.
• Uncontrolled hypertensive patient.
• Ischemic heart diseases.
• Moderate to severe stenotic valve lesion.
• Atrial fibrillation.