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Comparison of Prophylactic Continuous Infusion of Norepinephrine, Ephedrine, and Their Combination for Prevention of Hypotension During Spinal Anaesthesia for Caesarean Delivery

Sponsor: Alexandria University

Summary

Background Spinal anaesthesia is the preferred anaesthetic technique for most elective Caesarean deliveries; however, maternal hypotension following spinal anaesthesia remains very common and may be associated with maternal nausea and vomiting, reduced uteroplacental perfusion, and adverse fetal acid-base changes. Several vasopressors have been used for the prevention and treatment of spinal anaesthesia-induced hypotension. Ephedrine has traditionally been used because of its combined α- and β-adrenergic effects. However, its indirect sympathomimetic action and placental transfer have raised concerns regarding maternal tachycardia and fetal metabolic effects. Norepinephrine is a potent α-adrenergic agonist with modest β-adrenergic activity. It has increasingly been investigated as an alternative vasopressor for Caesarean delivery because it can effectively maintain maternal arterial pressure with less maternal tachycardia than ephedrine. Randomized studies comparing norepinephrine and ephedrine have demonstrated effective prevention of spinal hypotension with norepinephrine and, in some studies, more favourable neonatal acid-base variables. Phenylephrine is widely used internationally for this indication; however, because of its limited availability in the Egyptian market, norepinephrine represents a potentially practical alternative in the local setting. The present study is designed to compare prophylactic continuous infusions of norepinephrine, ephedrine, and a combination of norepinephrine and ephedrine for prevention of spinal anaesthesia-induced hypotension during elective Caesarean delivery. Maternal haemodynamic effects and neonatal outcomes, including umbilical cord blood gas analysis, will be assessed. Aim of the study To compare the efficacy and safety of prophylactic continuous infusion of norepinephrine, ephedrine, and their combination in preventing spinal anaesthesia-induced hypotension during elective Caesarean delivery. Primary outcome The incidence of maternal hypotension from initiation of spinal anaesthesia until delivery, defined as:Systolic blood pressure (SBP) \<90 mmHg. Secondary outcomes Maternal outcomes 1. Number of hypotensive episodes. 2. Duration of hypotension. 3. Number of rescue vasopressor boluses required. 4. Total dose of study vasopressor administered. 5. Incidence of hypertension, defined as SBP \>140 mmHg. 6. Incidence of maternal bradycardia, defined as HR \<50 beats/min. 7. Incidence of nausea and vomiting. 8. Incidence of shivering. Neonatal outcomes Apgar score at 1 and 5 minutes. Umbilical arterial pH. Umbilical arterial PaCO₂. Umbilical arterial bicarbonate. Patients The study will include healthy pregnant women, American Society of Anesthesiologists (ASA) physical status I, with an uncomplicated singleton pregnancy at ≥36 weeks of gestation, scheduled for elective Caesarean delivery under spinal anaesthesia. After approval by the institutional Ethics Committee and obtaining written informed consent, eligible patients will be randomly allocated in a 1:1:1 ratio to one of three groups using computer-generated randomization and sequentially numbered, opaque, sealed envelopes. Group N - Norepinephrine Norepinephrine concentration: 4 µg/mL Group NE - Combination Norepinephrine concentration: 2 µg/mL plus Ephedrine concentration: 2 mg/mL Group E - Ephedrine Ephedrine concentration: 4 mg/mL Anaesthetic technique All patients will have an 18-G peripheral intravenous cannula inserted before transfer to the operating theatre. On arrival in theatre, standard monitoring will be established, including ECG, non-invasive blood pressure, heart rate and pulse oximetry. Baseline haemodynamic measurements After allowing the patient to rest in the operating theatre, three consecutive measurements of SBP and HR will be obtained before spinal anaesthesia at 1-minute intervals. The mean of the final two measurements will be considered the patient's baseline SBP and HR. This standardized pre-spinal baseline will be used for assessment of haemodynamic changes during the study. Spinal anaesthesia will be performed with the patient in the sitting position at the L3-L4 or L4-L5 interspace using a 27-G Whitacre needle. After free flow of cerebrospinal fluid has been established, 12.5 mg hyperbaric bupivacaine 0.5% with fentanyl 25 µg will be injected over approximately 10-15 seconds. Immediately following the spinal injection, the patient will be positioned supine with approximately 15° left uterine displacement. No routine fluid preload will be administered. Ringer's acetate solution will be administered at a minimal rate required to maintain intravenous access, with a maximum volume of 500 mL . Haemodynamic measurements SBP and HR will be recorded at 1-minute intervals from the administration of spinal anaesthesia until delivery. After delivery, measurements will be obtained at 2-minute intervals until completion of surgery. The following variables will be recorded: Baseline SBP and HR. Lowest SBP

Official title: Comparison of Prophylactic Continuous Infusion of Norepinephrine, Ephedrine, and Their Combination for Prevention of Hypotension During Spinal Anaesthesia for Caesarean Delivery: A Randomized Controlled Trial

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