Effect of 90% Effective Dose of Metaraminol in Supine and Left Tilt Positions on Cesarean Section

Effect of 90% Effective Dose of Metaraminol in Supine and Left Tilt Positions on Cesarean Section：A Non-inferiority Trial

For hypotension after spinal anesthesia, metaraminol has different 90% effective doses in the supine position and the left-tilt position. We plan to conduct a non-inferiority trial to compare the effects of the two on the fetus and the mother.

Inclusion Criteria:

1. Singleton pregnancy at term scheduled to be delivered via elective cesarean delivery;
2. height 150-180 cm;
3. American Society of Anesthesiologists (ASA) physical status II-III;
4. body mass index (BMI) <35 kg/m2.

Exclusion Criteria:

1. transverse presentation, fetal macrosomia;
2. uterine abnormalities (eg, large fibroids, bicornuate uterus);
3. polyhydramnios;
4. ruptured membranes, oligohydramnios;
5. intrauterine growth restriction;
6. gestational or nongestational hypertension, diabetes, or eclampsia;
7. hypertensive disorders or any condition associated with autonomic neuropathy (such as diabetes mellitus for >10 years) or renal failure;
8. contraindications for combined spinal-epidural anesthesia;
9. participants who declined to sign informed consent forms.