Investigating Maternal Effects of Positions Applied in Patients Preparing for Caesarean Section Under Spinal Anesthesia

After the approval of the Ethics Committee, 120 patients were planned to be included in the study between 15.06.2022 and 15.01.2023. Women who underwent elective cesarean delivery under spinal anesthesia were randomized to the supine position, 15° left-lateral tilt position, or 30° left-lateral tilt position. The position will be changed to supine before the incision. It was planned to recruit 40 patients from each group, with a total of 120 patients. Anesthetic management was standardized and fluid administration with 10 mL/kg isotonic was planned. Hypotension (systolic blood pressure \[SBP\] reduction \> 20% baseline or SBP \<90 mm Hg) will be treated with intravenous bolus ephedrine based on maternal heart rate. The primary outcome is planned to include maternal SBP in 15 minutes of anesthesia induction, the amount of vasoactive drug administered before the end of surgery, and the incidence of hypotension during cesarean delivery.

Pregnant women in the supine position may compress the Inferior Vena Cava (IVC) by compression of the enlarged uterus in the third trimester. In this way, it is considered that it may reduce the amount of returning blood and cause hypotension. The incidence of this condition, called Supine Hypotension Syndrome, was reported to be 8%-10% (1-3). Spinal anesthesia, decreased sympathetic tonus, decreased systemic vascular resistance, and vasodilation may also cause hypotension in the patient (4).

It was considered that if the uterus is tilted, the pressure on the IVC would be removed, increasing the return, blood volume and cardiac output, improving the fetus, blood supply and oxygen supply (5). However, studies that were conducted so far have not proven significant differences and there is no routine standard practice (6-8). Here, the purpose was to investigate the maternal effects between supine, tilt to the left of 15-degree, and tilt to the left of 30-degree., References

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4. Dyer RA, Reed AR, van Dyk D, et al. Hemodynamic effects of ephedrine, phenylephrine, and the coadministration of phenylephrine with oxytocin during spinal anesthesia for elective cesarean delivery. Anesthesiology. 2009;111:753-765.
5. Kinsella SM. Lateral tilt for pregnant women: why 15-degree? Anaesthesia. 2003;58:835-836.
6. Ellington C, Katz VL, Watson WJ, Spielman FJ. The effect of lateral tilt on maternal and fetal hemodynamic variables. Obstet Gynecol. 1991;77:201-203.
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8. Calvache JA, Mu.oz MF, Baron FJ. Hemodynamic effects of a right lumbar-pelvic wedge during spinal anesthesia for cesarean section. Int J Obstet Anesth. 2011;20:307-311.

Eligibility Criteria:
Inclusion Criteria:

* Elective cesarean delivery with term pregnancy
* Patient's height 150-180 cm
* American Society of Anesthesiologists (ASA) Physical Condition II
* Body Mass Index (BMI) \<35 kg/m2.

Exclusion Criteria:

* Fetal macrosomia
* Uterine abnormalities (e.g. large fibroids, bicornuate uterus)
* Polyhydramnios
* Torn membranes, oligohydramnios
* Intrauterine growth restriction
* Gestational or non-gestational hypertension, diabetes, or eclampsia
* Contraindications for spinal anesthesia