Aortocaval Compression Syndrome: Time to Revisit Certain Dogmas

Area of Science:

• Obstetrics and Gynecology
• Anesthesiology
• Maternal-Fetal Medicine

Background:

• The practice of avoiding the supine position in late pregnancy, particularly during cesarean delivery, stems from the phenomenon of "postural shock" described over 70 years ago.
• Pelvic tilt is a standard measure to prevent aortocaval compression, based on older, non-randomized studies using varied anesthetic techniques and avoiding vasopressors.

Purpose of the Study:

• To re-evaluate the evidence surrounding aortocaval compression and the necessity of pelvic tilt in contemporary obstetric anesthesia.
• To appraise current clinical guidelines in light of recent physiological and clinical findings.

Main Methods:

• Review of historical and recent evidence on aortocaval compression and its management.
• Analysis of magnetic resonance imaging studies on inferior vena cava compression in term gravida.
• Examination of clinical investigations comparing supine and tilted positions during cesarean delivery with modern anesthetic management.

Main Results:

• Recent MRI studies challenge the long-held belief that 15° of left tilt adequately relieves inferior vena cava compression.
• A clinical trial found no difference in neonatal acid-base status between tilted and supine positions in healthy term women undergoing cesarean delivery, provided maternal blood pressure was maintained with crystalloid coload and phenylephrine.

Conclusions:

• The established practice of routine pelvic tilt may warrant reevaluation in the context of current anesthetic protocols and hemodynamic management.
• Contemporary clinical practice may allow for a more nuanced approach to positioning during cesarean delivery, potentially including the supine position under specific conditions.