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Aortocaval Compression — FRCA Final MCQ

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EasyObstetric AnaesthesiaAortocaval CompressionFRCA Final

A 35-year-old woman at 32 weeks' gestation requires an emergency appendicectomy under spinal anaesthesia. After the intrathecal injection, she is positioned supine with a 15° left lateral tilt. What is the primary physiological purpose of the tilt?

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Correct answer: D — Reduce gravid uterine compression of the great vessels

The correct answer is D. In late pregnancy, the supine gravid uterus can compress the inferior vena cava and, to a lesser extent, the aorta. Left lateral tilt displaces the uterus from these vessels, limiting impairment of venous return, cardiac output and uteroplacental perfusion. A fixed 15° tilt may not completely abolish caval compression in every patient, but this remains its primary physiological purpose. It does not prevent the sympathetic blockade produced by spinal anaesthesia, although relief of aortocaval compression may reduce the severity of associated hypotension. Aspiration risk is addressed by fasting, pharmacological prophylaxis and airway management rather than lateral tilt. Tilt is not primarily intended to control intrathecal spread or improve surgical access.

Reference: Lee AJ, Landau R. Aortocaval Compression Syndrome: Time to Revisit Certain Dogmas. Anesthesia & Analgesia. 2017;125(6):1975-1985. https://pubmed.ncbi.nlm.nih.gov/28759487/