Battling Hypotension in Cesarean Section

Abstract

Perhaps the greatest day in a mother's life is the birth of her child. As a father of two, I will never forget those two drastically different, yet equally beautiful moments. In each circumstance, the obstetricians, nurses, anesthesia providers, and technicians all worked seamlessly to provide a safe and enjoyable childbirth experience for our new and growing family. One key element of the childbirth experience is maternal pain control. Depending on several factors, the parturient may receive an epidural, a spinal, a combined spinal/epidural, IV analgesics or perhaps nothing at all. One key commonality after any anesthetic administration is its propensity to cause hypotension, which is usually most profound after spinal anesthesia (SA). SA is the preferred method during elective cesarean sections due to the rapid and predictable onset and duration of action of local anesthetics injected directly into the cerebrospinal fluid. Immediately after SA is administered, the patient is helped to lay supine which assists the hyperbaric local anesthetic to move with gravity and rise cephalad from the lower lumber injection site (L3-L5) towards the desired T4 vertebra. While marching up those 12 dermatome levels, the local anesthetic quickly begins to attenuate sympathetic tone at every level along the way. Depending on the health of the patient's cardiovascular system, intravascular volume status and other factors, the sympathectomy and subsequent vasodilation can result in significant and symptomatic hypotension, causing a vast array of symptoms such as maternal nausea, vomiting, dizziness, and cardiovascular collapse as well as fetal acidosis and decreased Apgar scores. Preanesthesia fluid boluses are commonly administered in hopes to increase intravascular volume and lessen the severity of hypotension, but its effectiveness is unreliable. Acute arterial vasodilation is the primary cause of hypotension after SA. Intravenous vasoactive medications such as phenylephrine and ephedrine offer the fastest and most effective means of arterial vasoconstriction and subsequent correction of blood pressure; yet healthcare providers will always continue to search for alternative and less invasive methods of preventing and/or treating hypotension after SA.