The Severity Of Hypotension Comparing Three Positions During Spinal Anesthesia For Cesarean Delivery

Spinal anesthesia is the most commonly used anesthetic for cesarean delivery. In part, this is due to the ease of administration, reliability and low rates of adverse effects. Additionally, the avoidance of general anesthesia allows the parturient to participate in the birth experience, despite being in surgery.

Although hyperbaric local anesthetic solutions have a remarkable record of safety, their use is not totally without risk. The side effects of spinal anesthesia are well described, but most notably include hypotension (low blood pressure). Spinal hypotension is primarily due to the vasodilatory effects of local anesthetics, and would occur in virtually all women if not prevented or treated.

The incidence of hypotension in both the literature and in clinical practice ranges from 30% to 50% of all patients. Recent literature using a continuous, non-invasive blood pressure monitor suggests that hypotension occurs with greater frequency and may be associated with a higher incidence of adverse effects to either mother or fetus. The incidence and degree of hypotension have been associated with fetal acidosis, which is a sign of either poor perfusion of the placental bed, or increased metabolism due to the blood pressure medications.

The most effective treatment for spinal hypotension is uterine displacement using a hip wedge; the use of a hip wedge after spinal anesthesia is a standard of care. Other treatment, including fluid administration of either crystalloid or colloid, are either partially effective, clinical impractical, or result in administering large doses of medications that may have negative effects on the fetus.

Epidural anesthesia is associated with a reduction in the incidence and severity of hypotension compared with spinal anesthesia. This is believed to be due to the slower onset of sympathetic blockade with epidural anesthesia; this slow onset allows the physiologic compensation to changes in blood pressure. Unfortunately, the slower onset and lower reliability of epidural anesthesia prevents routine use in clinical practice for cesarean delivery.