The Severity Of Hypotension Comparing Three Positions During Spinal Anesthesia For Cesarean Delivery
Condition: Hypotension
MeSH terms: Hypotension
Study type: Interventional

Summary: 
      The investigators intend to study the impact of patient positioning on the changes in blood
      pressure after spinal anesthesia for cesarean delivery. The investigators hypothesized that
      the changes in blood pressure relate to the speed with which the spinal medication rises. By
      slowing the rise of spinal anesthesia, the investigators believe that the incidence and
      severity of hypotension might be reduced.
    

Detailed description: 
      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.

      The investigators hypothesize that the position patients are in during spinal placement might
      play a role in the severity of maternal hypotension. Interestingly, very few studies have
      investigated this posibility. Gori, et al. (1) studied influence of seated versus lateral
      positioning for spinal placement in Cesarean section. They found no significant differences
      in onset times, Bromage score for motor block, recovery dynamics, and use of ephedrine in two
      different positions; however, they did not compare the incidence and severity of spinal
      hypotension. Yun, et al. (2) found that the severity and duration of hypotension were greater
      when hyperbaric bupivacaine and fentanyl were induced in the sitting position compared to
      lateral.

      Of notice, in all these studies, the authors focused on the immediate positions when the
      spinal mediation was injected; none has examined the effect of positioning after injection
      during phase when spinal anesthesia is rising.

      Density differences between intrathecal injectate and CSF may explain the observed postural
      differences in extent of sensory block. Thus, the height of spinal anesthesia blockade could
      be affected by patient positioning during and after spinal injection. A small incline in
      positioning immediately after spinal injection may slow the rise of spinal blockade without
      affecting the duration of spinal anesthesia. In the current protocol, the investigators
      hypothesize that by slowing the rise of spinal anesthesia, the investigators might reduce the
      severity of hypotension.
    

Intervention name(s): Position
Intervention type(s): Other
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: spinal anesthesia; hypotension; pregnancy