Location of CSE with spinal dural needle

Intramural block is usually performed while the patient is sitting, especially in obese patients, because the midline is easily recognized. Sitting has been shown to help women bend their spine better. In addition, the distance from the skin to the epidural space is significantly greater when epidural puncture is performed in the lateral decubitus position compared to the sitting position. This change in distance may cause the catheter to shift when the patient moves from sitting to lying on the side, resulting in inadequate analgesia.

Yun et al. compared CSE anesthesia induction in sitting and lateral decubitus positions in healthy women undergoing elective cesarean sections. The severity of hypotension, as measured by the maximum percentage decrease and duration of systolic blood pressure compared to the control group, was significantly higher in the sitting group (P < 0.05). Twice as much ephedrine was required to treat hypotension in the sitting group as in the lateral decubitus group. The reasons for the differences in hypotension severity are unclear. They hypothesized that this was related to the slower recovery of venous stasis in the lower extremities from the initial sitting position assumed supine.

It has traditionally been taught that the propagation of high-pressure intrathecal solutions follows gravity. Lewis et al. compared the development of left decubitus and supine wedge spinal blocks after CSE in a sitting position. Intrathecal administration consisted of 2 mL 0.5% high-pressure bupivacaine and 15 μg fentanyl. No unilateral block occurred in the left decubitus position. The left decubitus position was associated with slower block occurrence (P =.004), but the resulting block had similar characteristics to those obtained in the supine wedge position. The left decubitus position is known to improve maternal cardiac output, and the possible benefits to the fetus may outweigh slow onset.

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