Comparison of Three Different Sitting Positions for Performing Combined Spinal-Epidural Anesthesia

Positioning of patients plays a major role to identify accurately epidural and/or spinal spaces for neuraxial blocks. Flexed back is considered mandatory to widen the inter spinous space in traditional lateral and sitting positions. In traditional sitting position (TSP), the patient is positioned in a sitting posture on the operating table. A stool is placed by the side of the operating table to support the legs. Both hips and knees are maximally flexed.

In recent years, several studies suggested that the reduction of lumbar lordosis may increase the success rate of spinal or epidural block and reduce needle-bone contact. Different modified sitting positions were described for this aim: the harmstring stretch position (HSP), the squatting position (SP), and the crossed-leg position (CLP).

In modified sitting positions, the patients sit up from supine position with the legs remaining on the operating table, either knees are maximally extended (the harmstring stretch position), or hips and knees are maximally flexed (the squatting position), or hips and knees are flexed with crossing the legs (the crossed leg position). All studies comparing modified sitting positions with TSP found that the success rate and number of needle bone contacts were similar except one study which reported a lower needle bone contact with squatting position. Other factors contributing the success of the neuraxial block were: anatomical landmarks (palpability of the spinous processes, identification of the midline), immobilization of the patient during the injection, and the provider's level of experience.

The combined spinal - epidural (CSE) technique has been increasingly used for over thirty years which consist of intentional injection of a local anesthetic into the subarachnoidal space and the placement of a catheter into epidural space to prolong or modify the block.

Although CSE technique combines the best features of spinal and epidural blockade, it is a more complicated to perform. Studies comparing CSE with epidural and/or spinal technique reported similar failure rates but most of them did not focuse on the effect of patient's positioning.