sacral plexus block

sacral plexus block is very much useful procedure in pain management and adjuant to general anesthesia for lower limb surgeries

1. SACRAL PLEXUS BLOCK

2. sacral plexus is formed by the union of the first three sacral nerves and the fourth and fifth lumbar nerves. also connects with the ascending division of the fourth sacral nerve sacral plexus is located on the anterior surface of the sacrum and is separated from the sacrum by the piriformis muscle covered by the parietal portion of the pelvic fascia In front of it lie the ureter, the pelvic colon, part of the rectum and iliac artery and vein

3. Gives off two sets of branches: Collateral and Terminal Collateral : pudendal plexus, hip joint, gluteal structures adductor and hamstring muscles Terminal : greater and lesser sciatic nerves

4. SACRUM: fused , lower five sacral vertebrae attached to iliac bones Posterior sacral foramina: on each side of fused spinous processes - posterior divisions of plexus Not exactly parallel, angling toward the midline Transsacral canal - depth varies from 2.5 cm at S1 to 0.5cm at S4 Transsacral block and Parasacral Block

5. INDICATIONS: Anesthesia for upper thigh, hip, perineum High amputations, relief of sciatic pain Obturator block is not achieved Immediate access to the individual nerves is not possible

6. Prone position pillow under the hips Posterior iliac spine, sacral Cornu Skin wheal is raised lateral and above sacral Cornu 1cm medial and 1cm below PSIS

7. Distance between these wheals is bisected An additional wheal is raised at this level These identify 2,3,4, sacral foramina First sacral foramina - 1-2cm above the 2 foramina in the same line

8. Parasacral block: lateral decubitus position, side to be blocked up The dependant limb should be straightened at the knee and hip, and the limb to be blocked should be flexed at both hip and knee Landmarks

9. The needle is connected to a nerve stimulator. For a single shot, the needle is directed perpendicular to the skin in all planes and strictly horizontal. It is important not to direct the needle medially

10. Plantarflexion of the foot or toes (tibial portion) or Dorsiflexion/eversion of the foot or toes (peroneal division) Contraction of the hamstring muscles (biceps femoris, semitendinosus) above the knee is associated with the motor response, most consistent with success. The mean depth at which response is obtained - 7cms

11. More than an isolated sciatic nerve block Blocks both components of sciatic and posterior cutaneous nerve of thigh Spread of LA also blocks superior and inferior gluteal, pudendal, pelvic splanchnic nerves, the terminal portion of sympathetic trunk, inferior hypogastric plexus and the obturator nerve

12. PARA SACRAL PARALLEL SHIFT

13. COMPLICATIONS: Excessive volume spread proximally may cause sympathetic blockade can cause hypotension Loss of parasympathetic function to bowel, bladder and sphincter may occur Injection into subarachnoid space is a remote risk Needle entering into colon or rectum and bladder and going unnoticed

14. References: Hadzics Cousins and breidenbaugh’s neural blockade and pain management JOURNAL OF NEW YORK SCHOOL OF REGIONAL ANESTHESIA - PARASACRAL NERVE BLOCK BY ELIZABETH GAERTNER, MD