الفهرس 
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Abstract
Sciatic nerve block (SNB) has become increasingly popular for anesthesia or analgesia during lower limb procedures. There are several techniques for SNB.
Ultrasound guided techniques are based on direct ultrasound visualization of nerves, needle, and adjacent anatomic structures, making it possible to apply the local aesthetic precisely around nerves and to follow its distribution in real time, achieving a more effective blocked, with reduced latency, decreased dependency on anatomic landmarks, reduced volume of local anesthetics, and increased safety. Therefore the use of ultrasound is capable of offering several potential advantages when compared to the (blind) techniques. The sciatic nerve (L4,5. S,1,2,3) supplies nearly the whole of the skin of the leg, the muscle of the back of the thigh, and those of the leg and foot. It is the largest peripheral nerve in the body, measuring about 2 cm in breadth, and is the continuation of the flattened band of the sacral plexus.
Anesthesiologist, must understand some basic ultrasound principles that are relevant to clinical practice, such as, the choice of transducer based on simple fact that high frequency probes allow high resolution but have limited depth of penetration, while lower frequency probes allow greater depth but with less resolution.
However, despite the research suggesting that ultrasound guidance during nerve block procedures allows reduction of total dose/ volume of local anesthetic, the doses and volume used for reliable blockade by many clinicians are still capable of producing significant systemic toxicity. Therefore, precautions during nerve blockade and in the choice of local anesthetics should be adhered to regardless of ultrasound guidance utilization. Beside basic monitoring full resuscitation equipment must be available and access to intralipid is recommended.
Important ultrasound guided sciatic nerve block approaches include:
- Anterior approach , medial mid thigh approach , both can be done in supine position .
- Posterior approach which include : Subgluteal approach and parasacral approach . both can be done in lateral or prone positions.
- Popliteal approaches : can be done in supaine or prone positions, for surgery below the knee level
Depending on the surgical indication , SNB can be used on its own or in combination with an ipsilateral lumbar plexus block or femoral nerve block for surgical anesthesia.
The SNB provides complete anaesthesia of the leg below the knee with the exception of a strip of medial skin innervated by saphenous nerve .
Combained with femoral or saphenous nerve block , it provide analgesia for surgery of the distal thigth , knee , calf , ankle , or foot . It also provide analgesia when a thigth tourniquet is required ..