SAPHENE AND SCIATIC NERVE BLOCK IN DOGS (analgesia/anesthesia for knee surgery)

Sciatic-nerve-blockade-dogs

Author: within this discipline

EBVS & RCVS Specialist in Veterinary Anaesthesia and Analgesia

In this article, Miguel Martínez Fernández, our veterinarian with a European Diploma in Anesthesia and Analgesia, tells us how to perform a correct saphenous and sciatic nerve block in dogs.

The use of regional anesthesia techniques allows optimal control of analgesia during and after knee surgery.The sensory and motor innervation of the hind limb comes from the ventral rami of the lumbosacral trunk of the spinal cord.

Specific, the innervation of the knee area comes mainly from the saphenous nerves (branch of the femoral nerve) on the medial side and from the sciatic nerve on the anterior, posterior and lateral sides. In some dogs (10-20%) there is a contribution from the obturator nerve.

We aim perineural injection of an appropriate volume and concentration of anesthetic Locally, it transiently blocks the transmission of the nociceptive impulse through ascending sensory pathways and prevents sensitization of the central nervous system (anesthesia/analgesia).

HOW TO PERFORM THE BLOCK OF THE SAPHENE AND SCIATIC NERVE IN DOGS

Saphenous and sciatic nerve block for knee surgery it can be done by blind localization using anatomical landmarks or by ultrasound visualization (ultrasound-guided), which is ideal. The block is extremely effective and easy to perform and complications are rare, allowing a reduction in the use of other anesthetics and analgesics (balanced anesthesia). The use of loco-regional anesthesia is known to reduce anesthetic morbidity and mortality in dogs.

LOCATION OF THE SAPHENE NERVE

The saphenous nerve is located on the medial aspect of the thigh, superficially accompanying the femoral artery and vein. (Photo 1).

saphenous and sciatic nerve block in dogs
Photo 1

For a blind block, the nerve is located cranial to the artery, which is easily located by palpating the pulse (Photo 2).

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Photo 2

Ultrasound visualization is simple by placing a linear probe in the middle of the medial aspect of the thigh transverse to the longitudinal axis of the femur (Photo 3). For knee surgery, it is recommended to use long-acting local anesthetics such as bupivacaine 0.5% or ropivacaine 0.5% at approximate volumes of 0.1ml/Kg (although this depends on the ultrasound visualization of the local anesthetic around the nerve). The saphenous nerve is only sensitive, so it does not produce motor paralysis of any innervated muscle (it maintains the mobility of the quadriceps).

saphenous nerve block
Photo 3

LOCATION OF THE SCIATIC NERVE

The sciatic nerve (composed of the common tibial and peroneal nerves within the same sheath) runs through the caudo-lateral aspect of the thigh from the trochanteric fossa between the powerful muscles of the area (Photo 4). For blind blockade, it can be easily located 1-2 cm deep in the trochanteric fossa between the greater trochanter of the femur and the ischial tuberosity (deep plane of the gluteal muscles) (Photo 5).

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photo 5

For the ultrasound-guided block, we placed the linear probe perpendicular to the longitudinal axis of the femur distal to the trochanteric fossa on the lateral aspect of the thigh (Photo 6). Local anesthetic injection (approximately 0.1 mL/kg) produces a long-lasting sensory block (analgesia) and a shorter-lasting motor block.

Performing this block is simple with a little practice and provides optimal conditions for surgery and patient recovery.. Once you try it, you won't be able to do without it.

And remember, if you want to expand your knowledge about the saphenous and sciatic nerve block in dogs, consult our courses, always carried out by qualified specialists of international prestige.