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4766
A new ultrasound-guided lateral approach for proximal sciatic nerve block: a comparison with the anterior approach and a cadaveric evaluation
Session: MP-05a
Fri, April 20, 8-9:30 am
Shubert (Shubert Complex), 6th floor

Please note, medically challenging cases are removed three months after the meeting and scientific abstracts after three years.

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BACKGROUND
The original landmark-based lateral approach to proximal sciatic nerve block for patients in the supine position was first devised in 1959.
The original lateral approach was found to be technically difficult  to localize the sciatic nerve even performed by an experienced hand using nerve stimulation guidance.
We have introduced ultrasound guidance to facilitate identification of the nerve with the lateral approach.
The lateral approach for proximal sciatic nerve block can be performed in patients lying supine, similar to the ultrasound-guided anterior approach.
Injection level is more proximal than the anterior approach, almost the same as the subgluteal approach that can reliably block the posterior femoral cutaneous nerve simultaneously.
The frequency of concomitant blockade of the posterior femoral cutaneous nerve would be promising.
 
METHODS

Clinical Evaluation

Study Design

•Prospective, randomized, controlled, observer-blind, trial

Inclusion Criteria

•Patients who were scheduled for unilateral knee surgery

Exclusion Criteria

•Patients refusal
•ASA PS ≥4
•Inability to communicate
•Age <20 years old
•Body weight <40 kg
•Body mass index >35 kg/m2
•Allergy to local anesthetic
•Pre-existing sensory impairment in the lower extremities
•Infections at the injection site
•Surgical history involving the hip or femur on the present operated side

Primary outcome

•The frequency of complete blockade of the posterior femoral cutaneous nerve assessed by pinprick 30 min after the sciatic nerve block  

Secondary outcomes

•The frequency of complete sensory block in the area supplied by the sciatic nerve
•The frequency of motor sciatic nerve block
•Pre-scan time required to identify the sciatic nerve under ultrasound
•Sciatic nerve block performance time (time from initial insertion to withdrawal of the needle)
•The depth of sciatic nerve (distance from the skin to the sciatic nerve)
•The needle depth (distance from the skin to the needle tip during injection of local anesthetic)
•The incidence of adverse effects (e.g. inadvertent vessel puncture, LAST, infection) 

Cadaveric Evaluation

The ultrasound-guided lateral approach was simulated in four legs in three female adult cadavers using 20 ml of water-soluble dye to validate the feasibility that the injectate would reach both the sciatic and the posterior femoral cutaneous nerves. 

 

CONCLUSIONS

The technical difficulty of the lateral approach can be alleviated by ultrasound guidance.
The ultrasound-guided lateral approach for proximal sciatic nerve block can be performed as successfully as the anterior approach.
The ultrasound-guided lateral approach provides concomitant blockade of the posterior femoral cutaneous nerve more often than the anterior approach. 
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