Chung O T in Operative Techniques in Lower Limb Reconstructi

T E C H N I Q U E S 4 Operative Techniques in Plastic Surgery: Lower Limb Reconstruction and Amputation ■■ Local anesthetic selection and volume of injection depend on the goals of the block. ■■

■■ A catheter may be placed for continuous local anesthetic infusion. ■■ Use 0.2% ropivacaine or 0.125% of bupivacaine at 4 to 6 mL/h for continuous infusion, with a patient- controlled bolus of 2 to 4 mL every 30 minutes. ■■ Infusions are generally continued for 2 to 3 days fol- lowing surgery.

For a surgical block, use 20 to 30 mL of 1.5% mepi- vacaine, 2% lidocaine, 0.5% bupivacaine, or 0.5% ropivacaine. ■■ For an analgesic block, use 15 to 20 mL of 0.25% bupivacaine or 0.25% ropivacaine.

■■ Femoral Block: Nerve Stimulator Technique

■■ Adductor Canal Block: Ultrasound- Guided Technique ■■ Position and prepare the patient as for a femoral block. Externally rotating the leg may facilitate access to the adductor canal. ■■ Place a high-frequency linear transducer in a trans- verse orientation over the medial thigh at the midpoint between ASIS and the superior pole of the patella. ■■ Identify the sartorius, vastus medialis, and adductor longus muscles. ■■ The femoral artery and vein lie within the adductor canal. ■■ The saphenous nerve may be visualized just lateral to the artery, beneath the sartorius muscle and the vasto- adductor membrane. ■■ Estimate the depth of the nerve in the ultrasound image. ■■ After sterile skin preparation, place a skin wheal just lat- eral to the ultrasound probe. ■■ The depth of the nerve should guide the insertion site. ■■ Insert the block needle in the plane of the ultrasound image, visualizing the tip of the needle in real-time as the target is approached ( TECH FIG 3 ). ■■ Traverse the sartorius muscle to position the needle tip just lateral to the femoral artery. ■■ A “pop” may be felt as the needle passes through fas- cial layers. ■■ Following patient positioning and preparation described above, identify and mark the inguinal crease. ■■ Standing near the patient’s hip and facing the head, pal- pate the femoral pulse along the crease. ■■ After sterile prep, place a local anesthetic skin wheal 2 cm lateral to the femoral artery pulse. ■■ Insert a stimulating block needle at a 45 to 60 degree angle to the skin in a cephalad direction ( TECH FIG 2 ). ■■ A quadriceps twitch (“patellar snap”) should be elic- ited at a current of 0.2 to 0.5 mA. Redirect the needle until the appropriate stimulation is observed. ■■ Sartorius contraction indicates a needle placement on the anterior division of the femoral nerve. Further advancement of the needle toward the posterior divi- sion of the nerve will usually solve this. ■■ Aspiration of blood indicates intravascular placement. Reposition the needle. ■■ Muscle contraction at a current of greater than 0.5 mA usually indicates inadequate needle-nerve proximity and may result in an incomplete or failed block.

TECH FIG 2  • Positioning and approach for stimulator-guided fem- oral nerve block.

■■ Muscle contraction at a current of less than 0.2 mA may indicate intraneural needle placement. Withdraw the needle slightly before injecting, carefully noting injection pressure. ■■ Avoid high-pressure injection (greater than 15 psi), indicative of an intraneural needle placement. ■■ Once an acceptable motor response is elicited, inject local anesthetic as above. The motor response should terminate with injection (Raj test).

TECH FIG 3  • Positioning and approach for ultrasound-guided adductor canal block.

■■ Take care to avoid the femoral vein, which often lies deep and lateral to the artery, and may not be visible when pressure is applied to the ultrasound transducer. ■■ After careful aspiration, inject a small amount of local anesthetic. ■■ Observe local anesthetic spread in the ultrasound image. This should appear as hypoechoic fluid fill- ing the space deep to sartorius and lateral to femoral artery. ■■ Ensure that local anesthetic is not tracking back along the sartorius muscle, but rather staying contained in the adductor canal while partially surrounding the femoral artery.

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