Continuous Popliteal Nerve Block: Intertendinous Approach
- Indications: Ankle and foot surgery
- Landmarks:
- Popliteal fossa crease
- Tendons of the semitendinosus
- Semimembranosus muscles
- Nerve stimulation: Twitch of the foot or toes at 0.2-0.5mA current
- Local anesthetic: 35-45 mL
- Complexity level: Advance
Continuous popliteal block is an advanced regional anesthesia technique and solid experience with the single-shot technique is recommended to ensure its efficacy. The technique is similar to the single-shot injection, however, slight angulation of the needle cephalad is necessary to facilitate threading the catheter. Securing and maintenance of the catheter are easy and convenient. This technique can be used for surgery and postoperative pain management in patients undergoing a wide variety of lower leg, foot, and ankle surgeries. |
The patient is placed in the prone position with the feet protruding off the table to facilitate monitoring of the foot or toe responses to nerve stimulation. |
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A standard regional anesthesia tray is prepared with the following equipment:
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The landmarks for continuous popliteal are essentially the same as those in the single-shot technique. These include:
- Popliteal fossa crease
- Tendon of biceps femoris (laterally)
- Tendons of semitendinosus and semi-membranosus muscles (medially)
The needle insertion site is marked at 7 cm proximal to the popliteal fossa crease and between the tendons of the biceps femoris and semitendinosus muscles.
The continuous popliteal block technique is similar to the single-shot technique. With the patient in the prone position, infiltrate the skin with local anesthetic using 25-gauge needle at the injection site, 7 cm above the popliteal fossa crease and between the tendons of biceps femoris and semitendinosus muscles. A 5-10 cm needle connected to the nerve stimulator (1.5 mA current) is inserted at the midpoint between the tendons of the biceps femoris and semitendinosus muscles. Advance the block needle slowly with a slight cranial direction while seeking a plantar or dorsiflexion of the foot or toes. After obtaining appropriate twitches, continue manipulating the needle until the desired response is seen or felt using a current of 0.5 mA to 0.2 mA. After negative aspiration for blood, inject 35-45 mL of a local anesthetic of choice. |
The catheter should be advanced some 5 cm beyond the needle tip. The needle is then withdrawn back to the skin, while simultaneously advancing the catheter to prevent its inadvertent removal. TIP: When insertion of the catheter proves difficult, lowering the angle of the needle or rotating the needle should be attempted. |
Before activating, the catheter is checked for inadvertent intravascular placement by negative aspiration test for blood and
injecting an epinephrine-containing local anesthetic. A number of techniques to secure the catheter to the skin have been
proposed. A benzoin skin preparation, followed by application of a clear dressing is one of simplest and most efficacious methods.
The infusion port should be clearly marked as: "continuous popliteal block." |
Continuous infusion
Continuous infusion is initiated after an initial bolus of local anesthetic through the catheter. For this purpose, we routinely use 0.2% ropivacaine (15-20 mL). Diluted bupivacaine or l-bupivacaine are also suitable, but may result in more motor blockade. The infusion is maintained at 10 mL/hr or 5 mL/hr when a PCA dose is planned (5 mL).
TIPS:- Breakthrough pain in patients on continuous infusion is always managed by administering a bolus of local anesthetic. Increasing the rate of infusion only is never adequate. With patients on the ward, a higher concentration of a shorter acting local anesthetic (e.g., 1% mepivacaine or lidocaine) is useful to both manage the pain and test the position of the catheter.
- When the bolus injection through the catheter fails to result in blockade after 30 minutes, the catheter should be considered dislodged and it should be removed.
- Patients receiving continuous nerve block infusion should also be prescribed an alternative pain management protocol because incomplete analgesia and catheter dislodgment can occur. For inpatients, this is probably best done using a back-up IV PCA.
Some general and specific instructions on possible complications and how to avoid them.
| Infection | - Use a strict aseptic technique |
| Local anesthetic toxicity |
- Systemic toxicity after popliteal block is rare - Absorbtion of the local anesthetic from the popliteal fossa is very slow due to the low vascularity of the adipose tissue in the fossa |
| Vascular puncture | - Avoid medial redirection of the needle, because the vascular sheath is positioned medially and deeper as compared to the sciatic nerve |
| Nerve injury |
- Exceedingly rare; use nerve stimulation and slow needle advancement; do not inject when the patient complains of pain or high pressures on injection are met; do not inject when stimulation is obtained at < 0.2 mA current (100 µsec) - Avoid a combination of epinephrine in local anesthetic and application of tourniquet over the injection site to decrease the risk of prolonged ischemia of the nerve |
| Hematoma | - Stop needle insertion when patient complains of pain; this typically indicates insertion of the needle through biceps or semitendinosus muscle; increasing the current output of the nerve stimulator helps distinguish between the two |
| Other | - Instruct the patient on the care of the insensate extremity |
- di Benedetto P, Casati A, Bertini L, Fanelli G, Chelly JE: Postoperative analgesia with continuous sciatic nerve block after foot surgery: a prospective, randomized comparison between the popliteal and subgluteal approaches. Anesth Analg 2002; 94:996-1000.
- Ilfeld BM, Morey TE, Wang RD, Enneking FK: Continuous popliteal sciatic nerve block for postoperative pain control at home: a randomized, double-blinded, placebo-controlled study. Anesthesiology 2002; 97:959-65.
- Singelyn FJ, Aye F, Gouverneur JM: Continuous popliteal sciatic nerve block: an original technique to provide postoperative analgesia after foot surgery. Anesth Analg 1997; 84:383-6.
