Peripheral nerve block is well suited for distal extremity surgery. Blocking the nerves at the distal extremity is easily done. It does not require ultrasound or stimulators to identify the nerve. Blocking nerves in the distal extremity is safe with low risk of toxicity. The effect of the nerve block is limited to the distribution of the nerve. The distal nerves in the lower extremity are sensory branches of the sciatic nerve. This provides a sensory block only. This has the advantage of allowing the patient to actively contract tendons in the foot and ambulate more quickly after surgery.
Key points
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Peripheral nerve block is well suited for distal extremity surgery.
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Blocking nerves in the distal extremity is safe with a low risk of toxicity as a result of smaller dosing of the anesthetic agents required for the smaller diameter and superficial nerves in the distal extremity.
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Blocking the nerves at the distal extremity is easily done, because the nerves are superficial and landmarks easily palpable for safe needle placement.
Introduction
Peripheral nerve block is well suited for distal extremity surgery of the hands and feet. The technique is simple, safe, and effective for obtaining anesthesia in the outpatient clinic or office.
Blocking the nerves at the distal extremity is easily done, because the nerves are superficial and landmarks easily palpable for safe needle placement. It does not require the use of ultrasound or stimulators to identify the nerve.
Blocking nerves in the distal extremity is safe with low risk of toxicity as a result of smaller dosing of the anesthetic agents. Nerves in the distal extremity are smaller in diameter, more superficial, and require less volume to achieve a good block. The effect of the nerve block is limited to the distribution of the nerve only, sparing the other functions in the extremity.
The distal nerves in the lower extremity are sensory branches of the sciatic nerve. This provides a sensory block only and leaves the motor function intact. This has the advantage of allowing the patient to actively contract tendons in the foot, which is useful when doing tenotomies to correct deformities in toes (ie, claw toes or hammer toes). This also allows the patient to ambulate more quickly after surgery and shortens postoperative recovery times.
Patient selection
Patient selection is critical to the success of nerve block anesthesia. The use of a nerve block requires that the patient is agreeable to the procedure, understands the nature of nerve block anesthesia, and is cooperative. This technique is not suitable for patients with language barriers, because cooperation of the patient and verbal feedback are required for this method to be successful. Children and anxious patients are not good candidates for nerve block anesthesia. Mild anxiety can be treated with a mild preoperative sedative to make the patient relaxed. I have learned that patients who say they have difficulty with dental freezing are better suited to general or neuraxial anesthesia.
Indications
Most patients undergoing surgery to the foot desire a limited regional anesthesia rather than a general or neuraxial anesthesia.
Infection is a predominant cause of surgery of the foot. Extensive cellulitis or ascending lymphangitis at the site of the nerve block would preclude utilizing a nerve block technique.
Peripheral vascular ischemia, a common reason for foot surgery, is suitable for nerve block anesthesia as long as no epinephrine is added to the blocking agent. Because the distal nerves are small in diameter and easily accessible, epinephrine is not required to augment the distal nerve block.
Distal extremity nerve block is best suited to operative procedures of 30 minutes or less. Although the nerve block will last for a few hours, the patient will become uncomfortable from positioning the leg for an extended time and not moving. The use of a tourniquet becomes more painful with time when only part of the foot is blocked. Procedures longer than 30 minutes duration are better done under general or neuraxial anesthesia.
Technique
The peripheral sensory nerves are superficial and well localized by easily identifiable landmarks. This allows the Xylocaine to be infiltrated around the nerve for optimal blocking concentration. Not infrequently, Paraesthesia may be elicited if the nerve is touched. The risk of traumatizing the nerve is minimized by ensuring that the bevel of the needle is parallel to the alignment of the nerve being blocked. Smaller-gauge needles minimize damage to the nerve if accidentally touched. It is important to stop injection immediately and withdraw the needle slightly if the patient experiences paraesthesia and pain with infiltration.
To minimize the discomfort associated with injecting Xylocaine, the Xylocaine can be buffered with 2 mL sodium bicarbonate 8.4% in 20 mL of Xylocaine. This reduces the acidity of the Xylocaine and takes away the sting associated with the infiltration. This makes the infiltration of the anesthetic much more tolerable to the patient, who feels a sensation of pressure rather than stinging.
Surgery is done with tourniquet of the extremity ( Fig. 1 A). Using a tourniquet restricts the time of surgery to less than 30 minutes, after which the pressure of the tourniquet becomes painful to the patient. A blood pressure cuff can be used around the calf for a short period of time, but this can be uncomfortable because of compression of the calf muscles. An Esmark elastic bandage can be used to exsanguinate the foot and remain tight around the ankle as a tourniquet (see Fig. 1 B). This is better tolerated by the patient, because the tourniquet pressure is applied to the distal tibia and ankle, minimizing soft tissue and muscle compression, which can be uncomfortable. Fig. 1 C shows the beginning of surgery.
