Answer
Infection can occur when the puncture site is not clean. Avoid puncture through infected skin or skin lesions. Be sure to use sterile technique during the procedure, as the risk of infection is insignificant when sterility is properly maintained.
Intra-arterial injection may result in vasospasm and lead to ischemia of the limb tissue. Intravenous injection can lead to systemic toxicity in high doses. Tissue texture changes revealing pallor, bogginess, and cool temperature may indicate that either intravascular injection or vascular compression has occurred. Always draw back the syringe to rule out intravascular placement before injection. Alpha-adrenergic antagonists (eg, phentolamine 0.5-5 mg diluted 1:1 with saline) can be administered by local infiltration to relieve arterial vasospasm secondary to intra-arterial injection. [10]
Patients may develop paresthesia, sensory deficits, or motor deficits secondary to inflammation of the nerve. Most often, this type of neuritis is transient and resolves completely. During the procedure, pull back gently after induction of paresthesia so as to not inject the nerve directly. Make sure to document a complete neuromuscular examination both before and after the procedure. [11]
Reports of significant hemorrhage during regional anesthesia are rare, even in patients with blood coagulopathies. [9] A hematoma may develop with intravascular puncture. If prolonged bleeding occurs, attempt to obtain hemostasis with direct pressure and elevation.
Allergic reactions to local anesthetics occur at a rate of 1%. [12, 10] Reactions range from delayed hypersensitivity (type IV) to anaphylactic (type I). Although rare, the most common cause of allergic reaction is the preservative in the local anesthetic solution. Cardiac lidocaine is an alternative because it does not contain the preservative. Alternatively, a 1-2% diphenhydramine solution can be used as a local anesthetic. [10]
The volume of 1% lidocaine without epinephrine should not exceed 5 mg/kg. If lidocaine with epinephrine is used, total volume should not exceed 7 mg/kg. Systemic toxicity manifests in the central nervous and cardiovascular systems. [12] Signs such as tremors, convulsions, tachycardia, or respiratory compromise should alert the physician to stop the procedure and reassess the patient.
-
The posterior tibial nerve courses down the posterior calf.
-
Medial and lateral plantar nerves after branching from the posterior tibial nerve.
-
Cutaneous innervation by the medial and lateral branches of the posterior tibial nerve.
-
Cutaneous innervation of the calcaneal region by the medial plantar nerve.
-
The tibialis posterior tendon, flexor digitorum tendon, posterior tibial artery, posterior tibial nerve, and flexor hallucis longus tendon at the ankle level.
-
Areas of anesthetization to complete an ankle block. This block requires anesthetization of 5 nerves for complete sensory block below the ankle. The areas to anesthetize include a line along the anterior ankle for the superficial peroneal nerve (blue line), the deep peroneal nerve (red star), the saphenous nerve (pink star), the sural nerve (green arrow), and the posterior tibial nerve (orange arrow).
-
Equipment needed for the regional block.
-
Posterior tibial nerve block landmarks. Medial malleolus (MM) is at the left and Achilles tendon is at right. Posterior tibial artery (A) is approximately 1 cm inferior to the site marked for needle insertion (arrow).
-
Palpation of the posterior tibial artery.
-
Marking the injection site, which is 0.5-1 cm superior to the posterior tibial artery.
-
Location of injection site when unable to palpate the posterior tibial artery.
-
Using povidone iodine solution (Betadine) to clean the injection site.
-
Placing a skin wheal.
-
Injection posterior and superior to the posterior tibial artery.
