Definition
The foot block is a regional anesthetic procedure to perform painless operations or wound care on the foot. Around the lower leg, just above the ankle, local anesthetic is injected at several points, thus blocking nerve transmission at this point. The entire foot is not sensitive to pain. The mobility of the foot is not completely suppressed because some of the muscles for foot movement are located in the lower leg. It is a relatively low side effect procedure.
How is a foot block performed?
After precise planning of the procedure and education of the patient, the puncture site, in this case the lower leg, is sterilely covered. The puncture sites, in the case of the foot block these are five different sites around the lower leg, are thoroughly disinfected. The skin can be locally anesthetized before the actual anesthesia, so that no pain occurs during the puncture.
The cannula is inserted through the skin and advanced to the nerve. This can be checked by an ultrasound examination. An electrical discharge can also indicate to the anaesthetist whether the nerve has been hit.
The local anesthetic is injected near the nerve. Since several large nerves run through the lower leg, this procedure must be repeated five times until the entire foot is anaesthetized. The effect of the drug sets in after about fifteen minutes.
The foot first starts tingling and then becomes numb. Once the foot is completely numb, the actual procedure can begin. In most cases, a green cloth is stretched between the surgical field and the patient’s head to protect the sterile environment. Therefore, the patient usually cannot watch the operation.
What are the risks?
Regional anesthesia, and thus also the foot block, is a procedure with relatively few side effects. Allergic reactions are possible locally. If an injection is accidentally made into the nerve, and not next to it as planned, nerve damage and sensation may occur.
In rare cases, a systemic, i.e. an allergic reaction affecting the entire body, up to and including allergic shock, may occur. For this reason, a different procedure should be chosen in case of a known allergy to the local anesthetic. If the local anaesthetic enters the bloodstream unplanned, stronger side effects are possible.
Nausea, dizziness, drowsiness and restlessness may occur. The anaesthetist tries to prevent this by retracting the plunger of the syringe before the injection and testing whether there is blood in the syringe. In rare extreme cases, seizures and respiratory paralysis are possible.
Local anesthetics also have an effect on the cardiovascular system. The strength of the heart and the frequency of strokes decrease and the blood pressure can drop. In some cases, cardiac dysrhythmia can develop and even lead to sudden heart failure. Since these side effects occur particularly in patients with decompensated cardiac insufficiency or conduction disorders, another anaesthesiological procedure, usually general anaesthesia, should be used in these cases.
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