The axillary nerve block is a common form of regional anesthesia providing temporary pain relief and muscle relaxation for procedures involving the arm, forearm, wrist, or hand. This technique involves injecting a local anesthetic solution near the specific bundle of nerves that control sensation and movement in the distal upper limb. Targeting these nerves in the armpit, or axilla, effectively numbs the surgical area, often allowing the patient to remain awake. The goal is to prevent the transmission of pain signals, ensuring a comfortable and pain-free surgical experience without general anesthesia.
Targeted Anatomy What Areas Are Blocked
The axillary approach specifically targets the terminal branches of the brachial plexus, the network of nerves originating from the neck. At the level of the axilla, these nerves have separated and are clustered closely around the axillary artery, making this a practical injection location. The principal nerves blocked are the median, ulnar, and radial nerves, which provide motor and sensory supply to the elbow, forearm, wrist, and hand.
The resulting numbness and temporary paralysis affect the forearm, wrist, and hand, making the block highly effective for procedures below the elbow. However, the musculocutaneous nerve, which supplies the biceps muscle and sensation to the lateral forearm, often separates from the main nerve bundle higher up in the armpit. This nerve may require a separate injection to ensure a complete block; if missed, it can result in incomplete numbness along the outer forearm.
The axillary nerve block typically spares nerves that control the shoulder and upper arm, such as the axillary nerve itself and the medial brachial cutaneous nerve. Because of this anatomical distinction, the axillary block is not suitable for procedures requiring anesthesia of the shoulder or the proximal upper arm.
The Procedure Step-by-Step Administration
Patient preparation begins with careful positioning, usually lying on their back with the arm to be blocked abducted and often bent at the elbow. Standard monitoring equipment is applied to track heart rate, blood pressure, and oxygen saturation throughout the procedure. Before the injection, a small amount of local anesthetic may be used to numb the skin at the needle insertion site, minimizing patient discomfort.
Administration relies heavily on guidance technology, with ultrasound being the standard for visualizing internal anatomy. A gel is applied to the skin, and an ultrasound probe locates the axillary artery, which serves as a reliable landmark. The median, ulnar, and radial nerves appear on the screen as small, bright structures clustered around the dark, pulsatile image of the artery.
A thin needle is then advanced toward the targeted nerves under continuous ultrasound visualization. The goal is to place the needle tip immediately adjacent to the nerves without penetrating them directly. As the local anesthetic solution is injected, the clinician watches the ultrasound screen to confirm that the medication spreads circumferentially around the nerves, bathing them completely. Patients may feel a sensation of pressure or fullness during the injection, but this should not be painful.
To ensure comprehensive coverage, the clinician may perform multiple small injections, targeting each of the main terminal nerves individually, including the musculocutaneous nerve. The entire process of positioning and injection typically takes only a few minutes. Following the injection, the local anesthetic solution begins to work, and the patient usually feels a warm, tingling sensation in the limb within minutes.
The full onset of the block, characterized by complete numbness and loss of muscle control in the forearm and hand, generally occurs within 15 to 30 minutes. During this period, the patient remains under observation as the regional anesthesia takes effect. This controlled onset time allows the clinical team to confirm the density of the block before proceeding with the surgical procedure.
Clinical Applications and Patient Selection
The axillary nerve block is a favored anesthetic method for a wide range of surgical procedures performed below the elbow. Common indications include carpal tunnel release, fracture repair of the wrist or hand, and tendon or ligament repairs in the forearm. It is also frequently utilized for operations on the elbow, although a successful block of the musculocutaneous nerve is important for these more proximal procedures.
A significant advantage of this regional technique is avoiding general anesthesia, which carries risks, particularly for patients with pre-existing respiratory or cardiac conditions. By targeting only the nerves supplying the surgical site, the block minimizes the risk of respiratory complications, such as temporary diaphragm paralysis, sometimes associated with nerve blocks placed higher in the neck. Patients who receive the axillary block often experience less post-operative nausea and tolerate oral intake sooner than those who received general anesthesia.
The block provides excellent post-operative pain control. The local anesthetic remains active in the tissues for several hours after the procedure is complete, typically lasting between four and 24 hours. This extended period of numbness means that patients wake up from surgery without immediate pain, reducing the need for high doses of systemic opioid pain medication in the immediate recovery period.
Managing Risks and Recovery
While the axillary nerve block is considered a low-risk procedure, patients should be aware of potential, though infrequent, complications. The most common minor side effects include temporary localized bruising or slight discomfort at the injection site. A rare but reported risk is systemic toxicity, which occurs if the local anesthetic is inadvertently injected into a blood vessel, emphasizing the safety benefit of ultrasound guidance.
Temporary nerve irritation, felt as tingling or a persistent patch of numbness after the block wears off, is reported in a small percentage of patients. This feeling is usually temporary, resolving fully within a few weeks or months as the nerve recovers from the local anesthetic. Permanent nerve damage is an extremely rare event, with estimates suggesting it occurs in fewer than 1 in 5,000 cases, a risk mitigated by the precision of ultrasound visualization.
The recovery phase begins as soon as the local anesthetic takes effect, rendering the arm numb and heavy. The duration of this effect varies depending on the specific anesthetic agent used, but generally lasts an average of 10 to 12 hours. During this period, protecting the anesthetized limb is paramount to prevent accidental injury, as the patient cannot feel pain or temperature. Practical measures include:
- Keeping the arm in a sling.
- Avoiding exposure to extreme heat or cold.
- Avoiding sharp objects.
- Avoiding any activity that requires fine motor control.
As the block begins to wear off, the sensation of numbness is gradually replaced by a return of feeling and muscle function, sometimes accompanied by a tingling sensation. Patients should transition to oral pain medication before the block completely resolves to manage post-surgical pain effectively. If numbness or weakness persists for an unusually long period, patients must contact their healthcare provider for further evaluation.