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Field block is a technique of injecting anesthetic around a wound rather than into the wound itself. By surrounding an area with anesthetic, the nerves proximal to the injection site are anesthetized but the tissue to be repaired is not infiltrated. This is useful in areas such as the ear, which should not be infiltrated directly. Typical field blocks involve injecting agent in all four directions around the target area. |
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Abscesses requiring incision and drainage can be challenging to adequately anesthetize. Passing a needle through infected tissue can spread the infection. The skin to be incised rests directly over a collection of pus, which makes infiltrating under this skin less for several reasons. Because the underlying tissue is stretched and distorted by the fluid collection, injecting directly into the abscess may not deliver an adequate amount of drug to the nerves of the overlying tissue. |
| The acidic environment of the abscess also inhibits action of the drug. Injecting additional fluid into an abscess, which is already under pressure, can make the area much more painful. For these reasons, a field block around the area to be incised is more effective. The skin to be incised may also be anesthetized through an intradermal injection. This involves inserting a 27- to 30-gauge needle at an oblique angle just under the epidermis and infusing a small amount of agent, taking care to avoid going deeper into the abscess itself. When the needle is properly positioned intradermally, the skin around the needle should blanch when drug is infused. |
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| link to auricular block |
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