The Approach
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Review radiographs and locate the wrist fracture. Mark the area you plan to inject with a pen.
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Have the patient supine on the stretcher. Dissuade the patient from watching you complete the setup and injection.
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Wash the skin well with soap and water to remove any excess blood or debris.
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Obtain cleaning solution such as alcohol, chlorhexidine, or Betadine, and clean the injection site.
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Draw up 10 mL of 1% or 2% plain lidocaine into a 10mL syringe using an 18g needle.
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Change the needle to one with a smaller gauge for injection (22-27g).
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Begin by infiltrating a small wheel above the fracture site on the dorsal aspect of the wrist. Insert the needle at a 90- to 120-degree angle and slowly progress down to the hematoma, aspirating back until you see blood return to the syringe.
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Advance the needle into the hemaatoma just a tiny bit further. Inject lidocaine into the hematoma and around the adjacent periosteum.
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You may feel the needle drop into the space easily.
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Remember to inject the lidocaine slowly. Fill the space with about 8-10 mL of lidocaine, and apply pressure to control any bleeding to the site.
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No need to use an 18-gauge needle for this, and you should warn the patient that it will burn and that he will feel a lot of pressure. It is OK to take breaks during the injection and reassure the patient, instead of quickly injecting and unloading the lidocaine into the hematoma.
The Pause
Wait 15 minutes before manipulating the wrist to allow adequate anesthesia to take effect.
Contraindications
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Do not do a hematoma block for open fractures. These usually go to the operating room and need a washout.
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Do not inject more than 10-15 mL of lidocaine into the fracture site. If you have used 15 mL of 2% lidocaine, that is 300 mg of lidocaine! You must consider toxicity, and don't forget about compartment syndrome with large amounts of fluid in this small space.
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Do not repeat injections into the joint space.
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Do not inject into the volar surface of the wrist.
