Soundings: Needle in a haystack

Ultrasound-guided identification of foreign bodies could make finding the needle a lot easier.

 

It’s your third night in a string of four. It’s 4am and you are hours behind. As you stumble more than glide through the department on the way to see your next patient, you hear a small voice echo inside your head. It is an admonition you have heard more than once from an esteemed colleague: “pass-ons kill”.

You walk in to see your next patient. The chief complaint is “Splinter”. You introduce yourself, smile, shake hands with the patient and her husband. Your patient explains she was shuffling her way barefoot to the bathroom in the dark when she felt a sudden pain in the ball of her right foot. It was a huge splinter and when she tried to pull it out, it broke. She shows you her half and it looks quite large, as does the puncture wound on her foot. You let them know that the department is very busy and you’ll try to get the splinter out as soon as you can, but it will probably be at least an hour wait. In the mean time you are going to order some medication for her. In and out of the room in under 3 minutes you do the easy stuff – order a procedure tray, a tetanus booster, a Vicodin and some PO Keflex. Knowing an X-ray will be useless for locating unpainted wood, you ask the tech if they can plug in the bedside ultrasound machine. You hope triage will stay empty and hopefully by 5am you’ll be caught-up enough to try to get that splinter out before she and her husband grow too impatient.

 

Sometimes an hour makes all the difference in your state of mind and the state of the department. By 5:15 you have magically dispo’d all of your sign-outs as well as five more of your own patients. What a relief! Your patient with the splinter seems a bit peeved when you enter the room. You should have told her it would be an hour and a half. However, both she and her husband seem easily distracted by the ultrasound machine once you turn it on and start to explain how it works. Your explanations also end their wonder about why X-rays were never done. Everyone likes a little technology, so you give them a quick tour of the foot with the machine, showing them what bones and muscle look like on-screen (below).

 

Then, before focusing on the area of interest, you explain the risks and benefits of trying to remove a foreign body that cannot be easily located by physical exam alone. You explain that the anatomy of the foot is complex, and that the task is a lot closer to looking for a needle in a haystack than most people think. You let them know ahead of time that if you can’t locate the splinter easily, say within five to ten minutes, the risk for causing more tissue damage will outweigh the benefits of continuing the search. You explain how you often have to refer these types of injuries to a surgeon who could remove the splinter in the operating room some time in the upcoming week. Finally, you explain the role of the ultrasound machine to help improve your odds, which are probably “50-50” at best. You then place your small parts probe on the area near the puncture wound and obtain the following image.

 

 

What do you see? What should you do next?

See next page for answer. 

 

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Finding: Map it, numb it, remove it 

 

 

 

 

You have located the wood splinter, which appears as a linear hyperechoic structure, in the foot (top). It is not there on the comparison view of the other foot (bottom). Using the small parts ultrasound probe you map out the location and direction of the splinter and decide to go for it. After appropriate anesthesia and sterile preparation you use the ultrasound machine to guide an 18-gauge syringe-less hypodermic needle tip to the near end of the splinter. You then clean your probe with a sanitizing surface wipe and place it in the holder on the side of the machine. Finally you make a small incision at the puncture wound that allows you to spread the tissues with a small hemostat. You gently perform a blunt dissection towards the tip of your finder needle and voila, you find the buried base of the splinter. You are able to grasp it with the hemostat and carefully pull it out in one piece. You remove the splinter and the finder needle, confirm with the ultrasound that there is no residual splinter, and place a sterile bacitracin dressing. Mission complete!

Your patient is so impressed with your gadgets and your work that he asks you if you could also remove a bullet that he’s had next to one of his ribs from an injury 5 years ago. You answer, “I don’t know about that, but I can take a look with this”

 

See the next page for clinical pearls and pitfalls for ultrasound imaging of foreign bodies.

 

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Pearls and Pitfalls for ultrasound of foreign bodies in soft tissue 

 

Know your limitations: Ultrasound may help clarify findings elicited by history and physical exam. When used correctly, it can greatly improve diagnostic accuracy, and help guide patient management, especially for time-critical diagnosis and treatment in unstable patients. There is no substitute for hands-on practice to improve your skills, but if you use ultrasound in your ED, your department should also have a quality improvement program set up that is approved by both ED administration and radiology.

Use a high frequency probe: Soft tissue applications, where the structures of interest are generally close to the skin surface, should be performed with a high frequency linear array transducer (E.g. a 5 to 7.5 MHz linear array transducer)

Use enough gel. Apply sufficient ultrasound gel to optimize your acoustic interface. The only real down side of extra gel is extra clean-up.

Consider a stand-off pad: If the patient is thin with little subcutaneous fat, you may need to utilize an acoustic standoff pad to improve your sonographic window. If acoustic standoff pads are not available, an acoustic window can be easily created with a small bag of normal saline or a fluid filled glove sandwiched between two layers of ultrasound gel.

Check multiple views: Always obtain images in multiple planes (longitudinal, transverse, oblique) to help define the borders of the structure of interest. Prior to the procedure, attempt to identify surrounding nerves and vessels to help prevent accidental injury.

Use the unaffected side for comparison: Utilize contra-lateral limbs and adjacent areas of normal appearing tissue for comparison.

Wood-Glass-Plastic-Metal: Wood tends to be very hyperechoic (white). Glass is more difficult to see than wood and plastic is a bit more challenging than glass. Metal objects can be very difficult to visualize with ultrasound. Look for ring-down artifact farfield to the metal object and consider X-ray or fluoroscopy if indicated.

Use artifacts to help you: Look for acoustic shadowing or bright comet tails to help you find foreign bodies.

Finder needle: A “finder needle” may be inserted under ultrasound guidance and then left in place until the procedure is finished. A larger needle or one with a plastic sheath (angiocath) may make visualization by ultrasound easier. Use a short needle without a syringe to minimize torque forces due to gravity.

Real-time guidance: Ultrasound guided foreign body removal can be performed in a static or dynamic manner. If the procedure is performed in “real-time”, remember to use sterile ultrasound gel and prep the ultrasound probe in a sterile fashion. Blunt tissue dissection should be performed using a sterile hemostat or a pair of fine forceps that you can attempt to follow and “guide” using you ultrasound machine.

 

Brady Pregerson, MD, oversees QI for ED Ultrasound at Cedars-Sinai Medical Center in Los Angeles. For more images, check out Real-Time Readings at www.epmonthly.com.
Teresa Wu, MD, a clinical assistant professor in EM at Florida State University, completed her ultrasound fellowship at Stanford University Medical Center.