骨髄針の配置
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Q1: When should intraosseous needle placement be used instead of peripheral IV access?
IO needle placement is preferred when peripheral IV cannulation is technically challenging or has failed. This includes small children, injection drug users, obese patients, those with chronic illnesses requiring frequent access, patients with burns or skin conditions, and patients in shock where blood is shunted away from peripheral vessels. IO access provides rapid, effective vascular access for unstable patients needing urgent medication, fluid, or blood product administration.
Q2: What are the three main anatomical sites for intraosseous needle insertion?
The three primary IO insertion sites are the proximal tibia on the medial flat side, three centimeters distal to the inferior border of the patella; the distal tibia on the medial flat side, three centimeters proximal to the medial malleolus; and the proximal humerus on the greater tubercle, one to two centimeters proximal to the surgical neck. The proximal humerus is preferred in patients with abdominal, pelvic, or lower extremity trauma.
Q3: What contraindications prevent using a specific IO insertion site?
Contraindications to IO placement at a chosen site include acute or recent fracture of the target bone, previous significant orthopedic procedure at that location, overlying skin or soft tissue infection, inability to palpate anatomic landmarks, and previous IO needle placement at the site within the past 48 hours. These factors must be assessed before site selection to ensure safe needle placement.
Q4: How do you know when the IO needle has entered the medullary space?
When drilling, you will feel the needle suddenly give way as the high resistance of the mineralized cortex changes to the much lower resistance of soft marrow. This tactile sensation indicates the needle has penetrated the bone cortex and entered the medullary space. In young children with cartilaginous bones, this sensation is less prominent, requiring careful attention to drilling resistance.
Q5: What is the correct final needle depth for intraosseous placement?
The goal is to achieve a total needle depth of one to two centimeters, with the tip seated in the medullary space. This depth usually results in the hub ending up next to the skin if the proper needle size has been selected. Avoid pushing the hub flush against the skin, as this may result in excessively deep insertion and potential complications.
Q6: How do you verify that an IO needle is properly positioned and functional?
Verify IO needle position by aspirating to check for pink marrow reflux into the tubing, though this is not always present. Confirm functionality by flushing with a five to ten milliliter syringe; you should encounter minimal resistance and see no fluid leakage around the insertion site or skin puffiness. Once verified, the needle is ready for infusion of fluids, blood products, bolus medications, and continuous infusions.
Q7: What needle sizes are used for different patient populations in IO placement?
Needle selection depends on patient size: 15 millimeters for infants and small children, 25 millimeters for larger children and adults, and 45 millimeters for unusually large adults. All needles have black markings every five millimeters from tip to shaft top. The first five millimeter mark must be visible above the skin surface after initial positioning to ensure adequate length to reach the medullary space.