Intraosseous access — formative SAQs

SAQ 1 — Decision and proximal tibial insertion (15 marks, 15 minutes)

A two-year-old is brought to the emergency department cold, mottled, and barely rousable with presumed septic shock. Heart rate 180, capillary refill 6 seconds, blood pressure 60/35. Two peripheral cannulation attempts over the last 75 seconds have failed. ^{[1] [3]}

Question. Outline your immediate vascular access decision, describe the proximal tibial intraosseous insertion step by step (including the landmark and the weight-based needle), and state how you would confirm correct placement. Explain your reasoning.

Model answer

Decision (3 marks). State the rule aloud and act on it: intravenous access that cannot be secured within 60 to 90 seconds in a child with shock, arrest, or peri-arrest mandates an intraosseous needle now — not a third cannulation attempt. Name the operator and run the clock. Central lines and cut-downs take too long in an unstable child. ^{[1] [3]}

Site and needle (3 marks). First-line site is the proximal tibia: the flat anteromedial surface, one to two centimetres below and one to two centimetres medial to the tibial tuberosity. This keeps the track medial to and below the growth plate and reaches the vascular metaphysis. Choose an EZ-IO 15 millimetre pink needle set (for 3 to 39 kilograms); a 25 millimetre blue set is for 40 kilograms and over. ^{[1] [9]}

Technique (4 marks). Clean the skin, don sterile gloves, and palpate the landmark. Hold the drill perpendicular to the skin and drill with gentle pressure until a distinct give is felt as the cortex breaches; stop at once, remove the stylet, and attach the extension set. Angle perpendicular, never toward the ankle, to avoid the growth plate and a shallow position. Do not re-drive a placed needle. ^[1]

Confirmation (3 marks). The needle stands firm and upright like a tent peg. Aspirate marrow if possible (and send it for blood gas, glucose, group and hold, and culture), but recognise that failure to aspirate does not exclude a good line. Flush with saline: it should run easily with no calf swelling, and the distal limb should remain soft, warm, and well perfused. ^{[1] [12]}

Reasoning and next step (2 marks). The marrow venous sinusoids sit inside a rigid cortex and do not collapse in shock, so drugs and fluids reach the heart in seconds at intravenous doses. Give adrenaline at the intravenous dose, push crystalloid with a pressure bag (gravity flow is too slow), and obtain definitive access as the child stabilises, removing the IO within 24 hours. ^[1]