Intraosseous access — branching viva

Branching viva — intraosseous access

The examiner releases the stem and then branches into four probes. A strong candidate answers the decision first, defends the physiology, demonstrates the technique, and names the complications without prompting. ^{[1] [3]}

Opening (examiner)

"A two-year-old arrives cold, mottled, and barely rousable with septic shock. Heart rate 180, capillary refill 6 seconds, blood pressure 60/35. Two peripheral cannulation attempts over 75 seconds have failed. What is your next move?" ^[1]

Branch 1 — The decision (expected answer)

State the rule and act on it: if intravenous access cannot be secured within 60 to 90 seconds in a child with shock, arrest, status epilepticus, or peri-arrest, place an intraosseous needle now rather than attempting a third cannula. Name the operator, state the decision aloud, and run the clock. Central lines and cut-downs take too long in an unstable child. ^{[1] [3]}

Probe. "Why IO and not a central line?" — A central line takes many minutes and interrupts resuscitation; an IO is placed in under a minute, does not interrupt compressions, and delivers drugs to the heart in seconds at intravenous doses. ^{[1] [2]}

Branch 2 — Physiology (expected answer)

The medullary cavity holds thin-walled venous sinusoids held open by the rigid cortex, so they do not collapse in shock when peripheral veins have shut down. Fluid and drugs drain through the central venous canal and the nutrient vein into the systemic circulation and reach the heart in seconds, with pharmacokinetics close to a central line. Every drug that can be given intravenously can be given intraosseously at the same dose. ^{[9] [12]}