Medicine
Intraosseous Access for Emergency Vascular Access
Quick fact
An intraosseous line can be placed in under 90 seconds, and medications infused through the bone marrow reach the central circulation nearly as quickly as those given through a peripheral IV.
Why this is interesting
When seconds count and veins collapse, where do you turn? The answer may be inside the bone itself.
Read the full explanation
Understanding Intraosseous Access for Emergency Vascular Access
Think of the bone marrow as a rigid, protected network of blood vessels. In children and adults, the marrow within long bones (like the tibia) is densely packed with a venous plexus—an extensive network of small veins. By inserting a specialized needle through the hard outer bone (cortex) into this marrow cavity, we gain direct access to the systemic venous system. This works even when peripheral veins are collapsed due to shock, dehydration, or cardiac arrest. The procedure involves locating a landmark (commonly the proximal tibia, just below the knee), cleansing the site, and, using a twisting or drilling motion, placing a needle into the marrow cavity. Once the needle is correctly positioned, aspiration of bone marrow into a syringe confirms placement, and a standard IV extension set can be attached to infuse fluids and drugs.
A deeper explanation
The key reason IO access works is that the bone marrow is not isolated; it drains directly into the venous sinuses and then into larger veins, which empty into the central circulation. This makes the marrow cavity a functional venous reservoir. The physiology of the bone marrow blood supply means that anything injected into the marrow is rapidly transported to the heart. This is why IO access is so vital in emergencies: when peripheral veins are inaccessible, the bone marrow remains a reliable point of entry. It also matters in trauma and cardiac arrest because time is critical; IO placement can be achieved more quickly than central venous catheterization, and it avoids the risks of pneumothorax or arterial puncture associated with central lines. Once the patient is stabilized, the IO line is removed and replaced with a more conventional IV, but during the initial critical minutes, it saves lives.