Intraosseous (IO) access, commonly called “bone infusion,” is a technique used in emergency medicine to rapidly deliver fluids and medications directly into the body’s circulatory system. This method involves inserting a specialized needle into the highly vascularized bone marrow cavity, which connects to the central circulation. The bone marrow space acts as a non-collapsible vein, allowing for the quick absorption of therapeutic agents when standard intravenous (IV) access is difficult or impossible. IO access provides a reliable, temporary pathway into the systemic circulation during time-sensitive medical crises.
Why Intraosseous Access is Necessary
Intraosseous access becomes the preferred alternative when peripheral IV access cannot be established quickly or is physically unobtainable during a life-threatening emergency. Current resuscitation guidelines recommend using the IO route if IV access is delayed or fails, often suggesting it after two failed attempts or when access cannot be secured within a critical timeframe, such as 60 to 90 seconds.
The necessity of IO access is highlighted in specific medical scenarios where a patient’s veins are compromised or difficult to locate. These situations include cardiac arrest, severe shock from trauma or illness, and cases of profound circulatory collapse. In patients experiencing severe burns or massive edema, the peripheral veins may be inaccessible. Because the bone’s vascular channels remain patent even when a patient is in shock, IO access ensures a reliable port for resuscitation efforts.
The Mechanics of Insertion
The IO procedure involves inserting a specialized needle through the hard outer layer of the bone, the cortex, and into the inner medullary cavity where the bone marrow resides. Trained medical professionals use specific anatomical sites for insertion, most commonly the proximal humerus (upper arm bone) and the proximal or distal tibia (shin bone). The humerus is often preferred in adults for its high flow rate capabilities, while the tibia is a common site across all age groups.
Insertion is often performed using specialized, powered devices that drive the rigid needle into the bone with precision and speed. After the needle penetrates the cortex, a distinct sensation, sometimes described as a “pop” or “give,” is felt as the tip enters the marrow cavity. Once the needle is placed, the inner stylet is removed, and the catheter is immediately secured and flushed. Placement is confirmed by the needle’s stability, the ability to aspirate bone marrow, or the smooth, uninhibited flow of a flush solution without swelling around the site.
Substances Delivered Through the Bone
The IO route allows for the administration of virtually any medication or fluid that can be given intravenously. This includes large-volume fluid resuscitation with crystalloid solutions, blood products, and most drugs necessary for advanced life support. The absorption rate of substances delivered through the bone marrow is comparable to standard IV administration, making it an effective alternative for rapid treatment.
The bone marrow cavity functions like a network of venous sinuses that drain directly into the systemic circulation. This efficient pathway allows emergency medications, such as epinephrine and atropine, to reach the central circulation quickly and in therapeutic concentrations. To achieve the necessary flow rates for rapid fluid delivery, especially during resuscitation, the fluids must often be administered using a pressure bag or infusion pump.
Safety and Removal Procedures
Intraosseous access is considered a safe procedure when performed by trained personnel, though complications are possible and must be monitored closely. Potential complications include osteomyelitis (bone infection) and compartment syndrome, which is tissue pressure buildup from fluid leakage. The risk of infection is notably higher if the IO catheter remains in place longer than 24 hours.
Because IO access is temporary, it must be removed as soon as standard IV access is successfully established or within 24 hours of placement. For conscious patients, local anesthesia is typically administered before the procedure to manage pain associated with the insertion and the subsequent infusion. Removal involves stabilizing the bone and pulling the needle straight out with a continuous, gentle rotating motion. After removal, the site is dressed, and the limb is continuously monitored for any signs of complication.