IO Intraosseous Infusion Explained (as seen on The Pitt)
- Bryan Knowles
- Mar 28
- 6 min read
Those of you watching The Pitt on HBO/MAX have seen prominently featured something called an "IO" where the physicians appear to use a drill on the patients during a mass casualty event. While appearing disturbing, this is a way of establishing access for the provision of blood where it may be too time-consuming or difficult to place an IV (which stands for "intravenous" rather than "intraosseous").
Etymology: Intra (within) Os (bone)
Intraosseous Lines in Trauma Care
Intraosseous (IO) access is a life-saving technique used in emergency and trauma situations where intravenous (IV) access is difficult or impossible to establish rapidly. This method involves inserting a needle directly into the bone marrow cavity, most commonly in long bones such as the tibia, humerus, or femur. The marrow cavity is a non-collapsible venous network, allowing for the rapid administration of fluids, medications, and even blood products in critically ill or injured patients.
The use of intraosseous lines has become increasingly common in both pre-hospital and hospital trauma settings due to advancements in insertion devices, growing evidence of efficacy, and changes in clinical guidelines. This method has proven particularly valuable in patients experiencing hypovolemic shock, cardiac arrest, severe burns, or major trauma—conditions in which peripheral veins may be collapsed and challenging to cannulate.
Here is a video of how to do it: Intraosseous needle insertion - EZ-IO 'drill' system
Physiological Basis of Intraosseous Access
The bone marrow cavity is highly vascular and interconnected with the central circulation through venous sinusoids that drain into the central venous system. Fluids and medications administered through an intraosseous needle enter the marrow's vascular network and are quickly absorbed into the systemic circulation. This rapid uptake ensures therapeutic efficacy comparable to that of intravenous administration, particularly when time is critical.
In trauma scenarios where circulatory collapse is imminent or already occurring, traditional IV access can be delayed or impossible due to vasoconstriction and vein collapse. In such circumstances, IO access provides a reliable and fast alternative, with high first-attempt success rates and minimal time required for placement. For these reasons, IO lines have gained prominence as a front-line option for vascular access in trauma protocols.
Use of Intraosseous Lines for Blood Transfusion
Traditionally, intraosseous access has been used primarily for the administration of fluids, medications, and blood products in pediatric resuscitation, but it is now increasingly employed in adults as well. Blood transfusion through an IO line is not only feasible but has been supported by clinical and experimental data. Red blood cells, plasma, and platelets can be transfused via intraosseous access with flow rates and bioavailability similar to peripheral IV lines, particularly when using pressure infusion (squeezing those bags).
Several studies have demonstrated the compatibility of IO lines with packed red blood cells. The marrow cavity can tolerate the osmolarity and viscosity of blood products without adverse effects, and flow can be enhanced through pressure bags or infusion pumps. In situations where peripheral and central venous access is unobtainable or delayed, IO transfusion can make the difference between life and death, particularly in massive hemorrhage or shock.
It is important to note, however, that while IO lines can support blood transfusion, the site selection, needle gauge, and proper placement are essential to ensuring optimal flow and preventing complications. The humeral site, for example, is often preferred for blood transfusion due to its proximity to the central circulation and its relatively large marrow cavity, which can accommodate higher flow rates.
Advantages of Intraosseous Lines in Trauma Settings
The primary advantage of intraosseous access in trauma is the speed and reliability of insertion. In emergency scenarios where IV access is difficult, the ability to establish IO access within seconds to a minute significantly improves the resuscitation process. The ease of insertion, especially with modern battery-powered or spring-loaded devices, allows even less experienced clinicians to achieve successful placement with minimal training.
Another critical advantage is the consistency of access in severely hypovolemic patients.
During shock, peripheral veins collapse, and the time required for traditional IV placement increases substantially. IO access circumvents this issue by accessing a non-collapsible marrow cavity, ensuring vascular access regardless of peripheral vasoconstriction.
Furthermore, IO lines can be used for all types of fluid and medication administration, including vasopressors, antibiotics, and anesthetics, in addition to blood products. This versatility makes IO access particularly valuable in mass casualty situations, pediatric trauma, and prehospital care where time and resources are limited.
Steps For Placing an IO Access
Once the patient is prepared, identify the designated site with a sterile gloved finger.
Disinfect overlying skin, and provide local anesthetic as desired.
Be sure the stylet is in place on the needle prior to insertion.
Have a 20 ml Saline syringe flush, IV tubing, tape, medications, fluids, and pump prepared, as required.
Place the needle through the skin, perpendicular and down to the bone.
Activate the IO drill or gun until the IO needle anchors in place, OR manually TWIST the needle clockwise (don’t push) with gentle firm pressure until the bone gives (loss of resistance technique) and the needle locks into place.
The bone give is an indication the needle has passed through cortical bone into the marrow.
If properly positioned, the needle will stand without support and be fixed in place.
• Remove the stylet and attach the syringe and aspirate, marrow and blood confirms placement but may not always appear.
Gently flush saline through the needle and watch the insertion site for swelling.
If the test injection is unsuccessful or swelling is seen on the opposite side of the bone, repeat the above procedure with a new IO needle on another bone.
If successful, stabilize the needle with the tape; gauze padding may be used as desired.
Attach the IV tubing to the needle hub and infuse fluids, blood products, or medications.
IO access is contraindicated in certain conditions such as fractures at or near the intended insertion site, previous orthopedic procedures at the site (e.g., joint replacement), or known bone pathology such as osteogenesis imperfecta. These limitations necessitate careful patient assessment before placement.
Comparison with Intravenous Lines for Blood Transfusion
Intravenous access remains the gold standard for vascular access and blood transfusion in trauma care. Peripheral IV lines, especially large-bore catheters (14- to 18-gauge), allow for rapid infusion of large volumes of fluids and blood products. Central venous catheters, though more time-consuming to place, provide even more secure and high-flow access, suitable for prolonged resuscitation and administration of vasopressors or irritant drugs.
In comparison, IO lines offer several distinct advantages and disadvantages. The key benefit of IO access lies in its speed and reliability, particularly when IV access fails. In many cases, IO access can be established within 30 to 60 seconds, whereas multiple IV attempts may take several minutes, which can be critical in trauma resuscitation. However, IO lines are generally considered a temporary solution, intended to provide immediate access until definitive IV or central venous access can be obtained.
Flow rate is another differentiating factor. While IV lines—especially large-bore—facilitate high flow rates suitable for massive transfusion, IO lines have more limited flow without the aid of pressure infusion devices. Even then, the maximum flow achievable via IO access typically falls short of what can be delivered through dual large-bore IVs or a central line with rapid infuser systems.
The duration of use also distinguishes the two methods. IO lines are generally recommended for short-term use (ideally less than 24 hours), due to the risk of infection and other complications. IV lines, particularly central lines, can be maintained for longer periods under sterile conditions and can accommodate ongoing resuscitative and supportive care.
Another point of comparison lies in patient comfort and ease of management. IO insertion, although rapid, can be painful due to the pressure within the marrow cavity during infusion, necessitating administration of local anesthetic if the patient is conscious. IV lines, while not always comfortable, are less painful to maintain and typically more acceptable to patients for prolonged use.
Conclusion
Intraosseous access represents a critical advancement in trauma and emergency medicine, offering a rapid and reliable alternative to intravenous access when time is of the essence. Its utility in blood transfusion has been well established, particularly in cases where conventional IV access is delayed or impossible due to circulatory collapse. Though IO lines are not without limitations—such as reduced flow rates, risk of complications, and short-term usability—they remain an essential tool in the trauma clinician’s arsenal.
Comparatively, intravenous access continues to be the preferred method for administering blood products due to its capacity for high-volume infusion and long-term use. Nonetheless, intraosseous access provides a vital bridge in resuscitation, enabling the rapid initiation of life-saving therapy, including blood transfusion, in the most critical moments of trauma care. As technology and training improve, the role of IO lines will likely continue to expand, reinforcing their place alongside IV lines in comprehensive trauma management.