Interosseous
A vascular access technique that delivers fluids and medications directly into the bone marrow when intravenous access cannot be obtained, providing a fast and reliable route during shock or cardiac arrest.
In the Field
Intraosseous access is what tactical paramedics reach for when the patient is too cold, too shocked, or too poorly veined for an IV. The bone marrow does not collapse the way veins do in shock, so an IO works when an IV will not. Modern devices have made the procedure fast and reliable in the field. For aid bag specifications, IO capability is one of the items that distinguishes a tactical paramedic kit from a basic provider kit. The training, the device, and the protocol authority all have to be in place for an IO program to make sense.
Common Mistake
Treating IO as a last resort instead of recognizing it as a first-line option in shocked or hemodynamically compromised patients where IV access will be slow or unsuccessful.
Technical Detail
Interosseous (IO) access is a vascular access technique that delivers fluids and medications directly into the bone marrow cavity, where the marrow's vascular network rapidly distributes the infusion into the central circulation. IO access is functionally equivalent to a central venous catheter for most resuscitation purposes, with onset of medication effect comparable to peripheral IV administration.
Why IO matters in trauma. Peripheral IV access is the standard route for fluid and medication delivery, but in trauma patients several factors can make IV access difficult or impossible:
Shock and hypovolemia. As blood volume drops, peripheral veins collapse and become difficult to cannulate.
Hypothermia. Cold patients have constricted peripheral vessels.
Burns or trauma to the extremities. Damaged or covered limbs may not have accessible veins.
IV drug use history. Patients with chronic IV drug use frequently have scarred or thrombosed peripheral veins.
Body habitus. Obesity, edema, or anatomic variation can make veins difficult to locate.
In any of these scenarios, attempting peripheral IV access can consume critical time without producing a usable line. IO access bypasses these limitations because the bone marrow vascular network does not collapse in shock and does not depend on visible peripheral veins.
Anatomic sites. Several IO insertion sites are commonly used:
Proximal tibia. The most commonly used site for adult and pediatric patients. Located approximately two finger-widths below the kneecap on the flat medial surface of the tibia.
Proximal humerus. An alternative adult site, located on the surgical neck of the humerus. Often preferred when leg access is not feasible.
Distal tibia. Used as an alternative site, particularly in adults.
Sternum. Used with specialized sternal IO devices, primarily in military settings.
Devices. Modern IO access uses specialized insertion devices rather than manual needles. Common devices include:
EZ-IO (Teleflex). A battery-powered drill with proprietary needles. Most widely used in civilian and military prehospital care.
T.A.L.O.N. and similar manual devices. Used primarily in military and austere settings.
FAST1 (Pyng Medical). A sternal-specific device used in military forward care.
The shift to powered insertion devices in the 2000s dramatically improved the reliability and speed of IO access, making it a practical first- or second-line option rather than a procedure of last resort.
What can be administered. Essentially any medication or fluid that can be given IV can be given IO, including:
Crystalloid and blood products.
Resuscitation medications (epinephrine, atropine, calcium, sodium bicarbonate).
Pain management medications.
Antibiotics.
TXA.
Sedation and anesthesia agents.
Provider scope. IO access is a provider-level skill. Within civilian EMS, IO is typically authorized for paramedics and at provider levels above. State EMS scope of practice rules and individual service medical director protocols govern when and where IO can be performed. Within tactical contexts, IO is a standard skill for tactical paramedics, SWAT medics, and military combat medics.
Aid bag specifications. IO devices and consumables are standard contents of advanced tactical aid bags including:
Tactical paramedic and SWAT medic kits.
Air medical and ground critical care transport kits.
Forward-deployed military medical kits.
The drive-style devices (EZ-IO and similar) require the device itself plus needles in adult and pediatric sizes. Storage and inspection cycles apply to maintain device readiness.
Procurement implications. Adding IO capability to an agency's tactical medical program requires:
The device and its consumables.
Provider training, often delivered by the device manufacturer or through tactical paramedic education programs.
Service medical director protocol authorizing IO use within scope of practice.
Documentation and continuous quality improvement processes.
For agencies updating tactical medical specifications, IO capability is one of the markers that distinguishes a basic responder kit from a provider-level resuscitation kit. The cost of the device and consumables is modest; the training and protocol work is the larger investment.
Why IO matters in trauma. Peripheral IV access is the standard route for fluid and medication delivery, but in trauma patients several factors can make IV access difficult or impossible:
Shock and hypovolemia. As blood volume drops, peripheral veins collapse and become difficult to cannulate.
Hypothermia. Cold patients have constricted peripheral vessels.
Burns or trauma to the extremities. Damaged or covered limbs may not have accessible veins.
IV drug use history. Patients with chronic IV drug use frequently have scarred or thrombosed peripheral veins.
Body habitus. Obesity, edema, or anatomic variation can make veins difficult to locate.
In any of these scenarios, attempting peripheral IV access can consume critical time without producing a usable line. IO access bypasses these limitations because the bone marrow vascular network does not collapse in shock and does not depend on visible peripheral veins.
Anatomic sites. Several IO insertion sites are commonly used:
Proximal tibia. The most commonly used site for adult and pediatric patients. Located approximately two finger-widths below the kneecap on the flat medial surface of the tibia.
Proximal humerus. An alternative adult site, located on the surgical neck of the humerus. Often preferred when leg access is not feasible.
Distal tibia. Used as an alternative site, particularly in adults.
Sternum. Used with specialized sternal IO devices, primarily in military settings.
Devices. Modern IO access uses specialized insertion devices rather than manual needles. Common devices include:
EZ-IO (Teleflex). A battery-powered drill with proprietary needles. Most widely used in civilian and military prehospital care.
T.A.L.O.N. and similar manual devices. Used primarily in military and austere settings.
FAST1 (Pyng Medical). A sternal-specific device used in military forward care.
The shift to powered insertion devices in the 2000s dramatically improved the reliability and speed of IO access, making it a practical first- or second-line option rather than a procedure of last resort.
What can be administered. Essentially any medication or fluid that can be given IV can be given IO, including:
Crystalloid and blood products.
Resuscitation medications (epinephrine, atropine, calcium, sodium bicarbonate).
Pain management medications.
Antibiotics.
TXA.
Sedation and anesthesia agents.
Provider scope. IO access is a provider-level skill. Within civilian EMS, IO is typically authorized for paramedics and at provider levels above. State EMS scope of practice rules and individual service medical director protocols govern when and where IO can be performed. Within tactical contexts, IO is a standard skill for tactical paramedics, SWAT medics, and military combat medics.
Aid bag specifications. IO devices and consumables are standard contents of advanced tactical aid bags including:
Tactical paramedic and SWAT medic kits.
Air medical and ground critical care transport kits.
Forward-deployed military medical kits.
The drive-style devices (EZ-IO and similar) require the device itself plus needles in adult and pediatric sizes. Storage and inspection cycles apply to maintain device readiness.
Procurement implications. Adding IO capability to an agency's tactical medical program requires:
The device and its consumables.
Provider training, often delivered by the device manufacturer or through tactical paramedic education programs.
Service medical director protocol authorizing IO use within scope of practice.
Documentation and continuous quality improvement processes.
For agencies updating tactical medical specifications, IO capability is one of the markers that distinguishes a basic responder kit from a provider-level resuscitation kit. The cost of the device and consumables is modest; the training and protocol work is the larger investment.