Intraosseous Access: Indications, Insertion Sites, and Technique

Intraosseous (IO) access is one of the most important fallback strategies in emergency medicine – and at the same time one of the most frequently underutilized. When peripheral intravenous access cannot be established within 60 to 90 seconds in a critically ill patient, IO access is not a last resort but the guideline-recommended next step. The AHA guidelines classify IO access as equivalent to intravenous access – both for drug administration and volume resuscitation during cardiac arrest. Yet in practice, many colleagues train IO access too infrequently and hesitate when it matters most. This article provides you with a systematic overview of indications, contraindications, insertion sites in adults and children, available systems, correct technique, and the specifics of drug administration via the intraosseous route.

Physiological Basis: Why Does IO Access Work?

Bone marrow contains a dense network of non-collapsible venous sinusoids that communicate directly with the central venous system. Even in severe hypovolemia or vasoconstriction – situations in which peripheral veins collapse – this intramedullary vascular plexus remains perfused and accessible. Drugs and fluids injected into the medullary cavity reach the central circulation within seconds. Pharmacokinetic studies demonstrate comparable onset times and plasma levels to those achieved with peripheral intravenous administration.

The key point: The medullary cavity functions like a non-collapsible vein. This makes IO access reliable precisely in those situations where peripheral access is most difficult to obtain.

Indications

The core indication is clearly defined: IO access is indicated when intravenous access cannot be established in a timely manner and urgent drug or volume administration is required.

Specifically, this means:

• Cardiac arrest (CPR): After a maximum of two failed peripheral venous puncture attempts or after 60–90 seconds without successful IV access
• Severe shock (hemorrhagic, septic, anaphylactic) with non-accessible veins
• Severe burns with extensive skin damage making peripheral venous access impossible
• Status epilepticus when no IV access is available and intranasal/rectal administration is insufficient
• Pediatric emergencies: In children – especially infants and toddlers – IO access is often faster and more reliable than repeated IV attempts
• Hypothermia with peripheral vasoconstriction
• Entrapped patients with limited access to extremities

A key clinical decision point: You should not view IO access as a last resort but plan for it early in your access strategy. During cardiac arrest in particular, every minute without vascular access costs valuable time for epinephrine administration.

Contraindications

Contraindications are mostly site-specific rather than procedure-specific. If one extremity is contraindicated, choose an alternative insertion site.

Absolute Contraindications (for the respective extremity)

• Fracture of the target bone – drugs and fluids leak through the fracture gap into soft tissue
• Previous IO puncture of the same bone within the last 24–48 hours (perforated cortex leads to extravasation)
• Vascular injury proximal to the insertion site – drainage into the central circulation is not ensured
• Local infection or burn at the insertion site

Relative Contraindications

• Severe osteoporosis or osteogenesis imperfecta (increased fracture risk, but not an absolute contraindication)
• Previous orthopedic surgery on the target bone (prosthesis, internal fixation)
• Known bone tumors at the insertion site

Important: In a resuscitation scenario, the benefit almost always outweighs the risk. An absolute contraindication at one site means: choose another site, not "no IO access."

Insertion Sites in Adults and Children

The choice of insertion site depends on the clinical situation, the patient's age, and the available systems.

Proximal Tibia (Standard Location)

The proximal tibia is the most commonly used insertion site in both adults and children and the recommended first-choice location.

• Landmark in adults: Approximately 2 cm medial and 1–2 cm distal to the tibial tuberosity on the flat medial tibial surface
• Landmark in children: Approximately 1–2 cm distal and medial to the tibial tuberosity (in infants, one finger breadth below the tuberosity is sufficient)
• Advantages: Large, flat bone surface, easily palpable landmarks, relatively easy to identify even in obese patients, minimal soft tissue

Distal Tibia (Medial Malleolus)

• Landmark: 1–2 cm proximal to the highest point of the medial malleolus on the flat tibial surface
• Advantages: Very little soft tissue, easily palpable
• Suitability: Alternative site when the proximal tibia is not available; well suited for children aged approximately 6 years and older

Proximal Humerus

• Landmark: The arm is adducted and slightly internally rotated (hand on the umbilicus). The insertion site is at the greater tubercle – identified by palpating the acromion and puncturing approximately 1–2 cm distal to it on the anterolateral surface of the humeral head
• Advantages: Very large medullary cavity in adults, high flow rates achievable (up to 5 liters/hour under pressure infusion), shortest distance to the central circulation
• Disadvantages: Somewhat more challenging landmarks, less commonly used in children
• Suitability: Preferred site in adults when high flow rates are needed (e.g., volume resuscitation in shock)

Distal Femur (Pediatric)

• Landmark: Approximately 1–2 cm proximal to the superior border of the patella on the anteromedial femoral surface, with the knee extended
• Advantages: Large medullary cavity in children
• Suitability: Primarily in infants and toddlers as an alternative to the proximal tibia

Sternum

• Landmark: Manubrium sterni, approximately 1 cm below the jugular notch
• Limitation: Exclusively with the designated FAST1 system (in adults); contraindicated in children due to thin cortex and risk of pericardial injury
• Suitability: Rarely used in current practice, as the humerus and tibia offer more reliable alternatives

Available Systems

Three systems dominate the market and are used in prehospital and in-hospital emergency medicine:

EZ-IO (Arrow/Teleflex)

• Principle: Battery-powered drill with single-use needle sets
• Needle sizes: 15 mm (pink, 3–39 kg), 25 mm (blue, ≥ 40 kg), 45 mm (yellow, for obese patients or humeral insertion)
• Advantages: Rapid application (typically < 10 seconds insertion time), easy handling, very high success rate (> 90% on first attempt), most widely used
• Insertion sites: All of the above except the sternum

BIG (Bone Injection Gun)

• Principle: Spring-loaded mechanism
• Variants: Adult (red) and pediatric (blue)
• Advantages: Compact, no power source required
• Disadvantages: Single-use device, penetration depth must be preset, slightly less controlled insertion compared to the EZ-IO

FAST1/FASTx (Sternum)

• Principle: Specifically designed for sternal puncture
• Suitability: Adults only, sternum only
• Relevance: Declining use in current practice

For most clinical scenarios, the EZ-IO system is the standard. Correct needle size selection is critical – a needle that is too short will seat the tip in the cortex rather than the medullary cavity, while a needle that is too long carries the risk of penetrating through the far cortex.

Technique: Step by Step

Using the example of the proximal tibia with the EZ-IO system:

1. Confirm the indication: No IV access achievable within 60–90 seconds, urgent drug/volume administration required
2. Rule out contraindications: No fracture, no infection, no previous IO in the same bone
3. Identify and mark the landmark: Palpate the tibial tuberosity, mark the insertion point 2 cm medial and 1–2 cm distal
4. Skin disinfection (if the situation allows – do not delay during cardiac arrest)
5. Select the needle: Blue needle (25 mm) for normal-weight adults, yellow needle (45 mm) for obese patients or humeral insertion, pink needle (15 mm) for children under 40 kg
6. Attach the needle to the drill and remove the safety cap
7. Insertion: Place the needle perpendicular to the bone surface (90° for the tibia), apply gentle pressure, and activate the drill. Do not push forcefully – let the drill do the work. A distinct loss of resistance ("give") signals penetration through the cortex into the medullary cavity
8. Remove the drill, unscrew and discard the stylet (trocar)
9. Attempt aspiration: Bone marrow (dark red, viscous aspirate) confirms correct placement. Note: Negative aspiration does not rule out correct placement – the aspiration success rate is approximately 60–80%
10. Connect the extension set (EZ-Connect)
11. Flush with 10 ml of 0.9% NaCl (in conscious patients, first slowly administer 20–40 mg of 2% lidocaine via the IO needle – see below)
12. Confirm placement: Flush proceeds without increased resistance, no swelling in the surrounding soft tissue, needle is firmly seated in the bone
13. Secure: EZ-Stabilizer or adhesive dressing, do not move the extremity

Drug Administration via IO Access

What Can Be Administered via IO?

The key message: All drugs and fluids that can be given intravenously can also be administered intraosseously. This includes:

• Catecholamines: Epinephrine 1 mg every 3–5 minutes during cardiac arrest, norepinephrine, dobutamine
• Amiodarone: 300 mg bolus for refractory ventricular fibrillation
• Sedatives and analgesics: Midazolam, ketamine, fentanyl, morphine
• Neuromuscular blocking agents: Rocuronium, succinylcholine (for RSI)
• Volume: Crystalloids, colloids, blood products (packed red blood cells, fresh frozen plasma)
• Glucose: 10% or 20% for hypoglycemia
• Sodium bicarbonate, calcium chloride, magnesium sulfate
• Antibiotics in septic shock
• Contrast media for CT scans (can be administered via IO, though image quality may be reduced)

Dosing

Doses are identical to intravenous administration. Each drug administration should be followed by a flush of 5–10 ml of 0.9% NaCl to propel the drug from the medullary cavity into the central circulation.

Flow Rates

• Gravity infusion: approximately 80–100 ml/h (limited by medullary cavity resistance)
• Pressure bag (300 mmHg): Up to 1 liter in 10–15 minutes at the tibia, even faster at the humerus
• For clinically significant volume resuscitation, a pressure bag is virtually always required

Pain Management in Conscious Patients

The IO insertion itself is minimally painful, as the cortex contains no pain receptors. The infusion, however, causes significant pain due to the rise in intramedullary pressure. For conscious patients, therefore:

• Before flushing: Slowly administer 20–40 mg of 2% lidocaine (0.5 mg/kg) via the IO needle
• Allow 60 seconds for the lidocaine to take effect
• Then slowly flush with 0.9% NaCl
• Repeat lidocaine if needed (observe the maximum total dose: 4.5 mg/kg without epinephrine additive)

This point is frequently overlooked in practice – IO infusion without lidocaine in conscious patients is extremely painful and leads to patient resistance and complications.

Complications

IO access is a safe procedure with a complication rate below 1%. Possible complications include:

• Extravasation (most common complication): Fluid leaks into the soft tissue – recognizable by swelling around the insertion site. Cause: needle not in the medullary cavity, penetration through the far cortex, or fractured bone. Action: remove the needle, choose another site
• Compartment syndrome: Rare but serious consequence of unrecognized extravasation during pressure infusion
• Osteomyelitis: Very rare (< 0.6%), risk increases with dwell time. IO access should therefore be removed within 24 hours and replaced with IV access
• Fat embolism: Theoretical risk, clinically rarely relevant
• Fracture: Extremely rare, primarily in osteoporotic bone or with excessive force
• Growth plate injury in children: Not expected with correct technique and insertion site

Dwell Time and Removal

• IO access is an emergency solution – not intended for long-term therapy
• Maximum recommended dwell time: 24 hours (ideally shorter)
• Once reliable intravenous access has been established, the IO access should be removed
• Removal: Attach a Luer-Lock syringe to the needle hub and withdraw the needle with a rotating motion (do not bend). The EZ-IO needle is removed using the supplied syringe
• Apply a sterile dressing to the insertion site

Common Mistakes in Practice

• Hesitating too long: The most common mistake is deploying IO access too late. Three, four, five failed IV attempts during cardiac arrest waste valuable minutes
• Wrong needle size: A needle that is too short in obese patients leads to malposition
• No aspiration AND no flush: At least one of the two should be performed for placement confirmation
• No lidocaine in conscious patients
• Forgetting to flush after drug administration: Without flushing, a significant proportion of the drug remains in the medullary cavity
• IO access as a CVC substitute: IO access is not a replacement for a central venous catheter in stable patients

Practical Training

Intraosseous access is a procedure that lends itself excellently to training under realistic conditions – and should be trained regularly. Puncture technique on bone models provides the characteristic tactile feedback of cortical penetration that no theoretical description can adequately convey. In the Emergency Physician Refresher Course by Simulation Tirol, you have the opportunity to practice IO access hands-on at various insertion sites, train proper needle selection, and solidify integration into the resuscitation algorithm under realistic time pressure. Because when it matters, every step must be second nature.

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