A 62-year-old woman undergoes emergency intubation during resuscitation for cardiac arrest in the ICU. The team is unable to establish intravenous access immediately. According to ACLS guidelines, what is the most common site for intraosseous (IO) access in adult resuscitation?

Explanation

## Most Common Site for Intraosseous Access in Adults **Key Point:** The proximal tibia (medial aspect, 1–2 cm below the tibial tuberosity) is the most common and preferred site for intraosseous (IO) access in adult resuscitation. It is easily accessible, has reliable landmarks, and has the lowest complication rate. ### Intraosseous Access Sites in Adults | Site | Landmarks | Frequency of Use | Advantages | Disadvantages | |------|-----------|------------------|------------|---------------| | **Proximal tibia** | 1–2 cm below tibial tuberosity, medial surface | Most common | Easy access, superficial, low complication rate | Potential tibial fracture (rare) | | Proximal humerus | Anterior aspect, surgical neck | Second choice | Good alternative when tibia unavailable | Deeper, requires more skill | | Distal femur | Medial condyle, 2–3 cm above knee | Less common | Useful in lower limb trauma | Proximity to knee joint, deeper insertion | | Anterior superior iliac spine | Medial aspect of ASIS | Rarely used | Alternative in specific cases | Difficult landmarks, deeper, higher risk | **High-Yield:** IO access is indicated when: - IV access cannot be obtained within 3 minutes of resuscitation - Severe peripheral edema or burns - Profound hypotension or shock - Cardiac arrest requiring immediate drug administration ### Why Proximal Tibia Is Preferred 1. **Superficial location** — minimal soft tissue depth 2. **Reliable landmarks** — tibial tuberosity is easily palpable 3. **High success rate** — 90–95% first-attempt success in trained operators 4. **Low complication rate** — compartment syndrome, fracture, and infection are rare 5. **Rapid access** — can be established in <60 seconds 6. **Adequate flow rates** — can deliver fluids and medications at rates comparable to peripheral IV **Clinical Pearl:** IO access provides equivalent drug delivery and fluid resuscitation compared to central venous access during cardiac arrest. All ACLS medications (epinephrine, amiodarone, atropine) can be administered via IO with normal dosing. **Mnemonic: "PHAT IO" — Proximal Humerus, Proximal Tibia, Anterior ASIS, Tibial tuberosity.** Proximal tibia is listed second but is most commonly used. ### Technique for Proximal Tibial IO 1. Patient supine or semi-recumbent 2. Identify tibial tuberosity (bony prominence below knee) 3. Insert needle 1–2 cm below tuberosity on medial surface 4. Angle 90° to skin or slightly caudal (10–15°) 5. Advance with firm, twisting motion until "pop" or loss of resistance 6. Confirm placement: needle stands upright, aspirate bone marrow, flush with saline 7. Secure with tape or dressing ### Contraindications to Proximal Tibia IO - Fracture of ipsilateral tibia or femur - Severe soft tissue injury or burns at insertion site - Osteogenesis imperfecta or other bone disease