January 2026
In this VETgirl online veterinary continuing education blog, we highlight the important, life saving, time saving circulatory access skill – intraosseous catheter placement! Ideal for neonates, exotics, and those challenging “I swear this patient has no veins” moments, IO catheters, with practice, are quick, relatively simple skills we all need to know how to perform!

Want to see how to place an IO catheter? Check out this VETgirl instructional video HERE! Have you heard of the EZ IO gun? Check out this VETgirl instructional video to see how IO catheters can be made EZ!

Intraosseous Catheter Placement in Small Animals: A Practical VETgirl Guide

When seconds count and vascular access is critical, sometimes our trusty cephalic or saphenous veins just won’t cooperate. Tiny kittens, shocky puppies, dehydrated geriatrics, and those “I swear this patient has no veins” moments all test our patience (and our skills). That’s when intraosseous (IO) catheters can save the day. At VETgirl, we want to make sure you feel confident reaching for this advanced technique not only as a “Hail Mary,” but as a reliable tool for fluid therapy, drug delivery, and stabilization in those tough cases. Let’s break down why, when, and how to use IO catheters, plus some pearls on maintenance and troubleshooting.

Why IO Access?

The medullary cavity of bone is richly vascularized, draining directly into systemic circulation. That means anything you can give IV, you can deliver IO, including fluids, medications, blood products, and anesthetics. No matter how dehydrated or shocky your patient is, the medullary cavity won’t collapse like peripheral veins can, so it’s a reliable target for vascular access even in your critically ill patients. IO access is generally considered close to equivalent to IV access in terms of pharmacokinetics, making it a life-saving bridge until IV placement is possible — or as a primary route in very small patients.

Where to Place IO Catheters

In dogs and cats, several landmarks are practical and accessible. The key is choosing cortical bone that’s easy to access and away from large muscle masses.

 

Where you place an IO catheter often comes down to training, patient size, patient comorbidities, and species – in birds it’s vital to avoid IO catheter placement in pneumatic bones which is why the distal ulna and proximal tibiotarsus are more commonly used. In dogs and cats of any size, the proximal humerus and proximal femur are classic, dependable choices, though angling 90 degrees through the medial proximal tibia is also an easy option as long as the medullary cavity diameter is wide enough for the catheter tip. For neonates, insertion through the proximal tibia and advancing the catheter antegrade (toward the floor, along the shaft) is a quick win because there is very little soft tissue in the way, making access fast and reliable.

IO Catheter Contraindications and Cautions

While IO catheterization can be a lifesaving skill in emergency situations, it’s not without its limitations and risks. Here’s what you need to keep in mind:

Contraindications

• Avoid IO placement in fractured bones or bone with previous puncture (within 48 hr.); extravasation of fluids and drugs will occur.
• Don’t place through sites with active skin disease (e.g., infection, burns).
• In birds, steer clear of pneumatic bones (i.e., humerus, keel, pelvic girdle, clavicle, skull, lumbar and sacral vertebrae) — fluids here can be disastrous.

Potential Risks & Complications

• Epiphyseal injury in neonates: rare, but damaging growth plates can permanently alter bone development
• Avulsion fracture: avoid inserting through the tibial tuberosity due to the risk of avulsion injury upon IO catheter removal (this VETgirl has seen it firsthand!)
• Fracture at insertion site: rotary and pneumatic devices can create microfractures at the insert site, though clinically significant injury is uncommon
• Sciatic nerve damage: insertion into the trochanteric fossa on the proximal femur risks contacting this major nerve
• Catheter dislodgement: the most common complication, causing leakage of fluids or medications into surrounding tissues
• Infection: the next most common complication, ranging from subcutaneous abscesses to osteomyelitis; IO catheters should be considered temporary and ideally removed once IV access is secured

Pain Considerations

IO catheter placement hurts in conscious patients. If time allows, a topical anesthetic cream can help. In urgent cases, infiltrating local anesthetic down to the periosteum is an option.

IO catheter in proximal humerus in a cat. (Image courtesy of Amy Kaplan-Zattler)

Infusion Notes

IO catheter flow rates hinge on a few key factors: the catheter’s position within the medullary cavity, the catheter diameter, and which bone it’s placed in. If the bevel rests against or is too close to the inner cortex, your infusion may meet resistance. Studies show that the humerus tends to allow the fastest flow rates, followed by the femur, with the tibia lagging behind. Although it’s proven generally true so far that you can give anything IO that you’d give IV, keep in mind that not all drugs and fluids have actually been tested through this route yet. And don’t forget— rapid, high-pressure infusions or cold fluids delivered in the vasculature can be uncomfortable in awake patients.

Confirming IO catheter placement in a reptile’s tibia. (Image courtesy of Amy Kaplan-Zattler)

Equipment: What You’ll Need

  • Sterile prep supplies (chlorhexidine/alcohol, gloves)
  • IO catheters +/- administration device:
    • Manual insertion with 18–22g hypodermic needle, spinal needle, or bone marrow needle with stylet
    • Powered or spring-loaded insertion device or similar IO specific placement device with device-associated IO catheters
  • Leur-lock syringe with heparinized saline or flush solution
  • Leur-lock extension set (pre-filled with sterile saline or flush solution)
  • Securement materials (tape, bandage, vet wrap)
    Optional: lidocaine for local infiltration in conscious patients (the periosteum is sensitive!)

Examples of what can be used as IO catheter options for manual insertion (Image courtesy of Amy Kaplan-Zattler)

Step-by-Step: Placement Technique

  1. Prep the site by sterile technique — just like you would for an IV catheter.
  2. Stabilize the limb with your non-dominant hand and palpate your landmark with your dominant hand.
  3. Line up the orientation of your needle +/- insert the needle through the skin and make a shallow pierce in the periosteum (like seeding a drill)
  4. Advance the needle:
    • Manual – steady pressure with twisting/boring motion until you feel a “pop” into the medullary cavity
    • Rotary device – maintain firm contact, engage the trigger, and apply gentle constant pressure to advance the catheter through the cortex until a sudden loss of resistance is felt
  5. Remove the stylet (if present) and attach a syringe
  6. Confirm placement:
    • Flushes easily without resistance or SQ swelling
    • Catheter stands firmly upright without wobbling (e.g., feels tightly “seeded” in the marrow)
    • Aspiration of marrow (sometimes possible), which helps support appropriate placement
  7. Secure the catheter with tape, bandage, or commercial IO stabilization device

What Can You Give IO?

• Fluids (e.g., crystalloids, colloids, blood products)
• Emergency drugs (e.g., epinephrine, atropine, lidocaine, vasopressors)
• Anesthetics/induction agents (e.g., propofol, alfaxalone, ketamine, etc.)
Anything you’d give IV, you can typically give IO at the same doses and rates.

Maintenance and Monitoring

IO catheters are not long-term solutions. We don’t yet have evidence-based guidelines on IO catheter duration, but we do know that risk of infection increases over time. So a good rule of thumb is to remove the IO catheter once reliable IV access is achieved, generally within 24-48 hours. But if it’s all you’ve got, use it! This VETgirl has successfully maintained an IO catheter in a dog for 4 days without developing any secondary complications during use or after removal. Just keep in mind that IO catheters are often hard to “wrap.”

Care Tips:

• Flush periodically (similar to IV catheter care) to maintain patency and immediately prior to all IO administrations
• Check the insertion site frequently for swelling, pain, heat, or discharge
• Bandage securely but avoid excess pressure that compromises perfusion
• Remove immediately if there’s evidence of infection, extravasation, or mechanical failure
• Remove once IV access is achieved

Case Example: 12-Week-Old Puppy in Shock

IO catheter placed in the femur of a puppy for initial resuscitation (Image courtesy of Amanda M. Shelby)

A 12-week-old Chihuahua puppy presents with hypoglycemia and dehydration, collapsed peripheral veins, and hypothermia. Peripheral IV attempts in multiple locations fail. IO catheter placed in the proximal femur with a 20g hypodermic needle is performed. Immediate 50% dextrose (0.5-1.5 mL/kg, diluted 1:3 with an isotonic crystalloid) and isotonic crystalloid fluid bolus are administered IO. Within minutes, the puppy regains mentation and perfusion improves. This allows IV access to be obtained for continued medical therapies. This is the kind of scenario where IO access literally saves lives. VETgirl loves IO catheters for the young the tiny, exotics, and for when seconds count!

Take-Home Points

• Intraosseous access is fast, reliable, and life-saving when IV access fails.
• Familiarize yourself with landmarks and technique before you’re in a crisis.
• Treat IO catheters like IV catheters — aseptic placement, securement, and regular monitoring.
• Use IO catheters as a bridge until IV access is secured, or as primary vascular access in neonates/exotics.

Final Thoughts

Don’t wait until your next code or collapsed puppy to dust off your IO skills. Like anything in veterinary medicine, confidence comes from preparation and practice. Place a few IO catheters in cadavers, practice with your EZ-IO® device or with manual insertion, and train your tech team.
Because when that critical patient rolls through your door, IO access may just be the reason they get to walk back out again…

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