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TECH TIPS: INTRAOSSEOUS CATHETERS
Linda Schneider, LVT
Intraosseous catheterization can be a valuable technique when patients with inaccessible peripheral vessels or those in circulatory collapse need fluids, blood products, or drugs. It provides quick access via bone marrow sinusoids and medullary venous channels, allowing rapid delivery of fluids (up to 11 ml/min) to neonates, small animals, and birds.
An intraosseous catheter is contraindicated if the patient is septic, has a bone or skin infection, or a recent fracture at the site. It also carries certain risks, including osteomyelitis, damage to the epiphyseal plate, or pain during fluid administration (pain is usually attributable to cold or irritating solutions, putting too much weight on the needle, or trying to infuse a large volume of fluids too quickly).
The catheter can be placed in a variety of sites, for example, the proximal tibia, the trochanteric fossa of the femur (the preferred site for puppies and kittens under six weeks of age), the ilial wing, the ischium, the greater tubercle of the humerus, or the distal ulna (in birds). The size, species, and body condition (e.g., obese or heavily muscled) of the patient must be considered in choosing an appropriate site. (A note of CAUTION: in birds, the humerus is and the femur may be (depending on species) a pneumatic bone; attempting to administer fluids through these sites will cause iatrogenic drowning).
A 15-18G bone marrow needle, a Cook intraosseous access needle, a 20G x 3.75cm spinal needle (for cats and puppies), or an 18-25G hypodermic needle (for neonates and birds) may be used for catheterization. The catheter must be placed aseptically and secured to the skin. Patency is maintained by flushing q 6 hrs with 1-2 ml of heparinized saline; the catheter may be left in place up to 3 days.
The following is a step-by-step guide to placing an intraosseous catheter:
1. Clip and surgically prepare the site.
2. If the patient is conscious, infiltrate 0.5-1 ml of 2% lidocaine through a 25G needle into the skin, subcutaneous tissue, and periosteum.
3. Have an assistant stabilize the site. This person will rotate the limb as needed to give access to the site and will apply counter pressure.
4. Flush the needle with an anticoagulant.
5. Visualize the bone and orient the needle parallel to the marrow cavity in which it will be placed.
6. Using a rotary action and significant pressure, penetrate the cortex of the bone.
(Continued on page 8)
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