22. The intraosseous needle – April 2015
Administration of fluids and pharmacological agents in acute pre-hospital emergencies is a mainstay of modern practice. Most of these agents will have to work quickly but without causing problems. There are numerous routes of administration with intravenous common. In many instances gaining IV access can be very difficult and an alternative but equally effective route must be found. The intraosseous route is such an alternative.
There are different devices available for this. Frequently the device will be intended for a particular injection site as different needle lengths will be required. Typical sites include the sternum, proximal humerus, distal femur and both ends of the tibia. The sternum requires a very short needle. The humerus is particularly useful for patients where the lower body is not exposed. The tibia is very common as the target site has a flat and thin covering area.
Bone is very alive. Within the hard outer layer there is an inner layer of bone marrow at the ends of some, nerves and blood supply. Intraosseous needles are inserted into the marrow ends. Locating the correct site is important. In adults the tibial tuberosity can be located, the finger moved two cm medial then two cm upward. For children move two cm down instead of upward to stay away from the growth plate. For the distal IO needle, locate the medial malleolus. For children move upward about one cm. For adults move two cm.
The IO route should be used in any acute life threatening emergency. If a quick inspection does not offer immediate prospect of IV access, turn quickly to the IO route without hesitation. With children, there may be little to no IV options on offer even with a tourniquet applied to each limb. Don’t delay in futile searching and move to the IO within one minute if the patient is in extremis. The IO cannot be used where the bone in question has been injured from trauma. Similarly it should not be inserted into an infected limb. It should also be avoided where the fragile bone osteogenesis imperfect is present. If an upper site is chosen but unsuccessful the lower one cannot be used in the same leg to avoid drug leakage.
The IO needle is far from new in concept having been in use for many decade. It lost popularity for unclear reasons but is back well and truly. Older devices were manual screw in and difficult to insert and unpleasant to watch. Newer devices include spring loaded options such as the Bone Injection Gun (left) and the EZ-IO drill (right).
Before anything is administered through an IO needle its patency should be assessed fully. Sometimes bone marrow can be withdrawn from the needle. Many times not so. Extravasated drug can cause considerable tissue damage. Just as when using an IV, air must not be injected into the IO to avoid embolism. Fat embolism is a possibility but is uncommon. It is more likely with adults where the marrow is more yellow and less red. It is not necessarily painful to insert an IO needle however it can be painful to run drugs through it once placed. To reduce this a bolus of 1% lignocaine can be administered first as a local anaesthetic.
When administering drugs through an IO there may be a lot of resistance. Typically a bag of crystalloid is attached and wrapped in a pressure bag. This may take as much as 300mmHg to ensure flow. A 3 way tap is attached first to the IO needle. This is then secured to ensure that the IO needle is not displaced. A 50ml syringe can be used to fill with fluid then push any drug into the needle. This is particularly useful in small children where volumes administered must be carefully monitored and where fluid may be more critical than drugs in resuscitation. Experience shows that cold IO fluids do not run as well as warm.
Jeff Kenneally – www.prehemt.com