Clinical Exercise: Intraosseous Cannulation (humerus)

Scenario:

An unconscious patient in their late teens is flown into the Shock Trauma facility suffering thoracic and pelvic injury from an unsecured impact during a motor vehicle collision. The patient is exhibiting rapid blood pressure drop during the helicopter evacuation and is experiencing difficulty breathing from the thoracic injury.

The airway members of the trauma team immediately start working around the patient to manage the acute respiratory distress. The emergency medical technicians on the medevac helicopter report they were having difficulty inserting an intravenous line during transport and could not deliver fluids into the circulation.

Diagnosis:

The major torso and pelvic injuries coupled with rapid blood pressure loss indicate significant vascular trauma and risk of exsanguination (bleeding to death) from as yet unidentified internal rupture of a vessel or vessels. The hypotensive emergency (blood pressure drop) coupled with the report of difficulty in intravenous insertion from the EMT's, makes you suspect there is significant circulatory vessel collapse.

You recognize that you need to act immediately to provide a large bolus (volume) of fluid to sustain blood pressure/circulation and you are not confident of being able to establish intravenous access with the suspected vascular collapse. Thus, you need an alternate location to deliver rapid, large boluses of fluid to stabilize the patient at a location that will not interfere with any thoracic or pelvic repair. You are also concerned that the pelvic injury may impede flow of any fluids administered to the lower extremities. 

You decide that the best approach is to insert an intraosseous cannula into the humerus so that you can deliver fluid support.

Mechanism:

In cases of vascular collapse it can be difficult (or impossible in infants and young children) to establish a peripheral intravenous catheter. An alternative method is to provide fluid into the marrow cavity of one of the large bones. This marrow cavity of large bones is highly vascularized with drainage to a central venous canal, then into emissary veins leaving the bone, and into the central circulation. The marrow cavity essentially functions as a non-collapsible venous access route that can support rapid infusions of large volumes of fluid.

In cases of vascular collapse the intraosseous cannulation procedure is much faster to perform than central or peripheral lines. The method was traditionally recommended only in children (and almost always used in children younger than 6), but studies in the last 15 years have shown that this is an effective approach at all ages. However, in older individuals the thicker bone and smaller marrow cavity can make the approach more difficult and potentially fracture bone in the area.

The proximal humerus is a common site as it provides readily palpable landmarks and only a thin layer of cortical bone. Other sites in the adult include the tibia (proximal or distal) and sternum (supports the highest flow rate, but in our scenario involving cardiopulmonary resuscitation and possible thoracic surgery it would not be usable).

Treatment (perform these steps on the donor in a mock-procedure):

To treat this patient you need to insert a needle through the outer cortical bone layer of the humerus into the marrow chamber. A variety of devices have been developed for this function ranging from needles with flanges/knobs through to motorized drill devices (reducing fracture risk over manual approaches).

PREPARATION: Send a member of your team to the instrument supply tables to fetch two syringes (so someone can work on left and right side of your donor at the same time) and five 16 gauge needles (one per student). While not the standard intraosseous needle style it will be suitable for the exercise.

CAUTION: exercise care when handling needles to prevent impaling yourself or a colleague. Needle-stick injury is the leading cause of accidental blood-borne pathogen infection in hospital staff.

Setup: Remove the clear base cap of the needle. With the needle still in the protective sheath attach the needle firmly to the syringe, locking it in place with a twisting motion into the threads on the syringe. Remove the protective cap only when you are ready to use the needle at step 4 below.

1) The patient is positioned supine with the upper limb at their side (i.e. adducted) with a slight internal rotation (hand over umbilicus).

The internal rotation is likely impossible in a donor to to reduced flexibility of embalmed joints, so use the closest approximation of the position the arm that is achievable for the exercise.

2) If time permits the area would be cleaned with antiseptic and a local anesthetic injected.

3) Identify the humeral tuberosity located on the proximal humerus (either or both arms can be used).

In a donor, palpation is difficult so reflect the skin you have dissected away from the shoulder to make it easier.

You can approach from inferior by pressing against the mid-shaft of the humerus and pressing firmly working superiorly until you reach the bulge of the greater tuberosity of the humerus.

You can also approach from superior by grasping the head of the humerus on the anterior and posterior side. Then feel on the lateral side centrally located between your other fingers for the bulge of the greater tuberosity of the humerus.

In a clinical emergency, as long as you hit the humerus 'near enough is good enough' for positioning.

4) Place the needle directly against the greater tuberosity of the humerus and insert the needle through subcutaneous tissue aiming at the bone.

Have one of your team hold the arm steady during the procedure in order to minimize the chance of the arm/needle slipping away from the correct target position.

Since the axilla neurovascular bundle runs medial to the humerus, placing your needle on the lateral humeral surface limits the risk of striking the bundle.

5) Upon reaching bone, hold the needle tightly and press the point of the needle against the bone while rotating the needle with a back-forth twisting motion.

Firm (but not forceful) pressure should be used. Excessive pressure could result in bone fracturing in an elderly patient. It will take anywhere from 5 to 15 back-forth twists to penetrate depending on the stature of the individual. A larger individual with thicker cortical bone may require more twisting back-forth cycles.

The twisting motion rotates the tip of the needle and, in a manner similar to a trepanning drill bit, the tip of the needle will cut a channel through the cortical bone into the marrow chamber.

7) Continue the press/twisting until there is a popping sensation and drop in the pushing resistance, indicating that you have entered the marrow chamber.

8) At this step in a patient you would connect a gravity IV line and begin fluid delivery. Faster rates of infusion can be achieved by manual infusing of 30-60ml fluid boluses.

You can try injecting 10-20ml of wetting agent through the needle with your syringe. Hold the needle base with a hemostat and remove (untwist) the syringe so you can fill it with some fluid. You may find that blood clotting within the venous spaces of the marrow cavity limit how much fluid you can infuse in a donor.

There should be enough space on the humerus surface of both arms for everyone to have a chance to perform an intraosseous cannulation. Use a new/fresh needle for each insertion as the process of perforating the bone will blunt each needle.

NOTE: when finished the procedure ensure that the syringe and attached needle are collected in one of your trays and transported to the sharps containers for disposal.
Do not attempt to re-cap a needle - Re-capping is a leading cause of needle-stick injury.
Never transport needles by hand - Always transport entire syringe/needles in a tray. 

Outcome:

The rapid infusion of fluids stabilizes the blood pressure allowing the trauma surgery team to determine the extent of the patient's injury. After considerable trauma surgery the patient makes a full recovery, and hopefully recognizes the importance of wearing a seatbelt in a motor vehicle.

Addendum:

The proximal tibia is another common site for intraosseous cannulation. If you are interested, a version of this scenario and instructions for a proximal tibial intraosseous cannulation can be found by:              ------ clicking here ------>