The Pre-brief
In critically ill patients presenting with shock, severe hypovolemia, cardiac arrest, major trauma, and difficult peripheral IV access, providers have 3 options with which to draw labs and administer resuscitative treatments
- Insertion of an ultrasound-guided peripheral venous catheter
- Insertion of a central venous catheter
- Placement of an intraosseous (IO) device
IO placement is a safe and rapid method for obtaining parenteral access in patients with difficult venous access. The IO route is the fastest way to infuse fluids, medications, and blood products in emergency situations including cardiac resuscitation.
Bones are better:
The anatomical characteristics of bone make IO access an optimal location for the administration of resuscitative products.
Bone marrow is highly vascularized and is connected to the central vascular system via the medullary venous channel. Furthermore, the non-collapsibility of compact bone and the presence of bone spicules where marrow is contained makes these cavities stable even in the presence of shock or severe hypovolemia – a stark contrast to veins.
Medications:
Theoretically, any medication that can be given IV can also be given IO. The dosing for IV and IO routes is equivalent. Vesicants such as vasopressors can be administered IO; however, an IO should only stay in place for a maximum of 24 hours to prevent infectious complications.
Several studies have demonstrated the pharmacokinetic equivalence of medications administered IV vs IO. However, the administration of ceftriaxone, phenytoin, tobramycin, and vancomycin may result in lower peak serum concentrations based on one adult study. Furthermore, there are a few case reports in the pediatric population indicating that IO administration of adenosine for the treatment of supraventricular tachycardia is not an effective route and that even despite escalating the dose, the arrhythmias could not be converted.
Each medication administered via IO route should be flushed with 10 mL of saline to ensure that the medication does not linger in the medullar cavity.
Pressure bags or rapid infusion devices are also required to enhance flow rates and ensure that medications reach the central vascular system. Manual compression of IV bags is not sufficient. This is due to bone spicules which increase the flow resistance between the cavity and the vascular system. The mean BP in the medullary space is quite significant at roughly 20-30 mmHg (approximately 1/3 of systemic mean pressure).
Lastly, one caveat to remember when administering medications via the IO route is that IO blood samples are not reliable after drug and fluid administration due to the dilutional effect of these infusions. IO labs need to be drawn prior.
Locations:
There are 3 preferred IO insertion sites for adults:
- The proximal tibia
- The distal tibia
- The proximal humerus
The sternal location can also be considered; however, in patients undergoing CPR, chest compressions would need to be interrupted to obtain sternal IO placement making this a suboptimal location.
So the question remains, does one site offer benefit over another? There have been conflicting results in regards to studies evaluating flow rates between access points. However, there is currently more data to support that humeral IO sites may provide higher flow rates (up to 150 mL/min with the concomitant use of pressure bags) compared to tibial IO sites. Furthermore, because fluids flow easier through the humerus, less pressure is required to deliver the initial flush. Therefore, less pain is experienced with the humeral site than with the tibial sites.
Complications:
Complication rates from IO use are low. The most common complication is extravasation and reported rates vary from 1% to 22%. Rarely, extravasation can lead to compartment syndrome. Medication-related risk factors for compartment syndrome include a high total volume of fluid administered and administration of hyperosmolar fluids such as hypertonic saline.
Infectious complications can also rarely occur but can be mitigated by limiting IO use to a maximum of 24 hours.
Lastly, fat or bone marrow emboli are also possible. However, despite the high percentage of emboli occurring with IO infusions, there have been no case reports of death or significant morbidity from emboli.
Pain control:
Pain-related to IO use is not due to insertion but rather it arises from the need to overcome the inherent pulse pressure caused by bone marrow blockage in the cavity. The initial saline flush needed to unblock this cavity and create a channel for fluid flow is a source of great discomfort. Furthermore, higher infusion pressures yield faster infusion flow rates. This is the desired goal for fluid administration but also unfortunately results in a greater amount of pain.
Pain can be substantially reduced by injecting 2% preservative-free lidocaine through the IO port.
The Debrief
- The IO route is the fastest way to infuse fluids, medications, and blood products in emergency situations including cardiac resuscitation.
- IO dosing of medications is equivalent to IV dosing.
- Pressure bags or rapid infusion devices must be used to ensure medications reach the central vascular system; manual compression of IV bags is not sufficient.
- IO labs should be drawn before treatments are administered through the IO site to prevent false values secondary to dilutional effects.
- The humeral IO site offers the highest flow rate and confers the least amount of pain based on current literature.
- Pain should be preemptively treated with the use of 2% preservative-free lidocaine flushed through the IO port
References
Petitpas F, Guenezan J, Vendeuvre T, et al. Use of Intra-Osseous Access in Adults: A Systematic Review. Critical Care. 2016; 20:102.
Anson J. Vascular Access in Resuscitation: Is There a Role for the Intraosseous Route? Anesthesiology. 2014; 120:1015-31.
Buck M, Wiggins B, Sesler J. Intraosseous Drug Administration in Children and Adults during Cardiopulmonary Resuscitation. Ann Pharmacother. 2007; 41(10): 1679-86.
Goodman I, Lu C. Intraosseous Infusion Is Unreliable for Adenosine Delivery in the Treatment of Supraventricular Tachycardia. Pediatr Emerg Care. 2012; 28(1): 47-8.
Philbeck T, Miller L. Montez D, et al. Hurts So Good: Easing IO Pain and Pressure. JEMS. 2010; 35(9): 58-69.
Distal femur is gaining prevalence in many systems and has proven to be quick and beneficial for rapid resuscitation in most age groups.
Reading about the anatomical characteristics of bone and its connection to the central vascular system through the medullary venous channel was fascinating. It’s reassuring to know that IO placement is a safe and rapid method, especially in emergency situations. However, the pain associated with the initial flush and the need for higher infusion pressures does sound quite uncomfortable. The suggestion of using lidocaine to alleviate the pain is a great tip that I will keep in mind.