Cadaver Testing to Validate Design Criteria of an Adult Intraosseous Infusion System

Military Medicine, Mar 2005 by Johnson, David L, Findlay, Judy, Macnab, Andrew J, Susak, Lark

Introduction: The FAST 1 intraosseous (10) infusion system was designed to deliver fluids and medications into the adult sternum in the prehospital and battlefield environments. Objective: To test the prototype in 106 cadavers and excised sterna and compare it with other IO devices. Results: The insertion force was similar to that of other IO devices (mean, 8.5 kg; range, 2.3-19.6 kg). In 39 of 39 trials, the depth-control mechanism inserted the portal within 1.0 mm of a predetermined distance below the anterior surface of the cortical bone. If misplaced, underpenetration was more likely than overpenetration (mean displacement, -0.3 mm; SD, 0.5 mm). After release, the portal could not be advanced further into the manubrium. Marrow was accessed in 75 of 77 trials. Mean flow rates were 109 mL/min for normal saline solution and 102 mL/min for hypertonic saline/dextran, similar to the Cook SurFast device. Conclusion: The cadaver and bench tests demonstrated the reliability and safety of the FAST 1 system at the design/prototype stage.

Introduction

In the United States and Europe, intraosseous (10) vascular access devices are reemerging as an important field treatment option for armed services1-3 and civilian emergency medical care providers.4 The FAST 1 (First Access for Shock and Trauma) IO infusion system (Pyng Medical Corp., Vancouver, Canada) is a patented IO device for use in the adult sternum (Fig. 1). The system provides an alternative to peripheral vascular access in prehospital and battlefield environments. It has been described, illustrated fully, and compared with other IO devices elsewhere,4 the insertion methods summarized,4 and the feasibility, efficacy, and safety of IO infusion of drugs and fluids comprehensively reviewed from the military standpoint.1

In the 1920s, Drinker et al.5 first suggested the concept of IO infusion, or vascular access via the bone marrow, as a result of a study of the circulation of the sternum. Substantial research in the 1940s by Henning6 and Tocantin et al.7-13 indicated that substances injected into the adult sternum are well absorbed into the circulation, primarily via the internal mammary and azygos venous system.13,14 Unlike peripheral veins, the intramedullary blood vessels in the bone marrow do not collapse in shock.15,16

Despite the development of IO techniques and equipment, advocacy for IO infusion,9-13 and more than 1,000 successful pediatric IO infusions,17 the technique was virtually abandoned with the advent of modern intravenous (IV] therapy.18 Interest in IO infusion was renewed when it became apparent that there is a need for an alternative to peripheral IV infusions when peripheral access proves unsuccessful. IO infusion into the tibia among children is now widely accepted and is a Pediatric Advanced Life Support protocol.19 Although it is considered a reliable, effective, and relatively simple approach for emergency vascular access and fluid/medication administration,20,21 IO infusion was limited almost exclusively to the pediatric population1,4,21,22 until the advent of new devices and recent research.

For adults, IO infusion is possible via multiple sites, including the iliac crest, femur, proximal and distal tibia, humerus, radius, and clavicle.3,23 The tibia is not an ideal site in adults because red marrow is replaced by less vascular yellow marrow or fat by the fifth year of life.24,25 Similarly, the pelvic marrow space, although large, has a complex shape, yellow marrow often predominates,25 and it must be accessed through thick cortical bone (2.8-6 mm) and subcutaneous adipose tissue.

The adult sternum has advantages as an IO infusion site. The sternal body is large and relatively flat and can be readily located. The sternum is usually easy to expose in trauma victims. The cortical bone covering is thin (1-2 mm), and the marrow space is relatively uniform (6-11 mm, anteroposterior).25,26 The sternum is less often fractured than the extremities, and fluids and drugs infused into the sternal marrow rapidly enter the circulation.13,14

The width and thickness of the manubrium are of concern in designing an IO device, because of the bone's position over the heart and great vessels and the consequent risks of overpenetration. Factors that affect the degree of risk of overpenetration include IO device design, insertion characteristics, user training and competence, and possibly the race or gender of the patient. To address these factors, we tested the behavior of the FAST 1 system prototypes and other IO systems. Input into the design was obtained from U.S. military medical personnel (Fort Detrick, Maryland), Canadian paramedics (Paramedic Academy, New Westminster, British Columbia, Canada), and members of the British Columbia Ambulance Service (Vancouver, Canada).

Methods

IO devices were tested on cadavers and excised sterna at the Jack Bell Research Centre and Vancouver Hospital (Vancouver, British Columbia, Canada). After an IO system was used to place an infusion tube or tubes into cadavers of various sizes, the sterna were excised and stripped of tissue, to allow macroscopic or microscopic examination of the penetration site. In some cases, the sternum was excised first and portal placement or other measurements were conducted on the excised sternum. There was no attempt to select cadavers for specific physical criteria or demographic features.