Study arm: In this type of study, patients are split into groups and assigned to receive one treatment or another. Each group receiving the same intervention is called an “arm.”
Power calculation: Researchers predict the number of patients or events needed in a study to reach statistical significance.
Five recent studies on intraosseous (IO) will help ring in the New Year. Each of these has something unique to add to our knowledge and practice, but together they tell a more powerful story.
Intraosseous “IN” the Research
Reades R, Studnek JR, Vandeventer S, et al. Intraosseous versus intravenous vascular access during out-of-hospital cardiac arrest: A randomized controlled trial. Ann Emerg Med. 2011. 58(6):509–516.
Thank you to Mecklenburg (N.C.) EMS for undertaking this great study on intraosseous first attempt success rates during adult cardiac arrests. It’s by far the most robust of the studies reviewed this month and published in a prestigious journal.
A total of 182 out-of-hospital cardiac-arrest (OHCA) patients were prospectively randomized to receive a peripheral IV, an IO inserted in the humerus (H-IO) or an IO inserted in the tibia (T-IO). The three groups, also called study arms, had roughly the same number of participants. Success rates were fastest and best for the tibial IO group (91%). Second best was humeral IO (51%), and peripheral IVs came in last at a 43%
Interestingly the H-IO was successfully inserted 71% of the time, leading the authors to conclude that it’s a feasible route of insertion, but it became dislodged in 20% of the cases. The researchers speculate that this is perhaps due to shallow insertion (the needle being too short) or simply because of entanglement with resuscitation in the torso. Unfortunately, the researchers didn’t list the needle lengths used in these cases.
These same authors had calculated an observational study of IO in 2009 and used it to do a power calculation for this one. This is essential when trying to find statistically significant results with three different study arms. Each crew was contacted by phone for a post-incident debriefing, allowing for improved data collection. Great research.
Wampler D, Schwartz D, Shumaker J, et al. Paramedics successfully perform humeral EZ-IO intraosseous access in adult out-of-hospital cardiac arrest patients. Am J Emerg Med. 2011;Oct 24. [Epub ahead of print].
This San Antonio, Texas-based study reviewed 405 cardiac arrests, 247 of which had an H-IO placed. First-attempt H-IO success rates were 91%, and dislodgement was 2%. Tibial success rate was 95%. You may notice that this study reported four times as many cases with much higher success and lower dislodgement than the study above.
The authors list H-IO as the preferred method of access because of its proximity to central circulation and high flow rates that might benefit therapeutic hypothermia and volume replacement.
Readers should be on notice to read these papers carefully before jumping to conclusions. The original purpose of data collection in this case was for an unrelated drug study.
Retrospective secondary analysis of these data to compare IO access makes this study much weaker than the one above.
This study was funded by the San Antonio fire department but was partially supported by Vidacare, the makers of the EZ-IO device. Although the ethics of the authors are not in question and all potential conflicts were properly disclosed, the fact that a relationship with a manufacturer of the product exists puts more scrutiny on this study.
It appears we have two “dueling” groups: Reades and Studnek found considerably less success rates and high dislodgement with the H-IO. The authors found higher success rates and reference Reades’ 2009 article citing differences in previous IO experience a lack of standardization in securing methods as possible reasons for their lack of success.
IO Fluid administration Pain
Schalk R, Schweigkofler U, Lotz G, et al. Efficacy of the EZ-IO needle driver for out-of-hospital intraosseous access—a preliminary, observational, multicenter study. Scand J Trauma Resusc Emerg Med. 2011;10(19):65.
This Scandinavian group prospectively recorded 77 IO insertions in 69 adults and five children during a two-year period. Most of these (75) were done by emergency physicians with no previous IO experience. All of them except for two were successful tibial insertions.
The patient population is much more diverse in this study, including children, trauma patients and conscious patients. Of the 22 T-IOs in responsive patients, 18 reported pain on fluid administration. Lidocaine 20–40 mg helped reduce or eliminate pain in 12 cases.
This study is more of a case series because they left the decision to use the IO up to the responding physician or paramedic. A weaker study than those listed above.
Pediatric IO Use
Hansen M, Meckler G, Spiro D, et al. Intraosseous line use, complications, and outcomes among a population-based cohort of children presenting to California hospitals. Pediatr Emerg Care. 2011;27(10):928–932.
In this retrospective hospital database study, the authors looked strictly at pediatric IO insertion inside 90 different hospitals. Most of these were inserted in the emergency departments (ED) of non-pediatric hospitals. The focus was to describe in-hospital use (4% per 1,000 ED visits; 34% in cardiac arrest; 19% in trauma). The researchers found no documented or reported complications in a total of 291 pediatric IO uses during a two-year period. JEMS
What we know: IO is widely used to gain vascular access for both adult and pediatric patients. Several studies have reported poor placement success with obese patients and high incidence of dislodgment specifically in H-IO. Better success rates with H-IO have been reported with longer (45 mm) needles.
What this study adds More definitive evidence that IOs are faster and better than peripheral IVs during adult cardiac arrest and have low complications in both adults and pediatric cases. They provide evidence that humeral IO insertion is feasible, but it remains less effective than tibial IO, and it comes with a strong warning about securing methods and needle length needing to be 45 mm.
Kehrl T & Broderick E. Relationship of body mass index and increased difficulty with intraosseous needle placement: Assessment of tissue depth using ultrasound. Ann Emerg Med. 2011;58(Research Forum Abstracts_256):S263.
The authors used ultrasound to scan 75 obese patients with a body mass index (BMI) greater than 30 in an ED. The average distance to proximal tibia was 1.10 cm, distal tibia was 1.07 cm, and proximal humerus was 2.96 cm. Researchers were unable to palpate the tibial tubercle in five patients with an average BMI of 67.2. In these patients, the average distance to proximal tibia was 2.97 cm; distal tibia was 2.08 cm and proximal humerus was 3.58 cm. They concluded that a 25 mm needle is feasible if you can palpate the tubercle, but humeral insertion was not recommended.
This article originally appeared in January 2012 JEMS as “Intraosseus Intrigue: Studies examine success rates on pediatric, adult & obese patients.”