Comparison of two different intraosseous access methods in a physician-staffed helicopter emergency medical service – a quality assurance study

Our primary objectives were to evaluate the insertion times, insertion sites, complications and flow rates in two different intraosseous devices used by our HEMS. The secondary objectives were to describe IO insertion criteria and main patient categories.

The study was designed as a quality assurance study in our HEMS based at Haukeland University Hospital, Bergen, Norway. This service is operational 24/7 and is a physician-staffed service. Seven prehospital anesthesiologists and 10 flight paramedics performed the IO insertions and collected the data prospectively. All patients requiring IO from January 1st, 2014 to November 30th, 2016 were included in the study. There were no exclusion criteria.

Our HEMS is equipped with two different IO devices: EZ-IO (® Vidacare Corp, San Antonio, Texas) and FAST-Responder (® Pyng Medical Corporation, Vancouver, BC, Canada). EZ-IO is a battery powered device enabling 500–1000 insertions [13]. EZ-IO has three different needle sizes (the smallest is certified down to 3 kg) [14]. It is most commonly used in three different insertion sites (proximal and distal tibia and the humeral head). In 1997, FAST-1 was the first FDA approved sternal IO system. In 2013, PYNG launched FAST-R, a modified version of FAST-1, to meet the needs of civilian emergency medical services and hospital critical care personnel. FAST-R is a disposable semiautomatic device for sternal insertion only, in which the insertion site is located just below the sternal notch. It cannot be used in children < 12 years of age [15]. Only one attempt can be made per FAST- unit, whereas multiple attempts are possible using the EZ-IO [12].

The data was analyzed for insertion time, flow, indication for IO, insertion site and complications. IO device placement was confirmed by loss of resistance, aspiration of bone marrow or blood, and/or administration of saline and fluid administration. Insertion time was recorded in seconds from placement against skin until vascular access was confirmed by aspiration of bone marrow or infusion of fluids. Flow was evaluated based on drip chamber flow and categorized as very good (continuous flow without pressure bag), good (fast drip without pressure bag), adequate (slow drip without pressure bag) or poor (poor flow and in need of pressure bag). All primary and final insertion sites were recorded. The physicians recorded insertion related complications such as technical issues, extravasation, IO needle detachment, failed aspiration, fracture when inserting, insertion time exceeding 30 s and difficulty in localizing insertion site. Patient journals were checked for all patients admitted to the hospital for late complications, such as osteomyelitis, fracture after IO insertion or compartment syndrome. In case of missing data, the attending prehospital physician was contacted to provide supplemental data.

A total of 93.9% of the insertions were successful on the first attempt. The remaining 6.1% of the insertions were successful on the second attempt. The median insertion time using the EZ-IO was shorter compared to FAST-R: 15 s and 20 s, respectively. A significant difference in insertion times was found when we included the outliers (Fig. 2). A comparison of flow is illustrated in Fig. 3.

Insertion complications when using EZ-IO included extravasation (2.4%), aspiration failure (11.9%) and insertion time > 30 s (4.8%). Using FAST-R, complications were reported such as user failure (12.5%) and insertion time > 30s (12.5%). It was reported that 8% of the patients experienced pain during infusion. A total of 34.7% of the patients survived until hospital admittance, and 20.4% were alive after 30 days. No cases of long-term insertion complications were described in the in-hospital journals at discharge (or death).

IO was used as a bridge to later IV in 32%. In 28%, the IO insertion was used because of failed IV access. In 15%, patients received IO parallel to IV attempts. All IO insertions were made on critically ill or injured patients.

The main EZ-IO insertion site was in the proximal tibia (90.5%); however, 9.5% of the EZ-IO were inserted in the humerus. All FAST-R insertions were sternal (100%). With EZ-IO, 2.4% of the tibial insertions failed, and another successful attempt was made in the humeral head. Of the patients receiving FAST-R, 25% of the insertions were reported as failures. These patients subsequently received successful tibial insertions using the EZ-IO.

In most cases, the patient needed medications (77.6%) and/or fluids (55.1%). Plasma or whole-blood was administered in 10.2% of cases. In 6.1% of the patients, nothing was administered through the IO.

To our knowledge, this is the first study comparing FAST-R and EZ-IO. In general, we experienced a low complication rate using both IO techniques. Our study showed a high insertion success rate on the first attempt, and all insertions were successful after two attempts. Although the EZ-IO may be a faster technique, our study suggests that the FAST-R may have a place when high-flow infusion rates in patients are required.

Calkins et al. described two failures in 31 attempts with sternal placement using FAST-1 caused by lack of continuous increasing pressure over the sternal insertion site [12]. Regarding the FAST-R insertion failures in our study, the patients subsequently received successful IO insertions with the EZ-IO. This finding may indicate that some training with the devices is recommended.

Using the EZ-IO, extravasation occurred in 2.3% of the patients, and aspiration failure was experienced in 11.9% of the cases. In 2.3% of the patients receiving EZ-IO insertions, low battery caused an insertion time > 30s. Compared to FAST-R, this result shows that EZ-IO has an expected shelf-life, which is estimated by the manufacturer to be approximately 10 years or 500 insertions. However, aspiration failure was regarded as a complication and occurred using both IO methods. This issue could result in physicians attempting another IO insertion, even though the previous IO might have been correctly inserted in the intramedullary space [13, 16]. Hammer et al. also showed that both methods are easy to use, even by medical students without any specific training [11]. In a prehospital environment, the physician tends to choose the method he or she is familiar with since IO is mainly used as a rescue technique. Our HEMS has good experience using the EZ-IO, which could explain the low number of FAST-R insertions.

We found a significant difference in insertion times, as we could not exclude the outliers from the data. However, given our low number of FAST-R insertions, the outliers have a huge impact on the analysis. In a study conducted by Hammer et al., no significant difference in insertion times or in first pass insertion success rates were found between EZ-IO and FAST-R [11]. This result might indicate that a higher number of FAST-R insertions could have improved our insertion times since we observed a minimal difference in median insertion times. Nonetheless, comparing studies may be difficult due to different patient populations and study protocols [17].

We found that none of the FAST-R infusions needed a pressure bag to maintain a very good flow. None of the EZ-IO insertions experienced very good flow, and 33.3% needed a pressure bag. Pasley et al. concluded that the sternal IO provided a more consistent and higher flow rates compared to tibial or humeral insertions [2].

Our results also showed a larger number of EZ-IO insertions in the proximal tibia compared to the humerus, which was also the case in a previous study conducted in our HEMS. This site may be preferred in different HEMSs in Norway and other European countries due to an easy detectable landmark, and it has the advantage of not interfering with ongoing cardiopulmonary resuscitation (CPR), parallel IV insertion or assisted ventilation [3]. With FAST-R, the only option is sternal insertion. This site may not always be easily accessible, as it is close to the compression site during CPR. A blunt trauma to the sternum may also prevent FAST-placement [12]. This factor may explain why our physicians or flight paramedics may prefer EZ-IO for primary insertion.

Almost all medications and fluids, as well as blood components, can also be administered through a IO access [11]. Our findings support this approach, as our patients received necessary drugs, crystalloids, plasma or whole blood. In 3 patients, the IO remained unused. This finding may indicate that a certain overuse in this patient group will be inevitable.

We found a higher number of IO insertions during our study period compared to an earlier study in our service [3]. Increased use of IO may indicate that the threshold for using IO has decreased following increased user experience with IO in our service or that improved devices are available. All the insertions were made by trained physicians and paramedics with experience in establishing IV access. Compared to the study conducted by Sunde et al., we recorded a lower number of IO insertions in pediatric emergencies [3]. This difference may indicate that our crews have improved their skills in establishing IV access in younger patients. In our HEMS, IO is primarily used as a rescue technique if other attempts at vascular access fails, and the technique needs to be reliable. The use of IO is generally recommended as a rescue technique in critically ill or injured patients if intravenous access cannot be achieved. In situations in which the patients suffer from severe hypovolemic/hemorrhagic shock, IV access is difficult or impossible, and our operational, prehospital conditions make this issue even more challenging. Thus, research is essential to determine which device is the most efficient in a prehospital service [3]. Additional clinical studies comparing intraosseous devices and insertion sites in the prehospital environment are needed. New IO methods may require more research to determine the best IO device.

A limitation in our study is the limited number of IO insertions, especially using the FAST-R method. Additionally, the evaluation on flow rate is based on the physician’s assessment, with no objective volume measurements. A randomized controlled study would be difficult to conduct, as FAST-R cannot be randomly inserted in all patients, excluding pediatric patients.

Our study has been performed prospectively in a prehospital setting, involving all the different factors one has to consider when establishing an intraosseous infusion in critically ill patients. The insertions were all made by the same HEMS crews with the same training and medical background, which we believe reduces the interpretation bias. This approach has given a picture of the functionality and efficiency of the method used, as well as complications that might not be reported in a controlled research environment.