Page 58 - JSOM Spring 2024

no dropouts or withdrawals. Students averaged 1.6 (SE 0.1) FIGURE 6 Times to fill blood bag volumes with ruggedized lock
attempts to achieve IV access success (range 1–7), with 70% (RL) and straight stick (SS) techniques.
requiring a single attempt and 17% requiring two attempts.
The antecubital location accounted for 96% of attempts, fol-
lowed by the forearm (4%), and upper arm (<1%). The num-
ber of attempts and location did not significantly differ by SS
and RL and are therefore not considered for further analysis.
Incomplete fills after successful IV access were statistically
similar (p=.87) for SS (20%) and RL (19%).

Hypothesis 1: First-Attempt Success
SS (76%) trended higher than RL (64%) in first-attempt veni-
puncture success, but the 12% difference did not reach statis-
tical significance (p=.07).

Hypothesis 2: Time to IV Access
Figure 5 shows that SS (448 [SE 23] s) was significantly faster *p<.05; †p<.01.
than RL (558 [SE 31] s) in time to achieve IV access (p<.01).
equipment, but did not like that the SS was less secure, re-
FIGURE 5 Time to venipuncture (VP) and total donation time for quired a new bag if the initial IV attempt failed, and was un-
ruggedized lock (RL) and straight stick (SS). comfortable for the patient. Some students commented that
the SS needle was unnecessarily long, making SS less secure
and potentially more painful for the donor. Study participants
liked that the RL was more secure, reliable, sanitary, and less
painful for the donor, as well as the utility of swapping out
collection bags, but they did not like the number of steps and
the slower fill times.

Discussion
The present study makes a novel contribution to the literature
by being the first investigation specifically designed to contrast
the two common methods for acquiring whole blood in aus-
tere environments on battlefield-relevant measures.
*p<.01 versus SS. SS outperformed RL in all objective measures, including some-
what higher rates of first-attempt IV access success, significantly
Hypothesis 3: Collection Bag Fill Rate faster IV access times, significantly faster blood collection times,
Figure 6 shows that SS and RL were essentially identical at and significantly faster total times. In contrast, RL outper-
100-g collection bag weight. However, SS was significantly formed SS in most subjective measures, including significantly
faster than RL at each measured increment from 300g to com- greater preference, confidence, and potential use in a combat
plete bag fill (each p≤.05 or p<.01). environment. These intriguing results are discussed in the fol-
lowing sections.
Hypothesis 4: Total Time
Figure 5 shows that SS (1026 [SE 56] s) was significantly faster Hydrodynamic Explanation of
than RL (1241 [SE 52] s) in total time (p<.01). This translates Filling Rate Differences Between SS and RL
to SS averaging about 3.5 minutes faster than RL in total time. The comparative disadvantage of the RL in slower fill times
can be explained, at least in part, by the laminar flow of a
Hypothesis 5: User Preference viscous liquid through a cylinder, as described by Poiseuille’s
On the postcourse survey, 5% of the participants had no pref- equation (Equation 1).
erence between SS and RL. Of the remaining, the majority pre- πR ΔP
4
ferred RL (60%) over SS (40%; p<.05). Study participants were Q =
twice as likely to indicate that they would eagerly take the RL μL
(48%) into combat compared with SS (22%; p<.01) and roughly
half as likely to indicate that they would reluctantly take the Equation 1: Poiseuille’s Equation
RL (13%) into combat compared with SS (22%; p<.05). Confi- Q is flow rate, R is radius, ∆P is pressure gradient across
dence was significantly higher for RL (4.4 [SE 0.1]) than SS (4.1 the cylinder, μ represents blood viscosity, and L is cylinder
[SE 0.1]) following training (p<.01). Of those who expressed an length.
opinion, 73% considered RL more reliable (p<.001) and 57%
considered RL easier to use (p=.09). SS was considered faster For the SS, blood flow is constrained for 1.25in through the
than RL by 73% of the students (p<.001). 16-gauge needle. RL flow is constrained for twice that length be-
cause the blood travels through the 16-gauge catheter and then
Open-ended survey responses revealed that study participants through the needle (1.25in catheter + 1.25in needle = 2.50in
generally liked that the SS was fast, simple, and required less total constrained length).

56 | JSOM Volume 23, Edition 1 / Spring 2024