Page 46 - Journal of Special Operations Medicine - Summer 2014

throughout the experiment, and the body temperature Table 1 Time to Onset and Recovery Benchmarks in Minutes
of the swine was maintained at greater than 36.0°C. (Mean ± SD)
EMG data were obtained following a modified method Mean p
previously described by Shi et al. Subdermal needle elec- IV IO Ratio Value
8
trodes (Medtronic USA, Jacksonville, FL) were placed in Onset 0.55 (0.26) 0.97 (0.40) 0.59 .048
the sternomastoid muscle for direct EMG recording on 90
a Nerve Integrity Monitor (NIM) Response 3.0 monitor Onset max 2.90 (1.39) 4.20 (1.33) 0.58 .162
(Medtronic USA). Once baseline EMG amplitudes were 25% Recovery 6.0 (2.3) 6.6 (2.3) 0.90 .760
established, 3mg/kg succinylcholine was administered in 50% Recovery 8.9 (2.9) 8.6 (3.1) 1.03 .900
a single bolus via either a 20g IV catheter placed in an 75% Recovery 11.2 (3.4) 10.3 (3.7) 1.09 .740
auricular vein or a 15g IO needle (Vidacare Corpora-
tion, San Antonio, TX) inserted in the proximal medial 95% Recovery 12.9 (3.8) 11.4 (4.2) 1.13 0.650
aspect of the tibia, followed by a 10mL normal saline
flush. A dose of 3mg/kg was used after a standard hu- Figure 1 Comparison of individual times to 90% reduction
man dose of 1.5mg/kg failed to produce maximal EMG of EMG by route of administration.
suppression during model development.

EMG amplitudes were measured at baseline and at
10-second intervals for 2 minutes, at 30-second inter-
vals for the next 8 minutes, and then every minute for
the next 10 minutes. The animal was allowed to recover
for 60 minutes, and the experiment was conducted again
via the alternate route of administration.

The initial data were transformed to percent of baseline
and graphed as percent baseline versus time. Individual
onset and recovery data were plotted using Excel (Micro-
soft, Redmond, WA). The time from the end of injection was no statistical difference in the recovery of neuro-
to 90% reduction of baseline EMG activity (Onset ) muscular function between IO and IV administration.
90
and the time to maximum reduction (Onset peak) were The results are similar to a study in which sheep were
used to characterize the onset of neuromuscular block- administered succinylcholine via the IO route and re-
ade. Recovery from neuromuscular blockade was char- spiratory arrest was used as a measure of onset. The
9
11
acterized by the time from injection to return of 25%, investigators found the mean time to respiratory arrest
50%, 75%, and 95% of baseline EMG activity. The was 30 seconds after IV administration compared with
10
results were compared using a multivariate analysis of 57 seconds after IO administration but concluded that
variance. All analyses were performed with SPSS version it made little clinical difference. However, in emergent
18 (SPSS Inc., Chicago, IL). Significance in this study medical conditions requiring immediate endotracheal
was indicated by p < .05. intubation for airway protection, time is critical. Any
time delay in the placement of a definitive airway may
lead to unacceptable patient outcomes. Therefore, de-
Results
velopment of administration techniques that would pro-
Times used to characterize onset and duration of paraly- duce equivalent onset to IV administration when using
sis after succinylcholine administration are summarized the IO route would be useful to the emergency care pro-
in Table 1. The mean time to a 90% reduction in EMG vider. Increasing the dose of succinylcholine or adminis-
activity was statistically longer after IO administration tering a larger flush volume following administration of
compared with IV administration (p = .048). Individual succinylcholine may accelerate onset when using the IO
subject comparison of time to a 90% reduction in EMG route and should be investigated.
activity is presented in Figure 1. There was no statistical
difference in mean time to recovery of all benchmarks. Further, data on the onset and duration of succinylcho-
line administered via the sternal IO route should also be
investigated. There is a possibility that any delay in on-
Discussion
set of drug action may be minimized by administration
This study has two major findings. First, the time from via the sternal IO route, which is anatomically closer
administration to 90% reduction in EMG activity was to the effect site than the tibial IO route. This concept
statistically longer after tibial IO administration com- was demonstrated in a study comparing peak arterial
pared with peripheral IV administration. Second, there blood concentrations of Evans blue– and indocyanine

36 Journal of Special Operations Medicine Volume 14, Edition 2/Summer 2014