Resuscitation 81 (2010) 343 347
Contents lists available at ScienceDirect
Resuscitation
journal homepage: www.elsevier.com/locate/resuscitation
Simulation and education
Increase in pre-shock pause caused by drug administration before defibrillation:
An observational, full-scale simulation study
Christian Bjerre HÅ‚yera,", Erika F. Christensenb, Berit Eikaa
a
Centre for Medical Education, Faculty of Health Sciences, University of Aarhus, Aarhus N, Denmark
b
Department of Prehospital Medical Services, Central Region Denmark, Aarhus N, Denmark
a r t i c l e i n f o a b s t r a c t
Article history:
Background: The importance of circulation during cardiopulmonary resuscitation has led to efforts to
Received 22 August 2009
decrease time without chest compressions ( no-flow time ). The no-flow time from the interruption of
Received in revised form
chest compressions until defibrillation is referred to as the  pre-shock pause . A shorter pre-shock pause
12 December 2009
increases the chance of successful defibrillation. It is unclear whether drug administration affects the
Accepted 30 December 2009
length of the pre-shock pause. Our study compares pre-shock pause with and without drug administration
in a full-scale simulation.
Keywords:
Methods: This was an observational study in an ambulance including 72 junior physicians and a cardiac
Information overload
arrest scenario. Data were extracted by reviewing video recordings of the resuscitation. Sequences includ-
Advanced life support (ALS)
ing defibrillation and/or drug administration were identified and assigned to one out of four categories:
Ambulance
Defibrillation only (DC-only) and drug administration just prior to defibrillation (Drug + DC) for which
Cardiac arrest
Cardiac massage the pre-shock pause was calculated, and drug administration alone (Drug-only) for which pre-drug time
Cardiopulmonary resuscitation (CPR)
was calculated.
Chest compression
Results: DC-only sequences were identified in 68/72 simulations, Drug + DC in 24/72, and Drug-only in
Circulation
33/72. Median pre-shock pauses were 18 s (DC-only) and 32 (Drug + DC), and median pre-drug pause 6. The
Defibrillation
variation between pauses was statistically significant (p 0.001). DC-only and Drug + DC sequences was
Education
found in 22/72 simulations. A statistically significant difference of 8 s was found between the median pre-
Emergency treatment
shock pauses: 17 s (DC-only) and 25 (Drug + DC) (p 0.001). For un-paired observations, the pre-shock
Guidelines
pause increased with 78% and for paired observations 47%.
Manikin
Conclusions: Drug administration prior to defibrillation was associated with significant increases in pre-
Resuscitation
Transport shock pauses in this full-scale simulation study.
Drugs
© 2010 Elsevier Ireland Ltd. All rights reserved.
Pharmacokinetics
Crisis resource management
1. Background on ILCOR recommendations, the European Resuscitation Council
(ERC) and the American Heart Association (AHA) now recommend
The critical importance of sufficient circulation during car- a compression ventilation ratio of 30:2 (rather than previously
diopulmonary resuscitation has led to increased efforts to decrease 15:1), and only one defibrillation between each 2-min series of
no-flow time.1 5 No-flow time refers to the period during car- basic life support (BLS) (rather than three).6 12 Furthermore, the
diac arrest without sufficient circulation, and is equivalent to AHA recently added a  hands-only CPR recommendation to their
the time without chest compressions. Several initiatives have guidelines.13
been taken to reduce no-flow time (also referred to as  hands- During advanced life support (ALS), BLS is interrupted every
off time ) in the treatment recommendations published by the 2 min to assess the cardiac rhythm and to guide therapy. For
International Liaison Committee on Resuscitation (ILCOR). Based non-perfusing tachy-arrhythmias (e.g., ventricular fibrillation (VF)
and pulseless ventricular tachycardia), therapy includes defibrilla-
tion alone or drug administration and defibrillation together.8,9,12
Defibrillation and drug administration are potentially life saving

A Spanish translated version of the abstract of this article appears as Appendix
actions, but they may also increase hands-off time if interrupting
in the final online version at doi:10.1016/j.resuscitation.2009.12.024.
chest compressions. Thus, it is necessary to weigh the disadvan-
"
Corresponding author at: INCUBA Science Park, Skejby, Brendstrupgaardsvej
tages of interrupting chest compressions against the advantages of
102, DK-8200 Aarhus N, Denmark. Tel.: [phone].
other actions.
E-mail addresses: [e-mail], [e-mail] (C.B. HÅ‚yer).
0300-9572/$  see front matter © 2010 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.resuscitation.2009.12.024
344 C.B. HÅ‚yer et al. / Resuscitation 81 (2010) 343 347
tice. Therefore, the aim of our study was to compare the pre-shock
pause with and without drug administration in a full-scale simula-
tion study.
2. Methods
The data used in this paper originated from our previous
observational study of junior physicians skills and behaviour dur-
ing simulated resuscitation.23 The study included 72 participants
who had graduated within 5 years and were working in internal
medicine departments with acute admissions. Participation was
voluntary, informed consent was obtained, and data were kept
confidential.
The simulations took place in a working ambulance with gen-
uine equipment and personnel (a paramedic and an emergency
medical technician). A computer-controlled manikin with simu-
lated cardiac rhythm, respiration, peripheral blood saturation, and
blood pressure, was placed on the stretcher (ResusciAnne Simulator
& Laerdal PC SkillReporting System, Laerdal Medical, Norway). Sup-
Fig. 1. Comparison of advanced life support (ALS) guidelines. The figure shows the
interpretation of ALS guidelines from the American Heart Association (AHA), the
plemental oxygen, intravenous accesses, electrocardiogram, and
European Resuscitation Council (ERC), and the Norwegian Resuscitation Council
self-adhesive defibrillation pads were established in advance.
(NRC).
The scenario involved a patient case with acute coronary
syndrome in need of percutaneous coronary intervention at a
specialised cardiac department. During transfer, the patient expe-
The no-flow time that starts from the interruption of chest
rienced a ventricular fibrillation (VF) cardiac arrest that was
compressions until the delivery of DC-shock is referred to as the
refractory to treatment for 5 min. In the following 3 min, defibril-
pre-shock pause. A shorter pre-shock pause increases the chance
lation would invoke ROSC. If not defibrillated within these 3 min,
for successful defibrillation and, accordingly, the return of sponta-
ROSC would appear no later than 8 min after the onset of VF. In
neous circulation (ROSC).14 17 Current recommendations state that
all simulations, the used monitor/defibrillator, LIFEPAK-12 (Physio-
pre-shock pauses should not exceed 10 s.18
Control, USA) was of the same type and set to manual mode before
The recommended timing for drug administration during ALS
initiating the simulation (in contrast to advisory mode).
differs between authorities, including the ERC, AHA, and the Nor-
wegian Resuscitation Council (NRC) (Fig. 1). The ERC and AHA
2.1. Data and statistics
agree that drugs should be administered just before delivery of
DC-shock9,12; however, this apparent agreement encompasses two
different interpretations. As a safety precaution, the ERC dis- Video recordings from a digital surveillance camera mounted
in the ambulance documented all simulations, and recordings
courages touching the patient while charging the defibrillator7,9;
were continuously time-stamped by the camera with a built-in
consequently, drug administration is to occur prior to charging the
on-screen digital clock. Calculation of intra- and inter-observer
defibrillator. In contrast, the AHA recommends continued chest
variability was done by random selection of three simulations that
compressions  and therefore drug administration  during the
charge phase.12 Yet another recommendation adds to the discor- were reviewed (in their full length) twice by two independent per-
sons (a physician and a medical student) and by the first author of
dance as the NRC recommend drug administration happens 60 s
this paper. The inter- and intra-observer coefficients were calcu-
after defibrillation, i.e., during the following cycle of BLS.19
lated using Stata/IC 10.1 (StataCorp, USA).
The rationale for delaying drug administration to 60 s after
defibrillation is dual. One part is pharmacokinetic and patho- Events identified in the video recordings included time to onset
of VF, all ventilations, start/stop of all series of chest compressions
physiological aspects of resuscitation; the other is cognitive
(including the number of chest compressions in each series), and
considerations about complexity of guidelines.
time for defibrillation and drug administration (Fig. 2).
The pharmacokinetic and pathophysiological arguments against
Sequences that included defibrillation and/or drug administra-
administering adrenaline just prior to defibrillation are, according
tion were identified in the dataset and assigned to one out of
to the NRC, that myocardial perfusion ceases almost immediately
four categories: DC-only, Drug + DC, Drug-only, and Drug-during
when chest compressions are interrupted,20,21 and that it takes up
(Table 1). If a pause in chest compressions included several defibril-
to 90 s to restore adequate perfusion of the heart after resuming
lations and/or several drug administrations or if in correct numbers
chest compressions.20,21 Thus, adrenaline injected into a peripheral
but in the wrong order, they were excluded.
vein only reaches its peak concentration after 90 150 s.22 As such,
there may be no immediate benefit from adrenaline injected just
prior to defibrillation.9
Table 1
The cognitive considerations about guideline complexity can be
Defibrillations and/or drug administrations were assigned to one out of the four
summarised to questioning if the focus on drug administration may
categories listed in the table. The table shows the actions included in each of the
shift focus away from defibrillation and thereby increase the pre-
four categories.
shock pause.19
Category Action
In theory, drug administration in itself should not significantly
Chest compressions Drug administration Defibrillation
influence the pre-shock pause since teams should use the BLS cycles
to prepare drugs for subsequent injection.9 Further, intravenous
DC-only Interrupted No Yes
injection of 1 ml (as in the case for 1 mg adrenaline) should be very Drug + DC Interrupted Yes Yes
Drug-only Interrupted Yes No
quick, as should the mandatory saline flush9; however, it remains
Drug-during Ongoing Yes No
unclear if drug administration affects the pre-shock pause in prac-
C.B. HÅ‚yer et al. / Resuscitation 81 (2010) 343 347 345
Fig. 2. Example of registrations. The figure illustrates a segment of a simulation exercise. The diagonal numbers represent net time in the simulation, starting with the debut
of the ventricular fibrillation at the time 00:00:00 (hours:minutes:seconds).
For the two categories including defibrillation (DC-only and
Drug + DC), the pre-shock pause was calculated (Fig. 3). In order to
compare sequences including defibrillation and sequences includ-
ing drug administration, but not defibrillation, the term  pre-drug
pause was introduced (Fig. 3): The pre-drug pause describes the
hands-off time from chest compressions are interrupted until drugs
are administered and thus represent an equivalent to the pre-shock
pause calculated in events including defibrillation. Time used for
drug administration during chest compressions (Drug-during) was
by definition zero.
In order to prevent results from being skewed by paired obser-
vations, the median value in each category (DC-only, Drug + DC,
Fig. 4. Time in seconds since interruption of chest compressions to DC-shock
and Drug-only) was calculated for each simulation: If a simulation
(DC-only (n = 68) and Drug DC (n = 24)) or drug injection (Drug-only (n = 33)),
included more than one case in a single category, e.g. three cases
respectively. The three sequences depicted (DC-only, Drug + DC, and Drug-only) did
not necessarily happen in each simulation; consequently the numbers in each group
of defibrillation alone (DC-only), the median duration of the three
does not add up to the 72 simulations described. The differences were statistically
pre-shock pauses was calculated and used for further analysis.
significant (one-way analysis of variances, p 0.001). Values depicted are medians,
Two comparisons were done: First, the duration of the median
upper/lower quartiles, 5 95 percentiles (whiskers), and outliers (dots).
pauses in the three categories (DC-only, Drug + DC, and Drug-only)
were compared using one-way analysis of variances. Second, intra-
individual comparison between the pre-shock pause in DC-only
and Drug + DC sequences was calculated for all simulations includ-
ing both DC-only and Drug + DC sequences using paired t-test. Both
comparisons were made using GraphPad Prism 5.02 (GraphPad
Software, USA). All time values are given in seconds as median
(lower; upper quartiles) [minimum maximum].
3. Results
Almost all of the 72 simulations (68 (94%)) included DC-only
sequences, while only 24 (33%) included Drug + DC sequences.
Drug-only sequences were found in 33 (46%) of the simulations
(Fig. 4). Furthermore, 24 (33%) simulations included drug admin-
istration during ongoing chest compressions (Drug-during). The
three sequences (DC-only, Drug + DC, and Drug-only) did not nec-
essarily happen in each simulation; consequently, the numbers in
each group do not add up to the 72 simulations described
In the simulations including DC-only sequences (n = 68), the
median pre-shock pause for DC-only sequences was 18 s (14; 23)
Fig. 3. Illustration of pauses and categories used in analysis. The upper part of the fig- [1 38]. In the 24 simulations including Drug + DC sequences the
ure illustrates two different pre-shock pauses: upper left illustrates a sequence with
median pre-shock pause for Drug + DC sequences was 32 s (21; 36)
only defibrillation (DC-only) and upper right a sequence with drug administration
[12 85]. Drug administration alone happened in 33 simulations
and defibrillation (Drug + DC). The lower left part of the figure shows a sequence of
and had a median pre-drug pause of 6 s (3; 12) [1 41]. The difference
a pre-shock pause, when only drugs are administered instead of a DC-shock, that is,
between the three groups was statistically significant (one-way
a pre-drug pause (Drug-only). The lower right of the figure illustrates drug injection
during chest compressions (Drug-during). analysis of variances, p 0.001) (Fig. 4). The relative increase in
346 C.B. HÅ‚yer et al. / Resuscitation 81 (2010) 343 347
pre-shock pause. Information overload, i.e., a situation with more
incoming stimuli than the physician has cognitive abilities to pro-
cess, may be one explanation.27 30
Drug administration is not only a matter of emptying the
syringe, but also entails other actions, such as flushing with saline
(10 20 ml) and raising the limb in the air for 10 20 s.9,12 Thus,
after deciding on appropriate drug administration, the physician
almost instantaneously has to estimate if this (injection, flush-
ing, raising the limb, etc.) will cause the patient to be left without
chest compressions for more than 10 s, and, in that case omit drug
administration.9,12,18
To the experienced physician, such actions may be implicit,
Fig. 5. Pre-shock pause. The figure illustrates the pre-shock pause in the DC-
only and the Drug DC-groups for the 22 simulations that included both type of but to the less experienced physician substantial efforts may be
sequences. The difference in pre-shock pause was statistically significant (paired
necessary in order to recall these details. Further increasing the
t-test, p 0.001). Values depicted are medians, upper/lower quartiles, 5 95 per-
number of information units to be processed within the very short
centiles (whiskers), and outliers (dots).
time frame from chest compressions are interrupted to defibrilla-
tion is supposed to be done, constitutes the core concept of  safe
pre-shock pause between DC-only and Drug + DC was 78% (14/18).
defibrillation . Safe defibrillation is advocated by the ERC, which
A total of 22 (31%) of the simulations included both DC-only
discourages touching the patient while charging the defibrillator
and Drug + DC sequences, which made it possible to compare intra-
(18, pp. 82 83); however, the ERC also recommends administering
individual differences between the pre-shock pause in DC-only
drugs while charging the defibrillator as a method of shortening
and Drug + DC sequences. In those 22 simulations, the median
the pre-shock pause.31
pre-shock pause when only defibrillation was done (DC-only)
In our study we observed, that when drugs were administered
was found to be 17 s (15; 22) [6; 38] compared to 25 s (21;
apart from defibrillation, but during a pause in chest compressions,
36) [12 51] when drugs were administered prior to defibrillation
the median pre-drug pause was 6 s. Thus, performing one instead
(Drug + DC) (Fig. 5). The difference in means was statistically sig-
of multiple procedures can be associated with shorter pauses in
nificant (p 0.001, paired t-test).
chest compressions. This supports our concerns about informa-
Only two physicians performed the recommended flushing
tion overload under the current guidelines, a question also raised
with saline after drug administration. Raising the limb after drug
by Meertens et al.32 who suggested that drug administration just
injection9 happened only once.
before defibrillation may divert focus from defibrillation to drug
The intra-observer variability coefficients were 0.9966, 0.9981,
administration, thereby prolonging the pre-shock pause.
and 0.9971, respectively, and the inter-observer variability coeffi-
If the onset of the effects of adrenaline does not occur until
cients were 0.9897, 0.9913, and 0.9906, respectively.
minutes after administration,9,20 22 it should be carefully con-
sidered if this equals that the timing of administration could
4. Discussion be changed without negative consequences. It could be argued
that drug administration during BLS is merely relocating the time
In this observational, full-scale cardiac arrest simulation study, without chest compressions. A counter-argument is the immense
we found an increase in the median pre-shock pause when impact that the length of the pre-shock pause has on the chance for
drugs were administered prior to defibrillation (25 s) compared successful defibrillation.
to defibrillation alone (17 s) in 22 simulations that included both In our study, we saw 24 simulations that included drug
sequences. This 8-s difference in medians is equivalent to a 47% administration during ongoing chest compressions (Drug-during).
relative increase (8/17) in the pre-shock pause. Further, compari- One interpretation is that the physicians intuitively prioritised
son of all 72 simulations revealed a relative increase in pre-shock chest compressions higher than drug administration and there-
pause between DC-only and Drug + DC at 78% (14/18). fore chose to administer drugs during ongoing chest compressions
This is an important finding given that a prospective, multi- instead. Another, of course, would be that they did not know
centre, observational study of cardiac arrest showed survival to be guidelines.
71% if the pre-shock pause was within 10.2 20.0 s, but only 60% if A limitation in this study is that performance during simulation
the it was within 21.1 30 s.14 is not equal to performance in real life. A manikin is not able to sim-
Pre-shock pauses shorter than 10 s might not be attainable in all ulate all vital signs, skin pallor and temperature are just some of the
settings. We found pre-shock pauses of 17 and 25 s in the Drug-only signs missing as well as it is clear that human life is not at stake.33
and Drug + DC groups, respectively, and our findings are supported The link between real life and the results presented in this paper is
by those of other studies that found median pre-shock pauses of that the simulations were held within the actual context. The setup
15 s,1 15.3 s,14 11 s,24 and 17 s.25 was a genuine ambulance, and the fellow players in the simulation
The findings of pre-shock pauses longer than 10 s need attention. were real ambulance crews. The drugs, syringes, needles, and fluids
One explanation is that the charging time of the defibrillator pro- were real. Naturally, the manikin was not real. However, the chest
longs the interruption of chest compressions. This will be the case if moved, the pulse was palpable  and vivid communications took
guidelines that discourage touching the patient during charging the place between the physicians and the simulated patient through
defibrillator are followed (ERC and NRC guidelines, Fig. 1). Another the first minutes of the simulations.
explanation for longer pre-shock pauses may be inappropriately Life-like surroundings and a patient case representing a frequent
designed equipment.26 challenge to the junior physician constitute a major strength to this
A third and perhaps more important explanation may be that study. In the light of this, and the fact that simplified guidelines have
the less experienced physician needs more time than the more been shown to increase guideline adherence,34 36 it seems reason-
experienced to assess the cardiac rhythm before deciding whether able to carefully consider if it is possible to reduce the number of
defibrillation is appropriate. actions to be performed during the pre-shock pause, thereby reduc-
In this study, we observed that performing two resuscitation ing information overload. In order to further elucidate this point, it
actions instead of one correlates with a significant increase in will also be necessary to perform studies that focus on only single
C.B. HÅ‚yer et al. / Resuscitation 81 (2010) 343 347 347
actions in order to decide whether the action by itself has latent 10. 2005 American Heart Association Guidelines for cardiopulmonary resuscita-
tion and emergency cardiovascular care: adult basic life support. Circulation
weaknesses.
2005;112:IV-19 34.
11. 2005 American Heart Association Guidelines for cardiopulmonary resuscitation
5. Conclusions and emergency cardiovascular care: electrical therapies: automated externbal
defibrillation, defibrillation, cardioversion, and pacing. Circulation 2005;112:IV-
35 6.
Observations from our simulation study show that the pre-
12. 2005 American Heart Association Guidelines for cardiopulmonary resuscitation
shock pause is considerably longer in cases that include intravenous and emergency cardiovascular care: management of cardiac arrest. Circulation
2005;112:IV-58 6.
drug administration prior to defibrillation (25 s) compared to cases
13. Sayre MR, Berg RA, Cave DM, Page RL, Potts J, White RD. Hands-only
that include only defibrillation (17 s). Considering the recom-
(compression-only) cardiopulmonary resuscitation: a call to action for
mended maximum 10-s delay, both pauses were too long; however,
bystander response to adults who experience out-of-hospital sudden car-
diac arrest: a science advisory for the public from the American Heart
the delay related to drug administration is noteworthy as the pre-
Association Emergency Cardiovascular Care Committee. Circulation 2008;117:
shock pause represents time without sufficient circulation.
2162 7.
Our results suggest that altering the resuscitation sequence from
14. Edelson DP, Abella BS, Kramer-Johansen J, et al. Effects of compression depth
and pre-shock pauses predict defibrillation failure during cardiac arrest. Resus-
administering drugs before defibrillation to after defibrillation may
citation 2006;71:137 45.
improve the outcome of resuscitation. As Kern et al. concluded
15. Berg RA, Hilwig RW, Kern KB, Sanders AB, Xavier LC, Ewy GA. Automated external
in 2002,  Any technique that minimizes lengthy pauses in chest
defibrillation versus manual defibrillation for prolonged ventricular fibrillation:
compressions [...] should be given serious consideration .17 lethal delays of chest compressions before and after countershocks. Ann Emerg
Med 2003;42:458 67.
16. Yu T, Weil MH, Tang W, et al. Adverse outcomes of interrupted precordial com-
Conflict of interest statement
pression during automated defibrillation. Circulation 2002;106:368 72.
17. Kern KB, Hilwig RW, Berg RA, Sanders AB, Ewy GA. Importance of contin-
uous chest compressions during cardiopulmonary resuscitation: improved
None to declare.
outcome during a simulated single lay-rescuer scenario. Circulation 2002;105:
645 9.
Acknowledgements 18. European Resuscitation Council Advanced Life Support Course Manual, 5th edi-
tion. Antwerp, Belgium, European Resuscitation Council; 2006.
19. Lexow K, Sunde K. Why Norwegian 2005 guidelines differs slightly from the ERC
The authors wish to extend our greatest thanks to the enthu-
guidelines. Resuscitation 2007;72:490 2.
siastic ambulance crews for participating in the simulations and 20. Steen S, Liao Q, Pierre L, Paskevicius A, Sjoberg T. The critical importance of
minimal delay between chest compressions and subsequent defibrillation: a
to Peter G. Brindley MD, FRCPC, Division of Critical Care Medicine,
haemodynamic explanation. Resuscitation 2003;58:249 58.
University of Alberta, Edmonton, Alberta Q1, Canada, for critical
21. Sato Y, Weil MH, Sun S, et al. Adverse effects of interrupting precordial
review of the manuscript, as well as Anthony J. Handley MD, FRCP, compression during cardiopulmonary resuscitation. Crit Care Med 1997;25:
733 6.
Colchester, England. Funding sources: This simulation study was
22. Pytte M, Kramer-Johansen J, Eilevstjonn J, et al. Haemodynamic effects of
supported by a grant by the County of Aarhus, Denmark. Falck,
adrenaline (epinephrine) depend on chest compression quality during car-
Denmark sponsored ambulances and personnel.
diopulmonary resuscitation in pigs. Resuscitation 2006;71:369 78.
23. HÅ‚yer CB, Christensen EF, Eika B. Junior physician skill and behaviour in resus-
citation: a simulation study. Resuscitation 2009;80:244 8.
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