Ex-vivo and live animal models are equally effective training for the management of a penetrating cardiac injury
Izawa et al. World Journal of Emergency Surgery
Ex-vivo and live animal models are equally effective training for the management of a penetrating cardiac injury
Yoshimitsu Izawa 0 1
Shuji Hishikawa 0 1 2
Tomohiro Muronoi 0
Keisuke Yamashita 0
Hiroyuki Maruyama 2
Masayuki Suzukawa 0
Alan Kawarai Lefor 1 2
0 Department of Emergency and Critical Care Medicine, Jichi Medical University , 3311-1 Yakushiji, Shimotsukeshi, Tochigiken 329-0498 , Japan
1 Center of Development for Advanced Medical Technology, Jichi Medical University , 3311-1 Yakushiji, Shimotsukeshi, Tochigiken 329-0498 , Japan
2 Department of Digestive Surgery, Jichi Medical University , 3311-1 Yakushiji, Shimotsukeshi, Tochigiken 329-0498 , Japan
Background: Live tissue models are considered the most useful simulation for training in the management for hemostasis of penetrating injuries. However, these models are expensive, with limited opportunities for repetitive training. Ex-vivo models using tissue and a fluid pump are less expensive, allow repetitive training and respect ethical principles in animal research. The purpose of this study is to objectively evaluate the effectiveness of ex-vivo training with a pump, compared to live animal model training. Staff surgeons and residents were divided into live tissue training and ex-vivo training groups. Training in the management of a penetrating cardiac injury was conducted for each group, separately. One week later, all participants were formally evaluated in the management of a penetrating cardiac injury in a live animal. Results: There are no differences between the two groups regarding average years of experience or previous trauma surgery experience. All participants achieved hemostasis, with no difference between the two groups in the Global Rating Scale score (ex-vivo: 25.2 ± 6.3, live: 24.7 ± 6.3, p = 0.646), blood loss (1.6 ± 0.7, 2.0 ± 0.6, p = 0.051), checklist score (3.7 ± 0.6, 3.6 ± 0.9, p = 0.189), or time required for repair (101 s ± 31, 107 s ± 15, p = 0.163), except overall evaluation (3.8 ± 0.9, 3.4 ± 0.9, p = 0.037). The internal consistency reliability and inter-rater reliability in the Global Rating Scale were excellent (0.966 and 0.953 / 0.719 and 0.784, respectively), and for the checklist were moderate (0.570 and 0.636 / 0.651 and 0.607, respectively). The validity is rated good for both the Global Rating Scale (Residents: 21.7 ± 5.6, Staff: 28.9 ± 4.7, p = 0.000) and checklist (Residents: 3.4 ± 0.9, Staff Surgeons: 3.9 ± 0. 3, p = 0.003). The results of self-assessment questionnaires were similarly high (4.2-4.9) with scores in selfefficacy increased after training (pre: 1.7 ± 0.8, post: 3.2 ± 1.0, p = 0.000 in ex-vivo, pre: 1.9 ± 1.0, post: 3.7 ± 0.7, p = 0.000 in live). Scores comparing pre-training and post-evaluation (pre: 1.7 ± 0.8, post: 3.7 ± 0.9, p = 0.000 in ex-vivo, pre: 1.9 ± 1.0, post: 3.8 ± 0.7, p = 0.000 in live) were increased. Conclusion: Training with an ex-vivo model and live tissue training are similar for the management of a penetrating cardiac injury, with increased self-efficacy of participants in both groups. The ex-vivo model is useful to learn hemostatic skills in trauma surgery.
Trauma surgery; Ex-vivo training; Surgical education; Simulation; Objective Structured Assessment of Technical Skills; Self-efficacy
Simulation training is essential for learning a variety of
skills in medical training. Concerns for patient safety
and super-specialization have increased the need for
simulation-based training. Simulation training for
hemostasis in trauma surgery is especially desired
because hemostasis is critical to save severely injured
patients and there are limited opportunities for surgeons
to learn the skills needed to treat traumatically injured
patients in clinical practice [1, 2]. The number of
surgical procedures performed by trainees has been
decreasing with advancements in non-operative management
. Various simulation courses are conducted around
the world in part to make up for limited real-life
Live tissue training is considered by some to be the
most useful simulation for training in the hemostasis
of traumatic injuries [6, 7]. However, these programs
are expensive, repetitive training is impractical, and
ethical issues regarding the use of live animals have
gained intense focus . These factors limit the
conduct of live tissue training programs. Other methods,
such as cadaver training, virtual reality and bench
model training, are less suitable for training in
hemostatic skills because of decreased reality or a
total lack of bleeding [6, 7].
Ex-vivo tissue can be used for simulation training for
technical skills [8, 9]. It is generally considered to have
mid-level fidelity, is financially reasonable and conducive
to repetitive training. We previously conducted a pilot
study in the use of a circulation pump for ex-vivo
training in trauma surgery, with subjective evaluation .
The pump mimics circulation, and appears similar to
live tissue. However, objective assessment of this method
has not been conducted.
The purpose of this study is to objectively evaluate the
effectiveness of ex-vivo training with a pump, compared
to live tissue training, for the management of a
penetrating cardiac injury.
Institutional Animal Experiment Committee approval
was obtained before beginning this study. This study
was conducted in the Center for Development of
Advanced Medical Technology (CDAMtec) at Jichi
Staff surgeons and residents at Jichi Medical University
Hospital took part in this study. This program was the
first time any of the participants managed a penetrating
cardiac injury. Participants were surveyed regarding their
level of training, years of experience and details of their
previous trauma surgery experience.
This is a comparative study comparing ex-vivo training
and live tissue training (Fig. 1). Participants were divided
into two groups, an ex-vivo training group and a live
tissue training group. Participants were randomly assigned
based on their last name. However, there were a few
changes because of emergency clinical responsibilities
on the day of the training. After completing a
pretraining questionnaire (Fig. 2) and obtaining informed
consent about participation in the study, participants
were trained by experienced trauma surgeons to achieve
hemostasis of a penetrating cardiac wound and then
repair the wound with explanations and demonstrations.
Participants then practiced achieving hemostasis of a
one centimeter cardiac injury with help from the
instructor. The ex-vivo group did this using an ex-vivo
tissue model, and the live group performed this on a live,
anesthetized pig. After the training, a post-training
questionnaire was completed (Fig. 3).
One week after the training session, all participants
managed a standard one centimeter penetrating cardiac
wound in a live animal using the skills acquired during
the previous training session. Each participant managed
the wound individually, and was assessed with an
Objective Structured Assessment of Technical Skills
(OSATS) instrument. After the evaluation, a
postevaluation survey form was completed by the
participants (Fig. 3).
Ex-vivo training session (Fig. 4)
Ex-vivo training was performed using porcine hearts
from animals used in other experiments or training. The
ex-vivo hearts were harvested and frozen, the frozen
organs thawed and connected to a circulation pump before
the training session. During the training, a one
centimeter penetrating wound was made in the right
ventricle. Participants learned how to stop bleeding initially
with digital pressure, and then repair the injury with
direct suture, under the guidance of an instructor.
Live tissue training session (Fig. 5)
Live tissue training was performed with pigs (Crossbred
KCG or Mexican hairless miniature pig, approximately
30–40 kg under general anesthesia (Sevoflurane 2–5 %).
After performing a median sternotomy and incising the
pericardium, a penetrating injury about one centimeter
long was made in the right ventricle by the instructor.
Participants achieved hemostasis using digital pressure
and then repaired the injury with direct suture.
Participants were evaluated by direct observation in their
management of a cardiac injury in the live animal model
conducted one week after the training session. The
StaffSurgeons (n=14) and Residents (n=17)
Live tissue group (n=15)
Staff (n=7) and Residents (n=8)
Ex-vivo group (n=16)
Staff (n=7) and Residents (n=9)
Questionnaire before trainingand Informed consent
Live tissue training
Questionnaire after training
Evaluationwith live tissue model
(Global Rating Scale, Checklist, Time required to repair, with four evaluators)
Questionnaire after evaluation
Fig. 1 Study flowchart
animals were the same type and size used in the training
session. The evaluation session was conducted similarly
for all participants. Four evaluators assessed each
participant, and completed an evaluation form using the
OSATS instrument. The time required to repair the
injury by each of the participants was recorded. The
evaluators were blinded to whether participants had
undergone training with live tissue or an ex-vivo
There were six evaluators in total, and four of the six
assessed the performance of each participant using the
OSATS. Two of the six were experienced surgeons with
more than 25y experience in acute care surgery. Two
were board certified surgeons and others included an
experienced veterinarian, and an experienced veterinary
technician with more than 30 years of experience in
veterinary care and surgery.
OSATS is widely accepted as a reliable and valid
evaluative tool for simulation [10, 11]. This OSATS
instrument included a Global Rating Scale and
checklist. The Global Rating Scale includes nine items
(Fig. 6). Item 1–7 are standard, and we added two
items including, “amount of hemorrhage” and “overall
evaluation”. In eight of the nine items, a five-point
Likert scale (1 = poor ~ 5 = excellent) was used. One
item, “amount of hemorrhage”, was a three-point
qualitative scale (1 = little, 2 = intermediate and 3 = a
lot). The checklist included four Yes/No questions
(Fig. 7). The questions on the checklist are
taskspecific and more concrete, different from the global
Reliability and validity of the OSATS were evaluated
in this study. The internal consistency reliability was
analyzed by Cronbach’s α. The inter-rater reliability
was analyzed by inter-class correlation. The validity
was evaluated by comparing the outcome of the
Global Rating Scale (as the sum of the seven
component scores, each score range 1–5, overall range 7–35)
and checklist score (4 items scored 0 or 1, overall range
0–4) of staff surgeons and residents, using a sum of the
Participants completed questionnaires at three
separate time points: pre-training post-training and
postevaluation. The questionnaires utilized a five point Likert
scale (1 = poor ~ 5 = excellent) and included an
assessment of self-efficacy (self-confidence) (Figs. 2 and 3).
Data were analyzed with SPSS (IBM, Armonk NY)
version 22.0. Continuous variables are presented as means
with standard deviations. Mann Whitney’s U test is used
for continuous variables because most data were
nonnormal distributions. Wilcoxon signed-rank test is used
for paired continuous variables. Inter-class correlation is
Fig. 2 Pre-training questionnaire
used for the assessment of inter-rater reliability.
Statistical significance was set at a P-value less than .05.
There are no statistical differences between the two
study groups, although the number of years after
medical school graduation and trauma surgery experience in
the ex-vivo training group was slightly higher than in
the live tissue group (Table 1).
Evaluation of management of a penetrating cardiac injury
All participants were able to achieve hemostasis. Table 2
shows the results of the Global Rating Scale, amount of
hemorrhage, overall evaluation, checklist and time
required to repair. There was a significant difference in
the overall evaluation between the two study groups,
with the ex-vivo group being significantly higher. The
amount of hemorrhage before achieving hemostasis was
higher in the live tissue trained group, but this difference
did not quite reach statistical significance.
Table 3 shows the internal consistency reliability and
inter-rater reliability for both the Global Rating Scale
and checklist. The internal consistency reliability scores
were better in both groups than the inter-rater reliability,
but the results were reasonable for all four evaluations.
Although two instructors could not participate in all
evaluations, two different instructors served as
substitutes, and the inter-rater reliability scores remained
Table 4 shows the validity by comparing the Global
Rating Scale and checklist scores between residents and
staff surgeons. There is a significant difference between
residents and staff surgeons, with the validity for both
rating scales significantly greater for staff surgeons than
Tables 5 and 6 show the results of pre-training,
posttraining and post-evaluation questionnaires. Table 5
Fig. 3 Post-training and post-evaluation questionnaire
Fig. 4 Ex-vivo tissue: cardiac injury
Fig. 5 Live tissue training: cardiac injury
Fig. 6 Global Rating Scale score sheet, including evaluations of
amount of hemorrhage and overall evaluation
Fig. 7 Evaluation checklist
comparing the two study groups after training and after
the evaluation session. There was a small, but not
statistically significant difference in the satisfaction scores
after the training session, but this difference did not
appear after the evaluation session.
Table 7 shows the assessment of self-confidence
comparing the results at all three time points, pre-training,
post-training and post evaluation. Confidence levels are
similar in the two study groups at the pre-training time
point, with both groups showing significantly more
confidence both post-training and post-evaluation. Comparing
post-evaluation to post-training shows that the two study
groups had similar confidence levels after the evaluation
session, but that the live tissue group felt more confident
Interestingly, after the training session, the live tissue
group had significantly more self-confidence (score 3.7)
than the ex-vivo (score 3.2, p < .05) trained group.
However, after the evaluation session, while the self-confidence
of both groups was significantly greater compared to
pretraining, there was no longer a difference in the
selfconfidence level of the two groups.
shows that the two study groups had no differences in
their subjective self-assessment before the training.
Table 6 shows no differences in subjective evaluations
We conducted training using an ex-vivo model with a
pump, and compared it with use of a live animal model
Table 1 Characteristics of study participants: years after medical school graduation and previous experience in trauma surgery
Study group (n = number of participants)
Years after medical school graduation (mean years (Standard Deviation))
Prior experience in chest and abdominal trauma surgery (mean number of procedures
to teach the management of penetrating cardiac injuries.
After training, all participants were objectively evaluated
in their management of a penetrating cardiac injury.
All participants were able to achieve hemostasis at
the injury site on the surface of the right ventricle.
Objective assessment revealed that ex-vivo training
was as effective as live tissue training, based on the
evaluation conducted. The reliability and validity of
the OSATS instrument were good. Participant
responses to subjective questionnaires were positive and
the level of self-efficacy increased.
Live tissue training is considered by some to be the
most effective way to learn hemostatic skills for
trauma surgery [6, 7]. Other training models, such as
cadaver training, bench model training, or virtual
reality training, do not have active blood circulation
to mimic live tissue training. However, the ex-vivo
system used in this study simulates active bleeding
with an external pump which facilitates learning
hemostatic procedures in a more realistic
environment without a live animal .
Ethical issues regarding the use of experimental
animals are also important  and ex-vivo training models
are a good response to these ethical issues. Burch and
Russel proposed the 3R’s for animal ethics ,
including Reduction, Replacement and Refinement. Although
cadaver training and virtual reality training are beneficial
from an ethical standpoint, these models may not be
suitable for learning hemostatic skills. There are few
Table 2 Global Rating Scale score, amount of hemorrhage,
overall evaluation, checklist and time required to repair
comparing ex-vivo and live tissue groups
Study group (n = number of evaluation forms) Ex-vivo
(n = 64)
Amount of hemorrhage (Range 1–3)
Time required (seconds)a
1.6 (0.7) 2.0 (0.6)
3.8 (0.9) 3.4 (0.9)
3.7 (0.6) 3.6 (0.9)
Scores shown are mean (Standard Deviation), using a 5-point Likert scale
(range 1–5), except hemorrhage which is rated on a 3-point scale (1 = little,
2 = intermediate, 3 = a lot). Checklist scores are range 0–4. Scores shown are
the mean of the four evaluations for all participants
avalues of n shown for time are number of participants
studies comparing the effectiveness of training using
these modalities with training using a live animal
model . The ex-vivo model described here using a
pump provides the opportunity to learn hemostatic
skills in trauma surgery with objective results similar
to training with a live animal and respects the
principles represented by the 3R’s.
Although we did not calculate exact costs in this
study, estimates can be made, based on average
charges at our institution. The direct cost of the
exvivo training is the facility fee and the price of the
sutures. The facility fee is equivalent to the electrical
charges of the circulation pump and the refrigerator
for preservation of the harvested organs, which we
estimate to about US$20 for one session. The sutures
cost about US$50 per session, for a total cost of
about US$70. Live tissue training requires the cost of
the pig, the fee for general anesthesia, and the
sutures. The pig costs about US$1800, and the cost of
anesthesia and the facility fee is about US$300 for a
total cost of about US$2150, with the sutures. While
these are only estimates, the cost of live tissue
training is far greater than ex-vivo training.
One factor which influences the results of the
objective evaluation is the size of the penetrating cardiac
injury. The amount of hemorrhage was not excessive
because the stab wound was just one centimeter long.
It was relatively easy to stop the bleeding. If the
injury were larger, hemostasis would be more difficult
and a greater difference in results may have been
observed. Another important factor is the location of
the wound in the heart, which directly affects the
ease of achieving hemostasis. If the injury was created
in the left atrium, the results may have been different.
Manipulation of an ex-vivo heart during the procedure
Table 3 Internal consistency reliability and inter-rater reliability
of Global Rating Scale and checklist scores
Inter-rater reliability, inter-class Global Rating 0.719
correlation score (Four evaluators) Scale
Global Rating Scale (mean and
standard deviation, sum of seven
scores each score range 1–5,
with overall range 7–35)
Table 4 Validity of Global Rating Scale and checklist scores:
Residents and staff surgeons, four evaluations for each
participant (Mann–Whitney U test)
Group (n = number of evaluation forms) Residents Staff surgeons P value
(n = 68) (n = 56)
21.7 (5.6) 28.9 (4.7) 0.000
Checklist score (range 0–4)
does not have a physiologic effect, limiting the reality of
The overall evaluation of the ex-vivo group was
statistically significantly higher than that of the live tissue
group. Among other evaluation items, such as
amount of hemorrhage and time required to repair,
there was no significant difference between the two
groups, but the mean scores of the ex-vivo group are
higher than those of the live tissue group, though the
characteristics of participants are similar in both
groups. The pressure of the bleeding with the ex-vivo
model, seemed higher than that in the live tissue
model according to some participants , and might
influence the difference in scores. The impression of
higher pressure bleeding with the ex-vivo model
might give participants the impression that repair of
the injury in the live tissue model is easier than
during the training session.
The OSATS instrument had good reliability and
validity and was useful as an evaluation tool. OSATS is
widely used for the evaluation of technical skills in
simulation [10, 11, 13–16]. The internal consistency
reliability and inter-rater reliability analysis of the
Global Rating Scale were high and those for the
checklist were moderate. The validity was evaluated
by comparing the results of residents and staff
surgeons, and a significant difference was observed,
which means that the OSATS used in this study can
identify differences between the study groups. Overall,
the evaluation tools demonstrated that training with
this ex-vivo model is as useful as live tissue training
for the management of a penetrating cardiac injury in
a porcine model simple.
Table 5 Pre-training questionnaire
Study group (n = number of participants) Ex-vivo Live tissue P value
(n = 16) (n = 15)
I am looking forward to this training. 4.4 (0.7) 4.4 (0.8) 0.984
I am interested in trauma surgery.
4.2 (0.9) 4.2 (0.9)
I am confident in performing hemostatic 1.7 (0.8) 1.9 (1.0)
procedures for a cardiac injury.
The subjective evaluations also revealed the
usefulness of training with this ex-vivo model. All responses
to items in the questionnaires showed that the
training was perceived well by the participants.
Selfconfidence in both groups significantly increased after
the training. Self-confidence carries the same meaning
as self-efficacy, which was advocated by Bandura in
1977 . Bandura described that self-efficacy
means”people’s judgments of their capabilities to
organize and execute courses of action required to
attain designated types of performances .” In other
words, it is a belief that one can accomplish a specific
task. Self-efficacy is a very important characteristic for
physicians and surgeons who perform procedures
, particularly in emergency situations [20, 21].
Training with the ex-vivo model significantly
increased the self-efficacy of participants for the repair
of a penetrating cardiac injury. It was of interest that
the increased self-efficacy in the live tissue trained
group compared to the ex-vivo group was not
sustained. Self-efficacy of the two groups was equal after
the evaluation session.
This training is suitable for resident training as it
facilitates repetitive practice. Aboud et al. reported
that cadaver training for placement of an Intra-Aortic
Balloon can be performed with a fluid pump to
mimic circulation , but based on the description
of the procedure, is far more complex than the
system employed in this training program. This ex-vivo
model is reasonable and needs less work to perform
There are some limitations to this study. First,
hemostasis is just one factor in the care of trauma
patients. There are other technical skills required to
save patients with penetrating cardiac injuries, such
as performing a thoracotomy or median sternotomy
to gain access to the injury site. Decision making and
team dynamics for trauma are extremely important in
emergency care. This ex-vivo training does not
provide training for all of the requisite skills. Actual
patient care experience in clinical practice is essential.
There are a number of formal training programs to
teach skills needed in the care of trauma patients.
Second, the physical features of live tissue cannot be
reproduced completely with this ex-vivo model, such
as coagulation and motion of the heart. Third, a
complex injury cannot be simulated using this ex-vivo
model. Management of a single type of injury is a
limitation using this model and this level of fidelity is
suitable for learning basic procedures in trauma
surgery. Fourth, the sample size is somewhat small. As
Table 1 shows, there are differences between the two
groups for time since graduation and prior experience
(number of procedures) in chest and abdominal
Table 6 Post training and post evaluation questionnaires
Study group (n = number of participants)
I am satisfied with this training.
My interest in trauma care has increased.
I am confident to perform hemostatic procedures for a cardiac injury.
I would recommend this training to my colleagues.
Ex-vivo (n = 16)
Live tissue (n = 15)
I obtained new knowledge and skills to achieve hemostasis of a cardiac injury.
I would like to repeat this training.
Scores shown are mean (Standard Deviation), using a 5-point Likert scale (range 1–5). P-values shown are comparing the two study groups, ex-vivo and live tissue
trauma surgery. While the differences are not
significant, a significant difference may be identified with a
larger sample size. Power analysis shows that the
sample size required is 186 (α = 0.05, 1-β = 0.8),
supporting the need for further study of the ex-vivo
Although this ex-vivo model has some limitations,
simulation is an important modality in training for the
care of injured patients. Utilizing this ex-vivo model is
intended to bolster the competence of surgeons, and will
hopefully lead to the increased survival of severely
Ex-vivo training with a pump was as useful as live tissue
training to learn hemostatic techniques for a penetrating
cardiac injury. This training increased the self-efficacy of
participants, and objective scores of results showed no
differences for training with an ex-vivo model or live
tissue. This study supports the use of ex-vivo models for
training in hemostasis, at lower cost and respecting the
principle of 3R’s for animal research.
Table 7 Confidence level comparing pre-training, post-training
(n = 31)
(n = 31)
3.2 (1.0), p = 0.00
(n = 31)
3.7 (0.9), p = 0.00
3.8 (0.7), p = 0.00
Scores shown are mean (Standard Deviation), using a 5-point Likert scale
(range 1–5). P-values shown are comparison with the pre-training questionnaire
for each of the two study groups, while p** compares the live tissue and ex-vivo
group for the post-training evaluation (Wilcoxon signed-rank test)
Some part of this study was presented in the 10th Annual Congress of
Korean Society of Acute Care Surgery, 4th Joint Scientific Congress of KSACS
and JSACS in Busan, Republic of Korea on April 9th, 2016.
This study was supported by the Ministry of Education, Culture, Sports,
Science and Technology (MEXT)-Supported Program for the Strategic
Research Foundation at Private Universities.
YI: Conceived the trial, conducted the training, collected and analyzed data,
prepared the manuscript. SH: Conducted the training, collected data. TM:
Collected the data. KY: Collected the data. HM: Collected data. MS: Conceived
the trial. AKL: Conceived the trial, analyzed the data, preparation of manuscript.
All authors read and approved the final manuscript.
Consent for publication
Ethics approval and consent to participate
The approval of the Institutional Animal Experiment Committee of Jichi
Medical University was obtained before beginning this study (reference
No.14-026 and No.15-233).
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