1. science
2. medicine
3. surgery

Original Paper
Eur Surg Res 2009;43:235–240
DOI: 10.1159/000226219
Received: October 1, 2008
Accepted after revision: April 1, 2009
Published online: June 26, 2009
How to Prevent Lateral Thermal Damage to Tissue
Using the Harmonic Scalpel: Experimental Study
on Pig Small Intestine and Abdominal Wall
Z. Pogorelić a Z. Perko b N. Družijanić b S. Tomić c I. Mrklić c
a
Departments of Pediatric Surgery, b Surgery and c Pathology, Split University Hospital and Split University School
of Medicine, Split, Croatia
Key Words
Harmonic scalpel ⴢ UltraCision ⴢ Thermal injury ⴢ Pig
Abstract
Introduction: When using a harmonic scalpel, the lower
amount of energy that is transduced to the tissue reduces the chance of lateral thermal damage. Methods: Pigs
(weight: 40 kg) were used as the experimental model. After
anesthesia, tissue was coagulated using different application regimens for each group. The width of tissue necrosis
was measured from the point of incision by the harmonic
scalpel. Results: The pig abdominal tissues suffered mean
thermal damage of 0.0825 (output power 3) and 0.2969 mm
(output power 5) when used for 5 s; at 10 s these values were
0.3850 and 0.4793 mm, respectively. In a third experimental
condition, with 10 s of application broken down into 2 parts
of 5 s with a 5-second pause in-between, these values were
0.1876 and 0.2013 mm, respectively. The small intestine tissues suffered mean thermal damage of 0.1302 (output power 3) and 0.1771 mm (output power 5) at a duration of 5 s.
After 10 s of application, these values changed to 0.2655
(output power 3) and 0.2983 mm (output power 5). In the
third condition (activity for 5 s, pause for 5 s, activity for 5 s),
they were 0.2011 and 0.2258 mm, respectively. Conclusion:
Coagulation necrosis is bigger if the usage is continuous
rather than if it is disconnected/reconnected.
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Introduction
In laparoscopic surgery, it is essential to maintain an
operation field with minimal bleeding. High-power ultrasonic dissection systems for cutting and coagulating
tissues have been introduced in both open and endoscopic surgery. Use of the harmonic scalpel for tissue cutting
and hemostasis is a potential alternative to high-frequency current techniques, which can be associated with thermal tissue injuries [1–3]. It is generally assumed that ultrasonic dissection systems disperse less energy to surrounding tissue during activation, and have a reduced
propensity to cause collateral or proximity thermal damage [2, 3].
The harmonic scalpel incorporates piezoelectric transducers that induce a vibration frequency at the functional tip. The generated vibration frequency is between 23.5
and 55 kHz, and the movement of the working part is between 25 and 200 m. At this level, the ultrasonic energy
can cut and coagulate, especially when the functional end
consists of shears where the tissue is compressed between
the sharp and blunt blades [4].
The harmonic scalpel transduces a lower amount of
energy to the tissue than high-frequency current or laser
techniques, resulting in reduced lateral thermal damage
and penetration depth due to lower temperatures (50–
100 ° C) [5]. With the use of high-frequency current techniques, potentially toxic and carcinogenic quantities of
Zenon Pogorelić, MD, PhD
Department of Pediatric Surgery, Split University Hospital
Spinčićeva 1
HR–21 000 Split (Croatia)
Tel. +385 2155 6182, Fax +385 2155 6225, E-Mail zenon@vip.hr
Table 1. Protocol of the experiment and descriptive statistics values for all groups (surface area of thermal tis-
sue damage)
Group
Level
Duration, s
Mean
value, mm
Minimum
value, mm
Maximum
value, mm
Standard
deviation, mm
Abdominal wall
1
3
2
3
4
5
5
6
5
10
5–(5)–5
5
10
5–(5)–5
0.0825
0.3850
0.1876
0.2969
0.4793
0.2013
0.0520
0.2660
0.1140
0.1580
0.2950
0.1240
0.1440
0.4980
0.3070
0.4360
0.6170
0.4430
0.0234
0.0590
0.0652
0.0848
0.1047
0.0810
Small intestine
7
3
8
9
10
5
11
12
5
10
5–(5)–5
5
10
5–(5)–5
0.1302
0.2655
0.2011
0.1771
0.2983
0.2258
0.0910
0.1830
0.1160
0.1330
0.2240
0.1230
0.1730
0.3610
0.3040
0.1771
0.2983
0.2258
0.0238
0.0533
0.0447
0.0198
0.0689
0.0373
CS-14C coagulation shears were used for all groups.
smoke and dust particles are released within a confined
space. Use of the harmonic scalpel significantly reduces
these emissions, although this instrument does cause the
formation of bioaerosols or very small particles in the air
that can be breathed in. Furthermore, bioaerosols can
sustain biologic activity. They can contain live organisms
or cells posing as potentially contaminated material
[5–7].
The harmonic scalpel is used in many different operations, including cholecystectomy [2, 5, 8], appendectomy
[2, 9], fenestration of abdominal cysts [2, 10], reflux
esophagitis procedures [11], large bowel operations [12–
14], stomach resection [15–17], liver resection [18], splenectomy [19], and fenestration of non-parasitic spleen
and liver cysts [20–22]. Recently, the harmonic scalpel
has been used in transanal endoscopic microsurgery [23–
25], endoscopic inguinal and abdominal wall hernia operations [2, 26, 27], and hemorrhoidectomy [28]. The harmonic scalpel is used in head and neck surgery [29] and
gynecology [30], except for abdominal surgery. Recent
studies have shown the possibility of tissue exposition at
higher temperatures and the dependence of lateral thermal damage on instrument application time and output
energy [3, 4]. However, exactly how we should use the
harmonic scalpel to achieve ideal tissue cutting and hemostasis while minimizing thermal damage is currently
unknown. The aim of this study was to determine the effects of different harmonic scalpel application times and
236
Eur Surg Res 2009;43:235–240
levels of output energy on the different tissues. We used
an experimental model of the pig small intestine and fibromuscular layer at the abdominal wall.
Materials and Methods
The high-energy ultrasonic dissection system used was UltraCision (Ethicon Endosurgery, Cincinnati, Ohio, USA), which
consists of a high-frequency vibration generator, a foot switch (or
adapter for hand activation), and a hand piece with cable and various instruments for open and laparoscopic operations. In this
experiment, we used the generator 300 at outputs level 3 and 5, a
hand piece, and flat short coagulation shears CS-14C.
We used 40-kg pigs as the experimental model. One day before
the experiment, the animals were brought into the laboratory for
experimental surgery. For 8 h before the experiment, the animals
were not given any food or water. The animals were anesthetized
using the following sedation, relaxation, and narcosis regimen:
ketamine (Ketanest 10%, 20 mg/kg intramuscularly), xylazine
(Xylazin 2%, 2 mg/kg intramuscularly), atropine sulfate (1%,
3 ml/animal), and propofol (Disoprivan 1%, 2–5 ml/animal). Endotracheal anesthesia was induced with isoflurane (1–1.5 vol%),
nitrous oxide (max. 75 vol%), and oxygen (25 vol%).
After anesthesia, the animals were fixed to an operative table,
and a laparotomy was performed. Using CS-14C coagulation
shears, we coagulated the muscular part of the abdominal wall
without skin or small intestine using different application regimens for each group. Depending on experimental group, the application time was 5 s, 10 s, or 5 s followed by 5 s of inactivity and
another 5 s of application. The level of output energy was set at 3
or 5 depending on experimental group (table 1). Ten individual
Pogorelić /Perko /Družijanić /Tomić /
Mrklić
Fig. 1. Histologic specimen illustrating lateral thermal damage of
the pig abdominal wall. HE. !200. The black line represents the
lateral damage measured by the pathologist using a computer
around the instrument’s jaw.
Fig. 2. Histologic specimen illustrating lateral thermal damage of
the pig small intestine. HE. !40. The black line represents the
lateral damage measured by the pathologist using a computer
around the instrument’s jaw.
lesions were performed for each experimental group using the
harmonic scalpel. The lesions were performed by compressing tissue (muscular part of the abdominal wall or whole intestinal wall)
in the instrument’s jaw. After the experiment, the animals were
euthanized with 7.4% solution of KCl.
The parts of abdominal wall and small intestine were removed
and fixed in 4% buffered formalin for 24 h. The preparations were
dehydrated in growing concentrations of alcohol, clarified in xylol,
and embedded in paraffin. The paraffin blocks were cut in 5-m
slides and stained with HE. We could clearly see the width of lateral thermal damage from the point of harmonic scalpel application to the margins of unchanged nearby tissue (fig. 1, 2).
Using an Olympus BX41 light microscope and morphometric
computer imaging analysis (Soft Imaging System, Münster, Germany), the width of the lateral thermal damage was measured at
the application area. The data was analyzed using Student’s t test
and Excel for Windows 11.0 (Microsoft, Redmond, Wash., USA)
and Statistica for Windows 12.0 (Statsoft, Tulsa, Okla., USA).
To perform this experiment, we obtained the approval of the
Ethical Committee of Split University Hospital.
Table 2. Comparison between groups
Compared
groups
Tissue
damage
(group 1)
mm
Tissue
damage
(group 2)
mm
t
(Student’s)
1:2
1:3
2:3
4:5
4:6
5:6
7:8
7:9
8:9
10:11
10:12
11:12
0.0825
0.0825
0.3850
0.2969
0.2969
0.4793
0.1302
0.1302
0.2655
0.1771
0.1771
0.2983
0.3850
0.1876
0.1876
0.4793
0.2013
0.2013
0.2655
0.2011
0.2011
0.2983
0.2258
0.2258
–21.286
–73.874
9.74
–7.715
4.516
10.211
–11.675
4.365
–7.178
–7.724
3.685
–5.076
p
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.002
Tissue damage presented as mean values. See table 1 for detailed description of treatment received by the groups.
Results
The levels of lateral thermal damage to the pig abdominal wall and small intestine tissues are presented in tables 1 and 2.
Abdominal Wall
At output level 3, the abdominal wall sustained thermal damage over a mean width of 0.0852 8 0.0234 mm
Preventing Lateral Thermal Damage
Using the Harmonic Scalpel
for group 1, as compared with 0.3850 8 0.0590 mm for
group 2. On the other hand, the application regimen
of 5 s with 5 s of inactivity and another 5 s of activity
(group 3) resulted in a mean thermal damage width of
0.1876 8 0.0652 mm. The difference in thermal damage
between all the individual experimental groups (1:2, 2:3,
1:3) was statistically significant (p ! 0.001). At output levEur Surg Res 2009;43:235–240
237
el 5, we found more thermal damage, which was expected
(group 4: 0.2969 8 0.0848 mm vs. group 5: 0.4793 8
0.1047 mm). Like at output level 3, in group 6 (the application regimen of 5 s with 5 s of inactivity and another 5
s of activity) we found a mean thermal damage width of
0.2013 8 0.0810 mm. The difference in thermal damage
between all the individual experimental groups (4:5, 5:6,
4:6) was statistically significant (p ! 0,001; table 2). Figure 1 shows how the damaged tissue of the abdominal
wall was measured.
Small Intestine
At output level 3, the small intestine sustained thermal
damage over a mean width of 0.1302 8 0.0238 mm for
group 7, as compared with 0.2655 8 0.0533 mm for group
8. On the other hand, the application regimen of 5 s with
5 s of inactivity and another 5 s of activity (group 9) resulted in a mean thermal damage width of 0.2011 8
0.0447 mm. The difference in thermal damage between
all the individual experimental groups (7:8, 8:9, 7:9) was
statistically significant (p ! 0.001).
At output level 5, as expected, we found greater thermal damage in group 11 (group 10: 0.1771 8 0.0198 mm
vs. group 11: 0.2983 8 0.0689 mm). Like at output level
3, in group 12 (5 s activity, 5 s inactivity, 5 s activity) we
found a mean thermal damage width of 0.2258 8 0.0373
mm. The difference in thermal damage between all the
individual experimental groups (10:11, 11:12, 10:12) was
statistically significant (table 2). Figure 2 shows how the
small intestine damaged tissue was measured.
Discussion
The development of dissecting systems based on highpower ultrasonic energy, especially for laparoscopic surgery, was instigated by the need for an alternative to highfrequency monopolar electrosurgery and to enable the
use of multifunctional instruments (e.g. shears that can
be used for mechanical dissection as well as energized
cutting and coagulation). The perception has been that
these high-power ultrasonic systems would improve the
efficiency of laparoscopic dissections and at the same
time reduce the morbidity from collateral/proximity iatrogenic injuries, well-documented with high-frequency
electro surgery [3, 4, 31, 32]. In addition, ultrasonic systems abolish smoke production, which, aside from obscuring the view, contains highly toxic and mutagenic
polycyclic hydrocarbons produced by the high-temperature pyrolysis of fat and protein [6].
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Eur Surg Res 2009;43:235–240
When using the harmonic scalpel, a lower amount of
energy is transduced to the tissue than when a high-frequency current or laser is used, and there is less possibility of lateral thermal damage or deep penetration because
lower temperatures are generated (only 50–100 ° C) [5].
Use of the harmonic scalpel has the additional benefit of
not passing any electrical energy through the body. Lateral thermal damage is reduced because less energy is
transduced to the tissue, and this is the basis for the potentially lower surgical stress associated with use of the
harmonic scalpel [3, 4].
Recent studies have explained the phenomenon of tissue expansion at higher temperatures, and the manner in
which lateral thermal damage can depend on instrument
application time and output energy [3, 4].
High-power ultrasonic dissection may result in considerable heat production and collateral tissue damage,
especially when the activation time exceeds 10 s. In these
cases, studies on rabbits have shown a lasting fibroblastic
reaction and delayed healing process [4, 31].
Regarding the rare occurrence of complications that
arise from overheating the working part of the instrument, a lower activation level will help avoid these [33,
34].
One reported in vivo study on pigs demonstrated
proximity injury detected by histological examination to
important structures, such as the bile duct, aorta, and inferior vena cava, during high-power ultrasonic dissection
[35]. In certain structures, the extent of the damage was
marked: up to 80% of the thickness of the bile duct was
coagulated in most areas, and there was 30% transmural
necrosis/injury to the ureter, aorta, and inferior vena
cava. Of even greater concern was the observation that
this damage was not macroscopically apparent at the
time of surgery, but was apparent only on histologic examination of the structures harvested at the time of sacrifice of the animals. This study, however, did not give
information on the power level (excursion of the vibrating tip) and the activation time used. These 2 variables
determine the extent of frictional heat production.
Other reported in vivo studies in pigs analyzed extreme and equivalent temperature gradients that were
generated by ultrasonic dissection [4]. Heat production
was directly proportional to the power setting and the
activation time. The core body temperature of the animals after completion of the laparoscopic dissections
rose by an average of 2.3 ° C. The zone around the jaws
that exceeded 60 ° C with continuous ultrasonic dissection for 10–15 s at level 5 measured 25.3 and 25.7 mm for
Ultracision and Autosonix, respectively. At this power
Pogorelić /Perko /Družijanić /Tomić /
Mrklić
setting and an activation time of 15 s, the temperature 1.0
cm away from the tips of the instrument exceeded 140 ° C.
Although there was no discernible macroscopic damage,
these thermal changes were accompanied by significant
histological injury that extended to the media of large
vessels and caused partial- to full-thickness mural damage of the cardia, ureter, and bile duct. Collateral damage
was absent or insignificant after dissections at power level 3 for both systems with the activation time not exceeding 5 s.
In this study, we showed that the degree of thermal
damage is commensurate to the duration of application,
i.e. the damage was 2–3 times higher in the groups with
a usage time of 10 s. Within the 10 s groups, those with
5 s of inactivity between the 2 applications had significantly less damage.
In all experimental groups, lateral thermal damage
that was inflicted using the instrument at output power
of 5 was 0.5–2 times higher (depending on the experiment group) than those at output power 3.
Statistical analysis of the data showed that the differences among all experimental groups were statistically
significant.
Our past research on rat abdominal walls showed
greater lateral thermal damage when the cutting time was
continuous rather than briefly interrupted [3]. Nevertheless, exactly how we should best use the harmonic scalpel
to achieve ideal tissue cutting and hemostasis with minimal thermal damage is still unknown. The aim of this
study was to determine the effects of using different harmonic scalpel application times on the in vivo experimental model of pig small intestines and abdominal
walls. We have tried this before using the small intestine
of rats, but this model is not applicable here, so we chose
pigs as they are closer to humans.
Conclusion
The aforementioned findings lead us to conclude that
lateral thermal damage at standard output power is greater after a longer application time. Lateral thermal damage
is also greater if the cutting time is continuous rather
than briefly interrupted. The harmonic scalpel is a useful
tool in both open and endoscopic surgery. The minimization of lateral thermal injury is very important for minimizing lateral thermal damage, and it is particularly important for operations near vital areas. In conclusion, our
results suggest that harmonic scalpel application times of
more than 5 s present a risk of lateral thermal damage,
especially near sensitive tissues or organs, such as the
common bile duct or ureter. The findings of this study
suggest that after 5 s of application, a 5 s pause should be
made, and then another 5 s can be applied if necessary.
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