ORIGINAL STUDIES
Plasma-Mediated Bipolar Radiofrequency
Ablation of Overlong Soft Palate in the
Dog: A Pilot Study
Sophie Palierne, DVM, PhD, Patricia Meynaud, PhD, DVM, Alexis Bilmont, DVM,
Maxence Delverdier, DVM, PhD, DECVP, Marie-Odile Semin, DVM, DESV, Mailys Stieglitz, DVM,
Guillaume Riviere, DVM, André Autefage, DVM, PhD, DECVS
ABSTRACT
The objective of this study was to compare the clinical, biological, macroscopic, and histologic outcomes after resection of
the soft palate by plasma-mediated bipolar radiofrequency ablation (PBRA) or traditional incisional techniques (incisional
soft palate resection [INC]) in dogs.
Ten dogs were divided in two groups. In the INC group, the soft palate was incised with scissors and the wound was
sutured in a continuous pattern. In the PBRA group, a wand was used to ablate the desired portion of the soft palate,
without suture. Clinical, biological, macroscopic, and histologic assessments were scheduled over 14 days.
The duration of surgery was significantly shorter for the PBRA group. The C-reactive protein concentrations were
significantly higher in the PBRA group at 6 hr and on day 3 (P , .05) but with values very close to the baseline. C-reactive
protein concentrations were maximal, but with low values (,25 mg/L), at day 1 for both techniques. The irregularity scores
for the soft palate caudal border on days 1, 3, and 14 were significantly higher in the INC group than in the PBRA group
(P , .05). The main histopathologic changes were the presence of superficial granulomas and a significantly greater depth
of tissue damage in the INC group (2.5 6 0.3 mm) compared with the PBRA group (1.5 6 0.1 mm; P , .05).
PBRA compared favorably with the traditional technique in terms of ease, duration of surgery, and depth of tissue
damage. Future studies are warranted to validate its effectiveness for treating brachycephalic airway obstruction syndrome in dogs. (J Am Anim Hosp Assoc 2018; 54:---–---. DOI 10.5326/JAAHA-MS-6668)
Introduction
of the oral and nasal mucosal ends.2 Alternative techniques of soft
Elongated soft palate is a frequent congenital respiratory problem in
palate resection such as CO2 laser, bipolar sealing device, and har-
brachycephalic dogs. The condition is usually associated with other
monic scalpel have been introduced to reduce postoperative in-
abnormalities of the upper respiratory tract such as stenotic nares and
flammation and for their superior ease of use.2–6 An alternative
everted laryngeal saccules. The free border of the soft palate over-
technique, folded flap palatoplasty, has been developed to correct
laps the glottal opening, causing increased respiratory effort, in-
both the excessive length and thickness of the soft palate and to
spiratory distress, inflammation, and edema. The condition is self-
relieve nasopharyngeal obstruction.7,8 This technique produces less
worsening, warranting early surgical correction.1
postoperative pharyngeal inflammation and edema because the
1
Traditionally, soft palate resection is performed by sharp inci-
suture material is more rostrally situated. However, this technique
sion with a scalpel blade or scissors followed by apposition and suture
is slightly more invasive and more technically demanding than
From the Clinical Research Unit (S.P., P.M., A.B., M.S., G.R., A.A.) and
CRP (C-reactive protein); INC (incisional soft palate resection); PBRA
Department of Biological and Fundamental Sciences (M.D., M-O.S.),
Ecole Nationale Vétérinaire de Toulouse, Université de Toulouse, Toulouse, France.
(plasma-mediated bipolar radiofrequency ablation)
Accepted for publication: April 7, 2017.
Correspondence: s.palierne@envt.fr (S.P.)
ª 2018 by American Animal Hospital Association
JAAHA.ORG
1
conventional soft palate resection.7,8 Recently, objective clinical ef-
analyses prior to surgery. Before being enrolled in our study, these
fects of the folded flap technique associated with modified rhino-
beagle dogs had already been used as control dogs in a previous
plasty, ventriculectomy, and partial cuneiformectomy have been
procedure and were intended to be euthanized. Their general state
assessed by whole-body barometric plethysmography, with en-
of health and well-being had been fully restored before the current
couraging results.
9
study. Given that the current study was classified as a nonrecovery
Plasma-mediated bipolar radiofrequency ablationa (PBRA) is a
procedure, it was conducted in total agreement with the Directive
recent radiofrequency-based surgical modality commonly used in
2010/63/EU of the European Parliament and of the Council on the
human surgery.10 With this technology, radiofrequency energy is
protection of animals used for scientific purposes. The study was
applied to a conductive medium (usually saline solution), which
also approved by the Institutional Ethical Committee.
causes a highly focused plasma field to form around the energized
electrodes. This plasma field is composed of highly ionized particles,
Surgical Technique
which have sufficient energy to break the organic molecular bonds
All dogs in both groups were induced with propofol (6 mg/kg in-
within tissue. The byproducts of this non–heat-driven process are
travenously) and received morphine (0.2 mg/kg intravenously). The
elementary molecules and low-molecular-weight inert gases. PBRA
dogs were intubated and maintained with isoflurane (2%) in oxygen.
causes volumetric removal of tissue at low temperatures ranging
They were then positioned in sternal recumbency with the head
from 608C to 808C, with minimal collateral damage.10 The histologic
raised by means of a tape placed under the maxilla. A 5 mm-wide
effect of PBRA was examined in several studies.11–20 Most of these
segment of the caudal border of the soft palate was resected in
were histopathologic evaluations of human tissue resected by PBRA,
both groups. The two procedures were performed by the same
Two
surgeon (S.P.). A PBRA system consisting of a consoleb and wandc
others were cadaveric studies of sheep and pig intervertebral
attached to a line of saline for automatic continuous irrigation was
and included tonsils, nasal turbinates, and ovarian cysts.
12,15
11,16–18
Four studies described the serial appearance of the wound
used for the PBRA procedure. A new wand was used for each dog.
created with PBRA following superficial application of the probe
The cutting mode was selected with a power setting of 7. The tip of
discs.
13,14,19,20
The ex-
the soft palate was grasped with an Allis forceps, and the wand was
amined tissues included canine vocal fold, rat tongue, sheep para-
used to ablate the desired portion of soft palate. No suture was
and a follow-up period of 3, 7, 14, and 29 days.
13,14,19,20
Even though
placed. For the INC procedure, an incision was made 5 mm from
PBRA is largely used in human medicine for surgery to reduce
the free edge of the soft palate with Metzenbaum scissors. A muco-
nasal sinuses, and rabbit paranasal sinuses.
snoring, no scientific studies have shown its tissue effects over a
mucous suture (polydioxanone, 4/0–dec 1.5 on swaged round
period of time.21 To our knowledge, no assessment of the macro-
needles)d was applied in a continuous pattern.
scopic and histologic appearance of the soft palate after resection of
All dogs were allowed to recover, then extubated and monitored
its free border with PBRA technology has been done in any species.
hourly for clinical signs associated with the respiratory tract, over a
The purpose of our study was to examine the serial appearance
total of 6 hr. Surgery duration and any incidental event were noted for
of the wound over 14 days after resection of the soft palate in healthy
both procedures. Morphine (0.1 mg/kg subcutaneously) was given
nonbrachycephalic dogs and to compare the clinical, biological,
for postoperative analgesia 4 hr after the first injection. Additional
macroscopic, and histologic outcomes of PBRA, used in cutting
morphine was reinjected every 4 hr, depending on the pain score (see
mode, with the traditional incisional technique. Our hypothesis was
below).
that PBRA-assisted palatoplasty would be faster and easier than the
traditional technique and would result in less postoperative edema
Postoperative Evaluation
and inflammation.
Clinical assessments were scheduled daily over 14 days. Biological
and macroscopic assessments were performed at 1, 3, 7, and 14 days
Materials and Methods
and histologic evaluation only at 14 days. Each clinical and histo-
Dogs
pathologic evaluation parameter was graded as follows: 0: normal;
Ten adult beagle dogs (10.3 6 1.6 kg; range 9–12.5 kg) were ran-
1: mild changes; 2: moderate changes; 3: severe changes.
domly divided into two groups of five dogs for either PBRA soft
A single examiner, blinded for the surgical technique, per-
palate resection or incisional soft palate resection (INC). The dogs
formed a thorough physical examination before surgery, 6 hr
were acclimated to the new accommodation room and to being
postoperatively, and then daily from day 1 to day 14. Six parameters
manipulated by examiners for 7 days prior to the study. Each dog
were used to assess pain (subjective global pain evaluation, general
underwent a complete physical examination and serum biochemical
attitude, interactive behavior, cardiac frequency, ability to palpate the
2
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Plasma-Mediated Bipolar Radiofrequency Soft Palate Ablation
larynx, and response of the larynx to palpation). The intensity of
The inter-observer agreement for all five macroscopic param-
respiratory noises was noted on auscultation. The presence of cough
eters was good, ranging from 0.7 (edema) to 0.9 (color of soft palate
and gagging was also noted.
border). The physical examinations were unremarkable for both
Serum samples were taken once on the day of surgery (baseline)
groups throughout the study. The pain and respiratory scores did not
and then 6 hr, 1 day, 3, 7, and 14 days after surgery. The C-reactive
differ significantly between the two groups and did not vary sig-
protein (CRP) concentration (reference interval: 0–10 mg/L) was
nificantly before or after surgery. No additional morphine was re-
e
measured by immunoturbidimetry method. CRP concentrations
were plotted over time, and the area under the curve was calculated
quired for any of the dogs.
The C-reactive protein results are presented in Figure 1. In the
PBRA group, CRP was high on postoperative days 1, 2, and 3. In the
for each dog.
The soft palate was inspected immediately after the surgi-
INC group, CRP was only increased on postoperative day 1. CRP
cal procedure and then, under general anesthesia with propofol
was significantly higher for the PBRA group than for the INC group
(6 mg/kg intravenously), on days 1, 3, 7, and 14. A digital photograph
at 6 hr and on day 3 (P , .05). The area under the curve for
was taken, and a score (0 ¼ no change; 1 ¼ mild changes; 2 ¼
the PBRA group (123.8 6 14.7 mg 3 day/L) was not significantly
moderate changes; 3 ¼ intense changes; 4 ¼ severe changes) was
different (P ¼ .11) from that of the INC group (104.1 6
assigned by two independent observers at the end of the study. For
10.6 mg 3 day/L).
this macroscopic evaluation, five parameters were assessed and
The macroscopic appearance of the soft palate of one repre-
graded: edema, regularity of the section, thickness, color of the soft
sentative dog from each group is shown in Figure 2. The mean
palate border, and size of the granuloma if present.
scores for each of the five dogs and the two observers (10 obser-
The dogs were euthanized 14 days after surgery. The remaining
vations) are presented in Table 1 for each group.
portion of the soft palate was removed, sutured to cardboard, and
In the INC group, swelling of the palate was visible on day 0, 1,
fixed in 10% buffered formalin. Five full-thickness sections (4 mm
and 3, with maximum edema on day 1 (scores from 0 to 2). In the
wide) were made perpendicular to the edge of the excision. The first
PBRA group, mild edema was observed in only one dog on day 3 and
section was obtained at the midline of the palate. Two sections
by only one observer. The edema did not differ significantly between
were made at the left and right lateral edges and two others between
the two groups.
the midline and the lateral edges. The sections were embedded in
The soft palate was mildly to highly irregular in all dogs in the
paraffin, sectioned at 3 mm, and stained with hematoxylin and eosin.
INC group from day 0 to day 14, with a peak on day 3 (scores from 2
Each palate was subjectively graded for five parameters (inflam-
to 4). A mildly to moderately irregular soft palate wound was also
mation, fibroplasia, edema, hemorrhage, and necrosis) with the
seen in all dogs in the PBRA group from day 1 to day 3 and in only
22
same scale used by Brdecka. A consensual assessment was obtained
one dog on day 14. In the PBRA group, severe irregularity was
by two pathologists (M.D. and M.O.S.). The maximum depth of
observed in only one dog on day 0 and its soft palate was perfectly
injury was also recorded for each sample. The highest value of the
regular by day 14. The irregularity score was significantly higher
different sections was recorded for each parameter.
for the INC group than for the PBRA group on days 1, 3, and 14
(P , .05).
Data Analysis and Statistical Evaluation
Mild to severe thickening of the soft palate was detected in all
An analysis of variance test for clinical, macroscopic, and histologic
dogs in the INC group from day 1 to day 7, with a peak on days 1 and
data was employed for the statistical analysis. A Cohen’s Kappa
3 (scores from 2 to 4). Mild to intense thickening of the soft
coefficient was used to measure inter-observer agreement. The
palate was apparent on day 1, and moderate to severe thickening was
means of the observers’ values were used if this coefficient was $0.7.
noted on day 3 in all dogs in the PBRA group, which strongly improved
The significance level was set at P , .05. Results were expressed as
by days 7 and 14 (only one dog showed mild thickening on day 14).
mean 6 standard deviation.
The thickness score at the end of the surgical procedure, and on day
14, was significantly higher for the INC group than for the PBRA
Results
group (P , .05).
The physical examination and serum biochemical analyses were
Two small granulomas were observed in one dog in the INC
unremarkable for all dogs at the beginning of the study. No intra-
group from day 1 to day 3 in focal areas where apposition of the
operative complications occurred in either of the groups. The
mucosa had been inadequate.
duration of surgery was significantly shorter for the PBRA group
(504 6 168 s) than for the INC group (1,044 6 202 s; P , .05).
A discolored fringe on the free border of the soft palate, delineated by a thin reddish rim, was observed in all dogs in the PBRA
JAAHA.ORG
3
FIGURE 1
C-reactive protein re-
sults for the plasma-mediated bipolar
radiofrequency ablation group (light
gray bars) and incisional soft palate
resection group (dark gray bars). The
upper limit of the reference range is
indicated with a horizontal dotted
line. Asterisks indicate significant
differences between the two groups.
group, from day 1 to day 7 (Figure 2). The extent and intensity of the
though no sutures had been used to appose the oral and nasal
discoloration diminished over time in all dogs, and the color dif-
mucosa. Most of the histopathologic lesions observed with both
ference was no longer apparent on day 14 (Figure 2). Whatever the
methods were similar. Changes were apparent in two layers of the
changes, the color scores did not differ significantly between the two
connective tissue. The superficial layer was thin with a moderate per-
groups.
ivascular infiltrate of mononuclear cells (macrophages, lymphocytes,
The histologic scores are listed in Table 2. Microphotographs
plasmocytes) and mild edema. The deep layer showed local exten-
of soft palate samples are presented in Figure 3. By day 14, the
sive, moderate-to-marked fibroplasia and some areas of myofiber de-
surface of the section obtained after PBRA had epithelialized even
generation and focal necrosis. The main differences in histopathologic
FIGURE 2
Macroscopic appear-
ance of the soft palate of one representative dog in the PBRA group
(above) and INC group (below),
immediately after the operation (T0),
and on postoperative day 1 (D1), day
3 (D3), day 7 (D7), and day 14 (D14).
In each photograph, the tongue is on
the bottom and the hard palate is on
the top. A discolored area (asterisk)
delineated by a thin reddish rim (arrowheads) is visible on the free border
of the soft palate, 7 days (D7) after
PBRA. INC, incisional soft palate resection; PBRA, plasma-mediated bipolar radiofrequency ablation.
4
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Plasma-Mediated Bipolar Radiofrequency Soft Palate Ablation
TABLE 1
Scores for the Macroscopic Assessment
Macroscopic Parameters
Method of
Resection
PBRA
INC
Day
Edema
Regularity
Thickness
Color
Granuloma
0
0.0 6 0.0
(0.0–0.0)
1.2 6 1.1
(0.0–3.0)
a
0.8 6 0.4
(0.0–1.0)
1.0 6 0.7
(0.0–2.0)
0.0 6 0.0
(0.0–0.0)
1
0.0 6 0.0
(0.0–0.0)
1.8 6 0.3b
(1.0–2.0)
2.3 6 0.6
(1.0–3.0)
2.2 6 0.8
(1.0–3.0)
0.0 6 0.0
(0.0–0.0)
3
0.1 6 0.2
(0.0–1.0)
1.2 6 0.3c
(1.0–2.0)
2.6 6 0.7
(2.0–4.0)
2.2 6 0.6
(1.0–3.0)
0.0 6 0.0
(0.0–0.0)
7
0.0 6 0.0
(0.0–0.0)
0.5 6 0.6
(0.0–2.0)
0.9 6 0.7
(0.0–2.0)
1.3 6 0.4
(1.0–2.0)
0.0 6 0.0
(0.0–0.0)
14
0.0 6 0.0
(0.0–0.0)
0.1 6 0.2d
(0.0–1.0)
0.1 6 0.2e
(0.0–1.0)
0.0 6 0.0
(0.0–0.0)
0.0 6 0.0
(0.0–0.0)
0
0.1 6 0.2
(0.0–1.0)
1.6 6 0.5
(1.0–2.0)
1.5 6 0.5a
(1.0–2.0)
0.2 6 0.4
(0.0–1.0)
0.0 6 0.0
(0.0–0.0)
1
0.5 6 0.6
(0.0–2.0)
2.7 6 0.8b
(1.0–3.0)
2.8 6 0.8
(2.0–4.0)
1.0 6 0.8
(0.0–2.0)
0.3 6 0.7
(0.0–3.0)
3
0.1 6 0.2
(0.0–1.0)
3.0 6 0.8c
(2.0–4.0)
2.8 6 0.8
(2.0–4.0)
1.0 6 0.7
(0.0–2.0)
0.2 6 0.4
(0.0–2.0)
7
0.0 6 0.0
(0.0–0.0)
1.2 6 0.4
(1.0–2.0)
1.4 6 0.4
(1.0–2.0)
0.1 6 0.2
(0.0–1.0)
0.0 6 0.0
(0.0–0.0)
14
0.0 6 0.0
(0.0–0.0)
1.2 6 0.4d
(1.0–2.0)
0.8 6 0.3e
(0.0–1.0)
0.0 6 0.0
(0.0–0.0)
0.0 6 0.0
(0.0–0.0)
0 ¼ no change; 1 ¼ mild changes; 2 ¼ moderate changes; 3 ¼ intense changes; 4 ¼ severe changes.
Data
for all five dogs and two observers (10 observations) in each group is presented as mean 6 standard deviation (minimal–maximal score).
a–e
The same superscript indicates a significant difference between the two groups (P , .05).
INC, incisional soft palate resection; PBRA, plasma-mediated bipolar radiofrequency ablation.
changes between the two methods were the presence of superficial
toward the soft palate and makes a series of very shallow punctures
granulomas and/or suppuration in the INC group and a significantly
in the underlying muscle. A lower energy setting is used than in our
greater depth of tissue injury (2.5 6 0.3 mm) in the INC group
study, just to scar and tighten the tissue. It is impossible to ex-
compared with PBRA group (1.5 6 0.1 mm; P , .05).
trapolate such results to PBRA soft palate resection by cutting mode
in dogs. In humans, PBRA is used in cutting mode for tonsillec-
Discussion
tomy, with the same wand as in our study. The risk of post-
The results of our study confirmed our hypothesis. Resection of the
tonsillectomy hemorrhage was recently compared in 15,734 patients
soft palate with PBRA was easier and faster than with the traditional
following use of the cold steel technique (gold standard) or hot
incisional technique. To our knowledge, this is the first in vivo report
techniques (diathermy scissors, PBRA, laser, and ultracision).24
to compare the serial development of the wounds obtained after
PBRA resulted in a 3.2-times higher risk of posttonsillectomy
resection of the soft palate with the PBRA technique or traditional
hemorrhage than the cold technique but was associated with a lower
incisional technique, over 14 days, and to assess any clinical, bio-
risk of need for further surgery than with other hot techniques.
logical, macroscopic, and histologic differences between the techniques.
These results therefore warranted a study of local macroscopic
Current evidence suggests that no major safety concerns are
effects on soft palate after ablation by PBRA, over a 14-day period,
associated with radiofrequency ablation of the soft palate for snoring
23
as described here.
in humans. Radiofrequency ablation can be used interstitially or in
In previous studies of PBRA involving histologic assessment of
cutting mode. In human medicine, the most recent interventional
the remaining tissues, PBRA was applied locally for just a few seconds
procedure guidance recommends interstitial radiofrequency abla-
on vocal fold, tongue, sinus, or turbinate mucosa without any tissue
tion.23 The aim with this procedure is to stiffen the soft palate in
resection.13,14,19,20 As the probe was used briefly and superficially in
order to prevent excessive vibration but not to ablate a volume of
these studies, they could not provide information about the soft
soft palate as in our study. A wand with needle tip is directed upward
tissue damage occurring in cutting mode during tissue ablation. The
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TABLE 2
Scores for the Histologic Assessment
Histological Parameters*
Method of
Resection
PBRA
INC
Case No.
Inflammation
Fibroplasia
Edema
Hemorrhage
Necrosis
Granuloma/Suppuration
Depth of
Injury, mm
1
1
1
1
1
1
0
1.5
2
1
3
1
1
1
1
1.4
3
2
1
0
0
1
0
1.6
4
1
1
0
1
1
0
1.6
5
1
1
1
1
1
0
1.4
1
1
3
1
1
2
1
2.8
2
1
3
1
1
1
1
2.8
3
1
2
1
0
1
1
2.6
4
3
1
2
1
1
1
2.2
5
1
2
0
0
0
1
2.3
* 0 ¼ no change; 1 ¼ mild changes; 2 ¼ moderate changes; 3 ¼ severe changes.
INC, incisional soft palate resection; PBRA, plasma-mediated bipolar radiofrequency ablation.
sizes of the tissue lesions generated by interstitial radiofrequency
concentrations were obtained on day 1 with both techniques, as
at differing power settings were recently determined in human
previously described.28,29 Although CRP was significantly higher
tonsils and chicken breast tissue ex vivo.21 The most important
with PBRA at 6 hr and on day 3, the area under the curve from
reported limitation of these previous studies is that in vitro or
baseline to day 14 did not differ significantly between the two
ex vivo findings cannot necessarily be extrapolated to in vivo
groups. In recent studies, CRP varied from 0.07 to 16.8 mg/L in
conditions. Furthermore, the tissue effect of PBRA can evolve
clinically healthy dogs and increased 17- to 29-fold from the
over time or depend on the type of tissue, hence the need to assess
baseline value, 24–48 hr post surgery in dogs after ovariohyster-
the effects of PBRA, used in cutting mode on canine soft palate
ectomy and excision of superficial tumors, respectively.28,29 In
tissue, in vivo over a period of time corresponding to the healing
the present study, the maximum CRP concentrations were low
period.
(,30 mg/L), indicating that the tissue trauma due to surgery was
The present study of soft palate resection was conducted on
only slight.
healthy, nonbrachycephalic dogs. This was considered appropriate
PBRA palatoplasty was easy to perform in the current study and
because our objective was to compare the serial macroscopic ap-
allowed precise sculpting of the soft palate, as shown by the sig-
pearance of the wound after PBRA or use of the incisional tech-
nificant differences in the regularity scores on day 1, day 3, and day
nique, before applying the procedure in clinical patients. By using
14. Resection with scissors and sutures requires soft palate manip-
clinically normal dogs, it was possible to eliminate any variables
ulation and, due to its dependence on tissue elasticity and the ac-
attributable to brachycephalic syndrome abnormalities (stenotic
cessibility of the area, may not be easy. With PBRA, soft palate
nares, everted laryngeal saccules, or tracheal abnormalities) or
manipulation is minimal, and the wand is ergonomic. The signifi-
specific histopathologic findings (greater thickening of the soft
cantly lower scores obtained for soft palate thickness on day 0 and
palate, peculiar histologic features), and also to harvest histopathologic
day 14 in the group receiving PBRA were mainly due to (1) its
samples at the end of the study.25–27 Any postoperative clinical and
limited depth of effect, (2) its low temperature, and (3) the lack of
histopathologic signs would thus be directly attributable to surgery.
suture of the soft palate free border after resection.14 As in humans, a
No adverse reaction, such as excessive inflammation, hemor-
PBRA channeling procedure could be used to achieve soft palate
rhage, edema, aberrant scar formation or their manifestation as
thinning and shrink the tissues surrounding the treatment zone
cough, gagging, and pain, was observed during the postoperative
after elongated soft palate ablation.30 This procedure could provide a
clinical assessment, whatever the technique used.
minimally invasive alternative to the folded flap technique described
The severity of inflammation generated by surgical trauma
to reduce soft palate thickness in dogs.7,8 An assessment of PBRA
was assessed by measuring CRP concentrations over time. CRP
soft palate thinning was beyond the scope of our study and still
was mildly increased with both techniques. The maximum CRP
needs to be explored in dogs.
6
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Plasma-Mediated Bipolar Radiofrequency Soft Palate Ablation
indicated that PBRA produced less postoperative pain and improved healing. These advantages were attributed to the limited depth
of effect and low temperature of PBRA (608C–808C). In contrast,
laser treatment was considered to result in more peripheral damage
with charred tissue and a much higher temperature (about
4008C).16,31 Even though PBRA is associated with posttonsillectomy
hemorrhage in humans, there is less need for further surgery than for
all the other hot techniques, probably because of the limited peripheral effect of PBRA.24
The local macroscopic evaluation revealed inflammatory
changes on the soft palate with both techniques. Although the difference was not significant, PBRA was associated with less edema
and fewer signs of inflammation, such as granulomas. At day 14, the
good thickness and regularity scores obtained for the PBRA group
clearly demonstrated the advantage of PBRA over the incisional
technique for soft palate resection and highlighted the low morbidity
of the technique, as reported in another preclinical study of PBRA on
canine vocal cords.14
In earlier studies, histologic assessments of canine soft palate
had been done on days 2, 3, 4, 7, and 14 after resection, either on
small biopsies or after sacrifice.3,4,14 Histologic changes were
reported with both laser and traditional techniques, with peak inflammation, necrosis, and ulceration occurring on day 3.4 PBRA
induced initial stages of inflammation on the canine vocal fold on
day 4, and a more mature inflammatory reaction was observed on
day 7.14 In our study, a single histopathologic assessment was done
FIGURE 3
Representative photographs of histological slides. The
depth of tissue injury (black line measured in mm) is lower with
PBRA (A) than with the traditional incisional technique (B).
on day 14 when the presence or absence of aberrant scar formation was most visible. The lack of histopathologic information prior
to day 14 was mitigated by evaluating a systemic inflammatory
response based on CRP, as in a previous study, and by local macroscopic assessment of the surgical wound.32 Nevertheless, a histo-
A color change, visible as a white fringe on the free border of the
pathologic examination of the earlier stages could help us better
soft palate, was observed with PBRA (Figure 2). This color change
understand the injury mechanisms associated with PBRA in cutting
evolved favorably, with a maximum intensity on day 1 and progressive
mode. The grading system used for the histologic evaluation has
resolution until day 14. The precise nature of this modification re-
already been described.22 It did not reveal any difference between the
mains unknown and warrants further investigation in histologic
two techniques used here with regard to inflammation, fibroplasia,
studies. It could be attributed to tissue ischemia, very superficial
edema, hemorrhage, and necrosis. This might be because the his-
mucosal erosion, or coagulation necrosis, which was the most con-
tologic samples were obtained during the late phase of inflamma-
sistent finding observed shortly after applying PBRA.14,24 Whatever
tion.4 In a study involving incisional or CO2 laser techniques, the
the surface area of this white fringe, it was not correlated with tissue
necrosis, ulceration, and inflammation noted on days 0–3 had dis-
damage severity, as shown by the lack of mucosal debridement and
appeared by day 14, and the lesions noted on day 14 were similar to
the limited depth of histologic injury on day 14. This effect seems to
those reported in our study.4 Our scores compared favorably with
be very superficial and quickly disappears. These results are consistent
those of other studies involving CO2 laser or a bipolar sealing device,
with several previous studies that compared the outcome of PBRA
probably because our evaluation was done much later (on day 14
versus laser for tonsillectomy or palatoplasty in humans.16,31
versus day 2 or day 4).22
In contrast to CO2 laser, PBRA removed tissue at much lower
Histologic examination revealed a significantly smaller depth
temperatures, resulting in less peripheral thermal damage.31 Results
of effect with PBRA than with the traditional technique. This limited
JAAHA.ORG
7
depth of injury observed with PBRA was consistent with previous
PBRA was also of limited depth and shallower than that produced
studies in which PBRA only affected the superficial tissue with no
by the traditional technique. PBRA can be considered an alterna-
14,21
The depth of injury produced by PBRA in
tive technique for resection of elongated soft palate in dogs as it
cutting mode in our study (1.5 6 0.1 mm) compared favorably
ensures better regularity of the palatine wound and more rapid
with that of laser treatment (3.3 mm) and a bipolar sealing device
sutureless healing. Future clinical and histologic studies are warranted
(3.5 mm), although the timing of our analysis was later than those
to determine the nature of the early superficial effect and to validate
underlying injury.
of other studies.
22
A secondary significant difference was the presence of granu-
the effectiveness of PBRA in brachycephalic airway obstructive
syndrome dogs.
lomas and suppuration in all dogs in the incisional group compared
with only one in the PBRA group. This beneficial effect of PBRA
is probably related to the absence of a foreign body reaction due to
FOOTNOTES
a
suture materials. The choice of the suture material would have an
influence on the inflammatory effects of the suture. A 4/0 monofilament absorbable suture on swaged round needle was chosen to limit
b
c
tissue trauma. In a clinical situation, it would probably be preferable to choose a more rapidly absorbed suture such as polyglecaprone
25 rather than polydioxanone to reduce tissue inflammation. However,
considering the time necessary for polyglecaprone 25 absorption,
d
e
Coblation Plasma Technology, ArthroCare ENT; Smith & Nephew plc,
London, United Kingdom
Coblator II Surgery System, EC8000-01, ArthroCare ENT; Smith &
Nephew plc, London, United Kingdom
EVac Plasma Wand 70 Xtra, EIC5872-01, ArthroCare ENT; Smith &
Nephew plc, London, United Kingdom
PDS II suture (polydioxanone); Ethicon (Johnson & Johnson),
Somerville, New Jersey
CRP Plus; Thermo Fisher Scientific Konelab System, Waltham,
Massachusetts
we assumed that at 14 days this suture would also be persistent in
tissue, which would not have changed our histological findings.33
Complete healing was obtained in all dogs in the PBRA group
without any need to appose the oral and nasal mucosa with sutures
and without aberrant tissue formation.
The duration of surgery with PBRA (504 s) was halved in
comparison with the standard technique. This reduction in operative
time was also observed with laser (174–309 s), bipolar sealing device
(67 s), and harmonic scalpel (300 s).4,6,22 The operative time required with PBRA should improve further as experience is gained
with this new procedure.
The PBRA handpiece costs approximately $150 and, as a singleuse instrument, is quite expensive for general use. However, after
cleaning and sterilization with gas or liquid sterilizing agents, the wand
may be reused more than 10 times for a range of soft tissue procedures
(personal data). This represents a significant saving in cost and makes
PBRA a financially viable alternative to sharp dissection or lasers.
The first limitation in this study was our use of normal nonbrachycephalic dogs in whom the soft palate differs from that of
brachycephalic obstructive airway syndrome dogs. The relatively
short follow-up could also have impeded the detection of additional
events. Finally, the timing of our histologic evaluation made comparison with other studies difficult.
Conclusion
PBRA in cutting mode is a safe technique for resection of the soft
palate in nonbrachycephalic dogs. This technique compared favorably with the traditional technique in terms of ease, surgical time,
and postoperative inflammation and edema. The lesion created with
8
JAAHA |
54:5 Sep/Oct 2018
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