Keywords
tubal ligation - fulguration - occlusion
Palavras-chave
ligadura tubária - fulguração - oclusão
Introduction
Tubal ligation is an effective form of permanent female contraception. In the world,
it is the most commonly used method of permanent contraception selected by women aged
between 15 and 49 who are married or in union.[1] In the United States, it is the second most commonly used form of contraception.[2] Among the different methods of tubal ligation, the monopolar electrocoagulation
has the lowest long-term failure rate,[3] but has been associated with thermal injury to the bowel and is rarely used.[4] Laparoscopic bipolar coagulation is a safe technique according to the American College
of Obstetricians and Gynecologists (ACOG) practice bulletin.[4] The ACOG recommends that at least 3 cm of the isthmic portion of the Fallopian tube
must be completely coagulated.[4] According to Soderstrom et al,[5] they were able to verify that with 35 W of potency, 100% of the tubes had a complete
occlusion of the lumen, while with 25 W, none of the tubes had a complete occlusion.
Nonetheless, the 95% confidence interval (CI) of the data derived from Soderstrom
et al[5] revealed a wide range in both groups: 100% (5 out of 5: 95% CI 56.6–100) using bipolar
coagulation at 35 W, while zero cases had a total occluded area with 25 W (0 out of
5: 95% CI 0–43).
The use of inline ammeter has been advocated when tubal ligation is performed, since
visual inspection is not accurate to identify the complete fulguration of the Fallopian
tube.[5]
[6] The use of inline ammeter is not recommended or mentioned by the Brazilian Health
Ministry[7] or the Brazilian Federation of Gynecologists and Obstetricians (FEBRASGO, in the
Portuguese acronym).[8]
Modern electrosurgical generators (solid-state electrosurgical generators) provide
constant power output by measuring the output voltage and current and adjusting the
drive signal to compensate for changes in the equivalent load impedance.[9] Therefore, it is necessary to provide evidences that the current practice of tubal
ligation without inline ammeter, using the bipolar mode in a modern electrosurgical
generator, delivers enough energy to collapse the lumen of the Fallopian tube. The
objective of this study is to determine which configuration and power setting of electrocoagulation,
using a modern electrosurgical generator, yield the smallest unobstructed area of
the Fallopian tubes.
Methods
Study Design and Setting
This experimental study took place between April 1st 2010 and December 30th 2011, at Hospital Femina located in Porto Alegre, Rio Grande do Sul, Brazil.
Fallopian Tubes
The Fallopian tubes were obtained from consecutive women who were scheduled for tubal
ligation or hysterectomy for benign conditions. Subjects were invited to participate
in the study and gave their written consent. The inclusion criteria consisted in normal
Fallopian tubes and age ≤ 50 years-old. Those who had gynecologic cancer, hydrosalpinx,
isthmic segment of the Fallopian tube < 3 cm and abnormal anatomy of the Fallopian
tube were excluded. These surgeries were performed by one of the authors (Campagnolo
M.I.), or by another surgeon previously instructed about the protocol.
Randomization
The randomization list was generated by an online program (www.randomization.com) using blocks of four. The randomized list was kept in sequenced sealed envelopes,
which were opened at the beginning of the surgery.
Intervention
During the procedure, each tube was randomly allocated to one of the following groups:
group A) 25 W x 5 seconds; group B) 30 W x 5 seconds; group C) 35 W x 5 seconds; group
D) 40 W x 5 seconds; group E) 40 W x 5 seconds visual inspection (blanch, swells,
collapse); group F) 50 W x 5 seconds. All groups used the coagulation mode, because
it is not possible to use the cutting mode in bipolar electrocoagulation. Bipolar
electrocoagulation was applied in groups A to E, and monopolar electrocoagulation
was performed in group F.
Electrocoagulation was performed in the coagulation mode using the WEM Model SS-501S
electrosurgical generator (WEM Equipamentos Eletrônicos Ltda, Ribeirão Preto, SP,
Brazil) with the Edlo bipolar forceps Ref. 14.1048 (EDLO, Canoas, RS, Brazil), or
the Rhosse monopolar forceps Ref. 12231 (Rhosse, Ribeirão Preto, SP, Brazil). Bipolar
coagulation of the tubes was performed on an auxiliary table after the uterus was
removed. Due to the characteristics of the monopolar system, electrocoagulation of
the Fallopian tubes was performed before the removal of the uterus. Monopolar coagulation
has been considered the most efficient method, as described in the literature,[3] and was limited to eight samples.
Fulguration of the tubes was performed on 3 contiguous areas, at least 3 cm in length,
as recommended in the literature.[10]
Outcome/Data Sources/Measurements
The mean occluded area of the Fallopian tube after fulguration in each group was the
main outcome. This outcome was analyzed in terms of mm2 and percentage of the transversal section of the Fallopian tube that was unobstructed.
The time to achieve the collapse of the Fallopian tube in group E was analyzed in
seconds. To analyze these variables, the coagulated tubes were resected and fixed
in a formaldehyde (10%) solution and embedded in paraffin for histological analysis.
The paraffin blocks were cut 4 µm thick and stained with hematoxylin and eosin.
The data sources were obtained after microscopic analysis of four transversal sections
taken from each block. The section with the highest thermal injury, according to Soderstrom
et al,[5] was chosen for digital photomicrography. Digital pictures were taken using an Olympus
BX51 microscope (Olympus Optical Co., Tokyo, Japan) connected to a digital color camera/Q-Color
5 (Olympus, Waltham, MA 02453, USA). The images were obtained with a UPlanFI 4X objective
lens (Olympus, Waltham, MA, USA) (resolution: 2.75 μm), at a size of 2,560 × 1,920
pixels (resolution: 1 mm = 590 pixels), under standard lighting conditions.
To reduce bias, each slide was coded, and the unobstructed area of the lumen was blindly
analyzed for the outcomes (open luminal area in mm2 and percentage of area that was open in the lumen). These outcomes were analyzed
with ImageJ software, v1.43j (ImageJ; National Institutes of Health, Bethesda, MD,
USA). Briefly, a circle was drawn around the lumen of the Fallopian tube. The outside
area was cleared, and the image was converted into 8 bits. The image was adjusted
for a threshold, using a dark background. Next, the region of interest (ROI) manager
was activated and saved in a file. From the ROI manager, the software calculated the
total and relative open area of the section.
Sample Size
The sample size was calculated based on data previously published[5] and using the formula described in the literature for superiority trial for continuous
outcome.[11] The following parameters were used: an α error of 0.05, power of 0.8, median lumen
occlusion (100%) using bipolar coagulation at 35 W, an expected reduction of the mean
occluded area by 85% with lower potencies (25 W), and a standard deviation of 10.
The standard deviation value was obtained from a pilot study in tubes that used visual
fulguration. These figures yielded a sample size of a minimum of eight cases in each
group.
Statistical Methods and Ethics
GraphPad Prism version 6 for Macintosh (GraphPad Software, Inc., San Diego, CA, USA)
was used for statistical analysis of the variables, using the Kruskal-Wallis test.
Gaussian distribution of the data was verified by the D'Agostino & Pearson omnibus
normality test. Ethnicity was analyzed using descriptive statistics. This study was
submitted and approved by the Research Ethics Committees of Hospital de Clínicas de
Porto Alegre and Grupo Hospitalar Conceição, under the numbers 09–624 and 09–253,
respectively.
Results
Fifty-nine women were invited to participate in the study, and 11 were excluded (6
had a short isthmic segment; 5 had abnormal anatomy of the Fallopian tube). Forty-eight
women, that is, 96 Fallopian tubes were fulgurated; 88 were submitted to bipolar and
8 to monopolar coagulation. Four tubes were discarded after randomization for technical
problems during histopathology processing (one in the 35W, 2 in the 40W and 1 in the
40 W visual). The characteristics of the groups are depicted in [Table 1].
Table 1
Baseline characteristics of the studied population
|
Parameter
|
Group of fulguration settings
|
P
[i]
|
|
25 W[a]
|
30 W[b]
|
35 W[c]
|
40 W[d]
|
40 Wv[e]
|
50 W[f]
|
|
Age[g]
|
40.7(8)
|
37.6(7.7)
|
43.6(8.8)
|
37.1(8.2)
|
40.4(8.3)
|
40(4)
|
0.5
|
|
Gestations[g]
|
3.2(1.5)
|
2.9(1.5)
|
2.8(1.2)
|
3.3(0.9)
|
2.8(1.2)
|
1.5(1.7)
|
0.3
|
|
Parity[g]
|
3.2(1.5)
|
2.8(1.6)
|
2.5(1.3)
|
3.1(1.3)
|
2.6(1.1)
|
1.5(1.7)
|
0.4
|
|
Ethinicity[h]
|
|
Caucasian
|
3
|
9
|
5
|
3
|
6
|
2
|
|
|
Non-caucasian
|
11
|
2
|
3
|
5
|
2
|
2
|
|
|
Tubes from
|
|
Abd hysterec
|
5
|
4
|
4
|
3
|
0
|
8
|
|
|
Vag hysterec
|
3
|
3
|
6
|
4
|
6
|
0
|
|
|
BTL-Abdomen
|
8
|
10
|
7
|
12
|
9
|
0
|
|
|
BTL-Vaginal
|
1
|
0
|
0
|
0
|
1
|
0
|
|
|
BSO
|
0
|
0
|
1
|
1
|
0
|
0
|
|
|
Total n of tubes
|
17
|
17
|
17
|
18
|
15
|
8
|
|
Abbreviations: Abd hysterec., abdominal hysterectomy; BSO, bilateral salpingo-oophorectomy;
BTL, bilateral tubal ligation; Vag hysterec., vaginal hysterectomy.
a 25 W x 5 seconds—bipolar;
b 30 W x 5 seconds—bipolar;
c 35 W x 5 seconds—bipolar;
d 40 W x 5 seconds—bipolar;
e 40 W visual inspection—bipolar;
f 50 W x 5 seconds—monopolar;
g numbers are given as means (standard deviation);
h each Fallopian tube of a patient was randomized to a different group;
i analysis of variance (ANOVA).
The median [range] unobstructed area (mm2) of each group was: A= 0.13 [0–3.96], B= 0.17 [0.01–3.3], C= 0.33 [0.03–4.61], D=
0.22 [0–3.53], E= 0.27[0.01–.45] and F = 0.94 [0.08–2.67]. No statistical significance
was found (p = 0.3—Kruskal-Wallis test—[Fig. 1A]). In contrast, the smallest median unobstructed area considering the percentage
of the total area (%) of the Fallopian tube was obtained in group E (40 W visual inspection—8.3%;
range from 0.9–40%), although no statistically significant difference was found among
the groups (p = 0.09, Kruskal-Wallis test—[Fig. 1B]). The mean (SD) time of coagulation for each grasp in group E was 3.8 (1) seconds.
The largest median unobstructed area was obtained with the monopolar method with 38.2%
(range 3.1–51%—[Fig. 1B]). Examples of tubal occlusion with different power settings are depicted in [Fig. 2].
Fig. 1 Median area (A) and percentage of the total area (B) of a transversal section of the Fallopian tube that was unobstructed by different
configurations and power settings (W). The bars represent the median value. The statistical
analysis was performed using the Kruskal-Wallis test. The area was calculated using
ImageJ software. Mono: monopolar fulguration.
Fig. 2 Photomicrograph of representative sections stained with hematoxylin & eosin. Total
occlusion of the Fallopian tube using 25 W (A) and 40 W visual (C). Partial occlusion of the lumen of the Fallopian tube using 40 W (B); inadequate occlusion of the lumen of the Fallopian tube using monopolar fulguration
at 50 W (D). Magnification was 200x.
Discussion
The new feature of modern electrosurgical generators, where constant electronic adjustments
provide constant power through different tissue changes, leads us to investigate if
total fulguration of the Fallopian tube, using different potencies and modes of fulguration
settings presented herein, could be achieved without the use of an inline ammeter.
We were not able to find any statistical difference among groups. The bipolar mode,
independently of the wattage used, yielded a median occluded area of 85% or more,
while the 40 W with visual inspection provided around 92% of occlusion. Occlusion
of the luminal area close to 0% (0– 1%) was observed in one sample of the 25 W group
(0%), one in the 30 W (0.9%), one in the 40 W (0.7%) and one in the 40W visual inspection
(0.9%). These findings may be explained by the high-peak bursts that desiccate the
outer layers of the tube too quickly and prevents the deep penetration of the energy.
This phenomenon may explain the smallest coagulation area (around 61%) obtained with
monopolar coagulation, which used 50W.
Based on our findings, it seems reasonable to follow the international recommendations
to use an inline ammeter, which is incorporated with most bipolar generators in the
US, to confirm total occlusion.[5]
[12] This recommendation is based on a review of 2,267 procedures done before 1987, where
failures on tubal ligation were observed.[13] In 1989, Soderstrom et al,[5] using 5 tubes derived from hysterectomy, demonstrated that bipolar system using
35 W in the coagulation mode yielded complete coagulation of the Fallopian tube. Likewise,
using 20 tubes, complete coagulation of the Fallopian tube was obtained with 25 W
in the cutting mode. These results were based on an old Kepplinger and Valleylab generators.[5]
Modern electrosurgical generators have electronic adjustments, which provide constant
power through different tissue changes, and can offer up to 40 W. These new electrosurgical
generators have a computer-controlled tissue feedback response system that senses
tissue impedance and corrects the energy flow.[14] In contrast, modern electrosurgical generators do not offer “pure cut” in the bipolar
mode, thus the use of an inline ammeter seems to be necessary to indicate when the
current through the Fallopian tube has ceased flow.
Unfortunately, an inline ammeter is not sold in Brazil, and the only orientation given
by the Brazilian Health Ministry and other institutions, such as the Brazilian Federation
of Gynecologists and Obstetricians (FEBRASGO, in the Portuguese acronym), is that
the procedure should be performed with bipolar mode.[7]
[8] This lack of details could be related to the report that bipolar coagulation system
is highly effective for bilateral tubal ligation, if a segment of ≥ 3 cm is coagulated.[13]
The strengths of this study are the calculated sample size and the use of ImageJ software
to quantify the unobstructed area of the Fallopian tube. Using an α error of 0.05
and data on unobstructed area (mm2), post-hoc analysis revealed a power of 95.7% comparing groups 40 W visual inspection
vs 50 W and 94.2% comparing 40 W vs 50 W. ImageJ provides an unbiased quantification of the open area, and this approach
and this approach is likely to be superior to visual inspection.[15] Initially, we used the histological grading described by Soderstrom et al,[5] but the high inter- and intraobserver variation (data not shown) led us to use the
ImageJ software, a widely used software for this and other purposes.[16]
[17]
[18]
[19]
The main weakness of the study is the degree of thermal injury. The histological analysis
was done after the electrocoagulation was performed. It has been shown that complete
occlusion may take up to 8 weeks to occur.[20] Therefore, our data may underestimate the real rate of the tubal occlusion. Another
minor weakness is the lack of external validity. Just one electrosurgical generator
was used, so no extrapolations can make to other models.
Although no significant difference was found among the groups, the mean occluded area
was higher in the monopolar mode, and this was an unexpected finding. This study brings
new data about the monopolar occlusion rate at 50 W, which was thought to be the best
method for tubal occlusion. Different settings for tubal fulguration, such as lower
wattage and longer time, may be sought to reach the best occlusion rate without using
an inline ammeter. A low-cost alternative for the Brazilian population may be the
use of an ammeter plier in one of the cables of the bipolar.
Conclusion
In summary, the modern electrosurgical generator used herein yielded a similar degree
of damage on the Fallopian tube independently of the configuration and power setting
used, and none of these settings reached a mean occluded area of 100%.
