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Gas embolism during hysteroscopic surgery using bipolar or monopolar diathermia: a randomized controlled trial
Research
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GENERAL GYNECOLOGY
Gas embolism during hysteroscopic surgery using bipolar or monopolar diathermia: a randomized controlled trial Birgitte A. Dyrbye, MD; Lucilla E. Overdijk, MD; Paul J. van Kesteren, MD, PhD; Peter de Haan, MD, PhD; Robert K. Riezebos, MD, PhD; Erica A. Bakkum, MD, PhD; Bart M. Rademaker, MD, PhD
OBJECTIVE: The objective of the study was to determine the incidence
and amount of gas embolism during hysteroscopic surgery using either monopolar or bipolar diathermia and to investigate the relationship between the severity of gas embolism and the amount of intravasation of distension fluid. STUDY DESIGN: This was a randomized, observer-blinded trial. Fifty
patients, scheduled for hysteroscopic surgery, were assigned to either monopolar or bipolar diathermia. Transesophageal echocardiography was used to detect and classify gas embolism (grade 0-IV). Intravasation of distension fluid was measured. RESULTS: Venous gas embolism was observed in all but 1 patient. A
higher incidence of more extensive (grade IV) was seen during bipolar
diathermia (42% vs 13%; P ⫽ .031). Paradoxical embolism was observed in 2 patients. When intravasation exceeded 1000 mL, significantly more grade IV venous gas embolism was seen (P ⫽ .049). CONCLUSION: During hysteroscopic surgery, gas embolism was
equally observed irrespective of the type of diathermia. However, more extensive embolism was observed when intravasation of distension fluid exceeded 1 L. These results question the acceptance of up to 2500 mL intravasation of distension fluid if bipolar diathermia is used. Key words: diathermia, gas embolism, hysteroscopy, transcervical resection of myoma or endometrium, transesophageal echocardiography
Cite this article as: Dyrbye BA, Overdijk LE, van Kesteren PJ, et al. Gas embolism during hysteroscopic surgery using bipolar or monopolar diathermia: a randomized controlled trial. Am J Obstet Gynecol 2012;207:271.e1-6.
T
ranscervical resection of myoma (TCR-M) and transcervical resection of endometrium (TCR-E) are established and safe minimal invasive hysteroscopic procedures.1,2 However, potentially life-threatening venous gas emboli (VGE) and paradoxical embo-
From the Department of Anesthesiology, Academic Medical Center (Dr Dyrbye), and the Departments of Anesthesiology (Drs Overdijk, de Haan, and Rademaker), Gynecology (Drs van Kesteren and Bakkum), and Cardiology (Dr Riezebos), Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands. Received April 27, 2012; revised June 27, 2012; accepted July 20, 2012. The authors report no conflict of interest. Presented, in part, at the 8th Annual Scientific Meeting of the Dutch Society for Anesthesiology, Ede, The Netherlands, Sept. 30, 2011. Reprints: Bart M. Rademaker, MD, PhD, Department of Anesthesiology, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands. [email protected]. 0002-9378/$36.00 © 2012 Mosby, Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog.2012.07.027
lism have been described.3-5 It is thought that during hysteroscopic surgery, exposed uterine veins may allow gas to enter the circulation. These emboli most likely originate from the products of electrosurgical vaporization. They consist of hydrogen, carbon monoxide, and carbon dioxide, and their slow rate of absorption from the circulation allows them to reach the heart. When monopolar diathermia is used during hysteroscopic procedures, electrolyte free medium (eg, sorbitol 2%) is used for uterine distension. More recently, bipolar diathermia was introduced in hysteroscopic surgery, which allows for the use of an isotonic distension medium (NaCl 0.9%). Consequently, dilutional hyponatremia can be avoided and intravasation of up to 2500 mL is considered to be safe.6 This provides more time to complete the hysteroscopic myomectomy. However, this higher limit of intravasation may not be as safe as has hitherto been thought because a recent retrospective analysis showed that 43% of patients who had intravasation between 1000 and 2500 mL
experienced clinical symptoms that result from the formation of gaseous emboli.7 The gaseous particles produced by monopolar electrodes are smaller and might be more likely to enter the circulation.8,9 In addition, in vitro experimental studies have shown that monopolar diathermia is associated with more gas production compared with bipolar diathermia.10 Whether this leads to more intravascular gas embolism is not yet known. No studies are available that compare monopolar and bipolar instruments on the incidence and grade of venous gas VGE during operative hysteroscopy. Therefore, in the present study, the difference between monopolar and bipolar diathermia with respect to the incidence and grade of VGE was determined by using transesophageal echocardiography (TEE). The primary objective of our study was to investigate the prevalence of VGE between monopolar and bipolar diathermia. In addition, the incidence and grade of VGE were related to the amount of intravasation of distension fluid.
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General Gynecology
M ATERIALS AND M ETHODS Trial design We conducted a single-center, randomized, semiblinded study. The study was approved by the appropriate ethics committee (Verenigde Commissies Mensgebonden Onderzoek, St Antonius Ziekenhuis, Nieuwegein, The Netherlands) and was registered at the Dutch organization for registration of human research (Centrale Commissie Mensgebonden Onderzoek) under no. 1357. Informed consent was obtained from each patient before inclusion in the study. Patients Patients, scheduled for TCR-M because of intracavitary myomas or TCR-E because of medication resistant menorrhagia, were studied. Myomas were measured by transvaginal ultrasound, and the intra cavitary extension of the myomas was determined by saline infusion sonography and consequently graded in type 0-3 according to the Wamsteker classification.11 Exclusion criteria were age younger than 18 years or older than 70 years, a history of pulmonary embolism, cardiac disease or any contraindication for TEE (esophageal disease), and American Society of Anesthesiologists (ASA) classification III or higher. Non–Dutch-speaking patients were also excluded. Only patients with an expected operating time that exceeded 0.5 hours were included. The study protocol was approved by the hospital medical ethical committee, and each participant provided informed, written consent. Patients were randomized by envelopes, designating either monopolar or bipolar diathermia. The study was open by its nature to the principal investigator and the operating gynecologist. The cardiologist who reviewed the TEE images was blinded for both diathermia groups. Anaesthesia and operative procedure All patients received propofol-based total intravenous general anesthesia. Monitoring during this procedure included 3-lead electrocardiography with ST-II segment analysis (ST-II), noninvasive blood pressure measurement, pulse oxi271.e2
metry, infrared CO2 analysis, inspired oxygen fraction, nasopharyngeal temperature, and minute ventilation. Ventilation was controlled to maintain a normal end-tidal CO2. A data management system (MetaVision Anaesthesia Information Management System; iMDsoft, Needham, MA) collected all hemodynamic (including ST-segment changes) and ventilatory and respiratory data during the operation with a sample frequency of 1 per minute. Data were stored in the hospital’s central MSQL client/ server database. The operative procedures were performed by 3 experienced gynecologists. Monopolar diathermia (Olympus resectoscope, loop diameter 6.5 mm [Olympus Medical Systems Europa, Hamburg, Germany], connected to Erbe VIO generator (Erbe Elektromedicin, Tübingen, Germany), power setting for cutting: mode dry cut, effect 4, maximum 200 W, for coagulation: mode spray coagulation, effect 1, maximum 75 W) was used in combination with electrolyte-free, 2% sorbitol containing distension fluid. During bipolar diathermia (Olympus resectoscope, loop diameter 5 mm, connected to Erbe VIO generator, power setting for cutting: mode bipolar cut plus, effect 4, maximum 250 W, power setting for coagulation mode: mode bipolar soft plus, effect 4, maximum 250 W), normal saline was used as distension medium. To obtain a clear operating field, gas air bubbles and debris are actively removed from the uterine cavity by a continuous in- and outflow system (Olympus Uteromat, inflow pressure 80 mm Hg, flow 400 mL/min). To minimize the chance of air entrance in the uterus, the surgeon purged the air from all lines and hysteroscopic instruments before starting the resection, and after the change of every fluid bag. Following cervical dilation, the open cervix was minimally exposed to room air and the cervix was kept closed at all times, using a tenaculum forceps. The removal of tissue chips from the uterine cavity with reintroduction of the hysteroscopic instruments followed by accidental introduction of air was minimized.
American Journal of Obstetrics & Gynecology OCTOBER 2012
www.AJOG.org Outcomes Intraoperative characteristics including operating time, amount of intravasation, ST-II segment changes, end-tidal CO2, peripheral oxygen saturation, and extremes in blood pressure and pulse-rate were retrieved from the data management system. After the induction and placement of an oropharyngeal tube, an anesthesiologist qualified for TEE inserted an A 5 mHz multiplanar probe (Vivid-i GE Healthcare, Cardiovascular Ultrasound System; GE Medical Systems, Tirat Carmel, Israel). Because air bubbles dissolved in the intravenous fluid disturb the TEE imaging, no intravenous fluids were administered during anesthesia to avoid artifacts. Before the start of surgery, the gain setting was adjusted to minimize artifact and the midesophageal 4-chamber view was continuously monitored. The first recording was made before the start of surgery. Thereafter a loop of 3 heart cycles was recorded every 2 minutes. A final recording was made at the end of surgery, after the uterus distension was terminated. Because surgery lasted longer than 30 minutes in all patients, each patient had at least 15 recordings. A cardiologist, blinded for the study groups, reviewed the TEE loops. To quantify the degree of embolism by TEE, a 5-stage classification was used (Figure). Grade 0 was defined as the absence of emboli passing through the heart. Grade I embolization was defined as the presence of a limited number (⬍10 per field of view) of small particles in the right atrium (RA), right ventricle (RV), and right ventricular outflow tract (RVOT). Grade II included moderate amount of small particles (10-20 per field of view). Grade III included many small particles (⬎20 per field of view), and grade IV included many small and large particles (⬎20 per field of view), completely filling the diameter of RA, RV, and RVOT. To assess a relationship between the amount of intravasation and the grade of VGE, both monopolar and bipolar groups were brought together and analyzed according to the amount of intravasation.
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FIGURE
Degree of embolism
General Gynecology
Research
A cutoff point of 1000 mL of intravasation was chosen because this is considered the safe upper limit of intravasation when monopolar diathermia is used.7 During the operative hysteroscopy, cardiovascular disturbances that might be the result of VGE are as follows: a drop in end-tidal CO2 more than 20% of baseline, a blood pressure drop of more than 25% (not explained by hypovolemia), ventricular arrhythmias or electrocardiographic changes (defined as an STsegment change of more than 2 mm from baseline). Cardiovascular instability was defined when at least 2 of these clinical signs were present.
Statistical and power analysis The sample size was calculated by a priori power analysis. A target alpha of 0.05 and a beta of 0.8 and a 30% increase in the occurrence of venous emboli using monopolar diathermia compared with bipolar diathermia resulted in a group size of 21 patients. To correct for a possible loss of patients during follow-up, 25 patients were included in both groups. Data are presented as totals, means, and percentages when indicated. Continuous variables were analyzed using unpaired Student t test or Mann-Whitney U test, whereas categorical variables were analyzed using a 2 test. Grading of the embolic events and possible confounders were analyzed using a multivariate analysis of variance for repeated measures. A P ⱕ .05 was Embolic events observed and graded on transesophageal echocardiography. A, Grade 0 embolization and absence of emboli passing through the heart. B, Grade I embolization and a limited number (⬍10 per field of view) of small particles in the RA, RV, and RVOT. C, Grade II embolization and moderate amount of small particles (10-20 per field of view). D, Grade III embolization and many small particles (⬎20 per field of view). E, Grade IV embolization and many small and large particles (⬎20 per field of view) completely filling the diameter of RA, RV, and RVOT. RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract. Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
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TABLE 1
Demographic, clinical and intraoperative characteristics Monopolar group (n ⴝ 24)
Variable
Bipolar group (n ⴝ 22)
Age, y
45.5 ⫾ 7.0
43.7 ⫾ 7.4
Weight, kg
73.0 ⫾ 14.2
71.4 ⫾ 13.2
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
168.9 ⫾ 6.4
Height, cm
166.1 ⫾ 5.9
..............................................................................................................................................................................................................................................
ASA (1/2)
16/8
17/5
Para status 0/1/2/3 or more
12/2/7/3
10/4/6/2
6 (25%)
8 (36%)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
Hormonal therapy
..............................................................................................................................................................................................................................................
TCR-M/TCR-E
15/10
19/5
..............................................................................................................................................................................................................................................
Myoma, cm
2.9 (0–5) ⫾ 1.2
2.5 (1–4) ⫾ 0.8
Myoma class (0/1/2/3)
3/11/3/0
3/11/2/0
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
49.4 (24–180) ⫾ 29.4
Surgery, min
50.8 (30–90) ⫾ 15.1
..............................................................................................................................................................................................................................................
Data are mean (range) ⫾ SD or number (percentage). ASA, American Society of Anesthesiologists; TCR-M/TCR-E, transcervical resection of myoma/transcervical resection of endometrium. Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
considered statistically significant. All statistical analyses were performed using SPPS version 17.0 (SPSS Inc, Chicago, IL).
R ESULTS A total of 50 women were included: 40 patients scheduled for TCR-M and 10 patients scheduled for TCR-E. Four patients (3 bipolar, 1 monopolar) were excluded in the final analysis, 2 because of loss of the TEE-images and 2 because no abnormalities were observed during the procedure, and only a diagnostic hysteroscopy was performed. There were no statistically significant differences with respect to the patient demographic, obstetric, relevant gynecological, and intraoperative characteristics between the study groups (Table 1). One
patient in the monopolar and 2 patients in the bipolar group underwent a TCR-M as well as a TCR-E procedure. VGE were observed in all but 1 patient. Significantly more grade IV VGE was observed during bipolar diathermia (*, P ⫽ .05). The total number and percentage of patients experiencing different grades of VGE are shown in Table 2. In addition, the different grades of VGE were associated with the amount of intravasation in each group. No VGE was observed at levels of intravasation below 240 mL. The relationship of the grade of VGE with intravasation at a cutoff point of 1000 mL is demonstrated in Table 3. Significantly more grade IV VGE was observed if intravasation exceeded 1000 mL (P ⫽ .049). In the bipolar group, 7 pa-
tients (32%), and in the monopolar group 5 patients (21%) experienced intravasation above 1000 mL. The incidence of cardiovascular disturbances and cardiovascular instability, which resulted from VGE was the same in both groups. The number of patients in each group that experienced cardiovascular symptoms is shown in Table 4. In none of the patients was ventricular arrhythmia observed. However, a systolic blood pressure decrease exceeding 25% of baseline was noticed in 33% of the patients if both groups were combined. Seven of 13 patients with grade IV VGE showed a drop in end-tidal CO2. In these 7 patients, ST-segment changes were observed in 91.6 %. Pre- and postoperatively, no interventions for cardiovascular instability were needed. Major complications with overt cardiovascular collapse were not observed in any of the patients, even with high grades of VGE. Paradoxical embolism was observed in 2 patients (4.3% of all patients), both in the bipolar group, at an intravasation of 300 and 2300 mL, respectively. In these 2 patients, no changes in cardiovascular measurements that might result from VGE were observed.
C OMMENT In the present study, the difference in incidence and grade of venous gas embolism between monopolar and bipolar operative hysteroscopy was compared and related to the amount of intravasation of distension fluid. VGE was observed in almost every patient (98%) using either monopolar or bipolar diathermia. Bipolar diathermia was associated with a significantly higher incidence of
TABLE 2
Distribution of venous gas embolism (grade 0-IV) among patients and related amount of intravasation Variable
Grade 0
Monopolar, n (%)
1 (4)
Intravasation, mL
240 (–)
Grade I
Grade II
Grade III
Grade IV
7 (29)
7 (29)
6 (25)
3 (12)
................................................................................................................................................................................................................................................................................................................................................................................ a
378 (0–1400)
620 (250–800)
967 (600–1200)
1215 (30–1700)
................................................................................................................................................................................................................................................................................................................................................................................ b
Bipolar, n (%)
0 (–)
1 (4)
6 (27)
5 (23)
10 (45)
................................................................................................................................................................................................................................................................................................................................................................................ a
Intravasation, mL
500 (–)
474 (100–670)
833 (200–2300)
950 (200–2000)
................................................................................................................................................................................................................................................................................................................................................................................ a
Data presented as mean (range); b P ⫽ .031.
Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
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General Gynecology
www.AJOG.org VGE grade IV; 42% of the patients with bipolar diathermia experienced grade IV VGE. When the amount of intravasation was related to the grade of VGE, significantly more grade IV VGE was observed in the patients with intravasation greater than 1000 mL. The present finding of the high incidence of venous gas embolism is in agreement with a recent study in patients who underwent an operative hysteroscopy.12 In that study, gas bubbles could be demonstrated in the right atrium in all patients, and a continuous flow of bubbles was observed in 85% of the patients, as monitored by transthoracic echocardiography. Although monopolar diathermia is associated with more gas production compared with bipolar diathermia in in vitro experimental studies,10 more grade IV VGE was observed in the bipolar group in the present study. This might be attributed to the larger gaseous particles produced by bipolar diathermia.8,9 Because the composition of the gas bubbles (hydrogen, carbon monoxide, and carbon dioxide) appears to be the same using either monopolar or bipolar diathermia,8,9 the bigger particles that arise during bipolar diathermia are less likely to dissolve before they reach the heart. The higher incidence of grade IV in the bipolar group can also be explained by the higher level of intravasation in the bipolar group. When intravasation exceeded 1000 mL, higher grades of VGE were observed, irrespective of the type of distension fluid used. It is reasonable to assume that gaseous products of hysteroscopic electro surgery and intravasation fluid enter the circulation simultaneously through the surgically opened veins in the myometrium. As a result, an increase of intravasation will lead to an increase of gaseous emboli that enter the circulation. Indeed, the relation between intravasation and grade of VGE has been noticed before.7 Some technical differences between monopolar and bipolar resectoscopy have to be considered. We have used monopolar resectoscopes with a bigger loop diameter compared with the bipolar resectoscopes, which may shorten operating room time in case of monopolar
Research
TABLE 3
Relationship of intravasation >1000 mL with the grade of venous gas embolism (all patients of both groups combined) Variable
Grade 0
Grade I
Grade II
Grade III
Grade IV
⬍1000 mL, n (%) (34 patients)
2 (6)
6 (18)
13 (38)
6 (18)
7 (20)
⬎1000 mL, n (%) (12 patients)
0 (0)
1 (8)
0 (0)
5 (41)
6 (50)
.086
.049
.............................................................................................................................................................................................................................................. a a .............................................................................................................................................................................................................................................. a a
P value
.743
.113
.012
.............................................................................................................................................................................................................................................. a
P values compared to patients with ⬍1000 mL intravasation.
Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
surgery and reduce the amount of gas bubbles. However, the size and class of the myoma as well as the operating room time were not significantly different between the monopolar and bipolar group. The energy dispersed from the loop into the tissue may differ between monopolar and bipolar surgery and may influence gas bubble formation. The Erbe VIO generator, although limited in different amount of watts in the mono- and bipolar settings, provides a variable amount of power, depending on the amount of tissue that is in contact with the loop. Energy delivery from a monoor bipolar loop is therefore a very inconsistent factor throughout the procedure but may indeed influence the formation of gas. Increased coagulation may enhance closure of the veins and therefore limit the access of bubbles into the blood stream. The same counts for the reduction of insufflation pressure. Both are interesting subjects for future studies. The present study has several limitations. Although it is a prospective randomized clinical trial, the study was open to the principal investigator and the op-
erating gynecologist. However, any bias caused by not blinding the primary investigator is unlikely to have influenced the results because an independent cardiologist reviewed the TEE images. Videorecordings with the TEE-probe were made at set times and not continuously. Therefore, higher grades of VGE might have been underestimated. The observed VGE might not only be the result of electrosurgery. Room air can also enter the circulation during the process of removing and reinserting the scope, which acts as a piston in the vaginal cylinder to force air in the open uterine veins. Indeed, 1 patient in the present study demonstrated grade IV VGE during introduction of the resectoscope, without electrosurgery. This was also reported by Corson et al,13 who described 2 patients who died, apparently because room air entered the circulation through surgically exposed blood vessels. The composition of room air does not allow it to dissolve rapidly, which might augment the TEE image and worsen the clinical consequences.
TABLE 4
Clinical parameters changes that might be the result of a venous gas embolism Variables
Monopolar group (n ⴝ 24)
Bipolar group (n ⴝ 22)
EtCO drop ⬎20%
n ⫽ 4 (17%)
n ⫽ 4 (18%)
RR systolic drop ⬎25%
n ⫽ 6 (25%)
n ⫽ 9 (40%)
ST-segment depression ⬎2 mm
n ⫽ 4 (17%)
n ⫽ 6 (18%)
Cardiovascular instability
n ⫽ 4 (17%)
n ⫽ 4 (18%)
2 .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
EtCO2, end-tidal carbon dioxide pressure; RR, Riva Rocci blood pressure; ST-segment, electrocardiographic change. Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
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Clinical symptoms related to the occurrence of VGE are determined by the volume of gas entrainment and the rate of accumulation. A relatively large volume of gas that enters the circulation rapidly or a small volume entering over a longer period of time can give physiological changes.14 Most of the symptoms that occur during an embolic event are attributed to the direct effects of venous emboli, such as air lock in the right ventricle.4,15,16 The symptoms of VGE in an anesthetized patient are the following: a decrease in end-tidal CO2, hypoxia, electrocardiographic changes, hypotension, electromechanical dissociation, and asystole. The most sensitive monitoring device for venous embolism is the TEE, which detects as little as 0.02 mL/kg of air administered by bolus injection.14 In the present study, no major complications with overt cardiovascular collapse were seen. Because only ASA 1 and 2 patients were included, this may underestimate the cardiorespiratory consequences of VGE. The incidence of cardiovascular instability with a decrease in blood pressure and lowered levels of end-tidal CO2 was similar in both groups. More than 90% of our patients with grade IV emboli showed ST-II segment changes that indicate right ventricular strain.17 ST-II changes can also be explained by paradoxical embolism through an open foramen ovale or through patent pulmonary pathways and consequently a disruption of right coronary artery blood flow.18 In the present study, paradoxical embolism was observed in 2 patients. An episode of severe VGE that exceeds the capacity of lungs to filter emboli may also result in paradoxical embolism.19 Paradoxical embolism can result in serious neurological and cardiac complications. The overall incidence of 28% of severe, grade IV VGE raises concern in that respect. The results of the present study do not favor either mono- or bipolar diathermia. Although significantly more grade IV VGE was observed during bipolar diathermia, this can not be attributed exclusively to the use of the bipolar diathermia. The higher level of intravasation of isotonic distension fluid (up to 2500 mL)
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that is accepted during bipolar diathermia might be an important factor. Although the results of the present study question the liberal acceptance of intravasation of up to 2500 mL using bipolar diathermia, they do not justify a lower acceptable level of intravasation. However, irrespective of the type of diathermia, caution is warranted for the occurrence of extensive VGE if intravasation exceeds 1000 mL. If intravasation exceeds 1000 mL, the procedure should be terminated immediately as soon as any sign of gas embolism occurs, using routine monitoring including an electrocardiogram, end-tidal CO2, blood pressure, and saturation. Future studies are needed to confirm the relationship of VGE and intravasation of distension fluid with cardiopulmonary symptoms and minor clinical symptoms such as fatigue, nausea, and vomiting, which may slow down postoperative recovery. In conclusion, during hysteroscopic electro surgery venous gas embolism occurred in almost every patient in both monopolar and bipolar groups. More extensive embolism was observed when intravasation exceeded 1 L. The acceptance of intravasation of up to 2500 mL of normal saline during bipolar diathermia is questioned. f ACKNOWLEDGMENTS We acknowledge with great appreciation Lea Dijksma and Marieke Kluut (currently affiliated with the Department of Anaesthesiology, St Radboud, Nijmegen, The Netherlands) for their contributions while preparing the protocol and the manuscript.
REFERENCES 1. Di Spiezio Sardo A, Taylor A, Tsirkas P, Mastrogamvrakis G, Sharma M, Magos A. Hysteroscopy: a technique for all? Analysis of 5000 outpatient hysteroscopies. Fertil Steril 2008;98:438-43. 2. Shveiky D, Rojansky N, Revel A, Benshushan A, Laufer N, Shushan A. Complications of hysteroscopic surgery: “beyond the learning curve”. J Minim Invasive Gynecol 2007;14:218-22. 3. Cooper JM, Brady RM. Intraoperative and early postoperative complications of operative complications of operative hysteroscopy.Obstet Gynecol Clin North Am 2000;27:347-66. 4. Munro MG. Complications of hysteroscopic and uterine resectoscopic surgery. Obstet Gynecol Clin North Am 2010;37:399-425.
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www.AJOG.org 5. Paschopoulos M, Polyzos NP, Lavasidis LG, Vrekoussis T, Dalkalitsis N, Paraskevaidis E. Safety issues of hysteroscopic surgery. Ann N Y Acad Sci 2006;1092:229-34. 6. Loffer FD, Bradley LD, Brill AI, Brooks PG, Cooper JM. Hysteroscopic fluid monitoring guidelines. The ad hoc committee on hysteroscopic training guidelines of the American Association of Gynecologic Laparoscopists. J Am Assoc Gynecol Laparosc 2000;7:167-8. 7. Rademaker BMP, Kesteren van PJM, Haan de P, Rademaker D, France C. How safe is the intravasation limit in hysteroscopic surgery? J Minim Invasive Gynecol 2011;18:355-61. 8. Munro MG, Weisberg M, Rubinstein E. Gas and air embolization during hysteroscopic electrosurgical vaporization: comparison of gas generation using bipolar and monopolar electrodes in an experimental model. J Am Assoc Gynecol Laparosc 2001;8:488-94. 9. Farrugia M, Hussain SY, Perett D. Particulate matter generated during monopolar and bipolar hysteroscopic human uterine tissue vaporization. J Minim Invasive Gynecol 2009;16:458-64. 10. Munro MG, Brill AI, Ryan T, Ciarrocca S. Electrosurgery-induced generation of gases: comparison of in vitro rates of production using bipolar and monopolar electrodes. J Am Assoc Gynecol Laparosc 2003;10:252-9. 11. Wamsteker K, Emanuel MH, de Kruif JH. Transcervical hysteroscopic resection of submucous fibroids for abnormal uterine bleeding: results regarding the degree of intramural extension. Obstet Gynecol 1993;82:736-40. 12. Imasogie N, Crago R, Leyland NA, Ghung F. Probable gas embolism during operative hysteroscopy caused by products of combustion. Can J Anesth 2002;49:1044-7. 13. Corson SL, Brooks PG, Soderstrom RM. Gynecologic endoscopic gas embolism. Fertil Steril 1996;65:529-33. 14. Mirski MA, Lele AV, Fitzsimmons L, Toung TJK. Diagnosis and treatment of vascular air embolism. Anesthesiology 2007;106:164-77. 15. Mushambi MC, Williamson K. Anaesthetic considerations for hysteroscopic surgery. Best Pract Res Clin Anesthesiol 2002;16:35-51. 16. Groenman FA, Peters LW, Rademaker BMP, Bakkum EA. Embolism of air and gas in hysteroscopic procedures: pathophysiology and implications for daily practice. J Minim Invasive Gynecol 2008;15:241-7. 17. Leibowitz D, Beshalom N, Kaganov Y, Rott D, Hurwitz A, Hamani Y. The incidence and haemodynamic significance of gas emboli during operative hysteroscopy: a prospective echocardiographic study. Eur J Echocardiogr 2010;11:429-31. 18. Ghimouz A, Loisel B, Kheyar M, Fried D, Bouret JM. Carbon dioxide embolism during hysteroscopy followed by transient blindness. Ann Fr Anesth Reanim 1996;15:192-5. 19. Rademaker B, Groenman F, van der Wouw P, Bakkum E. Paradoxical gas embolism by transpulmonary passage of venous emboli during hysteroscopic surgery: a case report and discussion. Br J Anaesth 2008;101:230-3.
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GENERAL GYNECOLOGY
Gas embolism during hysteroscopic surgery using bipolar or monopolar diathermia: a randomized controlled trial Birgitte A. Dyrbye, MD; Lucilla E. Overdijk, MD; Paul J. van Kesteren, MD, PhD; Peter de Haan, MD, PhD; Robert K. Riezebos, MD, PhD; Erica A. Bakkum, MD, PhD; Bart M. Rademaker, MD, PhD
OBJECTIVE: The objective of the study was to determine the incidence
and amount of gas embolism during hysteroscopic surgery using either monopolar or bipolar diathermia and to investigate the relationship between the severity of gas embolism and the amount of intravasation of distension fluid. STUDY DESIGN: This was a randomized, observer-blinded trial. Fifty
patients, scheduled for hysteroscopic surgery, were assigned to either monopolar or bipolar diathermia. Transesophageal echocardiography was used to detect and classify gas embolism (grade 0-IV). Intravasation of distension fluid was measured. RESULTS: Venous gas embolism was observed in all but 1 patient. A
higher incidence of more extensive (grade IV) was seen during bipolar
diathermia (42% vs 13%; P ⫽ .031). Paradoxical embolism was observed in 2 patients. When intravasation exceeded 1000 mL, significantly more grade IV venous gas embolism was seen (P ⫽ .049). CONCLUSION: During hysteroscopic surgery, gas embolism was
equally observed irrespective of the type of diathermia. However, more extensive embolism was observed when intravasation of distension fluid exceeded 1 L. These results question the acceptance of up to 2500 mL intravasation of distension fluid if bipolar diathermia is used. Key words: diathermia, gas embolism, hysteroscopy, transcervical resection of myoma or endometrium, transesophageal echocardiography
Cite this article as: Dyrbye BA, Overdijk LE, van Kesteren PJ, et al. Gas embolism during hysteroscopic surgery using bipolar or monopolar diathermia: a randomized controlled trial. Am J Obstet Gynecol 2012;207:271.e1-6.
T
ranscervical resection of myoma (TCR-M) and transcervical resection of endometrium (TCR-E) are established and safe minimal invasive hysteroscopic procedures.1,2 However, potentially life-threatening venous gas emboli (VGE) and paradoxical embo-
From the Department of Anesthesiology, Academic Medical Center (Dr Dyrbye), and the Departments of Anesthesiology (Drs Overdijk, de Haan, and Rademaker), Gynecology (Drs van Kesteren and Bakkum), and Cardiology (Dr Riezebos), Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands. Received April 27, 2012; revised June 27, 2012; accepted July 20, 2012. The authors report no conflict of interest. Presented, in part, at the 8th Annual Scientific Meeting of the Dutch Society for Anesthesiology, Ede, The Netherlands, Sept. 30, 2011. Reprints: Bart M. Rademaker, MD, PhD, Department of Anesthesiology, Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands. [email protected]. 0002-9378/$36.00 © 2012 Mosby, Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog.2012.07.027
lism have been described.3-5 It is thought that during hysteroscopic surgery, exposed uterine veins may allow gas to enter the circulation. These emboli most likely originate from the products of electrosurgical vaporization. They consist of hydrogen, carbon monoxide, and carbon dioxide, and their slow rate of absorption from the circulation allows them to reach the heart. When monopolar diathermia is used during hysteroscopic procedures, electrolyte free medium (eg, sorbitol 2%) is used for uterine distension. More recently, bipolar diathermia was introduced in hysteroscopic surgery, which allows for the use of an isotonic distension medium (NaCl 0.9%). Consequently, dilutional hyponatremia can be avoided and intravasation of up to 2500 mL is considered to be safe.6 This provides more time to complete the hysteroscopic myomectomy. However, this higher limit of intravasation may not be as safe as has hitherto been thought because a recent retrospective analysis showed that 43% of patients who had intravasation between 1000 and 2500 mL
experienced clinical symptoms that result from the formation of gaseous emboli.7 The gaseous particles produced by monopolar electrodes are smaller and might be more likely to enter the circulation.8,9 In addition, in vitro experimental studies have shown that monopolar diathermia is associated with more gas production compared with bipolar diathermia.10 Whether this leads to more intravascular gas embolism is not yet known. No studies are available that compare monopolar and bipolar instruments on the incidence and grade of venous gas VGE during operative hysteroscopy. Therefore, in the present study, the difference between monopolar and bipolar diathermia with respect to the incidence and grade of VGE was determined by using transesophageal echocardiography (TEE). The primary objective of our study was to investigate the prevalence of VGE between monopolar and bipolar diathermia. In addition, the incidence and grade of VGE were related to the amount of intravasation of distension fluid.
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M ATERIALS AND M ETHODS Trial design We conducted a single-center, randomized, semiblinded study. The study was approved by the appropriate ethics committee (Verenigde Commissies Mensgebonden Onderzoek, St Antonius Ziekenhuis, Nieuwegein, The Netherlands) and was registered at the Dutch organization for registration of human research (Centrale Commissie Mensgebonden Onderzoek) under no. 1357. Informed consent was obtained from each patient before inclusion in the study. Patients Patients, scheduled for TCR-M because of intracavitary myomas or TCR-E because of medication resistant menorrhagia, were studied. Myomas were measured by transvaginal ultrasound, and the intra cavitary extension of the myomas was determined by saline infusion sonography and consequently graded in type 0-3 according to the Wamsteker classification.11 Exclusion criteria were age younger than 18 years or older than 70 years, a history of pulmonary embolism, cardiac disease or any contraindication for TEE (esophageal disease), and American Society of Anesthesiologists (ASA) classification III or higher. Non–Dutch-speaking patients were also excluded. Only patients with an expected operating time that exceeded 0.5 hours were included. The study protocol was approved by the hospital medical ethical committee, and each participant provided informed, written consent. Patients were randomized by envelopes, designating either monopolar or bipolar diathermia. The study was open by its nature to the principal investigator and the operating gynecologist. The cardiologist who reviewed the TEE images was blinded for both diathermia groups. Anaesthesia and operative procedure All patients received propofol-based total intravenous general anesthesia. Monitoring during this procedure included 3-lead electrocardiography with ST-II segment analysis (ST-II), noninvasive blood pressure measurement, pulse oxi271.e2
metry, infrared CO2 analysis, inspired oxygen fraction, nasopharyngeal temperature, and minute ventilation. Ventilation was controlled to maintain a normal end-tidal CO2. A data management system (MetaVision Anaesthesia Information Management System; iMDsoft, Needham, MA) collected all hemodynamic (including ST-segment changes) and ventilatory and respiratory data during the operation with a sample frequency of 1 per minute. Data were stored in the hospital’s central MSQL client/ server database. The operative procedures were performed by 3 experienced gynecologists. Monopolar diathermia (Olympus resectoscope, loop diameter 6.5 mm [Olympus Medical Systems Europa, Hamburg, Germany], connected to Erbe VIO generator (Erbe Elektromedicin, Tübingen, Germany), power setting for cutting: mode dry cut, effect 4, maximum 200 W, for coagulation: mode spray coagulation, effect 1, maximum 75 W) was used in combination with electrolyte-free, 2% sorbitol containing distension fluid. During bipolar diathermia (Olympus resectoscope, loop diameter 5 mm, connected to Erbe VIO generator, power setting for cutting: mode bipolar cut plus, effect 4, maximum 250 W, power setting for coagulation mode: mode bipolar soft plus, effect 4, maximum 250 W), normal saline was used as distension medium. To obtain a clear operating field, gas air bubbles and debris are actively removed from the uterine cavity by a continuous in- and outflow system (Olympus Uteromat, inflow pressure 80 mm Hg, flow 400 mL/min). To minimize the chance of air entrance in the uterus, the surgeon purged the air from all lines and hysteroscopic instruments before starting the resection, and after the change of every fluid bag. Following cervical dilation, the open cervix was minimally exposed to room air and the cervix was kept closed at all times, using a tenaculum forceps. The removal of tissue chips from the uterine cavity with reintroduction of the hysteroscopic instruments followed by accidental introduction of air was minimized.
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www.AJOG.org Outcomes Intraoperative characteristics including operating time, amount of intravasation, ST-II segment changes, end-tidal CO2, peripheral oxygen saturation, and extremes in blood pressure and pulse-rate were retrieved from the data management system. After the induction and placement of an oropharyngeal tube, an anesthesiologist qualified for TEE inserted an A 5 mHz multiplanar probe (Vivid-i GE Healthcare, Cardiovascular Ultrasound System; GE Medical Systems, Tirat Carmel, Israel). Because air bubbles dissolved in the intravenous fluid disturb the TEE imaging, no intravenous fluids were administered during anesthesia to avoid artifacts. Before the start of surgery, the gain setting was adjusted to minimize artifact and the midesophageal 4-chamber view was continuously monitored. The first recording was made before the start of surgery. Thereafter a loop of 3 heart cycles was recorded every 2 minutes. A final recording was made at the end of surgery, after the uterus distension was terminated. Because surgery lasted longer than 30 minutes in all patients, each patient had at least 15 recordings. A cardiologist, blinded for the study groups, reviewed the TEE loops. To quantify the degree of embolism by TEE, a 5-stage classification was used (Figure). Grade 0 was defined as the absence of emboli passing through the heart. Grade I embolization was defined as the presence of a limited number (⬍10 per field of view) of small particles in the right atrium (RA), right ventricle (RV), and right ventricular outflow tract (RVOT). Grade II included moderate amount of small particles (10-20 per field of view). Grade III included many small particles (⬎20 per field of view), and grade IV included many small and large particles (⬎20 per field of view), completely filling the diameter of RA, RV, and RVOT. To assess a relationship between the amount of intravasation and the grade of VGE, both monopolar and bipolar groups were brought together and analyzed according to the amount of intravasation.
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FIGURE
Degree of embolism
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Research
A cutoff point of 1000 mL of intravasation was chosen because this is considered the safe upper limit of intravasation when monopolar diathermia is used.7 During the operative hysteroscopy, cardiovascular disturbances that might be the result of VGE are as follows: a drop in end-tidal CO2 more than 20% of baseline, a blood pressure drop of more than 25% (not explained by hypovolemia), ventricular arrhythmias or electrocardiographic changes (defined as an STsegment change of more than 2 mm from baseline). Cardiovascular instability was defined when at least 2 of these clinical signs were present.
Statistical and power analysis The sample size was calculated by a priori power analysis. A target alpha of 0.05 and a beta of 0.8 and a 30% increase in the occurrence of venous emboli using monopolar diathermia compared with bipolar diathermia resulted in a group size of 21 patients. To correct for a possible loss of patients during follow-up, 25 patients were included in both groups. Data are presented as totals, means, and percentages when indicated. Continuous variables were analyzed using unpaired Student t test or Mann-Whitney U test, whereas categorical variables were analyzed using a 2 test. Grading of the embolic events and possible confounders were analyzed using a multivariate analysis of variance for repeated measures. A P ⱕ .05 was Embolic events observed and graded on transesophageal echocardiography. A, Grade 0 embolization and absence of emboli passing through the heart. B, Grade I embolization and a limited number (⬍10 per field of view) of small particles in the RA, RV, and RVOT. C, Grade II embolization and moderate amount of small particles (10-20 per field of view). D, Grade III embolization and many small particles (⬎20 per field of view). E, Grade IV embolization and many small and large particles (⬎20 per field of view) completely filling the diameter of RA, RV, and RVOT. RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract. Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
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TABLE 1
Demographic, clinical and intraoperative characteristics Monopolar group (n ⴝ 24)
Variable
Bipolar group (n ⴝ 22)
Age, y
45.5 ⫾ 7.0
43.7 ⫾ 7.4
Weight, kg
73.0 ⫾ 14.2
71.4 ⫾ 13.2
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
168.9 ⫾ 6.4
Height, cm
166.1 ⫾ 5.9
..............................................................................................................................................................................................................................................
ASA (1/2)
16/8
17/5
Para status 0/1/2/3 or more
12/2/7/3
10/4/6/2
6 (25%)
8 (36%)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
Hormonal therapy
..............................................................................................................................................................................................................................................
TCR-M/TCR-E
15/10
19/5
..............................................................................................................................................................................................................................................
Myoma, cm
2.9 (0–5) ⫾ 1.2
2.5 (1–4) ⫾ 0.8
Myoma class (0/1/2/3)
3/11/3/0
3/11/2/0
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
49.4 (24–180) ⫾ 29.4
Surgery, min
50.8 (30–90) ⫾ 15.1
..............................................................................................................................................................................................................................................
Data are mean (range) ⫾ SD or number (percentage). ASA, American Society of Anesthesiologists; TCR-M/TCR-E, transcervical resection of myoma/transcervical resection of endometrium. Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
considered statistically significant. All statistical analyses were performed using SPPS version 17.0 (SPSS Inc, Chicago, IL).
R ESULTS A total of 50 women were included: 40 patients scheduled for TCR-M and 10 patients scheduled for TCR-E. Four patients (3 bipolar, 1 monopolar) were excluded in the final analysis, 2 because of loss of the TEE-images and 2 because no abnormalities were observed during the procedure, and only a diagnostic hysteroscopy was performed. There were no statistically significant differences with respect to the patient demographic, obstetric, relevant gynecological, and intraoperative characteristics between the study groups (Table 1). One
patient in the monopolar and 2 patients in the bipolar group underwent a TCR-M as well as a TCR-E procedure. VGE were observed in all but 1 patient. Significantly more grade IV VGE was observed during bipolar diathermia (*, P ⫽ .05). The total number and percentage of patients experiencing different grades of VGE are shown in Table 2. In addition, the different grades of VGE were associated with the amount of intravasation in each group. No VGE was observed at levels of intravasation below 240 mL. The relationship of the grade of VGE with intravasation at a cutoff point of 1000 mL is demonstrated in Table 3. Significantly more grade IV VGE was observed if intravasation exceeded 1000 mL (P ⫽ .049). In the bipolar group, 7 pa-
tients (32%), and in the monopolar group 5 patients (21%) experienced intravasation above 1000 mL. The incidence of cardiovascular disturbances and cardiovascular instability, which resulted from VGE was the same in both groups. The number of patients in each group that experienced cardiovascular symptoms is shown in Table 4. In none of the patients was ventricular arrhythmia observed. However, a systolic blood pressure decrease exceeding 25% of baseline was noticed in 33% of the patients if both groups were combined. Seven of 13 patients with grade IV VGE showed a drop in end-tidal CO2. In these 7 patients, ST-segment changes were observed in 91.6 %. Pre- and postoperatively, no interventions for cardiovascular instability were needed. Major complications with overt cardiovascular collapse were not observed in any of the patients, even with high grades of VGE. Paradoxical embolism was observed in 2 patients (4.3% of all patients), both in the bipolar group, at an intravasation of 300 and 2300 mL, respectively. In these 2 patients, no changes in cardiovascular measurements that might result from VGE were observed.
C OMMENT In the present study, the difference in incidence and grade of venous gas embolism between monopolar and bipolar operative hysteroscopy was compared and related to the amount of intravasation of distension fluid. VGE was observed in almost every patient (98%) using either monopolar or bipolar diathermia. Bipolar diathermia was associated with a significantly higher incidence of
TABLE 2
Distribution of venous gas embolism (grade 0-IV) among patients and related amount of intravasation Variable
Grade 0
Monopolar, n (%)
1 (4)
Intravasation, mL
240 (–)
Grade I
Grade II
Grade III
Grade IV
7 (29)
7 (29)
6 (25)
3 (12)
................................................................................................................................................................................................................................................................................................................................................................................ a
378 (0–1400)
620 (250–800)
967 (600–1200)
1215 (30–1700)
................................................................................................................................................................................................................................................................................................................................................................................ b
Bipolar, n (%)
0 (–)
1 (4)
6 (27)
5 (23)
10 (45)
................................................................................................................................................................................................................................................................................................................................................................................ a
Intravasation, mL
500 (–)
474 (100–670)
833 (200–2300)
950 (200–2000)
................................................................................................................................................................................................................................................................................................................................................................................ a
Data presented as mean (range); b P ⫽ .031.
Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
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www.AJOG.org VGE grade IV; 42% of the patients with bipolar diathermia experienced grade IV VGE. When the amount of intravasation was related to the grade of VGE, significantly more grade IV VGE was observed in the patients with intravasation greater than 1000 mL. The present finding of the high incidence of venous gas embolism is in agreement with a recent study in patients who underwent an operative hysteroscopy.12 In that study, gas bubbles could be demonstrated in the right atrium in all patients, and a continuous flow of bubbles was observed in 85% of the patients, as monitored by transthoracic echocardiography. Although monopolar diathermia is associated with more gas production compared with bipolar diathermia in in vitro experimental studies,10 more grade IV VGE was observed in the bipolar group in the present study. This might be attributed to the larger gaseous particles produced by bipolar diathermia.8,9 Because the composition of the gas bubbles (hydrogen, carbon monoxide, and carbon dioxide) appears to be the same using either monopolar or bipolar diathermia,8,9 the bigger particles that arise during bipolar diathermia are less likely to dissolve before they reach the heart. The higher incidence of grade IV in the bipolar group can also be explained by the higher level of intravasation in the bipolar group. When intravasation exceeded 1000 mL, higher grades of VGE were observed, irrespective of the type of distension fluid used. It is reasonable to assume that gaseous products of hysteroscopic electro surgery and intravasation fluid enter the circulation simultaneously through the surgically opened veins in the myometrium. As a result, an increase of intravasation will lead to an increase of gaseous emboli that enter the circulation. Indeed, the relation between intravasation and grade of VGE has been noticed before.7 Some technical differences between monopolar and bipolar resectoscopy have to be considered. We have used monopolar resectoscopes with a bigger loop diameter compared with the bipolar resectoscopes, which may shorten operating room time in case of monopolar
Research
TABLE 3
Relationship of intravasation >1000 mL with the grade of venous gas embolism (all patients of both groups combined) Variable
Grade 0
Grade I
Grade II
Grade III
Grade IV
⬍1000 mL, n (%) (34 patients)
2 (6)
6 (18)
13 (38)
6 (18)
7 (20)
⬎1000 mL, n (%) (12 patients)
0 (0)
1 (8)
0 (0)
5 (41)
6 (50)
.086
.049
.............................................................................................................................................................................................................................................. a a .............................................................................................................................................................................................................................................. a a
P value
.743
.113
.012
.............................................................................................................................................................................................................................................. a
P values compared to patients with ⬍1000 mL intravasation.
Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
surgery and reduce the amount of gas bubbles. However, the size and class of the myoma as well as the operating room time were not significantly different between the monopolar and bipolar group. The energy dispersed from the loop into the tissue may differ between monopolar and bipolar surgery and may influence gas bubble formation. The Erbe VIO generator, although limited in different amount of watts in the mono- and bipolar settings, provides a variable amount of power, depending on the amount of tissue that is in contact with the loop. Energy delivery from a monoor bipolar loop is therefore a very inconsistent factor throughout the procedure but may indeed influence the formation of gas. Increased coagulation may enhance closure of the veins and therefore limit the access of bubbles into the blood stream. The same counts for the reduction of insufflation pressure. Both are interesting subjects for future studies. The present study has several limitations. Although it is a prospective randomized clinical trial, the study was open to the principal investigator and the op-
erating gynecologist. However, any bias caused by not blinding the primary investigator is unlikely to have influenced the results because an independent cardiologist reviewed the TEE images. Videorecordings with the TEE-probe were made at set times and not continuously. Therefore, higher grades of VGE might have been underestimated. The observed VGE might not only be the result of electrosurgery. Room air can also enter the circulation during the process of removing and reinserting the scope, which acts as a piston in the vaginal cylinder to force air in the open uterine veins. Indeed, 1 patient in the present study demonstrated grade IV VGE during introduction of the resectoscope, without electrosurgery. This was also reported by Corson et al,13 who described 2 patients who died, apparently because room air entered the circulation through surgically exposed blood vessels. The composition of room air does not allow it to dissolve rapidly, which might augment the TEE image and worsen the clinical consequences.
TABLE 4
Clinical parameters changes that might be the result of a venous gas embolism Variables
Monopolar group (n ⴝ 24)
Bipolar group (n ⴝ 22)
EtCO drop ⬎20%
n ⫽ 4 (17%)
n ⫽ 4 (18%)
RR systolic drop ⬎25%
n ⫽ 6 (25%)
n ⫽ 9 (40%)
ST-segment depression ⬎2 mm
n ⫽ 4 (17%)
n ⫽ 6 (18%)
Cardiovascular instability
n ⫽ 4 (17%)
n ⫽ 4 (18%)
2 .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. .............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
EtCO2, end-tidal carbon dioxide pressure; RR, Riva Rocci blood pressure; ST-segment, electrocardiographic change. Dyrbye. Gas embolism and intravasation during hysteroscopic surgery uses either monopolar or bipolar diathermia. Am J Obstet Gynecol 2012.
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Clinical symptoms related to the occurrence of VGE are determined by the volume of gas entrainment and the rate of accumulation. A relatively large volume of gas that enters the circulation rapidly or a small volume entering over a longer period of time can give physiological changes.14 Most of the symptoms that occur during an embolic event are attributed to the direct effects of venous emboli, such as air lock in the right ventricle.4,15,16 The symptoms of VGE in an anesthetized patient are the following: a decrease in end-tidal CO2, hypoxia, electrocardiographic changes, hypotension, electromechanical dissociation, and asystole. The most sensitive monitoring device for venous embolism is the TEE, which detects as little as 0.02 mL/kg of air administered by bolus injection.14 In the present study, no major complications with overt cardiovascular collapse were seen. Because only ASA 1 and 2 patients were included, this may underestimate the cardiorespiratory consequences of VGE. The incidence of cardiovascular instability with a decrease in blood pressure and lowered levels of end-tidal CO2 was similar in both groups. More than 90% of our patients with grade IV emboli showed ST-II segment changes that indicate right ventricular strain.17 ST-II changes can also be explained by paradoxical embolism through an open foramen ovale or through patent pulmonary pathways and consequently a disruption of right coronary artery blood flow.18 In the present study, paradoxical embolism was observed in 2 patients. An episode of severe VGE that exceeds the capacity of lungs to filter emboli may also result in paradoxical embolism.19 Paradoxical embolism can result in serious neurological and cardiac complications. The overall incidence of 28% of severe, grade IV VGE raises concern in that respect. The results of the present study do not favor either mono- or bipolar diathermia. Although significantly more grade IV VGE was observed during bipolar diathermia, this can not be attributed exclusively to the use of the bipolar diathermia. The higher level of intravasation of isotonic distension fluid (up to 2500 mL)
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that is accepted during bipolar diathermia might be an important factor. Although the results of the present study question the liberal acceptance of intravasation of up to 2500 mL using bipolar diathermia, they do not justify a lower acceptable level of intravasation. However, irrespective of the type of diathermia, caution is warranted for the occurrence of extensive VGE if intravasation exceeds 1000 mL. If intravasation exceeds 1000 mL, the procedure should be terminated immediately as soon as any sign of gas embolism occurs, using routine monitoring including an electrocardiogram, end-tidal CO2, blood pressure, and saturation. Future studies are needed to confirm the relationship of VGE and intravasation of distension fluid with cardiopulmonary symptoms and minor clinical symptoms such as fatigue, nausea, and vomiting, which may slow down postoperative recovery. In conclusion, during hysteroscopic electro surgery venous gas embolism occurred in almost every patient in both monopolar and bipolar groups. More extensive embolism was observed when intravasation exceeded 1 L. The acceptance of intravasation of up to 2500 mL of normal saline during bipolar diathermia is questioned. f ACKNOWLEDGMENTS We acknowledge with great appreciation Lea Dijksma and Marieke Kluut (currently affiliated with the Department of Anaesthesiology, St Radboud, Nijmegen, The Netherlands) for their contributions while preparing the protocol and the manuscript.
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www.AJOG.org 5. Paschopoulos M, Polyzos NP, Lavasidis LG, Vrekoussis T, Dalkalitsis N, Paraskevaidis E. Safety issues of hysteroscopic surgery. Ann N Y Acad Sci 2006;1092:229-34. 6. Loffer FD, Bradley LD, Brill AI, Brooks PG, Cooper JM. Hysteroscopic fluid monitoring guidelines. The ad hoc committee on hysteroscopic training guidelines of the American Association of Gynecologic Laparoscopists. J Am Assoc Gynecol Laparosc 2000;7:167-8. 7. Rademaker BMP, Kesteren van PJM, Haan de P, Rademaker D, France C. How safe is the intravasation limit in hysteroscopic surgery? J Minim Invasive Gynecol 2011;18:355-61. 8. Munro MG, Weisberg M, Rubinstein E. Gas and air embolization during hysteroscopic electrosurgical vaporization: comparison of gas generation using bipolar and monopolar electrodes in an experimental model. J Am Assoc Gynecol Laparosc 2001;8:488-94. 9. Farrugia M, Hussain SY, Perett D. Particulate matter generated during monopolar and bipolar hysteroscopic human uterine tissue vaporization. J Minim Invasive Gynecol 2009;16:458-64. 10. Munro MG, Brill AI, Ryan T, Ciarrocca S. Electrosurgery-induced generation of gases: comparison of in vitro rates of production using bipolar and monopolar electrodes. J Am Assoc Gynecol Laparosc 2003;10:252-9. 11. Wamsteker K, Emanuel MH, de Kruif JH. Transcervical hysteroscopic resection of submucous fibroids for abnormal uterine bleeding: results regarding the degree of intramural extension. Obstet Gynecol 1993;82:736-40. 12. Imasogie N, Crago R, Leyland NA, Ghung F. Probable gas embolism during operative hysteroscopy caused by products of combustion. Can J Anesth 2002;49:1044-7. 13. Corson SL, Brooks PG, Soderstrom RM. Gynecologic endoscopic gas embolism. Fertil Steril 1996;65:529-33. 14. Mirski MA, Lele AV, Fitzsimmons L, Toung TJK. Diagnosis and treatment of vascular air embolism. Anesthesiology 2007;106:164-77. 15. Mushambi MC, Williamson K. Anaesthetic considerations for hysteroscopic surgery. Best Pract Res Clin Anesthesiol 2002;16:35-51. 16. Groenman FA, Peters LW, Rademaker BMP, Bakkum EA. Embolism of air and gas in hysteroscopic procedures: pathophysiology and implications for daily practice. J Minim Invasive Gynecol 2008;15:241-7. 17. Leibowitz D, Beshalom N, Kaganov Y, Rott D, Hurwitz A, Hamani Y. The incidence and haemodynamic significance of gas emboli during operative hysteroscopy: a prospective echocardiographic study. Eur J Echocardiogr 2010;11:429-31. 18. Ghimouz A, Loisel B, Kheyar M, Fried D, Bouret JM. Carbon dioxide embolism during hysteroscopy followed by transient blindness. Ann Fr Anesth Reanim 1996;15:192-5. 19. Rademaker B, Groenman F, van der Wouw P, Bakkum E. Paradoxical gas embolism by transpulmonary passage of venous emboli during hysteroscopic surgery: a case report and discussion. Br J Anaesth 2008;101:230-3.