Version May 2024
INTRODUCTION — Hysteroscopy is a procedure in which a telescope is used to inspect the cervical canal and uterine cavity. This technology has provided a minimally invasive option for diagnosis or treatment of women with common gynecologic issues, such as abnormal uterine bleeding or uterine fibroids.
Use of and prevention and management of complications from hysteroscopic distending media will be reviewed here. Other hysteroscopic topics are discussed in detail separately. (See "Overview of hysteroscopy".)
In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we encourage the reader to consider the specific counseling and treatment needs of transgender and gender diverse individuals.
TYPES OF HYSTEROSCOPY — Panoramic hysteroscopy is the most common method. A uterine distending medium is used to allow a global view of the endometrial cavity. Carbon dioxide and low-viscosity fluids are the most frequently used distending media. Each medium has advantages and disadvantages, including specific safety concerns. (See "Overview of hysteroscopy".)
Contact hysteroscopy is another method, but it is rarely performed. Since no distending medium is used, only tissue in direct contact with the scope can be viewed [1].
CHARACTERISTICS OF DISTENDING MEDIA — Types of media, biochemical properties, adverse effects, and safety measures are summarized in the table (table 1).
Ideal characteristics — Ideal characteristics of a distending medium are:
●Allows clear visualization
●Nonconductive (to avoid electrocautery-related injury)
●Inexpensive
Since distending media are absorbed, a medium should also be:
●Nontoxic
●Hypoallergenic
●Non-hemolytic
●Isoosmolar
●Rapidly cleared from the body
Fluid media — Low-viscosity fluids are used for uterine distension during hysteroscopy. High-viscosity fluids (ie, 32 percent dextran 70 [Hyskon]) are no longer used because they are associated with increased risk of complications (eg, electrolyte imbalance, anaphylaxis, and disseminated intravascular coagulation) and can ruin expensive hysteroscopic equipment [2-4].
Fluid distending media may be either electrolyte (eg, normal saline, lactated Ringer's) or electrolyte-poor (eg, glycine, sorbitol, mannitol) [4]. The choice of fluid type depends upon whether a diagnostic or operative procedure is planned and on the surgeon's choice of equipment (ie, monopolar or bipolar energy source). Each type of fluid can result in complications if not used properly. (See 'Complications and adverse effects' below.)
Electrolyte — There are two types of low-viscosity distending media: those that contain electrolytes and those that do not. The electrolyte-containing media include normal saline and lactated Ringer's solution and cannot be used with monopolar electrosurgery because they conduct electric current (but can be used with mechanical morcellators, mechanical tissue removal systems, laser, or bipolar energy). The electrolyte-poor solutions are 5 percent dextrose, 1.5 percent glycine, 3 percent sorbitol and 5 percent mannitol, and are used with monopolar energy systems.
The electrolyte fluids used for hysteroscopy are isoosmolar (isotonic), and thus do not disturb the osmolar balance between intracellular and extracellular fluid. While the risks of fluid absorption are associated mainly with electrolyte-poor fluids, intravasation of large volumes of electrolyte fluid can also lead to fluid overload (eg, pulmonary edema or congestive heart failure) [5].
Electrolyte-poor — The electrolyte-poor fluids that are used most commonly for hysteroscopy are: 1.5 percent glycine, 3 percent sorbitol, 5 percent mannitol. Each has different properties and is metabolized by a different mechanism (table 1). The physiology of these fluids is discussed in detail separately. (See "Hyponatremia following transurethral resection, hysteroscopy, or other procedures involving electrolyte-free irrigation".)
All the electrolyte-poor fluids used in hysteroscopy can lead to hyponatremia if a large volume is absorbed. Mannitol differs from the others because it is isoosmolar, but is not commonly used because it is not available in the 3 L bags typically used for hysteroscopy.
Inflow and monitoring — Inflow and monitoring are controlled by the hysteroscope and a continuous fluid monitoring device. The surgeon should be frequently updated regarding the fluid deficit, particularly when the deficit approaches 500 mL. (See 'Diagnosis and management of fluid overload' below.)
We prefer a hysteroscope that has a dual outer sheath or dual port system with an outflow port that can be directly connected to a vacuum collecting system. This gives an accurate assessment of the fluid deficit, as less media is lost in the drapes, towels, or on the operating room floor.
Use of an automated fluid pump and monitoring system is advocated by the American College of Obstetricians and Gynecologists, American Association of Gynecologic Laparoscopists, and by the British Society for Gynaecological Endoscopy and European Society for Gynaecological Endoscopy with long procedures, such as endometrial resection or myomectomy [4,6,7]. Automated systems have the following advantages over manual set-ups:
●Continually measure fluid deficit and provide automated alerts
●Automated cessation of inflow of fluid when the fluid deficit is reached
●Measurement and titration of intrauterine fluid pressure
●Decreases risk of air emboli
Most automated hysteroscopic pump systems allow you to set the desired intrauterine pressure manually, and the system will then adjust the flow of fluid to maintain this pressure. In addition, automated pump systems should be set to give audible alerts at when the pre-set fluid deficit is reached.
Titrating intrauterine pressure is important to manage bleeding, facilitate full resection of endometrial lesions, and decrease "false negative" views of the endometrial cavity that may occur with higher or constant endometrial pressure. The surgeon should use the lowest pressure that allows optimal visualization. Typically, intrauterine pressure ranges from 70 to 80 mmHg. Higher pressures (up to 125 to 150 mmHg) may be required for patients with intrauterine bleeding, large intracavitary blood clots, or other debris; a uterine wall that is less compliant than average; or a uterus that is large and/or has intramural fibroids. A higher intrauterine pressure may result in increased absorption or extravasation of the distending medium. Thus, if a higher pressure is used, the fluid deficit should be monitored closely, the procedure should be performed as quickly as possible, and the pressure should be lowered if the higher pressure is no longer needed. (See "Hyponatremia following transurethral resection, hysteroscopy, or other procedures involving electrolyte-free irrigation", section on 'Minimize fluid pressure'.)
Where automated systems are not available, a manual technique is used. Fluid is infused using the force of gravity (ie, elevating the fluid bag) or by placing the fluid bag in a large blood pressure cuff and inflating the cuff. Fluid input and output are recorded manually.
A surgical staff member should be designated to frequently measure the input and output and report the deficit to the surgeon. To record fluid input manually, the volume of fluid in each bag must be known. Some surgeons make calculations based on the common assertion that fluid bags are generally overfilled by 10 percent or more (eg, a 1000 mL bag of normal saline is considered to have 1100 mL or more); this leads to an overestimate of the fluid deficit. However, a study of bags of normal saline, glycine, and sorbitol found that the average overfill was only 3 to 6 percent of the bag volume [8]. (See 'Fluid overload' below.)
To avoid hypothermia during longer procedures (ie, operative versus diagnostic hysteroscopy), fluid distending media can be warmed to room temperature at a minimum; hypothermia may potentiate the risk of acidemia and cardiac arrhythmias [9,10].
Gaseous media — Carbon dioxide is the only gaseous medium used in hysteroscopy; it is used solely for diagnostic hysteroscopy [4]. It provides a clear field of view, is rapidly absorbed, and has a long history of safety in tubal patency testing [11]; it is also widely available and makes cleaning of instruments easy. However, it is best suited for diagnostic rather than operative hysteroscopy, since gas bubbles form in association with intrauterine bleeding and impair visualization [12].
Carbon dioxide must be insufflated with a special instrument known as a hysteroinsufflator. It has a maximum insufflation of 100 mmHg/minute. A laparoscopic insufflator should never be used, as it can insufflate greater than 1 L CO2/minute. (See 'Prevention of gas embolism' below.)
Effects on operative visualization — The angle of view and magnification vary with the refractory index of the distending medium. Gaseous media (eg, carbon dioxide) allow perception of the maximal angle of view, while liquid media reduce the angle of view [13]. Use of gaseous media is usually limited to diagnostic procedures, since gas bubble may interfere with visualization [14].
COMPLICATIONS AND ADVERSE EFFECTS
Fluid overload — Fluid overload is rare, occurring in 0.06 to 0.2 percent of operative hysteroscopy procedures [15,16]. Complications related to distending media vary according to the patient population, length of procedure, size of intracavitary pathology, depth of fibroid penetration into the myometrium, creation of false tracks or cervical laceration, uterine perforation, type of pathology (polyp versus fibroid), and the medium used.
A patient's ability to adapt to fluid overload varies with age and comorbid conditions. Absorption of large volumes of electrolyte-poor fluid may result in the following complications:
●Volume overload – Acute decompensated heart failure, pulmonary edema, laryngeal edema, dilutional anemia
●Electrolyte or other plasma imbalance – Hyponatremia, hypoosmolality, hyperammonemia, hyperglycemia, acidosis
●Neurologic sequelae – Slurred speech, visual disturbances, hypersomnia, confusion, seizures, coma
During hysteroscopy, absorption is increased when venous sinuses are exposed (eg, during myomectomy with Type 1 and Type 2 leiomyomas, endomyometrial resection, septum resection that is too deep, difficult Asherman's syndrome cases). In addition, minimal fluid extravasates through the Fallopian tubes; history of prior sterilization does not alter total absorption [17,18].
Hyponatremia is a particular risk with electrolyte-poor fluids. This topic is discussed in detail separately. (See "Hyponatremia following transurethral resection, hysteroscopy, or other procedures involving electrolyte-free irrigation".)
Prevention of fluid overload — Fluid overload and electrolyte imbalance can be prevented by following several operative principles (see 'Fluid media' above):
●Use isoosmolar, electrolyte fluids whenever possible.
●Limit the amount of preoperative intravenous fluids.
●Advise anesthesia to minimize intra-operative fluids, especially when large myomas or deep hysteroscopic resection is anticipated.
●Monitor fluid deficit closely and halt the procedure and evaluate for fluid-related complications at pre-set thresholds [19].
●Maintain the lowest intrauterine fluid pressure to achieve excellent visualization. Know the patient’s mean arterial pressure (MAP), because the intrauterine pressure will need to be higher than the MAP to achieve excellent visualization. While in general intrauterine fluid pressure set at or 70 to 80 mmHg will achieve this, higher pressure up to 125 to 150 mmHg may be required [20].
●Limit surgical time to <1 hour [21].
These measures are discussed in detail separately. (See "Hyponatremia following transurethral resection, hysteroscopy, or other procedures involving electrolyte-free irrigation", section on 'Prevention'.)
Measures specific to hysteroscopy for prevention of excessive fluid absorption include use of a vasoconstrictor. This was illustrated in randomized trials in women undergoing operative hysteroscopy [21-23]. Intracervical injections of a dilute vasopressin solution (eg, 1 unit per 20 mL normal saline) at two sites around the cervix, 10 mL each, before the procedure compared with placebo resulted in a threefold decrease in fluid absorption. Blood loss was also decreased.
Other methods of limiting fluid absorption during hysteroscopy have not been widely adopted. Treatment with a gonadotropin-releasing hormone analog reduced deficits in one small randomized trial (n = 17), however, these results have not been further evaluated and the side effects (eg, hot flashes, mood changes, and costs) induced by these drugs may outweigh possible benefits [24].
Diagnosis and management of fluid overload — Serious complications of electrolyte-poor fluid overload have been reported at a fluid deficit of 500 to 1000 mL and are more likely to occur in patients with comorbidities (eg, heart and renal disease) and advanced age [25]. Thus, depending upon the type of fluid used and the health status of the patient, when the fluid deficit reaches 500 mL, the surgical team should pause and assess patient status. After estimating the amount of time necessary to complete the procedure, the team should either expedite the completion of the procedure or terminate the procedure.
For nonconductive, electrolyte-poor fluids, the procedure should be terminated when 1000 mL has been absorbed and the patient evaluated for hyponatremia. (See "Hyponatremia following transurethral resection, hysteroscopy, or other procedures involving electrolyte-free irrigation", section on 'Prevention'.)
For electrolyte-containing media, the criteria for terminating a procedure are [26]:
●2500 mL for younger patients with no comorbidities; some data suggest that fluid intravasation of >1000 mL is associated with an increased risk of gas embolism [27]. (See 'Gas embolism' below.)
●For other patients, the threshold must be individualized according to cardiovascular status or other comorbidities. A limit of 750 mL may be needed [25].
Terminating the infusion at lower thresholds is reasonable in outpatient settings with limited acute care and laboratory services. In addition, all procedures should be terminated if uterine perforation occurs, since large volumes of fluid may rapidly enter the circulation via the peritoneal cavity, cause compression on great vessels, and respiratory compromise [17]. (See "Uterine perforation during gynecologic procedures".)
If a criterion for stopping a procedure is met, the following steps should be taken to evaluate the patient:
(1) Halt procedure – Discontinue fluid inflow, remove all instruments; if there is active bleeding, a 10 to 30 mL Foley catheter can be inserted in the uterine cavity, inflated, and removed after six to eight hours if the patient is hemodynamically stable and bleeding has stopped. A larger intrauterine balloon for postpartum hemorrhage (eg, Bakri balloon, BT-cath) may be required if the uterus is larger because of fibroids or adenomyosis. Overdistension of the intrauterine cavity should be avoided to minimize the risk of uterine rupture.
(2) Ask about symptoms of volume overload, hyponatremia, or glycine toxicity (in patients who are not under sedation or general anesthesia) – Nausea, headache, visual disturbance, prickling or burning sensation in the face and neck, chest pain, shortness of breath [17]. If present, rapidly administer IV Lasix for fluid overload and monitor urine output for diuresis.
(3) Evaluate hemodynamic status – Vital signs, central venous pressure, oxygen saturation.
(4) Evaluate mental, respiratory, and cardiovascular status.
(5) Perform laboratory evaluation – Hematocrit, platelets, blood urea nitrogen, creatinine, sodium, potassium, bicarbonate, chloride, glucose, ammonia (glycine is metabolized to ammonia), and plasma osmolality.
Evaluation of the patient should be individualized according to a patient's comorbidities. For example, there is a higher risk of sequelae from metabolism of glycine to ammonia in a patient with liver disease. The metabolites of each distending medium are listed in the table (table 1).
Patients who have an excessive fluid deficit but show no signs or symptoms of fluid overload can be observed, but this observation must be continued postoperatively. Alternatively, IV Lasix can be administered in an anticipatory manner. Plasma dilution peaks at approximately 15 to 20 minutes after fluid infusion, but fluid and electrolyte shifts continue for several hours afterward [17].
If a fluid-related complication is suspected, an intraoperative management plan must be initiated by the surgeon and anesthesiologist. Depending on the degree of fluid overload or electrolyte imbalance, management may include observation, diuresis, intravenous administration of corrective fluids (eg, hypertonic saline), or hemodialysis. Consultation with a nephrologist or cardiologist, or transfer of the patient to a critical care setting, may be necessary.
Gas embolism — Clinically significant gas embolism appears to occur frequently in patients undergoing operative hysteroscopy [27,28]. Gas embolism may result in cardiovascular collapse or pulmonary edema, but few hysteroscopy patients experience clinically significant cardiac or pulmonary complications. (See "Air embolism".)
Gas embolism may result from use of carbon dioxide for distension. It may also occur with either gas or fluid media with introduction of air through the open cervix or with removal and reinsertion of instruments or tissue or, alternatively, through creation of gas bubbles with electrosurgical vaporization of tissue [5,27]. Gas embolism can cause cardiovascular collapse [29].
Prevention of gas embolism — Preventive steps for gas embolism during hysteroscopy include [30]:
●Keep the patient in flat or reverse Trendelenburg position
●Do not utilize Trendelenburg position
●Avoid use of nitrous oxide for anesthesia (this may enlarge air bubbles)
●Purge air from all tubing prior to insertion into the uterus
●Maintain intrauterine pressure at <125 to 150 mmHg. Start with the intrauterine pressure on the fluid pump at equivalent to the mean arterial pressure and increase to no more than 125 to 150 mmHg
●Limit removal and re-introduction of the hysteroscope (this may force air or gas into the uterus)
●Remove intrauterine gas bubbles (ideally with a continuous outflow system)
Limiting the distension fluid deficit may also be associated with a decrease in the risk of gas embolism, regardless of the type of fluid or type of electrosurgical instrument. This was illustrated in a randomized trial (n = 50) that found that use of either monopolar and bipolar electrosurgery for operative hysteroscopy resulted in evidence of intracardiac gas bubbles in nearly all patients, although no patients required treatment [27]. A subset analysis found that the likelihood of gas embolism was significantly higher with a fluid deficit of >1000 mL compared with <1000 mL.
Carbon dioxide must be insufflated with a special instrument known as a hysteroinsufflator. The laparoscopic insufflator delivers 1 L/min or more of flow and should NEVER be used for hysteroscopy, as a gas embolism may occur.
Hysteroinsufflators can be set to reach a target intrauterine pressure of less than 100 mmHg or to deliver a constant rate of flow of less than 100 mL/min [6,7,30,31].
Diagnosis and management of gas embolism — Dyspnea is the most common symptom; other signs and symptoms are listed in the table (table 2). A fall in a patient's end-tidal carbon dioxide pressure may raise intraoperative suspicion of gas embolism, but may also be present in other conditions [30].
If gas embolism is suspected, the procedure should be terminated immediately, the uterus deflated, and sources of fluid or gas removed [30].
Supportive care (eg, the use of mechanical ventilation, vasopressors, volume resuscitation as indicated) is the cornerstone of management, but active measures may also be helpful. (See "Air embolism".)
Shoulder pain — Infrequently, patients will complain of shoulder pain, likely due to diaphragmatic irritation from carbon dioxide. Symptoms usually subside in less than 15 minutes, without treatment [32]. The type of distension medium may affect the likelihood of shoulder pain. A systematic review of randomized trials found that shoulder pain was significantly reduced when normal saline was used compared with carbon dioxide (odds ratio 0.2; 95% CI 0.1-0.4) [14].
CHOOSING A DISTENDING MEDIUM — While diagnostic procedures can be performed using either carbon dioxide or normal saline, randomized trials have found that saline is associated with decreased pain, increased satisfaction, better visualization, and decreased operative time [11,14,31,33-35]. (See 'Shoulder pain' above.)
For operative procedures that utilize monopolar electrosurgical instruments, a nonconductive fluid (eg, glycine) is required to cut, coagulate, and dessicate tissue. Bipolar electrosurgical procedures may be performed using an isotonic fluid (eg, normal saline or lactated Ringer's), which avoids the risks of electrolyte and osmolar imbalances associated with nonconductive solutions.
Types of media, biochemical properties, adverse effects, and safety measures are summarized in the table (table 1).
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Hysteroscopy".)
SUMMARY AND RECOMMENDATIONS
●Distension media – Most simple diagnostic-only hysteroscopic procedures utilize a fluid or gaseous uterine distending medium to allow a global view. (See 'Characteristics of distending media' above and 'Choosing a distending medium' above.)
•Electrolyte-containing fluid media – Electrolyte-containing fluid media is utilized for mechanical hysteroscopic morcellators (tissue extraction devices) and bipolar hysteroscopy resectoscopes. (See 'Electrolyte' above.)
•Electrolyte-poor fluids – Electrolyte-poor fluids, including 1.5 percent glycine, 3 percent sorbitol, 5 percent mannitol, are used with monopolar systems. (See 'Electrolyte-poor' above.)
•Gaseous media – Carbon dioxide is the only gaseous medium used in hysteroscopy; it is used solely for diagnostic hysteroscopy. Use of carbon dioxide for uterine distension requires insufflation with a hysteroscopic insufflator. A laparoscopic insufflator should never be used because it can result in gas embolism. (See 'Gaseous media' above.)
●Absorption of distension media – Excessive absorption of any fluid medium can lead to complications of fluid overload. The most serious complication is intravasation of large volumes of electrolyte-poor media resulting in hyponatremia. (See 'Fluid overload' above.)
●Fluid monitoring – In women undergoing hysteroscopy using a fluid distending medium, we suggest using an automated rather than a manual fluid monitoring system (Grade 2C). (See 'Inflow and monitoring' above.)
●Approach to procedures:
•Electrolyte-poor media – In patients undergoing hysteroscopy using an electrolyte-poor fluid distending medium:
-For procedures that involve myometrial resection, we recommend an intracervical injection of dilute vasopressin immediately prior to the procedure (Grade 2B). (See 'Prevention of fluid overload' above.)
-We suggest halting the procedure at a fluid deficit of 1000 mL (Grade 2C). (See 'Diagnosis and management of fluid overload' above.)
•Electrolyte fluid – In patients undergoing hysteroscopy using an electrolyte fluid, we suggest halting the procedure at a fluid deficit of 2500 mL in those who are less than 50 years old and have no comorbid conditions (Grade 2C). For other patients, the threshold must be individualized according to cardiovascular status. (See 'Diagnosis and management of fluid overload' above.)
●Potential complications – Carbon dioxide or air embolism are rare complications of hysteroscopy. These may occur when carbon dioxide is used for distension, or also, if air bubbles are introduced while using fluid media. If gas embolism is suspected, the procedure should be terminated immediately, the uterus deflated, sources of fluid or gas removed, and supportive care provided. (See 'Gas embolism' above.)
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