Four basic types of distension media are used for hysteroscopy. The first type, CO₂, is used primarily for diagnostic hysteroscopy in an office setting. Secondly, a high-viscosity medium such as Hyskon is used primarily with inflow only–type hysteroscopes. The third and fourth types are both low-viscosity solutions that are used with continuous-flow hysteroscopes, electrolyte solutions, and non-electrolyte solutions. The choice between an electrolyte and non-electrolyte solution will depend on the use of monopolar versus bipolar electrocautery.

For diagnostic procedures in the office, some physicians choose CO₂ as the distension medium. CO₂ use requires a hysteroflator that delivers the gas at preset intrauterine pressures and has regulated flow rates. CO₂ may be used with either a small diagnostic rigid hysteroscope or a flexible hysteroscope and does not require a return channel for continuous flow, because the CO₂ gas will escape from the cervix or through patent fallopian tubes into the peritoneal cavity, where it is absorbed. Starting pressures for CO₂ are usually between 50 and 75 mm Hg. If adequate distension is not achieved, it may be necessary to increase the intrauterine pressure to a maximum of 100 mg Hg or a maximal flow of 100 mL per minute. Higher pressures or flow rates may produce a gas embolus, and rare fatalities have been reported. CO₂ will give an ideal view of the endometrial cavity that is not bleeding, because light reflection is identical to that of room air. However, any blood or mucus within the endometrial cavity will require changing to a liquid medium. Many physicians are routinely using low-viscosity solutions for office-based diagnostic procedures by using a large syringe as the delivery system. Since these procedures only take a few minutes to perform, larger volumes are not needed. Distention of the uterus can be controlled by varying the pressure on the syringe.

For many years, prior to the evolution of hysteroscopes that accommodate continuous flow, 32% high-molecular-weight dextran-70 (Hyskon) was commonly used as a liquid distension medium for operative hysteroscopy. Its nonmiscibility with blood allows its use when either blood or mucus is present in the endometrial cavity or bleeding is anticipated. Hyskon is compatible with either the Nd:YAG laser or electric cautery devices. When using Hyskon as the distension medium, its delivery requires significant constant pressure to overcome the resistance of a high-viscosity fluid flowing through the tubing and a standard diagnostic sheath. The major disadvantage of Hyskon is the difficulty in cleaning the solution from the instruments and stopcocks. If the instrumentation is not thoroughly cleaned, the dextran crystallizes and results in clouding of the hysteroscope lens and freezing of stopcocks. Rarely, patients may have an anaphylactic reaction to the dextran. Intravascular absorption of Hyskon results in a proportional 10-fold increase of intravascular volume, and if the absorbed volume is large, there may be accompanying cardiovascular overload and pulmonary edema. Careful monitoring of the amount of Hyskon intravasated during the procedure is mandatory, and absorption of 100 to 200 mL of Hyskon should warrant termination of the procedure. Because the molecular weight of Hyskon exceeds that which can pass into the circulation from the peritoneal cavity, spill through the fallopian tubes is inconsequential.

Operative hysteroscopy most commonly uses low-viscosity solutions, which can be either electrolyte solutions or non-electrolyte solutions. If monopolar resectoscopes are used, non-electrolyte solutions are required so that the flow of energy will be directed from the electrode tip into the tissue and not allowed to “short circuit” through an electrolyte-containing medium throughout the entire uterus. The electrolyte-free solutions that are used most often for operative hysteroscopy include 1.5% glycine, sorbitol, 5.0% mannitol, and dextrose in water. Significant intravasation of distension medium may occur with resectoscope use. As tissue is resected, venous channels within the endometrium and myometrium are opened, and the pressure of the distension medium will result in the absorption of these solutions. The primary complications associated with non-electrolyte low-viscosity solutions include fluid overload and hyponatremia. Fluid overload may result in pulmonary edema, and severe hyponatremia may result in neurologic sequelae such as confusion, seizures, and even death. Intraoperative monitoring of inflow and outflow must be performed every 5 to 10 minutes throughout the procedure, and a discrepancy between 500 and 1,000 mL with non-electrolyte solutions should warrant termination of the procedure. Glycine use has also been reported to cause hyperammonemia because of its conversion from glycine to ammonia by the liver.

Electrolyte solutions such as normal saline or lactated Ringer’s solution are used with bipolar electrical devices or for continuous-flow diagnostic hysteroscopy. Because bipolar devices contain both the active and return electrodes at the electrode tip, electrolytes are needed to complete the electrical circuit. The primary complication associated with electrolyte solutions is fluid overload, and a discrepancy of 1,500 to 2,000 mL during the procedure warrants termination of the procedure.

During operative hysteroscopy with significant operating time and use of large amounts of distension medium, the anesthesiologist should keep intravascular fluid replacement to a minimum to avoid fluid overload. Anesthesia personnel should also monitor the patient carefully for electrolyte abnormalities when using non-electrolyte solutions and anaphylactic shock under anesthesia when using Hyskon.

Hysteroscopy can be difficult to perform during the luteal phase because of the abundance of endometrial tissue. Performing hysteroscopy during the early to middle follicular phase should ensure adequate visualization of the uterine cavity. Alternatively, the endometrium can be suppressed with 2 to 4 weeks of progestin therapy, or hysteroscopy may be performed at any time in a patient taking oral contraceptives because of the dominant atrophy effect of progestin. Gonadotropin-releasing hormone (GnRH) analogues have most commonly been used to prepare the endometrium for endometrial ablation. At least 4 weeks of preoperative treatment are required for GnRH analogs such as leuprolide acetate (Depo-Lupron), because these medications are initially agonists and will actually increase estrogen output for the first 7 to 14 days before subsequent down-regulation of the pituitary ovarian axis and subsequent endometrial atrophy.

The cervix should be dilated no larger than the outer diameter of the hysteroscope that will be used. With many of the larger operative hysteroscopes, this will require dilation of the cervix to at least the diameter of a 20-French Hank dilator or a 9/10-French Hegar dilator. Care should be taken to avoid cervical lacerations and uterine perforation during cervical dilation. Preoperative treatment with intravaginal misoprostol can soften the cervix for easier dilation and may prevent cervical lacerations.

With insertion of the hysteroscope, the cervical canal can be visualized and the hysteroscope guided into the endometrial cavity under direct vision. If overdilation of the cervix has occurred and the distension medium cannot be retained within the endometrial cavity, an additional tenaculum may be placed on the posterior lip of the cervix or a special four-pronged tenaculum can be used to compress the cervix around the hysteroscope. The cervical canal and internal os will appear off center within the field of view when using offset-angle lenses. When the angle of the lens is oriented to look downward, the internal os will appear at the 12 o’clock position. If the telescope is inverted and the lens is pointed upward, the os will appear in the 6 o’clock position. The latter position is useful for viewing a retroverted uterus. The surgeon should always maintain the camera position in a straight up-and-down orientation so that the view on the screen corresponds anatomically to the patient’s position. As the hysteroscope is rotated to visualize the entire endometrial cavity, one hand should be kept on the camera to prevent its rotation; otherwise, the view on the monitor will be oriented improperly.