There are a number of options available to facilitate cervical dilation. There is evidence that prostaglandin E1 (misoprostol) administered 400 μg orally or 200 to 400 μg vaginally, approximately 12 to 24 hours before the procedure facilitates cervical dilation (212–215). Misoprostol alone may not be effective in postmenopausal women, but one well-designed randomized trial demonstrated that vaginal estrogen, administered daily for 2 weeks before the procedure facilitates the effect of the prostaglandin in this group of patients (215). Alternatively, there is evidence that intraoperatively administered intracervical vasopressin (0.05 U/mL, 4 cc at 4 and 8 o’clock) substantially reduces the force required for cervical dilation (216). Regardless of the circumstance, the cervix should be dilated as atraumatically as possible. It is best to avoid using a uterine sound because it can traumatize the canal or the endometrium, causing unnecessary bleeding and uterine perforation.
Uterine Distention Distention of the endometrial cavity is necessary to create a viewing space. The choices include CO2 gas, high-viscosity 32% dextran 70, and a number of low-viscosity ﬂuids, including glycine, sorbitol, saline, and dextrose in water. A pressure of 45 mm Hg or higher is generally required for adequate distention of the uterine cavity and to visualize the tubal ostia. To minimize extravasation, this pressure should not exceed the mean arterial pressure. For each of the ﬂuids, there are several methods used to create this pressure by infusion into the endometrial cavity.
A rigid hysteroscope is passed into the endometrial cavity through an external sheath. The design and diameter of the sheath reﬂect both the dimensions of the endoscope and the purpose of the instrument. Typical diagnostic hysteroscopes have a sheath slightly wider than the telescope, allowing infusion of the distention media. Operative sheaths have additional channels to permit the passage or efﬂux of distention media and the insertion of laser fibers, electrosurgical instruments or semirigid scissors, biopsy devices, or grasping forceps. These sheaths are usually 5 to 8 mm in diameter, and some allow continuous ﬂow of distention media in and out of the endometrial cavity (Figs. 23.25 and 23.26).
CO2 provides an excellent view for diagnostic purposes, but it is unsuitable for operative hysteroscopy and for diagnostic procedures when the patient is bleeding because there is no effective way to remove blood and other debris from the endometrial cavity. To prevent CO2 embolus, the gas must be instilled by an insufﬂator that is specially designed for the procedure—the intrauterine pressure is kept below 100 mm Hg and the ﬂow rate is maintained at less than 100 mL per minute.
Figure 23.26 Hysteroscope optics. Panoramic (0◦) and oblique (15◦ and 30◦) viewing angles.
Normal saline is a useful and safe medium for procedures that do not require radiofrequency electricity from standard monopolar resectoscopes. Even if there is absorption of a substantial volume of solution, saline typically does not cause electrolyte imbalance.
Therefore, saline is a good ﬂuid for minor procedures performed in the office. The development of bipolar radiofrequency instrumentation for hysteroscopic surgery allowed the application of saline as a distending medium in even more advanced and complex procedures.
Dextran 70 is useful for patients who are bleeding because it does not mix with blood.
However, it is expensive and tends to “caramelize” on instruments, which must be disassembled and thoroughly cleaned in warm water immediately after each use. Anaphylactic reactions, ﬂuid overload, and electrolyte disturbances can occur.