For standard operative hysteroscopy with monopolar radiofrequency resectoscopes, low-viscosity, nonconductive ﬂuids such as 1.5% glycine, 3% sorbitol, and 5.0% mannitol are used most often. These solutions can be used with standard, monopolar radiofrequency instrumentation because there are no electrolytes to disperse the current and impede the electrosurgical effect. Each of these media is inexpensive and readily available, usually in 3-L bags suitable for continuous-ﬂow hysteroscopy. Because each ﬂuid is electrolyte-free, extravasation into the systemic circulation can be associated with electrolyte disturbances. Compared with 1.5% glycine or 3.0% sorbitol, 5% mannitol is isomolar and it functions as a diuretic, both advantages when performing resectoscopic surgery. Regardless of the electrolyte content of the ﬂuid distending media, systemic “absorption” must be monitored continuously or at least frequently (every 5 minutes) by collecting outﬂow from the sheath and subtracting it from the total infused volume. The fact that the manufacturer frequently fills the bags with more than the indicated 3 L makes accurate calculation of absorbed volume even more difficult (217). There are a number of machines designed to provide continuous feedback to the surgeon regarding the degree of negative ﬂuid balance. Absorbed volumes greater than 1 L mandate the measurement of electrolyte levels. The risk of ﬂuid overload is reduced by the judicious restriction of intravenous ﬂuid by the anesthesiologist. The administration of an appropriate dose of furosemide should be considered, and the surgeon should plan for the expeditious completion of the procedure. If there is more than a preset limit (1.5 to2Lofextravasated ﬂuid), the procedure should be stopped. Excessive circulating sorbitol may cause hyperglycemia, and large volumes of glycine may elevate levels of ammonia in the blood (218).
Syringes can be used for office diagnostic procedures and are especially good for infusing dextran solution. The syringe can be operated by the surgeon and is either connected directly to the sheath or attached by connecting tubing. Because this technique is so tedious, it is suited only for simple operations.
Continuous hydrostatic pressure is effectively achieved by elevating the vehicle containing the distention media above the level of the patient’s uterus. The achieved pressure is the product of the width of the connecting tubing and the elevation—for operative hysteroscopy with 10-mm tubing, intrauterine pressure ranges from 70 to 100 mm Hg when the bag is between 1 to 1.5 m above the uterine cavity.
A pressure cuff may be placed around the infusion bag to elevate the pressure in the system. Caution must be exercised because this technique causes increasing extravasation if intrauterine pressure rises above the mean arterial pressure.
A variety of infusion pumps is available, ranging from simple devices to instruments that maintain a preset intrauterine pressure. Simple pump devices continue to press ﬂuid into the uterine cavity regardless of resistance, whereas the pressure-sensitive pumps reduce the ﬂow rate when the preset level is reached, thereby impeding the efﬂux of blood and debris and compromising the view.