Cryotherapy is a time-proven, ablative method of treating lower grades of cervical dysplasia. The procedure is easy to learn, perform, and apply in outpatient settings. It works by freezing and killing abnormal tissue, which then sloughs off, and new tissue grows in its place. The tip of the cryoprobe is cooled by a refrigerant gas that is fed into the hollow cryoprobe under pressure. The gas then rapidly expands and absorbs heat in the process. The temperature of a nitrous oxide probe tip falls to -65°C to -85°C. A water-soluble lubricant is applied to the probe to act as a thermocouple with the irregular surface of the cervix. This produces a more uniform freeze. A rapid freeze followed by a slow thaw maximizes cryonecrosis, and a freeze-thaw-refreeze cycle is more effective than a single freeze.
After the cryoprobe is placed in contact with the cervix and activated, a ring of frozen tissue, or ice ball, extends outward. The depth of freeze approximates the lateral spread of the freeze. Cell death occurs when the temperature falls below -10°F. However, there is a ring of tissue (i.e., thermal injury or recovery zone) that freezes but does not reach the -10°F necessary for cell death. This is why it is necessary to freeze well beyond the margins of any lesions. Studies have demonstrated that endocervical crypt (gland) involvement of cervical intraepithelial neoplasia (CIN) may penetrate up to 3.8 mm into the cervix. A freeze that causes cell death to 4 mm should effectively eradicate 99.7% of lesions with gland involvement. Current recommendations are to produce an ice ball with a 5-mm lateral spread to accomplish this goal.
The cryotherapy appointment should be scheduled when the patient is not experiencing heavy menstrual flow. Select the largest speculum that the patient can comfortably tolerate, and open the blades and the front end of the speculum as widely as possible without discomfort. If collapsing side walls are a problem, place a condom with the tip cut off, the thumb from a very large rubber glove with the tip cut off, or one half of a Penrose drain over the speculum. Alternatively, tongue blades or side-wall retractors may be placed to improve exposure.
The choice of treatment modality for cervical dysplasia is at the discretion of the health care provider. The recent National Cancer Institute/American Society for Colposcopy and Cervical Pathology (NCI/ASCCP) consensus guidelines note that limited evidence supports any treatment modality for all grades of dysplasia. It is common practice in the United States to treat CIN 3 with excisional therapy
(e.g., loop electrosurgical excisional procedure [LEEP]) to discover occult microinvasive cancer. Advantages and disadvantages of cryotherapy appear in Table 38-1.
TABLE 38-1. ADVANTAGES AND DISADVANTAGES OF CRYOTHERAPY FOR CERVICAL INTRAEPITHELIAL NEOPLASIA
No anesthetic is required before cryotherapy because the procedure is relatively painless, although some cramping may occur. Some physicians recommend the use of nonsteroidal antiinflammatory drugs to decrease cramping. Submucosal injection of 1% lidocaine with 1:100,000 epinephrine can be administered to decrease local pain.
Although the data are not extensive, cryotherapy apparently has little effect on fertility, labor, or pregnancy outcome. The most common minor complication occurs if the probe touches the vaginal side wall and adheres to it. This causes pain, and slight bleeding may occur from the injured vaginal mucosa. Occasionally, a patient may experience an undue amount of pain and cramping, which is usually associated with a high level of anxiety. If this can be anticipated, a paracervical block before cryotherapy, oral or intramuscular administration of benzodiazepines (e.g., 1 mg of Ativan given intramuscularly), or intravenous sedation may be chosen for relief. These measures are seldom required.
Rarely, a patient may experience a vasovagal reaction. Allowing the patient to rest on the examination table after the procedure and to get up slowly is usually sufficient to overcome this problem. There has been a reported case of anaphylaxis due to cold urticaria. Some concern has been raised about occupational exposure to vented NO2 gas following cryotherapy, but the scientific evidence for harm is very weak.
The patient should refrain from sexual intercourse and tampon use for 3 weeks after cryotherapy to allow the cervix to reepithelialize. Excessive exercise also should likewise be discouraged to lessen the chance of bleeding after treatment.
Most patients experience a heavy and often odorous discharge for the first month after cryotherapy. About one half of women rate the postprocedure discharge and its odor worse than a normal period. This discharge results from the sloughing of dead tissue and exudate from the treatment site. Routine cervical eschar débridement does not shorten the duration or amount of discharge and offers no significant advantage. Amino-Cerv cream may be prescribed if a heavy discharge is present after the procedure, although there is no scientific evidence of efficacy. Approximately one third of patients restrict their activities because of side effects of the procedure.
The first follow-up Papanicolaou (Pap) smear should not be performed for 4 to 6 months. Cytology can be very confusing if sampled during the sloughing or regenerative phases, which take at least 3 months to complete. If the first two follow-up smears are normal, Pap smears can be repeated every 6 months for 2 years after treatment. Most recurrences take place within 2 years of treatment. Annual smears may be recommended after 2 years. An alternative follow-up schedule involves replacing the initial and each yearly Pap smear with a colposcopic examination. Unfortunately, patient compliance with serial cytology follow-up is suboptimal.
If any of the follow-up tests are positive, restart the workup as if there was a newly diagnosed, first-time dysplasia. Colposcopy with directed biopsy is usually indicated. Unfortunately, colposcopy after cryotherapy may be more difficult because of migration of the squamocolumnar junction deeper into the cervical os. Other treatment methods (usually LEEP) are preferred if persistent disease is discovered.
Informed consent is obtained. Perform a pregnancy test if there is any doubt about the patient's pregnancy status. Make sure that there is adequate pressure in the tank; usually, the needle is in the “green zone” on the pressure gage.
(1) Ensure that there is adequate pressure in the tank. The needle usually is in the “green zone” on the pressure gauge.
Place the patient in the dorsal lithotomy position, and place a vaginal speculum. Select a probe that adequately covers the entire lesion and the entire transformation zone. Use only flat-ended or short nipple-tipped probes, not probes with long endocervical extensions, because they cause more cervical stenosis. Apply a water-soluble lubricant to the probe to act as a thermocouple with the irregular surface of the cervix.
(2) Use only flat-ended or short nipple-tipped probes, not probes with long endocervical extensions because they cause more cervical stenosis.
Apply the probe firmly to the cervix, and make sure that it is not touching the side walls of the vagina. Start the freeze by pulling the cryogun trigger or pressing the freeze button. Within a few seconds, the probe will be frozen to the cervix. Using very light backward pressure on the cryogun, gently draw the cervix forward a few millimeters into the vagina, where probe contact with the side walls is less likely.
(3) Using very light backward pressure on the cryogun, gently draw the cervix forward a few millimeters into the vagina, where probe contact with the side walls is less likely.
PITFALL: Be careful not to allow the cryoprobe to touch the vaginal side wall, because it may stick to and freeze the vagina. The operator may quickly push the vaginal mucosa off the probe with a tongue blade or with a slight twist of the probe. If this is not done quickly, it will become more difficult as the freeze deepens, and more vaginal mucosa will be destroyed. The operator should defrost the probe just enough to release the sidewall and then continue the freeze.
A rim of ice should form and grow to a width of at least 5 mm in all quadrants. Discontinue the freeze. Release the cryogun trigger or press the defrost button. Wait until the probe visibly defrosts before attempting to disengage it from the cervix. The cervix should be allowed to regain its pink color (usually over about 5 minutes). Repeat the freeze sequence as described. The second freeze is usually faster. After the freeze is completed, disengage the probe and remove the speculum. The patient may get up, get dressed, and leave as soon as she is ready.
(4) A rim of ice should form and grow to a width of at least 5 mm in all quadrants.
PITFALL: Fainting and light-headedness are not uncommon. Have the patient rest supine for at least several minutes and then sit up slowly.
INSTRUMENT AND MATERIALS ORDERING
The device consists of a gas tank containing nonexplosive, nontoxic gases (usually nitrous oxide but may be carbon dioxide). A 20-lb gas cylinder is preferable to the 6-lb E-type tank, because the former has a more efficient pressure release curve. Liquid nitrogen has been used in the past but is difficult to control and is not recommended. Tanks are usually obtained from local suppliers.
Cryotherapy units may be obtained from Circon/Cryomedics, Racine WI (phone: 888-524-7266 or 414-639-7205; http://www.acmicorp.com/acmi/user); CooperSurgical, Shelton, CT (phone: 800-645-3760 or 203-929-6321;http://www.coopersurgical.com); Gyne-tech Instruments, Burbank, CA (phone: 800-496-3832 or 818-842-0933); Leisegang Medical, Inc., Boca Raton, FL (phone: 800-448-4450 or 561-994-0202; http://www.leisegang.com) Olympus America, Inc., Melville, NY (phone: 800-548-555 or 631-844-5000; http://www.olympusamerica.com); Wallach Surgical Devices, Inc., Orange, CT (phone: 203-799-2000 or 800-243-2463; http://www.wallachsurgical.com); and Welch Allen, Skaneateles Falls, NY (phone: 800-535-6663 or 315-685-4100;http://www.welchallyn.com). Appendix B lists standard gynecologic instruments.
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