CryoProbe: Cryosurgery Review

The CryoProbe™ is a portable cryosurgical device employed by some physicians and veterinarians to treat benign skin lesions using disposable Nitrous Oxide cartridges. The nitrogen is applied to tissue by the spray from accessories called applicator tips, varying in size from 1mm to 15mm.

As with many cryosurgical methods, the patient will experience minimal or minor discomfort. The CryoProbe may allow for longer treatment and deeper freeze, which could lead to effective results.

The CryoProbe is intended for destruction of unwanted tissue by applying extreme cold using liquefied Nitrous Oxide. Treatable lesions include angiofibroma, granuloma, condyloma, dermafibroma, molluscumcontagiosum, porokeratosis, seborrheic keratosis, actinic keratosis, solar lentigo, warts on the feet and warts on the hand.

The CryoProbe cryosurgery system does require upfront costs in the range of $3000 for necessary equipment, and regular maintenance costs over time. Cartridges have limited use and the Nitrous Oxide will evaporate completely within a few weeks after they are first punctured.

The CryoProbe is cleared by the FDA as a Class ll device for physician use only.

Review of Histofreezer Cryosurgical System

Histofreezer is a portable cryosurgical system consisting of a proprietary mixture of gases in a handheld canister. The treatment times are 15-40 seconds and results are comparable to liquid nitrogen, with a freezing temperature of -55°C (-67°F).

Histofreezer is indicated for nine benign skin lesions such as common warts (verruca vulgaris), plantar warts (verruca plantaris), flat warts, actinic keratoses, seborrheic keratoses, skin tags (acrochordon), age spots (lentigo), condyloma acuminata and molluscum contagiosum.

This product is similar in some ways to Verruca Freeze, although Histofreezer treats fewer lesions and does not get as cold. Furthermore, Histofreezer has a shelf life of 2-3 years, compared to six years for Verruca Freeze.

Cryosurgical Applications and Technique

Tissue injury from freezing may be inflammatory or destructive in nature, depending on the severity of cooling. Usually, cryosurgical techniques are intended to produce necrosis. If the freeze time is too short or the thaw time is aborted from touching the treated lesions, only inflammation usually occurs.

Mechanisms of injury are the direct effects of freezing on the cells (such as crystallization of water, concentration or solute in the cells and irreversible changes in cell membranes) and vascular stasis which develops in the tissue after thawing.

The cornerstone of injury is ice crystal formation. Extracellular ice formation, which occurs with slow freezing, is associated with the loss of water from the cells and toxic concentration of the solute in the cells, called solution effects. Intracellular ice formation, which occurs with rapid freezing, is considered more lethal. Both types of ice formation occurs in cryosurgery. Fast cooling occurs in the center, slow cooling occurs at the border of the frozen tissue.

Vascular stasis (microcirculatory failure) is a major factor in tissue death. The loss of blood supply deprives all cells in frozen tissues of any possibility of survival.

Melanocytes, osteocytes are sensitive to cryogenic injury and cellular tissue sloughs quickly. Bone, though devitalized, resists sloughing. Fibrous stroma, large arteries, nerves, and cartilage resist structural change. The matrix serves as a framework for repair.

Factors determining the extent of cryogenic injury:

  1. Choice of the cryogen
  2. Manner of use and technique
  3. Freeze-thaw duration
  4. Efficiency of heat transfer
  5. Induced tissue ischemia
  6. Blood supply to the tissue
  7. Extent of vascular stasis after freezing

Variable factors in freeze-thaw cycles:

  1. Cooling rate
  2. Temperature produced in the tissue
  3. Duration of freezing
  4. Thawing rate
  5. Repetition of freeze-thaw cycles
  6. Interval between freeze-thaw cycles

Maximize tissue destruction:

  1. Freeze as fast as possible
  2. Attain lethal temperature (minimum -50 degrees Celsius)
  3. Maintain freezing for appropriate time
  4. Thaw slowly and completely
  5. Provide a short thawed interval (1-2 minutes)
  6. Repeat the freeze-thaw cycle (2-3 cycles for large lesions)
  7. Rapid freezing, slow thawing, and repetition of freeze-thaw process are standard features of technique
  8. Reduce the blood supply to the tissue by fluid (anesthetic) injection beneath the lesion prior to freezing.

A tissue temperature for at least -50 degrees Celsius is associated with extensive necrosis and is sufficient for permanent destruction of benign lesions.

What is Cryosurgery?

Cryosurgery (cryotherapy) is the application of extreme cold to destroy abnormal or diseased tissue.[1] The term comes from the Greek words cryo (κρύο) (“icy cold”) and surgery (cheirourgiki – χειρουργική) meaning “hand work” or “handiwork”. Cryosurgery has been historically used to treat a number of diseases and disorders, especially a variety of benign and malignant skin conditions.[2]

Some commonly used cryotherapy systems are Brymill Cry-Ac, CryoPen, CryoProbe, Histofreezer, Miltex CryoSolutions, Premier CryOmega, Premier NitroSpray, and Verruca-Freeze.