Hypothermia cap

A hypothermia cap (also referred to as "cold cap" or "cooling cap") is a therapeutic device used to cool the human scalp. Its most prominent medical applications are in preventing or reducing alopecia in chemotherapy, and for preventing cerebral palsy in babies born with neonatal encephalopathy caused by hypoxic-ischemic encephalopathy (HIE). It can also be used to provide neuroprotection after cardiac arrest, to inhibit stroke paralysis, and as cryotherapy for migraine headaches.

Worn tight on the head, hypothermia caps are typically made of a synthetic such as neoprene, silicone or polyurethane, and filled with a coolant agent such as ice or gel which is either frozen to a very cold temperature (-25 °C to -30 °C, or -13 °F to -22 °F) before application or continuously cooled by an auxiliary control unit.

Medical Uses

Prevention of chemotherapy-induced alopecia

One side effect of chemotherapy drugs such as Epirubicin, Docetaxel and Adriamycin, particularly in the treatment of breast cancer, is alopecia. As a method of preventing or reducing alopecia in chemotherapy patients, a hypothermia cap may be worn to induce local vasoconstriction around hair follicles during peak plasma concentrations of chemotherapeutic agents. The decreased blood flow around the hair follicle lessens or prevents the impact of alopecia-inducing chemotherapy toxins, thus preserving the follicles, and ultimately, the patient's hair.

The first U.S. patent, filed in 1979 and granted in 1984,^[1][2] was for Mark B. Barron's (née Mark Bowen) "Chemo Cap," which consisted of resizable gel-filled nylon pouches that were frozen and worn for 15 to 20 minutes prior to treatment.^[3] However, studies throughout the 1980s and early 1990s were not sufficiently encouraging,^[4] and the patent expired in 1998. An analysis of 53 studies from 1995 through 2003, however, showed an average success rate of 73%,^[5] and correspondingly, interest in scalp cooling in the prevention of alopecia in chemotherapy patients was renewed. Subsequent studies have shown success rates of 80 to 90 percent with certain chemotherapy regimens;^[6] one 2010 study by researchers in Finland reported a reduction of alopecia, in differing amounts, in 100% of the 64 participants who used the caps, with 20 percent opting to wear a wig following treatment.^[7]

Presently, the DigniCap Scalp Cooling System and the Penguin Cold Caps are being used throughout Europe, and both are undergoing testing in the United States for use in those with breast cancer while awaiting FDA approval.^[8][9][10] The DigniCap was first made available in Sweden in the mid-1990s,^[11] and of the over 4,000 patients who have used it, over 85% reported keeping their hair.^[12] In the DigniCap, coolant is cooled with the aid of a compressor and then pumped out into cooling caps. Circulation is controlled by temperature sensors in the cap and regulated by valves. If the temperature deviates from the set values or if other errors are detected, an alarm system is activated.^[13] The Penguin Cold Cap, invented by Frank Fronda of Medical Specialties of California and introduced in 1994,^[14] involves continuous application of caps filled with crylon gel cooled to -30 °C (-22 °F) to the scalp every 20 to 30 minutes before, during and after intravenous chemotherapy.^[15][16] Chemo Cold Caps, LLC provides patients with a turn key scalp cooling solution that makes the process of trying to reduce chemotherapy induced alopecia much simpler.

One reason for the slow adoption of hypothermia caps in the U.S. is concern that the caps could produce a corresponding increase in metastases of the scalp. However, a study published in 2009 showed an incidence of scalp metastasis of 1.1% (six cases out of 553 patients) among women who used scalp cooling and 1.2% (one case out of 87 patients) among women who did not use scalp cooling.^[17] Scalp cooling has been shown effective in reducing alopecia caused by anthracyclines and taxanes, but not when the two are used in combination.^[18]

Prevention of cerebral palsy in babies born with neonatal encephalopathy

Hypoxic ischemic encephalopathy (HIE) is a condition that occurs when the brain is deprived of an adequate oxygen supply, and is most commonly observed in newborn babies due to birth asphyxia. It is the leading cause of cerebral palsy, an irreversible neonatal brain injury that can result in long-term cognitive, motor, and visual impairments. About 10,000 babies are born each year with cerebral palsy.

In such cases, by slowing down cell metabolism and body functions, a hypothermic cap can be used to lessen a baby's need for oxygen. Research throughout the late 1990s and 2000s demonstrated that for every degree a baby's body temperature is lowered, its body functions and demand for energy slow down by 10 to 15 percent. Therefore, slowing metabolic demands through hypothermia therapy can rectify a mismatch between oxygen supply and cell need, lowering the risk for cerebral palsy.^[19]

Among babies who meet the criteria for hypothermia therapy—full-term with no known pre-existing conditions, having neonatal distress, and an abnormal neurological exam^[20]—cooling must begin within six hours of birth and body temperature must be maintained at 33–34 °C (91–93 °F) for 72 hours before being gradually warmed again. An alternative to hypothermia caps involves pumping cold water through a specially adapted blanket, cooling the whole body.^[21]

Induced pediatric hypothermia was approved in the U.S. by the FDA in March 2007. The most prominent such hypothermia cap is the Olympic Cool-Cap System, which utilizes a cooling unit, a control unit and temperature probes to maintain a steady flow of cool water through a cap covering the head.^[22]

Neuroprotection after cardiac arrest

A 2008 trial demonstrated that the pre-hospital induction of therapeutic hypothermia after cardiac arrest as soon as possible after return of spontaneous circulation (ROSC) can achieve optimal neuroprotective benefit. The hypothermia cap was applied to 20 patients after out-of-hospital cardiac arrest, with a median of 10 min after ROSC. The median time between initiation of cooling and hospital admission was 28 minutes. No side effects related to the hypothermia cap were observed. The study concluded that "prehospital use of hypothermia caps is a safe and effective procedure to start therapeutic hypothermia after cardiac arrest. This approach is rapidly available, inexpensive, non-invasive, easy to learn and applicable in almost any situation."^[23]

Other uses

The use of hypothermia caps has also shown promise in inhibiting stroke paralysis. Studies are underway testing a combination treatment consisting of four drugs plus a hypothermia cap to try to slow the cell death that is triggered by an ischemic stroke.^[24] Ischemic strokes are caused when a clot blocks blood flow to the brain, and comprise roughly 80% of all strokes.^[25] The slowing of cell death is theorized to give the brain time to find an alternate blood supply through unblocked arteries, meaning patients may potentially avoid physical and speech impairments caused by ischemic strokes.^[26]

Numerous studies have also suggested that therapeutic hypothermia can provide safe and effective adjunctive treatment for migraine headaches. For instance, a 1989 study in Headache: The Journal of Head and Face Pain showed 64.5% of 45 patients with migraine or migraine plus chronic daily headache evaluated use of a cold wrap for 20 to 30 minutes as mildly, moderately or completely effective.^[27] In a 1984 study using a frozen gel pack, 80% of migraine patients reported the pack was effective. Numerous over-the-counter hypothermia caps today offer therapy for headaches.^[28]

See also

• Hypothermia therapy for neonatal encephalopathy
• Therapeutic hypothermia

References