The Effects of Water Temperature on the Cold Pressor Test

Since the 1940s, the cold pressor test (CPT) has been used experimentally as a pain induction method due to its reliability, cost effectiveness and minimal production of side effects. In the CPT, a patient is asked to place his or her hand and forearm in an ice bath until the pain is too great to remain in the water. Researchers have employed the CPT to test a wide range of pain management techniques, including medications, cognitive- based therapies, or acupuncture, as well as to explore pain perception. The CPT has been performed on a variety of participants, including adolescents, drug abusers, and those suffering from chronic back pain.

In their classic 1989 paper, Walsh and colleagues developed the normative model of the CPT demonstrating that variations in response are dependent upon age, sex and ethnicity. In 2004, however, Mitchell et al. discovered that the water temperature of the CPT also plays a crucial role in the pain tolerance time of the subjects, noting that a temperature variation of 4°C produced significantly different results for the same subject. While the Mitchell investigations improved upon the standard for the proper CPT technique, as seen implemented in the works of Rash and Campbell, their discoveries were based on healthy individuals.

Researchers have explored the CPT responses of patients with an altered pain perception, such as patients with Opioid-Induced Hyperalgesia (OIH), in comparison to healthy controls, demonstrating greater sensitivity in OIH patients. What has not been studied is the effect of temperature on CPT response in OIH patients. Further, the CPT has been shown to have a relatively lengthy recovery time averaging around 10 minutes; however, the recovery time for hypersensitive patients, such as OIH patients, has yet to be studied.

As an extension of the work of Mitchell and colleagues, the proposed research will assess the effects of temperature difference and recovery time of the CPT on patients with OIH in comparison to healthy normal control patients. This work is a sub-study of a larger study, Opioid-Induced Hyperalgesia In Prescription Opioid Abusers: Effects of Pregabalin (PRO00000669), conducted by principal investigator Dr. Peggy Compton. The goal of the parent study is to evaluate the ability of pregabalin to diminish chronic low back or arthritic pain and OIH in a sample of prescription opioid abusers (POAs) opioid therapy. This current study is not assigning specific interventions to study subjects. Healthy control and OIH participants will complete all study measures in a single two-hour study session.

Inclusion criteria

• Between 21 and 65 years old
• On suboxone or methadone for at least ten days
• Currently experiencing chronic low back or arthritis pain

Exclusion criteria

• Be on any opioid analgesic
• Have a neurological or psychiatric illness (i.e., schizophrenia, Raynaud's disease, urticaria, stroke) that would affect pain responses
• Have an abnormal screening EKG, history of heart disease, stroke, liver or kidney disease or acute hepatitis, or currently have a pacemaker or uncontrolled high blood pressure.