The cold pressor test involves immersing the patient's hand in cold water to stimulate the sympathetic nervous system. Patients with certain disorders may respond abnormally to the test, illustrating the presence of a neurological problem. It also causes pain, which can be used to assess a patient's pain tolerance as part of a study. This test is not very invasive and can be done very quickly in a doctor's office without any special preparation ahead of time.
Typically, a cold pressure test involves a container filled with ice water. The patient's hand is immersed in the container for at least one minute. Sometimes a foot can be used, or a cold cloth or pack can be placed on the forehead of the patient. In all cases, the cold pressure test stresses the body, causing the sympathetic nervous system to react. This should cause an increase in blood pressure, because the veins will contract in response to the cold.
The increase in blood pressure may be accompanied by changes in heart rate. These are associated with stimulation of the vagus nerve. During the cold pressure test, a healthcare provider can monitor the patient's blood pressure and heart rate for expected changes. If the patient does not respond as expected, this may be a sign of a disorder. For example, the patient's nerves might not feel pain, or a neurological disorder might mix the signals sent by the sympathetic nervous system, which could be a problem with a source of physical stress in the real world.
Patients taking the test can report the onset of pain, which provides important data on sensation and tolerance. It is important to use chilled water to a standard temperature for the cold pressure test so that the patient's results can be accurately compared with those of others. When pain becomes excruciating, forcing the patient to move their hand, this can add another value to the pain scale. The time required for the patient to notice the pain and decide that it is too unpleasant can indicate how well the unpleasant stimuli are tolerated.
Low pain tolerances can be a sign of an underlying neurological problem. The cold pressure test can indicate something is wrong, and more tests may be needed for a diagnosis. This could include other neurological function tests involving different sources of stimulation to see how the patient reacts. Treatment options depend on the nature of the condition; some patients may benefit from medication, physical therapy, or surgery to treat nerve disorders.