The cold pressor test involves dipping a patient’s hand in cold water to stimulate the sympathetic nervous system. Patients with certain disorders may respond abnomrally 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 workup. This test is not very invasive and can be performed very quickly in a doctor’s office without any special preparation ahead of time.
Typically, a cold pressor test involves a container filled with ice water. The patient’s hand is dipped in the container for at least a minute. Sometimes a foot may be used instead, or a cold cloth or pack can be placed on the patient’s forehead. In all cases, the cold pressor test stresses the body, causing the sympathetic nervous system to react. This should cause a rise in blood pressure, because the veins will constrict in response to the cold.
Blood pressure rises may be accompanied by changes in heart rate. These are associated with vagus nerve stimulation. During the cold pressor test, a care provider can monitor the patient’s blood pressure and heart rate for the 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 sense pain, or a neurological disorder might mix the signals sent by the sympathetic nervous system, which could be a problem with a real-world source of physical stress.
Patients taking the test can report the onset of pain, which provides important data about sensation and tolerance. It is important to use water chilled to a standard temperature for the cold pressor test so the patient’s results can be accurately compared to those of others. When the pain becomes unbearable, forcing the patient to move the hand, this can add another value to the pain scale. The length of time required for the patient to notice the pain and decide it is too unpleasant can indicate how well the patient tolerates unpleasant stimuli.
Low pain tolerances may be a sign of an underlying neurological problem. The cold pressor test may indicate that something is wrong, and further testing could be necessary 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.