The overall goal of this testing protocol is to use quantitative sensory testing to obtain measures of pain processing in surgical patients. Many patients develop persistent pain after surgical procedures. That may be related to changes in pain processing.
This protocol may help answer key questions in the field of pain medicine. Such as which patients are prone to develop persistent pain after surgery. Demonstrating this procedure will be done by Hans Timmerman.
A researcher from our department anesthesiology, pain and palliative medicine. Before beginning the electrical pain threshold analysis turn on the quantitative sensory testing or QST stimulator and use the connection leads to attach the self-adhesive electrodes to the stimulator. Connect a visual analog scale slider consisting of a box with a mobile lever on a horizontal bar that represents the visual analog scale to the stimulator and hand the slider to the patient.
After explaining to the patient how to use the slider explain the procedure for the electrical detection threshold. Mark the testing sites in the C5 dermatome, the C6 dermatome, the T4 dermatome, the L1 dermatome and the L3 dermatome. Mark the L3 testing sites 15 centimeters above the patella.
To conduct a test run, instruct the patient to press the button to begin the stimulus. And to immediately release the button as soon as the stimulus is felt. Ask the patient to use the visual analog scale slider to indicate how the stimulus was experienced and note the result in the chart.
Next, explain the procedure for the electrical pain threshold test and perform a single test run as just demonstrated for the electrical detection threshold test. Having the patient immediately release the button as soon as the stimulation becomes painful. Record the result on the measurement chart.
Then, ask the patient to use the visual analog scale slider to rate the pain associated with the stimulus and note the result on the chart. After explaining the procedure for electrical detection threshold again, measure the electrical detection threshold three times at each study site, allowing at least 15 seconds between each measurement to avoid wind-up effects. Have the patient rate the associated pain on the visual analog scale after the last electrical detection threshold measurement at each site and note the test electrical values and visual analog scale scores on the measurement chart.
Next explain the procedure for determining the electrical pain threshold again and measure the electrical pain threshold three times at each study site as just demonstrated for the electrical detection threshold tests. Then, have the patient rate the associated pain on the visual analog scale after the last electrical pain threshold pain measurement at each site and note the test electrical values and visual analog scale scores on the measurement chart. To deliver the pressure pain threshold test, first explain the procedure to the patient.
Then, to conduct a test run, place a pressure algometer with a one square centimeter probe at a 90 degree angel on the patient's muscle and manually adjust the applied pressure and the pressure on the display at a ramping rate of approximately five newtons per second. To prevent skidding of the pressure measurement device, place the probe perpendicular to the skin and support the device with both hands while slowly increasing the pressure while standing firmly in place. Instruct the patient to say now"when the pressure feeling becomes throbbing, burning or painful and record the value on the measurement chart.
Explain the pressure pain threshold test to the patient again and apply pressure two times at each study site allowing at least 15 seconds between each measurement to avoid wind-up effects. Then, ask the patient to rate the associated pain on the visual analog scale after the last pressure pain threshold measurement at each site and note the test pressure values and visual analog scale scores on the measurement chart. To conduct a conditioned pain modulation test, give the patient the same instructions as for the pressure pain threshold test, and perform a pressure pain threshold test stimulus at the conditioned pain modulation test site.
Have the patient rate the associated pain on the visual analog scale slider, then note the value at which the pressure became painful and the associated pain score on the measurement chart. Next, use the temperature probe to measure the water temperature in a cold presser tank and explain the ice water procedure to the patient. Have the patient submerge a hand in the ice water up to the wrist and with the fingers spread for three minutes or until the patient can no longer tolerate the cold.
Ask the patient to rate the pain on a scale of zero to 10 for every 10 seconds that the hand is in the ice water and note the results on the measurement chart. As soon as the hand is removed from the ice water, measure the pressure pain threshold on the conditioned pain modulation test site and have the patient rate the associated pain on the visual analog scale. Then, note the pressure pain threshold and visual analog scale scores on the chart.
Women who develop persistent post surgical pain 12 months after breast cancer surgery defined as a visual analog scale of greater than 30 millimeters, exhibit lower pressure pain thresholds both early and late after surgery. Indeed, for every 10%lower threshold five days after surgery, the breast cancer surgery patients were 50%more likely to exhibit chronic pain at 12 months after the surgical procedure. Once mastered, this technique can be completed in about 20 minutes, when it's performed properly.
As more perioperative QST data become available, maybe we can develop treatments that minimize the risk of post-operative persistent pain.
