We thank the patients who participated in the study presented in the &#39;Representative results&#39; section.

This protocol has been approved in the context of a previous randomized controlled trial8 by the human research ethics committee region Arnhem-Nijmegen, the Netherlands (nr. 2004/239).
1. Preparation for Testing
<ol>
	<li>Informed consent:
	<ol>
		<li>Review the informed consent form together with the patient.</li>
		<li>Answer any questions that patient may have regarding the study.</li>
		<li>Obtain written informed consent by having the patient sign the informed consent form and signing it yourself.</li>
	</ol>
	</li>
	<li>Testing environment:
	<ol>
		<li>Perform all the measurements in the protocol in a stimulus poor and temperature stable environment (~21 &#176;C, no music, no uncovered windows, phones switched off). 
		NOTE: The clothing of the experimenter needs to be as neutral as possible, i.e. wear a lab coat, be &#39;naked below the elbows,&#39;&#160;wear no jewelry, and wear no perfume. It is well known that experimenter related factors may have influence on the outcome of the measurements. Some of these factors are not completely standardizable (e.g. sex), but one should keep this in mind when preparing the performance of the measurements.</li>
		<li>During measurements, ensure that the patient and the researcher are the only people in the room, ask others to leave.</li>
		<li>Attach a &#39;do not disturb&#39; sign to the door to avoid being disturbed during the measurements.</li>
		<li>Perform all testing with the patient in the supine position on the bed, except for the CPM test, which is performed with the patient in sitting position.</li>
	</ol>
	</li>
	<li>Sites of testing:
	<ol>
		<li>Mark the following sites for threshold testing using a surgical skin marker: 
		area under the greater tubercle on bilateral shoulders (C5 dermatome, pressure and electric thresholds), the bilateral thenar (C6, dermatome, pressure), on bilateral iliac crests (L1 dermatome, pressure and electric), bilateral in the mid axillary line at nipple height or 7 cm from the surgical incision in case of breast cancer surgery (T4 dermatome, pressure and electric thresholds).</li>
		<li>Mark the CPM testing site using a surgical skin marker: 15 cm above the patella on the non-dominant body site (L3 dermatome, pressure).</li>
		<li>Mark a test run site using a surgical skin marker, for example, 15 cm above the patella on the dominant body site.</li>
	</ol>
	</li>
	<li>Electrical stimulation configuration:
	<ol>
		<li>Apply two self-adhesive skin electrodes on each side of the marked spot on each electrical stimulation test site. Place the electrodes with their outer diameter such that they are just touching each other at the marked spot.</li>
		<li>Set the QST stimulator to deliver tetanic stimulation (100 Hz, 0.2 ms square waves) &#8211; Figure 1. Set the ramping rate to 1 mA/s. Set the initial current to 0 mA, the maximum current is automatically set to 50 mA for safety purposes.</li>
	</ol>
	</li>
</ol>
2. Electrical Pain Thresholds
<ol>
	<li>Delivery of electricity:
	<ol>
		<li>Use the QST stimulator. Connect the self-adhesive electrodes to the stimulator using the connection leads.</li>
	</ol>
	</li>
	<li>Measurement of visual analogue scale (VAS):
	<ol>
		<li>Use the VAS slider connected to the QST stimulator to obtain VAS scores. The VAS slider consists of a box with a mobile lever on a horizontal bar that represents the VAS. Hand the slider to the patient.</li>
		<li>Explain to the patient how to use the slider: &#34;The control unit has a slider. This slider can be moved to indicate how you experience the stimulus on a scale of no pain to the worst imaginable pain.&#34;</li>
	</ol>
	</li>
	<li>Test run:
	<ol>
		<li>Explain the procedure for the electrical detection threshold (EDT) to the patient: &#34;We will conduct a test run to get you familiarized with the measurement. The stimulation will start when you press the button, will gradually increase, and will stop immediately upon letting go of the button. Please press the button when I tell you to do so and let go when you feel anything.&#34; 
		NOTE: All instructions are read from a manual to aid in standardization.</li>
		<li>Perform a single test run on the test run site to demonstrate the procedure. Record the result on the measurement sheet &#8212; Figure 2. Make sure the patient cannot read the values of the measurements during the execution of the tests.</li>
		<li>Ask the patient to indicate how he/she experienced the stimulus using the VAS slider and note the result.</li>
		<li>Explain the procedure for the electrical pain threshold (EPT) to the patient: &#34;We will conduct a test run to get you familiarized with the measurement. This test is aimed at determining your pain perception in response to electrical stimulation. The stimulation will start when you press the button, will gradually increase, and will stop immediately upon letting go of the button. Please press the button when I tell you to do so and let go when the stimulation becomes painful.&#34;</li>
		<li>Perform a single test run on the testing site to demonstrate the procedure. Record the result on the measurement sheet.</li>
		<li>Ask the patient to indicate how he/she experienced the stimulus using the VAS slider and note the result.</li>
	</ol>
	</li>
	<li>Measurement:
	<ol>
		<li>Explain the procedure for EDT again to the patient, using wording from 2.3.1.</li>
		<li>Measure the EDT at the different study sites (first C5, then T4, then L1). Perform EDT measurement three times at each measurement site, allow at least 15 seconds in between measurements to avoid windup effects.</li>
		<li>Ask the patient to rate the associated pain on VAS after the last EDT measurement at each site. Note electrical values and VAS scores on the measurement sheet. Make sure the patient cannot read the values of the measurements during the execution of the tests.</li>
		<li>Explain the procedure to determine the EPT again using wording from 2.3.4.</li>
		<li>Measure the EPT at the different study sites (first C5, then T4, then L1). Perform EPT measurement three times at each measurement site, allow at least 15 seconds in between measurements to avoid windup effects.</li>
		<li>Ask the patient to rate the associated pain on VAS after the last EPT measurement at each site.</li>
		<li>Note test electrical values and VAS scores on the measurement sheet. Make sure the patient cannot read the values of the measurements during the execution of the tests.</li>
	</ol>
	</li>
</ol>
3. Pressure Pain Thresholds
<ol>
	<li>Delivery of pressure:
	<ol>
		<li>Deliver pressure with the pressure algometer with a 1.0 cm2 probe under a 90&#176; angle. Use a ramping rate of ~5 N/s by manually adjusting the applied pressure and the pressure on the display. Start at 0 N and apply up to a maximum of 200 N for safety purposes. 
		NOTE: Be careful not to let the device skid on the skin. To prevent skidding of the algometer it is important to place the probe perpendicular to the skin and to support the algometer with both hands while slowly increasing the pressure. The researcher should stand firmly to provide a controlled increase in pressure.</li>
	</ol>
	</li>
	<li>Test run:
	<ol>
		<li>Explain the procedure to the patient: &#34;We will conduct a test run to get you familiarized with the measurement. This measurement is aimed at determining your perception of pressure pain in muscle. I will put a pressure measurement device on your muscle and will gradually increase the pressure. Please notify me when the pressure feeling becomes throbbing, burning, or painful by saying &#39;now.&#39;&#34;</li>
		<li>Perform a single test run on the test site. Make sure the patient cannot read the values of the measurements during the execution of the tests. Record the result on the measurement sheet.</li>
	</ol>
	</li>
	<li>Measurement:
	<ol>
		<li>Repeat the instructions for patient using wording from 3.2.1.</li>
		<li>Apply pressure to the different study sites (first C5, then C6, then T4, then L1). Perform pressure pain threshold (PPT) measurement two times at each measurement site, allow at least 15 seconds in between measurements to avoid windup effects.</li>
		<li>Ask the patient to rate the associated pain on VAS after the last PPT measurement at each site.</li>
		<li>Note test pressure values and VAS scores on the measurement sheet.</li>
	</ol>
	</li>
</ol>
4. Conditioned Pain Modulation Paradigm
<ol>
	<li>Preconditioning test stimulus
	<ol>
		<li>Repeat 3.1.1. but use PPT as test stimulus. Repeat the instructions for patient using wording from 3.2.1.</li>
		<li>Measure pre-conditioning PPT at the CPM testing site (m. rectus femoris (L3) on the non-dominant side, 15 cm above the patella). Ask the patient to rate the associated pain on the VAS slider. Note the value at which the pressure become painful and the associated pain score.</li>
		<li>Explain the ice water procedure to the patient: &#34;This is a test to gain information on the way your body processes different pain signals at the same time. I will ask you to submerse your hand into the ice water in the bucket. Place your hand in the water until the wrist and with the fingers spread. Please hold your hand in the ice water until you can no longer tolerate it.&#34;</li>
		<li>Tell the patient to remove their hand from the water after 3 minutes of immersion or sooner if the pain becomes intolerable. &#34;Every 10 seconds, I will ask you to rate the pain on a 0 to 10 scale, in which 0 represents no pain and 10 unbearable pain. After you take your hand out of the ice water we will measure the pressure pain threshold on your leg again, similar to how we did that before.&#34;</li>
	</ol>
	</li>
	<li>Conditioning stimulus:
	<ol>
		<li>Use the cold pressor task as conditioning stimulus. Measure the water temperature using a temperature probe and note the temperature (target temperature between 1 &#176;C and 4 &#176;C).</li>
		<li>Ask patient to immerse dominant hand in ice-chilled water. Ask the patient to rate the pain throughout the cold pressure task every 10 seconds on VAS and note the result. Note the completed immersion time on the measurement sheet (maximum duration is 180 seconds, on average 56 &#177; 55 s8).</li>
	</ol>
	</li>
	<li>Determine test stimulus post-conditioning:
	<ol>
		<li>Measure PPT on the CPM test site after the conditioning stimulus. Ask the patient to rate the associated pain on VAS and note PPT and VAS score on sheet.</li>
	</ol>
	</li>
</ol>
5. Calculations
<ol>
	<li>EPTs:
	<ol>
		<li>Calculate the mean value for each testing location of the EDTs and EPTs.</li>
	</ol>
	</li>
	<li>PPTs:
	<ol>
		<li>Calculate the mean value for each testing location of the PPTs.</li>
	</ol>
	</li>
	<li>CPM:
	<ol>
		<li>Determine the CPM effect by calculating the relative change (in %) in the PPT at the CPM test location before and after the conditioning stimulus10. 
		&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;CPM = ([PPTpost &#8211; PPTpre] / PPTpre) * 100 
		CPM = conditioned pain modulation; PPT = pressure pain threshold.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Macrae, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+post-surgical+pain:+10+years+on.">Chronic post-surgical pain: 10 years on.</a> Br J Anaesth. 101 (1), 77-86 (2008).</li><li>IASP Taxonomy Working Group. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Classification of Chronic Pain. , (2011).</li><li>Kehlet, H., Jensen, T. S., Woolf, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Persistent+postsurgical+pain:+risk+factors+and+prevention.">Persistent postsurgical pain: risk factors and prevention.</a> Lancet. 367 (9522), 1618-1625 (2006).</li><li>Steegers, M. A., Wolters, B., Evers, A. W., Strobbe, L., Wilder-Smith, O. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+axillary+lymph+node+dissection+on+prevalence+and+intensity+of+chronic+and+phantom+pain+after+breast+cancer+surgery.">Effect of axillary lymph node dissection on prevalence and intensity of chronic and phantom pain after breast cancer surgery.</a> J Pain. 9 (9), 813-822 (2008).</li><li>Yarnitsky, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prediction+of+chronic+post-operative+pain:+pre-operative+DNIC+testing+identifies+patients+at+risk.">Prediction of chronic post-operative pain: pre-operative DNIC testing identifies patients at risk.</a> Pain. 138 (1), 22-28 (2008).</li><li>Hsu, E., Cohen, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postamputation+pain:+epidemiology,+mechanisms,+and+treatment.">Postamputation pain: epidemiology, mechanisms, and treatment.</a> J Pain Res. 6, 121-136 (2013).</li><li>Franneby, U., Sandblom, G., Nordin, P., Nyren, O., Gunnarsson, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risk+factors+for+long-term+pain+after+hernia+surgery.">Risk factors for long-term pain after hernia surgery.</a> Ann Surg. 244 (2), 212-219 (2006).</li><li>van Helmond, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperalgesia+and+Persistent+Pain+after+Breast+Cancer+Surgery:+A+Prospective+Randomized+Controlled+Trial+with+Perioperative+COX-2+Inhibition.">Hyperalgesia and Persistent Pain after Breast Cancer Surgery: A Prospective Randomized Controlled Trial with Perioperative COX-2 Inhibition.</a> PLoS One. 11 (12), e0166601 (2016).</li><li>Le Bars, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+whole+body+receptive+field+of+dorsal+horn+multireceptive+neurones.">The whole body receptive field of dorsal horn multireceptive neurones.</a> Brain Res Brain Res Rev. 40 (1-3), 29-44 (2002).</li><li>Yarnitsky, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recommendations+on+practice+of+conditioned+pain+modulation+(CPM)+testing.">Recommendations on practice of conditioned pain modulation (CPM) testing.</a> Eur J Pain. 19 (6), 805-806 (2015).</li><li>Rolke, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+sensory+testing:+a+comprehensive+protocol+for+clinical+trials.">Quantitative sensory testing: a comprehensive protocol for clinical trials.</a> Eur J Pain. 10 (1), 77-88 (2006).</li><li>Wilder-Smith, O. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> A Paradigm-Shift in Pain Medicine: Implementing a Systematic Approach to Altered Pain Processing in Everyday Clinical Practice. Based on Quantitative Sensory Testing. , (2013).</li><li>Nasri-Heir, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+pain+modulation+in+patients+with+persistent+postendodontic+pain.">Altered pain modulation in patients with persistent postendodontic pain.</a> Pain. 156 (10), 2032-2041 (2015).</li><li>Treede, R. D., Meyer, R. A., Raja, S. N., Campbell, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peripheral+and+central+mechanisms+of+cutaneous+hyperalgesia.">Peripheral and central mechanisms of cutaneous hyperalgesia.</a> Prog Neurobiol. 38 (4), 397-421 (1992).</li></ol>

The authors have no conflicts of interests or any financial interests to disclose.

Our method of quantifying pressure pain thresholds, electrical pain thresholds, and CPM can be successfully applied in a clinical context given its short duration (~20 minutes). We have previously shown that pressure pain values obtained early after surgery may be of value in predicting persistent pain at long term follow-up in the context of breast cancer surgery8. While electrical pain thresholds CPM were not predictive of persistent pain in our study, others have shown that these measures may be of value with regards to other procedures5,13. A limitation of using electrical pain thresholds is that it may represent an unnatural stimulus. However, the fact that it bypasses local modulation and that it offers very precise control over intensity and timing, improving repeatability, led us to include it in the current protocol14. Alternative stimulus modalities, such as heat, could potentially be used to replace the electrical stimulus in the present protocol.
We hope that detailing a circumscribed, yet valuable, quantitative sensory testing paradigm will lead to wider application of these measures in the context of the study of persistent pain after breast cancer. Once more perioperative quantitative sensory testing data become available it may be possible to identify subpopulations of patients that are at high risk of developing persistent postsurgical pain, and to tailor periprocedural treatments to minimize the risk of eventually developing persistent pain.

Chronic pain following surgery, persistent postsurgical pain, is an important condition contributing to significant symptom burden and lower quality of life1. Persistent post-surgical pain remains poorly understood, but is broadly recognized as pain lasting more than 3 months after surgery2. The condition is common, with estimates of its prevalence ranging from 10% to 50% of all postsurgical patients3. High-risk procedures include breast surgery4, thoracotomy5, limb amputation6, and hernia repair7. Persistent postsurgical pain is relatively refractory to treatment and thus has generated interest in potential preventive strategies and treatments. A better understanding of predicting and characterizing persistent postoperative pain would help identify the subset of patients who are likely to require additional treatment to optimize their peri-operative pain management.
Recently it was shown that abnormal changes in pain thresholds in response to surgery may be of predictive value for long-term persistent pain development in the context of surgery for breast cancer8. Others have stressed the importance of the conditioned pain modulation (CPM) effect in predicting persistent postoperative pain, for example with regards to persistent pain after thoracotomy5. CPM is the behavioral correlate of diffuse noxious inhibitory control, a physiological phenomenon where input from peripheral c-fibers results in diffuse inhibition from the brainstem of all incoming stimuli mediated by c-fiber from heterotopic fields9. The CPM effect is measured by comparing thresholds to a noxious stimulus, which is measured before and after the application of a second different stimulus, which is referred to as the conditioning stimulus10.
Current standardized quantitative sensory testing (QST) protocols, such as the German Research Network on Neuropathic Pain protocol11 are quite extensive and may not be suitable to perform in surgical patients. The aim of the current publication is to detail a short and standardized protocol to obtain both pain thresholds and a CPM effect measurement in breast cancer surgery patients. This protocol is derived from a collaborative protocol between our university and the University of Aalborg, Denmark12.

<table><tbody><tr><td>Bed</td><td>N/A</td><td>N/A</td><td>Any type of hospital bed or medical exam table</td></tr><tr><td>Desk</td><td>N/A</td><td>N/A</td><td>Any type of commercially available desk</td></tr><tr><td>Office chair</td><td>N/A</td><td>N/A</td><td>Any type of commercially available office chair</td></tr><tr><td>Force FPX 50 Pressure algometer</td><td>Wagner Instruments, Greenwich, CT, USA</td><td>N/A</td><td>Pressure algometer with a 1.0 cm2 circular tip to deliver pressure to perform pressure pain threshold measurements</td></tr><tr><td>Desktop computer</td><td>N/A</td><td>N/A</td><td>Any type of commercially available Windows computer to run QST-IV Stimulus Manager software on to control the QST-IV stimulator</td></tr><tr><td>QST-IV Stimulus Manager</td><td>Embedded Control BV, Ruurlo, the Netherlands</td><td>N/A</td><td>Software to control the settings of QST-IV electrical stimulator</td></tr><tr><td>QST-IV Electrical Stimulator</td><td>Embedded Control BV, Ruurlo, the Netherlands</td><td>N/A</td><td>Electrical quantitative sensory testing device with a patient operated switch. Device used to deliver electrical current to perform the electrical threshold measurements</td></tr><tr><td>VAS Slider</td><td>Embedded Control BV, Ruurlo, the Netherlands</td><td>N/A</td><td>The VAS slider consists of a box with a mobile lever on a horizontal bar that represents the VAS and is connected to the QST-IV.</td></tr><tr><td>Kendall H34SG 50 x 45 mm</td><td>Covidien, Mansfield, USA</td><td>N/A</td><td>Self-adhesive skin electrodes to apply to the measurement points on the skin to deliver electrical stimualtion</td></tr><tr><td>Crushed Ice</td><td>N/A</td><td>N/A</td><td>Ice generated by ice machine to cool water sufficiently for the cold pressor test</td></tr><tr><td>Bucket</td><td>N/A</td><td>N/A</td><td>Any type of commercially available 10 L bucket</td></tr><tr><td>Surgical skin marker</td><td>Covidien, Mansfield, USA</td><td>N/A</td><td>Any type of commercially available surgical skin marker</td></tr><tr><td>Stopwatch</td><td>N/A</td><td>N/A</td><td>Any type of commercially available stopwatch</td></tr><tr><td>Measurement form</td><td>N/A</td><td>N/A</td><td>Score form provided in the manuscript</td></tr><tr><td>Pencil</td><td>N/A</td><td>N/A</td><td>Any type of commercially available pencil</td></tr><tr><td>Thermometer</td><td>N/A</td><td>N/A</td><td>Thermometer to measure water temperature of ice water</td></tr><tr><td>Ruler</td><td>N/A</td><td>N/A</td><td>Any type of commercially available ruler</td></tr></tbody></table>

a quantitative sensory testing paradigm to obtain measures of pain processing in patients undergoing breast cancer surgery

Chronic pain following surgery, persistent postsurgical pain, is an important highly prevalent condition contributing to significant symptom burden and lower quality of life. Persistent postsurgical pain is relatively refractory to treatment hence generating a high need for preventive strategies and treatments. Therefore, the identification of patients at risk of developing persistent pain is an area of active ongoing research. Recently it was demonstrated that peri-operative disruptions in central pain processing may be able to predict persistent postsurgical pain at long term follow-up in breast cancer patients. The aim of the current report is to present a short protocol to obtain pain thresholds to different stimuli at multiple sites and a measure of endogenous analgesia in breast cancer patients. We have used this method successfully in a clinical context and detail some representative results from a clinical study.

In a previously published clinical trial in women (N = 94) undergoing surgery for breast cancer, we measured electrical and pressure pain thresholds as well as CPM using the protocol described in this report8. We performed the testing paradigm pre-operatively and at various time points throughout the year following surgery. We found that women who developed persistent postsurgical pain 12 months after breast cancer surgery, defined as a VAS of &#62;30 mm, exhibit lower pressure pain thresholds both early and late after surgery. Figure 3 details the changes in pressure pain thresholds both early (Figure 3A) and late (Figure 3B) after surgery. For simplicity&#39;s sake, the pressure pain thresholds at different measurement sites are summated and expressed as change vs. baseline. Using logistic regression, we found that for every 10% lower thresholds 5 days after surgery, patients were 50% more likely to exhibit chronic pain at 12 months after surgery (confidence interval 10&#8211;100% more likely, p = 0.01).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56918/56918fig1v2.jpg" /> 
Figure 1: Screenshot of the software interface and the appropriate settings to be used for electrical QST measurement. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56918/56918fig1v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56918/56918fig2v2.jpg" /> 
Figure 2: Scoring sheet. N: Newton; mA: milliAmpere; VAS: visual analogue scale; EDT: Electrical detection threshold; EPT: Electrical pain threshold; CPM, Conditioned pain modulation; PA: Pressure algometry; IWB: Ice water bucket test. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56918/56918fig2v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56918/56918fig3.jpg" /> 
Figure 3: Change in pressure pain thresholds in the year following breast cancer surgery. Panels A and B show the mean &#177; SE at the early and late postoperative time points, respectively. Time points are labeled in relationship to surgery, baseline assessment was ~1 week prior to surgery. Analysis was by mixed models analysis using factors &#39;Time&#39; and &#39;Persistent Pain&#39; with Bonferroni corrected post hoc comparison of individual time points. *Different vs. patients without persistent pain at 12 months postoperatively (&#945;-level 0.05), specifically: p = 0.02 at day 5; p &#60;0.01 at day 15; p &#60;0.01 at 30 days; p = 0.02 at 3 months; p &#8804;0.01 at 6 months and; p = 0.03 at 12 months. This figure has been modified from van Helmond et al.8. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/56918/56918fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about A Quantitative Sensory Testing Paradigm to Obtain Measures of Pain Processing in Patients Undergoing Breast Cancer Surgery at JoVE.com

A Quantitative Sensory Testing Paradigm to Obtain Measures of Pain Processing in Patients Undergoing Breast Cancer Surgery

Persistent postsurgical pain may be related to changes in pain processing. By assessing pain in response to standardized stimuli, changes in pain processing can be elucidated. We present methods to obtain pain thresholds to different stimuli and a measure of endogenous analgesia in patients undergoing breast cancer surgery.

Chronic pain following surgery, persistent postsurgical pain, is an important highly prevalent condition contributing to significant symptom burden and ...

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Universidad San Sebastian

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JoVE Journal

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9.2K Views.  Radboud University Medical Center. Persistent postsurgical pain may be related to changes in pain processing. By assessing pain in response to standardized stimuli, changes in pain processing can be elucidated. We present methods to obtain pain thresholds to different stimuli and a measure of endogenous analgesia in patients undergoing breast cancer surgery.

Video: A Quantitative Sensory Testing Paradigm to Obtain Measures of Pain Processing in Patients Undergoing Breast Cancer Surgery

An Experimental Paradigm for the Prediction of Post-Operative Pain (PPOP)

Many women undergo cesarean delivery without problems, however some experience significant pain after cesarean section. Pain is associated with negative short-term and long-term effects on the mother. Prior to women undergoing surgery, can we predict who is at risk for developing significant postoperative pain and potentially prevent or minimize its negative consequences? These are the fundamental questions that a team from the University of Washington, Stanford University, the Catholic University in Brussels, Belgium, Santa Joana Women's Hospital in S&atilde;o Paulo, Brazil, and Rambam Medical Center in Israel is currently evaluating in an international research collaboration. The ultimate goal of this project is to provide optimal pain relief during and after cesarean section by offering individualized anesthetic care to women who appear to be more 'susceptible' to pain after surgery.
A significant number of women experience moderate or severe acute post-partum pain after vaginal and cesarean deliveries. 1 Furthermore, 10-15% of women suffer chronic persistent pain after cesarean section. 2 With constant increase in cesarean rates in the US 3 and the already high rate in Brazil, this is bound to create a significant public health problem. When questioning women's fears and expectations from cesarean section, pain during and after it is their greatest concern. 4 Individual variability in severity of pain after vaginal or operative delivery is influenced by multiple factors including sensitivity to pain, psychological factors, age, and genetics. The unique birth experience leads to unpredictable requirements for analgesics, from 'none at all' to 'very high' doses of pain medication. Pain after cesarean section is an excellent model to study post-operative pain because it is performed on otherwise young and healthy women. Therefore, it is recommended to attenuate the pain during the acute phase because this may lead to chronic pain disorders. The impact of developing persistent pain is immense, since it may impair not only the ability of women to care for their child in the immediate postpartum period, but also their own well being for a long period of time.
In a series of projects, an international research network is currently investigating the effect of pregnancy on pain modulation and ways to predict who will suffer acute severe pain and potentially chronic pain, by using simple pain tests and questionnaires in combination with genetic analysis. A relatively recent approach to investigate pain modulation is via the psychophysical measure of Diffuse Noxious Inhibitory Control (DNIC). This pain-modulating process is the neurophysiological basis for the well-known phenomenon of 'pain inhibits pain' from remote areas of the body. The DNIC paradigm has evolved recently into a clinical tool and simple test and has been shown to be a predictor of post-operative pain.5 Since pregnancy is associated with decreased pain sensitivity and/or enhanced processes of pain modulation, using tests that investigate pain modulation should provide a better understanding of the pathways involved with pregnancy-induced analgesia and may help predict pain outcomes during labor and delivery. For those women delivering by cesarean section, a DNIC test performed prior to surgery along with psychosocial questionnaires and genetic tests should enable one to identify women prone to suffer severe post-cesarean pain and persistent pain. These clinical tests should allow anesthesiologists to offer not only personalized medicine to women with the promise to improve well-being and satisfaction, but also a reduction in the overall cost of perioperative and long term care due to pain and suffering. On a larger scale, these tests that explore pain modulation may become bedside screening tests to predict the development of pain disorders following surgery.

An Experimental Paradigm for the Prediction of Post-Operative Pain PPOP

Diffuse noxious inhibitory control, temporal summation and wound hyperalgesia testing are demonstrated in the obstetric patient. These tests evaluate inhibitory and excitatory mechanisms of pain processing and are here utilized to evaluate endogenous analgesia at different time-points during pregnancy and the peripartum period to help reveal individual s risk for persistent pain.

Many women undergo cesarean delivery without problems, however some experience significant pain after cesarean section. Pain is associated with negative ...

Intra-Operative Behavioral Tasks in Awake Humans Undergoing Deep Brain Stimulation Surgery

Deep brain stimulation (DBS) is a surgical procedure that directs chronic, high frequency electrical stimulation to specific targets in the brain through implanted electrodes. Deep brain stimulation was first implemented as a therapeutic modality by Benabid et al. in the late 1980s, when he used this technique to stimulate the ventral intermediate nucleus of the thalamus for the treatment of tremor 1. Currently, the procedure is used to treat patients who fail to respond adequately to medical management for diseases such as Parkinson's, dystonia, and essential tremor. The efficacy of this procedure for the treatment of Parkinson's disease has been demonstrated in well-powered, randomized controlled trials 2. Presently, the U.S. Food and Drug Administration has approved DBS as a treatment for patients with medically refractory essential tremor, Parkinson's disease, and dystonia. Additionally, DBS is currently being evaluated for the treatment of other psychiatric and neurological disorders, such as obsessive compulsive disorder, major depressive disorder, and epilepsy. 
DBS has not only been shown to help people by improving their quality of life, it also provides researchers with the unique opportunity to study and understand the human brain. Microelectrode recordings are routinely performed during DBS surgery in order to enhance the precision of anatomical targeting. Firing patterns of individual neurons can therefore be recorded while the subject performs a behavioral task. Early studies using these data focused on descriptive aspects, including firing and burst rates, and frequency modulation 3. More recent studies have focused on cognitive aspects of behavior in relation to neuronal activity 4,5. This article will provide a description of the intra-operative methods used to perform behavioral tasks and record neuronal data with awake patients during DBS cases. Our exposition of the process of acquiring electrophysiological data will illuminate the current scope and limitations of intra-operative human experiments.

Deep brain stimulation surgery offers a unique opportunity to examine information encoding in the awake human brain. This article will describe intra-operative methods used to perform cognitive and behavioral tasks while simultaneously acquiring physiological data such as EMG, single-unit neuronal activity and/or local field potentials.

Deep brain stimulation (DBS) is a surgical procedure that directs chronic, high frequency electrical stimulation to specific targets in the brain through ...

Quantitative Autonomic Testing

Disorders associated with dysfunction of autonomic nervous system are quite common yet frequently unrecognized. Quantitative autonomic testing can be invaluable tool for evaluation of these disorders, both in clinic and research. There are number of autonomic tests, however, only few were validated clinically or are quantitative. Here, fully quantitative and clinically validated protocol for testing of autonomic functions is presented. As a bare minimum the clinical autonomic laboratory should have a tilt table, ECG monitor, continuous noninvasive blood pressure monitor, respiratory monitor and a mean for evaluation of sudomotor domain. The software for recording and evaluation of autonomic tests is critical for correct evaluation of data. The presented protocol evaluates 3 major autonomic domains: cardiovagal, adrenergic and sudomotor. The tests include deep breathing, Valsalva maneuver, head-up tilt, and quantitative sudomotor axon test (QSART). The severity and distribution of dysautonomia is quantitated using Composite Autonomic Severity Scores (CASS). Detailed protocol is provided highlighting essential aspects of testing with emphasis on proper data acquisition, obtaining the relevant parameters and unbiased evaluation of autonomic signals. The normative data and CASS algorithm for interpretation of results are provided as well.

Standardized, comprehensive and fully quantitative testing of autonomic functions is described. The autonomic tests consist of evaluation of all three major autonomic domains including cardiovagal, adrenergic and sudomotor. The severity and distribution of dysautonomia is quantitated using Composite Autonomic Severity Scores.

Disorders associated with dysfunction of autonomic nervous system are quite common yet frequently unrecognized. Quantitative autonomic testing can be ...

Manual Muscle Testing:  A Method of Measuring Extremity Muscle Strength Applied to Critically Ill Patients 

Survivors of acute respiratory distress syndrome (ARDS) and other causes of critical illness often have generalized weakness, reduced exercise tolerance, and persistent nerve and muscle impairments after hospital discharge.1-6 Using an explicit protocol with a structured approach to training and quality assurance of research staff, manual muscle testing (MMT) is a highly reliable method for assessing strength, using a standardized clinical examination, for patients following ARDS, and can be completed with mechanically ventilated patients who can tolerate sitting upright in bed and are able to follow two-step commands. 7, 8 
This video demonstrates a protocol for MMT, which has been taught to &ge;43 research staff who have performed &gt;800 assessments on &gt;280 ARDS survivors. Modifications for the bedridden patient are included. Each muscle is tested with specific techniques for positioning, stabilization, resistance, and palpation for each score of the 6-point ordinal Medical Research Council scale.7,9-11 Three upper and three lower extremity muscles are graded in this protocol: shoulder abduction, elbow flexion, wrist extension, hip flexion, knee extension, and ankle dorsiflexion. These muscles were chosen based on the standard approach for evaluating patients for ICU-acquired weakness used in prior publications. 1,2.

Manual Muscle Testing:  A Method of Measuring Extremity Muscle Strength Applied to Critically Ill Patients

Survivors of acute respiratory distress syndrome (ARDS) and critical illness frequently develop long-lasting muscle weakness. Manual muscle testing (MMT) is a standardized clinical examination commonly used to measure strength of peripheral skeletal muscle groups. This video demonstrates MMT using the 6-point Medical Research Council scale.

Survivors of acute respiratory distress syndrome (ARDS) and other causes of critical illness often have generalized weakness, reduced exercise tolerance, ...

Determining Pain Detection and Tolerance Thresholds Using an Integrated, Multi-Modal Pain Task Battery

Human pain models are useful in the assessing the analgesic effect of drugs, providing information about a drug&#39;s pharmacology and identify potentially suitable therapeutic populations. The need to use a comprehensive battery of pain models is highlighted by studies whereby only a single pain model, thought to relate to the clinical situation, demonstrates lack of efficacy. No single experimental model can mimic the complex nature of clinical pain. The integrated, multi-modal pain task&#160;battery presented here encompasses the electrical stimulation task, pressure stimulation task, cold pressor task, the UVB inflammatory model which includes a thermal task and a paradigm for inhibitory conditioned pain modulation. These human pain models have been tested for predicative validity and reliability both in their own right and in combination, and can be used repeatedly, quickly, in short succession, with minimum burden for the subject and with a modest quantity of equipment. This allows a drug to be fully characterized and profiled for analgesic effect which is especially useful for drugs with a novel or untested mechanism of action.

Human pain models are valuable tools used to assess the analgesic potential of novel compounds and predict their clinical efficacy, especially when used in an integrated manner. Although implementation of these models is complex, with proper execution, the pain models described in this protocol can provide predictive and reliable results.

Human pain models are useful in the assessing the analgesic effect of drugs, providing information about a drug&#39;s pharmacology and identify ...

Behavior

A Protocol of Manual Tests to Measure Sensation and Pain in Humans

Numerous qualitative and quantitative techniques can be used to test sensory nerves and pain in both research and clinical settings. The current study demonstrates a quantitative sensory testing protocol using techniques to measure tactile sensation and pain threshold for pressure and heat using portable and easily accessed equipment. These techniques and equipment are ideal for new laboratories and clinics where cost is a concern or a limiting factor. We demonstrate measurement techniques for the following: cutaneous mechanical sensitivity on the arms and legs (von-Frey filaments), radiant and contact heat sensitivity (with both threshold and qualitative assessments using the Visual Analog Scale (VAS)), and mechanical pressure sensitivity (algometer, with both threshold and the VAS). The techniques and equipment described and demonstrated here can be easily purchased, stored, and transported by most clinics and research laboratories around the world. A limitation of this approach is a lack of automation or computer control. Thus, these processes can be more labor intensive in terms of personnel training and data recording than the more sophisticated equipment. We provide a set of reliability data for the demonstrated techniques. From our description, a new laboratory should be able to set up and run these tests and to develop their own internal reliability data.

The goal of this procedure is to demonstrate a battery of quantitative techniques for sensory and pain measurement in humans. The equipment and techniques described are commonly found in pain clinics or are easy to obtain.

Numerous qualitative and quantitative techniques can be used to test sensory nerves and pain in both research and clinical settings. The current study ...

Multi-Modal Signals for Analyzing Pain Responses to Thermal and Electrical Stimuli

The assessment of pain relies mostly on methods that require a person to communicate. However, for people with cognitive and verbal impairments, existing methods are not sufficient as they lack reliability and validity. To approach this problem, recent research focuses on an objective pain assessment facilitated by parameters of responses derived from physiology, and video and audio signals. To develop reliable automated pain recognition systems, efforts have been made in creating multimodal databases in order to analyze pain and detect valid pain patterns. While the results are promising, they only focus on discriminating pain or pain intensities versus no pain. In order to advance this, research should also consider the quality and duration of pain as they provide additional valuable information for more advanced pain management. To complement existing databases and the analysis of pain regarding quality and length, this paper proposes a psychophysiological experiment to elicit, measure, and collect valid pain reactions. Participants are subjected to painful stimuli that differ in intensity (low, medium, and high), duration (5 s / 1 min), and modality (heat / electric pain) while audio, video (e.g., facial expressions, body gestures, facial skin temperature), and physiological signals (e.g., electrocardiogram [ECG], skin conductance level [SCL], facial electromyography [EMG], and EMG of M. trapezius) are being recorded. The study consists of a calibration phase to determine a subject&#8217;s individual pain range (from low to intolerable pain) and a stimulation phase in which pain stimuli, depending on the calibrated range, are applied. The obtained data may allow refining, improving, and evaluating automated recognition systems in terms of an objective pain assessment. For further development of such systems and to investigate pain reactions in more detail, additional pain modalities such as pressure, chemical, or cold pain should be included in future studies. Recorded data of this study will be released as the &#8220;X-ITE Pain Database&#8221;.

This article focuses on the experimental elicitation of pain through heat (thermal) and electrical stimulation while recording physiological, visual, and paralinguistic responses. It aims at collecting valid multimodal data for analyzing pain based on its intensity, quality, and duration.&#160;

The assessment of pain relies mostly on methods that require a person to communicate. However, for people with cognitive and verbal impairments, existing ...

Dynamic Quantitative Sensory Testing to Characterize Central Pain Processing

Central facilitation and modulation of incoming nociceptive signals play an important role in the perception of pain. Disruption in central pain processing is present in many chronic pain conditions and can influence responses to specific therapies. Thus, the ability to precisely describe the state of central pain processing has profound clinical significance in both prognosis and prediction. Because it is not practical to record neuronal firings directly in the human spinal cord, surrogate behavior tests become an important tool to assess the state of central pain processing. Dynamic QST is one such test, and can probe both the ascending facilitation and descending modulation of incoming nociceptive signals via TS and CPM, respectively. Due to the large between-individual variability in the sensitivity to noxious signals, standardized TS and CPM tests may not yield any meaningful data in up to 50% of the population due to floor or ceiling effects. We present methodologies to individualize TS and CPM so we can capture these measures in a broader range of individuals than previously possible. We have used these methods successfully in several studies at the lab, and data from one ongoing study will be presented to demonstrate feasibility and potential applications of the methods.

By assessing pain in response to repetitive or different types of standardized stimuli, dynamic quantitative sensory testing (QST) can reveal changes in the central processing of pain. We present methods to optimize and individualize two dynamic QST measures: temporal summation (TS) and conditioned pain modulation (CPM).

Central facilitation and modulation of incoming nociceptive signals play an important role in the perception of pain. Disruption in central pain ...

Neuroscience

Assessment of Sensory Thresholds in Dogs Using Mechanical and Hot Thermal Quantitative Sensory Testing

Quantitative sensory testing (QST) is used to evaluate the function of the somatosensory system in dogs by assessing the response to applied mechanical and thermal stimuli. QST is used to determine normal dogs&#39; sensory thresholds and evaluate alterations in peripheral and central sensory pathways caused by various disease states, including osteoarthritis, spinal cord injury, and cranial cruciate ligament rupture. Mechanical sensory thresholds are measured by electronic von Frey anesthesiometers and pressure algometers. They are determined as the force at which the dog exhibits a response indicating conscious stimulus perception. Hot thermal sensory thresholds are the latency to respond to a fixed or ramped temperature stimulus applied by a contact thermode.
Following a consistent protocol for performing QST and paying attention to details of the testing environment, procedure, and individual study subjects are critical for obtaining accurate QST results for dogs. Protocols for the standardized collection of QST data in dogs have not been described in detail. QST should be performed in a quiet, distraction-free environment that is comfortable for the dog, the QST operator, and the handler. Ensuring that the dog is calm, relaxed, and properly positioned for each measurement helps produce reliable, consistent responses to the stimuli and makes the testing process more manageable. The QST operator and handler should be familiar and comfortable with handling dogs and interpreting dogs&#39; behavioral responses to potentially painful stimuli to determine the endpoint of testing, reduce stress, and maintain safety during the testing process.

This work describes a standard protocol for mechanical and hot thermal quantitative sensory testing to evaluate the somatosensory system in dogs. Sensory thresholds are measured using an electronic von Frey anesthesiometer, pressure algometer, and hot contact thermode.

Quantitative sensory testing (QST) is used to evaluate the function of the somatosensory system in dogs by assessing the response to applied mechanical ...

A Novel Approach for Pain Assessment from Pain Body Diagrams

Quantifying Pain Location and Intensity with Multimodal Pain Body Diagrams

To quantify an individual&#39;s subjective pain severity, standardized pain rating scales such as the numeric rating scale (NRS), visual analog scale (VAS), or McGill pain questionnaire (MPQ) are commonly used to assess pain on a numerical scale. However, these scales are often biased and fail to capture the complexity of pain experiences. In contrast, clinical practice often requires patients to report areas of pain by drawing on a body diagram, which is an effective but qualitative tool. The method presented here extracts quantifiable metrics from pain body diagrams (PBDs) which are validated against the NRS, VAS, and MPQ pain scales. By using a novel pressure-hue transformation on a digital tablet, different drawing pressures applied with a digital stylus can be represented as different hues on a PBD. This produces a visually intuitive diagram of hues ranging from green to blue to red, representing mild to moderate to most painful regions, respectively. To quantify each PBD, novel pain metrics were defined: (1) PBD mean intensity, which equals the sum of each pixel&#39;s hue value divided by the number of colored pixels, (2) PBD coverage, which equals the number of colored pixels divided by the total number of pixels on the body, and (3) PBD sum intensity, which equals the sum of all pixels&#39; hue values. Using correlation and information theory analyses, these PBD metrics were shown to have high concordance with standardized pain metrics, including NRS, VAS and MPQ. In conclusion, PBDs can provide novel spatial and quantitative information that can be repeatedly measured and tracked over time to comprehensively characterize a participant&#39;s pain experience.

Author Spotlight: Quantifying Pain Experience &#8211; An Illustrative Approach Using the Pain Body Diagram 

Current pain scales used to quantify pain severity, such as visual analog scales, fail to capture the complexity of subjective pain experiences. Pain body diagrams are qualitative but may be more informative. The goal of this method is to extract quantitative metrics from pain body diagrams using novel pressure-hue transformation.

To quantify an individual&#39;s subjective pain severity, standardized pain rating scales such as the numeric rating scale (NRS), visual analog scale ...