Between-visit Reproducibility Of Pain, Sympathetic, And Blood Pressure Responses During The Cold Pressor Test

Interindividual differences exist in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) responses to the pain-evoking cold pressor test (CPT). One study examined between-visit reproducibility of MSNA (peroneal) and BP responses during the CPT, but did not measure pain perception in the 13 assessed adults. Therefore, we performed a retrospective analysis to examine the between-visit reproducibility of pain, BP, and MSNA responses during the CPT. PURPOSE: Based on past work we tested the hypothesis that reproducibility would be good for pain, very good for BP responses, and moderate for MSNA responses during the CPT. METHODS: During two experimental visits ≥48 hours apart, we continuously measured MSNA via radial microneurography and beat-to-beat BP via finger photoplethysmography during a 10-minute baseline and a 2-minute CPT (hand in 0.34 ± 0.05 °C ice bath). We assessed pain perception using a 10 cm visual analog scale. The left anchor [0 cm] was “no pain,” and the right anchor [10 cm] was “worst imaginable pain.” We calculated the changes in (Δ) MSNA and BP as CPT minute two minus baseline. We report data as mean ± SD or median [IQR] and calculated intraclass correlation coefficients (ICC). RESULTS: We tested 20 young adults (age = 30 ± 6 yrs; body mass index = 26 ± 3 kg/m2) who were free from overt disease and were not taking pain-modifying medications. Baseline mean BP had very good reproducibility (88 ± 8 mmHg; ICC = 0.78) and baseline MSNA burst frequency had moderate reproducibility (12[6] bursts/min; ICC = 0.41). During the CPT, perceived pain had excellent reproducibility (7.3[2.3] cm; ICC = 0.91), Δmean BP had good reproducibility (Δ19 ± 9; ICC = 0.71), and ΔMSNA burst frequency had poor reproducibility (Δ17[16] bursts/min; ICC = 0.14). ΔMSNA total activity had poor reproducibility before (325[394]% of baseline; ICC = -0.12) and moderate reproducibility after (325[379]% of baseline; ICC = 0.41) removing two statistical outliers (>3*IQR above median). CONCLUSION: These results suggest excellent reproducibility for pain, good reproducibility for Δmean BP, and poor-to-moderate reproducibility for ΔMSNA indices during the CPT. Since our results for ΔMSNA and Δmean BP differed from previous work, more research may be warranted to better understand the reproducibility of responses during the CPT. Supported by: LNB was supported by the National Institutes of Health (NIH; F32HL154565). This research was supported by the United States Army (W81XWH-18-2-0012 to CGC). JCW was supported by the American Physiological Society (Postdoctoral Fellowship), the NIH (F32HL154559 & K01HL160772), and the American Heart Association (23CDA1037938).