Dissociation between reduced pain and arterial blood pressure following epidural spinal cord stimulation in patients with chronic pain: A retrospective study.

PURPOSE: Acute pain and resting arterial blood pressure (BP) are positively correlated in patients with chronic pain. However, it remains unclear whether treatment for chronic pain reduces BP. Therefore, in a retrospective study design, we tested the hypothesis that implantation of an epidural spinal cord stimulator (SCS) device to treat chronic pain would significantly reduce clinic pain ratings and BP and that these reductions would be significantly correlated. METHODS: Pain ratings and BP in medical records were collected before and after surgical implantation of a SCS device at the University of Iowa Hospitals and Clinics between 2008 and 2018 (n = 213). RESULTS: Reductions in pain rating [6.3 ± 2.0 vs. 5.0 ± 1.9 (scale: 0-10), P < 0.001] and BP [mean arterial pressure (MAP) 95 ± 10 vs. 89 ± 10 mmHg, P < 0.001] were statistically significant within 30 days of SCS. Interestingly, BP returned toward baseline within 60 days following SCS implantation. Multiple linear regression analysis showed that sex (P = 0.007), baseline MAP (P < 0.001), and taking hypertension (HTN) medications (P < 0.001) were significant determinants of change in MAP from baseline (Δ MAP) (model R2 = 0.33). After statistical adjustments, Δ MAP was significantly greater among women than among men ( - 7.2 ± 8.5 vs.  - 3.9 ± 8.5 mmHg, P = 0.007) and among patients taking HTN medications than among those not taking hypertension medications ( - 10.1 ± 8.7 vs.  - 3.9 ± 8.5 mmHg, P < 0.001), despite no group differences in change in pain ratings. CONCLUSIONS: Together, these findings suggest that SCS for chronic pain independently produces clinically meaningful, albeit transient, reductions in BP and may provide a rationale for studies aimed at reducing HTN medication burden among this patient population.