Spinal cord injury (SCI) is associated with rapid and sustained impairments in cardiovascular function that ultimately cause an early onset of cardiovascular disease. We know remarkably little about the temporal progression of cardiovascular disturbances, but such an understanding is critical to inform clinical management and develop appropriate intervention strategies. To characterize the cardiovascular response to SCI, six male Wistar rats were instrumented with telemetry and assessed for continuous arterial blood pressure (BP), core body temperature, and heart rate (HR) 7 days before and up to 28 days after T3 SCI. Hemodynamic variables were averaged day by day and hour by hour. Spontaneously occurring autonomic dysreflexia (AD) was characterized by applying a novel algorithm to continuous BP and HR data, and induced AD was assessed weekly via the BP response to colorectal distension. Systolic BP was reduced at all time points after SCI compared with before SCI (p<0.003), except at 4 and 6 days post-injury. Core body temperature was reduced at 2 days post-SCI only (p=0.001). The nocturnal dip in BP and temperature observed pre-SCI was absent during the first 14 days post-SCI, but returned from 21 days post-SCI on (p<0.024). The frequency and severity of spontaneously occurring AD events were significantly less between days 6 and 10 post-SCI compared all other time points (p<0.037). The pressor response to colorectal distension was greater at 14, 21, and 28 days post-SCI compared with at 7 days post-SCI (all p<0.004). In conclusion, SCI induces rapid and profound alterations in basal hemodynamics and diurnal rhythms that partially recover by 14 days post-SCI. AD, on the other hand, is acutely present post-SCI, but the frequency and severity of AD events increase substantially from 14 days post-SCI on.
Keywords: BP; circadian oscillations; hemodynamics; hypertension.