Prevalence of Impaired Orthostasis after Concussion Injury

Abstract

To determine the prevalence of orthostatic hypotension (OHypo) and hypertension (OHTN), respectively after a concussion in collegiate athletes. Orthostasis causes a gravity-dependent redistribution of blood volume to the lower extremities. The baroreflex coordinates the cardiovascular autonomic nervous system to mitigate aberrant changes in systolic blood pressure (SBP). In autonomic dysfunction (AD), impaired accommodation may lead to a clinically significant? SBP decreases (OHypo: SBP fall = 20 mm Hg) or paradoxical increases (OHTN: SBP rise = 20 mm Hg) within 3 minutes of assuming the standing (STND) posture. Concussion injuries may induce a transient state of AD. A clinical approach to surveil this state has yet to be defined. A prospective study was performed in 36 concussed (gender: 23 female, 13 male; age: 20 ± 1 years; height: 1.75 ± 0.12 meters; weight: 73 ± 14 kilograms) and 20 non-concussed athletes (gender: 12 female, 8 male; age: 21 ± 2 years; height: 1.74 ± 0.15 meters; weight: 72 ± 18 kilograms). Continuous beat-to-beat SBP was collected for 10-minutes in a resting supine position (SUP) and then for 3-minutes in the STND position within 48 hours (48H) of concussion. The average SBP was computed from the difference between SUP and the final 15 seconds of STND. SBP were then categorized: Normal (NR: SBP -15 to +15 mm Hg); Borderline OHypo (BordOHypo: SBP -16 to -19 mm Hg) and OHTN (BordOHTN: SBP +16 to +19 mm Hg); OHypo; and, OHTN. In concussed athletes, the SBP prevalence rates were 42% NR, 31% OHypo, 11% OHTN, 11% BordOHTN, and 6% BordOHypo compared to 90% NR, 5% OHypo and 5% OHTN in the non-concussed athletes. ?2 test revealed a significant difference in this distribution (p = 0.012). Within 48H of concussion injury, a combined 42% of injured athletes had an abnormal SBP response to orthostasis and a further 6% had borderline responses that warrant re-evaluation. The incidence rates for each circumstance exceeded the control group.