Why the study?
Elevations in shock index are less discriminative of impending shock in older adults, and baroreflex dysfunction was hypothesized as a potential explanation for lower baseline values.
Autonomic dysfunction is associated with a lower shock index in older adults, which may mask signs of circulatory instability.
Autonomic dysfunction may blunt SI response in older adults; hypothesis-generating for age-adjusted shock thresholds.
• The shock index (SI) is calculated as heart rate/systolic blood pressure. • We demonstrated a negative association between autonomic dysfunction and SI. • Age and chronic illness-related autonomic dysfunction might be one explanation. Elevations in shock index (SI), defined as heart rate (HR)/systolic blood pressure (BP) are less discriminative of impending shock in older adults. We hypothesized baroreflex dysfunction as a potential explanation for lower baseline SI in older adults. 52 older adults (29 women, 23 men, age ≥ 65; mean age 77.8 ± 0.9 years) were recruited. SI, the modified shock index (MSI, HR/mean BP), and the age corrected SI (Age * SI) as well as baroreflex function (using the sequence method) was measured at baseline. SI (Standardized β = 0.392, p = 0.005), MSI (Standardized β = 0.385, p = 0.006) and Age * SI (Standardized β = 0.431, p = 0.002) showed significant positive associations with BRS up . Age * SI also showed a significant positive association with BRS (Standardized β = 0.329, p = 0.019). Autonomic dysfunction is associated with lower SI in older adults, potentially masking circulatory instability. ClinicalTrials.gov ID NCT01914133
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Madden et al. (2025) studied this question.
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