Noninvasive measurements of normal values of stroke volume and total peripheral resistance accounting for age and sex differences

Objective: Clinical management guidelines generally provide ideal ranges for stroke volume (SV) and total peripheral resistance (TPR) [1] and rarely provide detailed normal values addressing age and sex, particularly in the elderly population. This has likely impact on anaesthesia management in surgery and critical care and may impact other clinical fields. This study quantifies SV and TPR in older age. Design and method: 1051 (579 female) participants 50–100 years old presenting for a range of surgeries were studied at rest pre-surgery. SV was determined noninvasively using either the Vigileo Flotrac (Edwards Life Sciences) or Uscom 1A (USCOM) device. Coupled with blood pressure measurement, SV and TPR were calculated and cross-sectional differences were quantified in relation age, sex, and body mass and surface area. Results: At any age, SV and TPR differed in males and females and correlated with body mass index and body surface area. In both sexes, SV decreased and TPR rose for each decade. In females between the 6th and 10th decades, mean resting SV fell from 84 ± 14 mL to 40 ± 6 mL (outside “normal” range of 60–100 ml [1]), and TPR rose from 1200 ± 240 dynes.sec/cm5 to 2720 ± 480 dynes.sec/cm5 (above “normal” range of 1000–1500 dynes.sec/cm5 [1]). In males, mean resting SV fell from 111 ± 23 mL to 64 ± 10) mL (within “normal” range) and TPR rose from 1040 ± 160 dynes.sec/cm5 to 1600 ± 240 dynes.sec/cm5 (marginally above “normal” range). Conclusions: SV and TPR as reported by the Vigileo Flotrac and Uscom 1A devices move outside the generally accepted “normal” range for older individuals. This may either be due to the algorithms used for noninvasive calculation of SV and TPR, or may mean that “normal” values need to be revisited for older individuals, which will require confirmatory evidence by direct or invasive methods.