Reproducibility of orthostatic changes in cerebral oxygenation in healthy subjects aged 70 years or older.

Abstract

In the elderly, standing can frequently be accompanied by blood pressure (BP) changes and cerebral symptoms such as dizziness, fall, or even syncope, but this may vary from day-to-day. Therefore, we aimed to investigate the reproducibility of orthostatic responses of cerebral cortical oxygenation and systemic haemodynamics in elderly subjects. In 27 healthy elderly subjects (age 70-84 years), changes in systolic BP (SBP), diastolic BP (DBP), heart rate (HR) and stroke volume (SV) were continuously monitored by Finapres (Finger Arterial Pressure), and changes in oxyhaemoglobin ([O2Hb]) and deoxyhaemoglobin ([HHb]) concentrations were continuously measured over the right frontal cortex by near infrared spectroscopy (NIRS) during supine rest and 10 min of active standing on two separate occasions. SBP and DBP increased by 6.7 +/- 15.4 mmHg (P<0.05, mean +/- SD) and 8.2 +/- 6.4 mmHg (P<0.01), respectively, whereas HR increased by 9.5 +/- 5.0 bpm (P<0.01) and SV decreased by -8.3 +/- 7.4 ml (P<0.01) during standing on the first occasion. [O2Hb] decreased by -3.9 +/- 2.9 micromol l-1 (P<0.01), while [HHb] increased by 1.8 +/- 2.2 micromol l-1 (P<0.01). Group-averaged orthostatic changes in cortical oxygenation and systemic haemodynamics were very similar on the two occasions, although an intraindividual variation was found. Cortical oxygenation changes were not accompanied by severe cerebral symptoms. Active standing induced reproducible group-averaged frontal cortical oxygenation declines in healthy elderly subjects, although an intraindividual day-to-day variability was present, possibly related to the variability of orthostatic BP responses. These findings indicate that cerebral autoregulation fails to compensate completely for postural changes in elderly subjects, which might predispose elderly subjects to ischaemic cerebral symptoms.