Length of time required to achieve a stable baseline blood pressure in the diagnosis of orthostatic hypotension.

Diagnosis of orthostatic hypotension (OH) is essential because the consequences include morbidity and mortality 1, 2. Prevalence is estimated to be as high as 6% in community-dwelling older adults and 65% in older person's care facilities 3. Diagnosis depends entirely on a drop in systolic or diastolic blood pressure (BP) from baseline. Baseline is typically estimated after a period of supine rest. The rationale behind the supine rest is to establish a stable baseline, improving the precision of diagnosis, but how long is needed to reach a stable baseline remains uncertain, if it can be reached at all. The aim of this study was to identify the minimum time of supine rest required to achieve a stable baseline BP. METHODS All consecutive patients attending the Newcastle upon Tyne Hospitals National Health Service Foundation Trust Falls and Syncope Service who consented for their clinical data to be used for research were recruited between February and May 2009. Patients with OH aged 65 and older were matched to a non-OH case for age, sex, diabetes mellitus, and antihypertensive medication (diagnoses in controls included noncardiovascular falls, vertigo, peripheral neuropathy). Those with arrhythmias were excluded. Each patient underwent a 10-minute supine rest while recording a continuous, noninvasive electrocardiogram and beat-to-beat BP using digital plethysmography 2 (Taskforce, CNSystems, Graz, Austria). They were then assisted to a standing position to assess for OH. Mean BP was calculated for each minute of rest. The coefficient of variability (Cv=standard deviation/mean ×100) was calculated for each minute as a measure of BP variability. OH was diagnosed using the BP recordings alongside a clinical assessment by an experienced clinician. Repeated-measures analysis of variance was performed to identify statistically significant differences between consecutive minutes; results were considered significant when p <.05. Permission to perform the study was granted by the local reseaerch and ethics review panel. RESULTS Of 336 consecutive patients, 208 were aged 65 and older (median 76, maximum 90), and among these, 36 cases of OH were identified. Each group was 44% female, 11% with diabetes mellitus, and 31% on antihypertensive medication. Forty-seven percnet of those with OH were taking fludrocortisone, midodrine, or both. BP trends over 10 minutes can be seen in Figure 1, with all significant changes occurring within the first 4 minutes. During the initial rest period, the BP of those without OH declined much more sharply than that of those with OH. Variability of systolic …