VOL: 103, ISSUE: 20, PAGE NO: 24 Phil Jevon, PGCE, BSc, RN, is resuscitation officer/clinical skills lead, Manor Hospital, Walsall, and honorary clinical lecturer, University of Birmingham Medical School John Holmes, MA, Cert Ed, DPNS, RMN, RN, is senior lecturer, pre-registration adult nursing, University of Wolverhampton In healthy patients there is normally little difference between lying and standing blood pressure.

However, a significant fall (20mmHg or more) can occur in older people, patients with diabetes and those with symptoms suggesting postural hypotension (British Hypertension Society, 2006). It is advisable to measure both lying and standing blood pressure routinely in these patients.

Blood pressure measurement in the presence of atrial fibrillation, particularly when the ventricular rhythm is extremely irregular, is unreliable and may be improved with repeated measurements. Some automated devices may provide unreliable readings in the presence of atrial fibrillation (O’Brien et al, 2003). Auscultation using a mercury device may provide a more accurate reading.

POSTURAL HYPOTENSION

Postural or ‘orthostatic’ hypotension is the occurrence of an abnormally low blood pressure when a person suddenly stands up, typically inducing dizziness and syncope. It affects 10-33% of all elderly people (Patel et al, 1993), its prevalence increases with advancing age (Mathias and Kimber, 1999) and it can complicate a variety of diseases, such as diabetes. It can present as dizziness, syncope and falls on changing position. Although it may seem relatively harmless, safety and quality of life can be affected.

RELEVANT PHYSIOLOGY

The main function of maintaining blood pressure is to ensure adequate perfusion of organs, particularly when demands increase. This relies on the integrity of the heart and blood vessels, maintenance of intravascular volume and various vasoactive agents (Mathias and Kimber, 1999).

Blood pressure is in part regulated by baroreceptors in the aortic arch, carotid arteries and carotid sinus. By influencing heart rate and peripheral vascular resistance (via the autonomic nervous system), they help to compensate for transient changes.

Age-related changes in these mechanisms can precipitate postural hypotension. The baroreflex-mediated heart rate response to both hypotensive and hypertensive stimuli can become impaired. In addition, blood pressure regulation can be affected by age and disease-related cardiovascular changes such as atherosclerosis. Arterioles are less able to constrict in response to rapid changes in position. Older people are consequently more susceptible to postural hypotension.

CAUSES AND RISK FACTORS

Although postural hypotension can occur in healthy elderly people, it is more common in those with extra risk factors, particularly prolonged bedrest and an age of over 74. It can complicate many conditions, including hypovolaemia and diabetes, and can be caused by a number of medications, such as diuretics and antihypertensives.

MEASUREMENT

- Ensure the patient has been lying down for at least five minutes and is relaxed (Fig 1).

- Explain the procedure and obtain consent.

- Ask the patient to remove any tight clothing from around their arm.

- Ensure the arm is supported at the level of the heart - on a pillow, for example.

- Select an appropriately sized cuff: its bladder should encircle at least 80% of the arm but no more than 100% (Fig 2).

- Place the cuff snugly onto the patient’s arm with the centre of the bladder over the brachial artery. Most cuffs have a ‘brachial artery indicator’, an arrow that can be aligned with the artery.

- Ask the patient to refrain from talking or eating during the procedure as this can result in an inaccurate higher blood pressure measurement being recorded.

- Switch on the automated device (Fig 3) and press start.

- Document the systolic and diastolic blood pressures on the patient’s observation chart.

- Leave cuff in place and ask patient to stand (Fig 4), ensuring their safety.

- Allow the patient to stand for one minute.

- Ensure the arm is supported at heart level.

- Press start.

- Help the patient to sit or lie down.

- Document the readings (Fig 5).

- Switch off automated device, remove cuff and recharge battery if necessary (Fig 6).

- Compare with previous readings and inform nurse in charge/medical team (BHS, 2006; NICE and BHS, 2006).

PROFESSIONAL RESPONSIBILITIES

This procedure should be undertaken only after approved training, supervised practice and competency assessment, and should be carried out in accordance with local policies and protocols.

This article has been double-blind peer-reviewed.