VOL: 102, ISSUE: 42, PAGE NO: 30
Brendan Docherty, MSc, PGCE, RN, is nurse manager, patient access and nursing services
Steven Coote, MN (Critical Care), BN, RN, is advanced practice nurse, after hours nursing services; both at The Prince of Wales Hospital, Sydney, Australia
Blood pressure is a measurement of the force against the artery walls, and is an indicator of cardiac competence, f…
Blood pressure is a measurement of the force against the artery walls, and is an indicator of cardiac competence, fluid balance and peripheral vascular resistance (Tortora and Grabowski, 2002). An abnormality in blood pressure is usually related to one or several of these components.
In community settings, blood pressure abnormalities are usually chronic issues and are managed as part of an existing condition (for example heart failure, chronic renal failure or hyperlipidaemia).
In acute care settings, abnormalities in blood pressure can range from being a transient change in normal systemic pressure due to pain or vasovagal response, to being a symptom of shock as a result of acute myocardial infarction, sepsis or hypovolaemia from trauma (RCUK, 2005; Smith, 2000). The challenge for the practitioner is to recognise and react adequately to blood pressure changes. This article will focus on issues related to blood pressure in the acute phase in secondary care.
Each practitioner should consider the following elements in the holistic care of patients (RCUK, 2005; Smith 2000):
- The patient’s relevant medical and social history. Many patients have co-morbidities that might impact on the clinical findings;
- The trend of the previous blood pressure recordings to identify any patterns and relate them to the patient’s usual blood pressure;
- Relevant links. For example, when did the patient return from theatre? Is she or he pyrexial? What is the heart rate, the urine output and the fluid input? Is the patient anxious or in pain?
- Necessary observations and frequency of those observations - blood pressure recordings, pulse rate, 12-lead ECG to identify cardiac abnormalities, 3-lead ECG monitor, neurological observations;
- The solution to reverse the problem and how to stabilise the patient’s condition if interventions are required.
Measuring blood pressure
The procedure for measuring the blood pressure, and some other factors to consider, are summarised as follows (Tortora and Grabowski, 2002; Docherty, 2002):
- The arm should be slightly flexed and at heart level. The patient should be relaxed;
- The cuff should be placed on the left arm (closest to the heart) and should be the correct size for the arm circumference. A cuff which is too small (restrictive) or too large (loose) will not give accurate readings;
- The radial pulse should be palpated when inflating the cuff for the first time to check for where the pulse disappears. This indicates when the pressure of the cuff is greater than the systolic BP and ensures that the cuff is not over-inflated, possibly causing discomfort to the patient;
- After cuff inflation, the brachial artery should be monitored with a stethoscope. The first entry sound is the systolic pressure and the last sound is the diastolic pressure;
- Automated machines may have to be calibrated to each individual patient (that is, two recordings are necessary), and may be less accurate in hypotension.
Hypotension is the reduction of systemic blood pressure for that patient. As a guide a systolic blood pressure (SBP) less than 90mmHg is considered hypotensive (Adam and Osborne, 2005).
A mean blood pressure (MBP) less than 60mmHg indicates that the perfusion pressure of vital organs such as the kidneys is being impeded.
The inability to perfuse organs due to a loss of systemic blood pressure leads to organ, tissue and cellular failure and ultimately death (Adam and Osborne, 2005; RCUK, 2005). However, the MBP measurement is not always available on electronic devices. It can be calculated using this equation: MBP = diastolic BP + 1/3 (systolic BP - diastolic BP).
The general risk in hypotension is loss of systemic circulatory pressure needed to perfuse and deliver oxygen and essential metabolic requirements to the patient’s vital organs (for example kidneys, heart, brain, lungs). This may result in organ failure, confusion, metabolic compromise, hypoxia and cellular death (Adam and Osborne, 2005; Smith, 2000). Therefore quick assessment is essential. However, it is important to remember that in younger people with good exercise tolerance a low blood pressure may be the norm due to good cardiac function.
In the ward setting patients’ blood pressure readings will vary throughout a shift, therefore monitoring is essential in acute care settings to identify adverse trends in a patient’s blood pressure.
Raised blood pressure, particularly systolic blood pressure, is directly related to increased risk of cardiovascular events and death. The current definition of hypertension is a blood pressure above the patient’s therapeutic plan in the context of their cardiovascular risk factors (Heart Foundation, 2004).
In the clinical context a diagnosis of hypertension should be made based on recordings taken on several occasions.
Factors influencing hypertension include:
- Reasons for hospitalisation (surgery, pain);
- Smoking history;
- Lipidaemia status;
- Renal disease/impairment;
- Raised body mass index.
In the acute clinical setting hypertensive emergencies can occur. These life-threatening events may stem directly from the patient’s clinical problem such as recent head trauma or neurosurgery.
They could also be iatrogenic in nature related to the withholding of a patient’s antihypertensive medications due to fasting for theatre (Adam and Osborne, 2005; Singer and Webb, 2005).
Hypertensive crisis is diagnosed when systolic BP (gt) 180mmHg and diastolic BP (gt) 115mmHg (Joint National Committee, 2003). As a patient’s ability to autoregulate cerebral bloodflow ceases at a MBP of 120mmHg she or he is vulnerable to acute cardiovascular events (Singer and Webb, 2005). The patient may have varying signs of hypertension including headache, nausea, epistaxis, chest pain and dyspnoea or palpitations. Or the patient’s first sign of distress may be them stating ‘I don’t feel right’ (Joint National Committee, 2003).
- Define blood pressure and the factors that influence it
- Identify low blood pressure, the possible causes and the nursing care required
- Identify high blood pressure, the possible causes and the nursing care required
- Develop a systematic problem-solving approach in the care of patients who have blood pressure abnormalities
- Outline your place of work and why you were interested in this article
- Detail the last time you encountered a patient with abnormal blood pressure readings
- Write about a piece of information in the article that could have helped in your care of that patient
- Explain how you intend to disseminate what you have learnt among your colleagues
This article has been double-blind peer-reviewed