What is Hypotension (Low Blood Pressure)?
In general, low blood pressure can be thought of as a rate, pump or volume problem.
Bradycardia or tachycardia can cause a decrease in blood pressure. Problems with the pump - that is the heart function - may be things such as a myocardial infarction or cardiogenic shock causing low blood pressure. Other conditions such as hypothermia or cardiac depressant medications can cause low blood pressure by affecting the pump.
Perhaps the most common etiology of low blood pressure encountered clinically would be volume problems from things such as hypovolaemic shock, severe dehydration, haemorrhage or septic shock, anaphylaxis and neurogenic shock from spinal cord injury, are reasonably common causes of low blood pressure.
Low blood pressure should be evaluated and treated urgently. An assessment of low blood pressure should include a recheck of the pressure and close monitoring. If a client has recently changed positions, they should be returned to a supine position and rechecked in a few minutes.
Orthostasis literally means, ‘standing upright’. Orthostatic hypotension is defined as a decrease in systolic blood pressure of at least 20 mmHg, or at least 10 mmHg diastolic, within 3 minutes of the patient standing. If orthostatic hypotension is encountered, then the client is at risk of falls and should be closely supervised with ambulation or advised to call for assistance with the activity.
To test for orthostatic hypotension, take the blood pressure whilst the patient is supine and at rest, then stand the patient. They must be able to stand for 3 minutes before taking the blood pressure again.
If the measurements meet the criteria stated previously, then orthostatic hypotension is evident.
If the result is equivocal, record that and request a formal assessment.