Research Applied to Clinical Practice
by Robert C. Knies, RN MSN CEN
Section Editor
Orthostatic Measurement
Definition:
Orthostatic, tilt or postural vital signs (VS) are serial measurements of blood pressure (B/P) and pulse that are taken with the patient in the supine, sitting, and standing positions, results are used to assess possible volume depletion. This test is commonly performed on patients who complain of; nausea, vomiting, diarrhea, GI bleed, and syncope. The results can help the practitioner decide if the patient needs fluid replacement, more extensive testing or treatment.
Possible Causes:
Diseases |
Medications |
|
| Addison’s disease | Anemia | Diuretics |
| Autonomic disorders | Diabetes Mellitus | Calcium Channel blockers |
| Hyponatremia | Mitral valve prolapse | Alpha-adrenergic blockers |
| Nephrotic syndrome | Neurologic diseases | Ganglionic blocking drugs |
| Recent brain attack | Pheochromocytoma | Tricyclic antidepressants |
| Toxic shock syndrome | Prolonged bed rest | MAO inhibitors |
| Alcohol consumption | Post partal bleeding | |
| Chronic Fatigue Syndrome | ||
Normal Pathophysiology:
When a patient stands, gravity causes blood to pool in the large vessels of the legs and lower trunk (up to 500ml). Normally, baroreceptors in the aortic arch and carotids sense this change in blood pressure/volume and stimulate an endocrine, catecholamine, renin/aldosterone response. This response causes the peripheral blood vessels to constrict, the heart rate and contractility to increase, and the kidneys to hold fluids. This action pulls blood into the core circulation to supply the primary organs (heart, lungs, kidneys, liver and brain).
In patients who are volume depleted (hypovolemic), there is not enough circulating blood to be pushed into core circulation, especially when the patient moves from the supine to sitting or standing. That is why clinicians think a positive tilt is indicative of volume depletion, and institute replacement while awaiting other test results.
There is little agreement as to what indicates a significant orthostatic change and what is considered a positive tilt test. The "20-10-20" rule may be used as a guide for this. The rule refers to the expected decrease in systolic B/P (up to 20 mm Hg), a rise in diastolic B/P of 10 mm HG and an increase in heart rate by 20 beats per minute.
Measurement Techniques:
1. There is controversy as to length of wait between moving to a new position and taking VS. Most studies and experts agree that a one minute wait between movement is satisfactory.
2. For consistency the same arm with the same cuff and same location of pulse measurement should be used. This is easily accomplished by using electronic measuring devices.
Supine- The patient needs to lie supine, without pillows, for two to three minutes before measuring VS. * If supine position compromises patient’s breathing status or comfort level, assist them to a position as flat as possible. It is a good technique to obtain two sets of measurement while the patient is supine and use the second set as the baseline. This is done due to the normal sympathetic response (alerting reaction) which can cause false positives by initially raising the systolic B/P.
Sitting- Taking measurements with the patient in this position is controversial, some say the elevation is not significant enough to cause a change, other say that this in-between position causes false negatives by providing a chance for the body to adjust before changing to the standing position. * If the patient is not able to stand this is the next position after supine. Whenever measuring at this position the patient should be sitting upright, with their legs dangling at the side of the bed.
Standing- If the patient ambulated to the treatment area, and there are no signs of syncope, the sitting position can be avoided
Documentation:
Using symbols i.e., o-<--< =lying; o|_=sitting; =standing, or writing out the name of the position and the results at each position are necessary. You should also indicate whether the pulse was regular and if on a monitor, document rhythm. Also include any symptoms the patient reports as well as your clinical observations, but do not pose leading questions like, "are you dizzy?" Lastly, if fluid replacement is ordered, after infusion is completed, repeat orthostatic assessment should be performed to evaluate and document effectiveness.
References:
Halpern, JS (1987). Clinical notebook: Assessment of orthostatic hypotension. Journal of Emergency Nursing, 13 (3), 170-171.
Roper, M (1996). Back to basics; Assessing orthostatic vital signs. American Journal of Nursing, 96 (8), 43-46.
"Research Applied to Clinical Practice: Orthostatic
Measurement"
[http://ENW.org/Research-Orthostatic.htm]
is a webarticle by Robert C.
Knies, RN MSN CEN [bknies@stevenshealthcare.org]
©Robert C. Knies, RN MSN CEN
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