Orthostatic vital signs

Vital signs include body temperature, heart rate (pulse), breathing rate, and blood pressure. As you age, your vital signs may change, depending on how healthy you are. Some medical problems can cause changes in one or more vital signs. Checking your vital signs helps your health care provider monitor your health and any medical problems you may have.

Orthostatic vital signs also known as postural, vital signs, are a series of vital signs of a patient taken while the patient is supine, then again while standing. The results are only meaningful if performed in the correct order (starting with supine position) ¹. Orthostatic vital signs are used to identify orthostatic hypotension ². Orthostatic vital signs are used to evaluate the body’s response to position changes when volume loss is suspected ³. Orthostatic vital signs should be considered for patients with suspected blood, fluid loss or dehydration. The most common variables measured to assess orthostatic vital signs in potentially hypovolemic patients include blood pressure and heart rate, measured with the patient in different positions (supine, sitting, standing). Orthostatic vital signs are defined as a change in blood pressure, heart rate, or onset of symptoms after a change in position in individuals (adult, child, and adolescent) with a decrease in intravascular volume ⁴.

Under normal conditions blood pooling in the lower extremities during position change is directed back to the upper body through the vasoconstriction of blood vessels ⁵. This vasoconstriction is accomplished through unloading of the arterial baroreceptors to enhance sympathetic outflow, which increases systemic vascular resistance, venous return and cardiac output ⁶. Baroreceptors are mechanoreceptor sensory neurons that are excited by stretching of the corresponding blood vessel. The most important arterial baroreceptors are the carotid sinus baroreceptors, and the aortic arch baroreceptors ⁷. However, conditions leading to hypovolemia and autonomic failure may result in a sudden drop in blood pressure known as orthostatic hypotension and result in impaired perfusion to the upper body. The American Autonomic Society and the American Academy of Neurology define orthostatic hypotension as a decrease in systolic blood pressure of 20 mm Hg or a decrease in diastolic blood pressure of 10 mm Hg within three minutes of standing compared with blood pressure from the sitting or supine position ⁸. This drop in blood pressure may be associated with symptoms such as lightheadedness, dizziness, blurred vision, weakness, fatigue, cognitive impairment, nausea, palpitations, tremulousness, headache, neck ache and syncope ⁹.

The most common reason for performing orthostatic vital signs in the emergency department (ED) is to evaluate fluid volume status. However, research has shown orthostatic vitals are not reliably sensitive to volume losses less than 1000-mL in adult patients ¹⁰. Studies have also revealed wide variations in response to the orthostatic challenge among normal adult individuals ¹¹. To add to the confusion, the procedure for measurement of orthostatic vital signs is not standardized as evidenced by a review of the literature reflecting significant variations in practice. The duration of position change differs between research studies as do the position changes (lying to standing, lying to sitting to standing). There is even some debate as to which findings are the most important indicators of orthostatic hypotension and what the cut-points are for vital signs changes.

An increase in heart rate is often noted when there is a change in posture. This compensatory change occurs in response to the sudden drop in blood pressure ¹². While heart rate is not included in the official definition for orthostatic hypotension per the American Academy of Neurology, changes in heart rate aid the differential diagnosis for orthostatic hypotension. For instance, a drop in blood pressure accompanied by a rise in heart rate indicates volume depletion, while no change in heart rate may point to a neurogenic cause ¹². Knopp, Claypool, and Leonardi ¹³ found that in adults a heart rate increase of 30 beats per minute or more is considered indicative of volume loss.

The definition of orthostatic vital signs warrants further research despite its common use in clinical practice, textbooks, guidelines and research studies ³. A review of definitions from the literature indicates that the assessment parameter labeled as orthostatic vital signs can be summarized by its: physiological variables, measurement method, and purpose. The physiological variables include blood pressure, heart rate, and stroke index ⁴, as well as symptoms of dizziness or lightheadedness ¹⁴. Stated purposes of orthostatic vital signs assessment include identification of hypovolemia (both dehydration and blood loss) and treatment efficacy of pharmacological agents for neurological conditions.

Body positioning and timing

Supine

The period of rest prior to the supine measurement is variously identified as one minute ¹⁵, two minutes ¹⁶, three minutes ⁹, or five minutes ¹⁷. Harkel and colleagues ¹⁸ discovered that the period of rest did impact the changes in blood pressure and heart rate with more pronounced changes identified following a longer period of rest. They measured vital signs following one minute, five minutes and 20 minutes of rest and found that “the augmentation of the BP and HR response is small when the period of rest is increased from five to 20 minutes, it seems adequate to perform this test after at least five minutes of supine rest” ¹⁸. However, Lance et al. ¹⁴ found that 10 minutes of rest was required for accurate measurement of orthostatic vital signs. It should be noted that both studies by Harkel et al. ¹⁸ and Lance et al. ¹⁴ were conducted on small samples of 10 and 34 (respectively) of young, healthy, normotensive subjects. In addition, different methods of recording vital signs were used by the researchers: Harkel et al. ¹⁸ used the Ohmeda 2300 Finapres continuous, non-invasive finger blood pressure device, and heart rate
was measured via electrocardiogram; Lance et al. ¹⁴ used the Johnson and Johnson Critikon DINAMAP model 1846 SX to measure blood pressure and heart rate in the upper arm.

The American Heart Association recommends blood pressure measurements to be made in the upper arm with 5 minutes of rest time prior to the first blood pressure measurement ¹⁹. Furthermore, the subject should refrain from talking and the legs should be “uncrossed, and the back and arm supported” ¹⁹. Crossing the legs elevates the systolic blood pressure while an unsupported back raises the diastolic blood pressure ¹⁹. Failure to support the arm will also impact blood pressure readings: readings taken above the level of the heart are artificially low while those taken below heart level are artificially high ¹⁹.

Sitting

The definition of orthostatic hypotension provided by the American Autonomic Society and the American Academy of Neurology only considers blood pressure changes from the supine to the standing, not the sitting, position. Measuring vitals in the sitting position can actually lessen the orthostatic effect of standing ²⁰. Cooke and colleagues ⁹ found that, in adults on a syncope unit (n=730), the sit-stand test had low diagnostic accuracy. In a review of the literature, Winslow, Lane, and Woods ²¹ reported less dramatic changes in systolic blood pressure when the sitting position is included but this finding was not statistically significant. However, it may be unsafe to move from the lying position directly to standing, especially in patients with large volume losses ²². Kennedy and Crawford (1984) recommended measuring vitals in the sitting position first and, if no change occurs, measuring in the standing position to avoid falls in orthostatic individuals.

Standing

Empirical evidence reveals inconsistencies in the process of measuring vital signs after standing. orthostatic hypotension can be detected within two minutes of standing in most cases ²³. Cohen and colleagues ¹⁷ found that 83.5% of orthostatic hypotension
could be detected within three minutes of standing. Knopp and colleagues ²⁴ determined that measurements taken one minute after standing demonstrated the greatest change in pulse rate between no blood loss and 1000 ml blood loss. However, the detection of orthostatic hypotension is enhanced by the measurement of vital signs at multiple points per position ²³. This is especially true in cases where orthostatic hypotension is delayed.

Delayed orthostatic hypotension occurs within 10 to 30 minutes of standing ²⁵ classical orthostatic hypotension occurs with three minutes ²⁶. Delayed orthostatic hypotension may occur more frequently in the elderly, with vasoactive and diuretic drug use, and co-morbidities ²⁶. In mildly symptomatic individuals who have normal orthostatic vital signs within two minutes of standing, it is recommended that additional vital signs be taken to rule out delayed orthostatic hypotension.

Sensitivity to fluid loss

Researchers have shown that orthostatic vitals are not reliably sensitive to volume losses less than 1000 ml in adult patients ¹⁵. Barraf and Schriger ¹⁵ determined that pulse rate was the most sensitive vital sign in detecting a 450 ml blood loss (9% sensitivity for a pulse rate increase of 20 or higher). Knopp et al. ¹³ had similar findings comparing two groups: Group 1 with a 450 ml blood loss and Group 2 with a 1000 ml blood loss in 500 ml increments. Pulse change (supine to standing) at one minute had the greatest change between no blood loss and 1000 ml blood loss. Blood pressure change did not distinguish patients with no blood loss; patients with 500 ml blood loss; or patients with 1000 ml blood loss ¹³.

Levitt et al. ¹¹ evaluated the degree of volume loss and orthostatic vital sign changes in emergency department (ED) patients. They found wide variation in orthostatic vital sign changes for healthy and ill individuals and poor correlation of vital signs and level of dehydration ¹¹. Heart rate and age had a small correlation with level of dehydration. While systolic blood pressure did not demonstrate a statistically significant association with the degree of dehydration, systolic blood pressure was the only vital sign to distinguish between patients with blood loss and healthy volunteers. Patients with blood loss had a mean systolic blood pressure change of -10.7 mmHg (± 13.7 mmHg).

Blood pressure

Blood pressure and heart rate were the most frequent physiological variables measured during orthostatic vital sign assessment. Generally, orthostatic hypotension in an adult can be described as a drop in blood pressure and an increase in heart rate associated with position change. Several studies reported blood pressure changes following position changes. In a convenience sample of 814
adult emergency department patients suspected to be hypovolemic, Cohen and colleagues ¹⁷ found that, of those with diagnosed orthostatic hypotension, 83.5% could
be detected at one and three minutes after standing. Similarly, a decline in systolic blood pressure of 20 mmHg or more in 31% of the patients (n =69) and decline in diastolic blood pressure of 10 mmHg or more in 14% of the patients (n = 31) within 10 minutes of standing were reported by Atkins et al. ²³.

It is important that the patient rest prior to the first blood pressure measurement. Physical activity immediately preceding orthostatic vital signs can influence the results. Generally, 5-10 minutes is thought to be a sufficient period of time. The important thing to remember is that patients should not have their orthostatic vital signs measured immediately after physical exertion.

In a contrasting population, different blood pressure changes were found in a convenience sample of 100 normovolemic adolescent patients, ages 12 to 19 years, in a study by Horam and Roscelli ²⁷. The mean systolic blood pressure change ranged from a 17 mmHg decrease to a 19 mmHg increase, and diastolic blood pressure change ranged from a 7 mmHg decrease to a 24 mmHg increase. In other words, systolic and diastolic blood pressure tended to increase rather than decrease upon position changes in many adolescents. These findings suggest the physiological response to position changes yields a different blood pressure response in adolescents compared to hypovolemic adults. Compensatory mechanisms that may influence the blood pressure response in adolescents include: baroreceptor activity, arteriolar vasoconstriction, capillary hydrostatic forces, renin aldosterone stimulation and antidiuretic hormone release ²⁷. Given the wide variability of orthostatic vital signs in the adolescent population, further research is warranted.

Orthostatic vital signs were compared between normally-hydrated and volume-depleted children aged 4-15 in a 1987 study by ²⁸. Volume status was determined using an adaptation of the method discussed by Winters and Finberg ²⁹ which evaluates mucous membranes, eyes, skin color, urine output and urine specific gravity. Mean changes in systolic blood pressure were small and non-significant (-0.38 ±8 mmHg) for both groups of children ²⁸.

Heart rate

Heart rate was the second most frequent variable used during orthostatic vital sign assessment. Five of the 12 research studies used heart rate as a measurement variable. Heart rate showed significant changes in two studies of healthy blood donors ⁴. Barraf and colleagues conducted a study to determine the effect of age on orthostatic vital signs, whereas early detection of acute blood loss was the purpose of the study by Durukan et al. ⁴. The heart rate variable by itself showed a sensitivity of 9% and a specificity of 98% with an increase in heart rate greater than 20 beats per minute in the Barraf et al. study ¹⁰. Also, an increase in heart rate greater than 20 beats per minute, plus a drop in diastolic blood pressure more than 10 mmHg, increased the sensitivity to 17% while maintaining a specificity of 98%. Levitt, Lopez, Liberman, and Sutton ¹¹ reported a weak, non-significant change in heart rate, in 202 dehydrated or acutely bleeding adults compared to 21 healthy individuals. Heart rate changes for the healthy individuals were 11.26 ± 11.3 bpm, whereas the ill adults had heart rate changes of 13.63 ± 10.3 bpm ¹¹.

The study by Fuchs and Jaffe ³⁰ investigated orthostatic vital sign changes in children. Like adults, children typically respond to a decrease in intravascular volume with an increase in heart rate. This study involved two groups of children between the ages of four and 15 years old who were seen in an emergency department. Group 1 consisted of 16 children meeting the dehydration criteria, compared to 21 children evaluated as normal. The mean orthostatic rise in heart rate was significantly different between groups: 29.1 bpm (± 10.7) in the dehydrated group versus 13.1 bpm (± 8.5) in the normovolemic group. Further research of hypovolemic children is warranted to learn how the heart rate increase compares with the adult population.

Syncope symptoms and shock index

In addition to blood pressure and heart rate, syncope symptoms and shock index are two other variables reported in the literature related to orthostatic hypotension. Adults, 16 years and older, presenting with complaints of syncope to an emergency department were studied to learn the relationship between syncope symptoms and orthostatic vital signs ³¹. Syncope was defined as a “sudden, transient loss of consciousness associated with an inability to maintain postural tone that was not compatible with a seizure disorder, vertigo, dizziness, coma, shock, or other states of altered consciousness” ³¹. A significant number, 31% (n=69/223) of patients with syncope as the chief complaint demonstrated a reduction in systolic blood pressure of 20 mmHg or more upon standing (n=34). Syncopal patients with and without orthostatic hypotension were reported to be similar in age, medications, baseline blood pressure, and timing of blood pressure changes (one, two, three, five and 10 minutes after standing). Similar findings regarding syncopal symptoms were reported in a study by Gehrking et al ³². Episodes referred to as presyncope, were reported in 67% of the patients (n = 24) after a 70 degree head up tilt ³². Presyncope was defined by the patient’s indication of feeling faint or the observer’s visual judgment of the patient. The study measured vital signs at one, two, three, and five minute intervals. The presyncopal symptoms occurred after the three minute but before the five minute interval.

Durukan and colleagues ⁴ added shock index (heart rate divided by systolic blood pressure) along with blood pressure and heart rate to detect hemodynamic changes after acute blood loss. The researchers reported significant changes in systolic blood pressure and shock index. Five minutes after blood donation, while remaining in a semi-supine position, systolic blood pressure (108 ± 12mmHg), and shock index (0.76 ± 0.15) were significantly different from pre-donation (systolic blood pressure 120 ± 20 mmHg; shock index 0.66 ± 0.15). While they only tested vital signs while participants remained in a semi-supine position, change in shock-index with position change might be investigated as an indicator of volume status in future research. The time to calculate shock index could be a limitation in an emergency setting unless a calculator is readily available.

Description of decision options and interventions

1. Adults (age 17 years and older. The correct procedure for measuring blood pressure while the patient is seated or standing is to measure the blood pressure in the upper arm while supporting the patient’s arm and back. The legs should be uncrossed.
   1. The individual should rest in a flat, supine position 5-10 minutes prior to the first blood pressure measurement.
   2. Blood pressure measurements should be taken at one and three minutes after standing.
   3. Position change from supine to standing has better diagnostic accuracy in volume depleted adults compared to position changes from supine to sitting and then to standing.
   4. Orthostatic vital signs alone lack the sensitivity to reliably detect volume losses less than 1,000 ml.
   5. Symptoms such as dizziness and syncope, in combination with orthostatic vital signs, are more sensitive indicators of volume loss that vital sign changes alone. Therefore, symptoms and vital signs should be documented as the orthostatic variables.
   6. When measuring orthostatic vital signs, one or more of the following findings may indicate intravascular volume loss in adult patients:
      • a. Decrease in systolic blood pressure of 20 mmHg or more
      • b. Decrease in diastolic blood pressure of 10 mmHg or more
      • c. Increase in heart rate of 20 or greater beats per minute
2. Pediatric and Adolescent (less than 17 years)
   • There is insufficient evidence in the literature to make recommendations regarding orthostatic vital signs in the pediatric or adolescent population with fluid volume alterations.

References

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