Orthostatic hypertension, also known as postal hypertension is a medical condition consisting of an abrupt and sudden rise in blood pressure when a person stands up or upon assumption of upright posture. In orthostatic hypertension, there is an increase in Blood pressure of 20 mm Hg upon standing in an upright posture.
Explaining orthostatic hypertension by an increase in diastolic blood pressure is less reliable than systolic blood pressure. In diastolic orthostatic hypertension usually BP rise by 5 to 10 mmHg upon upright posture or standing up because of peripheral vasoconstriction and decrease in cardiac stroke volume.
Orthostatic hypertension is also linked with morning blood pressure surge and intense nocturnal blood pressure dipping both of which are responsible to increase pulsatile hemodynamic stress of central arterial pressure and blood flow in patients with the systemic hemodynamic atherothrombotic syndrome
An abnormality in the cardiovascular autonomic mechanism triggers orthostatic hypertension. In healthy individuals, blood pressure decreases upon standing due to blood being pooled in capacitance vessels below the diaphragm.
Also, 10% to 20% of plasma volume from the intravascular compartment is forced by hydrostatic pressure in the interstitial spaces within 15 to 20 minutes of standing. In presence of such a mechanism, an increase in blood pressure is medically too shocking and unexpected.
Studies suggest that orthostatic hypertension is most likely to occur due to the following pathophysiological phenomenon
- Due to increased vascular resistance
- Due to the increase in blood viscosity and its contributions to vascular resistance
- Excessive plasma shifts
- Excess venous pooling
- Reduction in cardiac preload
Orthostatic hypertension relates to essential hypertension
Recently clinical studies observe the relation of orthostatic hypertension with essential hypertension by choosing two groups. One is elderly patients with essential hypertension plus orthostatic hypertension.
Another group is hypertensive patients with orthostatic hypertension who show abnormal diurnal variation in blood pressure. Results reveal the following results
- The risk of silent cerebrovascular infarct was high in patients with orthostatic hypertension than in hypertensive individuals without orthostatic hypertension.
- Orthostatic hypertensive patients have an increased prevalence of CNS lesions detectable by MRI
- Orthostatic hypertension may be associated with measurable neurocognitive deficits and cerebrovascular infarction independent of essential hypertension.
How Orthostatic hypertension is linked with other disorders
Orthostatic hypertension is directly or indirectly related to other medical disorders mentioned as follows
- Essential hypertension
- Type 2 diabetes
- Anorexia nervosa
- Renal arterial stenosis
- Vascular adrenergic hypersensitivity
- Postural orthostatic tachycardia
- Other types of dysautonomia
Its pathophysiology and the exact cause are still unknown. Research and studies are in the process to explain and define its mechanism of occurrence and etiology in a more definite and authentic way with enough clinical and statistical evidence.
Orthostatic hypertension symptoms
There is no sign and symptoms in mild or moderate orthostatic hypertension. However severe orthostatic hypertension may exhibit typical symptoms of hypertension.
According to clinical findings the most common, orthostatic hypertension symptom associated with diastolic orthostatic hypertension is orthostatic venous pooling. It occurs in legs upon upright posture.
Diagnosis of this undefined medical disorder is fortunately straightforward, i.e to measure the blood pressure of the patient in the supine and upright position and evaluating the difference between these two values gives an idea about the presence or absence of orthostatic hypertension.
However standardized value for the increase in systolic blood pressure and diastolic blood pressure is lacking in terms of diagnostic criteria.
Usually, an increase in 20 mm Hg of BP in an upright position is considered as an indication of orthostatic hypertension.
Readings should be taken more than one time to check the reproducibility of results as patients with essential hypertension show more variable BP readings as compared to healthy normotensive patients.
Currently, there is no official treatment for orthostatic hypertension. Treatment for this disorder still follows a trial and error experiment strategy. However, some medications that have been successfully used for its treatments are
- Propranolol hydrochloride
In severe cases, specialists go for the infusion of normal saline through IV for hypovolemia to bring the blood pressure and volume to safe levels. Blood pooling issues along with this disorder can be managed by pressure garments over the pelvis and lower extremities.
Patients having other underlying conditions such as essential hypertension or diabetes Mellitus type two should be treated accordingly.
How to measure orthostatic blood pressure
Orthostatic blood pressure can be determined by observing the difference in blood pressure while sitting and in an upright posture. It is relatively simple and consists of the following steps
- Ask the patient to lie down for 5 minutes
- Measure blood pressure and blood rate
- Ask the patient to stand in an upright position
- Again measure blood pressure and pulse rate after 1 to 3 minutes of standing.
Change in blood pressure greater than 20 mmHg or greater than 10 mmHg in diastolic blood pressure is considered abnormal.
Here are a few medical conditions where orthostatic hypertension is a notable feature.
Chronic primary conditions
Essential hypertension in the elderly
■ Essential hypertension with abnormal diurnal variation (‘extreme dippers’)
Type 2 diabetes mellitus
- Postural tachycardia syndrome with a disorder of mast-cell activation
- Norepinephrine transporter deficiency
- Baroreflex failure (acute)
Potentially surgically-correctable conditions
- Medullary vascular compression
- In orthostatic hypertension, there is an increase in Blood pressure of 20 mm Hg upon standing in an upright posture.
- Its diagnostic criteria and treatment is still under study
- Orthostatic hypertension involves a hyperactive response to orthostatic stress that increases the risk for CVS disease or organ damage.
- Orthostatic hypertension is considered to a form of prehypertension and an alarming sign of mask hypertension in individuals with normal supine blood pressure.
- OTH leads to hemodynamic atherothrombotic syndrome by increasing pulsatile hemodynamic stress of central arterial pressure and blood flow.
- Studies reveal that alpha-adrenergic vascular disease is a potential cause of OTH.
- Further studies are required to understand more about the complications and risk factors of orthostatic hypertension disease.
Orthostatic hypertension is a definite clinical phenomenon linked with a variety of underlying conditions. At present, its pathophysiology is poorly understood with undefining orthostatic hypertension symptoms but seems to involve the activation of the sympathetic nervous system.
A better understanding of its pathophysiology will be more helpful in its management and treatment. This illness has still many undefined questions that required focused basic science and clinical inquiry.