cardiovascular disorders
Orthostatic Hypotension
Evaluation of Orthostatic Hypotension
Orthostatic hypotension is diagnosed when systolic BP drops by ≥ 20 mm Hg or diastolic BP drops by ≥ 10 mm Hg within 3 minutes of standing. Once orthostatic hypotension is diagnosed, a cause must be sought. History of present illnessshould identify the duration and severity (eg, whether associated with syncope or falls) of symptoms. The patient is asked about known triggers (eg, drugs, bed rest, fluid loss) and the relationship of symptoms to meals. seeks symptoms of causative disorders, particularly symptoms of autonomic insufficiency such as visual impairment (due to mydriasis and loss of accommodation), incontinence or urinary retention, constipation, heat intolerance (due to impaired sweating), and erectile dysfunction. Other important symptoms include tremor, rigidity, and difficulty walking ( Parkinson Disease , should identify known potential causes, including diabetes, Parkinson disease, and cancer (ie, causing a paraneoplastic syndrome). The drug profile should be reviewed for offending prescription drugs (see table Causes of Orthostatic Hypotension ), particularly antihypertensives and nitrates. A family history of orthostatic symptoms suggests possible familial dysautonomia. BP and heart rate are measured after 5 minutes supine and at 1 and 3 minutes after standing; patients unable to stand may be assessed while sitting upright. Hypotension without a compensatory increase in heart rate (<10 beats/minute) suggests autonomic impairment. Marked increase (to>100 beats/minute or by>30 beats/minute) suggests hypovolemia or, if symptoms develop without hypotension, POTS. The skin and mucosae are inspected for signs of dehydration and for pigment changes suggestive of Addison Disease (eg, hyperpigmented areas, vitiligo). The extent of physical examination is guided by clinical suspicion. A rectal examination is done to evaluate for gastrointestinal bleeding. A detailed neurologic examination should include evaluation for peripheral neuropathy (eg, abnormalities of strength, sensation, and deep tendon reflexes). Certain findings suggest a more serious etiology: Bloody or heme-positive stool Abnormal neurologic examination In patients with acute symptoms, the most common causes—drugs, bed rest, and volume depletion—are often apparent clinically. In patients with chronic symptoms, an important goal is to detect any neurologic disorder causing autonomic dysfunction. Patients with movement abnormalities may have Parkinson Disease or ECG, serum electrolytes, creatinine, and glucose are routinely checked. However, these and other tests are usually of little benefit unless suggested by specific symptoms. The dose of a suspected drug may be reduced or the drug stopped to confirm the drug as the cause. Tilt Table Testing None Patients with autonomic symptoms or signs require further evaluation for Diagnosis , Autonomic function can also be evaluated with bedside cardiac monitoring, although this test is not often done. When the autonomic system is intact, heart rate increases in response to inspiration. The heart is monitored as the patient breathes slowly and deeply (about a 5-second inspiration and a 7-second expiration) for 1 minute. The longest inter-beat (R-R) interval during expiration is normally at least 1.15 times the minimum R-R interval during inspiration; a shorter interval suggests autonomic dysfunction, but this response to inspiration may decrease with aging. A similar variation in R-R interval should exist between rest and a 10- to 15-second Valsalva maneuver. 