1. 
   

   What symptoms and signs should be assessed in the initial evaluation of a patient with reported hypotension?

   
   
2. 
   

   What are the major categories of shock?

   
   
3. 
   

   What are the common iatrogenic complications that produce hypotension in the hospital?

According to the Agency for Healthcare Research and Quality (AHRQ), as many as 52,000 patients experience hypotension while hospitalized, leading to 162 deaths and an average of 3.7 additional hospital days in the United States annually. Hypotension may be the presenting reason for hospital admission or it may develop during hospitalization, sometimes as an iatrogenic complication. Because patients with hypotension may decompensate quickly, suffer irreversible end-organ damage, and ultimately die, clinicians should be able to recognize the clinical presentation of patients with life-threatening or reversible causes of hypotension and appropriately intervene.

Deviations from “normal” blood pressure must be considered in the context of the patient’s baseline blood pressure. A patient’s blood pressure normally varies depending on the time of day, even from minute-to-minute, and typically decreases during sleep. Arterial monitoring has shown that the systolic and diastolic blood pressure also varies with the respiratory cycle and with each heartbeat. Although hypotension typically refers to blood pressure lower than 90/60 mm Hg, some patients may be completely asymptomatic at such readings, whereas other patients may develop clinically important hypotensive symptoms at much higher readings. A patient with advanced cirrhosis, for example, may have a chronic stable systolic blood pressure of 85–90 mm Hg that requires no intervention, whereas a severely hypertensive patient may experience a stroke, myocardial infarction, or renal insufficiency from relative hypotension with “normal” blood pressure readings. Acute decreases in mean arterial pressure (typically more than 25%), such as after receiving an antihypertensive medication, put patients at greatest risk for such end-organ damage.

After quickly ensuring that the patient is alert and responsive and that ACLS does not need to be initiated, the first step is to determine whether the reported blood pressure reading is a valid measure of intraarterial blood pressure; this requires assessing the blood pressure manually. Many factors may affect the immediate accuracy of a blood pressure measurement, including the device used (cuff size, leaky bulb, faulty aneroid device), the technique or bias of the examiner (positioning of patient, placement of the cuff, inappropriately rapid deflation, excess bell pressure), and a noisy environment. Most errors overestimate the blood pressure, so a report of low blood pressure should alert the clinician to an impending emergency. In general, it is best to use the palpatory method first to avoid underinflation in patients with an auscultatory gap and overinflation in those with a very low blood pressure.

When assessing a hypotensive patient, the examiner should obtain a blood pressure reading by inflating the bladder to a pressure 20–30 mm Hg above the level previously determined by palpation with a manual device. Interobserver variation increases when arrhythmias such as atrial fibrillation cause a variable cardiac output from beat to beat; examiners should ignore premature beats as well as the subsequent beat because they do not represent mean arterial pressure.

After a low blood pressure is confirmed, the next step is to determine whether the blood pressure reading reflects an acute drop in central arterial pressure. In general during their first encounters with patients, physicians should personally record blood pressure measurements in both arms and, depending on the reason for admission and comorbidities, obtain orthostatic blood pressure readings. In an asymptomatic patient who has a history of vascular disease, a targeted vascular examination should be performed. Any hemodynamically significant vascular stenosis will result in a systolic difference of at least 10 or 15 mm Hg. To perform an optimal assessment and control for normal variation in blood pressure and other factors such as impaired baroreceptors, two examiners should measure the upper extremity blood pressure at the same time, and then change sides. If there is a discrepancy in blood pressure readings, the higher of the two readings reflects the central blood pressure, and subsequent blood pressures should be checked in the higher arm. Uncommonly, patients may have bilateral stenoses in both subclavian arteries, resulting in low blood pressure in both arms, but in this setting a low blood pressure reading would be unlikely to cause symptoms of decreased perfusion unless accompanied by vascular disease elsewhere. If upper extremity vascular disease is suspected as the etiology for inaccurate upper extremity blood pressure readings, large thigh cuffs can sometimes be used (with the patient reclined), but the patient’s body habitus and the presence of diffuse vascular disease may limit success (Table 91-1).

The next step is to determine whether the patient is experiencing any symptoms related to low blood pressure. If the patient is asymptomatic, the clinician has more time to review the previous days’ blood pressure measurements and hospital record with the goal to review and adjust any medications that may be contributing. Assuming a confirmed accurate low blood pressure reading, asymptomatic patients are more likely to be young and healthy, pregnant, or have systemic diseases such as severe hypothyroidism, chronic adrenal insufficiency, heart failure, cirrhosis, or vascular disease.