Chapter 7 – APPROACH TO THE PATIENT WITH ABNORMAL VITAL SIGNS

David L. Schriger

Care of the patient is guided by integration of the chief complaint, history, vital signs, and physical examination findings (Chapter 6). Physicians should be keenly aware of a patient's vital signs but should seldom make them the centerpiece of the evaluation.THE IMPORTANCE OF VITAL SIGNSThe importance of vital signs in medical care is a conundrum for proponents of an evidence-based approach to care of patients. No experienced physician would be willing to care for patients without them, yet a formal evaluation of the utility of vital signs for making specific diagnoses would conclude that they are not particularly useful because their likelihood ratios are too low to differentiate those who have a condition from those who do not (Chapter 6). For uncommon conditions, their predictive value is even worse. For example, the probability of tachycardia in a patient in thyroid storm is high, yet the probability of thyroid storm in a patient with isolated tachycardia is low. This application of Bayes' theorem (Chapter 9) demonstrates why there is no justification for ordering thyroid tests for every tachycardic patient and why attempts to say “When vital sign x is high [low], do y” fail. Each vital sign can be normal or abnormal in almost every acute condition (Table 7-1), and vital signs can be transiently abnormal in healthy individuals. An algorithmic approach to testing and treatment in response to abnormal vital signs would be too vague and too complex to be of use.

TABLE 7-1   -- NORMAL AND PANIC RANGES FOR KEY VITAL SIGNS IN ADULTS^[*]

	Normal	Panic
Temperature	36–38°C (96.8–100.4°F)	40°C (104°F)
Pulse	60 to 100 per minute	<45 per minute, >130 per minute
Respirations	12 to 20 per minute	<10 per minute, >26 per minute
Oxygen saturation	95–100%	<90%
Systolic blood	90–130 mm Hg pressure	<80 mm Hg, >200 mm Hg
Diastolic blood pressure	60–90 mm Hg	<55 mm Hg, >120 mm Hg

*

Normal values are for healthy adults. Values outside these ranges are common in patients who are ill or are anxious about their health care encounter. Panic values demand the health care provider's attention in any adult patient. These values are specific (rarely present in healthy patients) but not sensitive (most ill patients' vital signs will not include panic values). All vital signs must be interpreted in the context of the patient's presentation (see text).

Predictive ValueHow can it be that vital signs are poor predictors of diagnoses but central to the practice of medicine? First, although vital signs are insufficiently predictive to be of use in rigid algorithms, these algorithms are but one of several heuristics used by physicians to diagnose and to treat patients. Pattern recognition and the hypothetico-deductive model are heuristics that are based not on average tendencies of a single factor (e.g., hypotension is present in x% of cases of septic shock) or a small number of factors (hypotension and tachycardia are present in y% of cases of septic shock) but on the complex interaction of multiple factors (e.g., because this patient is an ill-appearing elderly man with an enlarged prostate and a history of urinary tract infections, is tachycardic and hypotensive, has clear lungs and an enlarged but nontender prostate, and has an oxygen saturation of 97%, he should be treated for urosepsis [Chapter 306] while awaiting results of urinalysis and urine culture). Thus, vital signs can play an important function in medical decision making even though their likelihood ratios are unimpressive.Vital Signs as SymptomsAbnormal vital signs are seldom the fundamental pathophysiologic problem. In shock (Chapter 107), hypotension and tachycardia are manifestations of pathophysiologic processes occurring at cellular and molecular levels. Given the circuitous links from clinical disease to fundamental pathophysiology to abnormal vital signs, it is not surprising that the relationships between the ends of the chain are not strong. Until new technologies enable direct measurement of primary pathologic processes, vital signs remain an important, albeit imperfect, proxy.The five key vital signs are temperature, pulse, blood pressure, respiratory rate, and oxygen saturation (pulse oximetry). Pulse oximetry is included because it has become widely available in acute care settings, is noninvasive and relatively inexpensive, and provides information unique from the respiratory rate. Advocates have suggested that pain, smoking status, and weight be considered routine vital signs; although a case can be made for each, they are not considered here. Clinicians should never forget that the most important vital sign is what the patient looks like; general appearance is a sign that guides the intensity and urgency of the evaluation.