The first priority in the physical examination should be to assess the patient’s airway, breathing, circulation, and adequacy of mentation (eg, alertness, orientation, coherence of thought).
General appearance and vital signs vary according to the severity of the anaphylactic episode and the organ system(s) affected. Vital signs may be normal or significantly disordered with tachypnea, tachycardia, and/or hypotension.
Patients commonly are restless due to severe pruritus from urticaria. Anxiety, tremor, and a sensation of cold may result from compensatory endogenous catecholamine release. Anxiety is common unless hypotension or hypoxia causes obtundation. Frank cardiovascular collapse or respiratory arrest may occur in severe cases.
Respiratory findings
Severe angioedema of the tongue and lips (as may occur with the use of angiotensin-converting enzyme [ACE] inhibitors) may obstruct airflow. Laryngeal edema may manifest as stridor or severe air hunger. Loss of voice, hoarseness, and/or dysphonia may occur. Bronchospasm, airway edema, and mucus hypersecretion may manifest as wheezing. In the surgical setting, increased pressure of ventilation can be the only manifestation of bronchospasm. Complete airway obstruction is the most common cause of death in anaphylaxis.
Cardiovascular findings
Tachycardia is present in one fourth of patients, usually as a compensatory response to reduced intravascular volume or to stress from compensatory catecholamine release.
Bradycardia, in contrast, is more suggestive of a vasodepressor (vasovagal) reaction. Although tachycardia is the rule, bradycardia has also been observed in anaphylaxis (see Pathophysiology). Thus, bradycardia may not be as useful for distinguishing anaphylaxis from a vasodepressor reaction as was previously thought. Relative bradycardia (initial tachycardia followed by diminished heart rate despite worsening hypotension) has been reported previously in experimental settings of insect sting anaphylaxis, as well as in trauma patients.[6, 7, 57, 58, 59]
Hypotension (and resultant loss of consciousness) may be observed secondary to capillary leak, vasodilation, and hypoxic myocardial depression. Cardiovascular collapse and shock can occur immediately, without any other findings. This is an especially important consideration in the surgical setting. Because shock may develop without prominent skin manifestations or history of exposure, anaphylaxis is part of the differential diagnosis for patients who present with shock and no obvious cause.
Cognitive findings
If hypoperfusion or hypoxia occurs, it can cause altered mentation. The patient may exhibit a depressed level of consciousness or may be agitated and/or combative.
Cutaneous findings
The classic skin manifestation is urticaria (ie, hives). Urticaria can occur anywhere on the body, often localizing to the superficial dermal layers of the palms, soles, and inner thighs. Lesions are red and raised, and they sometimes have central blanching. Intense pruritus occurs with the lesions. Lesion borders are usually irregular and sizes vary markedly. Only a few small or large lesions may become confluent, forming giant urticaria. At times, the entire dermis is involved with diffuse erythema and edema.
In a local reaction, lesions occur near the site of a cutaneous exposure (eg, insect bite). The involved area is erythematous, edematous, and pruritic. If only a local skin reaction (as opposed to generalized urticaria) is present, systemic manifestations (eg, respiratory distress) are less likely. Local reactions, even if severe, are not predictive of systemic anaphylaxis on reexposure.
Angioedema (soft-tissue swelling) is also commonly observed. These lesions involve the deeper dermal layers of skin. It is usually nonpruritic and nonpitting. Common areas of involvement are the larynx, lips, eyelids, hands, feet, and genitalia.
Generalized (whole-body) erythema (or flushing) without urticaria or angioedema is also occasionally observed.
Cutaneous findings may be delayed or absent in rapidly progressive anaphylaxis.
Gastrointestinal findings
Vomiting, diarrhea, and abdominal distension are frequently observed.