7-10
Chapter 30: Shock
Shock: Anaphylactic
COL Clifford Cloonan, MC, USAIntroduction:
Anaphylaxis is an acute, generalized allergic reaction affecting the cardiovascular, respiratory, cutaneous, and
gastrointestinal systems. This is a severe immune-mediated reaction that occurs when a previously sensitized
patient is again exposed to an allergen. Common causes: bee/wasp stings, penicillin or other drug allergies
(esp. when given IM/SC/IV), seafood (esp. shrimp/shellfish) and nuts of various types. Allergens may produce
an allergic reaction by being ingested, inhaled, injected, or absorbed through the skin/mucous membranes.
Shock is produced by the release of histamine that causes bronchospasm/wheezing. Histamine also causes
“leaky” vessels resulting in hives/edema and hypotension. This produces both a volume problem and a
vascular resistance problem. Anaphylactic shock differs from less severe allergic reactions in that it is
characterized by hypotension and obstructed airflow (upper and/or lower) that can be life-threatening. History
of allergies is a risk factor.
Subjective: Symptoms
General malaise/weakness, lightheadedness, anxiety/feeling of impending doom diffuse itching/”scratchy”
sensation in the back of the throat, chest tightness/difficulty breathing. If allergen was ingested, there may
be associated nausea/vomiting and diarrhea.
Objective: Signs
Using Basic Tools: Vital Signs: Pulse: tachycardia; B/P: hypotension and orthostatic hypotension; +/-
narrowing pulse pressure (systolic-diastolic pressure); Respirations: tachypnea/hyperpnea
NOTE: Children and physically fit young adults may maintain near normal vital signs until significant shock
is present and death is imminent
Inspection: Anxious appearance with increased respiratory rate +/- audible stridor, +/- altered mental
status, flushed/red skin with hives (urticaria), and edema (esp., periorbital/perioral). Nasal mucosa may
be congested, swollen and inflamed. Profuse watery rhinorrhea, itchy eyes, followed by wheezing are
characteristic. Generalized itching with hives (pruritus and urticaria), and occasionally angioedema of the
face (swelling of the eyelids, lips, cheeks) Capillary refill: Delayed in shock, longer than 3 seconds.
Auscultation: Inspiratory and expiratory wheezing (bronchospasm)
Palpation: Warm skin (until severe hypotension develops at which point skin becomes cool/moist)
GI: Bowel edema, causing cramps and water diarrhea.
Using Advanced Tools: Pulse oximetry
Assessment:
Differential Diagnosis
Allergic reaction without hypotension and/or airway obstruction
Vasovagal reaction after injection/immunization (common)
Cardiogenic shock
Angioedema
Plan:
Diagnostic Tests
Essential: Clinical observation is the only diagnostic test. Use the rapidity and constellation of symptoms to
suggest the diagnosis. A prior history of similar symptoms may be the only other clue.
Close observation with frequent assessment/reassessment of mental status, vital signs, and pulse oximetry
Recommended: Continuously monitor urinary output. If patient is intubated and ventilations are being
supported, frequently reassess the pressures needed to ventilate.
Procedures
Essential: Reduce/eliminate all further exposure to allergen. If due to an injected drug or venom, apply