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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3063_Библиотеки_им_академика_М_И_Перельмана
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Basic Science Correlate
Anaphylaxis is a classic type I hypersensitivity reaction, but know the other
hypersensitivity reactions and their associated clinical conditions and mechanisms.
Type I hypersensitivity
Anaphylactic and atopic
Free antigen cross-links IgE on mast cells and basophils and triggers immediate release of
histamine and bradykinin, which act on postcapillary venules; this leads to edema formation,
vasodilation, and bronchoconstriction
Delayed response follows, due to production of leukotrienes from arachidonic acid
Examples:
Allergic and atopic (rhinitis, asthma, hay fever, hives, eczema)—
Patients with IgA-deficiency can have severe anaphylactic reaction to blood products
(dyspnea, bronchospasm, hypotension, respiratory failure, shock); administer washed
RBCs
—
Type II hypersensitivity
Cytotoxic (antibody mediated) IgM, IgG bind to fixed antigen on cell leading to cellular
destruction
Opsonization leading to phagocytosis—
Complement-mediated lysis—
Antibody-dependent cell-mediated cytotoxicity usually due to NK cells or macrophages—
Examples:
Autoimmune hemolytic anemia—
Pernicious anemia—
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Final Diagnosis
Anaphylaxis, secondary to nuts
Rheumatic fever
—
Goodpasture’s syndrome
—
Bullous pemphigoid
—
Idiopathic thrombocytopenic purpura
—
Type III hypersensitivity
Immune complex mediated
Complexes activate complement, which attracts neutrophils; neutrophils release lysosomal
enzymes
Examples:
SLE
—
Polyarteritis nodosa
—
Post-streptococcal glomerulonephritis
—
Serum sickness
—
Arthus reaction (e.g., swelling and inflammation following a vaccination)
—
Type IV hypersensitivity
Delayed (T-cell mediated)
Sensitized T lymphocytes encounter antigen and then release lymphokines, leading to
macrophage activation
Only hypersensitivity type that does not involve antibodies
Examples:
Multiple sclerosis
—
Guillain-Barré syndrome
—
Graft-vs-host disease
—
PPD
—
Contact dermatitis
—
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Case 7
Chief Complaint
Extensive body burns
History and Physical Examination
A man is trapped in a house fire for 20 minutes. When he is finally rescued, he is noted to
be alert and breathing. He suffers extensive burns on his right arm and anterior chest, and
is brought by ambulance to the emergency department.
He is currently awake and alert with a patent airway and moving air without difficulty.
There is some soot around his mouth, and he is not hoarse. Vital signs are stable. There
are extensive second- and third-degree burns along the entire right arm and anterior torso,
with some scattered first-degree burns over both lower extremities and back. He weighs
220 lbs. Heart and lung examinations are normal except for tachycardia; there is no
wheezing. His abdomen is soft and nontender.
Differential Diagnosis
Initial Management
Setting: emergency department
Skin burns
1.
Airway burn
2.
Carbon monoxide poisoning
3.
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Diagnostic/Therapeutic Plan
Test Results
CLINICAL PEARL
The most common cause of death in burns is carbon monoxide poisoning. That makes
100% oxygen administration the most important initial therapy for burns.
Assessment
Diagnosing skin burns in this case is not difficult; the challenge is to determine the exact extent
of the burns. Burn depths are graded as first-, second-, and third-degree.
Carboxyhemoglobin level
Chest x-ray
CBC
Electrolytes (chemistry)
Carboxyhemoglobin elevated at 23%
Chest x-ray: normal
Hemoglobin 14 g/dL
Electrolytes: normal
First-degree burns are erythematous, and only the superficial layer of skin is affected.
Second-degree burns are often associated with blistering and a white or fibrinous exudate.
Third-degree burns may appear blackened, charred, or leathery. Patients often lack
sensation in these areas because of loss of both epidermal and dermal elements, including
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Evidence of respiratory tract injury includes tachypnea, soot in the mouth, erythema of the
palate, stridor, laryngospasm, and other evidence of respiratory distress. Laryngeal edema and
respiratory failure can develop 6–24 hrs after the injury. The airway and lung may appear
normal at first, but life-threatening abnormalities may appear later.
Further Management Plan/Results
CCS NOTE
Order a bolus of fluids with the initial set of labs in serious burns; you can only specify
“bolus” or “continuous,” not the specific amounts.
Further Management Plan
hair follicles and pain receptors.
The most common causes of death in the initial period following second- and third-degree
burns are hypovolemic shock, infection, and airway injury.
Airway injury is a variable problem, depending on the nature of the burn. Even without a
direct burn of the airway, inhalation injury can lead to serious illness because of the
elevation of carboxyhemoglobin levels. Carboxyhemoglobin does not deliver oxygen to
tissues, and functionally, it is the same as being anemic.
—
Immediate bronchoscopy: reveals no significant airway injury
100% oxygen
1.
Fluid resuscitation 4 mL/kg/% BSA burned (Ringer’s lactate)
2.
Prevention of infection with topical antibiotics
3.
Endotracheal intubation if there is evidence of significant respiratory injury
4.
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CCS NOTE
In burn cases with evidence of respiratory burn (e.g., hoarseness, wheezing, stridor,
burns in the mouth), perform endotracheal intubation with the first set of orders.
Discussion
Care in the acute period should focus on maintaining adequate ventilation and oxygenation,
replacement of acute volume loss, correcting metabolic abnormalities, and prevention of
infectious complications. The decision to use intubation is based on the degree of airway
inflammation and level of oxygenation. The patient should be started on 100% supplemental
oxygen, as oxygen therapy decreases the half-life of the carboxyhemoglobin. The full extent of
an inhalation injury may not be apparent for 12–24 hrs.
Hypovolemic shock often results from second- or third-degree burns encompassing >25% of
the BSA.
CCS NOTE
Fluid is infused at 2–4 mL per kg per %
Fluids are given in first 24 hrs; normal saline or Ringer’s lactate is acceptable
Patients may require replacement of plasma and albumin as well
Emphasis should be placed on maintaining adequate urine output to avoid renal failure
Hypovolemia can result in metabolic acidosis
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The CCS asks route of administration, not dose. Hence, in burns, topical antibiotics,
not systemic or IV antibiotics, are used prophylactically.
If the patient is not tolerating PO intake, control the pain with IV morphine drip or PCA pump;
if the patient is tolerating it, use extended-release morphine or methadone.
Calculations for BSA are as follows:
Silver sulfadiazine is administered topically to all burned areas, and the wounds should be
débrided and dressings changed 2x daily. Operative debridement of deep partial-thickness
burns and skin grafting should be done as soon as feasible. This helps to avoid subeschar
infection and improves wound closure. Streptococcal and staphylococcal infection often
complicates the initial course.
Excision of burn eschar may be done to improve healing or if evidence of arterial compression
is present. Patients may require skin grafting.
Final Diagnosis
Burns
Head 9%
Arms 9% each
Legs 18% each
Chest 18%
Back 18%
Perineum 1%
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269
Case 8
Chief Complaint
“I have a weird feeling in my chest.”
History and Physical Examination
A 66-year-old man comes to the emergency department complaining of a several-day
history of an intermittent sensation of fluttering in his chest. He feels weak when the
episodes occur, but denies chest pain or shortness of breath. He presents today because
the symptoms are now constant. He has had hypertension for 20 years, which is well-
controlled with enalapril, and he takes albuterol for asthma. He denies any alcohol use.
Vital signs are temperature 36.8° C (98.3° F), blood pressure 140/80 mm Hg, pulse
140/min, and respirations 12/min. Physical examination shows a supple neck and no
jugular venous distention or thyromegaly. Cardiovascular exam shows an irregularly
irregular rhythm with no rubs or gallops. The chest is clear, the abdomen is benign, and
there is no edema in his extremities.
Differential Diagnosis
Atrial fibrillation
1.
Multifocal atrial tachycardia
2.
Supraventricular tachycardia
3.
Cardiomyopathy
4.
Pulmonary embolism
5.
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