Rosen & Barkin's 5-Minute Emergency Medicine Consult (53 page)

• Patients with allergic reactions should have a follow-up within 48 hr of discharge to evaluate effectiveness of outpatient therapy.
  
• Refer patients who are treated and released from the ED after an episode of anaphylaxis, angioedema, or urticaria to an allergist for follow-up skin testing and consideration for desensitization.
  
• Patients should be advised to carry some type of treatment that can be self-administered in the event of future reactions such as the prefilled syringe EpiPen.
  
• Patients with a known trigger should be counseled on strict avoidance of that trigger.
  

• Failure to consider anaphylaxis early in presentation can lead to devastating hemodynamic compromise and airway collapse.
  
• Epinephrine given early is the most important intervention.
  
• Patients with a history of anaphylaxis should be educated about trigger avoidance and instructed in the correct use of epinephrine auto-injector pens.
  

• Barach EM, Nowak RM, Lee TG, et al. Epinephrine for the treatment of anaphylactic shock.
  JAMA
  . 1984;251:2118–2122.
  
• Lieberman P, Kemp SF, Oppenheimer J, et al. The diagnosis and management of anaphylaxis: an updated practice parameter.
  J Allergy Clin Immunol
  . 2005;115(3):S483–S523.
  
• Simmons FER. Anaphylaxis: Recent advances in assessment and treatment.
  J Allergy Clin Immunol
  . 2009;124:625–636.
  
• Tang MLK, Osborne N, Allen K. Epidemiology of Anaphylaxis.
  Curr Opin Allergy Clin Immunol
  . 2009;9:351–356.
  
• Thomas M, Crawford I. Glucagon infusion in refractory anaphylactic shock in patients on beta-blockers.
  Emerg Med J
  . 2005;22:272–273.
  

See Also (Topic, Algorithm, Electronic Media Element)

• Angioedema
  
• Urticaria
  

CODES

• 989.5 Toxic effect of venom
  
• 995.0 Other anaphylactic reaction
  
• 995.60 Anaphylactic reaction due to unspecified food
  

BASICS

• Reduction below normal in the mass of RBCs
  
• Measured by 1 or more of the major RBC components:
  
  • Hemoglobin (Hgb): Concentration of the major oxygen-carrying component in whole blood
    
  • Hematocrit (Hct): Percent volume of whole blood occupied by intact RBCs
    
  • RBC count: RBCs contained in a volume of whole blood
    
• Adult female: Hgb <12 g/dL or Hct <37%
  
• Adult male: Hgb <14 g/dL or Hct <42%
  
• Normal blood count values depend on age:
  
  • Birth: Hgb 16.5, Hct 51
    
  • 1 yr: Hgb 12, Hct 36
    
  • 6 yr: Hgb 12.5, Hct 37
    
  • Adult male: Hgb 14, Hct 42
    
  • Adult female: Hgb 12, Hct 37
    
• Hgb/Hct depend on oxygen pressure:
  
  • Increased in neonates and people living above 4,000 ft
    
• Hgb, Hct, and RBC count are concentrations:
  
  • Dependent on RBC mass and plasma volume
    
  • Values decrease if RBC mass decreases or plasma volume increases.
    
• Anemia is an indication of an underlying disorder or deficiency.
  

• Never a normal variant:
  
  • May be the first manifestation of a systemic disorder
    
  • Always seek a cause.
    
• Excessive blood loss (most common cause):
  
  • Trauma
    
  • GI bleed
    
  • Menstruation
    
• Hemolysis (increased RBC destruction, RBC lifespan <100 days):
  
  • Hypersplenism
    
  • Autoimmune hemolytic anemia
    
  • Mechanical trauma (prosthetic heart valves, vasculitis, thrombotic thrombocytopenic purpura [TTP], hemolytic uremic syndrome [HUS], or disseminated intravascular coagulation [DIC])
    
  • Toxins
    
  • Infections (malaria, babesiosis)
    
  • Membrane abnormalities
    
  • Intracellular RBC abnormalities (G6PD, sickle cell anemia, or thalassemia)
    
• Decreased RBC synthesis:
  
  • Classified by measurement of RBC size
    
  • Hypochromic/microcytic:
    
    • Iron deficiency
      
    • Thalassemia
      
    • Sideroblastic
      
    • Chronic disease
      
  • Normochromic/macrocytic:
    
    • Hypothyroidism
      
    • Folate deficiency
      
    • Vitamin B
      ₁₂
      deficiency
      
    • Liver disease
      
    • Myelodysplasia
      
    • Certain leukemias
      
  • Normochromic/normocytic:
    
    • Aplastic anemia
      
    • Chronic renal failure
      
    • Malignancy
      
    • Adrenal insufficiency
      
    • Hyperparathyroidism
      
    • Alcohol abuse
      
    • Acute blood loss
      

DIAGNOSIS

Depends on:

• Rapidity of onset:
  
  • Hypovolemia if acute
    
  • Asymptomatic if mild and chronic
    

• Underlying disease
  
• Severity and type of anemia
  
• Fatigue
  
• Decreased exercise intolerance
  
• Shortness of breath
  
• Dyspnea on exertion
  
• Chest pain/angina
  
• Syncope
  
• Blood in stool/tarry black stools
  
• Irregular or heavy menses
  
• Easy bruising or history of excessive bleeding
  

• Cardiovascular:
  
  • Tachycardia, cardiomegaly, or murmurs
    
  • Postural hypotension
    
• Dermatologic:
  
  • Skin:
    
    • Cool
      
    • Pallor
      
    • Jaundice
      
    • Purpura
      
    • Telangiectasia
      
    • Petechiae
      
    • Ecchymosis
      
  • Spoon-shaped nails (koilonychia)
    
• Neurologic:
  
  • Neuropathy
    
  • Altered mental status
    
• Bone (especially sternal) or joint pain (sickle cell disease)
  
• Hepatomegaly, splenomegaly
  
• Lymphadenopathy
  
• Findings reflect underlying disease
  

• CBC
  
• Vital signs/orthostatics
  
• Determine if:
  
  • Bleeding
    
  • Increased RBC destruction
    
  • Bone marrow suppression
    
  • Iron deficient
    

• Type and crossmatch or type and screen
  
  • Depends on severity
    
• CBC
  
  • RBC indices:
    
    • Mean corpuscular volume (MCV; normal: 80–100 μm
      ³
      )
      
    • Mean corpuscular hemoglobin (MCH; normal: 27–34 pg/cell)
      
    • Mean corpuscular hemoglobin concentration (MCHC; normal: 33–36%)
      
  • Platelet count
    
    • Thrombocytosis suggests:
      
      • Iron deficiency
        
      • Myeloproliferative disorders
        
      • Inflammation
        
      • Infection
        
      • Neoplasm
        
    • Thrombocytopenia suggests:
      
      • Bone marrow malignancy
        
      • Hypersplenism
        
      • Sepsis
        
      • Vitamin B
        ₁₂
        or folate deficiency
        
      • Autoimmune disorders
        
• Reticulocyte (retic) count:
  
  • Normal 0.5–1.5% (retics/1,000 RBCs)
    
  • Increased retic count: Increased erythropoietic response to continued blood loss or hemolysis
    
  • Stable anemia with low retic count: Impaired RBC production
    
  • Active hemolysis or blood loss with low retic count: Concurrent disorder
    
  • Low retic count with pancytopenia: Aplastic anemia
    
  • Low retic count with normal WBC and platelets: Pure RBC aplasia
    
• Reticulocyte index (RI): Retic count (%) × (patient Hct/normal Hct):
  
  • RI <2% implies inadequate RBC production.
    
  • RI >2% implies increased RBC production with excessive RBC destruction or loss.
    
• WBC with differential and peripheral smear:
  
  • Leukopenia with anemia suggests bone marrow suppression, hypersplenism, or deficient vitamin B
    ₁₂
    /folate
    
• Stool for occult blood
  
• Electrolytes, BUN, creatinine, glucose:
  
  • Chronic renal failure
    
• Urinalysis:
  
  • Hematuria
    
  • Hemoglobinuria in hemolytic anemia
    
• Workup strategy:
  
  • Hypochromic/microcytic anemias:
    
    • Iron
      
    • Total iron-binding capacity
      
    • Transferrin saturation
      
    • Ferritin
      
  • Macrocytic anemias:
    
    • Folate
      
    • Vitamin B
      ₁₂
      
    • LFT
      
    • Thyroid function tests
      
  • Hemolytic anemia:
    
    • Rapid fall in Hgb
      
    • Reticulocytosis
      
    • Fragmented RBCs
      
    • Increased LDH
      
    • Increased indirect bilirubin
      
    • Decreased serum haptoglobin
      
    • Coombs positive
      
• Special tests:
  
  • Peripheral smear:
    
    • Helmet cells/schistocytes—microangiopathic hemolysis
      
    • Teardrop cells—myelofibrosis
      
    • Spherocytes—autoimmune hemolysis
      
    • Leukoerythroblastic pattern—bone marrow replacement
      
    • Bite cells—oxidative hemolysis
      
    • RBC parasites—malaria or babesiosis
      
    • Target cells—liver disease
      
    • Burr cells—uremia
      
    • Sideroblasts—alcoholism or myelodysplasia
      
    • Howell–Jolly bodies—asplenia
      
  • Hgb electrophoresis for sickle cell/thalassemia
    
  • Iron, iron-binding capacity, transferrin saturation, ferritin:
    
    • Iron deficiency
      
    • Iron—decreased
      
    • Iron-binding capacity—increased
      
    • Transferrin saturation—decreased
      
    • Ferritin—decreased
      
  • Chronic disease:
    
    • Iron—decreased
      
    • Iron-binding capacity—decreased
      
    • Transferrin saturation—decreased/normal
      
    • Ferritin—normal/increased
      
  • Thalassemia:
    
    • Iron—normal
      
    • Iron-binding capacity—normal
      
    • Ferritin—normal
      
  • Sideroblastic anemia:
    
    • Iron—increased
      
    • Iron-binding capacity—normal
      
    • Ferritin—increased