Shock, Emergency Medicine

Basics

Description

Inadequate supply of blood flow to tissues to meet the demandsof the tissues
Tissue oxygen requirements are not fulfilled.
Toxic metabolites are not removed.
If untreated, inevitable progression from inadequate perfusion to organ dysfunction and ultimately to death.
Major categories of shock:
- Hypovolemic shock:
  - Decreased blood volume
  - Suspect hemorrhage if acute onset
  - Severe dehydration if progressive onset and elevated hematocrit, BUN, and creatinine
- Obstructive (cardiogenic) shock:
  - Decreased cardiac output and tissue hypoxia with adequate intravascular volume and myocardial dysfunction
  - Venous congestion with increase in central venous pressure
  - Compensatory increase in SVR
  - May be caused by cardiac dysfunction, obstruction to inflow of blood to the heart, or obstruction to outflow of blood from the heart
- Septic shock:
  - An initial infectious insult overwhelms the immune system.
  - Biochemical messengers (cytokines, leukotrienes, histamines, prostaglandins) cause vessel dilatation.
  - Capillary endothelium becomes disrupted and the vessels leak.
  - Drop in SVR leads to inadequate tissue perfusion.
  - Secondarily, decreased cardiac output from "cardiac stun " resulting in cold septic shock
- Neurogenic shock:
  - Spinal cord insults disrupt sympathetic stimulation to vessels.
  - Loss of sympathetic tone causes arteriodilating and vasodilatation.
  - Lesions proximal to T4 disrupt sympathetic, spares vagal innervation causing bradycardia.
- Anaphylactic shock:
  - An antigen stimulates the allergic reaction.
  - Mast cells degranulate.
  - Histamine releases, along with autocoids, stimulate an anaphylaxis cascade.
  - Vascular smooth muscle relaxes.
  - Capillary endothelium leaks.
  - Drop in SVR leads to inadequate tissue perfusion.
- Pharmacologic agents may cause shock through smooth muscle dilation or myocardial depression.

Etiology

Hypovolemic shock:
- Abdominal trauma, blunt or penetrating
- Abortion " complete, partial, or inevitable
- Anemia " chronic or acute
- Aneurysms " abdominal, thoracic, dissecting
- Aortogastric fistula
- Arteriovenous malformations
- Blunt trauma
- Burns
- Diabetes
- Diarrhea
- Diuretics
- Ruptured ectopic pregnancy
- Epistaxis
- Fractures (especially long bones)
- Hemoptysis
- GI bleed
- Mallory " Weiss tear
- Penetrating trauma
- Placenta previa
- Postpartum hemorrhage
- Retroperitoneal bleed
- Severe ascites
- Splenic rupture
Toxic epidermal necrolysis:
- Vascular injuries
- Vomiting
Cardiogenic shock:
- Cardiomyopathy
- Conduction abnormalities and arrhythmias
- MI
- Myocardial contusion
- Myocarditis
- Pericardial tamponade
- Pulmonary embolus
- Tension pneumothorax
- Valvular insufficiency
- Ventricular septal defect
Vasogenic shock:
- Acute respiratory distress syndrome
- Bacterial infection
- Bowel perforation
- Cellulitis
- Cholangitis
- Cholecystitis
- Endocarditis
- Endometritis
- Fungemia
- Infected indwelling prosthetic device
- Intra-abdominal infection or abscess
- Mediastinitis
- Meningitis
- Myometritis
- Pelvic inflammatory disease
- Peritonitis
- Pyelonephritis
- Pharyngitis
- Pneumonia
- Septic arthritis
- Thrombophlebitis
- Tubo-ovarian abscess
- Urosepsis
Anaphylactic:
- Drug reaction (most commonly to aspirin, ²-lactam antibiotics)
- Exercise (rare)
- Food allergy (peanuts, tree nuts, shellfish, fish, milk, eggs, soy, and wheat account for 90% of food-related anaphylaxis)
- Insect sting
- Latex
- Radiographic contrast materials
- Synthetic products
Pharmacologic:
- Antihypertensives
- Antidepressants
- Benzodiazepines
- Cholinergics
- Digoxin
- Narcotics
- Nitrates
Neurogenic:
- Spinal cord injury

Diagnosis

Signs and Symptoms

Generalized shock:

Hypotension
Decreased peripheral pulses
Tachycardia
Tachypnea
Decreased urine output
Diaphoresis
Obtundation
Lethargy

History
Standard medical history with a goal of deducing the etiology of the shock and important precipitating factors
Physical Exam

Standard physical exam to assist in determining the etiology (e.g., wounds, cardiac exam signs of cellulitis and urticarial rash, etc.)
Targeted physical exam to focus on the type of shock state:
- Hypovolemic (classic symptoms):
  - Neck veins are flat.
  - Mucous membranes are dry.
  - Extremities are cold.
- Cardiogenic shock (classic symptoms):
  - Jugular venous distension is present.
  - Mucous membranes are moist.
  - Extremities are cold.
- Early septic shock (classic symptoms):
  - Neck veins are flat.
  - Mucous membranes are dry.
  - Extremities are warm.
  - During late shock, extremities may become cold and mottled.

Essential Workup

Identify type or types of shock present.
Identify underlying cause of shock.

Diagnosis Tests & Interpretation

Lab

Hemoglobin/hematocrit
WBC:
- High: Nonspecific marker of infection
- Low: Neutropenic infections
Electrolytes
Blood glucose:
- High: Diabetic ketoacidosis or septic shock
- Low: Pediatric sepsis
Prothrombin time/partial thromboplastin time
Cardiac enzymes
Urinalysis
²-human chorionic gonadotropin
Lactic acid level:
- Good surrogate marker of shock state

Imaging

CXR
ECG
Abdominal US
CT abdomen:
- Requires that the patient 1st be stabilized
- In the setting of abdominal trauma and in search for suspicion of abdominal infection

Diagnostic Procedures/Surgery
EKG:

Assess for ischemia and other disorders of cardiac muscle:
Electrical alternans or low voltage with cardiac tamponade
Right-heart strain with pulmonary embolism

Treatment

Pre-Hospital

ABCs per standard protocol
Fluid resuscitation as warranted

Initial Stabilization/Therapy

Large-bore IV access:
- When possible, central venous access and monitoring
Fluid resuscitation in noncardiogenic shock patients
Control bleeding with direct pressure measures.
Stabilization of a fractured pelvis with sheet or commercial device or external fixation

Ed Treatment/Procedures

Hypovolemic shock:
- Identify source of volume depletion
- Aggressive fluid resuscitation keeping systolic blood pressure (SBP) >100 mm Hg until definitive treatment
- 2 " 3 L crystalloid initially
- Packed RBCs if 2 " 3 L crystalloids do not improve SBP
- Identify source of bleeding and rapidly move toward definitive treatment.
- Thoracotomy and aortic cross-clamping in refractory shock with penetrating torso trauma
Cardiogenic shock:
- Ease work of breathing with intubation
- Insult-specific therapy (e.g., thrombolytics for MI, pericardiocentesis for pericardial tamponade)
- Treat dysrhythmias.
- Vasopressors (norepinephrine or dopamine) as needed
Septic shock:
- Aggressive crystalloid fluid resuscitation
- Titrate fluid to urine output >30 cc/hr
- Blood product transfusion to maintain HCT 30 " 35%
- Early antimicrobial therapy
- Inotropic support as needed
- Norepinephrine as preferred 1st-line infusion
Anaphylactic shock:
- Intubation for airway compromise
- Epinephrine
- Subcutaneous in noncritical settings
- IV drip for immediate life threats or refractory hypotension
- H1 blockers (diphenhydramine)
- H2 blockers (cimetidine)
- Corticosteroids (hydrocortisone or methylprednisolone)
- Nebulized ²2-antagonists for bronchospasm
- Patients taking ²-blockers may be more likely to experience severe symptoms of anaphylaxis
Pharmacologic shock:
- Decontamination of overdoses with charcoal
- Inotropic agents as needed
- Drug-specific antidotes
Neurogenic shock:
- Supportive therapy
- Traction and fracture stabilization
- Corticosteroids

Medication

Albuterol: 2.5 mg/2.5 cc nebulizer PRN
Calcium gluconate: 100 " 1,000 mg IV at 0.5 " 2 mL/min
Cimetidine: 300 mg IV
Diphenhydramine: 50 " 100 mg IV over 3 min
Dobutamine: 5 " 40 ¼g/kg/min IV:
- Dopaminergic: 1 " 3 ¼g/kg/min IV
- ²-effects: 3 " 10 ¼g/kg/min IV
- α/ ²-effects: 10 " 20 ¼g/kg/min IV
- α-effects: 20 ¼g/kg/min IV
Epinephrine:
- 1 " 4 ¼g/min IV infusion
- Endotracheal 1 mg (10 mL of 1:10,000) once followed by 5 quick insufflations
- Place 1 mg in 250 mL D5W = 4 ¼g/mL
Glucagon: 1 " 5 mg IV bolus initial, then 1 " 20 mg/h infusion
Hydrocortisone: 5 " 10 mg/kg IV
Methylprednisolone: 1 " 2 mg/kg IV
Naloxone: 0.01 mg/kg IV initial, titrate to effect
Norepinephrine: Start 2 " 4 ¼g/min IV, titrate up to 1 " 2 ¼g/kg/min IV
Phenylephrine: 40 " 180 ¼g/min IV

Follow-Up

Disposition

Admission Criteria

All patients in shock need to be admitted.
ICU criteria:
- All patients with persistent shock need ICU monitoring.
Patients with shock definitively reversed may be admitted to non-ICU setting (e.g., tension pneumothorax that has been decompressed and chest tube placed).

Discharge Criteria
Patients who are in shock should not be discharged home from the ED.
Issues for Referral

Traumatic hypovolemic shock (hemorrhagic shock) patients may require a trauma center.
Patients with cardiogenic shock due to MI may require cardiac catheterization or additional cardiac surgery support.
Septic shock due to necrotizing fasciitis may require advanced surgical support.
Neurogenic shock with spinal cord injury will require neurosurgical care.

Pearls and Pitfalls

Identify the etiology of shock.
Aggressively resuscitate the patient, 1st with IV fluids and next with vasopressor support to minimize hypoxic exposure.

Additional Reading

Havel C, Arrich J, Losert H, et al. Vasopressors for hypotensive shock. Cochrane Database Syst Rev. 2011;(5):CD003709.
Puskarich MA. Emergency management of severe sepsis and septic shock. Curr Opin Crit Care. 2012;18(4):295 " 300.
Strehlow MC. Early identification of shock in critically ill patients. Emerg Med Clin North Am. 2010;28(1):57 " 66, vii.

Codes

ICD9

785.50 Shock, unspecified
785.51 Cardiogenic shock
785.59 Other shock without mention of trauma
785.52 Septic shock
995.0 Other anaphylactic reaction

ICD10

R57.0 Cardiogenic shock
R57.1 Hypovolemic shock
R57.9 Shock, unspecified
R65.21 Severe sepsis with septic shock
R57.8 Other shock
R57 Shock, not elsewhere classified
T78.2XXA Anaphylactic shock, unspecified, initial encounter

SNOMED

27942005 shock (disorder)
39419009 Hypovolemic shock (disorder)
89138009 Cardiogenic shock (disorder)
76571007 Septic shock (disorder)
129577007 Neurogenic shock
35001004 Anaphylactoid reaction (disorder)

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