Author:
Annette M.Ilg
Nathan I.Shapiro
Description
- Inadequate supply of blood and oxygen to meet the metabolic demand s of the tissues
- 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 circulating blood volume
- Suspect hemorrhage if acute onset
- Severe dehydration if progressive onset and elevated hematocrit, BUN, and /or creatinine
- Obstructive (cardiogenic) shock:
- Decreased cardiac output and myocardial dysfunction leading to tissue hypoxia in the setting of adequate intravascular volume
- Venous congestion with increase in central venous pressure
- Compensatory increase in SVR
- May be caused by cardiac dysfunction or obstruction of inflow/outflow of blood to/from the heart
- Septic shock:
- An initial infectious insult overwhelms the immune system
- Biochemical messengers (cytokines, leukotrienes, histamines, prostagland ins) cause vessel dilatation
- Capillary endothelium become disrupted causing vascular leak
- Drop in SVR leads to inadequate tissue perfusion
- Secondarily, decreased cardiac output from “cardiac stun” results 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
- Septic 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, β-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:
Signs and Symptoms
Generalized shock:
- Hypotension
- Decreased peripheral pulses
- Tachycardia (except neurogenic)
- Tachypnea
- Decreased urine output
- Diaphoresis
- Obtundation
- Lethargy
History
Stand ard medical history with a goal of deducing the etiology of the shock and important precipitating factors
Physical Exam
- Stand ard 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
Diagnostic 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
- β-human chorionic gonadotropin
- Lactic acid level:
- Good surrogate marker of shock state
Imaging
- CXR
- ECG
- Abdominal US
- Cardiac echo
- CT abdomen:
- Requires that the patient first be stabilized
- In the setting of abdominal trauma and in search for suspicion of abdominal infection
Diagnostic Procedures/Surgery
ECG:
Prehospital
- ABCs per stand ard 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
- Consider 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 and MAP >65 mm Hg
- Blood product transfusion to maintain HCT 30-35%
- Early antimicrobial therapy
- Inotropic support as needed
- Norepinephrine as preferred first-line infusion
- Anaphylactic shock:
- Intubation for airway compromise
- Epinephrine 0.3 mg IM
- Subcutaneous in noncritical settings
- IV drip for immediate life threats or refractory hypotension
- H1 blockers (diphenhydramine)
- H2 blockers (cimetidine)
- Corticosteroids (hydrocortisone or methylprednisolone)
- Nebulized β2-antagonists for bronchospasm
- Patients taking β-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 p.r.n
- 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
- Dopamine 5-40 μg/kg/min IV:
- Dopaminergic: 1-3 μg/kg/min IV
- β-effects: 3-10 μg/kg/min IV
- α/β-effects: 10-20 μg/kg/min IV
- α-effects: 20 μg/kg/min IV
- Epinephrine:
- 1-4 μg/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 μg/mL
- Glucagon: 1-5 mg IV bolus initial, then 1-20 mg/hr 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 μg/min IV, titrate up to 1-2 μg/kg/min IV
- Phenylephrine: 40-180 μg/min IV
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 or other operative diseases may require advanced surgical support
- Neurogenic shock with spinal cord injury will require neurosurgical care