Shock


Shock occurs when there is inadequate tissue oxygenation to meet demand. Shock may be thought of as belonging to one of four categories: hypovolemic, cardiogenic, obstructive, or distributive. Some emergency physicians like to add a fifth category, dissociative shock, in which the ability to use O2 is impaired (carbon monoxide or cyanide poisoning).

SYMPTOMS/EXAM

DIAGNOSIS

  Examples CO SVR PCOP SvO2
Distributive
Cardiogenic
  • Acute MI
  • CHF.

(except in RV infarct)
Hypovolemic
  • Trauma
  • Bleeding.
Obstructive
  • Tamponade
  • Pulmonary embolism
  • Tension pneumothorax
(tamponade) or
(Pulmonary embolism)

Laboratory evidence for inadequate tissue oxygenation:
  • Base deficit more negative than -5 mEq/L.
  • Serum lactate > 4 mmol/L.
  • Multiorgan dysfunction.


TREATMENT


Choice of Pressor in Shock:
Hemodynamics Initial Tx Comments
↓PCWP (or CVP) Aggressive volume expansion: Albumin no better than NS Volume >> pressors; reevaluate once CVP > 12
CO↓, SVR↑ Dobutamine Alternate: milrinone or dopamine + nitroprusside
CO↓, SVR↓ Dopamine VS Norepinephrine  
CO↑, SVR ↓ High Dose Dopamine OR Norepinephrine Add Epinephrine or Phenylephrine for refractory hypotension


Agent Receptor Activity Effects Indication
a1 b1 b2 DA
(Levophed)
Norepinephrine
1-30 mcg/min
+++

 

++ 0 0 SVR ↑↑
CO ↔↓↑
Sepsis
Phenylephrine
(Neo-synephrine)
40-180 mcg/min
+++

 

0

 

0

 

0

 

SVR ↑↑
CO ↔/↑
Sepsis,
Neurogenic shock
Epinephrine +++

 

+++ ++ 0

 

CO ↑↑
SVR ↓ (L)
SVR ↔/↑ (H)
Anaphylaxis,
ACLS,
Sepsis
Dopamine (mcg/kg/min)
Low-dose (0.5-2) 0 + 0 ++ CO ↑
SVR ↑↓
Sepsis,
Cardiogenic shock
Mid-dose(5-10) + ++ 0 ++ CO ↑
High-dose(10-20) ++ ++ 0 ++ SVR ↑↑
Doubutamine
2.5-20 mcg/kg/min
0/+ +++ ++ 0 CO ↑
SVR ↓
Cardiogenic shock
Isoproterenol
2-10 mcg/min
0

 

+++ +++ 0 CO ↑
SVR ↓
Cardiogenic shock w/
bradycardia
Vasopressin
(Adjunct)
0.01-0.04 U/min
        V2 receptors Vasoconstriction
Augments catecholamine

Receptor Functions
Receptor Function
α1  vascular smooth muscle contraction
pupillary dilator muscle contraction (mydriasis), 
intestinal and bladder sphincter muscle contraction
α2 sympathetic outflow, 
Insulin release
 lipolysis, 
platelet aggregation
β1 Heart rate
Contractility
Renin release
Lipolysis
β2 Vasodilation
Bronchodilation 
Heart rate
 Contractility
lipolysis
 Insulin release
 Uterine tone (tocolysis)
Ciliary muscle relaxation
 Aqueous humor production
M1 CNS, enteric nervous system
M2  Heart rate and contractility of atria
M3  exocrine gland secretions (e.g., lacrimal, salivary, gastric acid), 
gut peristalsis, 
bladder contraction,
Bronchoconstriction, 
pupillary sphincter muscle contraction (miosis),
Ciliary muscle contraction (accommodation)
D1 Relaxes renal vascular smooth muscle
D2 Modulates transmitter release, especially in brain
H1 nasal and bronchial mucus production, 
vascular permeability
Contraction of bronchioles
Pruritus
Pain
H2 gastric acid secretion
V1 vascular smooth muscle contraction
V2 H2O permeability and reabsorption in the collecting tubules of the kidney (V2 is found in the 2 kidneys)