Transcript SHOCK - THD Internal Medicine Training Program

Pathyophysiology and
Classification of Shock
KENNEY WEINMEISTER M.D.
Definition

Shock is a physiologic state characterized
by a significant, systemic reduction in tissue
perfusion, thereby resulting in decreased
tissue oxygen delivery.
Stages of Shock


Early, Preshock, Warm shock
Compensation by body’s homeostatic
mechanisms
• Tachycardia, Peripheral vasodilatation and
modest decrement in systemic BP
Stages of Shock



Shock
Homeostatic mechanisms are overwhelmed
Signs and symptoms of organ dysfunction
• Tachycardia, tachypnea, metabolic acidosis,
oliguria, and cool and clammy skin
• 20 to 25% fall in effective blood volume
• Fall in CI to < 2.5L/min/M2
• Activation of mediators of sepsis
Stages of Shock


End Organ Dysfunction
Pathophysiology
•
•
•
•
AG II & NE cause increased Ca+2 in cytosol
Ca + calmodulin = P+myosin
P+myosin + actin = Myosin ATPase
Myosin ATPase = muscle contraction
Pathophysiology of End Organ
Shock

Activation of ATP sensitive potassium
channels
• Activation causes hyperpolarization
• Closure of Ca channels
• Activated by decrease in cellular ATP and
increases in cellular H+ and lactate
• Natriuretic peptide and nitric oxide
Pathophysiology of End Organ
Shock

Increased production on Nitric Oxide
• activation of myosin light-chain phosphatase
• leads to dephosphoralation of myosin

Vasopressin deficiency
•
•
•
•
potentiates vasoconstrictor effects of NE
directly inactivates Katp channels
blunts increase in cGMP
decreases synthesis of NO synthase
Pathophysiology of End Organ
Shock



Vascular smooth muscle tone is lost
Resistant vasodilatation
End organ dysfunction and death
Classification of Shock



Hypovolemic shock
Cardiogenic shock
Distributive shock
Hypovolemic Shock


Results from decreased preload
Hemorrhagic
• Trauma, GIB, Ruptured aneurysm

Volume loss
• Third spacing, GI losses, burns, insensible
losses
Cardiogenic Shock


Pump failure
Cardiomyopathies
• Ischemic right and left ventricle,
• Dilated
• Stunned myocardium
Cardiogenic Shock continued

Arrhythmia's
• Bradyarrhythmias
• Tachyarrhythmias

Mechanical
• Valvular; MR, AI, AS
• VSD
• Atrial myxoma
Cardiogenic Shock continued

Obstructive
•
•
•
•
•
Massive PE
Tension pneumothorax
Constrictive pericarditis
Tamponade
Severe pulmonary hypertension
Distributive Shock

Vasodilatory shock resulting in severe
decrease in SVR
•
•
•
•
•
Septic shock
Activation of systemic inflammatory response
Toxic shock syndrome
Anaphylaxis
Drug or toxins
Distributive Shock continued



Addisonian crisis
Myxedema coma
Neurogenic shock
Evaluation




H&P
Labs
CXR
EKG
Treatment

Goal is early intervention to prevent
irreversible organ damage
• Recognize early shock
• Diagnose and correct the underlying cause

Early goal directed therapy in sepsis
• In hospital mortality 46.5% vs 30.5% for
treatment group
• NEJM, vol 345,No 19 Nov 8 2001
Treatment

Fluid resuscitation
• CVP 8-12

Vasopressors
•
•
•
•
Norepinephrin infuse mcg/min (4mcg/min)
Dopamine infuse mcg/kg/min
Epinephrine infuse mcg/min (range 1-10 mcg)
Vasopressin infuse units/min (range 0.01 to 0.1
units/minute)
No bubble is so iridescent or
floats longer than that blown by
the successful teacher.
Sir William Osler