Definition of shock:
acute circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in generalized tissue hypoxia
Name the 6 types of shock:
1) hypovolemic 2) cardiogenic 3) distributive (septic, anaphylactic) 4) neurogenic 5) traumatic 6) obstructive
What is the pathophysiology of shock in general?
tissue hypoperfusion causing a cellular energy deficit; supply/demand imbalance resulting in neuroendocrine and inflammatory responses
What are the 4 stages of shock?
1 initial 2 compensatory 3 progressive 4 refractory
What are the characteristics of the initial stage of shock?
Hypo-perfusion, tissue hypoxia, lactic acidosis
What are the characteristics of the compensatory stage of shock?
Cytokine release, hyperventilation for CO 2 removal, endogenous catecholamine release (norepinephrine and epinephrine)
What are the characteristics of the progressive stage of shock?
Failing compensatory mechanisms, worsening capillary leakage and metabolic acidosis, increased blood viscosity, micro-sludging, worsening organ dysfunction (MODS)
What are the characteristics of the refractory stage of shock?
Irreversible organ damage, cell death, degradation of ATP to adenosine
4 different categories of hemodynamic shock?
hypovolemic, cardiogenic, distributive, obstructive
Possible causes of hypovolemic shock?
hemorrhagic, GI/UT volume loss, third spacing
Cause of cardiogenic shock?
myocardial pump failure
Causes of distributive shock?
sepsis, anaphylaxis, spinal cord injury, corticosteroid insufficiency
Possible causes of obstructive shock?
tamponade, tension pneumothorax, PE all lead to equalization of diastolic pressures with filling pressures
What is the mortality of shock?
hypovolemic - variable cardiogenic - 60-90% spetic - 35-40%
What are the determinants of shock?
Loss of circulating intravascular volume • Inadequate capillary and tissue perfusion (micro circulation) • Disturbed cell metabolism • Mismatch of oxygen delivery and oxygen demand
The body's systemic physiological reaction to shock:
-- Progressive vasoconstriction – Increased blood flow to vital organs: Shunt of skin, acral regions, splanchnic system – Increase in CO/CI – Increase in respiratory rate and tidalvolume – Reduced urine production – Reduction gastric and intestinal activity
What does shock do to the kidneys?
Acute kidney injury: tubular necrosis and subsequent kidney failure
What does shock do to the liver?
congestion with elevated liver enzymes and coagulopathy
What does shock do to the GI tract?
Gastrointestinal ischemia: GI hemmorhage, peritonitis
Definition of cardiogenic shock:
Protracted severe malperfusion of tissues due to an acute, critical reduction in myocardial pump capacity Need to exclude other correctible factors: hypovolemia, arterial hypoxia, vasovagal rxn
What percent of MI pt end up with cardiogenic shock?
5-10% and Cardiogenic shock is considered the cause of death in 50-90% of these patients
What are the clinical signs of cardiogenic shock?
• Signs of centralized circulation and organ dysfunction • Agitation • Pale, cool, clammy skin • Oliguria (< 20ml/h) • RV dysfuntion (e.g. PE, RCA MI) : – Elevated venous pressures, jugular distention • LV dysfunction (e.g. LAD/Cx MI, acute AI/MR): – Pulmonary edema
The etiology of cardiogenic shock can be one of two categories:
myocardial or mechanical
Pathophysiology of ischemic cardiogenic shock?
inadequate myocardial perfusion (decreased duration of diastole) excessive increase in myocardial oxygen consumption (tachycardia and increse wall tension) metabolic derangement (lactic acidosis)
Activation of SNS during ischemic cardiogenic shock is triggered by what and results in what?
triggered by critical decrease in stroke volume causes increased preload and afterload
What tests are used to diagnose ischemic cardiogenic shock?
• 12-channel- EKG: Signs of ischemia?, arrhythmias ? if Normal EKG: cardiogenic shock due to MI unlikely • Chest X ray • Arterial blood gas (VBG) • Basic chem, CBC, cardiac enzymes • Serial lactate levels (indicator of perfusion)
Cardiogenic shock general management goals?
Optimize ventricular filling Improve coronary perfusion pressure With acute MI as cause: coronary angiography and immediate revascularization
Drugs that can be used to improve coronary perfusion pressure:
Vasopressors (norepinephrine, phenylepinephrine) Inotropics (dobutamine, epinephrine, milrione) IABP, mechanical circulatory support
What is SIRS?
Systemic inflammatory response syndrome
What is MODS?
Multi organ dysfunction syndrome – inflammatory injury involving more than one vital organ
What is the criteria for SIRS?
at least 2 of the following criteria • Tachypnea >20 breaths per minute Or PaCO2 < 32 mmHg • WBC < 4000cells/mm3 or > 12000 cells/mm3 • Heart rate > 90 beats per minute • Fever > 38.0 °C (100.4 °F) or hypothermia < 36.0 °C (96.8°F)
What is sepsis?
SIRS with infection usually with at least one of the following: Alteration in mental state Hypoxemia Elevated plasma lactate level Oliguria
What is septic shock?
the result of dysfunction of the endothelium and vasculature secondary to circulating inflammatory mediators and hypotension results from failure of the vascular smooth muscle to constrict appropriately
What is severe sepsis?
sepsis plus sepsis-induced organ dysfunction or tissue hypoperfusion
What is primary MODS?
Direct result of insult, organ dysfunction occurs early in the course and can be directly attributable to insult
What is secondary MODS?
Consequence of a host response (e.g cytokine release) Inflammatory host response to toxins and other components of microorganisms -> clinical manifestations of sepsis
What is cardiogenic shock?
defined as circulatory pump failure leading to diminished cardiac output and subsequent tissue hypoxia
What are the hemodynamic findings of cardiogenic shock?
Hemodynamic criteria include sustained hypotension (SBP <90 mmHg ), reduced cardiac index (<2.2 L/min per square meter), and elevated pulmonary artery wedge pressure (>15 mmHg).
What are the causes of cardiogenic shock?
Acute myocardial infarction (most common), cardiomyopathies, myocarditis, acute and chronic valve disease, severe arrhythmias, etc.
What is obstructive shock?
caused by a number of different etiologies that result in mechanical obstruction of venous return decreasing ventricular filling
Etiologies of obstructive shock?
pericardial tamponade, pulmonary embolism, tension pneumothorax, IVC obstruction, venous air embolism, etc.
diminished tissue perfusion as a result of loss of vasomotor tone usually secondary to spinal cord injuries that disrupt sympathetic regulation is what kind of shock?
systemic response after trauma, combining the effects of soft tissue injury, long bone fractures, and blood loss is what kind of shock?
hypoperfusion deficit in traumatic shock is magnified by what?
proinflammatory activation that occurs following the induction of shock via inflammatory mediators released in response to tissue injury
What is hemorrhagic shock?
Loss of oxygen supply/delivery
Treatment for hemorrhagic shock?
– Cristalloid solutions
– Colloid solutions (HAES)
– Small Volume Resuscitation