Pathophysiology and Therapy of Shock Flashcards
what are the classic signs of shock?
tachycardia and increased pulse rate
tachypnea
pale and cool skin
mucous membrane pallor
delayed capillary refill time
reduced urine output
weak arterial pulses, abnormal pulse pressure
muscle weakness
pupillary dilation abnormal sensorium
what is the definition of shock?
clinical syndrome resulting when cardiac output is insufficient to fill the arterial tree with blood under sufficient pressure to provide organs and tissues with adequate blood flow
oxygen deficit to tissues
what characterizes shock?
reduced tissue perfusion
impaired oxygen delivery
inadequate cellular oxygen utilization
inadequate cellular energy production
what are the major mechanisms for lack of oxygen delivery/utilization to tissues (shock)?
inadequate blood volume
inadequate cardiac performance
inadequate vascular tone
tissue defect in oxygen utilization
what does higher sympathetic tone lead to?
faster heart rate
positive inotropy
positive chronotropy
increased vascular tone
what are some etiologies of shock?
hemorrhage/hypovolemic
traumatic
cardiogenic
septic
neurogenic
anaphylactic
what are the compensatory mechanisms from the sympathetic nervous system in shock?
increased heart rate
increased inotropy
vasoconstriction
increase blood pressure towards normal
hepatic glycogenolysis to increase blood glucose
what does the baroreceptor response in shock lead to?
increased cardiac output
what happens with the blood due to reduced cardiac output?
metabolic acidosis
elevated blood lactate
what do cats usually have in response to shock/critical illness?
bradycardia
hypothermia
hypoglycemia
what often happens in cardiogenic shock?
fluid volume typically excessive
ANP and BNP are elevated
jugular vein is distended
what is infection?
inflammatory response to the presence of microorganisms
what is endotoxemia?
endotoxin in the bloodstream
are fluids or diuretics indicated in cardiogenic shock?
diuretics often indicated
fluids often not indicated
what is septic shock?
severe sepsis with hypotension that is unresponsive to adequate fluid resuscitation
what criteria does an animal have to have 2/3 of to have systemic inflammatory response syndrome (SIRS)?
abnormal temperature
abnormal heart rate
tachypnea
leukocytosis, leukopenia, or significant left shift
what is multiple organ dysfunction syndrome (MODS)?
presence of organ dysfunction in 2 or more systems
how is cardiovascular dysfunction identified?
need for pressors
what is hypovolemic shock?
loss of circulating blood volume
what can cause hypovolemic shock?
hemorrhage
gastrointestinal losses
reduced intake of fluids
diuresis
third spacing of fluids
addison’s disease
what should you do after giving sufficient fluids if shock persists?
give pressors or inotropes
what is a shock dose of fluids for a dog and cat?
dog: 90 ml/kg in an hour
cat: 60 ml/kg in an hour
how should you bolus a dog with crystalloids in shock?
give bolus of 20 ml/kg, then reassess
repeat up to 3 times (80 ml/kg) then think about pressors, blood, colloids
what are the replacement fluid types?
0.9% NaCl
lactated ringer’s solution
plasmalyte A
do crystalloids stay in the intravascular space for long?
no
what is hypertonic saline used for?
very large animals
head trauma cases to minimize cerebral edema
maybe large breed dogs
what are some potential side effects of hypertonic saline?
hyperosmolarity
hemolysis
hypernatremia
hyperchloremia
hypotension or ventricular premature contractions if given too fast
what are colloids?
large, oncotically active particles
what do colloids maintain?
intravascular colloid osmotic pressure
how well do colloids persist in the intravascular space?
better than crystalloids
what is the total dose of colloids?
20 ml/kg
often 5 ml/kg boluses
why might you give fresh frozen plasma?
clotting factors
protein
what is cryoprecipitate?
clotting factors without the volume
what makes up frozen plasma?
protein
when might you use inotropes and vasopressors?
blood volume okay, heart or vascular tone abnormal
what is the main inotrope/vasopressor?
norepinephrine
what do beta-2 receptors stimulate?
vascular and bronchial receptors: vasodilation and bronchodilation
what do alpha-1 receptors stimulate?
vasoconstriction and increased blood pressure
when might colloids be used?
albumin dropping lower than 1.8-2.2
dropping total solids and bleeding without coagulopathy
capillary leak
what can happen with fluid overload?
fluid retention in lungs
peripheral fluid retention
associated with worse outcome
what is cardiogenic shock?
low cardiac output resulting from poor cardiac performance
what is included in the definition of cardiogenic shock?
low cardiac output
hypotension
signs of hypoperfusion
normal or elevated cardiac filling pressures
due to cardiac cause
how can you treat cardiogenic shock?
oxygen
determine and remove inciting cause
how difficult is septic shock to treat?
one of most difficult forms of shock to treat
what characterizes warm or hyperdynamic shock?
tachycardia
bounding pulses
fever
hyperglycemia
injected mucous membranes
fast capillary refill time
what are some complicating developments of septic shock?
inadequate circulating blood volume
poor left ventricle contractile function
loss of vasomotor tone
metabolic alterations leading to reduced ability of cells to utilize oxygen
when should you initiate antibiotics with septic shock?
within one hour of diagnosis
delayed initiation reduces survival
what mediates release of substances from mast cells and basophils in anaphylactic shock?
IgE
what is anaphylaxis in dogs often associated with?
spontaneous abdominal effusion +/- gall bladder edema
how can you treat anaphylactic shock?
epinephrine
oxygen
IV crystalloid fluid bolus
re-evaluate vitals plus PCV, TS, lactate
what is neurogenic shock?
loss of vasomotor tone
increased vascular capacity leads to pooling
what are some causes of neurogenic shock?
anesthesia too deep
CNS disease
trauma
ischemia to vasomotor centers
what is the equation for oxygen delivery?
DO2= CO x CaO2
CaO2= oxygen content of arterial blood
what affects stroke volume?
preload
afterload
myocardial contractility
what does the cerebral ischemic response lead to?
vasoconstriction via sympathetic nervous system
what does reticuloendothelial cell depression from reduced cardiac output lead to?
liver/spleen cannot clear endotoxin and bacteria
what inflammatory cytokines are released during reduced cardiac output?
tumor necrosis factor
interleukin I
platelet activating factor
other cytokines
what systems can be involved in multiple organ dysfunction syndrome (must have two or more)?
kidneys
cardiovascular
respiratory
hepatic
coagulation
what does a 10% loss of circulating blood volume lead to?
little change in mean arterial pressure
what is the dose of hypertonic saline?
4 ml/kg over more than 10 minutes
what are some colloids?
hetastarch
dextrans
gelatin
albumin
hemoglobin-based oxygen carriers
what are some disadvantages of colloids?
more expensive
possible renal toxicity
coagulopathy
anaphylactic reactions
not cleared quickly
no clear survival benefit
reduced survival in human trauma cases
what is gram negative septic shock like?
various bacterial toxins plus endotoxin
when might you give steroids in septic shock?
if dependent on vasopressors
what is perhaps the most effective treatment for head trauma?
insure adequate blood pressure
what are the etiologies of shock?
hemorrhagic/hypovolemic
traumatic
cardiogenic
septic
neurogenic
anaphylactic
what does antidiuretic hormone release lead to?
water retention
vasoconstriction to raise blood pressure
what does reduced gastrointestinal perfusion lead to?
bacterial translocation
what does vasodilator release lead to in shock?
circulatory pooling and loss of effective circulating volume
what is myocardial failure in reduced cardiac output from?
cytokines
coronary thrombosis
low cardiac perfusion
what is severe sepsis?
sepsis with organ dysfunction and hypoperfusion
what does a loss of 15-20% of the circulating blood volume lead to?
MAP low normal 80-90 mmHg
spontaneous recovery possible
what is an adverse reaction to crystalloids?
fluid overload if give too much
how much of the administered volume of crystalloids remains in the intravascular space after an hour?
1/4 to 1/5 of administered volume
will the effects of hypertonic saline persist if they are not followed by crystalloids?
no
what is cryoprecipitate?
clotting factors without the volume of plasma
what are some inotropes and vasopressors?
dopamine
dobutamine
norepinephrine
phenylephrine
milrinone or inamrinone
what do beta 1 agonists stimulate?
cardiac receptors: increase heart rate and contractility
what do beta 2 agonists stimulate?
vascular and bronchial receptors: vasodilation and bronchodilation
what do alpha 1 receptors stimulate?
vascular receptors: vasoconstriction and increased blood pressure
what can result in cardiogenic shock?
cardiac tamponade due to pericardial effusion
ruptured chordae tendinae
severe arrhythmia
myocardial infarction
pulmonary thromboembolism
tension pneumothorax
what is gram positive shock like?
various bacterial toxins
when might you see bradycardia with neurogenic shock?
elevated intracranial pressure
what is the treatment of neurogenic shock?
oxygen
crystalloid fluid bolus
reduce anesthesia level
consider vasopressors early
how can you treat head trauma in neurogenic shock?
insure adequate blood pressure
surgical decompression if indicated
mannitol if not hypovolemic
diuretic is not hypovolemic
