Exam 1: Physiology, Mechanisms, Recognition of Shock

what is the core definition of shock

an imabalnce between oxygen supply and demand leading to inadequate cellular energy production, cellular death, and multiorgan dysfunction

what is the key component to cellular energetics

O2 → used in cellular respiration

what are the steps of oxygen delivery through cardiac output

stroke volume (preload, afterload, contractlity), heart rate

what is the common demoninator for blood pressure and tissue perfusion

cardiac output = major target for compensatory systems and clinical intervention

generally describe anaerobic metabolism

an inefficient way to produce ATP without oxygen, produces lactic acid or lactate

what are the cellular effects of energetic disruption

• energy based processes are impaired or stopped

• homeostasis disrupted

• cellular damage

• cell death

what are the goals of compensatory mechanisms of shock

maintain O2 delivery and cellular energetics

what are the physiologic options to compensate for shock

• increase cardiac output and perfusion

• increase oxygen extraction

• anaerobic metabolism

what are the three predominant mechanisms for compensating for shock

• sympathetic nervous system

• renin-angiotensin-aldosterone system

• antidiuretic hormone (vasopressin)

what are the immediate cmpensatory effects

• occur within minutes

• increase sympathetic tone and relase catecholamines (Epi/Nor)

what are the net effects of immediate compensatory effects

• parasympathetic inhibition

• increased CO

• increased vascular resistance

• greatest benefit to patient acutely

what are the intermediate compensatory effects

• occur within one hour

• RAAS and vasopressin causing vascular constrictin

what are the delayed compensatory effects

• occurs after 1 hour and up to 48hrs

• RAAS-aldosterone and vasopressin for fluid conservation

• marginal utility to the pt acutely

what is the compensatory reserve?

• body’s ability to maintain normal function despite physiologic stress, aka how much gas in the tank?

what are the phases of shock

• compensatory

• decompensatory

• refractory aka late decompensatory

what is the compensatory phase

• oxygen delivery to tissues adequately preserved

• normal cellular metabolism and function maintained, but the body is working harder to do it

what is the decompensatory phase

• compensatory systems no longer adequate

• oxygen delivery fails to meet demands

• anaerobic metabolism increasing

• reversible cellular damage

what is the refractory phase

• energy deficient state prolonged

• cellular damage widespread and irreversible

• persistent multiorgan dysfunction expected

  • arrest is imminent

how do the mechanisms of shock occur

• reduced O2 delivery

• increased O2 consumption

• aberrant O2 utilization

what are the functional classifications of shock

• hypovolemic

• obstructive

• disruptive

• cardiogenic

• hypoxic

• metabolic

describe hypovolemic shock

• decreased blood volume caused by less volume/beat, lower CO, low blood pressure

• O2 delivery problem, perfusion dependent

• most common class

list examples of hypovolemic shock

• trauma or hemorrhage

• high fluid losses

• severe dehydration

describe obstructive shock

• physical impediment to blood flow returning from large veins

• trapping of blood causes less return and lowers pump volume

• O2 delivery problem, perfusion dependent

what are common examples of obstructive shock

• pericardial effusion

• GDV

• large vessel thrombosis

define distributive shock

• vascular changes (dilation and or permeability) causing vascular volume to distrubute abnormally

• loss of venous return pressure, less blood return to heart, less volume pumping

• O2 delivery problem, perfusion dependent

? may occur as a secondary component to distributive shock

hypovolemia

what are common examples of distributive shock

• sepsis/sirs

• anaphylaxis

define cardiogenic shock

• heart function impaired leading to less blood being pumped per beat = decreased cardiac output

• may be due to systolic function problem, diastolic function problem, rate dependent problem

what are examples of cardiogenic shock

• cardiomyopathy/heart failure

• severe tachyarrhythmias (V-tach, SVT)

• severe bradyarrhythmias (3rd degree AV blocks)

define hypoxic shock

• decreased arterial O2 problem, NOT perfusion dependent

• may be due to altered transport capacity or oxygen diffusion problems

why are examples of hypoxic shock

• anemia/methemoglobinemia - decreased or altered transport

• pneumonia, pulmonary edema- diffusion problems

• asthma, brachycephalic syndrome- low intake

what is metabolic shock

• disrupted use of O2 usage at the mitochondria

• not perfusion dependent

• possible mechanisms include mitochondrial damage, uncoupling of Oxphos, lack of metabolites/substrates

what are examples of metabolic shock

• ischemic event, sepsis- mitochondria damage

• toxins such as cyanide and bromethalin- uncoupling

• hypoglycemia- lack of metabolites

how is oxygenation assessed

• RR and effort

• mucous membrane color

• oxygen saturation

• ± arterial O2 content

how do you assess O2 carrying capacity

PCV/Hct

how do you assess perfusion

• heart rate

• pulse quality

• MM color, CRT

• temperature

• mentation

• blood pressure

• blood lactate

what terms are used for vascular color

• pallor

• hyperemic or injected

what terms are used for mucous membrane pigment

• pallor

• cyanosis

• icterus

what is included n QATs

• packed cell volume

• glucose

• lactate

describe perfusion parameters for compensatory shock

• T= normal

• HR= tachycardia

• Pulse= bounding

• Mentation = QAR

• MM color = hyperemic

• CRt <1sec

• mean BP = normal

• urine output = normal

What are the perfusion parameters of decompensatory shock

• T= decreased

• HR= tachycardia

• Pulse= weak

• Mentation = obtunded

• MM color = pale

• CRt >2sec

• mean BP = hypotension

• urine output = decreased

describe perfusion parameters for refractory shock

• T= decreased

• HR= tachycardia → bradycardia

• Pulse= weak

• Mentation = obtunded → stupor

• MM color = pale to muddy grey

• CRt >3-4

• mean BP = hypotension

• urine output = decreased

what are findings of shock influenced by

• stage of shock

• compensatory mechanisms

• type of shock

• patient factors

what is the formula for shock index

• heart rate / systolic blood pressure

• aids in discriminating stable sympathetic response vs compensatory shock response

• for use in ADULT DOGS ONLY

what is a normal shock index

1.0 ± 0.2

adult dog with a HR 160 annd BP 160. determine the SI and source

160/160= 1, anxiety and stress

adult dog with HR 160 and BP 100, determine SI and source

160/100 = 1.6, compensatory shock

how is shock generally described in cats

• shock organ is the lungs, so will exhibit respiratory signs even with no dx

• may be tachy or brady

• uncommonly exhibit compensatory changes

what is the cat shock trifecta

• hypothermia

• hypotension

• bradycardia

• a sick cat that is bradycardic = bad