Shock

Question 1

shock

Answer 1

inadequate cellular energy production

occurs when oxygen delivery does not equal oxygen consumption

Question 2

three mechanisms of shock

Answer 2

1. inadequate blood flow to cells
2. lack of substrate
3. cellular dysfunction

Question 3

types of shock - inadequate blood flow to cells

Answer 3

most common
diagnosed by PERFUSION PARAMETERS

1. vasoconstrictive - hypovolemic, obstructive, cardiogenic
2. vasodilatory - distributive

Question 4

types of shock - lack of substrate & cellular dysfunction

Answer 4

less common
diagnosed by LAB VALUES

1. metabolic shock - hypoglycemia, hypoxemic, cytopathic

Question 5

perfusion parameters

Answer 5

1. mentation
2. MM color
3. CRT
4. HR
5. pulse quality
6. extremity temperature

Question 6

vasoconstrictive shock - PP

Answer 6

1. obtunded mentation
2. pale MM
3. slow CRT (>2s)
4. tachycardia (dogs), bradycardia (cats)
5. poor pulse quality
6. cold extremities

Question 7

types of vasoconstrictive shock

Answer 7

1. hypovolemic
2. obstructive
3. cardiogenic

Question 8

hypovolemic shock

Answer 8

decreased circulating volume

causes dec. preload –> dec. stroke volume + cardiac output –> dec. O2 delivery and BP

Question 9

causes of hypovolemic shock

Answer 9

intravascular volume loss
1. whole blood: hemorrhage (internal or external)
2. plasma loss: GI loss of plasma proteins
3. isotonic loss: GI (vomiting, diarrhea), renal, burns, third space loss

Question 10

obstructive shock

Answer 10

relative hypovolemia
normal blood volume but not enough is returning to the heart

causes dec. preload –> dec. SV and CO –> dec. O2 delivery and BP

**dec. preload caused by obstruction of blood flow back to heart NOT by low volume

Question 11

causes of obstructive shock

Answer 11

1. pericardial effusion
2. GDV
3. space occupying lesions

Question 12

cardiogenic shock

Answer 12

heart disease leading to inadequate circulation

dec. preload and contractility w/ inc. afterload –> dec. SV and HR –> dec. CO –> dec. O2 delivery

Question 13

causes of cardiogenic shock

Answer 13

primary heart disease:
1. altered HR: tachy/bradycardia and tachy/bradyarrhythmias
2. decreased preload: degenerative mitral valve disease
3. decreased contractility: DCM, HCM

Question 14

how to differentiate a hypovolemic or obstructive shock from cardiogenic shock

Answer 14

1. history: hx of fluid loss (hemorrhage, vomiting, diarrhea) vs hx of heart disease
2. signalment: breed predispositions for heart disease
3. PE: heart murmurs, arrhythmias, venous distension, dyspnea, cyanosis, pulmonary crackles
4. additional tests: ECG, POCUS, troponin, NT-proBNP

Question 15

how does treatment of cardiogenic shock differ from other vasoconstrictive shocks

Answer 15

do NOT use IV fluid resuscitation in patients with heart disease

exception: pericardial effusion because it is obstructive shock not cardiogenic

Question 16

vasodilatory shock - PP

Answer 16

1. obtunded mentation
2. hyperemic MM
3. rapid CRT (<1s)
4. tachycardia
5. bounding pulses
6. warm extremities

Question 17

distributive shock

Answer 17

decreased systemic vascular resistance

dec. SVR –> dec. venous return –> dec. CO –> dec. O2 delivery

over time - inflammatory mediators can increase vascular permeability leading to decreased preload

Question 18

causes of distributive shock

Answer 18

1. inflammatory mediators
2. sepsis/SIRS
3. anaphylactic reactions

Question 19

hypoglycemic and hypoxemic shock

Answer 19

substrates are unavailable leading to inadequate cellular energy production

dec. Hb/SaO2/PaO2 –> dec. CaO2 –> dec. O2 delivery

Question 20

causes of hypoglycemia/hypoxemic shock

Answer 20

1. severe hypoglycemia (neonates, sepsis)
2. hypoxemia (anemia, dyshemoglobinemia, lung disease)

Question 21

cytopathic shock

Answer 21

substrates available but cells unable to use it

caused by uncoupling of oxidative phosphorylation

Question 22

shock treatment plan

Answer 22

1. O2 supplementation
2. IV fluid therapy
3. active warming (cats only)

Question 23

goal of IV fluid therapy

Answer 23

increase preload

use a large bore and short IVC for fluid bolus administration

reassess every 5-10 minutes

Question 24

why do cats need to be actively warmed during fluid resuscitation

Answer 24

cats will appear vasoconstricted if hypothermic - can obscure resuscitation status and lead to overestimation of fluid requirements

Question 25

types of fluids

Answer 25

1. isotonic crystalloids - LRS, plasmalyte, 0.9% saline, normosol 2. hypertonic saline 3. hypotonic - D5W, sterile water, hypotonic saline 4. colloids - synthetic, natural

Question 26

shock doses - isotonic crystalloids

Answer 26

dogs: 80-90 mL/kg IV cats: 40-50 mL/kg IV if mild shock: give 1/4 shock dose over 10 min then reassess if severe shock: give 1/2 shock dose over 5 min then reassess; anticipate needing full dose

Question 27

indications - hypertonic saline

Answer 27

1. head trauma w/ concurrent shock 2. giant breeds (low volume resuscitation) 3. active hemorrhage small volume required - good for administration but only increases blood volume by small amount - MUST follow up with isotonic crystalloids to restore blood volume

Question 28

shock dose - hypertonic saline

Answer 28

dogs: 4-6 mL/kg IV cats: 2-3 mL/kg IV rate: 5 minutes

Question 29

are hypotonic solutions ever used for shock resuscitation

Answer 29

NO - will not stay in the IV space causes hyponatremia --> cerebral edema

Question 30

indications - colloids

Answer 30

synthetic: high molecular weight so will stay in the IV space longer and draw water into IV space without fluid redistribution into interstitium natural: hypovolemia + coagulopathies

Question 31

contraindications - colloids

Answer 31

synthetic: may cause coagulopathies and AKI natural: can get transfusion reactions

Question 32

shock dose - colloids

Answer 32

synthetic: - dogs: 10-20 mL/kg IV - cats: 5-10 mL/kg IV - rate: 5-15 min natural: 10-20 mg/kg IV - want fresh frozen plasma over whole blood

Question 33

resuscitation endpoints

Answer 33

1. normalization of perfusion parameters 2. improved BP 3. normal lactate 4. increased venous O2 5. normal urine output

Question 34

general fluid dosing guidelines - isotonic

Answer 34

dogs: 100 mg/kg cats: 50 mg/kg

Question 35

general fluid dosing guidelines - synthetic colloids

Answer 35

dogs: 20 mL/kg cats: 10 mL/kg

Question 36

general fluid dosing guidelines - hypertonic saline

Answer 36

dogs: 5 mL/kg cats: 2.5 mL/kg