Shock Flashcards
shock
inadequate cellular energy production
occurs when oxygen delivery does not equal oxygen consumption
three mechanisms of shock
- inadequate blood flow to cells
- lack of substrate
- cellular dysfunction
types of shock - inadequate blood flow to cells
most common
diagnosed by PERFUSION PARAMETERS
- vasoconstrictive - hypovolemic, obstructive, cardiogenic
- vasodilatory - distributive
types of shock - lack of substrate & cellular dysfunction
less common
diagnosed by LAB VALUES
- metabolic shock - hypoglycemia, hypoxemic, cytopathic
perfusion parameters
- mentation
- MM color
- CRT
- HR
- pulse quality
- extremity temperature
vasoconstrictive shock - PP
- obtunded mentation
- pale MM
- slow CRT (>2s)
- tachycardia (dogs), bradycardia (cats)
- poor pulse quality
- cold extremities
types of vasoconstrictive shock
- hypovolemic
- obstructive
- cardiogenic
hypovolemic shock
decreased circulating volume
causes dec. preload –> dec. stroke volume + cardiac output –> dec. O2 delivery and BP
causes of hypovolemic shock
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
obstructive shock
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
causes of obstructive shock
- pericardial effusion
- GDV
- space occupying lesions
cardiogenic shock
heart disease leading to inadequate circulation
dec. preload and contractility w/ inc. afterload –> dec. SV and HR –> dec. CO –> dec. O2 delivery
causes of cardiogenic shock
primary heart disease:
1. altered HR: tachy/bradycardia and tachy/bradyarrhythmias
2. decreased preload: degenerative mitral valve disease
3. decreased contractility: DCM, HCM
how to differentiate a hypovolemic or obstructive shock from cardiogenic shock
- history: hx of fluid loss (hemorrhage, vomiting, diarrhea) vs hx of heart disease
- signalment: breed predispositions for heart disease
- PE: heart murmurs, arrhythmias, venous distension, dyspnea, cyanosis, pulmonary crackles
- additional tests: ECG, POCUS, troponin, NT-proBNP
how does treatment of cardiogenic shock differ from other vasoconstrictive shocks
do NOT use IV fluid resuscitation in patients with heart disease
exception: pericardial effusion because it is obstructive shock not cardiogenic
vasodilatory shock - PP
- obtunded mentation
- hyperemic MM
- rapid CRT (<1s)
- tachycardia
- bounding pulses
- warm extremities
distributive shock
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
causes of distributive shock
- inflammatory mediators
- sepsis/SIRS
- anaphylactic reactions
hypoglycemic and hypoxemic shock
substrates are unavailable leading to inadequate cellular energy production
dec. Hb/SaO2/PaO2 –> dec. CaO2 –> dec. O2 delivery
causes of hypoglycemia/hypoxemic shock
- severe hypoglycemia (neonates, sepsis)
- hypoxemia (anemia, dyshemoglobinemia, lung disease)
cytopathic shock
substrates available but cells unable to use it
caused by uncoupling of oxidative phosphorylation
shock treatment plan
- O2 supplementation
- IV fluid therapy
- active warming (cats only)
goal of IV fluid therapy
increase preload
use a large bore and short IVC for fluid bolus administration
reassess every 5-10 minutes
why do cats need to be actively warmed during fluid resuscitation
cats will appear vasoconstricted if hypothermic - can obscure resuscitation status and lead to overestimation of fluid requirements
types of fluids
- isotonic crystalloids - LRS, plasmalyte, 0.9% saline, normosol
- hypertonic saline
- hypotonic - D5W, sterile water, hypotonic saline
- colloids - synthetic, natural
shock doses - isotonic crystalloids
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
indications - hypertonic saline
- head trauma w/ concurrent shock
- giant breeds (low volume resuscitation)
- 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
shock dose - hypertonic saline
dogs: 4-6 mL/kg IV
cats: 2-3 mL/kg IV
rate: 5 minutes
are hypotonic solutions ever used for shock resuscitation
NO - will not stay in the IV space
causes hyponatremia –> cerebral edema
indications - colloids
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
contraindications - colloids
synthetic: may cause coagulopathies and AKI
natural: can get transfusion reactions
shock dose - colloids
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
resuscitation endpoints
- normalization of perfusion parameters
- improved BP
- normal lactate
- increased venous O2
- normal urine output
general fluid dosing guidelines - isotonic
dogs: 100 mg/kg
cats: 50 mg/kg
general fluid dosing guidelines - synthetic colloids
dogs: 20 mL/kg
cats: 10 mL/kg
general fluid dosing guidelines - hypertonic saline
dogs: 5 mL/kg
cats: 2.5 mL/kg
