Exam 2: Critical Care Flashcards
What defines hemodynamic instability in shock?
SBP< 90mmHg
MAP< 65 mmHg
What are signs of poor tissue perfusion/anaerobic metabolism?
Lactate > 4mmol/L
What characterizes shock?
Hypo-perfusion of tissues leading to anaerobic metabolism (impaired cellular metabolism). This will lead to inadequate tissue perfusion, cellular injury and dysfunction and ultimately multiple organ failure.
What happens with impaired oxygen utilization?
Anaerobic metabolism kicks in leading to
- ATP stores reduced and decreased Na/K ATPase Pump usage and decreased amplitude of action potential.
- Increased Na leading to hypovolemia (fluid entering cells due to higher Na levels), cellular edema and leaking lysosomal enzymes (damages the cells more)
- Decreased fluid in vascular system (hypovolemia) which will lead to decreased O2 delivery causing the activation of clotting cascade, ATN, ARDS, DIC.
- Anaerobic metabolism leads to metabolic acidosis/acidemia causing membrane disruption, enzyme disassociation and decreased O2 carrying capacity
Impaired Glucose Utilization
- Decreased delivery of glucose will increase cortisol, growth hormone and catecholamine release.
- Leads to hyperglycemia and insulin resistance.
- Glycogenolysis, gluconeogenesis and lipolysis cause high energy costs that contribute to cell failure.
What are the issues with gluconeogenesis in shock?
Protein is not longer available to maintain cell structure, function, repair, replication.
- Decreased albumin leads to reduced osmotic pressure
- decreased immunoglobulins = immunosuppression
- alanine release produces lactate
- byproducts of ammonia and urea
What happens to muscle tissue as a result of gluconeogenesis in shock?
Muscle wasting (diaphragm and cardiac muscle)
- respiratory dysfunction (decreased O2/CO2 exchange)
- Myocardial dysfunction (decreased glucose delivery)
- Decreased removal of waste products
What is shock driven by?
Reduced cardiac output, reduced systemic vascular resistance, or both
How do you determine blood pressure?
CO x SVR
How do you determine cardiac output?
SV x HR
What determines central venous pressure (Preload)?
Pressure of blood returning to the heart through the venous system
How do you determine mean arterial pressure (MAP)?
MAP = (1/3)SBP + (2/3)DBP
What does MAP represent?
Average of systolic and diastolic pressure in the arterial system, it is a surrogate marker of issue perfusion.
How do you calculate SVR?
80* (MAP-CVP)/CO
What does SVR represent?
the total resistance of the circulatory system (the amount or resistance the heart must overcome to create forward flow)
What are the types of shock?
Cardiogenic, Hypovolemic, Neurogenic, Anaphylactic (distributive), Septic (distributive), Sustained shock
What is the etiology of cardiogenic shock?
(Problem with the pump) Decompensated HF, MI, PAH, PE, valvular dysfunction, dysrhythmias, myocarditis
How do we treat cardiogenic shock?
Inotrope, vasopressor, cautious diuresis, correct underlying cause.
What compensatory mechanisms occur in cardiogenic shock?
Increases to SVR (e.g. vasoconstriction) resulting in further cardiac output.
How do you treat hypovolemic shock?
- Stop bleeding/fluid loss,
- give fluids (crystalloid or colloid
- Blood Products: whole blood, or packed red blood cells+ platelets + fresh frozen plasma) (if needed)
- Vasopressors (temporize)
Etiology: Neurogenic shock
Profound vasodilation and lack of compensatory tachycardia.
- too much parasympathetic activity leading to bradycardia.
- too little sympathetic stimulation of vascular smooth muscle leading to decreased SVR.
3: mostly caused by SCI: C-spine, high T-spine (T1-T6)
How do you treat neurogenic shock?
- Fluids
- Vasopressors (increase vascular tone)
- Inotropes (treat bradycardia)
- Stabilize spine if SCI
What is the etiology of anaphylactic shock?
Allergy leads to an immune/inflammatory response (IgE mediated), leads to vasodilation (decreased SVR) and vascular permeability (tissue edema/hypovolemia), extra-vascular smooth muscle constriction leading to bronchoconstriction/laryngospasm
How do you treat anaphylactic shock?
- Remove the antigen or anti-venom (if available)
- Glucocorticoids, antihistamines (blunt inflammatory response)
- Fluid resuscitation (correct hypovolemia)
- Epinephrine (vasoconstriction (alpha 1 agonist), bronchodilation (Beta 2 agonist))
What is the etiology of septic shock?
Bacteremia leading to endo/exo-toxins, lipopolysaccharide (LPS) gram negative, peptidoglycan and lipoteichoic acid gram positive.
How do you treat septic shock?
- Remove/suppress infection (ABX)
- Fluids
- Vasopressors
- Source control (I&D, remove infected heart valve, debridement/amputation)
- Renal replacement therapy, mechanical ventilation
What happens if a patient sustains shock for a long period of time?
Multi-organ dysfunction syndrome (MODS): progressive dysfunction of two or more organ systems resulting from uncontrolled inflammatory response to severe illness or injury
What are some common triggers that can lead to MODS?
- Severe trauma
- Major surgery
- Burns
- Shock
- Pancreatitis
- AKI
- ARDS
What are the three main types of shock?
Hypovolemic, cardiogenic, distributive
What is hypovolemic shock?
Decreased CO due to inadequate blood or plasma volume.
How is hypovolemic shock presented as?
Thirst, nausea, anxiousness, weakness, light headedness, dizziness, decrease UOP.
Severe: tachycardia, elevated RR, hypotension, altered mental status
What types of fluids are given in hypovolemic shock?
Crystalloids (NS, LR, D5W, and 3% NaCl), Colloids (Albumin), blood products
How is NS and LR distributed into the body?
100% ECF,
75% into the interstitial and 25% into the intravascular space.
How is D5W distributed into the body?
40% ECF and 60% ICF
75% into the interstitial and 25% into the intravascular space (break down of the ECF)
How is Albumin 5% distributed in the body?
100% ECF
100% interstitial
How is Albumin 25% distributed in the body?
100% ECF
500% intravascular (concentrated albumin will pull fluid into the intravascular space)
When would we use D5W in hypovolemia?
Dehydration with minor s/s of volume deplesion
When would we use 3% NS in hypovolemia?
In addition to LR/NS, for head trauma. Caution due to osmolarity, risk of cellular crenation and damage
Why would we use packed red blood cells in shock?
To increase oxygen carrying capacity in blood.
Why would we use fresh frozen plasma in shock?
To replace the clotting factors
Why would we use platelets in shock?
To administer for thrombocytopenia
How does Cardiogenic shock present?
altered mental status, pulmonary edema, hypotension, weak pulses, cool extremities, decreased urine output
How do we diagnose cardiogenic shock?
Sustained hypotension (SBP <90), reduced Cl (<2.2 l/min/m2) with an elevated PCWP > 18 (pulmonary capillary wedge pressure)
How do we generally treat cardiogenic shock?
Fluid resuscitation (unless frank pulmonary edema is present), furosemide for pulmonary edema, correct rhythm abnormalities (Mg/K), consider vasopressor therapy.
Avoid BB and CCB
How do we treat cardiogenic shock with STEMI pts?
PCI or CABG, fibrinolytic therapies for unstable patients, intra aortic balloon pump, alternative LV assist devices for circulatory support.
How is distributive shock defined as?
Excessive vasodilation resulting in impaired distribution of blood flow.
What is SIRS? What are the criteria?
Systemic Inflammatory response syndrome (SIRS), criteria (2 or more):
- Temperature of >38.3 or <36
- HR >90 bpm
- RR > 20 or mechanical vent
- WBC >12,000 or <4,000 or >10% immature forms (bands)
How do you determine qSOFA?
2 or more:
- RR >/= 22
- altered mentation
SBP = 100 mmHg
How should you initially resuscitate a sepsis induced hypoperfusion?
- Measure lactate (repeat if elevated (>2 mmol/L)
- Blood cultures and broad spectrum abx
- fluids for hypotension or lactate >4 mmol/L
- Vasopressors for MAP >/= 65 mmHg (to maintain 65 mmHg or greater)
At what rate and what types of fluids should a septic patient receive?
Crystalloids are preferred, 30 mL/kg
Albumin may be used for pts with substantial requirements of crystalloids after initial resuscitation.
CVP is used for fluid status (goal 8-12 mmHg or 12-15 if mechanically ventilated)
What is the target goal for vasopressor therapy in shock?
MAP >/= 65
Norepinephrine:
Dose:
Rate:
Dose: 0.02-3 ug/kg/min
Rate: 4-30 ug/min
Why is norepinephrine considered first line therapy?
Increases MAP/SVR via vasoconstriction and causes little change in heart rate and stroke volume, may be a little more effective at reversing hypotension than dopamine
Vasopressin
Rate:
0.04 units/min, can do 0.03 units/min to NE to raise MAP or decrease NE
>0.03-0.04 units/min is considered salvage therapy.
What are some considerations to think about with vasopressin?
increases BP in pts refractory to other vasopressors, antidiuretic properties via V2 receptors, may increase serum cortisol via V3 receptors (proinflammatory and increases BP), higher doses associated with cardiac, digital and splanchnic ischemia
Epinephrine
Dose:
Rate:
Dose: 0.01-0.5 mcg/kg/min
Rate: 2-10 mcg/min
What’s epinephrine’s role in therapy?
Either added to possibly substituted for NE
What are some considerations to think about with epinephrine?
Decreases renal and splanchnic blood flow, increases lactate levels via stimulation of skeletal B2 receptors
Phenylephrine
Dose:
Rate:
Dose: 0.5-9 mcg/kg/min
Rate: 40-300 mcg/min
Why would you use phenylephrine?
Not normally recommended.
Only use if NE is associated with serious arrhythmias
High CO and persistently low BP
Salvage therapy
What are some considerations if thinking about using phenylephrine?
It’s purely an alpha activator and the least likely drug to cause tachycardia.
May decrease stroke volume (limited use)
Dopamine
Rate:
- 1-3 mcg/kg/min
- 3-10 mcg/kg/min
- 10-20 mcg/kg/min
What’s dopamine’s role in shock?
It is an alternate to NE when there is a low risk of tachyarrhythmias and absolute or relative bradycardia.
- Do not use low doses for renal perfusion
What are some considerations when thinking of using dopamine?
- increases MAP and CO due to increase in stroke volume and HR.
- may be useful with compromised systolic function, but causes more tachycardia and may be more arrhythmogenic than NE
- Influences endocrine response via hypothalamic pituitary axis and has immunosuppressive effects
When can you use dobutamine?
myocardial dysfunction as suggested by elevated cardiac filling pressures and low CO. Ongoing signs of hypoperfusion despite adequate intravascular volume and adequate MAP
When should you use hydrocortisone therapy?
Hemodynamic instability despite fluid resuscitation and vasopressor therapy.