23 - Shock

MAP equals what, and what does that mean?

MAP equals CO x TPR and it means pressure difference of blood leaving the heart vs when it returns(MAP - CVP, but CVP is so low it’s dropped) is equal to cardiac output and systemic vascular resistance

What is a more detailed way to say MAP = CO x TPR?

We say SV x HR x TPR, because CO is SV x HR

What is a more detailed way to say MAP = SV x HR x TPR?

We say (EDV-ESV) x HR x TPR

EF =

EDV - ESV/EDV

What does EDV x EF x HR x TPR mean?

It is an equation that represents MAP via 4 important factors

• EDV: Preload

• EF: Contractility

• HR: Rate/rhythm

• TPR: Afterload

O2 delivery equation

• What is it?

• Importance

((1.34 x Hb x O2_sat) + (0.003 x PaO2)) x CO

• It is important because it multiplies cardiac output with how much O2 is in each unit of blood and sees how good we’re delivering O2 to tissues

Lactate of ___ is a sign of ___

Of < 2 mmol/L is a sign of tissue hypoxia

Types of shock and their basic classification

• Low CO shock: Hypovolemic, cardiogenic, obstructive shock

• High CO shock: Distributive shock

Most common type of shock

Septic shock, a distributive shock

How do we tell, simply, what kind of shock a patient has?

If the patient has increased CO, they have distributive shock. If not, we look at their JVP

• If their JVP is decreased, it’s hypovolemic shock or a distributive shock we weren’t able to classify from their first step

• If their JVP is increased, it can be obstructive or cardiogenic

  • Associate obstructive with clear breath sounds, and cardiogenic with crepitations

Hypovolemic shock simple cause

Loss of plasma or blood volume

Hypovolemic shock

• JVP

• Lung sounds

• S3

• HR

• Pulse pressure

• Capillary refill

• JVP:Low because there’s little blood in system to back up into central veins

• Lung sounds: Low because there’s little blood to back up into lungs

• S3: Found in high volume, not low

• HR: High due to compensation

• Pulse pressure: Less blood causes lower SBP, increased sympathetic stimulation to keep MAP high increases DBP = narrow pulse pressure

• Capillary refill: Slow because less blood flow

How do we tell if pulse pressure is wide?

More than 50% of SBP

Types of hypovolemic shock

Hemorrhagic shock vs non-hemorrhagic

How is hemorrhagic shock classified?

1. ATLS system: Classes I-IV, with IV being the worst(expect anuria, lethargic mental status, BP very low, etc.) and I being different from II because pulse pressure gets narrow, and II and III are different because we start to see a decreased systolic BP in class III

2. Current markers, since patients don’t always fall into one class

   1. Mental status

   2. Shock index over 0.9 is BAD

   3. Base excess(under -2 mmol/L, showing that there’s too little base due to increased acid) and lactate

   4. Response to treatment(Transient and non-responders are bad)

   5. Evidence of on going bleeding

Shock index calculation

HR/SBP, should be below 0.9

Explain the lethal diamond of hemorrhagic shock

1. Acidosis: Less O2 reaches tissues → lactic acid forms from anaerobic met. → pH affects cell function

2. Hypothermia: Poorly perfused tissues burn less fuel, pt. may be given cold blood/fluids and this affects clotting enzymes → bleeding

3. Coagulopathy → Wound(likely bc there’s hemorrhage) uses up platelets, then the lost clotting factors and body’s inflammatory response switches off clotting

4. HypoCa2+: Vasoconstriction uses up all the Ca2+ and that can affect clotting and the heart

Cardiogenic shock simple cause

Ventricular failure, usually the left side

Cardiogenic shock

• JVP

• Lung sounds

• S3

• HR

• Pulse pressure

• Capillary refill

• JVP: High because backup of fluid

• Lung sounds: Crepitations if left-sided, clear if right-sided

• S3: The ventricles are already full since we couldn’t pump everything out, so in the next filling, blood slaps against the wall

• HR: High due to compensation, unless the pt. has a heart block, often due to infarction of AV node

• Pulse pressure: Weaker pump, raised TPR = narrow, except bradycardia because fuller heart leads to more stroke volume being pumped out so SBP is higher

• Capillary refill: Delayed because less blood gets out

Main myocardial(and other causes) vs mechanical cause of cardiogenic causes are…?

Acute coronary syndrome(then think of myocarditis, cardiomyopathies) and valvular heart disease

Why does distributive shock happen?

Vasodilation(or venodilation)

Distributive shock

• JVP

• Lung sounds

• S3

• HR

• Pulse pressure

• Capillary refill

• JVP: Blood pools so it can’t return to heart

• Lung sounds: Less preload, so no backup to lungs

• S3: No high amnt of fluid ino ventricle

• HR: High unless there’s a neurogenic shock

• Pulse pressure: Normal or wide because diastolic pressure drops a lot

• Capillary refill: Due to dilation and leakiness of vessels, blood refills into tissues easily

Main cause of distributive shock

Septic shock

Sepsis vs septic shock

Infection + at least 2 SIRS criteria vs sepsis with hypotension despite adequate fluid loading(vasoplegia)

SIRS

• Temp: >38, <36

• HR: >90

• RR: >20 or PaCO2 <32 mmHg

• WBCs >12k or <4k or band form 10%

Septic shock is mainly distributive shock, but…

1. If there is leaky vessels, it can also be hypovolemic

2. If there is inflammation of the heart muscle and contraction gets impaired, it can also be cardiogenic

Diastolic shock index

• What is it?

• Value needed to give NE

• HR/DBP

• >3

Why can these conditions cause distributive shock?

1. Acute pancreatitis

2. Anaphylaxis

3. Adrenal crisis

4. Neurogenic shock

5. Drugs/toxins

6. Liver failure

1. Acute pancreatitis: Enzymes and inflammatory chemicals are released into the blood which damages endothelium

2. Anaphylaxis: Histamine release dilates/leaks vessels

3. Adrenal crisis: Cortisol insufficiency leads to vessels being unable to respond to symp. tone + hypovolemic component from aldos.

4. Neurogenic shock: Spinal cord injuries above the lateral horn(T1-L2) lead to us being unable to send sympathetic supply to the body

5. Drugs/toxins: Drugs like ACE/ARB can cause too much vasodilation

6. Liver failure: Excess arginine becomes NO, which is a strong vasodilator

Why does obstructive shock happen?

Something physically blocks blood flow, typically something obstructing the RVOT

Obstructive shock

• JVP

• Lung sounds

• S3

• HR

• Pulse pressure

• Capillary refill

• JVP: Due to blood backup from RV to neck veins

• Lung sounds: Before the lungs, so lungs are fine

• S3: Underfilled LV

• HR: Compensation

• Pulse pressure: Narrow bc raised DBP and less stroke volume due to less blood available for LV

• Capillary refill: Decreased bc less blood pumped out

Obstructive shock causes

1. Tension pneumothorax/massive hemothorax

2. Cardiac tamponade

3. Pulmonary embolism

4. Superior vena cava syndrome

Tension pneumothorax

• Trachea

• Chest movements

• Percussion

• Breath sounds

• Tactile fremitus/vocal resonance

• Trachea: Away from affected lung

• Chest movements: Decreased

• Percussion: Hyperresonance

• Breath sounds: Decreased

• Tactile fremitus/vocal resonance: Decreased bc there’s an extra air layer making the lung not touch the chest wall

Difference in initial fluid treatment of cardiogenic shock that’s from an RV infarction vs non-RV infarction

• In RV infarction, we give fluid before vasopressors/inotropes because the damaged heart can still pump

  • On the other hand, if it was LV, patient’s are already congested

Dopamine use case

Shock with bradycardia

Avoid dobutamine when…

The patient already has low BP, unless we know that the dobutamine can bind beta 1 so good that it overrides dobutamine’s beta 2 vasodilation effect

Main vasopressor in shock, and what are it’s use cases

Norepinephrine

• Distributive shock except anaphylaxis, cardiogenic shock, obstructive shock

NE effect and ADR to be aware of

80% alpha 1 vasoconstriction → beware PAD patients

20% beta 1 inotrope and chronotrope

Cardiogenic shock treatment approach

1. Very slow HR: Atropine, dopamine

2. Very fast: Cardioversion

3. Normal: Fluid then NE if RV infarction, or else NE

Dobutamine vs milrinone

• Class

• ADR difference

• Inodilators

• Dobutamine can cause tachyarrhythmias

Septic shock antibiotic in…

• Community acquired

  • Pneumonia

  • UTI

  • Unknown

• Within 90 days of hospital visit and no clear cause

• Community acquired

  • Pneumonia: Ceftriaxone + azithro.

  • UTI: Ceftriaxone

  • Unknown: Ceftriaxone

• Within 90 days of hospital visit and no clear cause: Piperacillin-tazobactam, ceftazidime + meropenem

Main treatment of most shocks

Fluid, specifically RLS or acetar, but not in LV cardiogenic shock