Case 1

65 year old female nursing home

resident with a hx CAD, PUD, recent hip

fracture

Transferred to ED with decreased

mental status

BP in ED 80/50

Case 1

65 year old female nursing home

resident with a hx CAD, PUD, recent hip

fracture

Transferred to ED with decreased

mental status

BP in ED 80/50

This case demonstrates some common risk factors for causes of shock

(ACS from CAD?, bleeding from a peptic ulcer?, PE from immobility?)

and common manifestations of shock (altered mental status, hypotension)

Shock

• Definition

• Physiology of shock

• Types of shock

• Stages of shock

• Clinical presentation of shock

• A bit on vasopressors, inotropes

Definition

Inadequate perfusion of tissues which is

insufficient to meet cellular metabolic

needs

There is no set blood pressure, cardiac

output, CVP, urine output, or etc that

defines shock.

Mechanisms of Hypotension

MAP – mean arterial pressure

Cardiac Output

Stroke Volume

Preload Contractility

SVR

Heart Rate

Dr. Kreit circa 2010

Mechanisms of Hypotension

Hypotension

Cardiac Output

Stroke Volume

Preload Contractility

SVR

Heart Rate

Dr. Kreit circa 2010

Compensatory Mechanisms that

maintain MAPLV Preload

Stroke Volume

Cardiac Output

Arterial Pressure

Baroreceptors Sympathetic activity

Heart Rate Contractility

+

+

Arterial constriction

Venous constriction

+

SVR+

Adapted from Dr. Kreit circa 2010

Renin

Angiotensin II

Aldosterone

VasopressinNa and H2O

Retention

+

+

+

Systemic O2 Delivery

• Regulation of O2 delivery (DO2)

– Normally, via cardiac output (CO) and tissue

extraction

– There is no “normal” cardiac output

– Only adequate or inadequate cardiac output

for given metabolic conditions

Pinsky Chest 2007; 132: 2020

http://www.ncbi.nlm.nih.gov/pubmed/18079239

Shock Physiology

• Imbalance of O2 delivery and

consumption

• Shock results in inadequate O2 delivery

– Cellular hypoxia → anaerobic metabolism

– ↓ ATP generation

– ↓ ion pumps, membrane function

• Initially, damage is reversible →

eventually there is irreversible injury

– Cell death, organ failure, MOSF, death

Types of Shock

• 4 major categories – Hinshaw and Cox

• “Volume, pump, container”

– Hypovolemic- volume

• Fluid losses (fistulas, burns), hemorrhage

– Cardiogenic- pump

• Myopathic, arrhythmic, mechanical, thyroid

– Distributive- container

• Sepsis/SIRS, anaphylaxis, neurogenic, adrenal

• Obstructive

• PE, Aortic stenosis, tamponade, tension pneumo

Types of Shock

Shock Type COCardiac output

PCWPpulmonary capillary

wedge pressure

SVRsystemic vascular

resistance

Hypovolemic ↓ ↓ ↑

Cardiogenic ↓ ↑ ↑

Obstructive ↓ NL or ↑ ↑

Distributive ↑ ↓ or NL ↓

Septic shock

SIRS HR, WBC (↑,↓), RR (PaCO2), Temp (↑,↓)

Sepsis SIRS with culture+ infection or identified infection

Severe Sepsis Sepsis with organ hypoperfusion or dysfunction

Septic Shock Severe sepsis with hypotension after volume

Refractory Septic Shock Shock requiring high dose pressors after

resuscitation

Stages of Shock

• Pre-shock (“compensated shock”)– Homeostatic mechanisms are sufficient

– You may see:

– ↑ HR

– peripheral vasoconstriction

– BP remains nearly normal

• Shock– Homeostatic mechanisms are overwhelmed

– Organ dysfunction first appears

• End organ dysfunction

Case 2

You are call by a nurse:

“Mrs. Jones is hypotensive”

Step #1 – ?

Case 2

You are call by a nurse:

“Mrs. Jones is hypotensive”

Step #1 – Go See Patient –

Assess and Treat simultaneously

○ ABCs

IV access, crystalloid volume early

Pulse ox, UOP, central venous and arterial lines

○ H&P clues

Comorbidities, localizing sxs, etc.

Bleeding, cardiac exam, JVP, infection, etc

Clinical Presentation of Shock

• Signs and symptoms

– Anxiousness, altered mental status

– Tachycardia, tachypnea

– Cool extremities (±in early distributive shock)

– Weak pulses

– ↓ urine output, acidemia (lactate)

– eventually you will see ↓SBP (a late sign)

Shock Management

• Improve DO2 to “adequate level”

– There are no static values

– It requires a knowledge of CO, vascular tone

– Are they fluid (pre-load) responsive?

– Can assess with:

• Traditional parameters/methods:

• CVP/Fluid challenge) - not always reliable

• Pulse Pressure Variation, Passive leg raising

– If pre-load optimized → is CO adequate?

• Assess SvO2 for tissue oxygenation

Early Goal Directed

Therapy

“Functional Hemodynamic

Monitoring”

- early aggressive

resuscitation

- end point of improved

tissue oxygenation

- multicenter trials

ongoing

Rivers et al. NEJM 2001; 345:1368

http://www.ncbi.nlm.nih.gov/pubmed/11794169

A bit on vasopressors and

inotropes:

Adrenergic receptors

ADRENOCEPTORS

α1

- Vasoconstriction

- Increased peripheral resistance

- Increased blood pressure

α2

- Inhibition of norepinephrinerelease

β1

- Tachycardia

- Increased myocardial contractility

β2

- Vasodilation

- Decreased peripheral resistance

- Bronchodialation

Vasopressor parmacology

α1 β1 β2 DA MAP PCWP CO SVR HR

Dopamine

10 mcg/kg/min +++ ++++ + 0 ↑↑ ↑ ↑ ↑ ↑↑

Norepinephrine

0.01-3 mcg/kg/min +++++ ++ 0 0 ↑↑↑ ↑↑ ↑↓ ↑↑↑ ↑↑

Phenylephrine

0.5-9 mcg/kg/min +++++ 0 0 0 ↑ ↑ ↑↓ ↑ NA

Vasopressin

Inotrope pharmacology

α1 β1 β2 MAP PAP CO SVR HR MOC

Dopamine

3-10 mcg/kg/min 0/+ ++++ ++ ↑ ↔↑ ↑ ↔↓ ↑ ↑

>10 mcg/kg/min +++ ++++ + ↑↑ ↑ ↑ ↑ ↑↑ ↑

Dobutamine

2-20 mcg/kg/min + ++++ +++ ↓ ↓ ↑↑ ↓ ↑↑ ↑

Epinephrine

0.01-0.1 mcg/kg/min +++++ ++++ +++ ↑↑ ↑↑ ↑↑ ↑ ↑↑ ↑

Milrinone

0.125-0.75 mcg/kg/min

PDE-3 inhibitor ↓↓ ↓↓ ↑↑ ↓↓ ↑ ↔↑

Circulation 2008;118:1047-56

Crit Care Med 2008;36:S106-11

MOC; myocardial oxygen consumption

What pressor to chose?

De Backer D. NEJM 2010

http://www.ncbi.nlm.nih.gov/pubmed/20200382

More adverse events with

dopamine

De Backer D. NEJM 2010

http://www.ncbi.nlm.nih.gov/pubmed/20200382

Vasopressors and Inotropes

• Clinical considerations with pressors

– Ensure fluid replete

– Treating people with pressors who are

hypovolemic can cause digital and organ

ischemia

– pH ≥ 7.0 to 7.1

– Pressor-receptor interaction is poor with

acidosis. May need to give buffer to get pH

up.

– Central line preferable

Take Home Messages

Shock = inadequate tissue oxygen delivery

Cardiogenic, hypovolemic, distributive, obstructive

Treat patient at the bedside

Treat underlying cause, make sure volume replete, and use pressorsjudiciously