---
tags: tier1, OME, PGY1
---
# Shock
> [Tier 1 knowledge topics](/AoUNT7MtS3iso3e6iPOy9g)

Shock is defined as a state of tissue hypoxia due to decreased or dysregulated oxygen delivery or extraction resulting in end-organ damage.
- **Hypotension** (SBP < 90mmHg, MAP <70mmHg)
- hypoperfusion s/sx
- **Tachycardia**
- cool and clammy skin versus warm and flushed
- low urine output (<0.5 mL/kg/hr)
- altered mental status
- **Elevated Lactate** (>2 mmol/L)

## Hypotension
Blood pressure, specifically arterial blood pressure is determined by a few physiologic parameters: Heart rate(HR), stroke volume(SV), and systemic vascular resistance (SVR)

%%{ init: { 'flowchart': { 'curve': 'bump'}}}%%
flowchart LR
    map[MAP]
    map ---> svr[SVR]
    map --> co[CO]
    co --> SV
    co --> HR

## Differential

Circulatory shock is a medical emergency characterized by inadequate circulation of blood and oxygen to meet the needs of the body's tissues.
There are several different types of circulatory shock and we use measurements of cardiac output (CO), venous oxygenation (SvO2), and central venous pressure (CVP) to help differentiate/diagnose shock etiology.

%%{ init: { 'flowchart': { 'curve': 'bump'}}}%%
flowchart LR
    %%co((CO or SvO2))
    hiCO["#8593; CO\n(or nm)"]
    hiCO --> hiSVO2["#8593; SvO#8322;"] & loSVO2["#8595; SvO#8322;"]
    Low["#8595; CO"]
    %%Low --> CVP{"CVP"}
    Low --> hiCVP["#8593; CVP"]
    Low --> loCVP["#8595; CVP"]
    
    subgraph Shock types
        direction TB
        dist(Distributive)
        septic("Septic (early)")
        Hypovol(Hypovolemic)
        cardio(Cardiogenic)
        Obs(Obstructive)
    end
    %%hiCO ----> dist
    hiSVO2 --> septic
    loSVO2 --> dist
    hiCVP --> cardio & Obs
    loCVP --> Hypovol

In all cases of circulatory shock, the goal of resuscitation is to restore adequate blood flow and oxygenation to the body's tissues. The approach and specific vasopressors used will depend on the underlying cause of the shock. It's important to seek prompt medical attention in cases of suspected circulatory shock.

### Hypovolemic Shock
Caused by a loss of fluid from the circulatory system, such as from bleeding, dehydration, or severe burns. Look for Hx of fluid loss (hemorrhage, diarrhea, vomitting, diuretics, poor liquid intake)

**Approach to resuscitation**: Replace fluid loss with intravenous (IV) fluids, blood transfusion if necessary. Vasopressors not typically required.

### Cardiogenic Shock
Caused by an inadequate pumping of the heart, such as from a myocardial infarction, heart failure.
**Approach to resuscitation**: Support the heart with medications, such as inotropes, and manage any underlying causes.
**Vasopressors**: Inotropes improve cardiac output, such as dopamine, dobutamine, or norepinephrine.

### Distributive Shock
This is caused by dilation of blood vessels and decreased systemic vascular resistance, such as from sepsis, anaphylaxis, or spinal cord injury.

**Approach to resuscitation**: Treat the underlying cause, manage fluid balance, and maintain adequate blood pressure.
**Vasopressors**: Used to increase blood pressure and improve perfusion, such as norepinephrine, vasopressin, or phenylephrine.

### Obstructive Shock
Caused by a physical blockage of blood flow, such as from a blood clot, aortic stenosis, pulmonary embolism, or cardiac tamponade.

**Approach to resuscitation**: Remove the blockage and restore blood flow, manage fluid balance and blood pressure. **Vasopressors** may be used to increase blood pressure and maintain perfusion, such as norepinephrine or phenylephrine.

pie 
    title Types of shock
    "Distributive" : 66
    "Cardiogenic" : 16
    "Hypovolemic" : 16
    "Obstructive" :  2

## Pressors

%%{ init: { 'flowchart': { 'curve': 'bump'}}}%%
flowchart LR
    subgraph Shock
        dist(Anaphylactic)
        septic("Septic")
        Hypovol(Hypovolemic)
        cardio(Cardiogenic)
        Obs(Obstructive)
    end

    subgraph Pressor
        direction LR
        norepi[norepi fa:fa-arrow-right +vaso fa:fa-arrow-right +epi]
        septic --> norepi
        epinephrine
        vol[Blood/Fluids]
        ino[Dobutamine\nMilrinone]
        Obs -->|PE?| tPA
    end
    
    %%septic --> norepi
    dist --> epinephrine
    Hypovol --> vol
    cardio --> ino

%%{ init: { 'flowchart': { 'curve': 'basis'}}}%%
flowchart TB
    init("Add norepinephrine <br/>titrate to 40-90ug/min")
    subgraph addpress [Pressor escalation<br>]
        %%direction BT
        vaso["Add Vasopressin <br/> up to 30 U/min"];
        epi["Add Epinephrine <br/> up to 20-50 ug/min"];
        neo["Add phenylephrine <br/> up to 200-300 ug/min"];
        vaso --> epi
        epi --> neo
    end
    init -->|MAP<65| addpress
    init ----->|MAP>65| goal
    %%vaso --> goal
    %%epi --> goal
    goal["Wean as tolerated"]
    neo --> nogoal["fa:fa-frown-o"]
    
    
    %%vaso -- MAP>65 --> goal 
    %%epi --MAP>65--> goal
    %%neo --MAP>65--> goal
    %%escalate ---> goal

## References
https://resident360.nejm.org/rotation-prep/critical-care/sepsis-shock/fast-facts

[Surviving Sepsis 2021](https://link.springer.com/article/10.1007/s00134-021-06506-y)