DIP Episode 233 - Shock

Source / episode info

**Episode:**233
**Title:**Divine Intervention Episode 233 – Shock.
**Published:**2020-05-01
Source:Episode page

One-liner

This episode reviews the distinct hemodynamic profiles of major shock types (septic, cardiogenic, hypovolemic, neurogenic), emphasizing key measurements like SVR, CVP, PCWP, and Mixed Venous Oxygen Saturation ({SvO}_2).

High-yield summary

Septic Shock: Characterized by massive vasodilation leading to low SVR. CO is typically elevated (or inappropriately normal). {CVP} and {PCWP} are often low, and {SvO}_2 is high due to systemic hypoperfusion/high extraction.
Cardiogenic Shock: Low CO due to pump failure (e.g., post-MI, tamponade). This results in high SVR (compensatory vasoconstriction), high {CVP} and {PCWP}, and low {SvO}_2 (due to maximal tissue extraction).
Hypovolemic Shock: Low CO due to decreased preload/blood volume. High SVR is maintained by compensatory mechanisms, resulting in low {CVP} and {PCWP}.
Neurogenic Shock: Unique because both CO and SVR are simultaneously low (loss of sympathetic tone). This typically presents with profound hypotension and bradycardia ({HR} < 60).
Sepsis Diagnosis: Requires meeting criteria (e.g., SIRS/qSOFA) plus evidence of infection source, progressing to severe sepsis if signs of organ dysfunction are present (e.g., elevated lactate, acute kidney injury).

Learning objectives

Differentiate the hemodynamic profiles (\text{CO}, \text{SVR}, \text{CVP}, \text{PCWP}, \text{SvO}_2) across the four major types of shock.
Understand the pathophysiology and initial management steps for septic, cardiogenic, hypovolemic, and neurogenic shock.
Recognize the criteria used to diagnose sepsis (SIRS/qSOFA) and severe sepsis.
Interpret \text{Mixed Venous Oxygen Saturation} (\text{SvO}_2) as an indicator of systemic oxygen extraction efficiency in different shock states.

Board exam buzzwords

Condition	Key Finding	Association	Board Exam Tip
Septic Shock	Low SVR, High CO	Inflammatory mediators (histamine, etc.) cause vasodilation.	Remember that {CVP} and {PCWP} are low because the blood is moving forward rapidly.
Cardiogenic Shock	High SVR, Low CO	Pump failure; compensatory vasoconstriction.	The hallmark finding is high filling pressures ({CVP}/{PCWP}) with low cardiac output.
Hypovolemic Shock	Low {CVP} and {PCWP}, High {SVR}	Blood loss/volume depletion (decreased preload).	Always think of volume replacement first; the compensatory SVR is high to maintain BP.
Neurogenic Shock	Low {CO} AND Low {SVR}	High spinal cord injury (T-levels) affecting sympathetic outflow.	This is the only shock state where both CO and SVR are low simultaneously. Also associated with bradycardia.