SVR Explained: Why Resistance Reveals Shock Better Than Blood Pressure

Welcome to Pulse and Pressors, where critical care gets crystal clear.
Systemic Vascular Resistance (SVR) is the forgotten giant of shock management. We chase MAP, tweak pressors, and argue about fluids, but shock is fundamentally defined by the relationship between flow (CO/CI) and resistance (SVR) – not pressure alone.
In this episode, we break SVR down with 0.1% expert precision and real bedside relevance:
What you’ll learn
• The SVR formula and what the “80” actually does
• Normal and pathologic SVR/SVRi ranges in dynes·sec·cm⁻⁵
• Poiseuille’s Law made simple: radius to the 4th power and vasoplegia
• The SVR + CO shock matrix: distributive, cardiogenic, hypovolemic, mixed, and high-output shock
• Worked clinical cases: septic, cardiogenic, mixed shock, and post-cardiac surgery vasoplegia
• How vasopressors, inotropes, and vasodilators quantitatively shift SVR
• SVR targets for septic, cardiogenic, and post–cardiac arrest resuscitation
• Why high SVR does not guarantee organ perfusion (autoregulation and shunting)
• SVR patterns in sepsis, anaphylaxis, neurogenic shock, cirrhosis, hypothermia, and post-CPB vasoplegia
• SVR vs arterial elastance (Ea) and ventriculo-arterial coupling (fellowship-level concept)
• The limitations of SVR: global average, regional heterogeneity, and microcirculatory disconnect
You’ll see exactly how to:
• Calculate SVR in real time
• Interpret it in context of CO, lactate, and perfusion markers
• Choose the right tool: fluid, vasopressor, inotrope, or afterload reduction
• Aim for “adequate MAP at the lowest necessary SVR” instead of blind MAP chasing
If you want to move beyond “MAP 65” and think like a hemodynamics architect, this SVR masterclass is non-negotiable.
This is Pulse & Pressors, reflecting on the marvels of the human body.

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