Hypotension and shock subtypes

Shock is one MAP reached by two routes. Dropping cardiac output (hypovolemic) or dropping resistance (distributive) both pull MAP below the 65 mmHg perfusion floor; at a matched 59 mmHg the engine separates the routes — CO 50 mL/s at normal SVR versus SVR 0.66 at normal CO. Grade [F]; Surviving Sepsis MAP≥65 [L].

Hypotension lands on the same Ohm identity from either factor. A cardiac-output fall and a resistance fall each drive MAP under 65 mmHg; the engine reproduces both and, at a matched MAP of 59 mmHg, attributes them to distinct knobs — the hemodynamic basis of shock classification.

One floor, two routes

The Surviving Sepsis Campaign sets a mean-arterial-pressure target of at least 65 mmHg during resuscitation; below it, organ perfusion is threatened (Asfar P et al., SEPSISPAM, N Engl J Med 2014;370:1583–1593, PMID 24635770). On the transport law a MAP this low can arise two ways.

Hypovolemic vs distributive

Lowering cardiac output (hypovolemic/cardiogenic) carries MAP down 96→77→63→59→50→41 mmHg; lowering systemic resistance (distributive/septic) carries it down 96→79→62→59→50→42 mmHg — both cross the 65 mmHg floor. At a matched MAP of 59 mmHg the two settings are mechanistically distinct: the hypovolemic route holds normal SVR (1.10) with reduced CO (50 mL/s), while the distributive route holds normal CO (83 mL/s) with reduced SVR (0.66). The engine thus reproduces the clinical principle that MAP names the emergency but CO and SVR name the cause.