The Nomenclature, Definition and Distinction of Types of Shock

Abstract

Background: A severe mismatch between the supply and demand of oxygen is the common feature of all types of shock. We present a newly developed, clinically oriented classification of the various types of shock and their therapeutic implications.

Methods: This review is based on pertinent publications (1990-2018) retrieved by a selective search in PubMed, and on the relevant guidelines and meta-analyses.

Results: There are only four major categories of shock, each of which is mainly related to one of four organ systems. Hypovolemic shock relates to the blood and fluids compartment while distributive shock relates to the vascular system; cardiogenic shock arises from primary cardiac dysfunction; and obstructive shock arises from a blockage of the circulation. Hypovolemic shock is due to intravascular volume loss and is treated by fluid replacement with balanced crystalloids. Distributive shock, on the other hand, is a state of relative hypovolemia resulting from pathological redistribution of the absolute intravascular volume and is treated with a combination of vasoconstrictors and fluid replacement. Cardiogenic shock is due to inadequate function of the heart, which shall be treated, depending on the situation, with drugs, surgery, or other interventional procedures. In obstructive shock, hypoperfusion due to elevated resistance shall be treated with an immediate life-saving intervention.

Conclusion: The new classification is intended to facilitate the goal-driven treatment of shock in both the pre-hospital and the inpatient setting. A uniform treatment strategy should be established for each of the four types of shock.

Figure 1

Synoptic view of the four types of shock (inner, white field) with the organ systems primarily associated with them (outer corners), sites and mechanisms of manifestation (outside the circle), and pathogenetic and pathophysiologic features (outer and middle sectors of the circle). To maintain clarity, mixed types of shock are not depicted.

Figure 2

Algorithm for differential diagnosis as the basis for treatment of the different types of shock SvO2, central venous oxygen blood saturation

eFigure

Pathomechanism of neurogenic shock: Connections in the autonomic system for heart rate and blood pressure regulation. NA, nucleus ambiguus; RVLM, rostral ventrolateral nucleus in the medulla; NTS, nucleus tractus solitarii