I thought there may be some utility in having shock in its own little category, as failure of the "circulatory" organ system. Yes, there is a specific treatment for shock which addresses the causes, but let us presume that you are in some sort of nightmarish environment where the resources are scarce and competent assistance is absent. What do you do? It is "undifferentiated shock". And what about those situations when a patient with sepsis has a simultaneous sepsis-related cardiomyopathy, epidural abscess, and iatrogenic tension pneumothorax?
In short, non-specific shock ought to have its own clinical classification category and this page is in tribute to this under-appreciated entity. More detail, much of which is completely irrelevant to the CICM Fellowship Exam candidate, can be reviewed in the Definitions and Classification of Shock chapter from the section dealing with cardiovascular physiology.
Hypoxic: there isn’t enough oxygen, duuh.
Anaemic the blood is exposed to enough oxygen, but there is not enough hemoglobin to carry the oxygen
Stagnant: the blood is well oxygenated, but the circulation is slow, and the oxygen isn’t getting to the tissues- eg. cardiogenic shock
Histotoxic: the cells receive plenty of oxygen, but are unable to utilize it, eg. in cyanide poisoning
The mnemonic acronym for these four categories is HASH.
Neurogenic: another form of “distributive” shock
Anaphylactic: also “distributive” shock
Cardiogenic: pump failure. No pumping = no blood flow
Hypovolemic: loss of blood or water
Obstructive: eg. tension pneumothorax or cardiac tamponade
Septic: “distributive” shock; stagnation of blood flow owing to vasodilation
The mnemonic is NACHOS.
Whether these mnemonics are helpful or not remains to be seen. I am merely delighted to have my shock classifications spontaneously organise themselves into HASH and NACHOS.
Differential diagnosis of shock
This table has been compiled out of a collection of boxes which can be found in Matthew J Maiden and Sandra L Peake's chapter for the 7th edition of Oh's Manual (Ch. 15, "Overview of Shock" - p. 115). Other little bits and pieces have been added by the author, which degrades the authenticity somewhat. The goal was to blend HASH with NACHOS in a productive manner.
Artifactual or spurious
Mechanical support failure
Non-mechanical failure of the circulation