Skip to main content

Shock Definition and Dopamine

Question# 852

In the ROSC, Symptomatic Bradycardia and Cardiogenic Shock directives, "Mechanical shock" is listed as a contraindication across all three directives against the administration of Dopamine. The four main shock types are cardiogenic, distributive, hypovolemic and obstructive. Can you please clarify examples of "mechanical shock"; is it simply meant as obstructive shock in these directives, or are there "mechanical shock" states which could be classified under the other main shock types as well?

Answer:

Shock is characterized by a condition of cellular and tissue hypoxia, which occurs due to reduced oxygen delivery, increased oxygen consumption, insufficient oxygen utilization, or a combination of these factors.

As you pointed out, shock can be classified in various ways, each with distinct presentations and treatment approaches.


In general, the terms "mechanical" and "obstructive" describe similar underlying issues: extracardiac factors that hinder blood flow, that is a scenario characterized by an obstruction to blood flow that causes significant circulatory compromise and inadequate tissue perfusion. These terms are often used interchangeably.

Examples of mechanical or obstructive shock include tension pneumothorax, cardiac tamponade, pulmonary embolism (PE), constrictive pericarditis, aortic stenosis, tumors (for example, atrial tumor), and dissecting aortic aneurysm.

A useful mnemonic to help identify the cause of shock is:

  • S: septic/spinal
  • H: hypovolemic
  • O: obstructive/mechanical
  • C: cardiogenic
  • K: anaphylactic (“K”)

Dopamine is used as a vasoconstrictor and as an inotrope. However, tachycardia and vasoconstriction are known effects of dopamine. Together, they can raise cardiac oxygen demand as well as reduce oxygen delivery and that may worsen the patient outcome in cases of obstructive shock. Therefore, dopamine use is contraindicated in patients with obstructive shock.

References

- Evaluation of and initial approach to the adult patient with undifferentiated hypotension and shock – UpToDate (https://www.uptodate.com/contents/evaluation-of-and-initial-approach-to-the-adult-patient-with-undifferentiated-hypotension-and-shock?search=obstructive%20shockEvaluation%20of%20and%20initial%20approach%)
- Definition, classification, etiology, and pathophysiology of shock in adults – UpToDate (https://www.uptodate.com/contents/definition-classification-etiology-and-pathophysiology-of-shock-in-adults?search=mechanicl%20shock&source=search_result&selectedTitle=3%7E150&usage_type=default&display_rank=2)
- -Standl T, Annecke T, Cascorbi I, Heller AR, Sabashnikov A, Teske W. The Nomenclature, Definition and Distinction of Types of Shock. (https://pmc.ncbi.nlm.nih.gov/articles/PMC6323133/)
- Herget-Rosenthal S, Saner F, Chawla LS. Approach to hemodynamic shock and vasopressors (https://pmc.ncbi.nlm.nih.gov/articles/PMC6631076/)
- Ontario Base Hospital Group. 2005. Paramedic Resource Manual: Shock. https://www.lakeridgehealth.on.ca/en/ourservices/resources/0004_-_SHOCK_-_complete.pdf
Back to the questions

Published

20 November 2024

ALSPCS Version

5.3

Views

74

Please reference the MOST RECENT ALS PCS for updates and changes to these directives.