Undifferentiated shock

This page is for adult patients. For pediatric patients, see: undifferentiated shock.


  • Inadequate perfusion of the tissues
  • Goal to increase the flow of oxygenated blood to the tissues
  • MAP<50 in dog studies brain will become ischemic and patients might presents as an altered mental status [1]

Undifferentiated Hypotension Algorithm[2]

Check/manage the following in order:

Algorithm for the Evaluation of Hypotension(By Dr. Ravi Morchi)
  • Pulse (assess based on patient's age)
    • Too slow or too fast (to the point where CO is affected)?
      • If so, HR is likely primary etiology of hypotension
      • Pace or cardiovert
  • Volume status
  • Contractility
  • Systemic Vascular Resistance
    • Pathologic vasodilation (decreased SVR) suggested by:
      • Warm extremities
      • Bounding pulse
    • Treated based on likely etiology of distributive shock (see below)

Differential Diagnosis



Shock index (SI)[3]


  • Used when HR and SBP do not predict severity of hypovolemia in early stages
  • May be used as secondary triage tool in mass casualty incidents[4]
  • 0.5-0.7 is normal
  • >0.70-0.75 for occult shock or requirement of life-saving intervention

Simple Shock Index (sSI) was recently proposed. Subtracting SBP from HR is a good SI substitute. Working with integers is easier than dividing them, improving value availability.[5]

Consider RUSH to CVS


  • Treat underlying type


Pressor Initial Dose Max Dose Cardiac Effect BP Effect Arrhythmias Special Notes
Dobutamine 3-5 mcg/kg/min 5-15 mcg/kg/min (as high as 200) [6] Strong ß1 agonist +inotrope +chronotrope, Weak ß2 agonist +weak vasodilatation ) alpha effect minimal HR variable effects. indicated in decompensated systolic HF, Debut Research 1979[7] Isoproterenol has most Β2 vasodilatory and Β1 HR effects
Dopamine 2 mcg/kg/min 20-50 mcg/kg/min β1 and NorEpi release α effects if > 20mcg/kg/min Arrhythmogenic from β1 effects More adverse events when used in shock compared to Norepi[8]
Epinepherine 0.1-1 mcg/kg/min + inotropy, + chronotropy
Norepinephrine 0.2 mcg/kg/min 0.2-1.3 mcg/kg/min (5mcg/kg/min) [9] mild β1 direct effect β1 and strong α1,2 effects Less arrhythmias than Dopamine[8] First line for sepsis. Increases MAP with vasoconstriction, increases coronary perfusion pressure, little β2 effects.
Milrinone 50 mcg/kg x 10 min 0.375-75 mcg/kg/min Direct influx of Ca2+ channels Smooth muscle vasodilator PDE Inhibitor which increases Ca2+ uptake by sarcolemma. No venodilatory activity
Phenylephrine 100-180 mcg/min then 40-60 mcg/min 0.4-9 mcg/kg/min Alpha agonist Long half life
Vasopressin Fixed Dose 0.01 to 0.04 U/min unknown increases via ADH peptide should not be titrated due to ischemic effects
Methylene blue[10] IV bolus 2 mg/kg over 15 min 1-2 mg/kg/hour Possible increased inotropy, cardiac use of ATP Inhibits NO mediated peripheral vasodilation Don't use in G6PD deficiency, ARDS, pulmonary hypertension
Medication IV Dose (mcg/kg/min) Concentration
Norepinephrine (Levophed) 0.1-2 mcg/kg/min 8mg in 500mL D5W
Dopamine 2-20 mcg/kg/min 400mg in 250 D5W
Dobutamine 2-20 mcg/kg/min 250mg in 250 mg D5W
Epinephrine 0.1-1 mcg/kg/min 1mg in 250 D5W

Causes of non-response to vasopressors[11]

See Also

External Links


  1. Plöchl, W, D J Cook, T A Orszulak, and R C Daly. 1998. Critical cerebral perfusion pressure during tepid heart operations in dogs. The Annals of thoracic surgery, no. 1. http://www.ncbi.nlm.nih.gov/pubmed/9692450
  2. Morchi R. Diagnosis Deconstructed: Solving Hypotensionin 30 Seconds. Emergency Medicine News. 2015.
  3. Levitan, Richard M. Fundamentals of Airway Management. 3rd ed. Irving, TX: Emergency Medicine Residents' Association, 2015.
  4. Vassallo J et al. Usefulness of the Shock Index as a secondary triage tool. J R Army Med Corps. 2015 Mar;161(1):53-7.
  5. Kamikawa Y, Hayashi H. Equivalency between the shock index and subtracting the systolic blood pressure from the heart rate: an observational cohort study. BMC Emergency Medicine. 2020 Dec;20:1-8.
  6. https://www.ncbi.nlm.nih.gov/pubmed/8449087
  7. Edmund H. Sonnenblick, M.D., William H. Frishman, M.D., and Thierry H. LeJemtel, M.D. Dobutamine: A New Synthetic Cardioactive Sympathetic Amine
  8. 8.0 8.1 De Backer Daniel et al. Comparison of Dopamine and Norepinephrine in the Treatment of Shock. NEJM 363(9). 779-789
  9. https://www.ncbi.nlm.nih.gov/pubmed/15542956
  10. Pasin L et al. Methylene blue as a vasopressor: a meta-analysis of randomised trials. Crit Care Resusc. 2013 Mar;15(1):42-8.
  11. Anand Swaminathan, "Occult Causes of Non-Response to Vasopressors", REBEL EM blog, July 13, 2017. Available at: https://rebelem.com/occult-causes-of-non-response-to-vasopressors/.


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