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:

  • 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
    • What is the LV end-diastolic volume?
  • Contractility
    • Is the myocardium severely depressed in its contractile function (cardiogenic shock)?
    • Is forward flow occurring?
      • Assess for valvular dysfunction (MR, AR)
      • Assess for obstruction (PE, tamponade)
  • 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

Consider RUSH to CVS


  • Treat underlying type


PressorInitial DoseMax DoseCardiac EffectBP EffectArrhythmiasSpecial Notes
Dobutamine3-5 mcg/kg/min5-15 mcg/kg/min (as high as 200) [5]Strong ß1 agonist +inotrope +chronotrope, Weak ß2 agonist +weak vasodilatation )alpha effect minimalHR variable effects [6]. Also Increase SA and AV node fxindicated in decompensated systolic HF, Debut Research 1979[7] Isoproterenol has most Β2 vasodilatory and Β1 HR effects
Dopamine2 mcg/kg/min20-50 mcg/kg/minβ1 and NorEpi releaseα effects if > 20mcg/kg/minArrhythmogenic from β1 effectsMore adverse events when used in shock compared to Norepi[8]
Epinepherine0.1-1 mcg/kg/min+ inotropy, + chronotropy
Norepinephrine0.2 mcg/kg/min0.2-1.3 mcg/kg/min (5mcg/kg/min) [9]mild β1 direct effectβ1 and strong α1,2 effectsLess arrhythmias than Dopamine[8]First line for sepsis. Increases MAP with vasoconstriction, increases coronary perfusion pressure, little β2 effects.
Milrinone50 mcg/kg x 10 min0.375-75 mcg/kg/minDirect influx of Ca2+ channelsSmooth muscle vasodilatorPDE Inhibitor which increases Ca2+ uptake by sarcolemma. No venodilatory activity
Phenylephrine100-180 mcg/min then 40-60 mcg/min0.4-9 mcg/kg/minAlpha agonistLong half life
VasopressinFixed Dose0.01 to 0.04 U/minunknownincreases via ADH peptideshould not be titrated due to ischemic effects
Methylene blue[10]IV bolus 2 mg/kg over 15 min1-2 mg/kg/hourPossible increased inotropy, cardiac use of ATPInhibits NO mediated peripheral vasodilationDon't use in G6PD deficiency, ARDS, pulmonary hypertension
Medication IV Dose (mcg/kg/min) Concentration
Norepinephrine (Levophed)0.1-2 mcg/kg/min8mg in 500mL D5W
Dopamine2-20 mcg/kg/min400mg in 250 D5W
Dobutamine2-20 mcg/kg/min250mg in 250 mg D5W
Epinephrine0.1-1 mcg/kg/min1mg in 250 D5W

See Also


  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. https://www.ncbi.nlm.nih.gov/pubmed/8449087
  6. Edmund H. Sonnenblick, M.D., William H. Frishman, M.D., and Thierry H. LeJemtel, M.D. Dobutamine: A New Synthetic Cardioactive Sympathetic Amine
  7. De Backer Daniel et al. Comparison of Dopamine and Norepinephrine in the Treatment of Shock. NEJM 363(9). 779-789
  8. https://www.ncbi.nlm.nih.gov/pubmed/15542956
  9. Pasin L et al. Methylene blue as a vasopressor: a meta-analysis of randomised trials. Crit Care Resusc. 2013 Mar;15(1):42-8.


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