Undifferentiated shock

Undifferentiated Hypotension Algorithm

Check/manage the following in order:

• Pulse (assess based on pt'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?
    • Approximated by the IVC diameter or CVP
    • If low:
      • Assess for blood loss versus fluid loss
        • FAST for intra-abdominal bleed
        • US for ruptured AAA
        • Guaiac for GI bleed
        • CXR for hemothorax
      • Treat with IVF and/or pRBC depending on cause
• Contractility
  • Is the myocardium severely depressed in its contractile function (cardiogenic shock)?
    • Assess via ultrasound
    • Treat w/ inotrope
  • 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

• Cardiogenic
  • Acute valvular Regurgitation/VSD
  • CHF
  • Dysrhythmia
  • ACS
  • Myocardial Contusion
  • Myocarditis
  • Drug toxicity (e.g. beta blocker, CCB, or bupropion OD)
• Obstructive
  • Air embolism
  • Aortic Stenosis
  • Cardiac Tamponade
  • PE
  • Tension pneumothorax
• Distributive
  • Adrenal crisis
  • Anaphylaxis
  • Neurogenic shock
  • Sepsis
  • Toxicologic
• Hypovolemic
  • Severe dehydration
  • Hemorrhagic shock (traumatic and non-traumatic)

Management

• Treat underlying type

Vasopressors

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)	Strong ß1 agonist +inotrope +chronotrope, Weak ß2 agonist +weak vasodilatation )	alpha effect minimal	HR variable effects.	indicated in decompensated systolic HF, Debut Research 1979 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
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)	mild β1 direct effect	β1 and strong α1,2 effects	Less arrhythmias than Dopamine	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	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

See Also

• Ultrasound in Shock and Hypotension