What is the guideline for managing hypovolemic shock?

Management of Hypovolemic Shock

For hypovolemic shock, immediately initiate aggressive fluid resuscitation with isotonic crystalloids (normal saline or lactated Ringer's), administering 30 mL/kg in adults or 20 mL/kg boluses in children within the first hour, followed by norepinephrine as the first-line vasopressor if mean arterial pressure remains below 65 mmHg despite adequate fluid resuscitation. 1, 2

Distinguishing Hypovolemia from Hypovolemic Shock

The critical first step is determining whether the patient has simple hypovolemia or has progressed to shock:

• Hypovolemic shock is defined by inadequate tissue perfusion with cellular hypoxia that, if untreated, progresses to multiple organ failure and death, not merely decreased intravascular volume 1
• Key clinical indicators of shock include hypotension, altered mental status, capillary refill >2 seconds, cool extremities with weak peripheral pulses, decreased urine output, and elevated lactate 1
• The Shock Index (heart rate divided by systolic blood pressure) ≥0.9-1.0 indicates increased severity and need for aggressive intervention 3

Critical pitfall: Blood pressure may remain normal until late stages due to compensatory mechanisms, particularly in children who can maintain normal blood pressure despite significant volume loss 3. Do not rely solely on blood pressure to guide therapy 2.

Initial Fluid Resuscitation Strategy

Adults

• Administer 500-1000 mL boluses of isotonic crystalloid over 15-30 minutes, targeting 30 mL/kg within the first 3 hours 2
• Use lactated Ringer's solution as preferred first-line therapy over normal saline 2
• Reassess perfusion parameters after each bolus: mental status, capillary refill, peripheral warmth, and urine output 2

Pediatric Patients

• Administer 20 mL/kg boluses of isotonic crystalloid rapidly over 5-10 minutes 4, 2
• Repeat boluses up to 60 mL/kg in the first hour if perfusion does not normalize 2
• May require up to 200 mL/kg total if signs of fluid overload are absent 2
• Establish intravenous or intraosseous access immediately 2

Fluid Choice

• Isotonic saline is the first-choice fluid for resuscitation in neonates and children based on evidence showing no mortality difference between crystalloids and colloids, with no evidence that synthetic colloids or albumin are superior 4
• Never use hypotonic fluids for shock resuscitation in any age group 2

Vasopressor Therapy

Blood volume depletion should always be corrected as fully as possible before any vasopressor is administered 5

• Initiate norepinephrine when MAP remains <65 mmHg after initial fluid resuscitation (after 40-60 mL/kg in children or 30 mL/kg in adults) 1, 2
• Norepinephrine is the first-choice vasopressor for hypovolemic shock, with epinephrine as an alternative or addition 1
• Starting dose: 8-12 mcg/minute (2-3 mL/minute of standard 4 mcg/mL dilution), then titrate to maintain MAP ≥65 mmHg 5
• Average maintenance dose: 2-4 mcg/minute (0.5-1 mL/minute) 5
• Administer through a large central vein when possible to avoid extravasation 5

Critical consideration: When intraaortic pressures must be maintained to prevent cerebral or coronary ischemia, norepinephrine can be administered before and concurrently with blood volume replacement 5

Target Resuscitation Endpoints

Monitor and target the following parameters:

• MAP ≥65 mmHg 1, 5
• Capillary refill ≤2 seconds 1, 2
• Warm extremities with strong peripheral pulses 1, 2
• Normal mental status 1, 2
• Urine output >1 mL/kg/hour (children) or >0.5 mL/kg/hour (adults) 1
• Decreasing lactate levels 1

When to Stop Fluid Resuscitation

Discontinue or reduce fluid administration when:

• Signs of fluid overload develop: hepatomegaly, new or worsening pulmonary rales/crackles, gallop rhythm, increased work of breathing, decreased oxygen saturation, or increased jugular venous pressure 2
• Patient has received adequate volume (30 mL/kg in adults, 60 mL/kg in children) without response 2
• Perfusion parameters normalize 2

Special Considerations

Hemorrhagic Shock

• Blood products should be administered separately from crystalloids 1
• Use vasopressors cautiously in hemorrhagic shock 1
• Hemoglobin target of 7-9 g/dL is generally recommended 6
• For massive transfusion, use a ratio of red blood cells:plasma:platelets of 4:4:1 6

Electrical Shock or Rhabdomyolysis

• Target urine output >1 mL/kg/hour to facilitate myoglobin excretion and prevent acute kidney injury 1

Monitoring

• Central venous pressure monitoring is helpful in detecting occult blood volume depletion when patients remain hypotensive despite large fluid volumes 5
• Ultrasound assessment showing small, collapsing inferior vena cava and small cardiac chambers indicates severe hypovolemia 3