What is the difference in treatment between hypovolemia and hypovolemic shock?

Hypovolemia vs Hypovolemic Shock: Treatment Differences

The fundamental treatment difference is that hypovolemia requires controlled fluid boluses with careful monitoring, while hypovolemic shock demands immediate aggressive fluid resuscitation (minimum 30 mL/kg in adults, 20 mL/kg in children) plus vasopressors if perfusion does not normalize. 1

Key Clinical Distinction

The critical difference lies in tissue perfusion status:

• Hypovolemia = decreased intravascular volume that may still be compensated, with adequate tissue perfusion 1
• Hypovolemic shock = inadequate tissue perfusion with cellular hypoxia that progresses to multiple organ failure and death if untreated 1

Clinical indicators that hypovolemia has progressed to shock include: hypotension, altered mental status, capillary refill >2 seconds, cool extremities with weak peripheral pulses, decreased urine output, and elevated lactate 1

Treatment Algorithm for Hypovolemia (Without Shock)

Fluid Administration

• Administer controlled boluses: 500-1000 mL over 15-30 minutes in adults, or 20 mL/kg over 5-10 minutes in children 1, 2
• Reassess after each bolus for improvement in perfusion parameters before giving additional fluid 1
• Use isotonic crystalloids (normal saline or lactated Ringer's solution) as first-line therapy 1, 2

Monitoring Parameters

• Monitor for improvement in heart rate, blood pressure, capillary refill, mental status, and urine output 2
• Stop fluid administration if signs of fluid overload develop (hepatomegaly, pulmonary rales, gallop rhythm, increased work of breathing, decreased oxygen saturation) 2

Treatment Algorithm for Hypovolemic Shock

Immediate Aggressive Fluid Resuscitation

Adults:

• Administer minimum 30 mL/kg of isotonic crystalloids within the first 3 hours, given as 500-1000 mL boluses over 15-30 minutes 3, 2
• May require up to 60 mL/kg in the first hour if perfusion does not normalize 1
• Balanced crystalloids (lactated Ringer's) are preferred over 0.9% NaCl to reduce mortality and adverse renal events 3

Children:

• Administer 20 mL/kg boluses rapidly over 5-10 minutes, with immediate reassessment after each bolus 1, 2
• Repeat up to 60 mL/kg in the first hour if perfusion does not normalize 1, 2
• May require up to 200 mL/kg total if signs of fluid overload are absent 2

Vasopressor Therapy

When to initiate vasopressors:

• When mean arterial pressure (MAP) remains <65 mmHg after initial fluid resuscitation 3, 2
• When signs of persistent tissue hypoperfusion continue despite adequate fluid 2
• In children: after 40-60 mL/kg; in adults: after 30 mL/kg 2

Vasopressor selection:

• Norepinephrine is the first-choice vasopressor, targeting MAP of 65 mmHg 3, 1
• Epinephrine should be added to or potentially substituted for norepinephrine when an additional agent is needed 3
• Vasopressin 0.03 units/minute can be added to norepinephrine to raise MAP or decrease norepinephrine dosage 3

Resuscitation Endpoints

Target parameters indicating adequate resuscitation:

• MAP ≥65 mmHg 1
• 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

Fluid Type Selection

Crystalloids vs Colloids

For both hypovolemia and hypovolemic shock, crystalloids are the fluid of choice:

• Crystalloids are recommended as initial fluid for resuscitation 3
• Hydroxyethyl starches are contraindicated due to increased mortality and renal failure risk in septic shock 3
• The CRISTAL trial showed no difference in 28-day mortality between colloids and crystalloids in hypovolemic shock (25.4% vs 27.0%, p=0.26), though 90-day mortality favored colloids (30.7% vs 34.2%, p=0.03) 4

Albumin considerations:

• Albumin may be added to crystalloids when patients require substantial amounts of crystalloids 3
• For hemorrhagic shock specifically, albumin is not recommended as no benefit has been demonstrated 3
• Albumin 25% is indicated for hypovolemic shock when hyperoncotic expansion is needed, expanding plasma volume 3-4 times the administered volume 5

Balanced vs Unbalanced Crystalloids

Balanced crystalloids (lactated Ringer's) are preferred over 0.9% NaCl:

• Balanced solutions offer better plasma composition and help prevent acute kidney injury 3, 6
• In hemorrhagic shock, balanced crystalloids should be used rather than 0.9% NaCl to reduce mortality and adverse renal events 3
• The evidence for benefits in patient morbidity and mortality with balanced solutions is increasing 6

Critical Pitfalls to Avoid

Do not rely solely on blood pressure to guide fluid therapy; assess perfusion parameters comprehensively including capillary refill, mental status, and urine output 2

Do not continue aggressive fluid resuscitation without reassessing for fluid overload after each bolus 2

Do not delay vasopressor initiation in fluid-refractory shock; begin after 40-60 mL/kg in children or 30 mL/kg in adults 2

Do not use hypotonic fluids for shock resuscitation in any age group 2

In hemorrhagic shock, use vasopressors cautiously and administer blood products separately from crystalloids 1

For trauma with significant tissue destruction (electrical shock, rhabdomyolysis), target urine output >1 mL/kg/hour to facilitate myoglobin excretion and prevent acute kidney injury 1