What are the guidelines for managing hypovolemic shock?

Management of Hypovolemic Shock

Immediately initiate aggressive fluid resuscitation with isotonic crystalloids (normal saline or lactated Ringer's), administering a minimum of 30 mL/kg in adults and 20 mL/kg in children as rapid boluses, with the option to repeat up to 60 mL/kg in the first hour if perfusion does not normalize. 1

Initial Fluid Resuscitation

Crystalloid Administration

• Isotonic crystalloids are the first-line fluid of choice for hypovolemic shock, with normal saline (0.9% sodium chloride) or lactated Ringer's solution as the primary options 2, 1
• Administer rapid boluses: 250-1000 mL in adults over 5-10 minutes, or 20 mL/kg in children over 5-10 minutes 3, 1
• Reassess hemodynamic status after each bolus before administering additional fluid 2, 1
• In severe shock, total fluid requirements may reach 40-60 mL/kg or more in the first hour 3, 1

Colloid Considerations

• Albumin may be used as an alternative to crystalloids for initial resuscitation, though crystalloids remain preferred 3, 2
• Avoid hydroxyethyl starches due to increased risk of acute kidney injury and mortality 2
• Colloids offer no mortality benefit at 28 days compared to crystalloids, though 90-day mortality may be slightly lower (exploratory finding requiring further study) 4

Hemodynamic Monitoring and Targets

Critical Assessment Parameters

• Monitor these specific endpoints after each fluid bolus: 1
  • Mean arterial pressure (MAP) ≥65 mmHg
  • Capillary refill ≤2 seconds
  • Warm extremities with strong peripheral pulses
  • Normal mental status (reversal of altered consciousness)
  • Urine output >0.5 mL/kg/hour in adults, >1 mL/kg/hour in children
  • Decreasing serum lactate levels (aim for 20% reduction if elevated) 2, 1

Signs of Adequate vs. Excessive Resuscitation

• Stop fluid administration if hepatomegaly or pulmonary rales develop, as these indicate fluid overload 3
• Use dynamic measures of fluid responsiveness rather than static measures like central venous pressure alone 2

Vasopressor Support

When to Initiate Vasopressors

• Begin vasopressor therapy if hypotension persists despite adequate fluid resuscitation (after 30-60 mL/kg crystalloid) 1
• In children not responsive to fluid resuscitation, consider peripheral inotropic support until central venous access can be obtained, as delay in inotrope use significantly increases mortality risk 3

Vasopressor Selection and Dosing

• Norepinephrine is the first-choice vasopressor for hypovolemic shock, targeting MAP of 65 mmHg 1, 5
• Dilute norepinephrine 4 mg in 1000 mL of 5% dextrose solution (4 mcg/mL concentration) 5
• Initial dose: 8-12 mcg/minute (2-3 mL/minute of diluted solution), 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 tissue necrosis from extravasation 5
• Monitor blood pressure every 2 minutes until target achieved, then every 5 minutes 5

Critical Caveat on Vasopressor Use

• Blood volume depletion must be corrected as fully as possible before vasopressor administration, except in emergency situations where intraaortic pressure must be maintained to prevent cerebral or coronary ischemia 5
• If occult hypovolemia is suspected in patients requiring high vasopressor doses, reassess volume status with central venous pressure monitoring 5

Special Considerations

Hemorrhagic Shock

• In hemorrhagic shock, apply permissive hypotension (systolic BP 80-90 mmHg) to limit ongoing bleeding if no contraindications exist 6
• Administer blood products separately from crystalloids 1
• Target hemoglobin 7-9 g/dL; in massive transfusion, use red blood cells:plasma:platelets ratio of 4:4:1 6
• Early administration of tranexamic acid and fibrinogen is recommended to stabilize coagulation 6
• Maintain normothermia, pH >7.2, and normocalcemia 6

Pediatric-Specific Considerations

• Blood pressure alone is unreliable in children for assessing shock adequacy, as they maintain BP through vasoconstriction and tachycardia until cardiovascular collapse occurs 3
• In children with severe hemolytic anemia (severe malaria or sickle cell crisis) who are not hypotensive, blood transfusion is superior to crystalloid or albumin bolusing 3

Trauma and Myoglobinuria

• In electrical shock or trauma with significant tissue destruction, target urine output >1 mL/kg/hour to facilitate myoglobin excretion and prevent acute kidney injury 1

Common Pitfalls to Avoid

• Never leave a patient unattended while receiving vasopressors; continuous monitoring is essential 5
• Avoid infusing vasopressors into leg veins, particularly in elderly patients or those with occlusive vascular disease, due to increased risk of gangrene 5
• Do not use vasopressors during cyclopropane or halothane anesthesia due to risk of ventricular arrhythmias 5
• Gradually reduce vasopressor infusions rather than abruptly withdrawing to prevent rebound hypotension 5