What are the recommendations for maintaining adequate urine output in patients with sepsis?

Maintaining Adequate Urine Output in Patients with Sepsis

In patients with sepsis, urine output should be maintained at ≥0.5 mL/kg/h through protocolized fluid resuscitation with at least 30 mL/kg of crystalloid within the first 3 hours, followed by dynamic assessment of fluid responsiveness and vasopressor therapy if needed. 1

Initial Assessment and Management

Definition of Adequate Urine Output

• Adequate urine output in sepsis is defined as ≥0.5 mL/kg/h or ≥45 mL/h 1
• Acute oliguria is defined as urine output ≤0.5 mL/kg/h for at least 2 hours despite adequate fluid resuscitation 1

Early Fluid Resuscitation Protocol

1. Administer initial fluid resuscitation with 30 mL/kg of crystalloid within the first 3 hours 1
2. Consider administering up to 40-60 mL/kg (10-20 mL/kg per bolus) of crystalloids in the first hour, titrated to clinical markers of cardiac output 1
3. Further fluid should be given according to functional hemodynamic measurements 1

Monitoring Response to Fluid Resuscitation

A positive response to fluid resuscitation includes:

• ≥10% increase of systolic/mean arterial blood pressure
• ≥10% reduction of heart rate
• Improvement of mental state and peripheral perfusion
• Improvement in urine output 1

Hemodynamic Targets to Support Adequate Urine Output

Blood Pressure Targets

• Maintain mean arterial pressure (MAP) ≥65 mmHg as the driving pressure for tissue perfusion 2, 1
• Use norepinephrine as the first-choice vasopressor if fluid resuscitation fails to restore MAP 1
• Consider epinephrine as a second agent when needed 1
• Vasopressin (0.03 U/min) can be added to norepinephrine, but not as the initial vasopressor 1

Central Venous Pressure (CVP)

• Target CVP of 8-12 mmHg during initial resuscitation 2
• Although CVP has limitations as a marker of intravascular volume status, a low CVP generally indicates need for additional fluid 2

Oxygen Saturation Targets

• Target superior vena cava oxygen saturation (ScvO2) ≥70% or mixed venous oxygen saturation (SvO2) ≥65% 2

Fluid Management Phases in Sepsis

Fluid therapy can be conceptualized in 4 overlapping phases 3:

1. Resuscitation phase: Rapid fluid administration to restore perfusion

   • Administer at least 30 mL/kg crystalloid within first 3 hours 1
   • Complete this volume ideally within 3 hours for survival benefit 4

2. Optimization phase: Evaluate risks/benefits of additional fluids

   • Use dynamic measures to assess fluid responsiveness 1
   • Passive leg raises, fluid challenges against stroke volume measurements
   • Variations in systolic pressure, pulse pressure, or stroke volume in response to mechanical ventilation

3. Stabilization phase: Administer fluid only when there is evidence of fluid responsiveness

   • Monitor urine output closely as a marker of adequate perfusion
   • Avoid fluid overload as it can lead to respiratory impairment 1

4. Evacuation phase: Eliminate excess fluid accumulated during treatment

   • Consider diuretics when appropriate during recovery phase

Avoiding Complications

Preventing Fluid Overload

• Stop fluid resuscitation when no improvement of tissue perfusion occurs in response to volume loading 1
• Development of crepitations indicates fluid overload or impaired cardiac function 1
• Avoid hydroxyethyl starch solutions as they significantly increase the incidence of kidney replacement therapy 3

Monitoring for Kidney Injury

• Regularly assess urine output and serum creatinine for early detection of acute kidney injury
• Measure serum lactate level (elevated lactate ≥2 mmol/L indicates tissue hypoperfusion) 1
• Repeat lactate measurement within 6 hours if initially elevated 1

Special Considerations

• Some patients may require several liters of fluids during the first 24-48 hours based on individual factors 1
• Dosing less than 20 mL/kg has been associated with increased mortality 4
• Observational studies suggest potential increased mortality with higher volume resuscitation (>45 mL/kg), but this is not supported by randomized trials 4

Antimicrobial Therapy

• Administer broad-spectrum antimicrobials within 1 hour of recognition for patients with septic shock and within 3 hours for those with sepsis without shock 1
• Appropriate antimicrobial therapy is crucial for source control, which indirectly supports renal perfusion and urine output