How to apply the FURST (Fluid resuscitation, Urine output, Renal function, and Shock management) ratio in clinical practice?

Using the FURST Ratio in Clinical Practice

The FURST ratio (Fluid resuscitation, Urine output, Renal function, and Shock management) should be used as a dynamic measure to guide fluid resuscitation by targeting urine output of 0.5-1 mL/kg/h in adults while monitoring renal function and shock parameters. 1, 2

Components of the FURST Ratio

Fluid Resuscitation

• Begin with 30 mL/kg of crystalloid solution within the first 3 hours for patients in shock or with significant fluid needs 1, 3
• Either balanced crystalloids or normal saline can be used, though balanced solutions may be preferred to avoid hyperchloremic metabolic acidosis 2, 3
• After initial resuscitation, further fluid administration should be determined by individual patient factors and measures of fluid responsiveness 4
• Avoid relying solely on static measures like central venous pressure (CVP) to guide fluid therapy, as the ability to predict fluid responsiveness when CVP is within normal range (8-12 mm Hg) is limited 1

Urine Output

• Target urine output of 0.5-1 mL/kg/h in adults as the primary clinical indicator of adequate fluid resuscitation 1, 2
• For children, target urine output of 1-2 mL/kg/h, though when a child reaches 30-50 kg, maintain urine output at adult levels 5
• Persistent oliguria (<0.5 mL/kg/h) despite adequate volume resuscitation indicates potential renal injury requiring urgent nephrology consultation 1

Renal Function

• Monitor serum creatinine, blood urea nitrogen, and electrolytes to assess renal function 1
• Be vigilant for signs of acute kidney injury, which may require adjustment of fluid strategy 1
• For patients with end-stage renal disease on hemodialysis, aggressive fluid resuscitation (≥30 mL/kg) appears to be safe despite traditional concerns about volume overload 6

Shock Management

• Continuously monitor vital signs including heart rate, blood pressure, respiratory rate, and oxygen saturation 3
• If hypotension persists despite adequate fluid resuscitation, initiate vasopressor therapy targeting a mean arterial pressure of 65 mmHg 3
• Norepinephrine is the first-choice vasopressor and can be used in combination with fluid resuscitation 3, 7
• Using norepinephrine with fluid resuscitation can lead to a fluid volume-sparing effect with subsequently less hemodilution 7

Practical Application of the FURST Ratio

Initial Assessment

• Evaluate clinical state through heart rate, blood pressure, arterial oxygen saturation, respiratory rate, temperature, and urine output 1
• Consider echocardiography for a more detailed assessment of hemodynamic status 1
• Measure arterial lactate concentration as a marker of tissue hypoperfusion 1

Dynamic Monitoring

• Use dynamic measures to assess fluid responsiveness, including passive leg raises, fluid challenges against stroke volume measurements, or variations in systolic pressure, pulse pressure, or stroke volume 1
• Adjust fluid administration rates based on hourly urine output and other clinical parameters 1
• For patients with hemodynamic instability or persistent oliguria despite resuscitation, consider advanced monitoring such as echocardiography or cardiac output monitoring 1

Avoiding Common Pitfalls

• Avoid "fluid creep" (excessive fluid administration), which is associated with increased morbidity 1
• Equally avoid under-resuscitation, which can lead to tissue hypoperfusion and organ dysfunction 5
• Be cautious with hydroxyethyl starches due to increased risk of acute kidney injury 2
• For patients with cardiac dysfunction, consider smaller fluid boluses with more frequent reassessment 2

Special Considerations

• In burn patients, adjust fluid resuscitation based on the total body surface area affected 1
• For pediatric patients, calculate daily basal fluid intake requirement according to Holliday and Segar's 4-2-1 rule in addition to the fluid requirement determined by resuscitation formulas 1
• Consider adding albumin to crystalloids when patients require substantial amounts of crystalloids, particularly in burn patients with total burned body surface area over 30% after the first 6 hours 1, 2

By implementing the FURST ratio in clinical practice, clinicians can provide individualized hemodynamic management that optimizes fluid resuscitation while minimizing the risks of both under-resuscitation and fluid overload 8.