What is the target urine output to resuscitate a patient with impaired renal function?

From the Guidelines

The target urine output for resuscitating a patient with impaired renal function is generally 0.5 mL/kg/hr, as recommended by the Surviving Sepsis Campaign guidelines 1. This target is part of the initial resuscitation goals, which also include a mean arterial pressure of at least 65 mm Hg and a central venous oxygen saturation of 70% or higher. The rationale for this target is to maintain adequate renal perfusion pressure while minimizing the risk of further kidney injury from either under-resuscitation or fluid overload.

Key Considerations

• Fluid resuscitation should be guided by frequent reassessment of vital signs, laboratory values, and clinical response.
• Isotonic crystalloids like normal saline or lactated Ringer's solution are typically used initially, with careful monitoring for signs of fluid overload such as pulmonary edema.
• In cases of severe renal impairment, earlier involvement of nephrology for possible renal replacement therapy should be considered.
• The target urine output may need to be individualized based on the patient's specific condition, degree of renal impairment, and overall clinical status.

Monitoring and Adjustment

• Urine output should be monitored closely, and fluid resuscitation adjusted accordingly to achieve the target urine output.
• Other clinical endpoints, such as mean arterial pressure, skin color, and capillary refill, should also be monitored to guide fluid resuscitation.
• The use of dynamic over static variables to predict fluid responsiveness may be helpful in guiding fluid resuscitation 1.

Recent Guidelines

• The 2016 Surviving Sepsis Campaign International Guidelines for Management of Sepsis and Septic Shock recommend an initial target mean arterial pressure of 65 mm Hg in patients with septic shock requiring vasopressors 1.
• The guidelines also suggest guiding resuscitation to normalize lactate in patients with elevated lactate levels as a marker of tissue hypoperfusion 1.

Overall, the target urine output of 0.5 mL/kg/hr is a key component of the initial resuscitation goals in patients with impaired renal function, and should be individualized and adjusted based on the patient's clinical response.

From the Research

Urine Output Targets for Resuscitation

The target urine output to resuscitate a patient with impaired renal function is a crucial aspect of critical care. According to the available evidence:

• A urine output of 0.5 ml/kg/hour for 6 hours is often used as a criterion for acute kidney injury (AKI) 2.
• However, a study suggests that this definition may be too liberal, and a 6-hour urine output threshold of 0.3 ml/kg/hour may be more appropriate for predicting mortality and dialysis need 2.
• Another study found that urine output criteria for AKI as predictors of in-hospital mortality or dialysis need were compared, and the optimal threshold for each collection interval was determined 2.

Factors Influencing Urine Output

Several factors can influence urine output in critically ill patients, including:

• Decrease of glomerular filtration rate due to decrease of renal blood flow or renal perfusion pressure 3.
• Neurohormonal factors and functional changes that may influence diuresis and natriuresis in critically ill patients 3.
• The type of fluid used for resuscitation, with lactated Ringer's solution potentially being superior to normal saline in certain situations 4, 5.

Fluid Resuscitation Strategies

The choice of fluid for resuscitation can impact urine output and patient outcomes:

• Lactated Ringer's solution may be associated with improved survival and more hospital-free days compared to 0.9% saline in patients with sepsis-induced hypotension 4.
• In a swine model of uncontrolled hemorrhagic shock, lactated Ringer's solution was found to be superior to normal saline, with less fluid required to achieve and maintain baseline mean arterial pressure 5.