In a dehydrated patient receiving intravenous fluids, which measurement best confirms adequate volume resuscitation: central venous pressure of 8 mm Hg, lactate of 2 mmol/L, or urine output of 0.11 mL/kg per hour?

Confirming Adequate IV Fluid Resuscitation in Dehydration

Urine output >0.5 mL/kg/hour is the primary clinical endpoint for confirming adequate fluid resuscitation, making option C (0.11 mL/kg/hour) clearly inadequate and indicating ongoing under-resuscitation. 1, 2 This patient requires continued aggressive fluid administration.

Why Each Parameter Matters

Urine Output: The Gold Standard

• Target urine output is >0.5 mL/kg/hour for adequate resuscitation 1, 2
• The presented value of 0.11 mL/kg/hour represents oliguric acute kidney injury and signals inadequate volume resuscitation 1
• Urine output remains the easiest and fastest parameter to adjust fluid resuscitation rates in real-time 2
• This patient is producing less than 25% of the minimum acceptable urine output, indicating severe ongoing hypovolemia 1

CVP: Unreliable and Misleading

• CVP of 8 mmHg falls within the "normal" range (8-12 mmHg) where it has <50% positive predictive value for fluid responsiveness 3
• The Surviving Sepsis Campaign explicitly states that using CVP alone to guide fluid resuscitation can no longer be justified 3
• Static indices like CVP fail to predict which patients will benefit from additional fluid 3
• In mechanically ventilated patients, using CVP to direct fluid resuscitation may place patients at risk for under-resuscitation with resultant organ dysfunction and increased mortality 3

Lactate: Important but Incomplete

• Lactate of 2 mmol/L is mildly elevated (normal <2 mmol/L) and suggests some degree of tissue hypoperfusion 2
• Lactate normalization is an important marker of improved tissue perfusion, but serial measurements every 2-6 hours are more valuable than a single value 2
• Lactate should be interpreted alongside other perfusion markers rather than in isolation 2
• A lactate of 2 mmol/L alone does not confirm adequate resuscitation when urine output remains severely depressed 2

Comprehensive Assessment Algorithm

Step 1: Initial Fluid Administration

• Deliver 30 mL/kg of isotonic crystalloid within the first 3 hours for patients with tissue hypoperfusion 1, 2, 4
• Administer fluid in boluses of 250-1000 mL, reassessing after each bolus 4

Step 2: Monitor Multiple Clinical Endpoints Together

• Urine output >0.5 mL/kg/hour (primary endpoint) 1, 2
• Mean arterial pressure ≥65 mmHg 1, 2
• Lactate normalization (trending toward <2 mmol/L) 2
• Clinical perfusion markers: normalized heart rate, improved blood pressure, warm skin with capillary refill <2 seconds, reduced mottling, improved mental status 1, 2, 4

Step 3: Use Dynamic Assessment, Not Static Pressures

• After initial bolus, perform passive leg raise (PLR) test: a ≥10-15% increase in stroke volume or cardiac output indicates fluid responsiveness 3, 4
• Do not target specific CVP values as therapeutic goals, as this may lead to inappropriate fluid administration 3
• Dynamic measures have superior diagnostic accuracy (positive likelihood ratio = 11, specificity = 92%) compared to CVP 3, 4

Step 4: Continue Fluid Until Endpoints Are Met

• Continue fluid administration as long as objective perfusion parameters improve 4
• The rate of fluid administration must exceed the rate of continued losses (urine output + insensible losses of 30-50 mL/hour + gastrointestinal losses) 1
• More than 4 L during the first 24 hours may be required for adequate resuscitation 1

Critical Pitfalls to Avoid

• Never rely on CVP alone when values fall in the 8-12 mmHg range—this is where CVP is most unreliable 3
• Do not stop fluid resuscitation prematurely based on a "normal" CVP when urine output remains inadequate 3
• Avoid rapid large volume loads based solely on low static pressures without reassessing clinical response 3
• In elderly patients or those with heart/kidney disease, monitor closely for signs of fluid overload (elevated JVP, pulmonary crackles, peripheral edema) 1, 4

Answer to the Question

None of the three options alone confirms adequate fluid resuscitation, but option C (urine output 0.11 mL/kg/hour) definitively confirms INADEQUATE resuscitation. 1, 2 This patient requires:

• Continued aggressive fluid boluses 1, 4
• Reassessment after each bolus using clinical perfusion markers 4
• Target urine output >0.5 mL/kg/hour as the primary endpoint 1, 2
• Ignore the CVP of 8 mmHg—it provides no useful information in this context 3
• Monitor lactate trends alongside other markers 2