How can I determine whether a patient requires fluid therapy and which type of fluid is appropriate?

Determining Fluid Requirements and Selecting Appropriate Fluids

Assess for hypovolemia using specific clinical criteria, then administer isotonic crystalloids as first-line therapy, titrating to hemodynamic response while monitoring closely for fluid overload.

Initial Assessment: Determining if Fluid is Required

For Septic Shock Patients

• Administer at least 30 mL/kg of crystalloid within the first 3 hours if sepsis-induced hypoperfusion or septic shock is present 1, 2
• This equals approximately 2,100 mL for a 70 kg patient and should be given even before complete assessment is finished 3
• More rapid administration and greater volumes may be needed in some patients beyond this initial bolus 1, 2

For Volume Depletion from Blood Loss

• Postural pulse change ≥30 beats/minute from lying to standing indicates significant volume depletion (97% sensitive, 98% specific when blood loss ≥630 mL) 1
• Severe postural dizziness preventing standing is equally diagnostic 1
• Note: These findings are less reliable in older adults taking beta-blockers 1

For Volume Depletion from Vomiting/Diarrhea

• Presence of ≥4 of these 7 signs indicates moderate-to-severe volume depletion: 1
  • Confusion
  • Non-fluent speech
  • Extremity weakness
  • Dry mucous membranes
  • Dry tongue
  • Furrowed tongue
  • Sunken eyes

For Dehydration (Water Loss)

• Serum osmolality >300 mOsm/kg (or calculated osmolarity >295 mmol/L) in patients unable to drink warrants IV fluid consideration 1

Hemodynamic Indicators

• Persistent hypotension despite initial resuscitation requires continued fluid assessment 1, 2
• Decreased venous filling (empty veins) and low blood pressure suggest hypovolemia 1

Which Fluid to Administer

First-Line Choice: Crystalloids

Crystalloids are the fluid of choice for initial resuscitation and subsequent volume replacement in all patients with sepsis, shock, or volume depletion 1, 2, 3

Specific Crystalloid Selection

• Balanced crystalloids (Lactated Ringer's or Plasma-Lyte) are preferred over normal saline to reduce hyperchloremic acidosis and potentially lower mortality 3
• Isotonic crystalloids should be used for volume depletion from any cause 1
• Isotonic or slightly hypotonic fluids are ideal for electrolyte replacement 1

Administration Routes (in order of preference)

• Oral rehydration solutions when patient can tolerate 1
• Nasogastric if oral not feasible 1
• Intravenous for severe depletion or when large volumes needed rapidly 1
• Subcutaneous as alternative route 1

When to Consider Albumin

• Add albumin to crystalloids when patients require substantial amounts of crystalloids (weak recommendation) 1, 2
• Albumin may have beneficial effects in sepsis beyond volume expansion 1
• Do NOT use albumin as sole protein source in chronic hypoproteinemia, cirrhosis, or malnutrition 4

Fluids to AVOID

• NEVER use hydroxyethyl starches - they increase mortality and acute kidney injury risk 1, 2, 3
• Avoid gelatins - crystalloids are preferred 1

How to Administer Fluids

Fluid Challenge Technique

Continue fluid administration as long as hemodynamic factors continue to improve 1, 2, 3

Bolus Strategy

• Give 250-500 mL crystalloid boluses over 15-30 minutes in standard cases 1
• Give 500 mL over <15 minutes in high-lactate septic patients 1
• Reassess after each bolus rather than giving full calculated volume upfront 1, 2

Monitoring Response

After each bolus, evaluate these tissue perfusion markers: 2

• Mental status improvement
• Urine output increase
• Peripheral perfusion (capillary refill, skin temperature)
• Heart rate reduction ≥10% 3
• Blood pressure increase ≥10% 3

Dynamic Assessment (when available)

• Pulse pressure variation 1, 2
• Stroke volume variation 1, 2
• These are preferred over static measures like central venous pressure 2, 3

Critical Stopping Points: When to STOP Fluids

Signs of Fluid Overload - STOP IMMEDIATELY

Discontinue fluid administration if any of these develop: 1, 2, 3

• Pulmonary crackles/crepitations
• Increased jugular venous pressure
• Worsening respiratory function or declining oxygen saturation
• Increased work of breathing
• No improvement in tissue perfusion despite continued fluid 1, 2

Special Populations Requiring Caution

In patients with cardiac dysfunction or congestive heart failure: 1, 2, 3

• Use smaller boluses (250-500 mL) with more frequent reassessment 1, 2
• Monitor closely for signs of overload after each bolus 2, 3
• Do not withhold all fluids - limited monitored challenges remain appropriate 2, 3
• Consider early vasopressor initiation if hypotension persists 2, 3

In patients with non-collapsing, congested IVC on ultrasound: 2

• This indicates elevated right atrial pressure and volume overload risk 2
• Titrate fluids carefully even if patient appears fluid-responsive 1, 2

When to Initiate Vasopressors

Start norepinephrine (first-choice vasopressor) targeting MAP ≥65 mmHg if hypotension persists after adequate fluid resuscitation 1, 2, 3

• In cardiac dysfunction with venous congestion, consider earlier vasopressor initiation with limited fluid volumes 2
• The CLOVERS trial (2023) showed restrictive fluid strategy with early vasopressors resulted in ~2.1 L less fluid with no mortality difference 2
• Administer via central line when available; peripheral administration acceptable initially 1, 2

Common Pitfalls to Avoid

• Do not delay initial resuscitation due to concerns about fluid overload in septic patients - delayed resuscitation increases mortality 3
• Do not rely on CVP alone to guide fluid therapy - it has poor predictive ability for fluid responsiveness 2, 3
• Do not give the full 30 mL/kg upfront in patients with cardiac dysfunction - use incremental boluses with reassessment 1, 2
• Do not continue fluids when perfusion fails to improve - this leads to harmful fluid accumulation 1, 2
• Do not use oral medications during active vomiting - use IV, sublingual, rectal, or nasal routes 5
• Do not estimate blood loss from suction devices alone in the operating room - these estimates are often inaccurate 6