Why are fluids administered in sepsis?

Why Fluids Are Given in Sepsis

Fluids are administered in sepsis to restore tissue perfusion by correcting hypovolemia caused by vasodilation, venous pooling, and capillary leakage, thereby increasing cardiac output and oxygen delivery to prevent organ dysfunction and death. 1, 2

Pathophysiological Rationale

Sepsis creates a profound intravascular fluid deficit through multiple mechanisms that must be corrected:

• Vasodilation and capillary leak cause fluid to shift from the intravascular space into the interstitium, creating both relative and absolute hypovolemia 1, 3
• Tissue hypoperfusion is a key driver of sepsis-associated organ failure, and restoring adequate perfusion is the primary goal of resuscitation 1, 2
• Increased venous return and cardiac preload from fluid administration enhances cardiac output in fluid-responsive patients, improving tissue oxygen delivery and potentially reversing tissue hypoxia 2

Initial Fluid Resuscitation Strategy

The Surviving Sepsis Campaign provides clear guidance on initial fluid therapy:

• Administer at least 30 mL/kg of crystalloid solution within the first 3 hours of recognizing sepsis with tissue hypoperfusion or septic shock 2, 4, 5
• Crystalloids are the first-choice fluid because they are well tolerated, effective, and inexpensive 1, 5
• Either balanced crystalloids or normal saline can be used, though balanced solutions may be preferred to avoid hyperchloremic metabolic acidosis 4

This fixed initial volume enables clinicians to begin resuscitation promptly while gathering more specific hemodynamic information 2.

Hemodynamic Goals and Endpoints

Fluid therapy should target specific clinical endpoints rather than predetermined protocols:

• Target a mean arterial pressure (MAP) of at least 65 mmHg as the initial hemodynamic goal 1, 5
• Adequate tissue perfusion is the principal endpoint, not specific volume goals 1, 2
• Clinical markers of improved perfusion include normalization of heart rate, improved blood pressure, enhanced mental status, better peripheral perfusion (capillary refill, skin color), and increased urine output (>0.5 mL/kg/h) 1, 5

The 2016 Surviving Sepsis Campaign guidelines moved away from rigid early goal-directed therapy protocols after trials (ProCESS, ARISE, ProMISe) showed that predetermined resuscitation bundles did not reduce mortality compared with usual care 1.

Ongoing Fluid Management

After initial resuscitation, fluid administration requires careful assessment:

• Continue fluid administration using a challenge technique, giving additional fluids only as long as hemodynamic parameters improve 5, 6
• Use dynamic measures of fluid responsiveness (such as passive leg raise, pulse pressure variation) rather than static measures (like central venous pressure) when available 2, 5
• Transition to vasopressors (norepinephrine as first-line) if hypotension persists despite adequate fluid resuscitation 1, 5

Critical Pitfalls and Complications

Excessive fluid administration carries significant risks that must be avoided:

• Fluid overload can cause pulmonary edema, tissue edema, and abdominal compartment syndrome, particularly in patients with intra-abdominal infections 1
• Bowel edema and forced abdominal closure can increase intra-abdominal pressure, leading to intra-abdominal hypertension and abdominal compartment syndrome with multi-organ dysfunction 1
• Large positive fluid balance is associated with worse outcomes in intensive care patients who have already received initial resuscitation 7, 6
• Continued fluid administration after capillary leak develops drives intravascular fluid into the interstitial space, producing marked tissue edema and disrupting vital oxygenation 8

Special Populations

Certain patients require modified fluid strategies:

• Patients with heart failure or low ejection fraction may require smaller fluid boluses with frequent reassessment and earlier initiation of vasopressors 2, 5
• Elderly patients or those with renal impairment are at higher risk for fluid overload and require closer monitoring 2
• Children with compensated shock and profound anemia (particularly with malaria) may not benefit from aggressive fluid boluses, as demonstrated in African studies showing increased mortality with fluid boluses in this specific population 1

Monitoring and De-escalation

Appropriate monitoring prevents complications:

• Monitor for signs of fluid overload including pulmonary crackles, increased jugular venous pressure, and worsening respiratory function 4, 5
• Measure inferior vena cava (IVC) diameter by ultrasound as a simple method for defining ongoing fluid requirements 1
• Facilitate fluid removal (evacuation phase) for patients recovering from acute respiratory distress syndrome, as limiting fluid and administering diuretics improves ventilator-free days 6

The key is recognizing that fluid therapy evolves through phases: resuscitation (rapid administration), optimization (evaluating risks/benefits), stabilization (fluids only with signals of responsiveness), and evacuation (removing excess accumulated fluid) 6.