What is the purpose of administering a fluid bolus (intravenous fluid resuscitation)?

From the Guidelines

The administration of a fluid bolus should be guided by early fluid resuscitation to optimize tissue perfusion targets, without waiting for hemodynamic worsening, using isotonic crystalloids as the preferred fluid 1.

Key Considerations

• The goal of fluid bolus administration is to rapidly restore intravascular volume in patients experiencing hypovolemia, dehydration, or shock.
• For adult patients, the standard fluid bolus is 500-1000 mL of isotonic crystalloid solution, such as 0.9% normal saline or lactated Ringer's solution, administered over 15-30 minutes.
• For pediatric patients, the recommended volume is 20 mL/kg given over the same timeframe.
• When administering a fluid bolus, a large-bore IV catheter (18-gauge or larger in adults) should be used to allow for rapid infusion.
• After administration, the patient's vital signs, including blood pressure, heart rate, capillary refill, urine output, and mental status, should be reassessed to determine if additional boluses are needed.
• Multiple boluses may be required in severe cases of hypovolemia.
• Fluid boluses work by rapidly increasing preload, which improves cardiac output according to the Frank-Starling mechanism, thereby enhancing tissue perfusion and oxygen delivery.
• However, caution is warranted in patients with heart failure, renal failure, or pulmonary edema, as excessive fluid administration can worsen these conditions, and smaller boluses with more frequent reassessment are recommended in these cases.

Important Evidence

• The 2019 WSES guidelines for the management of severe acute pancreatitis recommend early fluid resuscitation to optimize tissue perfusion targets, without waiting for hemodynamic worsening, using isotonic crystalloids as the preferred fluid 1.
• The 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations suggests using an initial fluid bolus of 20 mL/kg for infants and children with shock, with subsequent patient reassessment 1.
• The 2009 clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock recommend rapid fluid boluses of 20 mL/kg (isotonic crystalloid or 5% albumin) to achieve normal perfusion and blood pressure 1.
• The 2012 recommendations for sepsis management in resource-limited settings suggest using adequate tissue perfusion as the principal endpoint of resuscitation, and targeting a systolic arterial blood pressure ≥90 mmHg in adults, as well as normal heart rate and arterial blood pressure in children 1.

From the Research

Fluid Bolus Administration

• The administration of intravenous fluids to support circulation in critically ill patients has been a mainstay of emergency medicine and critical care for decades, especially in patients with distributive or hypovolemic shock 2.
• However, the automatic use of large fluid volumes is being questioned, and analysis from several large trials has shown independent links between volumes of fluid administered and outcome 2.
• Conservative fluid strategies have been associated with lower mortality in trauma patients, and the use of central venous pressure to guide fluid administration has been discredited as an unreliable parameter of volume status or fluid responsiveness 2.

Choice of Fluid

• Lactated Ringer's solution and normal saline are the most widely used isotonic crystalloids for initial fluid resuscitation, but both have clinical limitations 3.
• Bicarbonated Ringer's solution has been shown to provide physiological levels of bicarbonate ions and electrolyte ions, and can be used to supplement missing extracellular fluid and correct metabolic acidosis 3.
• A study comparing lactated Ringer's solution and normal saline for initial fluid resuscitation in sepsis-induced hypotension found that lactated Ringer's solution was associated with improved survival and more hospital-free days 4.

Fluid Resuscitation Strategies

• The use of smaller volumes to perform fluid challenges, monitoring of extravascular lung water, and earlier use of norepinephrine can help reduce morbidity and mortality from severe sepsis 2.
• A study using a canine model of hypovolemic traumatic shock found that albumin and lactated Ringer's solution were approximately equivalent in terms of resuscitation quality, but albumin recipients had better plasma colloid osmotic pressure and less increase in extravascular lung water 5.
• Early IV fluid administration remains an important part of sepsis treatment, but questions remain regarding the optimal amount, type, rate, and mechanism of action of fluid administration 6.
• Assessing fluid responsiveness is crucial in determining further fluid administration, and various static and dynamic measures can be used to evaluate fluid responsiveness 6.