• Fluid resuscitation is critical in the treatment of patients with volume depletion, simultaneous with identification and treatment of the underlying cause.
• The goal of fluid resuscitation is to reestablish tissue oxygenation.  Oxygen delivery depends on many factors with cardiac output being key.  Intravenous (IV) fluids increase left ventricular preload and hence stroke volume, in fluid responsive patients.
• Aggressive fluid resuscitation can have negative consequences of volume overload as well as acid-base and electrolyte abnormalities.
• As poor tissue perfusion is often multifactorial (especially in the critically ill), every patient responds differently to fluid challenges, with reports indicating that less than half of patients with vasopressor-dependent shock being fluid responsive.

• Clinical exam does not reliably indicate who will respond best to fluids but is the best tool we have currently (refractory shock needs invasive monitoring).
  • Rapid Ultrasound for Shock (RUSH) exam helps evaluate cause of hypotension. Use HI-MAP approach (heart, IVC, Morison’s pouch, aortic aneurysm, pneumothorax).
    • Studies are inconclusive on whether the IVC variability is accurate
  • Other noninvasive methods of evaluation such as Passive Leg Raising and End-Tidal Co2 monitoring are still being evaluated.
• In general, resuscitate to mean arterial pressure (MAP) ≥ 65 mmHg using fluids +/- vasopressor support:
  • Lower MAP in patients with uncontrolled bleeding without severe head injury3, until bleeding is surgically controlled.
  • Higher MAP should be targeted in septic patients with history of hypertension, or if clinical improvement demonstrated with higher MAP.
• In septic patients, ≥ 30 mL/kg of crystalloid fluid is recommended in initial 3 hours.
• Elevated lactate levels may be used to guide initial resuscitation, serial measurements recommended.
• Add vasopressor if signs of hypoperfusion persist after preload optimization.

For resuscitations < 2 litres, there is no preferred fluid choice.

Beyond 2 litres, existing evidence indicates that Plasmalyte and Lactated Ringers (LR) are both superior to Normal Saline resulting in improved acid-base status and less hyperchloremia.  It is less clear how Plasmalyte compares to LR.

Lactated Ringer’s (LR)
Lactated Ringer’s (LR) with a chloride concentration of 109 mEq/L, does not lead to hyperchloremic metabolic acidosis unlike normal saline (154 mEq/L). Lactate is also converted to bicarbonate in the liver, which in theory helps with acidosis if liver functional (i.e. sepsis).

• However, the calcium in LR causes drug interactions, including aminocaproic acid, amphotericin, ampicillin and thiopental and precludes its use as a diluent for RBC transfusions.

Normal Saline (NS)
Normal Saline (NS) is preferred in patients with neurological insults (TBI, stroke, SAH) requiring rehydration; LR can promote brain swelling.

• With normal saline (NS), risk of developing hyperchloremic metabolic acidosis.
• NS is also the choice for rapid resuscitation; with rapid/high volume fluid resuscitation, the presence of K+ in LR can lead to hyperkalemia and potential life-threatening arrhythmia.

Plasmalyte
Compared with NS, Plasmalyte has shown improved acid-based status and reduced hyperchloremia when used in initial resuscitation of trauma patients. Some studies have shown Plasmalyte to have more rapid resolution of metabolic acidosis and lower hyperchloremia compared to NS in DKA.

Colloid
In septic shock patients requiring substantial ongoing volumes of crystalloid, the addition of albumin may be considered in consultation with ICU.

• Fluid resuscitation guided by multiple hemodynamic variables, ideally using dynamic measurements and should be measured in a sequential manner.
• Instructions for measuring and interpreting pulse pressure variation can be found at acep.org.
• If test for fluid responsiveness is negative, consider vasopressor use.
• If test for fluid responsiveness is positive, and patient has low cardiac output that requires correction, fluid management needs to be carefully titrated to individual patients. Cutoff values in literature have wide confidence intervals, suggesting that decision to administer fluid should be decided in consideration of both fluid responsiveness test results and clinical context.

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3. Cecconi, M. et al. Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine. Intensive Care Med. 40, 1795–1815 (2014).

   
   

4. Rhodes, A. et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016. Intensive Care Med. 43, 304–377 (2017).

   
   

5. Marino, P. L. The ICU Book, 3rd Edition. (Lippincott Williams and Wilkins, 2007).

   
   

6. Young, J. B. et al. Saline versus plasma-lyte A in initial resuscitation of trauma patients: A randomized trial. Ann. Surg. 259, 255–262 (2014).

   
   

7. Oliver, W. D., Willis, G. C., Hines, M. C. & Hayes, B. D. Comparison of Plasma-Lyte A and Sodium Chloride 0.9% for Fluid Resuscitation of Patients With Diabetic Ketoacidosis. Hosp. Pharm. 53, 326–330 (2018).

   
   

8. Chua, H. R. et al. Plasma-Lyte 148 vs 0.9% saline for fluid resuscitation in diabetic ketoacidosis. J. Crit. Care. 27, 138–145 (2012).

   
   

9. Mahler, S. A., Conrad, S. A., Wang, H. & Arnold, T. C. Resuscitation with balanced electrolyte solution prevents hyperchloremic metabolic acidosis in patients with diabetic ketoacidosis. Am. J. Emerg. Med. 29, 670–674 (2011).

   
   

10. Bentzer, P. et al. Will this hemodynamically unstable patient respond to a bolus of intravenous fluids? JAMA – Journal of the American Medical Association vol. 316 1298–1309 (2016).

    
    

11. Winters, M. E., Sherwin, R., Vilke, G. M. & Wardi, G. What is the Preferred Resuscitation Fluid for Patients with Severe Sepsis and Septic Shock? J. Emerg. Med. 53, 928–939 (2017).