Definitions 

• Crystalloids: IV fluids composed of water and electrolytes. 
• Colloids: IV fluids composed with larger macromolecules or particles that are relatively membrane-impermeable (e.g., albumin, red blood cell substitutes, Hextend/hetastarch). For use of blood products as a colloid, please see section Critical Care: Transfusion Strategies in the ICU. 

Contents of Commonly Used Fluids 

Colloid vs Crystalloid 

• Albumin vs crystalloid: 
  • CRISTAL study (2013): RCT of 2800 patients with hypovolemic shock randomized to NS vs colloid solutions (albumin, gelatin, hetastarch). No difference in 28 day mortality or need for RRT. Patients in the colloid group had more days of mechanical ventilation and vasopressors. 
  • SAFE study (2004): RCT of 7000 MICU and SICU patients that showed similar outcomes at 28 days (no difference in mortality, organ failure, duration of intubation, duration of renal-replacement therapy, duration of ICU or hospital stay) in patients treated with 4% albumin or normal saline. In subgroup analysis, there may be a benefit in early resuscitation with severe sepsis. 
  • Cochrane review of 36 RCTs comparing crystalloid and colloid (albumin, plasma protein fraction, hydroxyl starch, dextran, modified gelatin) found no difference in mortality. 
  • There are data that show a survival benefit from 25% albumin in patients with cirrhosis with spontaneous bacterial peritonitis (SBP). 
• Semisynthetic colloids (hydroxyethyl starch, tetraspan, voluven): cheaper than albumin, but multiple studies have shown either increased mortality (6S trial) or increased RRT (CHEST). 
• Chloride-liberal vs chloride-restrictive: prospective cohort study in JAMA showed chloride restrictive fluids (Plasma-Lyte, LR) in ICU patients showed decreased AKI and RRT compared to chloride-rich solutions (NS, albumin). 

NS vs Buffered Solutions  

• Lactated Ringers (LR) and Plasma-Lyte are isotonic fluids that are called buffered, balanced, or chloride-restrictive crystalloids. 
• NS (0.9% saline) is the most commonly used initial fluid due to its low cost, availability, and lack of strong evidence for benefit of buffered solutions with small volume (<2L) administration. 
• The type of fluid and rate should be individualized for each patient with frequent reassessment to see if a change in fluid is needed during their treatment course.  
• SMART trial (2018): 15,000 ICU adult patients with data that suggests a mortality benefit when balanced solutions are used over NS for critically-ill patients as well as reduction in new RRT or persistent renal dysfunction. 

Special Situations  

• Sepsis: 
  • Surviving Sepsis: 30cc/kg crystalloid infusion for hypotension or lactate >4. 
  • Balanced fluids (LR or Plasma-Lyte) are the preferred crystalloid over NS given reduced mortality and RRT. 
  • After initial fluid resuscitation, additional fluid needs are determined based on clinical response using capillary refill rate, BP response, PPV, UOP and other dynamic assessments of fluid responsiveness. 
    • If inadequate response to fluids and patient remains hypotensive, then recommendation includes initiation of vasopressors. 
    • Consider patient-specific co-morbidities such as CHF, cirrhosis, ARDS when determining optimal fluid resuscitation and the risk/benefit of additional fluids. 
• DKA/HHS: 
  • Both DKA and HSS are volume-depleted states and require isotonic fluids (Plasma-Lyte or NS) for resuscitation.  
    • Patients with DKA are often 3-8L depleted whereas HHS can range from 5-10L. 
  • The rate of fluid administration depends on several clinical factors including volume status and the degree and types of electrolyte derangements; thus, DKA/HHS management requires frequent reassessment of hemodynamics, clinical status, as well as electrolytes and FSG. 
• Acute pancreatitis: 
  • There is no consensus on the optimal type of fluid for resuscitation:  
    • Crystalloid is the preferred fluid type without convincing mortality data to suggest NS over balanced fluids. 
    • There is some data to suggest LR is the preferred fluid in pancreatitis.  
      • Note: not used when pancreatitis is due to hypercalcemia given LR contains some Ca. 
  • Rate of fluid resuscitation and type of fluid to administer remains an area of debate and ongoing investigation: 
    • Most guidelines suggest ~4L in the first 24 hours divided into initial and subsequent phases with close monitoring of response as well as taking into account patient-specific factors and co-morbidities where aggressive fluid administration would potentially lead to more harm.  
    • Initial: 20-30 cc/kg in the first 30 minutes. 
    • Subsequent: 3 cc/kg/hr.  

Key Points 

• In general, crystalloid is preferred over colloid for resuscitation in the critically ill. 
• Isotonic, balanced salt solutions should be considered for the majority of acutely ill patients. 
• Semisynthetic colloids should not be used in sepsis or patients at risk of AKI. 
• There is no strong evidence to use albumin in critically ill patients. 

6S Trial Group and the Scandinavian Critical Care Trials Group. Hydroxyethyl Starch 130/0.42 versus Ringer's Acetate in Severe Sepsis. N Engl J Med 2012. 367:124-134 

CRISTAL: Annane D, et al. Effects of fluid resuscitation with colloids vs. cyrstalloids on mortality in critically ill patients presenting with hypovolemic shock. JAMA. 2013; 310(17):1809-17. 

Myburgh JA, Finfer S, Bellomo R, et al. Hydroxyethyl starch or saline for fluid resuscitation in intensive care. N Engl J Med 2012; 367:1901-11 

Myburgh JA, Mythen MG. Resuscitation Fluids. N Engl J Med 2013;369:1243-51 

Petel R, Roberts I, Pearson M. Colloids versus crystalloids for fluid resuscitation in critically ill patients. Cochrane Database of Systematic Reviews 2007.  

SAFE Study Investigators.  A comparison of albumin and saline for fluid resuscitation in the intensive care unit. N Engl J Med 2004;350(22):2247-2256. 

SMART: Semler, MW, et al. “Balanced Crystalloids versus Saline in Critically Ill Adults”. N Engl J Med. 2018; 378(9):829-839. 

Yunos N, Bellomo R, et al. Association Between a Chloride-Liberal vs Chloride-Restrictive Intravenous Fluid Administration Strategy and Kidney Injury in Critically Ill Adults. JAMA 2012; 308(15):1566-1572