Kevin Kuruvilla, MD
Background
Volume repletion plays a key role in the resuscitation of hypotensive patients in the surgical ICU. The three main categories of fluids used for volume resuscitation are crystalloids (Ringer’s lactate, normal saline), colloids (albumin, hetastarch, dextran), and blood products. The choice of fluids used to resuscitate patients with shock in the ICU has been a subject of much debate.
Normal saline
Normal saline(NS) is one of the most common crystalloid fluids used. Historically normal saline was thought to be superior to other crystalloids but recent data suggests otherwise. Normal saline has a high chloride content relative to a patient’s plasma which increases the risk of hyperchloremic metabolic acidosis. This is a non-anion gap acidosis which can be corrected fairly readily if needed with D5W NaHCO3. Compared to other crystalloids normal saline also increases interstitial edema. Studies have also shown decrease in renal perfusion associated with normal saline use through tubular vasoconstriction and decreased GFR. Acidosis associated with saline can also cause potassium shift into the blood causing hyperkalemia.
Two randomized clinical trials were published in 2018.
SALT-ED: Compared NS to balanced crystalloids for noncritically ill adults in the ER. Higher rates of adverse kidney events with saline within 30 days.
SMART: 5 ICUs, more than 15k patients. Higher rates of adverse kidney events with saline within 30 days.
Also consider reviewing: PulmCrit’s entry “Get SMART: Nine reasons to quit using normal saline for resuscitation” http://emcrit.org/pulmcrit/smart/
Ringer’s Lactate
Ringer’s lactate (LR) is another commonly used crystalloid in the ICU. Compared to normal saline, LR has a lower sodium and chloride content and is associated with less risk of causing acidosis. Even though LR has higher potassium content than normal saline, the amount of potassium is so low that is unlikely to cause hyperkalemia. LR is safe to use in patients with renal failure. Even in patients with liver failure use of LR is unlikely to cause lactic acidosis. One potential disadvantage of LR is its lower osmolality and hence it should be used with caution in patients with traumatic brain injury.
| Fluid | Na | Cl | K | Ca | pH | Osmolality |
| Plasma | 140 | 103 | 4 | 4 | 7.4 | 290 |
| NS | 154 | 154 | 5.7 | 308 | ||
| LR | 130 | 109 | 3 | 3 | 6.5 | 273 |
Albumin
Albumin is a human derived colloid and accounts for approximately 80% of oncotic pressure. It is often thought to be superior to crystalloids in expanding intravascular volume. However historical studies have failed to show superiority of albumin over crystalloids when used as the sole fluid for resuscitation (Br Med Journal 1998, SAFE Trial NEJM 2004). In inflammatory or septic states with loss of endothelial integrity, albumin will still leak readily from capillaries.
The ALBIOS trial from 2018 compared crystalloids alone vs. crystalloids and 20% albumin in patients with severe sepsis or septic shock. There was no survival difference. It showed that vasopressors were weaned faster in the albumin group. At RIH albumin comes as a 5% solution (50g/L, 250mL aliquots) and a 25% solution (250g/L, 50mL aliquots).
Albumin may also be useful in reducing total amount of fluid adminstered to a patient with septic shock undergoing significant resuscitation.
Conclusion
LR is a superior crystalloid fluid compared to NS for volume resuscitation in the SICU. NS will remain the initial fluid for trauma patients in the ER who may have TBI. Albumin when used in conjunction with crystalloids for resuscitation may have some benefits.