Posted by:John Ellis
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A recent article in JAMA, a randomized trial in hypovolemic shock found pretty equivalent results for colloids vs crystalloids.  The colloids were a mixed-bag (gelatins, dextrans, hydroxyethyl starches, or 4% or 20% of albumin), as were crystalloids (isotonic or hypertonic saline or Ringer lactate solution).  They noted:

Conclusions and Relevance  Among ICU patients with hypovolemia, the use of colloids vs crystalloids did not result in a significant difference in 28-day mortality. Although 90-day mortality was lower among patients receiving colloids, this finding should be considered exploratory and requires further study before reaching conclusions about efficacy.

However, we know that not all colloids are alike; hetastarch has been associated with renal injury, coagulopathy, and death.  Additionally, NS may produce a hyperchloremic acidosis, and has also been linked to bad outcomes.

In an accompanying editorial, the authors note:

“And there may be no definitive answer to the question of whether patients with hypovolemic shock should preferentially receive colloids or crystalloids.”

Some of our notions about the differences between crystalloid and colloid may be wrong. For example, in an NEJM REVIEW ARTICLE: Resuscitation Fluids, the authors point out that the traditionally-accepted 1:3 ratio of colloid to crystalloid for volume replacement is false.  Some studies have found that the ratio is only 1:1.4!

In a recent review on septic shock in the NEJM, the authors comment what’s been the same for some time:

The exact components required to optimize resuscitation, such as the choice and amount of fluids, appropriate type and intensity of hemodynamic monitoring, and role of adjunctive vasoactive agents, all remain the subject of ongoing debate and clinical trials; many of these issues will be covered in this series.

Others would argue that the type of fluid is less important than WHEN and HOW it’s administrated; i.e., goal-directed administration.

“Early goal-directed hemodynamic therapy based on cardiac index, stroke volume variation, and optimized global end-diastolic volume index reduces complications and length of ICU stay after cardiac surgery.”

Other studies have suggested that fluid RESTRICTION improves outcome.  This has been shown in septic children in third world settings, in patients suffering penetrating trauma, and in elective colorectal surgery. Perhaps fluid should be restricted to be given when indicated by low pulse-pressure variation or other signs of fluid-responsiveness?

There’s also no doubt that the clinical scenario matters.  A given amount fluids that might be particularly harmful in the setting of brain swelling or poor lung function, might be helpful in other patient scenarios.

I think things are no more clear than when I started residency 30 years ago!

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