Does the choice of colloids interfere with the outcome in critically ill patients? A critical appraisal.

In this issue of the Journal, fluid management has been discussed in terms of a restricted or liberal approach.[1] Actually, two aspects have to be highlighted in this context:

Acute caregivers will inherently restrict fluids in patients at risk for edema (cerebral or pulmonary edema, acute respiratory distress syndrome, cardiac decompensation).

The discussion between liberal and restrictive management devolves to high volume resuscitation by crystalloids versus low volume optimization by colloids.

A restrictive policy appears logical when patients are at risk for developing edema or in whom restrictive fluid administration permits established homeostasis and stable hemodynamics without deterioration of renal function. The efficiency of low volume of colloids has been demonstrated in several settings, such as acute normovolemic hemodilution,[2] before and during spinal anesthesia (coloading or preloading, respectively)[3] and reversal of shock.[4] Therefore, a restrictive attitude is desirable, avoiding over-optimization of preload and blind correction of fluid responsiveness.

Nowadays, there is a debate on the use of hydroxy-ethyl starches (HES) in critically ill patients, especially in those with septic shock. Literature appears to blame HES containing colloids for most of the harmful effects. Several studies in the critical care setting demonstrated either no benefit or harm of HES. However the use of HES solutions and hyperoncotic solutions in septic shock and burn patients,[5] leads more frequently to acute kidney injury.[67] This was true not only in the few patients in whom cumulative doses exceeded 250 ml/kg of HES,[5] but also when recommended doses were administered. Furthermore, coagulopathy has been described in some studies,[78] but denied by others,[9] and is attributed to dilutional hypofibrinogenemia.[1011] It seems that main effects are closely related to the cumulative dose of the colloid.

These and other findings led to the publication of warnings and recommendations by European and American authorities, stating that HES is contraindicated in sepsis and burns, as well as in severe coagulopathy and liver dysfunction.[12] In perioperative care, HES solutions continue to be used in the setting of acute hypovolemia, in the absence of renal failure or significantly increased bleeding risk, though they are not really advantageous.[13] The corner stone in this debate is the correct use of HES with respect to a maximal dosing per 24 h (30 ml/kg/day HES 6%). In any case, a cautious and judicious use of these and other hyperoncotic solutions is warranted: Colloids are drugs, they have indications, maximum dose, and well-defined contraindications. Further studies have to elucidate their safety and harm in the perioperative setting.