We would like to thank Hahn1 for his comments concerning our recently published trial on the effects of goal-directed fluid therapy on microcirculation during free flap surgery.2 We assume that most clinicians are using crystalloids, while some, like Dr Hahn, prefer colloids for their better volume : replacement ratio.
Basically, both crystalloids and colloids are suitable for fluid resuscitation. According to Starling's ‘3-compartment model’, crystalloids are distributed in the extracellular space, while colloids should remain intravascularly due to their large molecular weight. However, clinical trials seem to disprove this principle as we do not see this large difference in the required volume of crystalloids versus colloids to stabilise patients. Published data have shown a strong association between acute kidney injury, an increased use of renal replacement therapy and the use of hydroxyethyl starch solution, which was also accompanied with unfavourable patient outcome.3–5 However, in these trials, the ratios of the administered volume of crystalloids and colloids were completely different to what should have been expected according to the Starling principle. Theoretically, colloids have better volume expansion effects, therefore they restore the circulating blood volume and hence DO2 faster than crystalloids do. A fluid challenge study shows that fluid responsiveness is time-dependent and that the issue of optimal timing needs to be addressed. Roger et al.6 aimed to evaluate whether echocardiographic assessment of the response to fluid challenge could affect the results by crystalloid solutions. In this study, 51.3% of initial responders had a persistent response to fluid 30 min after the beginning of fluid infusion and only 41.3% had a transient response.5 However, fluid therapy, a main component of resuscitation, may cause substantial endothelial injury.7 Preclinical studies show that fluid resuscitation degrades the endothelial glycocalyx structure. The volume of intravenous fluids during resuscitation is associated with the degree of glycocalyx degradation. These findings suggest a potential mechanism which may induce iatrogenic endothelial injury.
In our moderate bleeding-resuscitation animal model, the volume: replacement ratio for crystalloids and colloids followed similar patterns as predicted by Starling's principle, and the glycocalyx remained intact.7
Our study's main finding is that when fluid management is guided by detailed haemodynamic assessment, more crystalloid than colloid is needed to maintain haemodynamic stability. We did not find any difference between the effects of crystalloids and colloids on the microcirculation. Crystalloids actually have a worse volume : replacement ratio than colloids, therefore complex monitoring is essential for decision-making. Our results raise a point that personalised therapy may be superior to guidelines/bundles- driven management, which assumes the ‘one size fits all’ paradigm, and leaves the question on the crystalloid-colloid debate open.8
Acknowledgements relating to this article
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1. Hahn RG. Crystalloids should be second choice for goal-directed fluid therapy. Eur J Anaesthesiol
2. László I, Janovszky Á, Lovas A, et al. Effects of goal-directed crystalloid vs. colloid fluid therapy on microcirculation during free flap surgery: a randomised clinical trial. Eur J Anaesthesiol
3. Brunkhorst FM, Engel C, Bloos F, et al. Intensive insulin therapy and pentastarch resuscitation in severe sepsis. N Engl J Med
4. Perner A, Haase N, Guttormsen AB, et al. Hydroxyethyl starch 130/0.42 versus Ringer's acetate in severe sepsis. N Engl J Med
5. Myburgh JA, Finfer S, Bellomo R, et al. Hydroxyethyl starch or saline for fluid resuscitation in intensive care. N Engl J Med
6. Roger C, Zieleskiewicz L, Demattei C, et al. Time course of fluid responsiveness in sepsis: the fluid challenge revisiting (FCREV) study. Crit Care
7. Hippensteel JA, Uchimido R, Tyler PD, et al. Intravenous fluid resuscitation is associated with septic endothelial glycocalyx degradation. Crit Care
8. László I, Demeter G, Öveges N, et al. Volume-replacement ratio for crystalloids and colloids during bleeding and resuscitation: an animal experiment. Intens Care Med Exp