Cristalloïde/Colloïde ration; Plutôt 1,5 que 4

Crystalloids Versus Colloids: Exploring Differences in Fluid Requirements by Systematic Review and Meta-Regression

Orbegozo Cortés D. et Al. Anesth Analg 2015;120:389–402

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Le débat qui porte sur l'efficacité comparée des solutés de remplissage n'est pas nouveau. Cette méta-analyse porte sur l'analyse de 27 publications sélectionnées parmi 978. Elle met en évidence la très grande hétérogénéité des données publiées. Les raisons avancées portent sur la nature des populations étudiées (fuite capillaire très variable), l'administration préhospitalière de fluides à des volumes mal connu ce qui va compliquer l'analyse ultérieure, les différences de pharmacodynamie et cintétique des différents solutés employés, le fait que pour un même soluté l'efficacité en terme de remplissage puisse varier en fonction du moment de son administration, Qui qu'il en soit il semble que le ratio actuel soit plus proche de 1,5 que de 4.

On rappelle que la procédure du sauvetage au combat met en avant l'emploi de soluté salé hypertonique en première intention (250 ml en 10 minutes) suivi de 500ml de colloïdes (à défaut 250 ml de salé hypertonique) en cas de non restauration du pouls radial. Ce choix est résulte d'un compromis dans lequel le poids des solutés est pris en compte.

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BACKGROUND:

Positive fluid balance has been associated with worse outcomes, and knowledge of differences in the amounts of different types of fluid needed to achieve the same end points may have important clinical implications. Large molecules persist longer in the blood vessels than smaller molecules, such that less IV colloid may be needed to achieve similar hemodynamic end points compared with crystalloid. Recent clinical data have, however, challenged this physiological concept, with investigators reporting lower-than-expected crystalloid/colloid ratios in various populations.

METHODS:

We performed a systematic search in MEDLINE, EMBASE, and CENTRAL up to December 18, 2013, to retrieve all studies comparing (any) crystalloid with (any) colloid in all types of patients. The crystalloid/colloid ratio was calculated for each study. Descriptive analysis was performed for all studies, and a meta-analysis was performed in those studies reporting full data (in terms of means and standard deviations) of infused fluid volumes. Studies were grouped according to study and population characteristics. A meta-regression analysis was then performed to evaluate some of the possible reasons for differences in crystalloid/colloid ratios across studies.

RESULTS:

From 976 studies, 48 were retained for the final analysis; 24 of the studies had sufficient data for meta-analysis. The crystalloid/colloid ratio across all the studies included in the meta-analysis was 1.5 (95% confidence interval, 1.36–1.65) with marked heterogeneity among studies (I2 = 94%). From the meta-regression analysis, decade of publication across all publications (P = 0.001) and concentration (tonicity) in the subgroup of albumin studies (P = 0.001) were associated with the administered crystalloid/colloid ratio. The reduction in heterogeneity among studies for all publications in the meta-regression was minimal, with the maximal decrease obtained when decade of publication was considered (R2 = 12%).

 

CONCLUSIONS:

Greater fluid volumes are required to meet the same targets with crystalloids than with colloids, with an estimated ratio of 1.5 (1.36–1.65), but there is marked heterogeneity among studies. The crystalloid/colloid ratio seems to have decreased over the years, and differences in ratios are correlated with the concentration of albumin solutions; however, the main reasons behind the high heterogeneity among studies remain unclear.