Journal Information
Vol. 47. Issue 5.
Pages 301-302 (May 2023)
Letter to the Editor
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Saline, balanced solutions and Thomas Bayes
Suero salino, soluciones balanceadas y Thomas Bayes
Alejandro González-Castroa,
Corresponding author

Corresponding author.
, Vicente Modesto i Alapontb, Raquel Ferrero-Francoc
a Servicio de Medicina Intensiva, Hospital Universitario Marqués de Valdecilla, Santander, Spain
b UCI Pediátrica, Hospital Universitario La Fe, Valencia, Spain
c DUE Servicio Cántabro de Salud, Santander, Spain
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Dear Editor:

Since the publication of the study “SMART: Is saline on the tightrope?1, several authors have worked with the hypothesis that the infusion of balanced solutions in critical patients improves the outcomes in terms of renal function and mortality (Table 1). No studies have evidenced benefit from the use of saline solution; in the best of cases, performance has been reported to be equivalent2.

Table 1.

Principal characteristics of randomized controlled studies comparing 0.9% saline solution versus balanced solutions in critical patients after 2018.

Author, year  Name of study  Country  Patients randomized to SS 0.9%  Patients randomized to BS  Type of balanced solution  Follow-up 
Semler, 2018  SMART  USA  1169  1167  RL or ABS  30 days 
Pagano, 2020    Italy  49  35  RL  – 
Golla, 2020    India  80  80  RL  30 days 
Zampieri, 2021  BaSICS  Brazil  1017  1987  ABS  90 days 
Finfer, 2022  PLUS  Australia and New Zealand  1026  1068  ABS  90 days 

RL: Ringer lactate; BS: balanced solution; ABS: acetate balanced solution; SS 0.9%: 0.9% saline solution

A recent systematic review has been made of randomized clinical trials comparing balanced crystalloids with saline solution in adult critical patients, with 90-day mortality as the primary endpoint. The frequency statistics analysis revealed no significant differences. However, Bayesian analysis showed the posterior probability that balanced crystalloids reduce mortality to be 89.5%3.

Physicians naturally use the Bayes theorem in decision-making referring to patient diagnosis, prognosis and treatment. Based on an effect, we decide on the cause of the effect and intuitively assign a probability to the cause we are considering. Different information sources added in sequence – development of hyperchloremia, acidosis, renal failure – define in an increasingly precise way the probability of a certain cause, and always on an intuitive basis4. However, when considering research methodology, priority is given to the simplicity of being able to decide whether a treatment, a diagnostic method or a procedure is effective or not, based on a pre-established p < 0.05. The problem is that the p-value, which is no more than a tool used to quantify such uncertainty, is too often overvalued and misinterpreted.

A. González-Castro, M. Ortiz-Lasa, J. Bada da Silva.
SMART: Is saline on the tightrope?.
Med Intensiva (Engl Ed), 42 (2018), pp. 394-395
L. Muller, O. Joannes-Boyau.
Isotonic saline, balanced fluids, and chloride toxicity in ICU: Lessons from the PLUS trial.
Anaesth Crit Care Pain Med, 41 (2022),
N.E. Hammond, F.G. Zampieri, G.L.D. di Tanna, T. Garside, D. Adigbli, A.B. Cavalcanti, et al.
Balanced crystalloids versus saline in critically ill adults — A systematic review with metaanalysis.
C. Armero, P. Rodríguez, J.M. de la Torre Hernández.
A brief look into Bayesian statistics in cardiology data analysis.
REC Interv Cardiol, 4 (2022), pp. 207-215
Copyright © 2023. Elsevier España, S.L.U. and SEMICYUC
Medicina Intensiva (English Edition)
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