Intensive Care Medicine

, Volume 38, Issue 4, pp 686–693 | Cite as

In vivo conditioning of acid–base equilibrium by crystalloid solutions: an experimental study on pigs

  • T. Langer
  • E. Carlesso
  • A. Protti
  • M. Monti
  • B. Comini
  • L. Zani
  • D. T. Andreis
  • G. E. Iapichino
  • D. Dondossola
  • P. Caironi
  • S. Gatti
  • L. Gattinoni
Experimental

Abstract

Purpose

Large infusion of crystalloids may induce acid-base alterations according to their strong ion difference ([SID]). We wanted to prove in vivo, at constant PCO2, that if the [SID] of the infused crystalloid is equal to baseline plasma bicarbonate, the arterial pH remains unchanged, if lower it decreases, and if higher it increases.

Methods

In 12 pigs, anesthetized and mechanically ventilated at PCO2 ≈40 mmHg, 2.2 l of crystalloids with a [SID] similar to (lactated Ringer’s 28.3 mEq/l), lower than (normal saline 0 mEq/l), and greater than (rehydrating III 55 mEq/l) baseline bicarbonate (29.22 ± 2.72 mEq/l) were infused for 120 min in randomized sequence. Four hours of wash-out were allowed between the infusions. Every 30 min up to minute 120 we measured blood gases, plasma electrolytes, urinary volume, pH, and electrolytes. Albumin, hemoglobin, and phosphates were measured at time 0 and 120 min.

Results

Lactated Ringer’s maintained arterial pH unchanged (from 7.47 ± 0.06 to 7.47 ± 0.03) despite a plasma dilution around 12%. Normal saline caused a reduction in pH (from 7.49 ± 0.03 to 7.42 ± 0.04) and rehydrating III induced an increase in pH (from 7.46 ± 0.05 to 7.49 ± 0.04). The kidney reacted to the infusion, minimizing the acid-base alterations, by increasing/decreasing the urinary anion gap, primarily by changing sodium and chloride concentrations. Lower urine volume after normal saline infusion was possibly due to its greater osmolarity and chloride concentration as compared to the other solutions.

Conclusions

Results support the hypothesis that at constant PCO2, pH changes are predictable from the difference between the [SID] of the infused solution and baseline plasma bicarbonate concentration.

Keywords

Crystalloid solutions Acid-base equilibrium Stewart's approach Volume resuscitation Animal study 

Supplementary material

134_2011_2455_MOESM1_ESM.doc (466 kb)
Supplementary material 1 (DOC 281 kb)

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Copyright information

© Copyright jointly held by Springer and ESICM 2012

Authors and Affiliations

  • T. Langer
    • 1
  • E. Carlesso
    • 1
  • A. Protti
    • 1
  • M. Monti
    • 1
  • B. Comini
    • 1
  • L. Zani
    • 1
  • D. T. Andreis
    • 1
  • G. E. Iapichino
    • 1
  • D. Dondossola
    • 2
  • P. Caironi
    • 1
    • 3
  • S. Gatti
    • 2
  • L. Gattinoni
    • 1
    • 3
  1. 1.Dipartimento di Anestesiologia, Terapia Intensiva e Scienze Dermatologiche, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico di MilanoUniversità degli StudiMilanoItaly
  2. 2.Centro di Ricerche Chirurgiche PreclinicheFondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico di MilanoMilanItaly
  3. 3.Dipartimento di Anestesia, Rianimazione (Intensiva e Subintensiva) e Terapia del DoloreFondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico diMilanoItaly

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