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. 2013 Jul-Sep;25(3):197-204.
doi: 10.5935/0103-507X.20130035.

Urinary strong ion difference is a major determinant of plasma chloride concentration changes in postoperative patients

[Article in English, Portuguese]
Fabio Daniel Masevicius  1 , Alejandro Risso Vazquez, Carolina Enrico, Arnaldo Dubin
Affiliations

Urinary strong ion difference is a major determinant of plasma chloride concentration changes in postoperative patients

[Article in English, Portuguese]
Fabio Daniel Masevicius et al. Rev Bras Ter Intensiva. 2013 Jul-Sep.

Abstract
in English, Portuguese

Objective: To show that alterations in the plasma chloride concentration ([Cl-]plasma) during the postoperative period are largely dependent on the urinary strong ion difference ([SID]urine=[Na+]urine+[K+]urine-[Cl-]urine) and not on differences in fluid therapy.

Methods: Measurements were performed at intensive care unit admission and 24 hours later in a total of 148 postoperative patients. Patients were assigned into one of three groups according to the change in [Cl-]plasma at the 24 hours time point: increased [Cl-]plasma (n=39), decreased [Cl-]plasma (n=56) or unchanged [Cl-]plasma (n=53).

Results: On admission, the increased [Cl-]plasma group had a lower [Cl-]plasma (105 ± 5 versus 109 ± 4 and 106 ± 3 mmol/L, p<0.05), a higher plasma anion gap concentration ([AG]plasma) and a higher strong ion gap concentration ([SIG]). After 24 hours, the increased [Cl-]plasma group showed a higher [Cl-]plasma (111 ± 4 versus 104 ± 4 and 107 ± 3 mmol/L, p<0.05) and lower [AG]plasma and [SIG]. The volume and [SID] of administered fluids were similar between groups except that the [SID]urine was higher (38 ± 37 versus 18 ± 22 and 23 ± 18 mmol/L, p<0.05) in the increased [Cl-]plasma group at the 24 hours time point. A multiple linear regression analysis showed that the [Cl-]plasma on admission and [SID]urine were independent predictors of the variation in [Cl-]plasma 24 hours later.

Conclusions: Changes in [Cl-]plasma during the first postoperative day were largely related to [SID]urine and [Cl-]plasma on admission and not to the characteristics of the infused fluids. Therefore, decreasing [SID]urine could be a major mechanism for preventing the development of saline-induced hyperchloremia.

Objetivo: Demonstrar que alterações na concentração plasmática de cloreto ([Cl-]plasma) durante o período pós-operatório são amplamente dependentes da diferença de íons fortes urinária ([SID]urina=[Na+] urina+[K+] urina -[Cl-]urina) e não de diferenças na terapia hídrica.

Métodos: Foram realizadas mensurações na admissão à unidade de terapia intensiva e 24 horas mais tarde em um total de 148 pacientes pós-operatórios. Os pacientes foram designados para um de três grupos segundo a alteração na concentração plasmática de cloreto após 24 horas: [Cl-]plasma aumentada (n=39), [Cl-]plasma diminuída (n=56) ou [Cl-]plasma inalterada (n=53).

Resultados: Quando da admissão, o grupo com [Cl-]plasma aumentada tinha [Cl-]plasma mais baixa (105±5 versus 109±4 e 106±3mmol/L; p<0,05), um ânion gap plasmático ([AG]plasma) mais alto e um íon gap forte mais alto. Após 24 horas, o grupo com [Cl-]plasma aumentada mostrou [Cl-]plasma mais alta (111±4 versus 104±4 e 107±3mmol/L; p<0,05) e nível plasmático mais baixo de [AG]plasma e íon gap forte. O volume e íon gap forte dos fluidos administrados foram similares entre os grupos, exceto que os [SID]urina eram mais altos (38±37 versus 18±22 e 23±18mmol/L; p<0,05) no grupo com [Cl-]plasma aumentada na avaliação após 24 horas. Uma análise de regressão linear múltipla demonstrou que a [Cl-]plasma na admissão e [SID]urina eram preditores independentes de variação na [Cl-]plasma 24 horas mais tarde.

Conclusões: Alterações na [Cl-]plasma durante o primeiro dia pós-operatório foram amplamente relacionadas com [SID]urina e [Cl-]plasma na admissão, e não às características dos fluidos infundidos. Portanto, a diminuição da [SID]urina deve ser um mecanismo importante para prevenção do desenvolvimento de hipercloremia induzida por solução salina.

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Conflict of interest statement

Conflicts of interest: None.

Figures

Figure 1
Figure 1
Variation in the plasma chloride concentration in the increased [Cl-]plasma, decreased [Cl-]plasma, and unchanged [Cl-]plasma groups. ICU - intensive care unit.
Figure 2
Figure 2
Volumes and strong ion differences of the administered solutions and urine in the increased [Cl-]plasma, decreased [Cl-]plasma, and unchanged [Cl-]plasma groups. Panel A: Volume of the administered solutions. Panel B: Strong ion difference of the administered solutions. Panel C: Volume of diuresis. Panel D: 24 hours urine strong ion difference. SID - strong ion difference.
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Comment in

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