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The early phase of critical illness is a progressive acidic state due to unmeasured anions

Published online by Cambridge University Press:  01 July 2008

B. Antonini ,
S. Piva ,
M. Paltenghi ,
A. Candiani  and
N. Latronico
B. Antonini*
Affiliation:
University of Brescia, Institute of Anesthesiology and Intensive Care, Spedali Civili, Brescia, Italy
S. Piva
Affiliation:
University of Brescia, Institute of Anesthesiology and Intensive Care, Spedali Civili, Brescia, Italy
M. Paltenghi
Affiliation:
University of Brescia, Institute of Anesthesiology and Intensive Care, Spedali Civili, Brescia, Italy
A. Candiani
Affiliation:
University of Brescia, Institute of Anesthesiology and Intensive Care, Spedali Civili, Brescia, Italy
N. Latronico
Affiliation:
University of Brescia, Institute of Anesthesiology and Intensive Care, Spedali Civili, Brescia, Italy
*
Institute of Anesthesiology and Intensive Care, University of Brescia, Spedali Civili di Brescia, Piazzale Spedali Civili, 1, 25123 Brescia, Italy. E-mail: [email protected]; Tel: +39 30 3995570; Fax: +39 30 3995841
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Summary

Background and objective

Stewart’s and Fencl’s methods have recently been proposed to interpret acid–base disorders where traditional theory has proven inadequate. Our objectives were to evaluate: (1) the occurrence of acid–base disturbances in critically ill patients and their trend over the first 3 intensive care unit days, (2) whether Stewart’s theory offers advantages over the traditional theory in the diagnosis of acid–base metabolic disturbances and (3) whether variables derived from Stewart’s and Fencl’s methods offer advantages over the traditional method to predict patient mortality.

Methods

A prospective cohort study in a general intensive care unit. Blood samples were analysed for arterial blood gases, electrolytes and proteins. PaCO2, pH, bicarbonate, base excess, standard base-excess, sodium, potassium, chloride, phosphorous, calcium, magnesium and lactate were measured. Anion gap, Stewart’s and Fencl’s variables were calculated.

Results

When using Stewart’s method, metabolic acidosis and metabolic alkalosis were found in 92.9% and 93.4% of samples, respectively. Corresponding figures obtained with the traditional method were 15% and 18.7%. In 245 (64.5%) samples, Stewart’s method revealed that metabolic acidosis and alkalosis were simultaneously present, whereas the traditional method revealed a normal acid–base status. Strong ion gap increased significantly over the first 3 intensive care unit days. Strong ion gap and lactate were independent predictors of 28-day mortality.

Conclusions

Metabolic acidosis by unmeasured anions is a clinically relevant phenomenon, which is correlated with mortality. Progressive metabolic acidosis may be ongoing in the early phase of critical illness despite the absence of acidaemia.

Keywords

ACID–BASE EQUILIBRIUMMETABOLIC ACIDOSISMETABOLIC ALKALOSISCRITICAL CAREHYPOALBUMINAEMIAANIONSMORTALITYOUTCOME
Type
Original Article
Information
European Journal of Anaesthesiology , Volume 25 , Issue 7 , July 2008 , pp. 566 - 571
Copyright
Copyright © European Society of Anaesthesiology 2008

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