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Marcelo Park1, Aknar Calabrich1, Alexandre Toledo Maciel1, Fernando Godinho Zampieri1, Leandro Utino Taniguchi1, Ciro Eduardo de Souza1, Carlos Eduardo Barboza1, Antonio Paulo Nassar Junior1, Luciano César Pontes Azevedo1

Physicochemical characterization of metabolic acidosis induced by normal saline resuscitation of patients with severe sepsis and septic shockCaracterização físico-química da acidose metabólica induzida pela expansão volêmica inicial com solução salina a 0,9% em pacientes com sepse grave e choque séptico
ABSTRACT Objective: The aim of this study was to characterize and quantify metabolic acidosis that was caused by initial volume expansion during the reanimation of patients with severe sepsis and septic shock. Methods: A blood sample wasdrawn for physicochemical characterization of the patient’s acid-base equilibrium both before and after volume expansion using 30 mL/ kg 0.9% saline solution. The diagnosis and quantification of metabolic acidosis were based on the standard base excess (SBE). Results: Eight patients with a mean age of 58 ± 13 years and mean APACHE II scores of 20 ± 4 were expanded using 2,000 ± 370 mL of 0.9%saline solution. Blood pH dropped from 7.404 ± 0.080 to 7.367 ± 0.086 (p=0.018), and PCO2 increased from 30 ± 5 to 32 ± 2 mmHg (p=0.215); SBE dropped from -4.4 ± 5.6 to -6.0 ± 5.7 mEq/L (p=0.039). The drop in SBE was associated with the acidifying power of two factors, namely, a significant increase in the strong ion gap (SIG) from 6.1 ± 3.4 to 7.7 ± 4.0 mEq/L (p = 0.134) and a non-significant drop inthe apparent inorganic strong ion differences (SIDai) from 40 ± 5 to 38 ± 4 mEq/L (p = 0.318). Conversely, the serum albumin levels decreased from 3.1 ± 1.0 to 2.6 ± 0.8 mEq/L (p = 0.003) with an alkalinizing effect on SBE. Increased serum chloride levels from 103 ± 10 to 106 ± 7 mEq/L (p < 0.001) led to a drop in SIDai. Conclusion: Initial resuscitation using 30 mL/kg of 0.9% saline solution forpatients with severe sepsis and septic shock is associated with worsened metabolic acidosis, as measured by SBE. This worsened SBE can be ascribed to a serum increase in the levels of unmeasurable anions and chloride. Keywords: Ketosis; Intensive care units; Sepsis; Shock, septic/therapy; Acid-base equilibrium; Saline solution, hypertonic/therapeutic use

1. Intensive Care Unit, EmergencyDepartment, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo – USP – São Paulo (SP), Brazil.

This study was conducted at the Emergency Department – Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo – USP – São Paulo (SP), Brazil. Submitted on April 18, 2011 Accepted on June 10, 2011 Conflicts of interest: None. Corresponding author: Marcelo ParkRua Francisco Preto, 46 Zip Code: 05623-010 - São Paulo (SP), Brazil. Phone: 55 (11) 3069-6457 E-mail: mpark@uol.com.br

INTRODUCTION In Brazil, approximately 26% of patients who are admitted to the intensive care unit (ICU) are diagnosed with sepsis or severe sepsis.(1) Antibiotics and volume expansion are often the first-line therapies for these patients.(2) Crystalloids, particularly 0.9%saline solution (normal saline), are commonly used for volume expansion.(3) Although 0.9% saline solution is considered to be a “physiological solution”, infusing large volumes can cause metabolic disorders, particularly hyperchloremia-associated acidosis.(4-6) The actual implications of metabolic acidosis in patients with severe sepsis and septic shock is currently uncertain;(7) however, metabolicacidosis and hyperchloremia at admission and unimproved metabolic acidosis that are associated with lactate and unmeasurable anions within 5 days of admission are related to an increased mortality rate.(8) Overall, in septic patients, improving metabolic acidosis as measured by

Rev Bras Ter Intensiva. 2011; 23(2):176-182

Metabolic acidosis with normal saline resuscitation in septic patients...