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Acid – base disturbances in critically ill septic patients: a longitudinal quantitative study

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Applying a quantitative methodology, we described the acid – base status of severe septic patients in the first 5 days after admission to the ICU.

Patients and methods

Patients were studied if they had a diagnosis of severe sepsis with less than 24 hours of organ dysfunction. Data were prospectively collected daily until the fifth day after inclusion.


Sixty patients were included in the study. At admission to the ICU, septic patients presented a severe metabolic acidosis with an average pH of 7.29; PCO2 = 36 mmHg and SBE = -8.0. Figure 1 presents the several components of the metabolic acid – base disturbances found on the first day in the ICU. We found that the magnitude of metabolic acidosis, measured by the SBE, was greater among the nonsurvivors than the survivors. However, the components of acid – base disturbances are kept proportionally constant among different clinical outcome subgroups.

Figure 1

Components of SBE on the first day.

During the study period, the survivor group presented an increased SBE from -6.4 to -1.5 due to a significant decrease in serum lactate level and SIG. No change occurred in the albumin serum level, which persisted as an alkalinizing force. In contrast, the nonsurvivor group became even more acidemic due to an increase in the PCO2 and persistence of a highly negative SBE. From the metabolic point of view, no significant change occurred in this group from the first to the last day of the study, except for a small increase in the phosphate serum level.


Severe septic patients present, on the first day in the ICU, a complex metabolic acid – base disturbance marked by a mixed high-degree acidosis partially attenuated by a hypo-albuminemic alkalosis. Over the study period, the survivor group partially corrected its acidosis mainly through the disappearance of unmeasured anions and lactate. Nonsurvivors did not change significantly their metabolic acidosis over time.

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Noritomi, D., Park, M., Liborio, A. et al. Acid – base disturbances in critically ill septic patients: a longitudinal quantitative study. Crit Care 11, P21 (2007) doi:10.1186/cc5808

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  • Severe Sepsis
  • Metabolic Acid
  • Metabolic Acidosis
  • Septic Patient
  • Lactate Level