Low noncarbonic buffer power amplifies acute respiratory acid-base disorders in patients with sepsis: an in vitro study
Abstrakt
RATIONALE: Septic patients have typically reduced concentrations of hemoglobin and albumin, the major components of non-carbonic buffer power(β). This could expose patients to high pH variations during acid-base disorders.
OBJECTIVES: To compare, in-vitro, non-carbonic β of septic patients with that of healthy volunteers, and evaluate its distinct components. METHODS: Whole blood and isolated plasma of 18 septic patients and 18 controls were equilibrated with different CO(2) mixtures.
Blood gases, pH and electrolytes were measured. Non-carbonic β and non-carbonic β due to variations in Strong Ion Difference (β(SID)) were calculated for whole blood.
Non-carbonic β and non-carbonic β normalized for albumin concentrations (β(NORM)) were calculated for isolated plasma. Representative values at pH=7.40 were compared.
Albumin proteoforms were evaluated via two-dimensional electrophoresis. MEASUREMENTS AND MAIN RESULTS: Hemoglobin and albumin concentrations were significantly lower in septic patients.
Septic patients had lower non-carbonic β both of whole blood (22.0+-1.9 vs. 31.6+-2.1 mmol/L, p<0.01) and plasma (0.5+-1.0 vs. 3.7+-0.8 mmol/L, p<0.01). Non-carbonic β(SID) was lower in patients (16.8+-1.9 vs. 24.4+-1.9 mmol/L, p<0.01) and strongly correlated with hemoglobin concentration (r=0.94, p<0.01).
Non-carbonic β(NORM) was lower in patients (0.01 [-0.01 - 0.04] vs. 0.08 [0.06 - 0.09] mmol/g, p<0.01). Septic patients and controls showed different amounts of albumin proteoforms.
CONCLUSIONS: Septic patients are exposed to higher pH variations for any given change in CO(2) due to lower concentrations of non-carbonic buffers and, possibly, an altered buffering function of albumin. In both septic patients and healthy controls, electrolyte shifts are the major buffering mechanism during respiratory acid-base disorders.