RESUMEN
INTRODUCTION: Critically ill patients might present complex acid-base disorders, even when the pH, PCO2, [HCO3-], and base excess ([BE]) levels are normal. Our hypothesis was that the acidifying effect of severe hyperlactatemia is frequently masked by alkalinizing processes that normalize the [BE]. The goal of the present study was therefore to quantify these disorders using both Stewart and conventional approaches. METHODS: A total of 1,592 consecutive patients were prospectively evaluated on intensive care unit admission. Patients with severe hyperlactatemia (lactate level > or = 4.0 mmol/l) were grouped according to low or normal [BE] values (<-3 mmol/l or >-3 mmol/l). RESULTS: Severe hyperlactatemia was present in 168 of the patients (11%). One hundred and thirty-four (80%) patients had low [BE] levels while 34 (20%) patients did not. Shock was more frequently present in the low [BE] group (46% versus 24%, P = 0.02) and chronic obstructive pulmonary disease in the normal [BE] group (38% versus 4%, P < 0.0001). Levels of lactate were slightly higher in patients with low [BE] (6.4 +/- 2.4 mmol/l versus 5.6 +/- 2.1 mmol/l, P = 0.08). According to our study design, the pH, [HCO3-], and strong-ion difference values were lower in patients with low [BE]. Patients with normal [BE] had lower plasma [Cl-] (100 +/- 6 mmol/l versus 107 +/- 5 mmol/l, P < 0.0001) and higher differences between the changes in anion gap and [HCO3-] (5 +/- 6 mmol/l versus 1 +/- 4 mmol/l, P < 0.0001). CONCLUSION: Critically ill patients may present severe hyperlactatemia with normal values of pH, [HCO3-], and [BE] as a result of associated hypochloremic alkalosis.
Asunto(s)
Equilibrio Ácido-Base , Acidosis Láctica/sangre , Enfermedad Crítica , Anciano , Bicarbonatos/sangre , Análisis de los Gases de la Sangre , Dióxido de Carbono/sangre , Cloruros/sangre , Femenino , Humanos , Concentración de Iones de Hidrógeno , Unidades de Cuidados Intensivos , Ácido Láctico/sangre , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Enfermedad Pulmonar Obstructiva Crónica/sangre , Choque/sangreRESUMEN
OBJECTIVES: The Stewart approach states that pH is primarily determined by Pco2, strong ion difference (SID), and nonvolatile weak acids. This method might identify severe metabolic disturbances that go undetected by traditional analysis. Our goal was to compare diagnostic and prognostic performances of the Stewart approach with a) the traditional analysis based on bicarbonate (HCO3) and base excess (BE); and b) an approach relying on HCO3, BE, and albumin-corrected anion gap (AGcorrected). DESIGN: Prospective observational study. SETTING: A university-affiliated hospital intensive care unit (ICU). PATIENTS: Nine hundred thirty-five patients admitted to the ICU. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The Stewart approach detected an arterial metabolic alteration in 131 (14%) of patients with normal HCO3- and BE, including 120 (92%) patients with metabolic acidosis. However, 108 (90%) of these patients had an increased AGcorrected. The Stewart approach permitted the additional diagnosis of metabolic acidosis in only 12 (1%) patients with normal HCO3, BE, and AGcorrected. On the other hand, the Stewart approach failed to identify 27 (3%) patients with alterations otherwise observed with the use of HCO3-, BE, and AGcorrected (16 cases of acidosis and 11 of alkalosis). SID and BE, and strong ion gap (SIG) and AGcorrected, were tightly correlated (R2 = .86 and .97, p < .0001 for both) with narrow 95% limits of agreement (8 and 3 mmol/L, respectively). Areas under receiver operating characteristic curves to predict 30-day mortality were 0.83, 0.62, 0.61, 0.60, 0.57, 0.56, and 0.67 for Sepsis-related Organ Failure Assessment (SOFA) score, SIG, AGcorrected, SID, BE, HCO3-, and lactates, respectively (SOFA vs. the rest, p < .0001). CONCLUSIONS: In this large group of critically ill patients, diagnostic performance of the Stewart approach exceeded that of HCO3- and BE. However, when AGcorrected was included in the analysis, the Stewart approach did not offer any diagnostic or prognostic advantages.
Asunto(s)
Desequilibrio Ácido-Base/diagnóstico , Aniones/análisis , Bicarbonatos/sangre , Desequilibrio Ácido-Base/mortalidad , Desequilibrio Ácido-Base/patología , Anciano , Albúminas/análisis , Área Bajo la Curva , Femenino , Humanos , Concentración de Iones de Hidrógeno , Hipoalbuminemia/complicaciones , Unidades de Cuidados Intensivos , Ácido Láctico/análisis , Modelos Lineales , Modelos Logísticos , Masculino , Insuficiencia Multiorgánica/etiología , Insuficiencia Multiorgánica/mortalidad , Pronóstico , Estudios Prospectivos , Valores de Referencia , Sepsis/complicaciones , Sepsis/mortalidadRESUMEN
Se presenta el caso clínico de una paciente diabética tipo 2 tratada con metformina que es internada por un accidente cerebrovascular isquémico. En el laboratorio se detectó una hiperlactacidemia de 4,8 mmol/l, con pH, bicarbonato y exceso de base normales. Sin embargo, el enfoque de Stewart permitió identificar la presencia de una acidosis metabólica por aniones no medidos y una alcalosis hipoclorémica. El anión gap estaba elevado y sus valores declinaron paralelamente a los del ácido láctico. Se revisa la acidosis láctica por mertformina y el enfoque diagnóstico de este trastorno metabólico ácido-base.