Comparison of three different methods of evaluation of metabolic acid-base disorders.

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.

The distinct clinical profile of chronically critically ill patients: a cohort study.

INTRODUCTION: Our goal was to describe the epidemiology, clinical profiles, outcomes, and factors that might predict progression of critically ill patients to chronically critically ill (CCI) patients, a still poorly characterized subgroup. METHODS: We prospectively studied all patients admitted to a university-affiliated hospital intensive care unit (ICU) between 1 July 2002 and 30 June 2005. On admission, we recorded epidemiological data, the presence of organ failure (multiorgan dysfunction syndrome (MODS)), underlying diseases (McCabe score), acute respiratory distress syndrome (ARDS) and shock. Daily, we recorded MODS, ARDS, shock, mechanical ventilation use, lengths of ICU and hospital stay (LOS), and outcome. CCI patients were defined as those having a tracheotomy placed for continued ventilation. Clinical complications and time to tracheal decannulation were registered. Predictors of progression to CCI were identified by logistic regression. RESULTS: Ninety-five patients (12%) fulfilled the CCI definition and, compared with the remaining 690 patients, these CCI patients were sicker (APACHE II, 21 +/- 7 versus 18 +/- 9 for non-CCI patients, p = 0.005); had more organ dysfunctions (SOFA 7 +/- 3 versus 6 +/- 4, p < 0.003); received more interventions (TISS 32 +/- 10 versus 26 +/- 8, p < 0.0001); and had less underlying diseases and had undergone emergency surgery more frequently (43 versus 24%, p = 0.001). ARDS and shock were present in 84% and 83% of CCI patients, respectively, versus 44% and 48% in the other patients (p < 0.0001 for both). CCI patients had higher expected mortality (38% versus 32%, p = 0.003), but observed mortality was similar (32% versus 35%, p = 0.59). Independent predictors of progression to CCI were ARDS on admission, APACHE II and McCabe scores (odds ratio (OR) 2.26, p < 0.001; OR 1.03, p < 0.01; and OR 0.34, p < 0.0001, respectively). Lengths of mechanical ventilation, ICU and hospital stay were 33 (24 to 50), 39 (29 to 55) and 55 (37 to 84) days, respectively. Tracheal decannulation was achieved at 40 +/- 19 days. CONCLUSION: CCI patients were a severely ill population, in which ARDS, shock, and MODS were frequent on admission, and who suffered recurrent complications during their stay. However, their prognosis was equivalent to that of the other ICU patients. ARDS, APACHE II and McCabe scores were independent predictors of evolution to chronicity.

Shock on admission day is the best predictor of prolonged mechanical ventilation in the ICU.

STUDY OBJECTIVES: To determine the incidence of prolonged mechanical ventilation (PMV), which is associated with increased health-care costs and risks of adverse events, and to identify its early predictors. DESIGN: Retrospective cohort. SETTING: A medical-surgical ICU in a university-affiliated hospital. PATIENTS OR PARTICIPANTS: All patients admitted to the ICU over 3 years who received mechanical ventilation (MV) for > 12 h. INTERVENTIONS: None. MEASUREMENTS: PMV was defined as MV lasting > 21 days. We recorded epidemiologic data, severity scores, worst Pao(2)/fraction of inspired oxygen (Fio(2)), presence of shock on ICU admission day, cause for MV, length of MV, ICU length of stay (LOS), and hospital LOS. PMV patients were compared to patients weaned before 21 days (non-PMV group) to determine predictors of PMV. RESULTS: Of 551 hospital admissions, 319 patients (58%) required MV > 12 h. One hundred thirty patients died early and were excluded. Seventy-nine patients (14%) required PMV. The non-PMV group consisted of 110 patients. Simplified acute physiology score (SAPS) II, APACHE (acute physiology and chronic health evaluation) II, therapeutic intervention scoring system, Pao(2)/Fio(2), shock, ICU LOS, and hospital LOS differed significantly between groups. However, logistic regression identified shock on ICU admission day as the only independent predictor of PMV (odds ratio, 3.10; p = 0.001). SAPS II and Pao(2)/Fio(2) had the nearest coefficients and were used to build the predictive model. Sensitivity analysis was performed including the 130 patients who died early, and shock remained the most powerful predictor. CONCLUSIONS: PMV was a frequent event in this cohort. The presence of shock on ICU admission day was the only prognostic factor, even adjusting for severity of illness and hypoxemia.

Comparación de dos enfoques para el diagnóstico de los trastornos ácido-base metabólicos / Comparison of two approaches for the diagnosis of metabolic acid-base disorders

Introducción: Stewart ha planteado que la (H+) está primariamente determinada por: 1)la PCO2. 2) La diferencia de iones fuertes, SID=([Na+]+[K+]+[Ca++]+[Mg++])-([Cl-]+ [otros aniones fuertes]). 3) La concentración de ácidos débiles no volátiles, Atot= ([albúmina]+[Pi]). Las modificaciones de estas variables primarias, especialmente debido a la presencia casi constante de hipoalbuminemia, pueden provocar efectos aditivos o contrapuestos sobre variables dependientes como [HCO3] y exceso de base (EB). Usando este análisis, Fencl y cols. han demostrado que los pacientes críticos frecuentemente pueden presentar pH, [HCO3), EB y anión gap normales, en presencia de trastornos acidificantes o alcalinizantes, muchas veces graves...

Calcium dobesilate for chronic venous insufficiency: a systematic review.

Chronic venous insufficiency (CVI) causes much discomfort and sick leave. Many randomized clinical trials (RCTs) have shown a beneficial effect of calcium dobesilate, but consensus is lacking about efficacy and safety. The authors report a meta-analysis of the effectiveness and safety of calcium dobesilate in CVI. Ten RCTs (778 patients) in which calcium dobesilate for CVI was compared with placebo met the inclusion criteria. Only 3 trials (608 patients) were of good methodological quality. Calcium dobesilate significantly improved night cramps and discomfort nearly twice as well as placebo, with the number needed to treat (NNT) being 8 (95% CI 4-50) and 4 (95% CI 3-7), respectively. Frequency of adverse events was not significantly different from placebo. Subgroup analysis found a differential response with respect to disease severity, with greater improvements in pain, heaviness, and malleolar swelling being seen in the severe group than in the mild group. Calcium dobesilate improved paresthesias significantly more than placebo in the severe but not in the mild group and the effect on leg volume was also significantly better in the severe group (-7.2% vs -1.6%). No difference in effect was found for different doses of calcium dobesilate (1,000 or 1,500 mg/day). Sensitivity analyses did not affect the results. Current evidence suggests that calcium dobesilate is more effective than placebo in improving some CVI symptoms, that there is higher efficacy in more severe disease, and that a dose of 1,000 mg/day is as effective and safe as 1,500 mg/day. Further adequately powered trials are needed to further evaluate these hypotheses.

Impact of positive end-expiratory pressure on the definition of acute respiratory distress syndrome.

OBJECTIVE: We examined whether PEEP during the first hours of ARDS can induce such a change in oxygenation that could mask fulfillment of the AECC criteria of a PaO(2)/FIO(2)

Incidence, clinical course, and outcome in 217 patients with acute respiratory distress syndrome.

OBJECTIVE: To assess prospectively acute respiratory distress syndrome incidence, etiologies, physiologic and clinical features, and mortality and its predictors in four intensive care units in Argentina. DESIGN: Prospective inception cohort. SETTING: Four general intensive care units in teaching hospitals. PATIENTS: All consecutive adult patients admitted between January 3, 1999, and January 6, 2000, that met the criteria of the American-European Consensus Conference for acute respiratory distress syndrome. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 235 patients developed acute respiratory distress syndrome, and 217 survived for >24 hrs; these were further analyzed. Main risk factors were: sepsis (44%, including 65 pneumonia cases), shock (15%), trauma (11%), gastric aspiration (10%), and other (34%). At admission, nonsurvivors had significantly higher Acute Physiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment and McCabe scores, and lower oxygenation and pH. During the first week, Pao2/Fio2, Sequential Organ Failure Assessment, pH, base excess, and driving pressure consistently discriminated between survivors and nonsurvivors. Hospital mortality was 58%. One third of patients died early. Main causes of death were multiple organ dysfunction syndrome, sepsis, and septic shock; refractory hypoxemia was uncommon. Factors independently associated with mortality were organ dysfunctions on day 3, Pao2/Fio2 on day 3, and McCabe score. CONCLUSIONS: Acute respiratory distress syndrome was a frequent syndrome in this cohort. Sepsis was its leading cause, and pneumonia was the most common single diagnosis. Mortality was high but similar to most recent series that included serious comorbidities. Independent predictors of death 72 hrs after admission emphasize the importance of both extrapulmonary and pulmonary factors together with preexisting severe illnesses.

Respiratory syncytial virus prophylaxis: cost-effective analysis in Argentina.

INTRODUCTION: Respiratory syncytial virus is a major cause of bronchiolitis during the first year of life. Preterm infants and patients with bronchopulmonary dysplasia (BPD) have a higher risk of hospitalization. The objective of this study was to assess the risk of hospitalization and to evaluate the cost effectiveness of palivizumab use in our at risk population. METHODS: The study design was based on the hypothetical use of palivizumab in a cohort of patients. The cost effectiveness analysis included costs of palivizumab, the drug prescription and hospitalization. The effectiveness measure was the hospitalization rate decrease according to the result of the IMpact study: a 55% reduction in the need for hospitalization attributable to RSV. The years 1998 and 1999 were analyzed. Evaluable patients had follow-up at the High Risk Clinic and fulfilled the American Academy of Pediatrics criteria for palivizumab prophylaxis. RESULTS: Forty-two patients, 24 with BPD and 18 preterm infants without BPD, were evaluated. Ten patients required hospitalization because of respiratory syncytial virus; one of them died. Hospitalization cost was $184,777. The total palivizumab administration cost would have been $185,064. With a 55% decrease of hospitalization rate, the cost per hospitalization averted would have been $15,358, and the number needed to treat would have been 7.9. A sensitivity analysis showed that the cost per hospitalization averted could range between $2,171 and $48,630 according to the hospitalization rate. CONCLUSIONS: Because new effective but expensive treatments like palivizumab are available, this cost effective analysis can be an important tool in decisions about resource distribution.

Medicina basada en la evidencia / Evidence based medicine

La Medicina Basada en la Evidencia ha sido definida como el uso consciente, explícito y juicioso de la mejor evidencia. El avance tecnológico y la magnitud de información que actualmente un médico debe conocer para basar sus decisiones en la mejor evidencia hacen necesario que se sistematice la búsqueda, se aprecie críticamente la literatura y se aplique ese conocimiento para el logro de los mejores resultados. La difusión de esta forma de hacer Medicina pretende agregar al juicio clínico que se logra con la experiencia a través de los años, una forma práctica y sistemática de enfrentar el problema y reducir la posibilidad de error ante la toma de decisiones. No debemos pensar que puede ser usada por administradores de servicios de salud para reducir costos. Cuando se hace Medicina Basada en la Evidencia se aplican las medidas clínicas de mayor efectividad en beneficio de los pacientes y esto más que reducir puede aumentar los costos. Canadá, Holanda e Inglaterra tienen Centros de Medicina Basada en la Evidencia que reciben apoyo gubernamental. En Argentina nosotros necesitamos ser conscientes de este movimiento e intentar colaborar en la difusión de estas estrategias que pueden ayudar a mejorar la calidad de atención médica.