Métodos estadísticos alternativos y su aplicación a la investigación en Cuidados Intensivos / Alternative statistical methods and their application to research in intensive care setting

En los estudios de casos y controles anidados, el muestreo de los controles se hace habitualmente por densidad de incidencia y mediante emparejamiento. Con respecto a los casos control clásicos, son más eficientes, permiten el cálculo de la incidencia de la enfermedad y cuentan con más validez interna por la menor presencia de sesgo. Las técnicas de riesgos competitivos pueden usarse si se estudian diferentes tipos de eventos y nos centramos en el tiempo y el tipo del primer evento. El particionamiento recursivo es un tipo de análisis multivariante cuyo propósito es la construcción de algoritmos de clasificación, especialmente útiles cuando hay un gran número de variables predictoras con relaciones complejas con el evento objeto de estudio

In nested case-control studies, sampling of controls is usually done by density of incidence and pairing. With regard to the classic control cases studies, nested ones are more efficient, allow the calculation of the incidence of the disease and they have more internal validity due to the lower presence of bias. Competitive risks techniques can be used if we study different types of events and focus on the time and type of the first event. Recursive partitioning is a type of multivariate analysis whose purpose is the construction of classification algorithms, and it is especially useful when there are a large number of predictive variables with complex relationships with the event

Alternative statistical methods and their application to research in intensive care setting. / Métodos estadísticos alternativos y su aplicación a la investigación en Cuidados Intensivos.

In nested case-control studies, sampling of controls is usually done by density of incidence and pairing. With regard to the classic control cases studies, nested ones are more efficient, allow the calculation of the incidence of the disease and they have more internal validity due to the lower presence of bias. Competitive risks techniques can be used if we study different types of events and focus on the time and type of the first event. Recursive partitioning is a type of multivariate analysis whose purpose is the construction of classification algorithms, and it is especially useful when there are a large number of predictive variables with complex relationships with the event.

A pragmatic approach for mortality prediction after surgery in infective endocarditis: optimizing and refining EuroSCORE.

OBJECTIVE: To simplify and optimize the ability of EuroSCORE I and II to predict early mortality after surgery for infective endocarditis (IE). METHODS: Multicentre retrospective study (n = 775). Simplified scores, eliminating irrelevant variables, and new specific scores, adding specific IE variables, were created. The performance of the original, recalibrated and specific EuroSCOREs was assessed by Brier score, C-statistic and calibration plot in bootstrap samples. The Net Reclassification Index was quantified. RESULTS: Recalibrated scores including age, previous cardiac surgery, critical preoperative state, New York Heart Association >I, and emergent surgery (EuroSCORE I and II); renal failure and pulmonary hypertension (EuroSCORE I); and urgent surgery (EuroSCORE II) performed better than the original EuroSCOREs (Brier original and recalibrated: EuroSCORE I: 0.1770 and 0.1667; EuroSCORE II: 0.2307 and 0.1680). Performance improved with the addition of fistula, staphylococci and mitral location (EuroSCORE I and II) (Brier specific: EuroSCORE I 0.1587, EuroSCORE II 0.1592). Discrimination improved in specific models (C-statistic original, recalibrated and specific: EuroSCORE I: 0.7340, 0.7471 and 0.7728; EuroSCORE II: 0.7442, 0.7423 and 0.7700). Calibration improved in both EuroSCORE I models (intercept 0.295, slope 0.829 (original); intercept -0.094, slope 0.888 (recalibrated); intercept -0.059, slope 0.925 (specific)) but only in specific EuroSCORE II model (intercept 2.554, slope 1.114 (original); intercept -0.260, slope 0.703 (recalibrated); intercept -0.053, slope 0.930 (specific)). Net Reclassification Index was 5.1% and 20.3% for the specific EuroSCORE I and II. CONCLUSIONS: The use of simplified EuroSCORE I and EuroSCORE II models in IE with the addition of specific variables may lead to simpler and more accurate models.

Left-sided infective endocarditis in patients with liver cirrhosis.

OBJECTIVE: To evaluate the course of left-sided infective endocarditis (LsIE) in patients with liver cirrhosis (LC) analyzing its influence on mortality and the impact of surgery. METHODS: Prospective cohort study, conducted from 1984 to 2013 in 26 Spanish hospitals. RESULTS: A total of 3.136 patients with LsIE were enrolled and 308 had LC: 151 Child-Pugh A, 103 B, 34 C and 20 were excluded because of unknown stage. Mortality was significantly higher in the patients with LsIE and LC (42.5% vs. 28.4%; p < 0.01) and this condition was in general an independent worse factor for outcome (HR 1.51, 95% CI: 1.23-1.85; p < 0.001). However, patients in stage A had similar mortality to patients without cirrhosis (31.8% vs. 28.4% p = NS) and in this stage heart surgery had a protective effect (28% in operated patients vs. 60% in non-operated when it was indicated). Mortality was significantly higher in stages B (52.4%) and C (52.9%) and the prognosis was better for patients in stage B who underwent surgery immediately (mortality 50%) compared to those where surgery was delayed (58%) or not performed (74%). Only one patient in stage C underwent surgery. CONCLUSIONS: Patients with liver cirrhosis and infective endocarditis have a poorer prognosis only in stages B and C. Early surgery must be performed in stages A and although in selected patients in stage B when indicated.

Global impact of an educational antimicrobial stewardship programme on prescribing practice in a tertiary hospital centre.

The misuse of antibiotics has been related to increased morbidity, mortality and bacterial resistance. The development of antimicrobial stewardship programmes (ASPs) has been encouraged by scientific societies as an essential measure. An educational, institutionally supported ASP was developed in our tertiary-care centre. Local guidelines on the management of infectious syndromes were created. Antimicrobial prescriptions were chosen arbitrarily weekly and counselling interviews by expert clinicians were carried out, using a paedagogic, non-restrictive methodology. Satisfaction with the interview was assessed using anonymous questionnaires. The appropriateness of antimicrobial prescriptions as well as consumption was assessed prospectively throughout the year. Feedback regarding the correct use of treatments was communicated to each participating department periodically. The improvement in antimicrobial prescription was included among the annual objectives linked to economic incentives in every department. A total of 1206 counselling interviews were carried out during the first year. Fifty-three per cent of antimicrobial prescriptions (176/332) were inappropriate when the programme started. The rate of inappropriate prescriptions continuously declined to 26.4% (107/405) in the fourth trimester (p <0.001; RR = 0.38; 95% CI, 0.23-0.43). Antimicrobial consumption decreased from 1150 defined daily doses (DDDs) per 1000 occupied bed-days in the first trimester to 852 DDDs in the fourth, reflecting a reduction in antimicrobial expenditures of 42%. A total of 352 satisfaction questionnaires were received and 98% described the advice as positive. In conclusion, the implementation of an education-based ASP achieved a significant improvement in all antimicrobial prescriptions in the centre and a reduction in antimicrobial consumption, even when no restrictive measures were implemented. The programme was highly accepted by all prescribers.

Mortality and hospital stay related to coagulase-negative Staphylococci bacteremia in non-critical patients.

OBJECTIVES: To describe the morbidity and mortality related to coagulase-negative Staphylococci (CNS) bacteremia in non-critical patients. METHODS: Prospective, matched case-control study nested in a cohort. Patients with CNS bacteremia and no other isolate in blood cultures during their admission were defined as cases. Each case was matched by age, sex and area of hospitalization to one control. A 30-day follow-up was performed. Mortality and hospital stay were defined as endpoints. RESULTS: 105 cases and 105 controls were included. All cases carried intravascular catheters at the time of inclusion. Cases presented higher mortality compared to controls (14.3% vs. 4.8%), although this association was not independent in a multivariate analysis (p = 0.11). CNS bacteremia was independently associated with longer hospital stay (mean 12 vs. 8.5 days, p = 0.008). Moreover, when patients with CNS bacteremia were specifically analyzed, the persistence of fever (p = 0.005) and inappropriate empirical treatment (p = 0.04) were independently related to mortality. CONCLUSION: We did not observe increased mortality attributable to CNS bacteremia, although it was associated with longer hospitalizations. Early appropriate empirical antibiotic therapy pending blood culture results might improve the outcome of patients with CNS bacteremia. Close follow-up is recommended if fever persists beyond 72 h.

Time to positivity of blood culture association with clinical presentation, prognosis and ESBL-production in Escherichia coli bacteremia.

The time to positivity (TTP) of blood cultures has been associated with increased mortality in bacteremia caused by several microorganisms. The aim of this study is to evaluate the relationship between TTP and prognosis, clinical presentation and extended spectrum B-lactamase (ESBL)-production in patients with Escherichia coli bacteremia. This is a retrospective observational study involving 226 adult patients with E. coli bacteremia. Data collected included underlying diseases, clinical presentation, prognosis factors, TTP, ESBL-production and outcome. Thirty-one (14%) patients had severe sepsis and 29 (13%) septic shock at presentation. Thirty-three (14%) strains were ESBL-producers. Thirty-nine (17%) patients died during admission and 17 (7.5%) within 48 hours. The median TTP was 8.3 hours (range, 0.42­76.5). It was significantly shorter in patients with septic shock (6.23 h, range 1.12­47.29 h vs. 8.51 h, range 0.42­76.50 h; p = 0.018). Rapid growth of E. coli, Pitt index >1.5, non-urinary source and Charlson score >2 were selected as independent risk factors of in-hospital mortality by the multivariate analysis. ESBL-production was not associated with modifications in TTP. Lower TTP is an independent risk factor for septic shock and poor outcome in episodes of E. coli bacteremia. The TTP in E. coli bacteremia is not significantly modified by ESBL-production.

Surgical treatment for infective endocarditis in elderly patients.

OBJECTIVES: We evaluate the clinical, echographic and prognostic characteristics of infective endocarditis (IE) in a large population of elderly patients, and the results of surgical approach. METHODS: Multicentric, prospective, observational cohort study with 961 consecutive left-sided IE: 356 patients aged ≥65 years were compared with 605 younger. Indications for cardiac surgery, potential surgical risk, time and outcome, were compared. RESULTS: Hospital-acquired endocarditis, comorbidity, renal failure and septic shock were more frequent in elderly, but embolisms were less. Intracardiac destruction and ventricular failure were similar in both groups, but significantly fewer elderly patients underwent cardiac surgery (36% vs 51%; p < 0.01), and this group showed a worse outcome (43.2% of mortality vs 27% in younger; p < 0.01), resulting age as an independent predictor of mortality (OR: 1.02 CI95%: 1.01-1.03). Compared with medical treatment, surgery showed lower percentages of mortality compared with medical treatment (23.3% vs 31.3%; p = 0.03) in younger group, but a high mortality was observed with both procedures (47.6% vs 40.3%; p = 0.1) in the elderly. CONCLUSIONS: Although similar percentages of heart failure and intracardiac complications, increasing age is associated with higher mortality in IE. Lower rates of surgical treatment and a worse outcome after operation are common features in elderly patients.

Superinfection during treatment of nosocomial infections with tigecycline.

We performed a retrospective and observational study of 51 patients treated with tigecycline, as the treatment for nosocomial infections due to multidrug-resistant microorganisms, to evaluate the superinfection rate and their etiologies. Superinfections were diagnosed in 12 (23.5%) patients (seven due to Pseudomonas aeruginosa, 13.7%) and one patient had P. aeruginosa colonization. Five patients with superinfection died (41.6%), three due to superinfections and two to underlying diseases. The superinfection rate observed during tigecycline treatment is higher than that previously reported. Pseudomonas aeruginosa is the most frequent agent, being the cause of 58.5% of all superinfections.