[Coronary surgery in elderly patients. In-hospital and long-term results]. / Cirugía coronaria en pacientes ancianos. Resultados hospitalarios y a largo plazo.

BACKGROUND: Taking into account the steady increase in the number of elderly patients requiring coronary artery bypass grafting, we sought to analyze the in-hospital and long-term evolution of a group of elderly patients (>/= 75 years) who underwent coronary artery bypass grafting, and to identify clinical predictors of mortality and long-term symptoms. METHODS: Between April 1996 and February 2000, 207 patients older than 75 years of age who had undergone coronary bypass grafting were prospectively and consecutively analyze. Mean age was 78.4 +/- 2.7. RESULTS: An average of 2.6 grafts/patients was constructed. Left mammary artery was used in 93% of patients. The in-hospital incidence of heart failure, atrial fibrillation, preoperative infarction and stroke was 38%, 29%, 4.8% and 2.8% respectively. The in-hospital mortality rate was 5.8%. Mean follow-up was 18 months (25th an 75th percentiles 9-29). Late mortality rate was 4.1% in eight patients. Excluding the in-hospital deaths, the estimated probability of survival (Kaplan-Meier) at 3 years was 94% and the survival freedom from symptoms was 86%. A multivariate analysis showed that only age was predictor of in-hospital mortality (OR 1.16, p = 0.009). Only peripheral vascular disease was found as a predictor of symptoms during the long-term follow-up (p = 0.001). CONCLUSIONS: In this series of senile patients who underwent coronary surgery, those of an older age (> 80 years) showed a higher risk of in-hospital mortality. The presence of peripheral vascular disease is useful in the prognosis assessment of the group.

Robust methods in bioequivalence assay; preliminary results.

The aim of this study is to compare four statistical methods for outlier identification in Bioequivalence tests. The methods are based in four confidence intervals, 'parametric','non- parametric','robust with the asymptotic distribution of the M-estimator' and 'robust with the bootstrap distribution'. The drug we used was Diltiazen, in a two sequence randomized crossover study design. The pharmacokinetic parameters measured were the area under the plasma concentration curve (AUC), and the peak drug concentration (CMAX). Time to peak drug concentration (TMAX), was not used here in order to separate the efficiency of the methods from the efficiency of the measurements. The methods were applied to simulated and experimental data. We made two simulations, one with normal data and another one with outliers data. When simulating normal data all methods showed similar profiles and high power. On the contrary, when simulating experiments with outliers data, the parametric method showed low power, whereas robust methods showed just a slight decrement in power. When we analyzed experimental data of AUC, if we used the parametric method (recommended by U.S.P), we were not able to conclude Bioequivalence, but with the other methods, this was possible. This disagreement between parametric and robust procedures was a sign of outliers data. We conclude that the robust methods in bioequivalence assays help us in the identification of outliers as observations with weight equal zero.