Attributable mortality due to nosocomial infections. A simple and useful application of multistate models.

OBJECTIVES: Nosocomial infections constitute a major medical problem leading to increased morbidity and mortality of patients. Besides prolongation of length of hospital stay, hospital mortality attributable to those infections is often the quantity of interest when describing their impact and consequences. Since occurrence of nosocomial infections is a time-dynamic process, estimation of this quantity might be hampered by that fact. A general framework shall be developed for defining and estimating attributable mortality that in addition is taking discharge of patients as competing risk and potential censoring of observation time into account. METHODS: Since the term "attributable mortality" is used in a variety of meanings we first review basic definitions; the quantities of interest are then derived in terms of transition probabilities arising in a suitably defined multistate model that allows straightforward estimation and interpretation. Bootstrap resampling is used to calculate corresponding standard errors and confidence intervals. RESULTS: The methodology is applied to the data of the SIR-3 study, a prospective cohort study on the incidence of nosocomial infections in intensive care unit patients. Occurrence of nosocomial pneumonia is shown to be associated with increased mortality; the population-attributable fraction is estimated as 7.7% (95% confidence interval: 2.6-12.8%) for an observation period of 120 days. CONCLUSION: Attributable mortality is an important risk measure in epidemiology. If risk exposure is time dependent, multistate models provide an easily understandable framework to define and estimate attributable mortality. The approach is capable of handling competing events, which are omnipresent in clinical research and censoring.

High resolution TDL spectroscopy of the Ar-CH4 complex.

The spectrum of the weakly bound complex Ar-CH4 in the 7 microm region was discovered, analysed, and compared with a spectrum, predicted from ab initio calculations. The measurements were made by probing a supersonic gas expansion with a tunable diode laser (TDL). Several bands of Ar-CH4 associated with different ro-vibrational transitions of the v4 vibration of CH4 were recorded and analysed in a spectral region from 1295 to 1330 cm(-1). In particular the following transitions were studied: j = 1 <-- 0 (at 1311 cm(-1)) reported in Pak et al. [Z. Naturforsch. 53 (1998) 725], j = 0 <-- 1 (at 1301 cm(-1)), j = 2 <-- 1 (at 1316 cm(-1)), and j = 3 <-- 2 transitions (at 1322 cm(-1)). Here, j denotes the angular momentum of the methane unit inside the complex. Analysis of the recently recorded j = 1 <-- 1 transitions at about 1306 cm(-1) in the region of methane Q(1) is in progress. The experimental results are compared with ab initio calculations. The close agreement between observed and ab initio spectra is convincingly demonstrated with respect to the gross spectral features, including many details of the spectra.

Decreased mivacurium constant infusion requirements with defasciculating doses of pancuronium.

This study was designed to verify a technique in which the pharmacologic profile of mivacurium infusions could be altered by small doses of pancuronium to reduce the infusion requirement without altering the subsequent recovery kinetics. Thirty ASA physical status I or II patients were randomized into two groups in a blinded fashion. One group was administered pancuronium 10 micrograms/kg followed by pancuronium 2.5 micrograms.kg-1.h-1 thereafter. The control group was given identical volumes of saline. Subsequently, all patients were given an initial bolus of mivacurium, and anesthesia was maintained using a nitrous oxide/ alfentanil technique. When the thenar electromyogram response to supramaximal train-of-four stimulation returned to 5% of baseline, a mivacurium infusion was begun in both groups, and the infusion rate required to maintain the electromyographic response at 1%-10% of baseline was determined. At the conclusion of the procedure, the infusion was terminated and the recovery profile ascertained. The mivacurium infusion requirement for the group receiving the pancuronium supplementation was 2.77 +/- 1.38 micrograms.kg-1.min-1 (mean +/- SD), which represented a 49% decrease compared with the group that used mivacurium alone which required an infusion rate of 5.43 +/- 1.85 micrograms.kg-1.min-1. No statistically significant difference was found in the recovery profiles of the two groups when the infusion was terminated. We conclude that the addition of a small amount of pancuronium decreased the required mivacurium infusion rate by nearly 50% without affecting the spontaneous recovery when terminating the infusion.