Cluster www.selleckchem.com/products/Erlotinib-Hydrochloride.html numbers are arbitrarily assigned. Brighter shades of red indicate increased probability of death over baseline while brighter shades of green indicate increased probability of life over baseline.Cluster representation of novel physiological relationshipsHaving determined that 1) univariate analysis did not provide adequate predictors and 2) that hierarchical clustering provided superior prediction of outcomes, we next sought to determine why this was the case. We hypothesized that the clusters contained new physiological relationships and that the correlations between variable pairs would differ according to patient state. Furthermore, we believed that these changing correlations would likely reflect changing physiological relationships depending on the changing injury or resuscitation state of a patient.

To test this we next examined the correlations between pairs of variables within each cluster. To confirm that our correlations were statistically significant, we performed bootstrap resampling and label shuffling. Figure Figure66 shows the correlation coefficients of variable pairs for cluster 4, the cluster most closely associated with death, and cluster 1, which was most closely associated with good outcome. Examination of these results was very revealing and provided proof of both the discrimination of the clustering technique and the ability of this technique to identify physiologic relationships that would otherwise be impossible to discern.Figure 6Correlations of pairs of variables between clusters 1 (live) and 4 (die). Cluster 1 is shown in blue and cluster 4 in green.

Correlation coefficients are shown on the lines and the variables above each plot.Several variables showed no correlation or difference between clusters 1 and 4. For example, as expected, compliance and mGlucose were not correlated in either cluster (Figure (Figure6a).6a). This makes physiologic sense as there should be no obvious correlation between these disparate variables, and indeed we can determine no reason a relationship between these variables should be reflected in patient outcome. Furthermore, these two variables were not closely clustered in the physiologic variable dendrogram (Figure (Figure1).1). Another pair of variables with minimal correlation and no discrimination between outcome clusters is PmO2 and mGlutamate (Figure (Figure6b6b).

Other pairs of correlations represent pertinent physiology Batimastat that should be similar in patients with any outcome; the strong correlation between mLactate and the ratio between muscle lactate and pyruvate (mLP) is similar in clusters 1 and 4. (Figure (Figure6c).6c). This represents what we know physiologically to be true, namely that as anaerobic respiration takes place there is an increase in both lactate production and pyruvate consumption, resulting in an increase in mLP.