Fig 1.
A) Example of EEG processing and clinical data collected for one patient. This panel illustrates the correlation made between the EEG and clinical data gathered. (Top) 30-second segments of EEG at selected points of time to illustrate the relationship between the BSP values and the time domain EEG pattern. (Bottom) 48 hours of binary EEG (Bin), BSP and medication used. In the binary EEG plot, suppressions are white and non-suppression periods are black. In the plot of BSP, the target BSP of 0.8 is indicated by the solid green line; the upper and lower bound of the reference range (i.e. BSP 0.65 and BSP 0.95) are indicated by the dashed green line; and the measured BSPs are shown in black. In the medication plot, solid lines show the rates of infusion of IVADs used and hollow markers indicate boluses. Periods with intent to achieve EEG burst suppression are highlighted with a light green bar. B) Overview of all patient profiles and infusion medication used. Percentage of total anesthetic time for each medication or combinations of medications used. Refer to the legend of Table 1 for annotations of abbreviations.
Table 1.
Summary characteristics of patients and etiology.
Fig 2.
Example BSPs from 12 patients demonstrate the large degree of intra-patient variability in BSP achieved maintained on constant doses of IVADs.
Solid green lines indicate the reference of BSP 0.8 and the dashed green lines indicate the reference range 0.65–0.95. The blue line shown is the linear regression line for the BSP data. A) Increasing BSP over time. B) Approximately constant BSP over time. C) Decreasing BSP over time D) Varying up and down over time. For each panel A–D), we deliberately chose examples with low, median and high median BSP values to show that the trends are not unique to BSP ranges.
Fig 3.
Comparison of BSP values obtained for similar combinations of IVADs given to different patients.
We identified twelve groups of patients, who received infusions at the same weight-normalized rates, and compared the distribution of BSPs achieved in patients within each group. Numbers associated with the boxplots indicate the probability of a sample from the distribution with the lower median is smaller than a sample from the distribution with the higher median. Horizontal lines are used to indicate which pairs are being compared for sets with data from more than two patients. Unlabeled pairs within sets are different with probability one. The infusion rates for each patient group were as follows: Patients belonging to groups 1 to 3 received midazolam infusion only at 0.1, 0.3 and 0.4 mg/kg/hr respectively. Patients belonging to group 4 received both midazolam (0.1 mg/kg/hr) and propofol (3.0 mg/kg/hr). Finally, patients belonging to group 5–12 received propofol infusion only at 0.6, 1.7, 2.6, 2.8, 2.9 and 3.0 mg/kg/hr, respectively.
Fig 4.
Measures of level of burst suppression achieved.
a) Percentage of time spent within and outside of the reference BSP range in individual patients. Indices representing nRSE patients start with ‘N’ and indices representing aRSE start with ‘A’. Ideally, all patients should be on target (green) for 100% of time. Yet in many patients, the measured BSPs fall below the reference range (blue), and in some cases the measured BSPs overshoot the reference range (red). b—c) Posterior probability distributions for the probabilities that BSPs achieved was accurate and reliable in the nRSE and aRSE patient groups. The numbers associated with each distribution are the maximum a posteriori estimate and 95% Bayesian credibility intervals of the distributions.