Table 3.
Risk Factors for Delirium
| Variable* | Odds Ratio | P Value** |
|---|---|---|
| Mental status on previous day | 0.001 | |
| Delirious vs. normal | 26.5 (11.9, 58.9) | |
| Comatose vs. normal | 44.9 (19, 105.8) | |
| Benzodiazepine dose (midazolam equivalents) in previous 24 hours † | 6.8 (3.1, 15) | <0.001 |
| Opiate dose (fentanyl equivalents) in previous 24 hours ‡ | 0.5 (0.4, 0.6) | <0.001 |
| Methadone dose in previous 24 hours | 0.7 (0.5, 0.9) | 0.02 |
| Baseline variable component*** | 0.6 (0.3, 1.0) | 0.19 |
Odds ratios are presented using the 25th and 75th percentile values as comparators. For example, patients receiving 60 mg of benzodiazepines (expressed as midazolam equivalents) in the previous 24 hours had 6.8 times higher odds of delirium the following day (vs. a normal assessment) than those receiving 5 mg of benzodiazepines.
P-values are calculated using group added last tests for the overall effect of each variable, including all related terms. For example, the p-value for mental status on the previous day includes model terms for delirium vs. normal status as well as for coma vs. normal status; the p-value for benzodiazepines includes both the linear and nonlinear terms.
For the purpose of this study, all benzodiazepines were converted to midazolam equivalents, such that 1 mg of midazolam was equal to 0.4 mg of lorazepam and 2 mg of diazepam.
For the purpose of this study, all intravenous opioids administered were converted to fentanyl equivalents, such that 10 mg of morphine was equal to 150 micrograms of fentanyl.
In order to conserve power, principal component analysis was used as a data reduction technique to calculate a single value incorporating age, acute physiology component of the APACHE, history of alcohol/substance abuse, burn percentage, and presence of an inhalation injury.