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Abstract & Commentary
By Linda L. Chlan, RN, PhD, FAAN
Dean's Distinguished Professor of Symptom Management Research, The Ohio State University, College of Nursing
Dr. Chlan reports that she receives grant/research support from Hospira.
SYNOPSIS: ICU patients with initial "delirium present" assessment findings can transition to "delirium absent" when sedative infusions have been suspended, and these patients have similar outcomes when compared to patients with no "delirium present" findings during their ICU stay.
Delirium, or acute confusion, has become an all-too-common ICU-acquired syndrome for critically ill patients receiving mechanical ventilatory support. There are several known risk factors and contributors to delirium, such as hypertension, higher illness severity, sepsis, sleep deprivation, and receipt of medications such as sedatives. The occurrence of delirium in mechanically ventilated ICU patients is associated with increased morbidity and mortality, independent of illness severity. Not surprisingly, there has been an increase in research over the past decade that highlights the importance of regular assessment for delirium with valid instruments such as the Confusion Assessment Method-ICU (CAM-ICU).1
Patel and colleagues conducted a single-center, prospective, observational, blinded study to investigate whether delirium would abate when sedative infusions were halted. Two investigators conducted serial delirium assessments each day, before and after sedation interruption. However, the investigators were blinded to each other’s assessment findings and to whether the assessment was before or after the sedation interruption protocol. Further, the infusion pumps and tubing were covered so the investigators performing the CAM-ICU assessments would not able to determine whether the sedative or opiate was currently being infused. These serial delirium assessments were performed each day until the sedative infusions were discontinued. CAM-ICU assessments were then conducted once daily after sedative and opioid medications were discontinued until discharge. The main outcome for this study was the proportion of days of no delirium (ND) vs rapidly reversible, sedation-related delirium (RRSD) vs persistent delirium (PD). Secondary outcomes of interest were ventilator-, ICU- and hospital days, disposition after discharge, and 1-year mortality.
ICU patients (n = 102) receiving mechanical ventilation who were ≥ 18 years of age and who were on a daily sedative interruption protocol for less than 48 hours were studied. Patients with dementia, central nervous system diseases (stroke, cardiac arrest, active seizure activity), or alcohol withdrawal were not included. Median age of patients was 59.8 years, with 55% of the sample being male. ICU admission diagnoses of the patients, whose median APACHE II scores were 21.5 (interquartile range, 17-28), were respiratory failure, ventilatory failure, and sepsis. Overall, 89% of patients had at least 1 day of delirium when assessed before sedation interruption, whereas this number decreased to 77% delirium present after the sedation was interrupted for the "sedation holiday." Median days in delirium before sedation interruption were 4 compared to 3 post-sedation interruption. Patients were 10.5 times more likely to be classified as "delirium present" when they were assessed prior to sedation interruption. There was no difference in ventilator days, ICU days, or hospital days between the ND and RRSD group of patients. The PD group had higher ventilator days, ICU days, hospital days, and increased 1-year mortality as compared to the ND and the RRSD groups. More patients in the ND and the RRSD groups were discharged home (80%) as compared to the PD group (50%).
The findings from this study by Patel et al highlight the clinically important contribution of sedative and opioid medications when conducting delirium assessments. Given the greater number of patients who were found to be delirious when sedative medications were infusing, clinicians are advised to carefully time their delirium assessments with sedation interruption protocols for the most accurate findings.
The investigators instituted a very effective blinding protocol, which adds significant strength to the study design. The two investigators conducing the daily delirium assessments were not aware if sedative medications were infusing or not, nor was each of them aware of the other investigator’s assessment findings. These blinding strategies could be used in other studies to examine patient outcomes of persistent vs rapidly reversible, sedation-related delirium.
The reduction in the number of patients with delirium present after sedative infusions were halted calls into question the statistics on the percentages of patients with delirium (up to 80% in some studies) reported in previous studies. Perhaps delirium is not so prevalent overall in some mechanically ventilated patients, or is it only present due to the influence of potent CNS medications? Only further research will contribute answers to this puzzling question.
Limitations from this study include that the participating MICU is one of the leading centers in the U.S. conducting research and advancing the clinical practices of daily awakenings and spontaneous breathing trials to benefit patient outcomes. Thus, these practices are already an integral part of the unit’s culture. The generalizability of the findings to ICUs where these practices are not as imbedded in routine clinical practice may be more limited.
1. Ely EW, et al. Delirium in mechanically ventilated patients: Validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA 2001;286:2703-2710.