We’ve done a series of columns on delirium, including our Patient Safety Tips of the Week for October 21, 2008 “Preventing Delirium”, October 14, 2009 “Managing Delirium”, February 10, 2009 “Sedation in the ICU: The Dexmedetomidine Study”, and March 31, 2009 “Screening Patients for Risk of Delirium”. Delirium is prevalent, costly (in both human and financial terms), difficult to recognize, and potentially preventable.
Most outcome studies done on delirium in the ICU have focused primarily on medical rather than surgical populations. Now a new study (Lat et al. 2009) looks at mechanically ventilated patients in surgical and trauma ICU’s. Expectations were that the prevalence of delirium in these ICU patients would be lower because they were, in general, younger and lacking many of the comorbid conditions typically seen in medical ICU patients. Yet, using the CAM-ICU tool and Richmond Agitation and Sedation Scale tool daily, they found delirium at some point in the ICU stay for 63% of these patients. Patients who developed delirium had more ventilator days and longer ICU and total hospital lengths of stay independent of the illness severity or injury severity. These patients also had cumulatively larger doses of lorazepam and fentanyl. They did not find an association with mortality as seen in prior studies but did not have long-term followup on their patients. The study highlights the high prevalence of delirium in all ICU patients and especially the importance of optimizing the use of both sedatives and analgesics in the ICU population.
Use of sedation and analgesics in mechanically ventilated patients is universal in ICU’s. However, the problem of oversedation is widespread. Misperceptions about the level of sedation are striking. One study (Weinert et al 2007) showed that only 2.6% of nursing staff felt that their patients were oversedated when objective criteria documented oversedation in a third of these ICU patients. They also noted that time of day may influence one’s interpretation of sedation level.
One of the biggest reasons for oversedation is the use of continuous infusions of sedating agents, especially in the elderly and those with hepatic disease (Devlin 2008). This is especially problematic when sedatives with long half lives (eg. lorazepam) are being used. Yet we continue to be surprised at how many ICU’s still use continuous infusion of sedating agents.
Ventilator weaning protocols that include spontaneous breathing trials have been supported by numerous clinical trials. Also, a number of clinical trials have shown that either use of intermittent (as opposed to continuous) sedation or daily interruption of sedation have reduced the need for mechanical ventilation. The ABC trial (Awakening and Breathing Controlled trial) (Girard et al 2008) was a multicenter prospective controlled trial that paired the use of spontaneous breathing trials (SBT’s) with spontaneous awakening trials (SAT’s) in comparison to a usual care group in mechanically ventilated ICU patients. Validated tools, including the Richmond Agitation-Sedation Scale (RASS) and the CAM-ICU were used in the assessments. Results demonstrated patients in the intervention group had more ventilator-free days, shorter ICU and total hospital lengths of stay, and a 32% better survival at one year.
A second recent paper (van Eijk et al 2009) on delirium in the ICU compared two commonly used tools to detect delirium. They found the CAM-ICU tool had higher sensitivity (64%) and negative predictive value, whereas the ICDSC (Intensive Care Delirium Screening Checklist) had higher specificity and positive predictive value. Overall, the CAM-ICU tool picked up more cases of delirium. However, the most important point of the paper was really that the physicians providing most of the care to the ICU patients (i.e. residents) had a sensitivity of only 14%. Fellows and intensivists, on the other hand, had sensitivities of 63%. The study shows the importance of using structured tools to look for delirium since the physicians are not cognizant of most cases.
To complicate matters, two papers (Kilbride et al 2009; Oddo et al 2009) recently appeared in the neurology and critical care journals pointing out the frequent occurrence of nonconvulsive seizures in ICU patients, as detected by continuous EEG monitoring. Up to 10-20% of such ICU patients, particularly those admitted with sepsis, may have electroencephalographic seizure activity. Obviously, such activity may account for variable level of consciousness or attention and might easily be confused with delirium in this patient population.
The lessons learned from this week’s group of studies:
We would strongly recommend that hospitals review their current sedation management strategies and protocols in their ICU’s. While it may be easier in the short run to care for the patient who is oversedated, that oversedation in the long term increases the likelihood of prolonged ventilator therapy, prolonged ICU and hospital lengths of stay, ventilator-associated pneumonia (VAP), delirium, and death. Sedation protocols should be tailored to the specific patient, using validated assessment tools, and include regular assessment to determine whether continued use of sedatives and analgesics is necessary. A good discussion of goal-directed sedation is available at the Vanderbilt University ICU Delirium and Cognitive Impairment Study Group site and includes a copy of their sedation protocol.
Lat I, McMillian W, Taylor S, et al. The impact of delirium on clinical outcomes in mechanically ventilated surgical and trauma patients. Critical Care Medicine 2009; 37(6):1898-1905, June 2009
Weinert CR, Calvin AD. Epidemiology of sedation and sedation adequacy for mechanically ventilated patients in a medical and surgical intensive care unit. Critical Care Medicine. 35(2):393-401, February 2007.
Devlin JW. The pharmacology of oversedation in mechanically ventilated adults.
Current Opinion in Critical Care 2008; 14(4):403-407, August 2008.
Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial. The Lancet 2008; 371: 126 - 134, 12 January 2008
Richmond Agitation-Sedation Scale
van Eijk MMJ, van Marum RJ, Klijn IAM, et al. Comparison of delirium assessment tools in a mixed intensive care unit. Critical Care Medicine 2009; 37(6): 1881-1885
Vanderbilt University ICU Delirium and Cognitive Impairment Study Group. Patient-Oriented Goal-Directed Sedation Delivery.