Abstract & Commentary
Sedative Medications: Challenging to Predict Clinical Effectiveness in Some Mechanically Ventilated Patients
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: This pilot study reports that dexmedetomidine might be the sedative of choice for less ill mechanically ventilated ICU patients who take antidepressant medications at home.
- SOURCE: Smithburger PL, et al. Patient predictors of dexmedetomidine effectiveness for sedation in intensive care units. Am J Crit Care 2014;23: 160-165.
Administration of sedative therapy is a mainstay in today’s ICU care of
critically ill patients receiving mechanical ventilatory support. Promoting adequate ventilation and gas exchange while managing distressful symptoms such as pain and anxiety experienced by patients remains a vexing clinical challenge. Clinical practice guidelines suggest that the "ideal" patient be comfortable, alert, and only lightly sedated. One medication that might meet this guideline is dexmedetomidine. This agent is classified as a selective alpha-2 adrenergic receptor agonist which is desirable for its light sedative properties that does not induce respiratory depression. The available literature is unclear on the appropriateness of dexmedetomidine and the specific patients in which it is most effective as a first-line sedative choice. Thus, the pilot study conducted by Smithburger and colleagues aimed to determine whether specific patient characteristics were associated with the effectiveness or ineffectiveness of dexmedetomidine as a sedative agent in mechanically ventilated patients.
The investigators conducted a single-center, single-MICU, 6-month observational study. The purpose was to generate hypotheses for future studies to determine patient characteristics associated with adequate, effective sedation with dexmedetomidine. For this study, the selection of a specific sedative for individual patients and the dosing of these medications was based on individual physician orders and clinical protocols for the MICU. During the study period, 38 patients received dexmedetomidine as the sedative of choice. Of these patients, 50% were female, with a mean age of 52 years (SD 13.7) admitted to the MICU in need of mechanical ventilation. Sedation ineffectiveness with dexmedetomidine was defined as "the addition of a continuous infusion of a sedative at any dose or the reinitiation of a previously discontinued sedative while dexmedetomidine was being administered." Level of sedation was determined every 2 hours by nursing staff using the Sedation Agitation Scale per unit protocol. A target sedation level was determined to be 3-4, indicative of "waking up with verbal or physical stimuli or easily arousable." A number of patient characteristics were considered in the analysis as predictive of dexmedetomidine effectiveness or ineffectiveness, such as antidepressant use at home, heavy alcohol consumption, history of depression, illness severity, etc. The interested reader is advised to refer to the table in the original article for the list of clinical indicators considered in the analysis.
Overall, dexmedetomidine was judged to be ineffective for 50% of the sample and effective for sedation in 29% of the patients; the remaining 21% of the sample were unable to be classified due to clinical condition. Lower illness severity (APACHE II scores) and home antidepressant use were found to favor effective dexmedetomidine sedation. In fact, lower illness severity was an independent factor related to effective sedation with dexmedetomidine. Other clinical factors such as amount of narcotics, benzodiazepines, antipsychotics, or total propofol infused did not differ between those patients who had effective sedation with dexmedetomidine as compared with those who had ineffective sedation.
Smithburger and colleagues present the findings from an observational study conducted in one MICU to determine patient factors that might be used to predict who will and will not receive effective sedation with dexmedetomidine. While any medication, including sedatives, can have varying responses in critically ill patients, clinicians are still left to decide which sedative may best meet individual patient needs. However, we should not expect one sedative to meet the needs of all patients in the ICU. The findings from this small observational study suggest that dexmedetomidine may be more effective in patients who are less ill and taking antidepressant medications at home. These findings need to be tempered by a number of limitations. First, there is little information presented on these MICU patients, such as admission diagnosis, length of ICU stay, length of ventilatory support, what agents were administered prior to dexmedetomidine, or if dexmedetomidine was the first agent of choice. It will be informative to read about future prospective, controlled studies by Smithburger and colleagues that will hopefully shed some light on the appropriate administration of dexmedetomidine and other sedatives based on evidence, not on individual physician preferences.