Feasibility of a sedation wake-up trial and spontaneous breathing trial in critically ill trauma patients: A secondary analysis

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1 Intensive and Critical Care Nursing (2013) 29, Available online at j o ur nal homepage: ORIGINAL ARTICLE Feasibility of a sedation wake-up trial and spontaneous breathing trial in critically ill trauma patients: A secondary analysis Milagros I. Figueroa-Ramos a,, Carmen Mabel Arroyo-Novoa a, Geraldine Padilla b, Pablo Rodríguez-Ortiz c, Bruce A. Cooper b, Kathleen A. Puntillo b a University of Puerto Rico, Medical Sciences Campus, School of Nursing, Puerto Rico b University of California, San Francisco, School of Nursing, United States c University of Puerto Rico, Medical Sciences Campus, School of Medicine, Puerto Rico Accepted 4 May 2012 KEYWORDS Sedation; Spontaneous breathing; Trauma; Delirium Summary Objectives: To determine the feasibility of conducting a sedation wake-up trial (SWT) plus a spontaneous breathing trial (SBT) in critically ill trauma patients based on the ability to implement the combined intervention; to measure and describe patients physiological responses; and to maintain patient safety. Methods: A secondary analysis of the intervention group from a trial of 20 mechanically ventilated patients receiving SWT plus SBT in a trauma-intensive care unit. Results: Patients passed 67% of the 39 SWTs performed; those who failed presented RASS scores of +1 and +2 (70%), tachycardia (15%) or ventilator asynchrony (15%). Eighteen patients tolerated their first SBT, and after the second SBT, more than half of the patients were discontinued from the mechanical ventilator. A significant increase from the beginning to the end of the SWT was found in heart rate (p =.021), respiratory rate (p =.043) and systolic blood pressure (p =.04). Although these measures increased significantly, their overall mean did not increase by 20%. Conclusion: SWT plus SBT was well tolerated and successfully implemented. Our data showed that it is not necessary to withhold continuous-infusion analgesia during the SWT Elsevier Ltd. All rights reserved. Corresponding author at: PO Box , San Juan , Puerto Rico. Tel.: x3105; fax: addresses: milagros.figueroa@upr.edu,milliefr@hotmail.com (M.I. Figueroa-Ramos) /$ see front matter 2012 Elsevier Ltd. All rights reserved.

2 Sedation wake-up trial and spontaneous breathing trial 21 Implications for clinical practice SWT plus SBT is clinically feasible. The implementation of SWT plus SBT appears to be a safe intervention for trauma patients. SWT plus SBT intervention provides an alternative to the management of sedation in mechanically ventilated trauma patients. Introduction Patients in trauma-intensive care units (TICUs) on mechanical ventilation (MV) often receive continuous intravenous (IV) sedatives as part of supportive treatment. Sedatives are often given in order to improve patient comfort and safety and to minimise distress caused by the complexity of ICU care (Hooper and Girard, 2009; Sessler and Pedram, 2009). Sedation management in critically ill trauma patients is a multifaceted challenge. Complications that occur as a result of the mechanisms of the injury (e.g., acute respiratory distress syndrome [ARDS] and sepsis) make this kind of sedation management challenging (Robinson et al., 2008). Negative consequences of sedation due to inappropriate management can occur. Over-sedation may lead to prolonged MV, an increased length of stay, an increased number of neurological tests and greater delirium (Sessler and Pedram, 2009). Under-sedation may lead to anxiety, ventilator asynchrony, increased nursing workload, wound dehiscence and self-removal of tubes (Dasta and Kane-Gill, 2009). An individualised sedation level targeted according to the patient s clinical condition could enhance patients responses to sedation management. Daily interruption of sedation, which is known by a variety of names, but which we call a sedation wake-up trial (SWT), has been introduced as an option for managing sedation needs in ICU patients and has resulted in improved patient outcomes (i.e., decrease in duration of mechanical ventilation [MV], length of ICU stay) (Kress et al., 2000). The addition of a spontaneous breathing trial (SBT) to an SWT has also contributed to improved patient outcomes (Girard et al., 2008). Several studies have addressed the benefits, feasibility and safety of the SWT (Girard et al., 2008; Kress et al., 2003, 2007; Schweickert et al., 2004), but these studies have not included data on trauma patients. Indeed, it has been suggested that SWTs performed on young trauma patients may be dangerous and not well tolerated (Robinson et al., 2008). The goal of this secondary analysis was to describe the feasibility and safety of conducting an SWT plus an SBT on trauma patients. The primary aims of this secondary analysis were the following: (1) to explore the effectiveness of the screening criteria for both SWT and SBT; (2) to describe patient responses to the combined intervention, including pass/fail criteria, physiological indices (heart rate [HR], blood pressure [BP], respiratory rate [RR], oxygen saturation [SpO 2 ]), agitation/sedation levels and level of consciousness both before and at the end of the SWT; (3) to evaluate delirium and pain during each SWT; (4) to record the length of time to awakening after sedative interruption; and (5) to examine patient safety according to the occurrence of adverse events related to SWT and SBT. A secondary aim was to determine the reasons that patients remained on a mechanical ventilator after successfully passing an SBT. Methods The database used was from a prospective interventional study that determined whether an SWT plus SBT contributes to a reduction in the occurrence of delirium in critically ill trauma patients. Data from patients in the intervention group who received an SWT plus SBT are included in this report. The Institutional Review Board of the University of Puerto Rico, Medical Sciences Campus and the Committee on Human Research of the University of California, San Francisco, approved the study. The ClinicalTrials.gov identifier for the study is NCT Setting and study patients The study was conducted in the TICU of Trauma Hospital at the Puerto Rico Medical Center, San Juan, Puerto Rico. All consecutive patients admitted to the TICU were screened during their first 24 hours of admission. Patients who were 21 years of age, were receiving MV and a continuous sedative infusion, and had a Richmond Agitation Sedation Scale (RASS) score of 4 or 5 were included in the study. Excluded from the study were patients who had baseline neurological or psychiatric diseases, head trauma, an acute neurological injury with a Glasgow Coma Scale score <8, a history of alcoholism or drug dependence; also excluded were individuals whose death was expected within 24 hours (i.e., Acute Physiology and Chronic Health Evaluation [APACHE] II score 30) (Knaus et al., 1985). Measures The RASS was used to measure agitation and sedation levels based on three states: agitated (+1 to +4), calm/alert (0) and sedated ( 1 to 5) (Ely et al., 2003; Sessler et al., 2002). A non-invasive physiological monitor, the Bispectral Index (A-2000 BIS-XP TM, Aspect Medical Systems, Norwood, MA), was used to measure the level of consciousness. BIS scores range from 0 (isoelectrical line) to 100 (alert), with scores decreasing according to the depth of sedation. In order to determine the presence of pain, patients were asked to nod their heads if they were in pain and close their eyes if they were not. The Confusion Assessment Method for

3 22 M.I. Figueroa-Ramos et al. the Intensive Care Unit (CAM-ICU), Spanish version, was used to measure delirium (Vanderbilt University, 2002). The CAM- ICU has been validated in large ICU populations (Ely et al., 2001a,b; Guenther et al., 2010; Tobar et al., 2010). Procedure Since a patient had to be under deep sedation to be eligible to participate in the study, informed consent was obtained from the patient s authorised representative. Once patients were able to do so, they provided consent for their continued participation in the study. Sedation wake-up trial procedure Every morning after the day of admission, patients were screened to determine whether or not they could undergo an SWT. Physiological indices (HR, BP, RR, SpO 2 ), the RASS and the BIS were measured before the initiation of the SWT. If a given patient met the passing criteria (Table 1), the SWT was started. That is, continuous intra-venous (IV) sedatives were interrupted for a maximum of four hours. Those who failed during screening were reassessed in 24 hours. Because these trauma patients required pain management, the continuous infusions or scheduled intermittent doses of opioids were not interrupted during the SWT. For those patients who had a RASS score from 0 and 5 at the end of the SWT, the sedative treatment was changed to intermittent dosing as needed for agitation or anxiety. For patients failing the SWT, continuous sedative infusion was resumed at half of the previous dose and titrated to the target level of sedation established (i.e., RASS 3 to 1). In addition, if a patient had a RASS of +3 to +4, a sedative bolus was given. Those patients who had a RASS score of 3 to 5 at the end of the SWT were screened for an SBT in 24 hours. Physiological indices, the RASS, the BIS, delirium and the presence of pain were measured at the end of the SWT; if the patient was awake; or before the resumption of sedatives if the patient became agitated. Patients were considered to be awake when they were able to comprehend the oral instructions requesting them to perform at least three of the following actions: opening their eyes, using their eyes to follow the investigator, squeezing the investigator s hand, and sticking out their tongue. Significant changes in physiological indices (HR >20% from baseline or >120 beats/minute; systolic BP >20% from baseline or >180 mmhg; RR >20/minute; and SpO 2 <90%), or the presence of pain or delirium was reported to the physician and to the nurse in charge. Spontaneous breathing trial procedure Patients who passed the SWT with a RASS score of 0 to 2 were screened for an SBT. When a given patient met the screening criteria (Table 1), then the mechanical ventilator mode was changed to continuous positive airway pressure (CPAP), for two hours or until that patient failed the SBT (Table 1). The mechanical ventilation was changed to the previous mode and parameters if a patient failed the SBT. However, when a given patient passed the SBT, the physician in charge would then make a decision about whether or not to extubate that patient. All of the previous steps were determined by the study protocol and were strictly followed by the principal investigator (MIF) and the co-investigator (CMA). Table 1 Screening and failing criteria for sedation wake-up trial and spontaneous breathing trial. Sedation wake-up trial Spontaneous breathing trial Screening criteria PaO 2 /FIO 2 ratio 200 mmhg SpO 2 >90% No NMBA FIO 2 50% No agitation PEEP 7.5 cm H 2 O NIF 25 in a 5 minutes period No agitation No dopamine or dobutamine 5 g/kg/minute No noradrenaline 2 g/minute No vasopressin or milrinone at any dose Failing criteria Sustained anxiety RR >35 or <8 breaths/minute for 5 minutes Agitation SpO 2 <90% for 5 minutes RR >35 breaths/minute for 5 minutes Dysrhythmias SpO 2 <90% for 5 minutes Changes in mental status Dysrhythmias Respiratory distress Ventilator asynchrony Sustained anxiety = a RASS score of +1 for more than 5 minutes; respiratory distress = an increase in respiratory rate with the use of accessory muscles; dysrhythmias were identified using the bedside monitor; ventilator asynchrony = a lack of coordination between the patient and mechanical ventilator and was measured using the flow, pressure and volume waves of the ventilator; changes in mental status = a change in patient alertness. PaO 2 /FIO 2, partial oxygen pressure/fraction of inspired oxygen; NMBA, neuromuscular blocking agents; SpO 2, saturation of peripheral oxygen; PEEP, positive end-expiratory pressure; NIF, negative inspiratory force; RR, respiratory rate.

4 Sedation wake-up trial and spontaneous breathing trial 23 Statistical analysis Descriptive statistics were used to quantitatively describe the patients pass/fail rates with regard to both SWT and SBT, the occurrence of delirium or pain at the end of a given SWT, and the length of time to awakening after sedative interruption. A multilevel regression model was used to compare changes in physiological indices (HR, BP, RR, SpO 2 ), RASS scores and BIS scores occurring before and at the end of the SWT. Multilevel regression (also called linear mixed models, hierarchical linear models or random regression models) is superior to traditional methods of analysis for longitudinal data because it allows the estimation of change without dropping those observations for which some data are missing, among other advantages (Albert, 1999; Gueorguieva and Krystal, 2004; Hedeker and Gibbons, 2006; Singer and Willett, 2003). Estimates are unbiased in the presence of missing data as long as the mechanism of missingness is ignorable (e.g., missing at random) (Little and Rubin, 2002; McKnight et al., 2007; Schafer and Graham, 2002). In this study, SWT assessments were collected for up to six days. Some patients provided data for only a single day (i.e., successfully passed their first SWT), while others provided data from two to six days. Traditional repeated-measures ANOVA would have discarded those patients for whom data were incomplete, even if only for a single day. Models were estimated to test the effects of assessment time, day and the day-by-time interaction for each outcome separately. Descriptive statistics were also used to describe adverse events related to the SWT and SBT and explore reasons that patients remained on the mechanical ventilator after passing the SBT. Statistical analyses were performed using SPSS version 16.0 and STATA version Results Patients were enrolled from April 20, 2009 to August 10, A total of 20 patients were included in the analysis. The data are expressed as median (interquartile ranges [IQR]). The majority of patients were male (n = 17, 85%), were 31 (IQR 23 58) years of age, and had a median APACHE II score of 11 (IQR 10 14) at TICU admission. The mechanisms of trauma were gunshots (n = 8, 40%), motor vehicle crashes (n = 7, 35%), falls (n = 4, 20%) and stabbings (n = 1, 5%). Seventeen patients (85%) required surgical intervention. Patients spent 12.5 (IQR ) days on mechanical ventilation, and the length of TICU stay was 10.5 (IQR ) days. Twelve patients developed one or more complications: ARDS (n = 7, 35%), sepsis (n = 5, 25%), ventilator associated pneumonia (n = 4, 20%) and hypertensive crisis (n = 1, 5%). Screening criteria Sedation wake-up trial Twenty patients did not meet the SWT screening criteria a total of 51 times (58%) because of their partial oxygen pressure/fraction of inspired oxygen (PaO 2 /FIO 2 ) ratios being less than 200 (90%), the use of neuromuscular blockers agent (NMBA) use (8%), or agitation (2%). Sixteen of the 20 patients met the SWT screening criteria the first day after study enrollment; those who did not (n = 4), met the screening criteria by the seventh day (IQR 3 9.5) after enrollment. Spontaneous breathing trial The SBT was performed on 19 patients. One patient died before meeting the SBT screening criteria. The 19 patients with RASS scores of 0 to 2 were screened 74 times for eligibility for SBT. In 25 attempts (34%), these patients did not meet the screening criteria because of having an FIO 2 >50% (44%), a negative inspiratory force (NIF) > 25 cm H 2 O (40%) and a positive end-expiratory pressure (PEEP) 7.5 (16%). Patient responses to the SWT and SBT SWT pass/fail criteria Patients passed 67% of the 39 SWTs performed, and their continuous sedative infusions were switched to intermittent sedative dosing. Patients spent a median of seven (IQR ) days on mechanical ventilation prior to successful SWT. Specific findings from the SWTs are summarised in Table 2. After being changed to intermittent sedative dosing, patients had daily RASS scores of 0 (IQR 1 to 0) in 113 daily RASS assessments. Of these, RASS scores were +1 in five daily assessments. Thirteen of 20 patients passed the SWT the day after enrollment. Patients received one (IQR 1 3) SWT before being switched from continuous to intermittent sedative administration. One patient failed all six SWTs performed before he died. First SWT This section of the report includes an in-depth description of each patient s (20 patients) first experience with SWT. For their first SWTs, patients were receiving midazolam (n = 15, 75%), propofol (n = 4, 20%) or lorazepam (n = 1, 5%). Durations of the first SWTs are summarized in Table 3. At the end Table 2 Sedation wake-up trial. Sedation wake-up trial Frequency (%) Total 39 Passed 26 (67) RASS 0 6 (23) RASS 1 4 (15) RASS 2 5 (19) RASS 3 9 (35) RASS 4 1 (4) RASS 5 1 (4) Failed 13 (33) RASS +1 to +2 9 (70) Tachycardia 2 (15) Ventilator asynchrony 2 (15) Sedation decision at the end of SWT Intermittent dose 26 (67) Half dose 5 (13) Same dose 6 (15) Bolus and same dose 2 (5) SWT, sedation wake-up trial; RASS, Richmond Agitation Sedation Scale.

5 24 M.I. Figueroa-Ramos et al. Table 3 Duration of the first sedation wake-up trial. Duration n (%) 1/2 hour 2 (10) >1/2 hour, 1 hour 2 (10) >1 hour, 2 hours 4 (20) >2 hours, 3 hours 4 (20) >3 hours, 4 hours 8 (40) and BIS scores and all physiological indices (except for diastolic BP and SpO 2 ) increased significantly from the beginning to the end of the SWT (Table 4). As expected, RASS and BIS scores increased significantly. Although HR, RR and systolic BP increased significantly, their overall means did not increase by more than 20% from the beginning to the end of the SWT. These differences from the beginning to the end of the SWT did not differ depending on the day of the assessment (i.e., there was no day-by-time interaction for any outcome). of their first SWT, seven patients awoke with RASS scores of 0 to 2; nine had RASS scores of 3; one had a score of 4; one had 5; and two patients had positive RASS scores (+1 and +2, respectively). Of the 20 patients, four failed the SWT, having positive RASS scores, tachycardia or ventilator asynchrony. After being switched to intermittent dosing, six patients who had passed their first SWT required a restart of continuous IV sedatives because of a second surgical intervention and/or the development of ARDS (n = 4), a failed extubation (n = 1) or further agitation (n = 1). SBT pass/fail criteria Patients spent 10 (IQR ) days on mechanical ventilation prior to a successful SBT. The patients passed 98% of the 49 SBTs performed. One patient did not tolerate even one SBT because of a decrease in SpO 2. The findings from the SBTs, including the reason or reasons that a given patient remained on the mechanical ventilator after successfully passing the SBT, are illustrated in Fig. 1. Changes in physiological indices A multilevel regression analysis on the 39 SWTs performed showed that, controlling for the day of assessment, RASS Pain and delirium At the end of the 39 SWTs performed, four patients reported having pain in 6 of the SWTs (15%); nine patients experienced no pain in 12 SWTs (31%); and 14 patients were unable to report pain during 21 SWTs (54%). Those who reported having pain did not show restlessness (RASS +1) or agitation (RASS +2) at the end of the SWT. Patients were receiving continuous opioid infusions during 23 SWTs (59%) and intermittent opioids during 16 SWTs (41%). The fact that continuous opioid infusions were not stopped during the SWTs did not prevent the patients from awakening, increasing their RASS scores, or having pain. Only one patient was still deeply sedated (RASS score 4) at the end of one SWT. In those patients who reported having pain at the end of an SWT, either the rate of continuous IV opioids was increased or a bolus of morphine IV was given, and either action was accompanied by a medical order. Of the 39 SWTs performed, four patients exhibited delirium (two hypoactive and two hyperactive) at the end of four SWTs (10%). Nine patients had no delirium at the end of 14 SWTs (36%). Fourteen patients were unable to perform the CAM-ICU at the end of 21 SWTs (54%). The presence of delirium was reported to the physician in charge. Figure 1 Spontaneous breathing trial (SBT) findings. D/C, discontinued; MV, mechanical ventilation; SpO 2, saturation of peripheral oxygen; f/v T, breathing frequency-tidal volume ratio (>100 breaths/minute/ml).

6 Sedation wake-up trial and spontaneous breathing trial 25 Table 4 Changes in RASS, BIS and physiological measures during the sedation wake-up trial. Parameter Beginning SWT End SWT Estimated change p-value RASS 2.8 ± ± BIS 56.0 ± ± HR ± ± RR 16.9 ± ± SBP ± ± DBP 69.9 ± ± SpO (99 100) 99 (98 100) 0.18 a.36 Data are presented as mean ± SD or as median and interquartile range from sample statistics. Statistics are reported, collapsed across days in line with the estimated main effect of wake-up time for the multilevel analysis. Estimated mean change from the beginning to the end of the wake-up trial and p-values are reported from the multilevel regression analysis. a Change in means from the original scale converted back from a natural log scale. RASS, Richmond Agitation Sedation Scale; BIS, bispectral index; SWT, sedation wake-up trial; HR, heart rate; RR, respiratory rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; SpO 2, saturation of peripheral oxygen;, increase;, decrease. Adverse events Two patients self-extubated: one did not require reintubation and the other required re-intubation. While these self-extubations did occur during the study, they did not occur during the four hours of the SWT. One patient failed extubation after having passed the SBT and was reintubated. Discussion This study demonstrated the feasibility of conducting an SWT plus an SBT in trauma patients. All patients except one received both SWTs and SBTs. The patient who did not receive both received only the SWT because he died before meeting the SBT screening criteria. This patient failed all six SWTs. The majority of the patients who did not meet the screening criteria for an SWT had ARDS, with a PaO 2 /FIO 2 ratio less than 200 mmhg. Sedation is used in patients with ARDS to prevent MV resistance and to decrease oxygen consumption (Michaels, 2004). Although continuous IV sedatives were not stopped in patients with ARDS until the condition was resolved, the rate of infusion was adjusted according to these patients needs and medical orders. We found that the majority of patients were young, required only one SWT, and passed the said SWT on the first day after study enrollment, which usually corresponded to the first and second day after TICU admission. Moreover, most study participants did not develop any further restlessness or agitation that required the restarting of continuous IV sedatives. Based on this information, it is important to consider whether these patients really required continuous sedative infusion. Perhaps they would have benefited from intermittent sedative dosing or from the use of analgesics alone. Both the selection of patients with RASS scores of 0 to 2 and the application of specific screening and failure criteria guided the successful implementation of the SBTs. Eighteen patients tolerated their first SBT and, after the second SBT, more than half of the patients were liberated from the mechanical ventilator. Although 18 patients passed the first SBT, some of them were not extubated because they showed risk factors for extubation failure (i.e., abundant secretions, rapid shallow breathing [f/v T ] > 100 breaths/minute/ml and the absence of cuff air leak), as observed by the TICU medical staff. On sixteen occasions (33%), patients successfully passed the SBT and did not exhibit risk factors for extubation failure; however, they were not extubated and MV was continued by their physician. We found some discrepancies in terms of the rate of failure of screening criteria and the rate of completion of both interventions when compared to those same rates from the study carried out by Girard et al. (2008). Our patients did not meet the SWT screening criteria 58% of the time, versus 18% for the Girard study. This difference between the two studies could be due to our inclusion of a PaO 2 /FIO 2 ratio 200 mmhg as an SWT screening criterion. Furthermore, the patients in our study passed the SWT 27% fewer times than did the patients in Girard s study. Patients met the SBT screening criteria in the same proportion in both studies (66%). However, our study showed an extremely low rate of SBT failures compared to what was seen in Girard s study (2% versus 47%). A possible explanation for this discrepancy could be the differences in types of patient (i.e., trauma versus medical) or the duration of the study. We studied each patient over the course of the entire TICU stay (for up to 33 days, instead of the 28 days in the Girard study). Safety concerns (e.g., device removal, patient comfort and respiratory compromise, psychological effects and cardiac ischaemia) related to patient responses to the implementation of SWT have been described previously (O Connor et al., 2009; Tanios et al., 2009). Our results are similar to those found in a study of coronary risk patients, in which changes in physiological indices increased significantly from the beginning to the end of the SWT (Kress et al., 2007). However, the mean increase was not greater than 20%. In our study, only four patients demonstrated 20% increases in HR, systolic BP or diastolic BP. These values decreased after restarting the continuous sedative infusion. No consequences were observed from these physiological changes, and no further treatment was required. Patient safety concerns related to the removal of devices during the SWT have been described previously (Kress et al.,

7 26 M.I. Figueroa-Ramos et al. 2000; Tanios et al., 2009). The 10% incidence of selfextubation for patients in our intervention group was the same as was seen in the Girard study (2008). However, this incidence of self-extubation was higher than was seen in other studies that implemented daily interruption of sedation or algorithm/protocol-directed sedation management, in which studies reported self-extubation rates of 0 1.3% (Bucknall et al., 2008; Elliott et al., 2006; Weisbrodt et al., 2011). O Connor et al. (2009) noted in their review that, although pain can be present during the SWT and may be associated with anxiety, pain has not been explored in previous SWT studies. Our study addressed this gap by assessing pain at the end of each SWT. We found that some patients were able to report the presence or the absence of pain at the end of a given SWT. Moreover, the presence of pain at the end of an SWT was not associated with agitation, i.e., a RASS score of +2. Pain assessment at the end of the SWT provided the opportunity to optimise pain management and improve patient comfort. Several limitations of this study need to be addressed. The sample size was small, and the majority of patients were male. Thus, the results cannot be generalised to all trauma ICU patients. Since we included only patients with RASS scores of 4 and 5, the procedures described here may not apply to TICUs where patients are only lightly sedated. In addition, it is important to mention that at the time of this study, this particular TICU did not use a sedation guideline to manage sedation treatment, in which such a lack could contribute to a high occurrence of over-sedated patients. This study excluded patients with head trauma or who had a history of illicit drug dependence or alcoholism, but who, nevertheless, represent a high percentage of patients admitted to this TICU. Because in more than the half of SWTs, patients were unable to self-report their pain, the behavioural pain scale (Payen et al., 2001) or the critical care pain observation tool (Gelinas and Johnston, 2007) could have been used to measure pain behaviours. The APACHE was scored only at the time of patient admission. Conclusion A sedation wake-up trial plus a spontaneous breathing trial are clinically feasible and appear to be a safe and systematic intervention for these trauma patients. Our results show that this combined intervention was well tolerated and successfully implemented in the small sample. In addition, our data showed that it is not necessary to withhold continuousinfusions analgesic during the SWT, thus preventing rebound pain. Acknowledgements We wish to thank the nursing, respiratory therapists and doctors at the Trauma Hospital for their collaboration in the implementation of the SWT and SBT protocol. 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