Info

*AHCPR pooled results for weaning parameters [2].

*AHCPR pooled results for weaning parameters [2].

respiratory therapists to obtain weaning parameters, Hoo et al. [16] distributed a questionnaire to local registered respiratory therapists. Among 102 registered respiratory therapists serving nine different hospitals, wide variations regarding both weaning parameter definitions and how to obtain them were revealed. Specifically, there was no consensus on the mode of ventilation used during the process, the time before recording the parameters, or even how to record a parameter such as respiratory rate (e.g., ventilator display vs watching the patient). Furthermore, there was wide variation between registered respiratory therapists at the same institution.

What were the Pivotal Investigations that led to Modern Day Weaning Protocols?

In an early investigation of weaning parameters [17], it was noted that this clinical decision is often arbitrary, "based on judgment and experience". Despite numerous efforts to determine the best method of weaning patients from mechanical ventilation, it was not until 1994 that any RCT showed one method (pressure support ventilation, or PSV) to be superior to others [18]. The following year, however, another well performed RCT showed seemingly conflicting results, with SBTs leading to earlier extubation among mechanically ventilated patients [19]. Although these investigations reached contradictory conclusions, these trials showed that:

1. weaning strategies influence the duration of mechanical ventilation

2. the specific criteria used to initiate changes in ventilatory support influence outcome

3. the most ineffective approach was intermittent mandatory ventilation (IMV), a previously widely-used strategy.

Fig.1. Kaplan Meier curve showing effect of therapist and nurse-driven protocol on duration of mechanical ventilation as compared to non-protocolized approach using attending physicians as key decision makers. Despite higher severity of illness in the intervention group, those patients were off of mechanical ventilation an average of 2 days earlier as compared to the control group. From [20] with permission

Fig.1. Kaplan Meier curve showing effect of therapist and nurse-driven protocol on duration of mechanical ventilation as compared to non-protocolized approach using attending physicians as key decision makers. Despite higher severity of illness in the intervention group, those patients were off of mechanical ventilation an average of 2 days earlier as compared to the control group. From [20] with permission

In the first prospective study to incorporate a 'control', non-protocolized arm versus a registered respiratory therapist driven protocol we enrolled 300 mechanically ventilated medical and nonsurgical cardiac patients into a RCT in which the treatment group was weaned using a two-step process of screening by registered respiratory therapists followed by daily SBTs for patients who 'passed' the screen [20]. The outcomes of the investigation included removal from mechanical ventilation two days earlier in the protocol-directed group despite a higher severity of illness (Fig. 1), 50% fewer complications, and a reduction in the cost of ICU stay by $5,000 per patient. Subsequent implementation of this protocol in 530 patients at another large medical center was associated with a similar reintubation rate (6%) and no increased risk of mortality [21].

Simultaneous to our study, Kollef and colleagues [22] were conducting another RCT (n=357) of protocol-directed versus physician-directed weaning in four ICUs (two medical and two surgical). This investigation incorporated three separate weaning protocols because of difficulty in achieving consensus among different units, underscoring the practical challenges facing implementation of protocols. The protocol-directed group incorporated an amalgam of SBTs, PSV, and synchronized IMV (SIMV) protocols, and demonstrated an earlier initiation of weaning efforts and a median duration of mechanical ventilation of 35 hours versus 44 hours in the physician-directed group.

Two other RCTs have compared protocol-based weans to conventional weans. One very small trial (15 patients) compared a computer-directed wean to a physician-directed wean and found trends in favor of the computer-directed wean in both non-extubation and reintubation rates [23]. In a more recent investigation that included 335 patients (~50% surgical, predominantly trauma), Marelich and colleagues [24] showed that the use of a weaning protocol incorporating multiple daily SBT assessments shortened the median duration of mechanical ventilation from 124 hours to 68 hours (p=0.001).

The numerous non-randomized controlled clinical trials ofweaning [25-33] are generally consistent with the results of the RCTs, demonstrating statistically significant reductions or trends toward reductions in the duration of mechanical ventilation and ICU length of stay. Mortality and reintubation rates do not appear to differ between experimental and control groups. Protocol-based weans are associated with other favorable outcomes such as fewer arterial blood gases and significant cost savings.

Personnel expenses are thought to account for more than 50% of the cost of mechanical ventilation [34], and some investigators have advocated the use of a weaning team [35]. In our study, the total cost of ICU care throughout the study period for the control group was $4,297,024 and for the intervention group was $3,855,001, representing a savings of $442,023. Kollefet al. [22] reported savings of $42,960 in their protocol-directed weaning group. Similarly, Smyrnios et al. [36] reported dramatic savings of $3,440,787 during the course of their recently published prospective, before-and-after intervention trial using their own version of an SBT focused weaning protocol. These savings were the result of only 2 years of protocolized weaning for 518 adult ICU patients. The details of this investigation will be discussed in the protocol section.

What is a 'Spontaneous Breathing Trial' and how is one Performed?

Allowing a patient to breathe spontaneously with minimal or no ventilatory support for a predetermined time during close monitoring is an optimal process to confirm a patient's readiness for extubation. This method of liberation is generally accepted as standard of care for clinicians and researchers alike [2]. We recommend performing a SBT on a daily basis, preferably during the morning hours. Further trials throughout the day may be tolerated, but generally do not reduce ventilator time [19], and always make use of precious ICU resources. The specific definition of an SBT and how to perform one is detailed in Table 5.

Esteban and the Spanish Lung Failure Collaborative Group have defined practical aspects of the SBT. These investigators showed in a RCT of 526 patients that successful extubation was achieved equally effectively with SBTs lasting 30 minutes or 120 minutes [37]. Perren and colleagues [38] recently published a similar RCT involving 98 patients, all of whom were considered ready to wean after 48 hours of mechanical ventilation in 2 medical-surgical adult ICUs. The extubation success rate of a SBT using 7 cmH2O pressure support and lasting only 30 minutes was 93%, with only four (9%) patients requiring reintubation. Comparatively, the success rate of an SBT lasting 2 hours was 88%, with only two (4%) patients requiring re-intubation.

Esteban's group had previously documented that the SBT could be conducted with either a low level of PSV or a T-piece [39]. In our studies, SBTs were performed with either standard T-tube circuits or flow-triggered openings of the demand valve

Table 5. How to conduct a spontaneous breathing trial (SBT)

• A trial of spontaneous breathing for a predetermined amount of time (i.e., 30 to 120 minutes) with ventilator rate set to 0 and pressure support of 0 to 7 (we prefer 0)

• Practical criteria for safety:

- Absence of agitation (NOT dangerous to self or others) Oxygen saturation 88%

- No evidence of active myocardial ischemia

- No significant use of vasopressors or inotropes (patients may be on dopamine or dobu-tamine at <5 ^g/kg/min or norepinephrine <2 ^g/min, but may not be receiving any va-sopressin or milrinone)

- Patient exhibiting spontaneous inspiratory efforts.

- No evidence of increased intracranial pressure

Who performs the SBT?

• Registered respiratory therapists and/or registered nurses screen patients for the safety criteria above and initiate or prompt a physician to order an SBT

• Registered respiratory therapists and/or registered nurses initiate the SBT and monitor the patient during the trial, re-initiating mechanical ventilation if criteria for trial termination are met

When is an SBT terminated?

• If the patient successfully tolerates the SBT for 30 minutes to two hours

• When one of the following conditions is met:

- Any abrupt changes in mental status including but not limited to sustained anxiety, delirium, somnolence, and coma

- Total RR >35 or < 8(5 min at respiratory rate > 35 or <8 may be tolerated).

- SpO2 < 88% (< 15 min at < 88% may be tolerated).

- Respiratory distress (two or more of the following):

- HR > or < 120% of the 0600 rate AND either <60 bpm or >130 bpm.

- Marked use of accessory muscles.

- Abdominal paradox.

- Diaphoresis.

- Marked subjective dyspnea.

What does it mean if a patient passes an SBT?

• Successful completion of a 2 hour SBT indicates an 85 to 90% chance of successfully staying off the mechanical ventilation for 48 hours [21].

RR = respiratory rate; HR = heart rate; FiO2 = fraction of inspired oxygen; SpO2 =oxygen saturation as obtained via a pulse oximeter or an arterial blood gas.

without additional support. Incorporating flow-triggering during the SBT was a convenience that minimized respiratory therapist involvement, and had not been investigated by others. Taken together, these investigations support institutional variations in the specific method of conducting an SBT. In fact, individual physicians may wish to tailor the technique and duration of SBTs for individual patients.

Almost 10 years have passed since publication of the first evidence supporting the process of rapidly removing ventilatory support (e.g., SBTs or PSV tapered quickly) as a means ofweaning [18-20]. However, in a recent international utilization review of the actual weaning practices of 412 medical and surgical ICUs in1,638 patients receiving mechanical ventilation, only 20% of patients were weaned using some form of SBT, and in the United States SBTs were incorporated into weaning in less than 10% of all patients studied [40]. Such a disconnect between daily practice and evidence based medicine is a reality that strongly supports the implementation of widespread protocol-guided weaning algorithms.

Which Data Support 'Real-Life' Implementation of Weaning Protocols?

Smyrnios et al. recently published an interesting prospective before-and-after intervention study [36] examining the effects of a hospital-wide weaning protocol. These investigators recorded data on all adult ICU patients who met criteria for DRG 475 "respiratory system diagnosis with mechanical ventilation", and DRG 483 "tracheotomy except for mouth, laryngeal, or pharyngeal disorder" during a baseline, non-intervention year. They subsequently initiated a multifaceted, multidis-ciplinary weaning management protocol involving physicians, nurses, and registered respiratory therapists, and included a mandatory pulmonary consult if the primary physician felt that weaning was possible for 3 days, and yet unsuccessful. The once-daily SBT was chosen as the weaning mode of choice, using continuous positive airway pressure (CPAP) at 5 cmH2O during the trial. This protocol was left in place for 2 years, with frequent monitoring for compliance and continuing educational sessions. The mean APACHE II score actually increased from the pre-intervention, baseline year as compared to the second year of the trial (p < 0.0005). However, the endpoints were all significantly reduced (all p < 0.0005) in the post intervention protocol group compared to the pre-protocol group and included mean time on the ventilator (17.5 vs 23.9 days), mean hospital length of stay (24.7 vs 37.5 days), mean ICU length of stay (20.3 vs 30.5 days), and percentage of patients requiring tracheotomy (41 vs 61%). A total cost savings of $3,440,787 was estimated, as total cost per case decreased from $92,933 to $63,687 (p < .0005).

Vitacca et al. published data in regard to patients with chronic respiratory failure [41], which was listed in Krieger's 2002 top ten list in mechanical ventilation [3]. Invasively ventilated COPD patients who remained on the ventilator after 15 days were randomized to either daily SBTs or decreasing levels ofpressure support. Both methods were equivocal, and yet both were better than a historical control model of "uncontrolled clinical practice". Again, the influence of protocolized weaning was shown to be superior.

Iregui et al. [42] recently studied the efficacy of a weaning protocol powered by a handheld computer program. This investigation was also designed as a before-and-after prospective study with consecutive control and intervention groups, including allpatients in a medical ICU who required invasive ventilation in a single, academic institution. The specific registered respiratory therapist-driven protocol for all patients was identical to that used by Kollef et al. during their 1997 study, hence all patients (n = 176 control/176 intervention) should have undergone SBTs in exactly the same manner. However, patients during the intervention period had a significantly greater likelihood of undergoing an SBT when they first met the protocol criteria, presumably because the handheld computer 'reminded' the registered respiratory therapist to move ahead with the SBT. The registered respiratory therapists were more confident and effective in their bedside management of patients, which allowed for better protocol compliance. This automated methodology, reliant on a small, handheld computer, improved weaning efficiency in a safe manner, and resulted in a reduced length of stay in the ICU, and less ventilator associated pneumonia (VAP).

Written from the perspective of a respiratory therapist, Croft recently published a concise review of protocol recommendations [43] and stated that even the best-planned protocols are only as effective as the registered respiratory therapists (or equivalent non-physician health care provider if outside of the United States) implementing them.

Collectively, these data would suggest that it is the protocol approach to weaning (and the culture change which these protocols represent) that produces benefit in the medical ICU population, rather than any specific modality of weaning. Current data do not support a specific protocol, and the selection of an appropriate protocol is best left to multidisciplinar^ teams at individual institutions. Importantly, each institution must endorse the fiscal commitment and the staffing modifications necessary for developing and implementing a multidisciplinar^ weaning protocol team of dedicated health care practitioners. For a list of the seven specific AHCPR recommendations regarding the implementation of weaning protocols, see Table6.

What Advice can Increase the Success of Implementation?

Specific tips for the implementation of weaning protocols and for avoiding barriers to success, derived from the study of over 15,000 patient days and nearly 2 years of implementation, are presented in Table 7 [44]. Importantly, protocols perse should not be viewed as rigid rules, but rather as dynamic tools in evolution, which can be improved upon to address local problems and to accommodate new data. It is imperative that protocols be used not to replace clinical judgment, but rather to complement it.

In our experience, both clinically and from a research perspective, there are 2 important tenants regarding implementation of a weaning algorithm: 1) one must work hard at the outset to attain general consensus about the algorithm among the health care professionals (registered respiratory therapists, nurses, and physicians); and 2) the team must grant reasonable autonomy to the registered respiratory therapists and nurses who willbe instrumental in moving patients through the protocol.

To implement a novel protocol, whether in an academic or community based institution, we suggest following the pattern of change known as the "breakthrough method". The concept of this approach is simple; you must first set goals, then implement small changes, measure or quantify the outcome of the changes, and subsequently improve upon the original protocol. Essentially, you must 'plan-do-

Table 6. Seven AHCPR recommendations regarding weaning protocols

1. Non-physician health care professionals should be included in the development and utilization of respiratory care protocols (not confined to liberation from mechanical ventilation).

2. ICU clinicians should utilize protocols for liberating patients from mechanical ventilation in order to safely reduce the duration of mechanical ventilation.

3. At least once daily spontaneous breathing trials should be used to identify patients who are ready for liberation from the ventilator.

4. When patients fail a trial of spontaneous breathing, the following assessments and interventions should be made, based on varying levels of evidence:

- That all remediable factors be addressed to enhance the prospects of successful liberation from mechanical ventilation (e.g., electrolyte derangements, bronchospasm, malnutrition, patient positioning, excess secretions, etc.).

- That the patient be placed in an upright position on a comfortable, safe, and well-monitored mode of mechanical vcentilation (such as pressure support ventilation).

- That a spontaneous breathing test (SBT) be performed at least once daily. Few data support multiple manipulations of ventilator settings each day in an effort to wean or 'train' the patient. For clinicians who prefer step-wise reductions in mechanical ventilation, both multiple daily SBTs and weaning pressure support ventilation appear superior to intermittent mandatory ventilation.

- In the face of repeated failures at daily trials of spontaneous breathing, clinicians should consider longer-term options, including both tracheotomy and a long-term acute-care or step-down ventilator facility.

5. When patients have passed a spontaneous breathing trial, clinicians should seriously consider prompt extubation.

6. Consideration should be made of protocols that include daily cessation and targeted sedation goals to reduce the duration of mechanical ventilation and ICU stay.

7. Consideration should be made of the following strategies for weaning protocols: development using an evidence-based approach by a multidisciplinary team, and implementation using effective behavior changing strategies such as interactive education, opinion leaders, reminders, audit and feedback.

study-act', as described in detail recently by Brattebo et al. [45]. The initial version of a protocol will have some flaws that mostly relate to the uniqueness of an individual institution. These initial obstacles should not be regarded as failures of the methodology, but rather as opportunities for improvement.

Protocolized care has been advocated in many facets ofmedicine, but relinquishing control of the patient's management often creates resentment and frustration on the part of physicians. Negative reactions to protocols maybe reasonable under some circumstances, since protocols have the potential to do harm. Important considerations that may facilitate behavioral changes include interactive education, timely and specific feedback, participation by physicians in the effort to change, administrative interventions, and even financial incentives [46. Effective implementation also requires adequate staffing. If staffing is reduced below certain thresholds, clinical outcomes maybe jeopardized [47, 48]. In the specific context of liberation from mechanical ventilation, reductions in nurse to patient ratios have been associated with prolonged duration of mechanical ventilation [49].

Table 7. How to maximize the likelihood of success in achieving both a change of behavior and long-term protocol implementation

1. Identify the patient-care issue as a high priority item (e.g., ventilator weaning and timely extubation)

2. Obtain base-line data (e.g., lengths of stay and complication rates)

3. Base the program on medical evidence, but also reviews of other programs and attain local expert opinion

4. Acknowledge the need for a 'change in culture' on the part of both physicians and non-physician healthcare professionals

5. Work hard to attain 'buy-in' and participation of key opinion leaders/physicians

6. Establish a team including the hospital administration, respiratory care practitioners, nurses/nurse practitioners, potentially ethicists, and physicians

7. As a team, establish goals and set objective definitions of success and failure.

8. Structure a graded, staged implementation process which provides all of the following:

- Education

- Timely feedback

- Compliance monitoring (particularly important and yet most often overlooked)

- Tracking of appropriate outcomes (including cost) via daily data collection

- Avoid complicated plans aimed at perfection; rather remain practical and useful

- Consider the entire process to be dynamic not fixed; incorporate innovative changes over time to respond to lessons learned

9. Avoid changing personnel too often

10. Avoid overly rigid interpretation of the 'rules' of the protocol

11. Do not remove clinical judgment on part of any team members

12. Acknowledge the need for and plan to have periodic refresher implementation processes to avoid the otherwise inevitable 'regression to baseline'.

* These specific tips for the implementation of weaning protocols and for avoiding common barriers to success were derived from the study of over 15,000 patient days and nearly 2 years of implementation [45].

It is clear that guidelines, statements, and protocols have increasingly been considered as part of the standard of care, both by physicians and courts alike. Accordingly, there are some legal implications of clinical practice guidelines, which were recently addressed by Damen et al. [50] with regard to European court standards. The authors are clear that physician autonomy should remain the gold standard for care, and court decisions must bebasedupon sound clinical judgment. In other words, strict compliance to a protocol does not exclude liability, precisely because protocols and guidelines are designed for a population, rather than an individual patient.

Is there a Relationship Between Weaning Success and Sedation Practices?

Clinical practice guidelines with regard to standardizing sedation protocols within the ICU have recently been published as a collaborative effort among the American College of Critical Care Medicine, the Society of Critical Care Medicine (SCCM), the American Society of Health-System Pharmacists, and the ACCP [51]. Only two of the current 28 recommendations are supported by grade-A evidence. One of the grade-A suggestions reads as follows: "The titration of the sedative dose to a defined endpoint is recommended with systematic tapering of the dose or daily interruption with re-titration to minimize prolonged sedative effects."

Specific support for this statement can be found in the landmark article published by Kress et al. [52]. This study of 150 mechanically ventilated patients implemented a protocol in which the treatment group had sedatives discontinued daily, while the control group's sedation was titrated according to the attending physician's preferences. In the treatment group the duration of mechanical ventilation was reduced by 2 days (p=0.004) and the ICU length of stay was reduced by 3.5 days (p=0.02). Overall complications and length of hospital stay were similar in both groups, and the approach to daily cessation of sedatives appeared safe in this medical ICU population. Kollef et al. [53] showed that delivery of sedation via intermittent bolus was associated with shorter duration of mechanical ventilation than delivery via continuous infusion.

Randolph et al. recently published a RCT comparing a weaning protocol to 'standard care' in 182 critically ill children [54]. The study was stopped early due to an apparent lack of difference between the two groups. After data analysis, however, it was shown that increased sedative use during the first 24 hours of weaning was an important predictor of weaning duration [55]. Whether a sedation protocol could better influence the outcomes of critically ill children in terms of weaning is not known.

The goals of sedation for mechanically ventilated patients usually include the following: 1) alleviation of agitation to a safe, tolerable level of movement by the patient and 2) alleviation of distress (pain, anxiety, dyspnea, and delirium). The pharmacoeconomic impact of clinical practice guidelines for analgesia, sedation, and neuromuscular blockade appear favorable [56]. Following the above-mentioned study by Kollef et al. [53], the same group completed a RCT that incorporated a nursing-implemented protocol to manage the delivery of sedation. They showed a reduction in the duration of mechanical ventilation by 2 days (p=0.008), length of stay in the ICU by 2 days (p<0.0001), and a significantly lower tracheostomy rate among the treatment group (6 vs 13%, p=0.04) [57]. Importantly, the authors report an estimated savings of $349,920 for the 162 patients in the intervention group. Together with the study by Kress et al. [52], these data support that shorter durations of mechanical ventilation and reductions in complication rates can be accomplished by reducing the use of sedative drips and by stopping sedation entirely on a regularly scheduled basis.

Considering the important role that sedatives and analgesics play in causing at least temporary cognitive impairment, we would like to focus the reader's attention on an emerging body of literature that suggests that delirium (or acute brain dysfunction) is independently associated with adverse outcomes in mechanically ventilated patients. Delirium in the ICU, which is a measure of the 'content' of consciousness rather than simply the patient's level of arousal in the ICU, was associated with higher mortality at 6 months and was also found to persist in at least 10% of patients at hospital discharge [58, 59].

We recently undertook a prospective investigation of 275 ventilated patients to determine the relationship between delirium, ventilator free days, and extubation failure [60]. The presence of delirium was identified by the Confusion Assessment Method forthe Intensive Care Unit (CAM-ICU) [58,59], while ventilator-free days were defined as the number of days from initiation of unassisted breathing to day 28 after randomization. After excluding 51 patients who had persistent coma and death in the ICU, the development of at least one episode of delirium (n=183) (median 19 days, interquartile range 5 to 24) during mechanical ventilation was associated with fewer ventilator-free days versus patients without delirium (n=41, 24 days, 21 to 26, p<0.0001). There were trends toward extubation failure among the patients who were delirious within 48 hours following extubation versus those who were not (16 vs 8%, p=0.07).

We have conducted an international survey of 915 ICU health care professionals regarding their opinions about delirum in this setting [61]. The results of this survey suggest that most healthcare professionals consider delirium in the ICU a common and serious problem, most admit it is under-diagnosed, yet few actually monitor adequately for this condition. Data from this survey point to a disconnect between the perceived significance of delirium in the ICU and current practices of monitoring and treatment. However, only through future investigations concerning the prevention of and therapy for delirium will we fully understand the impact of this form of acute brain dysfunction on outcomes of mechanical ventilation.

Conclusion

This chapter has reviewed many of the most important aspects regarding liberating patients from mechanical ventilation, while emphasizing points of uncertainty and those ripe for future research. We have emphasized a simplified approach that focuses on two points: recognizing when patients are able to breath spontaneously, and modifying practice to optimize the use of sedation (e.g., avoiding overseda-tion). The evidence from multiple randomized trials supports a Grade A, Level I recommendation to implement a standardized/protocolized approach to liberation driven by a team of non-physician health care providers operating in concert with the physician. This protocol should strive to incorporate daily spontaneous breathing trials as the lynchpin ofweaning in patients who are clinically improving, rather than placing undue emphasis on specific cut-offs for individual weaning parameters. Each institution must actively adopt an approach that best serves its community. This approach should be evidence-based yet must be adapted so that it will be championed by the local opinion leaders who can continually work to implement, update, and document compliance with their protocol.

Perhaps the simplest statement regarding the 'bottom line' on weaningprotocols can be stated as previously published in the AHCPR guidelines [2]: "Acknowledging the important nuances in protocols that should be dictated by specific patient populations and institutional preferences, the following two steps in any successful weaning attempt derived from recent RCTs bear repeating: step A should involve minimizing or temporarily discontinuing sedation and analgesia enough to observe patient AWAKENING; and step B should involve an assessment of the patient's ability to spontaneously BREATHE."

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