|
|
||||||||
Guest Access | Sign In via User Name/Password |
|||||||||
* From the Division of Pulmonary and Critical Care Medicine, Departments of Internal Medicine (Drs. Marelich and Murin), Surgery (Dr. Battistella), Respiratory Care (Mr. Vierra), and Nursing (Mr. Roby), and Center for Health Services Research in Primary Care (Dr. Inciardi), University of California, Davis Medical Center, Sacramento, CA.
Correspondence to: Gregory P. Marelich, MD, FCCP, 6600 Bruceville Rd, Sacramento, CA 95823; e-mail: gregory.p.marelich{at}kp.org
| Abstract |
|---|
|
|
|---|
Design: Prospective, randomized, controlled study.
Setting: University medical center.
Patients: Three hundred eighty-five patients receiving mechanical ventilation between June 1997 and May 1998.
Interventions: A respiratory care practitioner and registered nursedriven VMP.
Results: Intervention and control groups were comparable with respect to age, sex, severity of illness and injury, and duration of respiratory failure at the time of randomization. The duration of mechanical ventilation for patients was decreased from a median of 124 h for the control group to 68 h in the VMP group (p = 0.0001). Thirty-one total instances of VAP were noted. Twelve patients in the surgical control group had VAP, compared with 5 in the surgical VMP group (p = 0.061). The impact of the VMP on VAP frequency was less for medical patients. Mortality and ventilator discontinuation failure rates were similar between control and VMP groups.
Conclusions: A VMP designed for multidisciplinary use was effective in reducing duration of mechanical ventilatory support without any adverse effects on patient outcome. The VMP was also associated with a decrease in incidence of VAP in trauma patients. These results, in conjunction with prior studies, suggest that VMPs are highly effective means of improving care, even in university ICUs.
Key Words: artificial respiration clinical protocols ICU pneumonia time factors ventilator weaning
| Introduction |
|---|
|
|
|---|
A number of studies have demonstrated that standardized approaches to liberation from mechanical ventilatory support can shorten the duration of mechanical ventilatory support.1 2 3 4 5 6 Limitations of previous studies included the use of historical controls2 4 and lack of a single, universally applied protocol.2 3 No trial has documented the effectiveness of a single protocol for use in medical and surgical ICUs in a prospective, randomized, controlled fashion. The potential beneficial effect of a weaning protocol, although significant in some studies,3 5 may be diluted by enrollment of patients at ICU admission, some of whom will have prolonged or terminal respiratory failure.
A potential corollary benefit of reducing duration of mechanical ventilation is a reduction in ventilator-associated complications. The risk of ventilator-associated pneumonia (VAP) appears to be related to duration of mechanical ventilation.7 8 We hypothesized that the incidence rate of VAP would be reduced by an effective ventilator management protocol (VMP).
The purpose of our study was to examine the efficacy of a single VMP in both medical and surgical ICUs. The VMP was created during multidisciplinary planning and required no additional support staff for its implementation, in contrast to other efforts.9 Because the focus of the study was on ventilator discontinuation, patients were randomized only after meeting objective physiologic criteria indicating a readiness to commence weaning. Standard ventilator management practice was compared with the VMP in a randomized, controlled fashion. In addition, we prospectively examined the effect of the VMP on the incidence of clinically defined VAP in our study population.
| Materials and Methods |
|---|
|
|
|---|
Randomization
Eligible patients were identified by twice-daily RCP screening
in the participating ICUs. Entry criteria were the following: (1)
PaO2/fraction of inspired oxygen
(FIO2)
200; (2) static compliance
25 mL/cm H2O; (3) minute volume
15 L/min
(
200 mL/kg/min); and (4) lack of failure of ventilator
discontinuation within the past 24 h. Pregnant patients, patients
< 18 years old, mentally disabled patients, and prisoners were
excluded. A prospective, randomized cohort design was used. Once
qualification for study entry was established, the patients were
randomly assigned to either the physician-directed (MD) or the VMP
group. Randomization was by opaque, sealed, numbered envelopes
stratified for MICU and trauma services and for ICU. The UC Davis Human
Subjects Review Committee approved the study, and the informed consent
requirement was waived.
Study Protocol
Physicians caring for patients randomized to the experimental
(VMP) groups were notified, and a verbal order was requested for study
entry. VMP group patients were then screened for the appropriateness of
an immediate spontaneous breathing trial (SBT). Patients receiving
ventilation > 72 h before study entry did not meet criteria for an
immediate SBT, and the protocol directed the incremental decrease of
each subjects FIO2, positive end-expiratory
pressure (PEEP), intermittent mandatory ventilation rate, and pressure
support (PS) level, as tolerated, in a prioritized fashion.
Patients were then screened for SBTs twice daily. To pass the SBT
screen, patients had to have the following: (1) a Glascow coma score
10 or a tracheostomy, (2) a mean arterial pressure of
60 mm Hg
without vasopressor agents (dopamine was allowed in doses
5 µg/kg
body weight/min), and (3) an adequate cough not limited by pain.
Physician approval for SBTs was not required. A 30-min SBT was used and
was performed on flow-by mode, PS
8 cm H2O
with PEEP
8 cm H2O, or T piece, at the
discretion of the RCP. The SBT was terminated for oxygen saturations
< 92%, respiratory rate > 30 breaths/min, spontaneous tidal
volumes < 5 mL/kg body weight, or respiratory distress. Physicians
were asked at the end of successful SBTs to approve discontinuation of
mechanical ventilation. If an SBT was not tolerated, the patients were
returned to their prior settings and were rescreened every 6 h
between 7:00 AM and 7:00 PM for a repeat SBT,
to a maximum of two SBTs each day.
Incremental reduction of FIO2, PEEP, intermittent mandatory ventilation, and PS was allowed 24 h/d for VMP patients. Patients in the VMP group were not allowed to undergo SBT (and therefore subsequent ventilator discontinuation) between 7:00 PM and 7:00 AM unless they met criteria for an immediate SBT on study entry (Fig 1 ).
|
Definitions
All definitions were selected a priori. APACHE (acute
physiology and chronic health evaluation) II, injury severity, and
Glascow coma scores were calculated in the usual
manner.10
11
VAP was clinically defined as initiation of
antibiotics for clinical suspicion of VAP in association with two of
the following: (1) positive endotracheal tube aspirate or bronchoscopy
cultures; (2) fever or rising peripheral leukocyte count; and (3)
pulmonary opacities consistent with pneumonia without objective
evidence of left atrial hypertension. The objective criteria for
ventilator discontinuation readiness were defined as (1) passage of the
SBT screen, and (2) successful completion of a 30-min SBT performed on
flow-by mode, PS
8 cm H2O on PEEP
8 cm
H2O, or T piece (see above). Successful
discontinuation of mechanical ventilation was defined as continuous
independence from ventilator support for a 24-h period.
Outcomes
The total duration of mechanical ventilation and the incidence
of VAP were defined as primary outcomes a priori. Secondary
outcomes were the duration of mechanical ventilation from study entry
to discontinuation of ventilator support, the duration of mechanical
ventilation from initiation of mechanical support to meeting ventilator
discontinuation criteria (Fig 2
), the ventilator discontinuation failure rate, and death.
|
2 or a Wilcoxon rank sum statistic.
Kaplan-Meier survival curves were generated for each group, and a log
rank statistic was used to test the null hypothesis that group
assignment does not affect the time to meet an end point. Cox
proportional hazards analysis was used to compare time to each end
point after adjustment for covariates, including age, APACHE II, sex,
duration of respiratory failure before study entry, and admission
diagnoses (SAS Statistical Software, Version 7; SAS Institute; Cary,
NC). Using a two-sided test and assuming a type 1 error of 0.05, the
study was expected to have 80% power to detect a 1.5-day difference
between groups with respect to the time to ventilator discontinuation.
We also estimated a similar degree of power to detect a 1.5% absolute
change in incidence rate of VAP. | Results |
|---|
|
|
|---|
|
|
|
|
VAP
The overall rate of VAP in our selected study population was
0.71/1,000 h of mechanical ventilation. Thirty-one total instances of
VAP were noted, 14 from the MICU service and 17 from the trauma service
(Table 2)
. On the trauma service, 12 subjects in the MD group had VAP,
compared with 5 in the VMP-directed group (p = 0.061,
2). The impact of the VMP on VAP frequency was
less for all patients combined (p = 0.100,
2) because of reduced VMP effect on VAP in the
MICU patients. Binary logistic regression suggested a protective effect
of the VMP for VAP on the trauma service (risk ratio, 0.39;
p = 0.119).
To examine the value of our clinical VAP definition for predicting
changes in clinical outcomes, the relationship of VAP to mortality and
ventilator discontinuation failure was examined. One of the MICU
patients with clinically diagnosed VAP died during the study, but no
trauma patients with VAP died (p = 0.84,
2).
Three MICU patients and 5 trauma patients with VAP had ventilator
discontinuation failures, compared with only 23 of 301 patients without
VAP (p = 0.0008,
2). Thus, a clinical
diagnosis of VAP was more common among patients with ventilator
discontinuation failures, although not among those that died.
Secondary Outcomes
The duration of mechanical ventilation from initiation of
mechanical support to meeting ventilator discontinuation criteria was
significantly reduced for the MICU patients and all patients combined
on the VMP (Table 3
). The duration of mechanical ventilation from study entry to
discontinuation of ventilator support was significantly reduced by use
of the VMP for MICU, trauma, and both groups combined.
|
2). The ventilator discontinuation failure
rate was greater for the VMP-directed as compared with the MD MICU
patients (10.8% vs 4.8%, p = 0.185,
2
test), but still within the range of expected ventilator
discontinuation failure rates.3
4
5
12
All-cause mortality for intent-to-treat patients was not different for
patients managed by physicians as compared with those managed by VMP
(p = 0.146,
2). Study subjects were selected
on the basis of adequate pulmonary physiology, thus explaining the
rather low observed mortality rates.
Other Results
The decision to perform tracheotomy or transfer to long-term acute
care facilities was left to the discretion of the managing physicians.
In the MICU group, 19 patients underwent tracheotomy; 13 of these were
physician managed and 6 were VMP managed. In the trauma service group,
15 patients underwent tracheotomy; 8 of these were physician managed
and 7 were VMP managed. Five MICU group patients were discharged to a
long-term acute-care facility. Four of these patients were physician
managed, and only one patient was VMP managed. No trauma service
patients were discharged to a long-term acute-care facility.
| Discussion |
|---|
|
|
|---|
A low probability value was noted for the comparison of all-cause mortality of patients managed by physicians with those managed by VMP (p = 0.146). This might indicate a trend toward increased mortality for the patients randomized to the weaning protocol. More severely ill study patients were excluded by the entry criteria of the protocol, and as a result, our overall mortality was low and the study was not powered to differentiate small changes in mortality from chance occurrence. More importantly, no patients died as a direct result of the weaning protocol, and it would seem unlikely that a weaning protocol comparable to or better than physician management would adversely affect mortality.
The subjects disease process and the duration of respiratory failure before study entry affect the total duration of mechanical ventilation. A VMP will not influence the resolution of the patients respiratory failure. Examining the time frame from protocol entry to ventilator discontinuation allows a focused look at the effect of a weaning protocol. Although our primary study end point was total duration of mechanical ventilation, the duration of mechanical ventilation from study entry to ventilator discontinuation is arguably the most important measure of the effect of the VMP on the weaning process. We found a highly statistically significant improvement in this variable for both medical and surgical patients in the VMP group.
Physician practice impacted on the effectiveness of the VMP. On the trauma service, a standardized MD approach to ventilator management was in place during the study. Control patients were managed with SBTs that were lengthened and/or performed more frequently, as tolerated. However, the decision to extubate the patient was not standardized, but was left to the physicians subjective impression of patient readiness. The duration of mechanical ventilation from study entry to meeting mechanical ventilator discontinuation criteria (the "weaning time") was not significantly affected by the VMP in the trauma population, but the duration of ventilation from meeting ventilation discontinuation criteria to ventilator discontinuation was. In fact, a 70% reduction in duration of mechanical ventilation after VMP patients met ventilator discontinuation criteria was observed. There was no difference in ventilator discontinuation failure rate between trauma VMP and control groups, suggesting that the ventilator discontinuation criteria of the VMP was as specific as the subjective impressions of the trauma physicians. Thus, the use of subjective criteria for determining ventilator discontinuation readiness led to unnecessary prolongation of mechanical ventilation in the MD trauma control group. It is likely that weaning time and total duration of mechanical ventilation were not significantly reduced by the VMP because a standardized, although less formal, weaning protocol was already in place. In contrast, in the MICU, in which there was no structured approach to weaning in place for the control group, the VMP outperformed physicians for each segment of the weaning process.
Published studies suggest that physician acceptance is paramount to the success of a VMP. In one study, physicians used three separate protocols in four ICUs to facilitate acceptance.3 A scheme for identification of patients capable of spontaneous breathing was effective in two MICUs,5 but surgical physician acceptance was only 63% during the first year of the large-scale implementation of the protocol.12 A multidisciplinary, multidepartmental team was used to develop our VMP. The education and leadership provided by physician, RCP, and nursing opinion leaders to their respective counterparts helped ensure the success of implementation of the VMP. A separate analysis of house staff attitudes found that, regardless of department, house staff considered VMPs beneficial to patients, and RNs and RCPs competent to perform weaning. They did not view protocols as detrimental to education or a threat to their autonomy in the ICU.14
Acceptance of our VMP is suggested by the brief duration of mechanical ventilation after patients met ventilator discontinuation criteria. There was little difference between MICU and trauma subjects in this regard, with > 75% of patients identified as meeting extubation criteria liberated from mechanical ventilation within 24 h, and > 90% by day 3.
Previous estimates of ventilator protocol cost-benefit have not included the impact of protocols on ventilator-associated complications. Our study found a difference (p = 0.061) in the incidence of clinically defined VAP between VMP and control trauma patients. The beneficial effect of reducing invasive mechanical ventilatory support on the incidence of VAP has been demonstrated in other studies.15 16 The low numbers of VAP observed in this study reduces the certainty of the conclusion that VAP may be reduced by a weaning protocol. The effect of protocol weaning on VAP should be examined in other clinical trials and venues. The less significant effect of the VMP on VAP in the MICU, despite a more dramatic shortening of time receiving mechanical ventilation, may be explained by the preponderance of respiratory admission diagnoses, which may have confounded our clinical definition of VAP.
Our study had other potential limitations. Although it was prospective, randomized, and controlled, it could not be blinded. It is possible that RNs and RCPs may have been more motivated in their weaning of patients on the VMP. Careful monitoring by a protocol manager failed to detect overt bias. A clinical definition of VAP was used rather than a pathologic or invasive sampling method. Although studies have demonstrated the difficulties in clinically predicting the presence of VAP,17 the impact of invasive airway culture sampling on outcome of VAP remains controversial.18 In terms of antibiotic and resource utilization, a clinical definition is not only adequate but also relevant.
| Conclusion |
|---|
|
|
|---|
| Acknowledgements |
|---|
| Footnotes |
|---|
Financial support provided by the Hibbard E. Williams, MD, Research Fund.
Received for publication June 29, 1999. Accepted for publication February 11, 2000.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
S. M. Koenig and J. D. Truwit Ventilator-Associated Pneumonia: Diagnosis, Treatment, and Prevention Clin. Microbiol. Rev., October 1, 2006; 19(4): 637 - 657. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. E. McLean, L. A. Jensen, D. G. Schroeder, N. R. T. Gibney, and N. M. Skjodt Improving Adherence to a Mechanical Ventilation Weaning Protocol for Critically Ill Adults: Outcomes After an Implementation Program Am. J. Crit. Care., May 1, 2006; 15(3): 299 - 309. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. E.A. Burns, N. K.J. Adhikari, and M. O. Meade A meta-analysis of noninvasive weaning to facilitate liberation from mechanical ventilation: [Une meta-analyse d'un sevrage non effractif pour faciliter le retrait de la ventilation mecanique]. Can J Anesth, March 1, 2006; 53(3): 305 - 315. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. R. MacIntyre Current Issues in Mechanical Ventilation for Respiratory Failure Chest, November 1, 2005; 128(5_suppl_2): 561S - 567S. [Abstract] [Full Text] [PDF] |
||||
![]() |
F. Sebat, D. Johnson, A. A. Musthafa, M. Watnik, S. Moore, K. Henry, and M. Saari A Multidisciplinary Community Hospital Program for Early and Rapid Resuscitation of Shock in Nontrauma Patients Chest, May 1, 2005; 127(5): 1729 - 1743. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. A. Hoffman, F. J. Tasota, T. G. Zullo, C. Scharfenberg, and M. P. Donahoe Outcomes of Care Managed by an Acute Care Nurse Practitioner/Attending Physician Team in a Subacute Medical Intensive Care Unit Am. J. Crit. Care., March 1, 2005; 14(2): 121 - 130. [Abstract] [Full Text] [PDF] |
||||
![]() |
Guidelines for the Management of Adults with Hospital-acquired, Ventilator-associated, and Healthcare-associated Pneumonia Am. J. Respir. Crit. Care Med., February 15, 2005; 171(4): 388 - 416. [Full Text] [PDF] |
||||
![]() |
C. A. Manthous, Y. Amoateng-Adjepong, H. E. Fessler, and J. A. Krishnan Weaning by Protocol Am. J. Respir. Crit. Care Med., July 1, 2004; 170(1): 98 - 100. [Full Text] |
||||
![]() |
J. A. Krishnan, D. Moore, C. Robeson, C. S. Rand, and H. E. Fessler A Prospective, Controlled Trial of a Protocol-based Strategy to Discontinue Mechanical Ventilation Am. J. Respir. Crit. Care Med., March 15, 2004; 169(6): 673 - 678. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. O. Meade and E. W. Ely Protocols to Improve the Care of Critically Ill Pediatric and Adult Patients JAMA, November 27, 2002; 288(20): 2601 - 2603. [Full Text] [PDF] |
||||
![]() |
J Goldstone The pulmonary physician in critical care * 10: Difficult weaning Thorax, November 1, 2002; 57(11): 986 - 991. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. ARABI, S. VENKATESH, S. HADDAD, A. A. SHIMEMERI, and S. A. MALIK A prospective study of prolonged stay in the intensive care unit: predictors and impact on resource utilization Int. J. Qual. Health Care, October 1, 2002; 14(5): 403 - 410. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. R. MacIntyre Evidence-Based Guidelines for Weaning and Discontinuing Ventilatory Support : A Collective Task Force Facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine Chest, December 1, 2001; 120(6_suppl): 375S - 396S. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. W. Ely, M. O. Meade, E. F. Haponik, M. H. Kollef, D. J. Cook, G. H. Guyatt, and J. K. Stoller Mechanical Ventilator Weaning Protocols Driven by Nonphysician Health-Care Professionals : Evidence-Based Clinical Practice Guidelines Chest, December 1, 2001; 120(6_suppl): 454S - 463S. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |