Protocols
and Beyond.
Weaning
the patient from mechanical ventilation can be frustrating
and potentially dangerous. There is often confusion
about whether the patient is ready to wean and what
is the best method to use in the weaning process. Some
of the confusion may result from labeling weaning as
an event rather than a process. A more useful paradigm
is to consider weaning as titration from mechanical
ventilation.
Most
nurses would not even consider abruptly removing a vasopressor
or nitrate infusion from a patient. Yet, many times
mechanical ventilation is abruptly withdrawn during
weaning. Abruptly withdrawing positive pressure ventilation
can cause respiratory distress and hemodynamic instability.
Paradigm
change in weaning from mechanical ventilation
To
be effective, titration from mechanical ventilation
must be:
-
well-planned
- patient
specific
- implemented
with a team approach
- and
have specific and measurable goals
Assess
the patient's readiness to wean:
There
are five major reasons why patients have difficulty with
the titration process. These are:
- The
primary respiratory problem remains unresolved
- The
patient has excessive secretions
- Nutrition
has not been maintained
- Electrolytes
are abnormal
- The
patient has auto-PEEP
Before
titration of mechanical ventilation can begin, these major
problems must be resolved. If these issues are addressed
when ventilation is begun, the patient will be able to
begin the titration process sooner. Titration should begin
as soon as the patient is hemodynamically stable. Weaning
protocols have been helpful by weaning FiO2 and PEEP early
in the course of ventilation. However, most weaning protocols
don't allow enough flexibility to make them patient specific.
If weaning is to be effective, it must be planned and
implemented with collaboration between physician, nurse,
and respiratory therapy.
Plan
method to use:
Before
titration is begun, the method for weaning should be considered.
Titration should be patient specific, taking into consideration
the patient's primary illness, length of ventilatory support,
and other confounding medical conditions. Four major modes
of titration are commonly used:
- SIMV
- T-piece
- CPAP
/ BiPAP
- Pressure
Support
Synchronized
intermittent mandatory ventilation (SIMV) is most useful
in patients whom a rapid change in intrathoracic pressure
would cause hemodynamic instability. Patients with cardiovascular
disease can suffer from congestive failure due to increased
venous return that occurs with rapid changes in thoracic
pressure. SIMV allows for gradual change from positive
pressure ventilation to spontaneous (negative) pressure
ventilation.
T-piece
trials are usually used with resting periods of assist
control (AC) ventilation. The advantage to this approach
is that while weaning the patient is doing all the work
of breathing, and while on AC the patient is allowed to
rest. AC with T-piece trials may work best in the patient
with COPD or other chronic lung conditions that cause
respiratory muscle weakness.
Continuous
positive airway pressure (CPAP) and bi-level positive
airway pressure (BiPAP) are effective in providing expiratory
support to maintain oxygenation and prevent alveolar collapse
during titration. They also maintain a level of positive
intrathoracic pressure that may be helpful in the cardiovascular
patient. BiPAP adds inspiratory support to CPAP, which
may be helpful in preventing respiratory muscle fatigue.
Pressure
support (PS) provides inspiratory support to help overcome
airway resistance and decrease respiratory muscle fatigue.
PS may be helpful in retraining respiratory muscles in
a patient who has been on long-term ventilation.
Research
does not support the use of any one of these methods for
all patients. The choice should be patient specific based
on the patient's primary pathology, previous cardiovascular
and respiratory disease, and tolerance of the method chosen.
Pack
& go:
Before
titration can begin, the patient should be "packed
up" by weaning to minimal support. Optimally, the
patient would be on <40% FiO2, <8 cmH2O PEEP,
and should be taking spontaneous breaths. At this time,
the patient's hemodynamics must be evaluated carefully,
and diuresis may be helpful to prevent cardiac congestion
with intrathoracic pressure changes.
Usually
sedation is discontinued when weaning is begun. This
often results in a wide-awake, frightened patient who
is "bucking" the ventilator and pulling on
the tube. Most patients say that mechanical ventilation
is extremely uncomfortable, and moderately painful.
Therefore, it would make sense to manage the patient's
pain and discomfort for the best outcome. A well-planned
strategy would include sedation, pain control, and anxiety
control in modest amounts to keep the patient comfortable
but conscious during weaning. Use of a sedation protocol
may be helpful in providing a standardized approach.
Gas-up
Once
the previous planning has been done, the patient should
be physically and psychologically prepared for weaning.
Check the patient's nutritional status with the help
of a dietitian. Assure adequate rest the night before
weaning. Keep in mind that the average ICU patient sleeps
about two hours a day. Your patient may need sedation
overnight with a short-acting medication such as Propofol®.
Shortly
before weaning, suction the patient and allow several
minutes for his oxygenation to return to normal. Using
100% FiO2 during suctioning helps to accomplish this.
Go
Start
the weaning trial at the appropriate time of day. Mornings
can be difficult for several reasons:
- Preload
may be higher in the morning
- Respiratory
function is worse in the morning (circadian effects)
- Interruptions
are more frequent (rounds, shift change, etc.)
Therefore,
if weaning is to begin early in the day, be aware of these
variables and try to minimize their effects on the patient
by: 1) assessing hemodynamics and the need for diuresis,
2) recognizing that some patients may have better respiratory
function in the afternoon, and 3) limiting interruptions,
examinations, and procedures during weaning.
When
to stop
Determination
of assessment parameters for continued weaning (Go),
cautious weaning (Caution), weaning discontinuation
(Stop) should be made before the trial is begun. These
parameters should be patient specific and should consider:
hemodynamics, underlying cardiac and respiratory disease,
respiratory muscle strength, and energy reserves. Some
general guidelines are below:
Go:
-
No
respiratory distress
-
Hemodynamically
stable
-
Respiratory
distress, respiratory acidosis
-
Vital
sign changes: increased RR, HR, B/P
The
diagram below depicts the weaning process from start to
finish:
Summary
Weaning
from mechanical ventilation is best achieved when it
is viewed as a process of titration, and is implemented
in a collaborative manner with input from the physician,
nurse, and respiratory therapist. When the patient is
properly prepared, the plan is well-communicated, and
goal-directed, then the length of ventilatory support
is decreased, ICU stay is shortened, and mortality is
improved.
The
conceptual model described above may help to integrate
many components of the complicated weaning process.
Caregiver-directed protocols shorten ventilator duration,
and improve patient outcomes (see
example of a weaning protocol). But it is important
that weaning not be directed from protocols or standard
methods alone, but should instead be patient-specific,
and flexible enough to allow for changes based on the
patient's response to titration.
References:
Ely,
E.W., Bennett, P.A., Bowton, D.L., et al. (1999). Large
scale implementation of a respiratory therapist-driven
protocol for ventilator weaning. American Journal
of Respiratory and Critical Care Medicine, 159: 439-446.
Estaban
A, Frutos F, Tobin MJ, et al. (1995). A comparison of
four methods of weaning patients from mechanical ventilation.
New England Journal or Medicine, 332-345.
Grap,
M.J., Strickland, D., Tormey, L. et al. (2003). Collaborative
practice: Development, implementation, and evaluation
of a weaning protocol for patients receiving mechanical
ventilation. American Journal of Critical Care,
12(5): 454-460.
Henneman,
E., Dracup, K., Ganz, T., et al. (2001). The effects
of a collaborative weaning plan on patient outcome in
the critical care setting. Critical Care Medicine,
1, 297-303.
Henneman,
E., Dracup, K., et al. (2002). Using a collaborative
weaning plan to decrease duration of mechanical ventilation
and length of stay in the intensive care unit for patients
receiving long-term ventilation. American Journal
of Critical Care, 11 (2), 132-140.
Kilger
E, Briegel J, Haller M, et al. (1999). Effects of noninvasive
positive pressure ventilatory support in non-COPD patients
with acute respiratory insufficiency after early extubation.
Intensive Care Medicine, 25:1374-1380.
Kollef,
M.H., Shapiro, SD., Silver, P., et al. (1997). A randomized,
controlled trial of protocol-directed versus physician-directed
weaning from mechanical ventilation. Critical Care
Medicine, 25, 567-574.
Marelich,
G.P., Murin, S., Battistella, F., et al. (2000). Protocol
weaning of mechanical ventilation medical and surgical
patients by respiratory care practitioners and nurses:
Effects on weaning time and incidence of ventilator-associated
pneumonia. Chest, 118: 459-467.
Saura,
P., Blanch, L., Mestre, J. et al. (1996). Clinical consequences
of the implementation of a weaning protocol. Intensive
Care Medicine, 22: 1052-1056.
Stoller,
J.K., Mascha, E.J., Kester, L., et al. (1998). Randomized,
controlled trial of physician-directed versus respiratory
therapy consult service-directed respiratory care to
adult non-ICU inpatients. American Journal of Respiratory
and Critical Care Medicine, 158: 1068-1075.
Wood,
G. MacLeod, B., Moffatt, S. (1995). Weaning from mechanical
ventilation: Physician-directed versus a respiratory
therapist-directed protocol. Respiratory Care, 40:
219-224.
Woodruff,
D.W. (1999). Managing complications of mechanical ventilation.
Nursing 99, 29, 11, 34-40.
Are
you interested in implementing a collaborative weaning
strategy in your institution?
E-mail us for more information.
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