Download Blood Oxygenation Monitoring During Impella® Support

Impella Updates
®
September, 2015
Blood Oxygenation Monitoring
During Impella® Support
WHAT’S NEW?
When using pulse oximetry in patients supported by
the Impella® Catheter, clinicians may observe issues
during nonpulsatile flow conditions. This Impella®
Update will help clarify what to expect from commonly
available oxygen saturation monitors during situations
in which arterial blood pressure may become nonpulsatile due to Impella® support in the face of significant
cardiac depression. This Impella® Update also discusses measures to mitigate this issue.
BACKGROUND
Patients can have dramatic hemodynamic variability while
undergoing cardiac catheterization lab interventions. During
such procedures, multiple monitoring modalities, including
pulse oximetry, are routinely and appropriately utilized.
During Impella® use, especially when the device is first
started, the patient’s pulsatility may drop or disappear completely. This is due to the functional nature of the continuous
flow ventricular support systems and may vary depending
on the level of myocardial compromise. During periods of
severe myocardial depression, the Impella® becomes the
dominant contributor to systemic blood flow. With the use
of a continuous flow ventricular support systems, blood flow
inherently loses its pulsatile nature until the native heart is
strong enough to return to pulsatile flow.
HCS-TB00992 rB
PUTTING IT INTO PRACTICE
Effect of Impella® on Common Oximetry
Monitoring.
Since a patient may experience a drop in pulsatility as the
device provides higher levels of support, it is important
to recognize the effect of Impella® on common oximetry
monitoring systems. Specifically, pulse oximetry is entirely
dependent upon a peripheral pulse in order to determine
the oxygen levels of the patient (Figure 1). A decrease
in pulsatility may cause a drastic drop or a “zero” value
calculated for SpO2. This displayed or calculated value can
occur regardless of the true arterial oxygen saturation and
may lead to confusion as to the true clinical state of the
patient’s arterial oxygenation saturation.
Alarms are set in place within the monitoring device to notify the operator when the readings drop below a specific
limit (%SpO2 below 85% in most popular devices) or when
pulse pressure is low.
The root cause of the pulse oximetry false readings is low
to no pulsatility which is outside of the intended operating conditions for this monitoring method. Instead, some
centers use cerebral oximetry for assessing hemodynamic
conditions when more invasive monitoring is not available3.
Support the Patient and Evaluate Reasons for
Alarm.
The first priority is always to support the patient and
evaluate potential reasons for an oximetry alarm condition.
When Impella® support is initiated, one should always
Impella Updates
®
note the degree of pulsatility. Pulse has been seen to
“mean out” with high levels of Impella® support; however,
the mean blood pressure should be adequate and in the
60–75 mmHg range. Myocardial depression and/or severe
hypovolemia will exacerbate this phenomenon. With this
knowledge, one should be prepared and aware that the
Impella® alarm of “Impella® Position Unknown” will be
displayed if the arterial pulse pressure is <20 mmHg at
which point pulse oximetry monitors may simultaneously
indicate falling or potentially unknown oxygen saturation
condition.
large volume of blood to be made available to the systemic
circulation by the selective vasoconstriction of the abdominal venous capacitance vessels. Small doses of ephedrine
or phenylephrine may rapidly increase available intracardiac volume so that Impella® flow remains high and the
left ventricle has volume to pump, thus restoring native
pulsatility.
Blood Oxygenation Monitoring During Impella
SUMMARY
Blood Oxygenation Monitoring
During Impella® Support
While on Impella® support, a patient’s blood flow inherently loses its pulsatile nature, which may cause a patient’s
pulsatility to drop or disappear completely. Clinicians may
It should be noted that although the blood pressure may
see a drastic drop or a “zero” value calculated for SpO2,
be flat and non-pulsatile, the patient is still displaying an
regardless
of the true arterial oxygen saturation. However,
acceptable blood pressure mean. Acceptable systemic oxy®
the
mean
blood
pressure should be adequate and in the
genation can be validated by a normal or unchanged exam
60–75 mmHg range and skin color and/or arterial blood
(skin color) or by arterial blood gas analysis.
gas analysis should reveal acceptable systemic oxygenation. Reducing Impella® support, if the patient can tolPulsatility can be returned by reduction of Impella® sup¥ Transilluminate a fingertip
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Basis of standard pulse oximetry
xygenation Monitoring During Impella Support
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discernable pulse,
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ofS., the
pulse
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false readings
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no pulsatility
which
is outside
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3. Slaughter,
et al. Clinical
management
of continuous-flow
left ventricular assist
devicesto
in advanced
heart failure. J Heart
Lung Transplant
2010;29:S1–S39.
pulse oximetry
fails
The root cause of the pulse oximetry false readings is low to no pulsatility which
1. Aldrich, Thomas K., MD. Pulseless Oximetry. Health & Bio Technology Summit. Bronx: Albert Einstein College of Medicine and Montefiore Medical Center, 2014. Print.
2. Wieben O, Light absorbance in pulse oximetry, in Design of pulsoximeters, J.G. Webster, Editor. 1997, Institute of Physics Publishing, Dirac House, Temple Back, Bristol
BS1 6BE, UK: Bristol. p. 40-55.
operating conditions for this monitoring method. Instead, some centers use cerebral oximetry for assessing
| 10 Instead, some centers use cereb
operating
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(3).GmbH
ABIOMED Inc.
ABIOMED Europe
www.abiomed.com
cine
22 Cherry Hill Drive
Neuenhofer Weg 3
dard Pulse Oximetry
and the Implications
of Non-Pulsatile
Flow (1,2)
hemodynamic
conditions
when
more invasive
monitoring
HCS-TB00992 rB
Danvers, MA 01923 USA
Phone 978-777-5410
Fax 978-777-8411
is not available (3).
52074 Aachen, Germany
Voice: +49 (241) 8860-0
Facsimile: +49 (241) 8860-111
Email: [email protected]
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