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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 with erate the reduction, or administering IV fluids to increase port level (if the patient can tolerate such a reduction) or at least 2 wavelengths, e.g., blood volume can return pulsatility. Pulsatility may also by Transilluminate increasing the available volumewith for the native a blood fingertip heart and the Impella® to pump. This can be accomplished 660nm (red) and 905nmbe restored by administering small doses of ephedrine or at least 2 wavelengths, e.g., (red) phenylephrine to rapidly increase 660nm left ventricular volume through IV fluid administration. A more rapid option is (infrared). 660nm (red) and 905nm and keep Impella® flow high. through the use of a vasoconstrictor allowing a relatively Basis of standard pulse oximetry xygenation Monitoring During Impella Support Basis of standard pulse oximetry ¥ 660 sis of standard pulse oximetry (infrared). ¥ Determine absorbance of each wavelength ¥ Determine absorbance of each by pulsing arterial From Weiben 1997 Flow (1,2) Figure 1: Basis of Standard Pulse Oximetry and the Implications of Non-Pulsatile wavelength by pulsing bloodarterial (and not other 905nm (infrared) a fingertip with From Weiben 1997 blood (and not other components of the fingertip) by lengths, e.g., • Transilluminate a fingertip with at least 2 660nm (red) components of the fingertip) bychanging (red) and 905nm nd 905nm wavelengths, e.g., 660nmmeasuring measuring changing (infrared). transmission during pulses transmission during pulses • Determine each wavelength orbance of each absorbance ¥ ofConvert to absorbance (really ¥ by Convert to absorbance (really pulsing arterial blood (and not other pulsing arterial attenuance). 905nm (infrared) Weiben 1997 attenuance). components of theFrom fingertip) Science the heart of medicine other Science at the heart of medicine byat measuring Calculate ratio transmission pulses ¥ changing Calculate ratio¥ ofduring attenuance of of attenuance of the fingertip) by red to attenuance of infrared From Weiben 1997 • Convert absorbance (really attenuance). red totoattenuance of infrared From Weiben 1997 nging • Calculate ratio of attenuance of red to uring pulses attenuance of infrared Without a discernable pulse, Without a discernable pulse, orbance (really dicine standard pulse oximetry fails standard pulse oximetry fails Without a discernable pulse, standard pulse oximetry fails of attenuance | 10 Science at of the heart of medicine Science at the heart of medicine ceFigure of infrared From Weiben 1997 1: Basis of Standard Pulse Oximetry and the Implications of Non-Pulsatile Flow (1,2) Figure 1: Basis of Standard Pulse Oximetry and the Implications of Non-Pu discernable pulse, The root causeMark ofS., the pulse oximetry false readings is low no pulsatility which is outside of the intended 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 conditions for this monitoring hemodynamic conditions when more invasive monitoring is notmethod. available (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] Support the Patient and Evaluate Reasons for Alarm. The first priority is always to support ® ulsepatient oximetry readings is lowthe to no pulsatility whichEvaluate isalarm outside ofReasons the intended supportThe is initiated andfalse evaluate potential reasons for an oximetry condition. When Impella Support Patient and for Alarm. first pr