7
Î Waveform capnography, which measures and displays the partial
pressure of end-tidal carbon dioxide (PETCO
2
) in exhaled air, can be
used to track perfusion in patients in whom more common physical
findings used to assess perfusion are not reliable.
• A PETCO
2
value of <20 mm Hg in an unresponsive, correctly intubated, pulseless
patient with an LVAD would seem to be a reasonable indicator of poor systemic
perfusion and should prompt rescuers to initiate chest compressions.
Î Peripheral pulse oximetry within normal limits is likely believable, but
a low oximetry reading may not represent true hypoxemia because of
the diminished pulsations seen in patients with an LVAD.
Î The likelihood of a favorable outcome after cardiac arrest increases
substantially if the event is witnessed, the event occurs in a public
place, bystanders call 9-1-1 and initiate chest compressions promptly,
the initial rhythm is VF, an automated external defibrillator is applied
and used, and there is a prompt EMS response.
• Therefore, it is the consensus recommendation that if an LVAD is definitively
confirmed by a trained person and there are no signs of life, bystander CPR,
including chest compressions, should be recommended by emergency medical
dispatchers for cardiac arrest situations.
• However, if mental status, breathing, skin color and temperature, and capillary
refill are adequate, a pulseless patient with an LVAD may be in an unconventional,
unique physiological state of hemodynamically stable pulseless electric activity
(PEA), which we refer to in this population as pseudo-PEA.
• Figure 7 illustrates the approach to such a patient.
Definitive Evaluation And Care
Î As soon as the expertise is available, two primary questions pertain:
Are the clinical symptoms attributable to an acute deterioration of
native cardiac function or LVAD malfunctioning?
• Assessment of inferior vena cava diameter, and its change during inspiration, will
provide an estimate of central venous pressure.
• Echocardiography can assess downward trends in right-sided heart function.
• Valve dysfunction can cause suboptimal LVAD performance.
• Impaired LVAD performance can be detected echocardiographically by noting an
enlarged le ventricular end-diastolic internal dimension (LVIDd) compared with
previous values obtained when the patient was stable.
