ECMO-/ECLS

consists of three components: 1) systolic upstroke, 2) dicrotic notch signifying
closure of the aortic valve and 3) diastolic runoff. Loss of the dicrotic notch is
associated with a dampened waveform and excessive peaking of the upstroke is
associated with pulse pressure amplification.
Arterial waveforms are subject to several operator errors. First, the device
must have a zero point (reference zero) for purposes of transduction. In general
this should be the interatrial axis of the heart the external analog of which is the
mid-axillary line of the 4th intercostal space. Changes in relative position of the
patient or transducer may artificially alter the recorded values. Second, catheter
malposition may result in dampened waveforms. Third, respiratory variation,
which may be amplified in hypovolemic states, may cause relatively wide swings
in arterial pressure recordings. Indeed, this finding forms the basis for many
newer technologies that purport to analyze cardiac preload and effectiveness of
volume administration.
At least one company has FDA approval for a device that calculates
cardiac output using indicator dilution and arterial line sampling. The technology
has been validated versus thermodilution technologies in adults but there is
limited data in young children.
Operative arterial lines require additional considerations. Unlike
percutaneous techniques, methods of open insertion often result in vessel
ligation. Though in the majority of patients this may be done without sequelae,
the clinician should consider the likelihood of disease chronicity and recurrence
(congenital heart disease), duration (multisystem organ failure), vascular disease