ECMO-/ECLS

systolic and diastolic pressures are back-calculated. Doppler measurement of
blood pressure is highly reliable for ascertaining systolic blood pressure, although
diastolic blood pressure is unreliable using this technique. In small neonates, the
cuff method usually overestimates BP, while in larger babies the cuff method
usually underestimates BP. If a baby is between cuff sizes, the larger size
should generally be used.
Invasive blood pressure monitoring with an arterial line is indicated for
patients with rapidly changing hemodynamics or if frequent labs or blood gas
analyses will be required. Arterial lines can be placed peripherally (radial,
dorsalis pedis, or posterior tibial) or more centrally (femoral, brachial, axillary or
umbilical). Caution should be exercised in placing arterial lines in the feet of
patients with anatomically impaired lower extremity circulation (diabetics or
peripheral vascular disease) due to risk of infection and unreliable tracings.
Furthermore, caution should be exercised in placing proximal/central arterial lines
due to the significant risk of thrombosis leading to limb ischemia and potentially
limb loss. Peripheral pulses should be documented frequently be the bedside
nurse in patients with proximal arterial lines. Arterial waveform transduction and
pressure measurement is dependent on the position of the catheter. Systolic
pressures are greater and diastolic pressures are lower in more distal vessels
due to pulse amplification of less elastic vessels. Pressures measured from
femoral or brachial lines will have a decreased pulse pressure. The MAP,
however, is constant across all points – peripheral or central. Arterial line
waveforms are subject to dampening or amplification (‘whip’). The waveform