Cardiac monitoring begins with rhythm and rate evaluation and surrogate
measures of function such as blood pressure. As circumstances dictate, more
detailed evaluation may require additional measures such as cardiac preload
(central venous pressure, RV end diastolic pressure/volume, pulmonary arterial
diastolic or wedge pressures), cardiac output, and the match between systemic
oxygen delivery and consumption (SvO 2 =mixed venous oxygen saturation). In
recent years, many of the more invasive measures have been deemed
unnecessary and surrogates have been increasingly used as indicators of
cardiac function.
Standards of care dictate that all ICU patients should be monitored at a
minimum with continuous ECG and non-invasive blood pressure cuff.
A. Blood Pressure Monitoring
Blood pressure can be monitored either invasively or non-invasively.
Noninvasive blood pressure (NIBP) monitoring with a blood pressure cuff can be
performed using a variety of methods. For all methods, the cuff bladder should
cover at least 75% of the appendage circumference. The traditional auscultatory
method (listening for Korotkoff sounds with a manual cuff over the brachial
artery) is the most reliable noninvasive method, but requires the practitioner to
repeat the measurement frequently. It is limited in low stroke-volume states or
continuous flow (ECLS) in which circumstances doppler (see below) methods
should be utilized. Automated oscillometric techniques measure the oscillometric
waveform as the cuff deflates to determine a mean arterial pressure (MAP) and