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8/3/2019 ECG Monitoring, Cardiac Output and Related Parameters
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ECG MONITORING, CARDIAC
OUTPUT AND RELATED
PARAMETERSIan Christian A. Gonzales
8/3/2019 ECG Monitoring, Cardiac Output and Related Parameters
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ECG MONITORING
The electrocardiogram
records the electrical
activity associated
with cardiaccontraction by
detecting voltages on
the body surface.
A 3-lead ECG is
obtained by placingelectrodes that
correspond to the LA,
RA, and LL.
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ECG MONITORING
ECG waveforms can be continuously displayed on
a monitor and the device can be set to sound an
alarm if an abnormality of rate or rhythm is
detected. It is applied to critically ill andperioperative patients.
Additional information can be obtained from a
12-lead ECG.
A study of vascular surgical patients on
continuous 12-lead ECG monitoring showed that
the precordial lead V4 is the most sensitive for
detecting perioperative ischemia and infarction.
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PRELOAD
It is the stretch of the ventricular myocardium
just before the next contraction.
Determined by the EDV.
EDP is frequently used to estimate EDV, butEDP is determined by both volume and diastolic
compliance.
For the RV, CVP approximates EDP.
For the LV, P AOP approximates EDP. AV valvular stenosis will alter this relationship.
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AFTERLOAD
The force resisting fiber shortening once systole
begins.
Clinically approximated by calculating for
systemic vascular resistance (MA P/CO)
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CONTRACTILITY
Increases when the force of ventricular
contraction increases at constant preload and
afterload.
Difficult to quantify clinically.
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PULMONARY ARTERY CATHETER
The simplest form of P AC has 4 channels:
1. Terminates in a balloon at the distal end,
connected to a syringe at the proximal end.
2. A thermistor at the distal end is connected bywires to a fitting which allows connection to a
device which measures CO.
3. Terminates at the tip.
4. Terminates 20cm proximal to the tip.Channels 3 and 4 are used for pressure monitoring
and the injection of the thermal indicator for CO
determination.
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P A CATHETERIZATION
Requires access to
central venous circ.
via the antecubital,
femoral, jugular, or
subclavian vein.
Right internal jugular
vein cannulation has
the lowest risk, and
the catheter path tothe RA is straight.
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P A CATHETERIZATION
Vein cannulation is
done percutaneously
using the Seldinger
technique.
The balloon is inflated
and the catheter is
advanced while
monitoring pressures
on an oscilloscope.
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P A CATHETERIZATION
The catheter isadvanced out thepulmonary arteryuntil a damped
tracing indicative of the wedged position isobtained.
The balloon is thendeflated. Leaving it
inflated can increasethe risk of pulmo.infarction orperforation.