ecg monitoring, cardiac output and related parameters

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ECG MONITORING, CARDIAC

OUTPUT AND RELATED

PARAMETERSIan Christian A. Gonzales



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.



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.



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.



AFTERLOAD

The force resisting fiber shortening once systole

begins.

Clinically approximated by calculating for

systemic vascular resistance (MA P/CO)



CONTRACTILITY

Increases when the force of ventricular

contraction increases at constant preload and

afterload.

Difficult to quantify clinically.



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.



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.



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.



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.

ecg monitoring, cardiac output and related parameters

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