Cardiovascular monitoring By Dr. Ahmed Mostafa Assist. Prof. of anesthesia and I.C.U.

Cardiovascular monitoring

ByDr. Ahmed Mostafa

Assist. Prof. of anesthesia and

I.C.U.

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I. Non-invasive:Clinical observations:

An altered general condition.

An alteration of the mental state.

Observations of capillary refill and other signs

of the peripheral circulation.

I. Non-invasive:

Pulse examination:

- By palpation.

- With an ECG monitor.

- From the arterial pressure curve.

- Finger photoplethysmography: this method is based on the

fact that light can pass through the capillary network. The

pulsation of the arteries modifies the volume of the tissues, and

this influences the absorption, reflection and scattering

properties of light.

I. Non-invasive:Noninvasive measurement of blood pressure:

a)Mercury manometer:


b) Bourdon aneroid

manometer:


c) Oscillotonometry:

• systolic and diastolic pressures correspond to the points of rapidly increasing and decreasing oscillations, respectively.

• Mean arterial pressure corresponds to the point of maximal cuff pressure fluctuation.


d) Ultrasound blood pressure measurement:


d) Ultrasound blood pressure measurement:

Advantages: can be used in infants, in patients

with low blood pressure and in a very noisy

environment.

Disadvantage: Affected by movement.

I. Non-invasive:Electrocardiography (ECG):

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Indications:

1)Diagnosis of rhythm disorders.

2)Pathological changes of the myocardium (e.g.

hypertrophy hypoxia or myocardial necrosis).


Indications:

4)Diagnosis of conduction abnormalities.

5)Diagnosis of pace maker malfunction.

6)Detect electrolyte imbalances.


Types:

1)3 lead ECG.

•Red - right arm.

•Yellow - left arm.

•Black (or Green) - left leg (or more often in the region of the apex beat.)


Types:

2) 5 lead ECG.

3) 12 lead ECG.

4) Holter ECG.

II. Invasive cardio-vascular monitoring:

Invasive blood pressure measurements:



Advantages:

Very accurate in vivo monitoring (arterial, intrauterine, intra -

cranial or intraocular pressures).

Can detect very small high-frequency pressure changes.



Disadvantage:

The transfer characteristic is completely nonlinear (there is a

nonlinear connection between the blood pressure and the

reflected light quantum).

Sediment blood on the surface of the membrane distorts the

modulation of light.



Problems of invasive pressure measurements:

1. Resonance:

Causes:

- Increase the radius of the cannula and catheter.

- Decrease the length of the cannula and catheter.




1. Resonance:

Causes:

- Lower compliance (Stiffer tube).

- Decrease of the fluid consistency.




2. Damping:

Causes:

- Air bubble.

- Kinking of the cannula and catheter.




2. Damping:

Causes:

- Arterial spasm.

- Clot formation in the system.



Complications after arterial catheterization:

Bleeding and arterial thrombosis.

Infection and Hematoma formation.

True and false aneurysm formation.

Distal and central embolization.


Central venous catheter:



Technique of central venous catheterization:

Needle-cannula combinations:

- Catheter on needle.

- Catheter in needle.



Technique of central venous catheterization:

Seldinger technique:

This is the most widespread process for

catheterizations of deep vessels such central veins

or the femoral artery.



• Indications of central venous catheterization:

The injection of compounds damaging the venous endothelial

layer.

Longer (3–5 days) volume therapy.

Parenteral nutrition.

Circulatory shock.



• Indications of central venous catheterization:

Measurement of central venous pressure.

Pacemaker implantation.

If there is no peripheral venous access, but venous access is

indicated



• Contraindications of central venous catheter:

Thrombosis, thrombophlebitis, or bacterial vegetation on the

tricuspid valve. Anticoagulant therapy or carotid artery stenosis on

the same side could mean a relative contraindication.



• Complications of catheterization are:

Thrombosis, thrombophlebitis.

A catheter embolus.

Sepsis and Local inflammatory infiltration.

Pneumothorax.

Bleeding.


Central venous pressure (CVP):

• The CVP indicates the right ventricular preload.

• It demonstrates the severity of hypo- or

hypervolemia.



the CVP is measured by water column manometer.

It is expressed in cm H₂O. The normal value

above a point level with the right atrium in a

patient lying flat is 5–10 cm H ₂O.



• The CVP is elevated in cases of:

↑ ↑ intra-thoracic pressure.

An impaired Rt cardiac function.

Hypervolemia (overfilling).

Superior vena cava obstruction.



• Decreased CVP in:

↓↓ intra-thoracic pressure.

Hypovolemia (if a volume challenge of 250–

500 mℓ of crystalloid causes ↑↑ in CVP that

is not sustained for more than 10 min.


Measurement of pulmonary artery pressure:



• The catheter has 4 or 5 lumens.

Yellow is the channel for pulmonary pressure.

Blue is a CVP port, its hole is at 29 cm from its end.

White is the thermistor cable (at the end of the catheter).

The red channel (the balloon located near the tip of the catheter).

The fifth channel is a reference thermistor cable for measuring

the temperature of injected saline.


Value of measurement of pulmonary artery pressure:

Direct hemodynamic parameters:

Central venous pressure.

Pulmonary artery systolic and diastolic pressures.

Pulmonary capillary wedge pressure.

Cardiac output (thermo-dilution methods).

Blood temperature.



Direct hemodynamic parameters:



Derived (calculated) hemodynamic data:



Other variable with sampling of mixed venous blood:

O2 delivery (D•O2):

It is the amount of O2 delivered to the capillaries/ minute.

D•O2 = CO × CaO2.

= CO × (Chemically combined with Hb + physically dissolved in plasma).

= CO × ({Hb × 1.38 × SaO2%} + {0.003 × PaO2}).

= CO × ({15 × 1.38 × 97%} + {0.003 × 95}).




O2 delivery (D•O2):

= CO × 20.6 ml /dl.

As {0.003 × PaO2} is of little value so, it has a little effect.

So, D•O2 = CO × {Hb × 1.38 × SaO2%}.

= 850 – 1050 ml/ min.




O2 Uptake (V•O2):

It is the amount of O2 taken from the capillaries/ minute.

V•O2 = CO × (CaO2 – CύO2).

= CO × Hb × 1.38× (SaO2 - SύO2).

= 250 ml/min.




O2 extraction ratio (O2 ER):

O2 ER = V•O2 / D•O2

= 20 – 30 %.

Mixed venous oxygen tension and saturation (SύO2).


Indications of pulmonary artery pressure:

Ischemic heart disease with recent myocardial infarction.

Symptomatic valvular heart disease.

Serious cardiomyopathy.

Congestive heart failure and low ejection fraction.

Shock (septic or hypovolemic).

Pulmonary hypertension.

Cardiac surgery or severely loading surgery with a poor

ventricular function.


Complications of pulmonary artery pressure:

As CVP catheterization.

Specific complications are:

Arrhythmias.

Thrombosis and embolization.

Pulmonary infarct or bleeding.

Endocarditis.

Atrial and ventricular perforations.


Measurement of cardiac output:

A. Invasive techniques:

1. Fick’s principle:

- The amount of oxygen consumed by an individual equals the

difference between arterial and venous (a–v) oxygen content (C)

(CaO2 and CvO2) multiplied by cardiac output (CO).

- It the standard method of measurement of CO to which all the

other methods are judged.




2. Indicator dilution technique:

By using Indocyanine green which has the following advantages:

- Nontoxic.

- Short half-life.

- Measurement is not affected by changes in oxygen saturation.




3. Lithium Dilution:

Another indicator dilution technique employs intravenously injected

ionized lithium as the indicator.




4. Thermo-dilution technique:

- It is the technique used now a day.

- Idea: 10 ml of cold normal saline or dextrose 5% is injected into

the right atrium and the temperature change of blood is recorded

by a thermistor in the pulmonary artery,





- The degree of change is inversely proportional to the cardiac

output.

- Plotting the temperature change as a function of time produces a

thermo-dilution curve.





- Cardiac output is determined by a computer program that integrates the

area under the curve.





- Advantages:

- Easy and cheap.

- Repeated measurements can be made using pulsed thermo-

dilution technique.





- Advantages:

- Arterial puncture and blood withdrawal is not necessary.

- Absence of recirculation of the indicator gives more accurate

results.



B. Non-invasive techniques:

1. Thoracic Bio impedance:

Changes in thoracic volume cause changes in thoracic resistance (bio-impedance). If

thoracic changes in bio-impedance are measured following ventricular depolarization,

stroke volume can be continuously determined. This non-invasive technique requires four

pairs of ECG electrodes to inject micro-currents and to sense bio-impedance on both sides

of the chest.




1. Thoracic Bio impedance:

Disadvantages: include susceptibility to electrical interference and reliance upon correct

electrode positioning. As with both suprasternal and trans-tracheal Doppler, the accuracy of this

technique is questionable in several groups of patients, including those with aortic valve disease

or previous heart surgery.




2. Ultrasonography: TEE: Value:

- Assesses left ventricular filling (end-diastolic volume and end-

systolic volume).

- Ejection fraction.

- Wall motion abnormalities, and contractility.




2. Ultrasonography: TEE: Value:

- Very sensitive indicator of intraoperative myocardial ischemia.

- Very early recognition of air embolism.




2. Ultrasonography: TEE: Limitations:

- The need for the patient to be anesthetized before insertion.

- Oversized esophageal probes can cause aortic compression in

infants and small children.




2. Ultrasonography: Pulsed Doppler:

Doppler is a related technology that can be used to measure the

velocity of aortic blood flow. Combined with TEE, which

determines the aortic cross-sectional area, this technique can

measure stroke volume and cardiac output.




2. Ultrasonography: trans-esophageal Doppler :

- Evaluates valvular function and intra-cardiac shunting.

- Information on blood flow is represented by color (indicating

flow direction) and intensity (indicating flow velocity).




2. Ultrasonography: Continuous-wave suprasternal Doppler:

also measures aortic blood velocity.

Trans-tracheal Doppler :consists of a Doppler transducer attached

to the distal end of a tracheal tube. Cardiac output is derived from

the ascending aorta diameter and blood velocity.




3. Pulse Contour-Derived Cardiac Output:

Calculate stroke volume from the area under the arterial pressure

waveform.

Trans-esophageal echocardiography


- The esophageal Doppler method was first used to measure the velocity of blood flow in the 1960s, but the ultrasound apparatus has been applied to measure cardiac output widely only since the 1990s.

- A small examining head is introduced into the esophagus, which allows the heart and mediastinum to be examined more effectively.

- The movements of the ventricular wall, changes in volume of the cardiac cavities and morphological changes of the heart can be investigated.


Modes: The motion (M) mode: shows the movement

of the interfaces as a function of time (e.g. a pulse wave passing through a vessel section is shown by converging and diverging wave lines of the vessel walls).

The (B) mode: visualizes the intensity of

individual echoes with light points of different

intensity and produces a two dimensional picture.


Color-coded mode:

the flow in the cranial

direction is indicated in

red and that in the

opposite direction in

blue.

Trans-esophageal echocardiography Indications :

- Ischemic conditions (indicated by movement

disorders of the heart wall).

- Measurement of the ejection fraction.

- Examination of the heart valves.

- Recognition of intra-cardiac thrombi, tumors and air.

- Endocarditis (endocardial vegetation).

Trans-esophageal echocardiography Contraindication:

- In severe esophageal diseases (stricture, tumor or varix).

- In severe coagulopathy.

- Esophagus perforation.

- Gastrointestinal bleeding.

- Esophageal burn.

- Transient vocal cord edema.

Thank youDr. Ahmed Mostafa

Cardiovascular monitoring By Dr. Ahmed Mostafa Assist. Prof. of anesthesia and I.C.U.

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Transcript of Cardiovascular monitoring By Dr. Ahmed Mostafa Assist. Prof. of anesthesia and I.C.U.