8-monitoring during anesthesia

8/14/2019 8-Monitoring During Anesthesia

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MonitoringMonitoring

duringduring AnesthesiaAnesthesia


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Perioperative periodPerioperative period

operationoperation postoperationpostoperationpreoperationpreoperation

operative evaluationoperative evaluation

and preparationand preparation anesthesiaanesthesia

Induction ofInduction of

anesthesiaanesthesia

Maintenance ofMaintenance of


Recovery fromRecovery from


Monitoring during anesthesiaMonitoring during anesthesia


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The word monitor is derived from the LatinThe word monitor is derived from the Latin

verbverb moneremonere to warn. The purpose of a to warn. The purpose of amonitoring device is to measure amonitoring device is to measure aphysiological variable and to indicatephysiological variable and to indicatetrends of change, thus enablingtrends of change, thus enabling

appropriate therapeutic action to be taken.appropriate therapeutic action to be taken. It is essential to ensure that all monitoringIt is essential to ensure that all monitoring

equipment is maintained correctly andequipment is maintained correctly andthat it functions accurately, so that thethat it functions accurately, so that the

information which it provides is reliableinformation which it provides is reliable The user should understand the basicThe user should understand the basic

principles on which monitoring equipmentprinciples on which monitoring equipmentis based and be able to interpret theis based and be able to interpret the

information provided.information provided.


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MonitoringMonitoring duringduring

AnesthesiaAnesthesia Cardiovascular SystemCardiovascular System

Respiratory systemRespiratory system

Body Temperature: geriatric, pediatricBody Temperature: geriatric, pediatric

Neuromuscular Junction: muscularNeuromuscular Junction: muscular

relaxantrelaxant

Nervous System: depth of anesthesiaNervous System: depth of anesthesia

Coagulation System: cardiothoracicCoagulation System: cardiothoracic

surgerysurgery


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PARTPART

THE CARDIOVASCULARTHE CARDIOVASCULAR

SYSTEMSYSTEM


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Electrocardiogram (EElectrocardiogram (ECCG)G)

ECG monitors have become increasinglyECG monitors have become increasingly

reliable and less subject to interference.reliable and less subject to interference.

As the technique is non-invasive, simpleAs the technique is non-invasive, simple

and accurate, it is now regarded asand accurate, it is now regarded as

mandatory in the UK that the ECG shouldmandatory in the UK that the ECG should

be monitored in all patients undergoingbe monitored in all patients undergoinganaesthesia, no matter how minor theanaesthesia, no matter how minor the

surgery procedure.surgery procedure.


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One of the standardized monitors duringOne of the standardized monitors during

any form of anesthesia.any form of anesthesia.

For detection and diagnosis ofFor detection and diagnosis of

DysrhythmiasDysrhythmias: Tachycardia, Bradycardia,: Tachycardia, Bradycardia,VFVF

CConduction defectsonduction defects: AVB: AVB auriculo-ventricular blockCCardiac ischemiaardiac ischemia: CAD: CAD

EElectrolyte disturbancelectrolyte disturbance: Potassium,: Potassium,

MagnesiumMagnesiumhyperkalemia, hypokalemia


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Types of MonitoringTypes of Monitoring

Five-electrode system: one onFive-electrode system: one on

each leach limbimb and one precordial leadand one precordial lead

(V(V5,5, along the anterior axillary linealong the anterior axillary line

in the fifth intercostal spacein the fifth intercostal space forfor

detection of anterior ischemia).detection of anterior ischemia).


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PPrecordial leadrecordial lead

Midclavicular line

Anterior axillary line Midaxillary line

Posterior axillary line


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Standard limb lead


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Standard lead II monitoring is usedStandard lead II monitoring is used

widely.widely.

However, the CMHowever, the CM55 lead configuration haslead configuration has

been advocated for routine intraoperativebeen advocated for routine intraoperative

monitoring because it reveals moremonitoring because it reveals more

readily ST segment changes produced byreadily ST segment changes produced by

left ventricular ischaemia.left ventricular ischaemia.


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Right arm lead overmanubrium sterni


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KaplanKaplan et al.et al. (Anesthesiology, 1976):(Anesthesiology, 1976):

90% of intraoperative cardiac ischemia will90% of intraoperative cardiac ischemia will

be detected by multiple Ebe detected by multiple ECCG, especially VG, especially V55..

At least two leads should be simultaneouslyAt least two leads should be simultaneously

showed on the monitor.showed on the monitor.


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Position of the LeadsPosition of the Leads

The four limb leads should be placed onThe four limb leads should be placed on

the back of shoulders and hips, wherethe back of shoulders and hips, where

they will disturb the operative field thethey will disturb the operative field theleast.least.

Every lead should be fixed and protectedEvery lead should be fixed and protected

with tape to prevent dislodgement ofwith tape to prevent dislodgement ofleads during operation.leads during operation.


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It is important to appreciate that the ECGIt is important to appreciate that the ECG

is an index only of electrical activity. It isis an index only of electrical activity. It is

possible for a normal electrical waveformpossible for a normal electrical waveformto exist in the presence of a negligibleto exist in the presence of a negligible

cardiac output.cardiac output.

Consequently, information from the ECGConsequently, information from the ECGshould be used in conjunction with datashould be used in conjunction with data

acquired from monitoring of perfusionacquired from monitoring of perfusion


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Monitoring the circulationMonitoring the circulation Maintenance of perfusion of vital organs is oneMaintenance of perfusion of vital organs is one

of the principal tasks of the anaesthetist duringof the principal tasks of the anaesthetist during

surgery. Adequate perfusion is dependent onsurgery. Adequate perfusion is dependent on

adequate venous return to the heart, cardiacadequate venous return to the heart, cardiac

performance and arterial pressure.performance and arterial pressure. Direct measurements of cardiac output andDirect measurements of cardiac output and

blood volume are difficult during anaesthesiablood volume are difficult during anaesthesia

and require invasive procedures which areand require invasive procedures which are

inappropriate in many situations.inappropriate in many situations.


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Monitoring the circulationMonitoring the circulation However, adequacy of cardiac output andHowever, adequacy of cardiac output and

circulating blood volume may be inferredcirculating blood volume may be inferred

indirectly from observation of the followingindirectly from observation of the following

variables:variables:

1. Peripheral pulse.1. Peripheral pulse.

2. Arterial oxygen saturation.2. Arterial oxygen saturation.

3. Peripheral perfusion.3. Peripheral perfusion.

4. Urine production.4. Urine production.

5.Arterial pressure.5.Arterial pressure.


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1.Regular palpation of the peripheralpulse is one of the simplest and most

useful methods of monitoring during

anaesthesia and is mandatory for even

the most minor surgery. (Radial artery)

2.Information may be obtained by

observation of the rate, volume and

rhythm.

The peripheral pulseThe peripheral pulse


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1.Pulse oximeters measure the arterial

oxygen saturation and the pulse rate

non-invasively and accurately to within

2%.

2.A simple probe is attached to a finger

an ear lobe, flexed across the nasalbridge, or wrapped around a childs digit

and connected to the oximeter.

3.The probe contains two light-emittingdiodes, one for red and one for infrared

light, and a single detector positioned

on the opposite side of the digit or ear

lobe.

Pulse oximetryPulse oximetry


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Pulse oximetry----ProbePulse oximetry----Probe

Finger probe forpulse oximeterattached to afinger


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Pulse oximetry----Pulse oximetry----

ProbeProbe

Disposable fingerprobe for pulseoximeterwrapped around a

childs digit


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Pulse oximetry----Pulse oximetry----

OximeterOximeter

Pulseoximeter

control anddisplaymodule,probe is

connected to

Waveform S

pO2

Pulse rate


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Pathophysiology:

Oxygen is exchanged by diffusion fromOxygen is exchanged by diffusion from

higher concentrations to lowerhigher concentrations to lower

concentrationsconcentrations

Most of the oxygen in the arterial blood isMost of the oxygen in the arterial blood is

carried bound to hemoglobincarried bound to hemoglobin

-97% of total oxygen is normally bound to-97% of total oxygen is normally bound tohemoglobin (hemoglobin (SpOSpO22))

-3% of total oxygen is dissolved in the-3% of total oxygen is dissolved in the

plasma (Paplasma (PaOO22))


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Oxygen Saturation: Percentage of hemoglobin saturated withPercentage of hemoglobin saturated with

oxygenoxygen

Normal SpONormal SpO

22 is 95-98%is 95-98%

Suspect cellular perfusion compromise ifSuspect cellular perfusion compromise if

SpOSpO22 is less than 95%is less than 95%

-Insure adequate airway-Insure adequate airway

-Provide supplemental oxygen-Provide supplemental oxygen

-Monitor carefully for further changes and-Monitor carefully for further changes and

intervene appropriatelyintervene appropriately


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Oxygen Saturation:

Suspect severe cellular perfusionSuspect severe cellular perfusion

compromise when SpOcompromise when SpO22 is less than 90%is less than 90% Insure airway and provide positiveInsure airway and provide positive

ventilations if necessary.ventilations if necessary.

Administer high flow oxygen.Administer high flow oxygen. Head injured patients, SpOHead injured patients, SpO22shouldshould

never drop below 90%.never drop below 90%.


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SpO2 and PaO2:

SpOSpO22 indicates the oxygen bound toindicates the oxygen bound to

hemoglobinhemoglobin-Closely corresponds to SaO-Closely corresponds to SaO22 measured inmeasured in

laboratory testslaboratory tests

-SpO-SpO22 indicates the saturation wasindicates the saturation was

obtained with non-invasive oximetryobtained with non-invasive oximetry

PaOPaO22 indicates the oxygen dissolved in theindicates the oxygen dissolved in the

plasmaplasma

-Measured in ABGs (artery blood gases)-Measured in ABGs (artery blood gases)


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SpO2 and PaO2:

Normal PaONormal PaO22 is 80-100 mmHgis 80-100 mmHg

NormallyNormally

80-100 mm Hg corresponds to 95-100%80-100 mm Hg corresponds to 95-100%

SpOSpO22

60 mm Hg corresponds to 90% SpO60 mm Hg corresponds to 90% SpO22

40 mm Hg corresponds to 75% SpO40 mm Hg corresponds to 75% SpO22


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1.Pulse oximeters are simple to use, non-

invasive and require no warm-up time.

2.Provide an overall assessment of the

integrity of all the systems involved in

delivering oxygen to the tissues

Oxygen supply, intake and delivery.

3.unaffected by pigmented skin


Advantages:


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1.It is assessed most usefully by

observation of the patient's extremities.

2.Warm, dry, pink skin indicates adequate

peripheral perfusion; cold, white

peripheries the converse

3.This is particularly true in children, inwhom cool peripheries usually indicate

hypovolaemia.

Peripheral perfusionPeripheral perfusion


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1.The core-peripheral temperature

gradient is a useful index of adequacy

of peripheral perfusion.

2.One temperature probe is placed

centrally (e.g. in the nasopharynx) and

the other peripherally (e.g. on the greattoe)

3.The temperature gradient increases

with vasoconstriction and low cardiacoutput, and decreases gradually as

vasodilation occurs with increasing limb

blood flow consequent upon increasing

cardiac output.

Peripheral perfusionPeripheral perfusion


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1.Adequacy of renal perfusion may be

inferred from the volume of urine

produced

2.The kidney is the only organ whose

function may be monitored directly in

this way.

3.Adequate production of urine implies

that perfusion of other vital organs is

Urine outputUrine output


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1.Accurate measurement of urine

volumes with a urimeter is particularly

indicated in the following situations:

Urine outputUrine output

6. Surgery in the jaundiced

patient.

3. Major trauma.

5. Massive fluid or blood

loss

2. Cardiac surgery.

4. Critically ill/shocked

patients

1. Major vascular

surgery.

aim is to achieve a urine output of 0.5~1ml.kg-1.h-1


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3 It is an indirect method of estimating


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3. It is an indirect method of estimating

adequacy of

cardiac output, because:

Blood pressure CO peripheral

resistance

4. In conjunction with estimation ofperipheral

perfusion, it is an invaluable

measurement.

6. Indirect, non-invasive methods of

measurement

Systemic arterialSystemic arterial

pressurepressure


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Palpation of the radial pulse as the

sphygmoma-nometer cuff is deflated is

a simple method of measuring systolic

pressure, but is inaccurate at low

pressures or when vasoconstriction is

present.


pressurepressurePalpation :


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1.Auscultation of the Korotkoff sounds is

too cumbersome for routine use during

anaesthesia.


pressurepressureAuscultation :


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pressurepressureOscillometry (2):

an automated oscillometer


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Multifunctional Monitor


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Cuff SizeCuff Size

Too small cuff will result in highToo small cuff will result in high

blood pressure reading.blood pressure reading. A loosely applied cuff will alsoA loosely applied cuff will also

produce a reading higher than itproduce a reading higher than it

should be.should be.

Too large cuff will severelyToo large cuff will severely


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Cuff SizeCuff Size

from Barbara Bates: A Guide to Physical

Examination


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a.Inaccurate when SBP less than 60mmHg

.

b. Unable to follow rapid swings in arterial

pressure .

c. Under-reading occurred at high systolic

pressures

Disadvantages:


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1. It is achieved by attaching a

transducer to an intra-arterial cannula

inserted into a peripheral artery.

2. It is an invasive procedure which

carries potential morbidity.

3. The method is only justified whenrapid changes in arterial pressure are

anticipated during anaesthesia.

Direct measurement ofDirect measurement of

ABPABP


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IABP system

CannulaManometertubeTransducerMonitor


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1. The transducer should be zeroed, and

the system should be calibrated.

2. The transducer is connected to the

cannula via a piece of stiff-walled,saline-filled manometer tube.

3. The pressure signal is displayed as a

waveform on an oscilloscope screen and

systolic, diastolic and mean arterial

pressures displayed digitally.


ABPABP


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Common indications for arterialcannulation:


ABPABP

Major vascular surgery

Cardiothoracic surgery

Induced hypotension

Critically ill and shocked patients

Surgery for pheochromocytoma

Neurosurgery

Necessity for frequent blood gas analysis


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Morbidity associated with arterialcannulation :


ABPABP

1. Arterial wall damage and

thrombosis

2. Embolization

3. Disconnection and

haemorrhage4. Sepsis

5. Tissue necrosis


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ABPABP

Site for Arterial Cannulation:

1. Radial artery:

2. Femoral artery:

3. Brachial artery:

4. Dorsalis pedis artery:


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1. A central venous catheter positioned

with its tip in the superior (inferior) vena

cava.

2. It provides valuable information

concerning the volume status of thecirculation during anaesthesia.

3. A direct measurement of RV filling

pressure, CVP is good measurement of

LV filling pressure only in the absence of

pulmonary hypertension or mitral

Central venousCentral venous

pressure (CVP)pressure (CVP)


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tip in the superior

Internal jugular

vein

External jugular

vein


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Femoral Vein


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pressurepressure

Site for Vein Cannulation:

1. Internal jugular vein

2. External jugular vein3. Subclavian vein

4. Femoral vein

5.Peripheral arm vein


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Peripheral arm vein :


pressurepressure1.This route is the least likely to provide

correct placement of the catheter

(approximately 40%)

2.It avoids most of the serious

complications of other routes of

insertion.

3.Thrombophlebitis and sepsis are

common when a peripheral arm vein is

used, particularly if the catheter is left


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Internal jugular cannulation:


pressurepressure

This route is associated with the

highest incidence of correct

catheter placement (approximately

90%).


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Technique for right internal jugularTechnique for right internal jugular

vein central venous cannulation.vein central venous cannulation.

P t


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(A) Important surface landmarks are identified.(A) Important surface landmarks are identified.

(B) The course of the internal carotid artery is palpated.(B) The course of the internal carotid artery is palpated. (C) The internal jugular vein is punctured at the apex of(C) The internal jugular vein is punctured at the apex of

the triangle formed by the two heads of thethe triangle formed by the two heads of thesternocleidomastoid muscle with the needle tip directedsternocleidomastoid muscle with the needle tip directedtoward the ipsilateral nipple.toward the ipsilateral nipple.

(D) A guide wire is introduced through the thin-wall(D) A guide wire is introduced through the thin-wallneedle into the vein.needle into the vein.

(E) The central venous cannula is inserted over the(E) The central venous cannula is inserted over theguide wire, making sure that the proximal end of theguide wire, making sure that the proximal end of theguide wire protrudes beyond the catheter and isguide wire protrudes beyond the catheter and is

controlled by the operator. See text for greater detail.controlled by the operator. See text for greater detail.

PunctureProcedure

C l


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Complications of internal jugularcannulation:


pressurepressure

1. Air embolism

2. Carotid artery puncture

3. Brachial plexus/phrenic nerve

damage

4. Ectopic placement (numerous

sites)5. Sepsis

6. Pneumothorax

lC t l


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Subclavian vein:


pressurepressure

1.This approach is more hazardous

than the internal jugular, and less

likely to provide correct catheter

placement.

2.It is the most suitable route if long-

term parenteral feeding.

C lC t l


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Complications of subclavian veincannulation :


pressurepressure

1. Pneumothorax

2. Subclavian artery puncture

3. Air embolism

4. Damage to thoracic duct (left

side)


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Measurement should be done atMeasurement should be done at end-end-

expirationexpiration phase.phase.


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Right atriumCVP


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C t lC t l


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Measurement of CVP:


pressurepressure1.The normal range of values is

0~6cmH2O in the spontaneously

breathing patient.

2.In patients receiving IPPV values of

CVP are approximately 5 cmH2O higher

because of the increased mean

intrathoracic pressure

3.Trends in measured observations are

C t lC t l


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Increase of CVP :


pressurepressure

1. Over hydration

2. Right-sided heart failure3. Cardiac tamponade

4. Constrictive pericarditis

5. Pulmonary hypertension6. Tricuspid stenosis and regurgitation

7. stroke volume is high

Pulmonary artery pressurePulmonary artery pressure


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monitoringmonitoring

It can measure:It can measure:

2.2. PA pressurePA pressure

3.3. Pulmonary capillary wedged pressurePulmonary capillary wedged pressure(PCWP): a balloon at catheter tip(PCWP): a balloon at catheter tip

(volume 1.5 ml), when the balloon is(volume 1.5 ml), when the balloon is

inflated and the vessel is wedged, ainflated and the vessel is wedged, a

valveless hydrostatic column existsvalveless hydrostatic column existsbetween the distal port and LA.between the distal port and LA.

PAPPAC (Swan-PAPPAC (Swan-Ganz)Ganz)



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monitoringmonitoring

1.1. CVP: a port for CVP measurement isCVP: a port for CVP measurement is

located at 30 cm from the tiplocated at 30 cm from the tip

2.2. Cardiac output: measurement of RVCardiac output: measurement of RV

outputoutput

3.3. Blood temperatureBlood temperature

4.4. Derived hemodynamic dataDerived hemodynamic data

n Mixed Venous OMixed Venous O22 saturation (SvOsaturation (SvO22))

The Pulmonary ArteryThe Pulmonary Artery


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The Pulmonary Arteryy y

CatheterCatheter

(PA catheter, Swan-Ganz)(PA catheter, Swan-Ganz)

PAP, PCWP, SvO2

CVP

Blood temperature CO

Administration


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Pulmonary Artery CatheterPulmonary Artery Catheter1. The proximal lumen. This is situatedapproximately 25 cm from the tip and should lie in

the right atrium after final placement of the catheter.

CVP may be measured using this lumen.

2. The distal lumen Situated at the tip of thecatheter, this lumen lies in a major branch of the

pulmonary artery when the catheter is placed

correctly and is used to measure pulmonary artery

pressure by connecting it to a suitable transducer.

3. The balloon lumen. This lumen permits the

introduction of approximately 1.5 ml of air into the

ballon which surrounds the distal tip of the lumen.

4. Thermistor lumen. A bead thermistor is

situated 4cm from the tip of the catheter and

measures the tem erature of blood at this site.

P l A tPulmonary Artery


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Pulmonary ArteryPulmonary Artery

CatheterCatheter

PA Port:PA Port:YELLOWYELLOW

CVP Port:CVP Port:BLUEBLUE

PA balloon Port:PA balloon Port:REDRED

1 Distal port opening is at1 Distal port opening is at


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1. Distal port opening is at1. Distal port opening is at

the tip (end) of thethe tip (end) of the

cathetercatheter.. pulmonary artery pressures (PAP)pulmonary artery pressures (PAP) systolic (PAS)systolic (PAS)

diastolic (PAD)diastolic (PAD) pulmonary capillary wedge pressure (PCWP)pulmonary capillary wedge pressure (PCWP)

when balloon is inflated PA pressures shouldwhen balloon is inflated PA pressures shouldalways be monitored continuouslyalways be monitored continuously

NEVER USENEVER USE for medication infusionfor medication infusion Can be used for drawing "mixed venous" bloodCan be used for drawing "mixed venous" blood

gas samplegas sample


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2.2.Balloon portBalloon port

located about < 1 cm from tip of the catheterlocated about < 1 cm from tip of the catheter

the balloon is inflated with proximately 0.8 to 1.5 ccthe balloon is inflated with proximately 0.8 to 1.5 cc

of airof air do not inflate with liquid---- always inflate with airdo not inflate with liquid---- always inflate with air

when deflated, turn stopcock to off position andwhen deflated, turn stopcock to off position and

leave syringe connect to portleave syringe connect to port

3 Th i t d3 Th i t d


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3. Thermistor and3. Thermistor and

connector portconnector port the thermistor connector connects thethe thermistor connector connects thepulmonary catheter to the cardiac outputpulmonary catheter to the cardiac outputcomputercomputer

thermistor wire within the lumen transmitsthermistor wire within the lumen transmitsblood temperature (core temperature is mostblood temperature (core temperature is mostaccurate reflection of the body temperature)accurate reflection of the body temperature)used in determiningused in determining cardiac outputcardiac output

i l4 P i l t


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4.Proximal port 4.Proximal port

approximately 30 cm fromapproximately 30 cm fromtip of catheter.tip of catheter. also known as CVP port (central venousalso known as CVP port (central venous

pressure) lies in the right atrium andpressure) lies in the right atrium and

measures CVP can be used for infusion of IVmeasures CVP can be used for infusion of IV

solutions or medicationssolutions or medications


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i f h hL i f h h


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Location of the catheterLocation of the catheter


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W f d i I i


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Waveform during InsertionWaveform during Insertion


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Length of InsertionLength of Insertion

Usual conditions (just for ease toUsual conditions (just for ease to

memorize)memorize)

35 cm: RV35 cm: RV 4545 cm: PAcm: PA

55 cm: wedge55 cm: wedge

But the actual length may varyBut the actual length may vary

greatly between patients!greatly between patients!

HemodynamicHemodynamic


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yMeasurements--Measurements--NormalNormal

RangeRange RA pressure: 2~6 mmHgRA pressure: 2~6 mmHg

RV pressure:RV pressure: systolic 15~25 mmHg;systolic 15~25 mmHg;

diastolic 0~4 mmHgdiastolic 0~4 mmHg PA pressure: systolic 15~25 mmHg;PA pressure: systolic 15~25 mmHg;

diastolic 8~16 mmHgdiastolic 8~16 mmHg

Mean PAP: 10~20 mmHgMean PAP: 10~20 mmHg

Pulmonary Capillary Wedge PressurePulmonary Capillary Wedge Pressure

(PCWP): 6~12 mmHg(PCWP): 6~12 mmHg

Derived HemodynamicDerived Hemodynamic


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ProfilesProfiles

Systemic Vascular ResistanceSystemic Vascular Resistance

(SVR): 80 x (MAP-CVP)/CO;(SVR): 80 x (MAP-CVP)/CO;

800~1200 dyne-sec-cm800~1200 dyne-sec-cm-5-5

Pulmonary Vascular ResistancePulmonary Vascular Resistance

(PVR): 80 x (PAP-PCWP)/CO;(PVR): 80 x (PAP-PCWP)/CO;20~130 dyne-sec-cm20~130 dyne-sec-cm-5-5



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ProfilesProfiles

Cardiac Output: thermodilutionCardiac Output: thermodilution

method; 4~8 L/minmethod; 4~8 L/min

Cardiac Index: CO/BSA; 2.5~4.2Cardiac Index: CO/BSA; 2.5~4.2L/min/mL/min/m22

Continuous CardiacContinuous Cardiac


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Continuous CardiacContinuous Cardiac

OutputOutput

Continuous Cardiac Output (CCO)Continuous Cardiac Output (CCO)

measurement can be achieved bymeasurement can be achieved by

a electric coil attached on the tipa electric coil attached on the tipof PA catheter. It automaticallyof PA catheter. It automatically

measures CO every 3 min.measures CO every 3 min.

Mixed Venous OxygenMixed Venous Oxygen


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Mixed Venous OxygenMixed Venous Oxygen

Saturation (SvOSaturation (SvO22))

Mixed by blood from both SVCMixed by blood from both SVC

and IVC, sampled at PAand IVC, sampled at PA

OO22 consumption= SaOconsumption= SaO22-SvO-SvO22SvOSvO22=SaO=SaO22 - (VO- (VO22/Q x Hb x 13)/Q x Hb x 13)


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Clinical monitoring ofClinical monitoring of


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ventilationventilation

Continuous observation should beContinuous observation should bemade of the following :made of the following :

1. patient's colour .1. patient's colour .

2. respiratory rate .2. respiratory rate .3. adequacy of chest movement .3. adequacy of chest movement .

4. movement of the reservoir bag or4. movement of the reservoir bag or

ventilator bellows .ventilator bellows .



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ventilationventilation Auscultation of both lung fields shouldAuscultation of both lung fields should

also be performed frequently in orderalso be performed frequently in order

to detect :to detect :

1. equality of air entry .1. equality of air entry .

2. intubation of a bronchus .2. intubation of a bronchus .

3. presence of secretions .3. presence of secretions .

4. occurrence of a pneumothorax .4. occurrence of a pneumothorax .



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ventilationventilation

Anaesthetist must check regularly for signs ofAnaesthetist must check regularly for signs of

respiratory obstruction as evidenced by:respiratory obstruction as evidenced by:

1. tracheal tug .1. tracheal tug .

2. paradoxical abdominal movement .2. paradoxical abdominal movement .

3. absence of bag deflation .3. absence of bag deflation .

Some ventilators make a regular noise duringSome ventilators make a regular noise during

part of the ventilating cycle and this is apart of the ventilating cycle and this is avaluable audible monitor.valuable audible monitor.

Measurement of airwayMeasurement of airway


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pressurepressure

Airway pressure may reflect changes in lung andAirway pressure may reflect changes in lung and

chest wall compliance :chest wall compliance :

Chest wall compliance may be influenced by :Chest wall compliance may be influenced by :

1. degree of muscle paralysis .1. degree of muscle paralysis .

2. surgical manipulation .2. surgical manipulation .

3. position of the patient .3. position of the patient .



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pressurepressure

Lung compliance may be influenced by :Lung compliance may be influenced by :

1. accumulation of secretions .1. accumulation of secretions .

2. development of a pneumothorax .2. development of a pneumothorax .

3. position of the patient .3. position of the patient .

Increased resistance to air flow caused byIncreased resistance to air flow caused by

bronchospasm or obstruction of the trachealbronchospasm or obstruction of the trachealtube is reflected by an increased peak airwaytube is reflected by an increased peak airway

pressure.pressure.



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pressurepressure

1.1. Kinking of ventilator tubing or tracheal tube.Kinking of ventilator tubing or tracheal tube.

2.2. Overinflation of the tracheal tube cuff withOverinflation of the tracheal tube cuff with

consequent obstruction of the lumen of the tube.consequent obstruction of the lumen of the tube.3.3. Increased secretions.Increased secretions.

4.4. Pneumothorax.Pneumothorax.

5.5. Bronchospasm.Bronchospasm.

6.6. Inadequate muscle relaxation.Inadequate muscle relaxation.

ses of elevation of airway pressure


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Disconnection alarmDisconnection alarm

When the lungs are ventilated mechanically, theWhen the lungs are ventilated mechanically, the

continuity of the anaesthetic breathing system,continuity of the anaesthetic breathing system,

and thus of gas delivery to the patient, should beand thus of gas delivery to the patient, should be

monitored using a disconnection alarmmonitored using a disconnection alarm The alarm is activated if the airway pressureThe alarm is activated if the airway pressure

decreases below a preset minimum for a presetdecreases below a preset minimum for a preset

time interval.time interval.


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Disconnection alarmDisconnection alarm

A large leak, or total disconnection, is indicated ifA large leak, or total disconnection, is indicated ifthe alarm is triggered.the alarm is triggered.

In addition, most of these devices sound an alarmIn addition, most of these devices sound an alarm

if excessive airway pressures are generated.if excessive airway pressures are generated.

A disconnection alarm does not obviate the needA disconnection alarm does not obviate the need

for visual surveillance of the continuity of thefor visual surveillance of the continuity of the

breathing system.breathing system.

End-tidal carbon dioxideEnd-tidal carbon dioxide


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End tidal carbon dioxideEnd tidal carbon dioxide

tension (PE'cotension (PE'co22)) PE'coPE'co

22

, correlates well with Paco, correlates well with Paco22

, in patients who, in patients who

have no significant pulmonary disease.have no significant pulmonary disease.

Normal PacoNormal Paco22-PE'co-PE'co22 gradient is approximatelygradient is approximately

5mmHg. (Paco5mmHg. (Paco22 35-45mmHg, PE'co35-45mmHg, PE'co22 30-40mmHg.)30-40mmHg.)

End-tidal carbon dioxide concentration may beEnd-tidal carbon dioxide concentration may be

measured using the principle of infrared absorptionmeasured using the principle of infrared absorption

spectrophotometry.spectrophotometry.

PPETETCOCO

22



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tension (PE'cotension (PE'co22))

PE'coPE'co22 is useful particularly in the followingis useful particularly in the followingcircumstances.circumstances.

b.b. To provide evidence of correct placement of theTo provide evidence of correct placement of the

tracheal tube. Capnography is the only methodtracheal tube. Capnography is the only method

available which provides rapid and reliableavailable which provides rapid and reliablediagnosis of intubation of the oesophagus.diagnosis of intubation of the oesophagus.

c.c. For routine monitoring of the adequacy ofFor routine monitoring of the adequacy of

ventilation and the effects of IPPV.ventilation and the effects of IPPV.

d.d. To detect rebreathing.To detect rebreathing.

PPETETCOCO

22



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tension (PE'cotension (PE'co22))

To detect air, fat or pulmonary embolism; a suddenTo detect air, fat or pulmonary embolism; a suddendecrease in PE'codecrease in PE'co22 occurs as a result of increasedoccurs as a result of increased

dead spacedead space

n To detect malignant hyperthermia; a progressiveTo detect malignant hyperthermia; a progressive

increase in PE'coincrease in PE'co22, results from increased muscle, results from increased musclemetabolism.metabolism.

n To ensure normocapnia in elderly patients in anTo ensure normocapnia in elderly patients in an

attempt to maintain adequate cerebral perfusion.attempt to maintain adequate cerebral perfusion.

n To maintain normal PE'coTo maintain normal PE'co22 during carotid arteryduring carotid artery

surgery in order to maintain cerebral perfusion.surgery in order to maintain cerebral perfusion.

PPETETCOCO

22


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7-5 a Normal CO2 waveform

b CO2 drop to zero Disconnection

c CO2 decrease gradually

hyperventilation

d CO increase raduall h oventilation


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PARTPART

OTHER SYSTEMOTHER SYSTEM

Measurement ofMeasurement of


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easu e e o

TemperatureTemperature General anaesthesia inhibits the patientsGeneral anaesthesia inhibits the patients

ability to maintain body temperature byability to maintain body temperature by

depressing the thermoregulatory centre indepressing the thermoregulatory centre in

the hypothalamusthe hypothalamus

Heat loss during anaesthesia is potentiatedHeat loss during anaesthesia is potentiated

by surgery of long duration and exposure oby surgery of long duration and exposure of

large surface areas of tissue, e.g. thelarge surface areas of tissue, e.g. the

abdominal contents during gastrointestinalabdominal contents during gastrointestinal

operations.operations.



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TemperatureTemperature The use of wet packs and dry inspiredThe use of wet packs and dry inspired

gases compounds the problem.gases compounds the problem.

These sources of heat loss assume These sources of heat loss assume

even more importance in children,even more importance in children,

especially small babies, whose surfaceespecially small babies, whose surface

area is much larger in proportion toarea is much larger in proportion to

body weight than in the adult.body weight than in the adult.



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TemperatureTemperature

1. The operating room temperature should be as high1. The operating room temperature should be as high

as is comfortable for the theater staff.as is comfortable for the theater staff.

2. A warming mattress should be placed beneath the2. A warming mattress should be placed beneath the

patient.patient.3. Exposed surfaces should be swaddled with warm3. Exposed surfaces should be swaddled with warm

gauze or foil, especially in neonates.gauze or foil, especially in neonates.

4. All i.v. infusion fluids should be warmed.4. All i.v. infusion fluids should be warmed.

5. Inspired gases should be warmed and humidified.5. Inspired gases should be warmed and humidified.

easurement to minimize heat loss



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TemperatureTemperature

1. The nasopharynx (approximates to brain1. The nasopharynx (approximates to brain

temperature)temperature)

2. The oesophagus (approximates to cardiac2. The oesophagus (approximates to cardiac

temperature).temperature).

3. The tympanic membrane (best for core3. The tympanic membrane (best for core

temperature, but the membrane is delicate andtemperature, but the membrane is delicate and

easily damaged)easily damaged)

4. The rectum.4. The rectum.

The probe may be placed in thefollowing positions in order to measurecore temperature:

8-monitoring during anesthesia

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