Curs 2012 Monitoring in Anesthesia.ppt

8/10/2019 Curs 2012 Monitoring in Anesthesia.ppt

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Monitoring in Anaesthesia

and Intensive Care

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Monitoring: A Definition ... interpret available clinical data to help

recognize present or future mishaps orunfavorable system conditions

... not restricted to anesthesia(change clinical data above to system data to apply to

aircraft and nuclear power plants )


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What is monitoring?

Physiologic parameter & Patient safety parameter

Clinical skills & Monitoring equipment

Data collection, interpretation, evaluation, decision

Problem seeking, Severity assessment, Therapeuticassessment, Evaluation of Anesthetic interventions


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Patient Monitoring and Management

Involves Things you measure (physiological measurement, such as

BP or HR)

Things you observe (e.g. observation of pupils) Planning to avoid trouble (e.g. planning induction of

anesthesia or planning extubation)

Inferring diagnoses (e.g. unilateral air entry may meanendobronchial intubation)

Planning to get out of trouble (e.g. differential diagnosis

and response algorithm formulation)


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Level of monitoring Routine / Specialize / Extensive

Non-equipment / Non-invasive / Minimally invasive

/ Penetrating / Invasive / Highly invasive

Systematic Respiratory / Cardiovascular / Temperature/Fetal Neurological / Neuro-muscular / Volume status & Renal

Standards for basic intraoperative monitoring ( ASA)


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Standards for basic intraoperative monitoring

( ASA :American Society of Anesthesiologists)

Standard I Qualified anesthesia personnel shall be present in the

room throughout the conduct of all GA, RA, MAC

Standard II During all anesthetics, the patients respiratory

(ventilation, oxygenation), circulation and temperature

shall be continually evaluated


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Monitoring in AnesthesiaOBJECTIVES:1. Guidelines to the practice of anesthesia and patient monitoring

2. Elements to monitor(Anesthesia depth, Oxygenation, Ventilation, Circulation, Temperature)2.1. ECG2.2. Pulse Oximetry ( Function, Values, Limitations)2.3. Blood Pressure (methods, indications, limitations, Insertion sites, values)2.4. central venous line and pressure (methods, indications, limitations,

Insertion sites and it's advantages, Complications, values)

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Monitoring in AnesthesiaOBJECTIVES:2.5. Capnography and EtCO2 (Uses, Measurement, values, factorsaffecting EtCO2)

2.6. Cyanosis2.7. The oxyhemoglobin dissociation curve (interpretation, causes ofLeft and right shifting , key values, O2-Content of Blood)2.8. Temperature ( Methods, Values, sites)

3. Normal values for a healthy adult undergoing anesthesia

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Guidelines to the practice of anesthesia and patient monitoring:

Monitoring in the Past

1. Visual monitoring ofrespiration and overallclinical appearance

2. Finger on pulse

3. Blood pressure10


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Monitoring in the Past

Finger on the pulse


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Harvey Cushing Not just a famous neurosurgeon but the father of anesthesia monitoring

Invented and popularized the anesthetic chart

Recorded both BP and HR

Emphasized the relationship between vital signs andneurosurgical events ( increased intracranial pressure leads to hypertension and bradycardia )


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Guidelines to the practice of anesthesia and patient monitoring:

1. Qualified anesthesia personnel shall be present inthe room throughout the conduct of :

- all general anesthetics- regional anesthetics- monitored anesthesia care

2. A completed pre-anesthetic checklist . (history, physical exam, lab investigations, NPO policy)

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Guidelines to the practice of anesthesia and patientmonitoring: 3. An anesthetic record.

- in general anaesthesia, regional anesthesia, or monitored IVconscious sedation H R and BP shoul d be measured every 5min.

- also time, dose and route of drugs and fluids should be charted

4. During all anesthetics , the patients

- oxygenation- ventilation- circulation shal l be continously evaluated !- temperature

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MONITORING

BP

MAP

Temp

RR

O2 sat

HR

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Elements to Monitor :

Patients with local or regional anesthesia provide verbalfeedback regarding well being.

Onset of general anesthesia signaled by lack of response toverbal commands, in addition to loss of blink reflex to lighttouch.

Inadequate anesthesia can be signaled by : Facial grimacingor movement of arm or leg. But with muscle relaxants ( fully

paralysis), it can be signaled by : Hypertension, tachycardia,

tearing or sweating. Excessive anesthesia can be signaled by :

Cardiac depression, bradycardia, and Hypotension.And also may result in hypoventilation, hypercapnia andhypoxemia when muscle relaxants is not given.

I. Anesthetic Depth:

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Clinically, monitored by patient color ( with adequateillumination ) and pulse oximetry .

Quantitavely monitored by using oxygen analyzer, equippedwith an audible low oxygen concentration alarm.

III. Temperature Continuous temperature measurements monitoring is

mandatory if changes in temperature are anticipated orsuspected.

II. Oxygenation :

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Clinically, monitored by pulse palpation, heart auscultationand monitoring intra-arterial pressure or oximetry.

Quantitavely using ECG signals and arterial blood pressuremeasurements every 5 min.

V. Ventilation Clinically, monitored through a correctly positioned

endotracheal tube, also observing chest excursions, reservoir bag displacement, and breath sounds over both lungs.

Quantitavely by ETCO2 analysis , equipped with an audibledisconnection alarm.

Arterial blood gas analysis for assessing both oxygen andventilation.

IV. Circulation :

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Monitoring: Electrocardiogram ECG:

A 3 or 5 lead electrode system is used for ECG monitoring in the OR.

The 3 lead system has electrodes positioned on the right arm, left arm and chestposition. ( placed in the left anterior axillary line at the 5 th interspace, referred

to as V5 ). Lead II is usually monitored by this system.

The 5 lead system adds a right leg and left leg electrodes, which allowsmonitoring v1, v2, v3, AVR, AVL, AVF and V5.

II and V5 very important !

ST segment

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Monitoring: Electrocardiogram ECG:

Identification of P waves in lead II and its association with the QRScomplex is useful in distinguishing a sinus rhythm from otherrhythms.

Analysis of ST segment is used as an indicator of MI. ( Dep.-ischemia/ elev.-infarction )

Over 85% of ischemic events can be detected by monitoring ST seg.of leads II and V5.

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Monitoring: Pulse Oximetry:

Allows beat to beat analysis of oxygenation.

Depends on differences in light absorption between oxyHb anddeoxyHb.

Red and Infra-red light frequencies transmitted through atranslucent portion. (finger-tip or earlobe)

Microprocessors then analyze amount of light absorbed by the 2wavelengths, comparing measured values, then determining

concentrations of oxygenated and deoxygenated forms. (oxy- anddeoxy-) 21


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PULSEOXIMETRY is for OXYGENATION

Principle : Spectrophotometry & Plethysmography

relies on the differing absorption of light, at different wavelengths by the variousstates of oxyhaemoglobin

- HbO2 has a higher absorption at 940 nm (blue light)

- Hb has a higher absorption at 660 nm (red light)

the light signal following transmission throughthe tissues has a pulsatile component

-


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- two LEDs : one emitting red light (660 nm) and theother a blue light (940nm) on the finger nail

- on the other side of the finger : photo sensor (photocell) detects the transmitted light

- the LEDs are switched on and off at 30 Hz to detectthe cyclical changes in the signal due to pulsatilearterial blood flow

- by calculating the absorption at the twowavelengths the processor can compute the

proportion of haemoglobin which is oxygenated

Hb HbO

HbO p

C C

C OS

2

2

2


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Pulse oximeters measure:1. The oxygen saturation of haemoglobin in arterial blood- which i s a measure o f the average am ount o f o xygen b ound to each

haem oglob in m olecu le

- Haemoglobin is a compound of iron (haem) and globin chains.- Each globin chain is linked to one atom of iron, each of which can carry 4

molecules of oxygen , and as each molecule of oxygen contains two atoms ofoxygen (O2), each haemoglobin molecule can carry 8 atoms of oxygen .

This makes haemoglobin a very efficient means of oxygen transport: each gram ofhaemoglobin can carry 1.34ml of oxygen.

2. The pulse rate - in beats per minute, averaged over 5 to 20seconds.


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A pulse oximeter is affected by :

ambient light shivering

abnormal haemoglobins ( carboxyhaemoglobin, methaemoglobin, dyes as methylene blue and bilirubin )

pulse rate and rhythm

vasoconstriction poor tissue perfusion ( shock, low CO, cold extremities )

NOT affected by : dark skin or anaemia.


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A pu lse oxim eter g ives no in formation abo ut :

The oxygen content of the blood The amount of oxygen dissolved in the blood

The respiratory rate or tidal volume i.e . ventilation The cardiac output or blood pressure ?


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Monitoring: Blood Pressure BP :

o Methods of BP measurement:

1. Simplest method of BP measurement,estimating the SBP, is by palpating the returnof arterial pulse as cuff is deflated (Riva-Rocci).

2.auscultation of the Kortokoff sounds on deflation

(providing both SBP and DBP)Mean Arterial PressureMAP = DBP + 1/3(SBP DBP)MAP = ( SBP + 2 DBP ) / 3

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MEASUREMENT OF ARTERIAL PRESSURE

INDIRECT measurement (non-invasive)- signals generated by the occlusion of a major artery using a cuff

- gives not continous but intermittent measurements

- palpation method ( Riva Rocci)- auscultation of the Korotkoff sounds

- osccilometry method

DIRECT measurement (invasive and continous)

di h d f (1)


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o Indirect Methods of BP measurement (1)

1. Riva Rocci: simplest method of BP measurement, estimating onlythe SBP, is by palpating the return of arterial pulse as cuff isdeflated.

2. Auscultation of the Korotkoff sounds (1905)on deflation created by the turbulent blood flow in the artery

(providing both SBP and DBP)Mean Arterial Pressure (MAP) = DBP + 1/3(SBP DBP)


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Indirect Methods of BP measurement (2)

3. OSCCILOMETRY - a microprocessor controlled oscillometer. DINAMAP- a pressur e tr ansducer that digital izes signal s ( microprocesor).- rapid, accurate ( 9 mmHg) measurements of SBP, DBP, MAP and HR

- SAP corresponds to the onset of rapidly increasing oscillations- MAP corresponds to the maximal oscillation at the lowest cuff pressure- DAP corresponds to the onset of rapidly decreasing oscillations

LIMITATIONS:

- tendency to overestimate at low pressures and underestimate at high pressures - errors : movements, arrhythmias or BP fluctuations- compressive peripheral nerve injuries (repeated measurements )


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Cuff Size

Too small cuff will result in false high blood pressure reading

Too large cuff will result in false low blood pressure reading

f rom

Ba


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DIRECT Measurement of the BP invasive : catheter into the artery

METHODS

1. open Liquid column method (obsolete) , measures only MAP13.4 cm. H2O = 10 mm.Hg.

2. Liquid manometers (obsolete)

3. Electromechanical transducers :- conversion of mechanic signal into an electric signal

- and then electronically converted and displayed as :

SAP,DAP and MAP .


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Electromechanical - TRANSDUCERS

The diaphragm :- is moved by arterial pulsations which push the saline column

- should be thin, small and rigid !

Transducers :

- based upon strain gauge principle : stretching (by PRESSURE ) a wire orsilicone crystal changes its electrical resistance

- connected to a wheatstone bridge circuit : so that the voltage output is proportionate to the pressure applied it


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The 3 major problems may occur :

1. Improper zeroing and zero drift

2. Improper transducer / monitor calibration

3. Inadequate dynamic response of system : RF and damping

Resonant (natural) Frequency (RF) = frequency at which a system oscillates whenstimulated.

- if the frequency of an input signal (i.e., pressure waveform) approaches the RF of asystem : progressive amplification of the output signal occurs,

a phenomenon known as ringing.

Th ARTERIAL PRESSURE W f


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The ARTERIAL PRESSURE Waveform

ARTERIAL WAVEFORM isa complex sine-wave The fundamental frequency (FF) or the 1-st harmonic is equal to the HR

( ex: for HR 60 b/min = 1 beat / sec = 1 cycle/sec = 1Hz.) physiologic peripheral arterial waveforms have a FF = 3 to 5 Hz

MONITORING SYSTEM The RF should be at least at least 5 times higher than the highest frequency in the

input signal or better : approx.10 times the FF

at least FR >20 Hz to avoid ringing and systolic overshoot


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The ARTERIAL PRESSURE Waveform

The damping coefficient (DC) is a measure of how quickly an oscillating systemcomes to rest

method to test the DC: the fast-flush test ( square wave test) optimal damping

- underdamping = overestimates SAP and underestimates DAP

- overdamping = underestimates SAP and overestimates DAP

- both cases however MAP is relatively accurate


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REDUCING ARTIFACTS IN A-LINES

Lines free of kinks and clots

Air Bubbles : small amount may augment systolic pressure reading, while largeamount cause an over-damped system

One stopcock per line

Heparinized saline flushed maintaining patency

Transducer should be electronically balanced or re-zeroed because the zeropoint may drift if the room temperature changes

to have an adequate damping = flushing TEST

Short and rigid : catheter and lines


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Monitoring: Blood Pressure BP:


3. Automated non-invasive BP measurements.METHODOLOGY: a microprocessor controlled oscillometer

(Dinamap) which is used routinely intraoperatively. It

allows automatic inflation of the BP cuff at preset timeintervals, sending readings into a pressure transducer thatdigitalizes them. This technique gives rapid, accurate ( 9mmHg) measurements of SBP, DBP, MAP and HR several

times a minute. LIMITATIONS: Errors occur due tomovements, arrhythmias or BP fluctuations due torespiration. 3 5 minutes intervals is recommended to

prevent compressive peripheral nerve injury due to repeatedrapid measurements.

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Monitoring: Blood Pressure BP:


4. Invasive BP measurements.(Arterial BP):

Indications: Rapid moment to moment BP changes Frequent blood sampling Major surgeries (cardiac, thoracic, vascular) Circulatory therapies: vasoactive drugs, deliberate

hypotension Failure of indirect BP: burns, morbid obesity Sever metabolic abnormalities Major traumaThe radial artery at the wrist is the most

common site for an arterial catheter.Alternatives are femoral, brachial anddorsalis pedis. 39


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Central Venous line and Pressure (CVP)

Catheter inserted into the SVC providing an estimate ofthe right atrial and ventricular pressures .

Serial CVP measurements are more useful than a singlevalue in order to assess blood volume, venous tone andright ventricular performance. HR, BP and CVPresponse to a volume infusion (100 500 ml) is also auseful test of right ventricular performance.

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Central Venous line and Pressure (CVP)

Indications: CVP monitoring provides Right Atrial and RightVentricle pressures

Advanced Cardiopulmonary disease + major

operation

Secure vascular access for drugs

Secure access for fluids + traumatic pts

Aspiration of entrained air: sitting craniotomies

Inadequate peripheral IV access41


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Central Venous Line:PERFORMANCE of Right Internal Jugular Vein

Internal jugular (Int. Jug.) vein lies in groovebetween sternal and clavicular heads ofsternocleidomastoid muscle

It is lateral and slightly anterior to carotid artery

Aseptic technique, head down

Insert needle towards ipsilateral nipple

Seldinger method: 22 G finder; 18 G needle,guide-wire, scalpel blade, dilator and catheter

Observe ECG and maintain control of guide-wire

Ultrasound guidance; Chest-Xray post insertion. 42


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Advantages of Right Int. Jug. vein

Consistent, predictable anatomic location Readily identifiable landmarks

Short straight course to Superior Vena Cava Easy access for anesthesiologist at patientshead

High success rate, 90-99%

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Complications of Central lines (jugular):

Bleeding Injury to surrounding

structures as carotid artery Pneumothorax Arrhythmia

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Central Venous line Alternative Sites Subclavian vein:

Easier to insert versus Int. Jug. vein Better patient comfort v. Int. Jug. Higher Risk of pneumothorax- 2%

External jugular: Easy to cannulate if visible. no risk of pneumothoroax, high risk or bleeding 20%: cannot access central circulation

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Central Venous Pressure (CVP )Monitoring

Reflects pressure at junction of vena cava + RA CVP is driving force for filling RA + RV CVP provides estimate of:

Intravascular blood volume RV preload

Trends in CVP are very useful Measure at end-expiration Central Venous Pressure (CVP): 1-10 mmHg

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SWAN GANZ = PA CATHETER


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SWAN-GANZ catheterWaveform during Insertion


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PA CATHETER


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PA CATHETER Zone III allows for

uninterrupted bloodflow and a continuouscommunication withdistal intracardiacpressures. (PAand PVexceed Palv)


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PAC Th dil ti


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PAC-Thermodilution

The change of the blood s temperature in is measured in the pulmonary arteryusing the PAC thermistor

The thermistor records the temperature change and the monitor electronicallydisplays a temperature/time curve.

The CO is inversely proportional to :- the temperature change- the area under the curve

( PAC measures the Pulm.CO = Global CO if no intracardiac shunt )

C h d E CO2


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Capnography and EtCO2

Capnometry : is the numerical measurement of CO 2 concentrationduring inspiration and expiration.

Capnogram : refers to the continuous display of the CO 2concentration waveform sampled from the patients airway duringventilation.

Capnography : is the continuous monitoring of a patientscapnogram. 53

C h d E CO2


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Capnography and EtCO2 End-tidal CO 2 monitoring is standard for all patients undergoing

GA with mechanical ventilation.

It is an important safety monitor and a valuable monitor of the patients physiologic status, and it has been an important factor in reducinganesthesia-related mortality and morbidity.

CO 2 monitoring is considered the best method for verifying successfulintubation and extubation procedures .

It helps in assessment of the adequacy of ventilation and an indirect

estimate of PaCO 2.

Also it aids in diagnosis of PE, recognition of a partial airway obstruction,and indirect measurement of airway reactivity (bronchospasm).

ETCO 2 levels have also been used to predict outcome of resuscitation.

C h d E CO2


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Capnography and EtCO2 Measurement of ETCO2 Sampling the patients respiratory gases near the airway . Using infra-red gas analysis or mass spectrometry on the values and

concentrations obtained.

Provided that when sampling, inspired CO 2 value should be nearzero. (i.e. ETCO 2 value is a function of CO 2 production, alveolarventilation and pulmonary circulation; excluding inspired CO 2).

During general anesthesia, with absence of ventilation perfusion

abnormalities, difference between PaCO 2 and ETCO 2 is about 5 mmHg (PaCO2 = 40 mmHg, ETCO2 = 35 mmHg)

Increases or decreases in ETCO2 values maybe the result of

increases or decreases in production and elimination .


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Normal

Esophageal 0 ! > 4 curves !

Cardiac arrest bronhospasm

Curare cleft spontaneous


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exhausted CO2 absorber

IMV

Expiratory Valve

Inspiratory valve

Hyper and hypo VENTILATION

Cyanosis


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Cyanosis Defined as the presence of 5 g./dL of deoxygenated

hemoglobin (deoxy Hb). i.e. Hb level = 15 g/dL, 5 g/dL release O 2 which leaves 10 g/dL of

oxyhemoglobin

SaO 2 = OxyHb / (OxyHb + DeoxyHb) = 10 / (10 + 5) = 66%

SaO 2 of 66% corresponds to PaO 2 of 35mmHg.

In anemic patients the oxygen tension at which cyanosis isdetectable will be even lower.

i.e. Hb level = 10 gm/dL, 5 gm/dL release O 2 SaO 2 = OxyHb / (oxyHb + DeoxyHb) = 5 / (5 + 5) = 50%

SaO 2 of 50% corresponds to PaO 2 of only 27 mmHg.

Th h l bi di i ti


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The oxyhemoglobin dissociation curve

It is a sigmoid curve that describes the relationship betweenoxygen tension (PaO 2) and binding (SpO 2).

When PaO 2 is low, the hemoglobin affinity to oxygen fallsrapidly , explaining the sharp sloping .(PaO 2< 60 mmHg)

The oxyhemoglobin dissociation curve


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The oxyhemoglobin dissociation curve A decrease in PaO 2 of less than 60 mmHg (corresponding to SpO 2

90 %) results in a rapid fall in the oxygenation saturation.

The lowest acceptable O 2 saturation level is 90%.Left And Right Shifts of the

Oxyhemoglobin Dissociation CurveRight Left

Decreased affinity of Hb for O 2. Increased affinity of Hb for O 2.

Causes: Inc. PCO 2 Hyperthermia

Acidosis Increased altitude Increased 2,3-DPG Sickle Cell Anemia Inhalational anesthetics

Causes: Dec. PCO 2 Hypothermia

Alkalosis Fetal hemoglobin Decreased 2,3-DPG Carboxyhemoglobin Methemoglobin

Th h l bi di i ti


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The oxyhemoglobin dissociation curve Key Values:a. At PO

2 100 mmHg, Hb 100% saturation .

b. At PO 2 40 mmHg, Hb 75% saturation.c. At PO 2 27 mmHg, Hb 50% saturation.

Oxygen content of blood: is the total amount of O 2 carried in blood, including bound and

dissolved O 2.O2 content = (O 2-binding capacity * % saturation) + O 2 dissolved

O2-binding capacity = maximal amount of O 2 bound to Hb at 100 % sat.

The dissolved O 2 isnt measured by oximetry but by blood gasanalysis.


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Monitoring Temperature

Objectiveaid in maintaining appropriate body temperature

Applicationreadily available method to continuously monitortemperature if changes are intended, anticipated orsuspected

Methodsthermostattemperature sensitive chemical reactions


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Potential heat loss or risk of hyperthermianecessitates continuous temperaturemonitoring

Normal heat loss during anesthesia averages0.5 - 1 C per hour, but usually not more that 2 -3 C

Temperature below 34C may lead tosignificant morbidity


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Hypothermia develops when thermoregulationfails to control balance of metabolic heat

production and environment heat loss Normal response to heat loss is impaired

during anesthesia Those at high risk are elderly, burn patients

neonates, spinal cord injuries


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Hyperthermia Causes Malignant hyperthermia Endogenous pyroxenes (IL1) Excessive environmental warming Increases in metabolic rate secondary to:

Thyrotoxicosis Pheochromocytoma


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Monitoring Sites Tympanic

Esophagus Rectum Nasopharynx

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Normal values for a healthy adult undergoing


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y g ganesthesia

Systolic Blood Pressure Diastolic Blood Pressure Heart Rate Respiratory Rate Oxygen sat. by oximetry End Tidal Carbon Dioxide tension Skin appearance Color Temperature Urine Production

SBPDBPHRRRSpO2ETCO2

85 16050 9550 1008 2095 10033 45warm, drypink36 37.5>= 0.5

mmHgmmHgbpmrpm%mmHg

O Cml.kg -1.min -1

Central Venous Pressure Pulmonary Artery Pressure Pulmonary Capillary Wedge Pressure Mixed venous oxygen saturation Cardiac OutputMean Arterial Pressure

*MAP = DBP + 1/3 ( SBP DBP )

CVPPAP (mean)PCWPSvO2COMAP

1 1010 205 15754.5 680 120

mmHgmmHgmmHg%1.Min -1

mmHg

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THANKYOU69

Clinical measurement


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Clinical measurement is limited by 4 major constraints:

1. Feasibility

2. Reliability

3. Interpretation

4. Value

4 mandatory steps in clinical measurement:


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4 mandatory steps in clinical measurement:

Detection : sensing device ( biological signal : mechanical, electrical, electromagnetichemical or thermal energy)

Transduction : the output is converted into another form, usually to a

continuous electrical signal

Amplification and signal processing : - extract and magnify the relevant features of the signal and reduce unwanted noise

Display and Storage : the output of the instrument is presented to the operator

Mechanical versus Digital instruments


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Mechanical versus Digital instruments

Mechanical instruments ;

- use the natural signal energy to drive a display,with minimal intermediateprocessing

Digital instruments

- non-electrical signals are converted by a transducer to an electrical signal suitablefor electronic processing by digital computers.

- higher accuracy and precision

Essential requiremets for CLINICAL MEASUREMENT


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q

Accuracy is the difference between the measurements and the real biological

signal , or in practice, between a certain techique and a superior 'gold standardtechnique.

Precision describes the reproducibility of repeated measurements of the samebiological signal.

- calibration is important( against predetermined signals or for absolute measurements to zero)

MECHANICAL SIGNALS:


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MEASUREMENT OF ARTERIAL PRESSURE

a wide range of instruments are used to measure pressure :

liquid column manometers : height, zero point, fluid density

mechanical pressure gauges : aneroid manometer

diafragm gauges (coupled to transducers)


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Potential Methods To Measure Cardiac Output

Fick metdod Indicator dilution Pulse waveform ( pulse contour) methods ULTRASOUNDS ( 2D-Echo and Doppler techique) Bioimpedance

ANGIOGRAPHY MRI


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Ideal Cardiac Output Monitoring Technique

Precise and No bias Non-invasive Continous and instantaneous Automatic Operator independent Cheap Easy available in the ICU Leads to treatment changes / improvement in outcome

IT DOES NOT EXIST !

Use the Best Compromise : feasibility precision patient !

The FICK principle


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defines flow by the ratio of the uptake or clearance of a tracer within an organ tothe arterio-venous difference in concentration

CO = VO2 / [CaO2 CvO2])*100

V O2 per minute using a spirometer + Douglas bag CvO2 is taken from the pulmonary artery CaO2 a cannula in a peripheral artery

The FICK method


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considered to be the most accurate method for CO

but : - invasive, time consuming- accurate VO2 samples are difficult to acquire

discontinous CO : Deltatrac (Datex)

continous CO : possible, but no integrated system available

modified Fick equation : continous CO by NICO2 apparatus

INDICATOR DILUTION


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INDICATOR DILUTION

Chemical indicator dilution (dye)

Thermal indicator dilution

( Thermodilution )

the widest used : PAC = Swan Ganz

INDICATOR DILUTION
http://illuminations.nctm.org/imath/912/cardiac/student/images/catheterbig.jpg


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CO measurement by indicator dilution has 3 phases :

(a) an indicator is brought into the circulation (injection)

(b) the indicator mixes with the bloodstream(mixing and dilution)

(c) the concentration of the indicator is measured downstream(detection).

Chemical indicator dilution


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Chemical indicator dilution The Stewart-Hamilton formula (time-concentration curve)

using indocyanine green as indicator was the conventional indicator dilutionmethod used to measure CO in ICU until the 1970s.

Indocyanine green :- nontoxic, inert, safe- short half-life,- not affected by arterial saturation

The Thermodilution (TD) method


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The Thermodilution (TD) method

Thermodilution = indicator is the change in blood temperature

An injectate of known volume and temperature is injected into the right

atrium and the cooled blood traverses a thermistor in a major vessel branchdownstream over a duration of time.

TD Methods :

1. PULMONARY Thermodilution (P-TD)

1. TRANSPULMONARY Thermodiution (TP-TD)

The CLINICAL STANDARD is the PAC !


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Pulmonary -TD

PAC-Thermodilution


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The change of the blood s temperature in is measured in the pulmonary arteryusing the PAC thermistor

The thermistor records the temperature change and the monitor electronicallydisplays a temperature/time curve.

The CO is inversely proportional to :- the temperature change- the area under the curve

( PAC measures the Pulm.CO = Global CO if no intracardiac shunt )


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Sources of measurement error for P-TD

Loss of indicator Variation of injectate temperature and volume Recirculation - IC shunts : false high CO values Tricuspid regurgitation : false low CO values Fluctuations in baseline temperature

...........................


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10 ml. cold optimal < 4 sec. > 4-5 sec. false low CO! at least 3 measurements and less than < 10 % between them

Advantages of P-TD


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Advantages of P TD The standard method for clinical CO measurement

Simple and Repeated measurements possible.

The modified PAC may provide CCO- thermal indicator : intermitent heating of a resistace- 44C for 1-4 sec each 30-60 sec

- Not really continous : mean of 3-4 min ! - expensive

The PAC provides, in addition, PA pressures, PAOP, SvO2, and optionally,RVEF and RVEDV.

PULMONARY Thermodilution TRANSPULMONARY Thermodiution


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PULMONARY Thermodilution TRANSPULMONARY Thermodiution

The pulmonary artery TD curve appears earlier and has a higher peak temperature thanthe femoral artery TD curve.

TP-TD is less invasive than P-TD, but does NOT give : SvO2 an PAP values !

,

The Clinical USE of TP-TD


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The Clinical USE of TP-TD

Mainly : as a calibration method for othersystems : PiCCO, LiDCO-Pulse CO

PiCCO and LiDCO-Pulse CO are able after the initial calibration, tomeasure in a continous manner

( beat by beat ) the C.O, using :

the Pulse Contour method

The Pulse Contour method


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1. CALIBRATED techniquesPiCCO

LiDCO Pulse CO

2. NON-CALIBRATED techniques

Flow-Track VIGILEONexfin

CCO by the pulse contour method


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y p

The area under the systolic part of the AP waveform correlates :

- directly with Left Ventricular STROKE VOLUME- inversely with aortic impedance

For calibrated techiques : the Aortic impedance is estimated from AP and CO pre-measured values

( calibration : CO is ussualy measured by TP-TD)

SV

PiCCO


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Continous pulse contour analysis with intermittent TP-TD calibration.

Enables continuous hemodynamic monitoring using:- femoral or axillary artery catheter

- central venous catheter

LiDCO Pulse CO


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the independent calibration technique is : Lithium indicator Dilution

safe and minimally invasive : peripheral venous and arterial catheters

The PulseCO algorithm used by LiDCO is based on pulse power derivation.

Continuous, real-time cardiovascular monitoring


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BIOIMPEDANCE


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bio tissues (bone, muscle,blood, etc) have different electric proprieties blood is the most conductive tissue ( Na+ and Cl-)

pulsatile modification of ITBV TB TB ~ stroke volume

SV = K x (dZ / dt) / Zo x TEV

TB is measured by : producing and transmiting electricity ( high = 70 kHz low A = 2,5 mA ) betwwen 2 pairs of electrodes

E h di g h f i g th CO


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Echocardiography for measuring the CO

2 D method

Doppler - method

Ultrasounds (1.)


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US techniques can detect : the shape, size and movement of tissueinterfaces, especially soft tissues and blood (RBC)

US are defined by :- amplitude of oscillation (delta pressure : ambient to peak) dB- the wavelength (distance between successive peaks)

- frequency (inversely proportional to wavelength, nr. of cycles / second )

human ear can detect frequencies : 20-20,000 Hz. US have frequencies > 20,000 cycles /sec ( 20 KHz) diagnostic US uses frequencies in the range of 1-10 MHz.

Ultrasounds (2.)


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Transducers :- generate and sense US- are made from ceramic materials able to transform mechanical energy (pressure) to

electrical energy and vice versa ( the piezoelectric effect )

- Transducers : generates ultrasound of the same frequency as the applied voltage

Shorter wavelengths and higher frequencies improve the resolution of distance,but tissue penetration is simultaneously reduced.

Amplitude determines the intensity of the ultrasound beam and therefore thesensitivity of the instrument.

2-D Method


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Principle

Stroke volume= End diastolic volume End systolic volume

LV volumes estimated by Simpsons method, which is the summation ofthe volume of stacked cylinders within the LV at end-diastole and end-systole

150 ml - 52 ml= 98 ml


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Doppler Effect - 3


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pp Doppler effect represented by:

V = _ F . c _

2 F0 cos

Where V = velocity of objectF = frequency shiftc = speed of sound in medium (body tissue here)F0 = frequency of emitted sound

cos = angle between sound wave and flow (RBC)

cos 90 = 0 so the US beam should be parallel to RBC Maximum angle = 20

Doppler MethodPrinciple


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Flow (stroke volume)=Area x Velocity

CO=Stroke volume * Heart rateArea of left ventricular outflow tractObtain LVOT dimension in parasternal long axis view

Simplified formula = (2.1cm) 2 * 0.785

D=2.1 cm

3 46 cm 2

Flow Velocity at LVOT Pulsed wave Doppler at LVOT in apical5 chamber view

Velocity time integral 25 cm

25 cm = 87 cm 3X OESOPHAGEAL DOPPLER


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Measurement of blood flow velocity in the descending aorta atthe tip of the flexible probe

4 MHz continuous or 5 MHz pulsed wave

CO (cardiac output)SV (stroke volume)FTc (corrected f low time)PV (peak velocity)MD (minute distance)HR (heart rate)

THANKS for your attention !


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THANKS for your attention !

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Curs 2012 Monitoring in Anesthesia.ppt

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