Monitoring in Anesthesia Modified w

8/3/2019 Monitoring in Anesthesia Modified w

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MONITORING DURINGANESTHESIA

BY

DOCTOR NASRULLAH KHANMBBS FCPS


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INTRODUCTION

In modern anesthesia very potent drugs are beingused and awareness of patients about their care hasput the patient and anesthetist at risk of variouscomplications therefore monitoring has become anessential aspect of anesthesia care.

The effective monitoring reduces the potential forpoor outcomes that may follow anesthesia byidentifying derangements before they result inserious or irreversible injury.Electronic monitors also improve physician's ability

to respond because he or she is able to makerepetitive measurements at higher frequencies thanhumans and do not fatigue or become distracted.Monitoring devices potentially increase thespecificity and precision of clinical judgments.


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STANDARDS OFMONITORING

Two standards for basic anestheticmonitoring have been established by the

American Society of Anesthesiologists(ASA) in 1986 and reaffirmed on October25, 2005.

These standards have emphasized theevolution of technology ,practice, clinicaljudgment and experience .


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These standards apply to all anesthesia

care, (general anesthesia, regionalanesthesia and monitored anesthesiacare)

No anesthetic procedure should be startedwithout strictly observing these standardsprior to operation, except in emergency

circumstances, where appropriate lifesupport measures take precedence.


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STANDARD 1

Standard I requires qualified personnel to bepresent in the operating room during general

anesthesia, regional anesthesia, andmonitored anesthesia care to monitor thepatient continuously and modify anesthesiacare based on clinical observations and the

responses of the patient to dynamic changesresulting from surgery or drug therapy.


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STANDARD 2

Standard II focuses attention on continuallyevaluating the patient's oxygenation, ventilation,circulation, and temperature and specificallymandates to monitor the following

Pulse ,

Oxygen saturation (Pulse oximetry)

Blood Pressure (Non-invasive),

ECG,

EtCO2(Capnography)


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However in complicated cases more

extensive monitoring may be required.Blood pressure (Invasive),

Central venous pressure,

Cardiac outputPulmonary artery pressure.

Temperature.

Renal functionsMuscle relaxation

Depth of anesthesia


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1.PULSE OXIMETRY

Pulse oximetry is a technique whichmeasure pulse and oxygen saturation noninvasively. It combines the principles of

oximetry and plethysmography . A sensorcontaining light sources (two or three light-emitting diodes) and a light detector (aphotodiode) is placed across a finger, toe,earlobe, or any other perfused tissue thatcan be transilluminated.


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Oximetry depends on the observation that

oxygenated and reduced hemoglobin differin their absorption of red and infrared light(LambertBeer law).

Oxyhemoglobin (HbO2) absorbs moreinfrared light (960 nm), whereasdeoxyhemoglobin absorbs more red light

(660 nm) which is analyzed byspectrophotometry.


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Pulse oximeters are mandatory for almostall types of anesthetics including evenmoderate sedation.

These are particularly useful in childrenand in compromised patient having lung

disease or cardiac problems. The nature of the surgical procedure

(chest surgery) ,or special anesthetictechnique (e g, one-lung anesthesia) alsomake it very essential.


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ALTOUGH OXIMETRY HELPS IN FINDING

PROBLEMS WITH O2 SUPPLY ,CONDITION OFLUNGS, O2 CARRYING CAPACITY OF BLOOD AND

PERFUSION OF TISSUES but does not giveexact information about adequate

ventilation so that the severe hypercarbiacan develop without any alarm.

CarboxyHb ,Met Hb ,hypotension,

discoloration of nails, skin pigmentationand anemia can interfere with actualreading.


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2.CAPNOGRAPHY

Capnography is measurement of end-tidal CO2(ETCO2) which rely on the absorption of infraredlight by CO2.

As we know that CO2 is produced at cellularlevel when carbohydrates combine with O2 andthen is carried out by the blood to lungs ,fromwhere it is excreted by ventilation.

Therefore capnography gives not only theinformation about adequate ventilation but alsoabout all the mechanism involved in productionand excretion of CO2.


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The various pattern of capnography gives lot ofinformation about the different complication ofanesthesia or surgical procedure.

Although ,Ventilation can be monitored byobserving the rate of respiration, pattern of

breathing and auscultation of the breath soundsbut capnogrphy has no match.. A rapid fall ofETCO2 is a sensitive indicator of air embolism,which is a major complication of sitting

craniotomies.There is no contraindication.


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Examples of capnograph waves

A, Normal spontaneous breathing.

B, Normal mechanical ventilation.


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G, Exhausted CO2 absorbent produces aninhaled CO2 concentration greater thanzero.


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H, Double peak for a patient with a singlelung transplant.


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CAPNOGRAPHY VS OXIMETRY

OXYGEN

AIR ---------LUNGS------BLOOD------TISSUES(CELLS)DETECTED BY OXYGEN PROBE

CARBON DIOXIDE

TISSUE(CELL)------BLOOD------LUNGS------AIRWAYS(O2+CHO)

DETECTED BY CO2 SENSOR


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3.ELECTROCARDIOGRAPHY

Electrocardiography (ECG) should bestarted in all patients undergoing surgerybefore induction of anesthesia.

This gives lot of information about heartrate, rhythm, ischemic changes, andconduction defects in heart.

There is no contraindication.


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SOME COMMONECG TRACINGS

Sinus normal rhthym

Sinus tachycardia

Sinus bradycardia


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Atrial flutter

Atrial fibrillation

Ventricular tachycardia

PVCs


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Ventricular fibrillation

Ventricular asystole


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4.BLOOD PRESSURE

Non

invasive Blood Pressure MonitoringThe use of any anesthetic, no matter how"trivial," is an absolute indication for arterialblood pressure measurement. The techniquesand frequency of pressure determination dependon the patient's condition and the type ofsurgical procedure. An oscillometric blood

pressure measurement every 3

5 min isadequate in most cases.


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Invasive Blood Pressure Monitoring

Arterial-Line is Indicated for invasive arterialblood pressure monitoring for followingpurposes,

1. Induced hypotension,

2. Anticipation of wide blood pressure swings,3.End-organ disease necessitating precise

beat-to-beat blood pressure regulation, and

the need for multiple arterial blood gas

analyses.


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5.Central venous pressure

Central venous pressure is measured to see thestatus of body fluids and cardiac capability tomaintain circulation. The central venouscatheter is passed for monitoring of

1. Central venous pressure (CVP),

2. Administration of fluid to treat hypovolumia andshock,

3. Aspiration of air emboli, If these occur duringsurgery.

4. Gaining venous access in patients with poorperipheral veins.


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Contraindications

1. Renal cell tumor extending into the rightatrium

2. Fungating tricuspid valve vegetations.3. Receiving anticoagulants

4. who have had an ipsilateral carotidendarterectomy, because of thepossibility of unintentional carotid arterypuncture.


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6.Pulmonary arterycatheterization

Although the effectiveness of pulmonary arterycatheter (PAC) monitoring remains largely

unproven in many groups of surgical patients,the ASA concludes that the appropriateness ofPAC use depends on the combination of risksassociated with the patient, the operation, and

the setting ,therefore it is indicated in cardiacsurgery only.


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7.Temperature

Temperature of every patient undergoinggeneral anesthesia /spinal anesthesiashould be monitored except very brief

procedures (eg, less than 15 min).

Esophageal probe or skin probe can beused for this purpose.


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8.Urine output

Insertion of a urinary catheter is indicatedin patients with

1. congestive heart failure,

2. renal failure,3. advanced hepatic disease,

4. shock.

5. Prolonged surgery6. Spinal anesthesia


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Catheterization is routine in some surgicalprocedures such as

1. Cardiac surgery,

2. Aortic or renal vascular surgery, craniotomy,

major abdominal surgery, or procedures inwhich large fluid shifts are expected.

3. Requiring intra operative diuretic administration

4. Patients having difficulty in passing urine inrecovery room after general or regionalanesthesia.


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9.Peripheral nerve stimulator

Muscle are paralyzed during anesthesia forvarious surgical cases. Muscle relaxation isrequired to be monitored with help of nervestimulator because of the variation in patient

sensitivity to neuromuscular blocking agents,and the nature of surgery. Especially duringneurosurgery and eye surgery where accuratelevel of relaxation is mandatory all the timethroughout procedure.


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Nerve stimulator is also used in assessingparalysis during rapid-sequence induction

or during continuous infusions of short-actingmuscle relaxants .

To locate nerves to be blocked by regional

anesthesia.

To diagnose type and degree of muscle blockduring prolonged apnea


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10.Bi spectral index scale

Now a days awareness during anesthesia hasbecome a challenging problem for the anesthetistespecially in emergency cases when patient is notcompletely fit for anesthesia and therefore relativelylight anesthesia is indicated .In such situation it

becomes mandatory to assess the exact level ofdepth of anesthesia. For this purpose variousmethods were used but without rewarding results.Recently a new method of assessing depth ofanesthesia during operation has been introduced

which has encouraging result. It is an advancedform of electroencephalography and is known asBI SPECTRAL INDEX SCALE (B . I .S).


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To perform a bi-spectral analysis, data measuredby EEG are taken through a number of steps tocalculate a single number that correlates with

depth of anesthesia / hypnosis.BIS values of6585 have been advocated as a measure ofsedation,

4065 have been recommended for general

anesthesia

B I S

I___I___I___I___I___I___I___I__ I100 90 80 70 60 50 40 30 20

AWAKE SEDATION ANESTHESIA CORTICALSILENCE


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The use of Bispectral analysis may help in

reducing the chances of awareness duringanesthesia, an issue that is important to thepublic.

It may also reduce resource utilization because

less drug is required to ensure amnesia,facilitating a faster wake-up time and perhaps ashorter stay in the recovery room.

But unfortunately it is effective only in conventionalform of general anesthesia and not in Ketamine

anesthesia.


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11.Measurement of anestheticagent concentraion

Concentration of anesthetic agent in theend tidal air is also measured to assessthe level of anesthesia depth and to avoid

the dangerous side effects of strongvolatile anesthetic agents.


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12.Blood chemistry

Blood samples are sent to laboratory formeasurement of Hb % to assess bloodloss during surgery. Arterial blood gases

and electrolytes are measured to find outacid base disorders and electrolytedisturbances during operation.


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CONCLUSION

Monitoring during anesthesia hasrevolutionized field of anesthesia and useof very potent drugs has become possible

without serious complications.

Human brain has no substitute thereforepresence of qualified person has been put

as standard 1 of monitoring.


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Monitoring in Anesthesia Modified w

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