By Dr.Doaa Kamal

Intraoperative monitoring: Introduction
The most primitive method of monitoring the patient 25 years ago was continuous palpation of the radial pulsations throughout the operation!!

What is the value of knowing this?
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To understand & appreciate the value of clinical monitoring.
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RULE: your clinical
judgement/assessment is much
BETTER & much more VALUABLE than the digital monitor.
To appreciate that modern monitors have made life much easier for us. They are present to make monitoring easier for us
NOT to be omitted or ignored.

Intraoperative monitoring: Introduction
Why do we need intraoperative monitoring???
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To maintain the normal pt physiology & homeostasis throughout anesthesia and surgery: induction, maintenance & recovery as much as possible. To ensure the well being of the pt.
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Surgery is a very stressful condition → severe sympathetic stimulation, HTN, tachycardia, arrhythmias.
Most drugs used for general & regional anesthesia cause hemodynamic instability, myocardial depression, hypotension & arrhythmias.
Under GA the pt may be hypo or hyperventilated and may develop hypothermia.
Blood loss → anemia, hypotension. So it is necessary to recognise when the pt is in need of blood transfusion
(transfusion point).

Intraoperative monitoring: Introduction
The FOUR BASIC Monitors:
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We are NOT authorised to start a surgery in the absence of any of these monitors:
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ECG.
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SpO2: arterial O2 saturation.
Blood Pressure: NIBP (non-invasive), IBP (invasive).
± [Capnography].
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The most critical 2 times during anesthesia are:
INDUCTION - RECOVERY .
Exactly like “ flying a plane ” induction (= take off) & recovery (= landing). The aim is to achieve a smooth induction & a smooth recovery & a smooth intraoperative course.

(1) ECG

Intraoperative monitoring: (1) ECG
Value:
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Heart rate.
Rhythm (arrhythmias) usually best identified from lead
II.
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Ischemic changes & ST segment analysis.
Timing of ECG monitoring: Throughout the surgery: before induction until after extubation & recovery.
Types & connections of ECG cables:
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3-leads : Red=Right YeLLow=Left
Black=Apex (can read leads: I, II, III)
5-leads : Red=Right YeLLow=Left
Black=under red Green=under yellow
White=central (can read any of the 12 leads: I,
II, III, avR, avL, avF, V1-V6).

Intraoperative monitoring: (1) ECG
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How to attach ECG electrodes:
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Choose a bony prominence . Avoid fatty regions
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AVOID hairy areas (up to shaving if required in very hairy persons).
Position them far away from each other to give e higher voltage and better gain.
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Ensure good contact with the skin: by using KY-
Gel.
If the electrodes will not be accessible during the surgery (eg. on the back in thyroidectomy or breast surgery) or will be soaked in betadine (eg. in abdominal surgery) after ensuring good ECG trace cover the stickers with adhesive tape.

Intraoperative monitoring: (1) ECG
If the EGC gives no trace (noise ةطبخش ): follow ECG cable from the pt to the monitor:
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Ensure good contact with the pt: non-hairy areas, apply KY-Gel, search for slipped or loose electrodes.
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Ensure proper fitting of cable connections.
(Sometimes we apply alcohol to dissolve betadine).
Ensure proper fitting of the cable to the monitor.
Change monitor settings: try different leads (I, II,
III, avR, avR, avL, V1-6), filter, size (amplitude) of
ECG.
Ensure earthing of the monitor (earth cable from behind). يضرلأا كلس

Intraoperative monitoring: (1) ECG
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RULES:
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QRS beep ON must be heard at all times.
NO silent monitors.
Remember that your clinical judgement is much more superior to the monitor.
Check peripheral pulsations.
Cautery → artefacts & fallacies in ECG
(noise/ electrical interference) → check radial (peripheral) pulsations.
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Arrythmias → check radial (peripheral) pulsations.

(2) SpO

Intraoperative monitoring: (2) SpO2
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It is the most important monitor. It gives a LOT of information about the pt.
Definition : % of oxy-Hb / oxy + deoxy-Hb .
Timing of SpO2 monitoring: throughout the surgery: before induction till after extubation & recovery. It is the LAST monitor to be removed off the pt before the pt is transferred outside the operating room to recovery room. SpO2 monitoring should be continued in recovery room.
Waveform of pulse oximeter = plethysmography (arterial waveform). It indicates that the pulse oximeter is reading the arterial O2 saturation. Without the waveform pulse oximeter readings are unreliable & incorrect.

Intraoperative monitoring: (2) SpO2
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Value:
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SpO2 : arterial O2 saturation (oxygenation of the pt).
HR .
Peripheral perfusion status (loss of waveform in hypoperfusion states: hypotension & cold extremeties).
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Gives an idea about the rhythm from the plethysmography wave (arterial waveform). (Cannot identify the type of arrhythmia but can recognize if irregularity is present).
Cardiac arrest.
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N.B. Pulse oximeter tone changes with desaturation from high pitched to low pitched
(deep sound). So just by listening to the monitor you can recognize: (1) HR (2) O2 saturation .

Intraoperative monitoring: (2) SpO2
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How to attach/apply saturation probe:
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To the finger or toe (if finger is not accessible). The red light is applied to the nail. Nail polish and stains should be removed
→ false readings and artefacts.
Can also be applied to the ear lobe.
In infants and children can be applied to 2 fingers or to the hand.
Usually attached to the limb with the IV line
(opposite the limb with the blood pressure cuff).

Intraoperative monitoring: (2) SpO2
Readings:
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Normal person on room air (O2 = 21%) ˃
96%.
Patient under GA (100% O2) = 98-100%.
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It is not accepted for O2 saturation to ↓ below 96% with 100% O2 under GA.
Must search for a cause.
< 90% = hypoxemia.
< 85% = severe hypoxemia.

Intraoperative monitoring: (2) SpO2
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Fallacies & Inaccuracies occur when:
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Misplaced on the pts finger, slipped.
Pt movement, shivering.
Poor tissue perfusion (cold extremities) → warm the pt, put a glove filled with warm water in the pts hand (always avoid hypothermia).
Poor tissue perfusion (hypotension & shock).
Cardiac arrest.
Sometimes by electrical interference from cautery in some monitors.

Intraoperative monitoring: (2) SpO2
RULES:
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Keep the sound of the pulse oximeter ON at
ALL times.
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Pay attention to the sound of the pulse oximeter. NO silent monitors.
ALWAYS Remember that your clinical judgement is much more superior to the monitor. Check pt colour for cyanosis: lips, nails.
If hypoxemia occurs immediately check the correct position of the probe on the pt and check the pts colour : nails & lips, then manage accordingly & CALL 4 HELP .

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Intraoperative monitoring: (3) BP
NIBP: (non-invasive ABP monitoring = automated).
Gives readings for: systolic BP, diastolic BP & MAP:
Systolic/ diastolic (mean).
Value: to avoid and manage extremes of hypotension &
HTN. Systolic BPDiastolic BPMAP.
Avoid ↓ MAP < 60 mmHg (for cerebral & renal perfusion) & avoid ↓ diastolic pressure < 50 mmHg
(for coronary perfusion).
Risks of HTN episodes: → (CVS): myocardial ischemia, pulmonary edema, (CNS): hemorrhagic stoke, hypertensive encephalopathy. While hypotensive episodes: (CVS): myocardial ischemia, (CNS): ischemic stroke, hypoperfusion state metabolic acidosis, delayed recovery, renal shutdown.

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Intraoperative monitoring: (3) BP
Timing of BP monitoring : throughout the surgery: before induction till after extubation & recovery.
Frequency of measurement :
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By default every 5 minutes.
Every 3 minutes: immediately after spinal anesthesia, in conditions of hemodynamic instability, during hypotensive anesthesia.
Every 10 minutes: eg. In awake pts under local anesthesia: “ monitored anesthesia care ”
(minimal hemodynamic changes).

Intraoperative monitoring: (3) BP
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How to attach/apply:
Correct cuff size : width of the cuff should be 1.5 times limb diameter and should occupy at least 2/3 of the arm.
2 cuff sizes for adult: blue : for most adult individuals (60-90 Kg), red : for morbid obese.
Selection of appropriate cuff size is important because a ti gh t cuff leads to false hi gh readings, while a L oose cuff gives false L ow readings.

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Is better applied directly to the arm (remove sleeve).
May also be applied to the forearm in very obese individuals. May be applied to the calf if the arms are not accessible during surgery.
Correct positioning : cuff is positioned with the hoses over the brachial artery .
Usually attached to the limb opposite the IV line & pulse oximeter. Unless the pt is performing hand or arm or breast surgery, the BP cuff is attached with the IV line and saturation probe on the same side.
AVOID attaching it to an arm with A-V graft (for renal dialysis) → damage of AV graft, & inaccurate measurements.

Intraoperative monitoring: (3) BP
Reading Error/failure:
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Pressure line is disconnected.
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Leakage from damaged cuff.
Line is compressed (under someone’s foot or under a weal).
Line contains water from washing!
Monitor error: cuff cannot inflate due to infant or neonate limits.

Intraoperative monitoring: (3) BP
RULE:
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YOUR clinical judgement is always superior to the monitor. Must check peripheral pulse volume from time to time (Radial A, or Dorsalis Pedis A, or Superficial
Temporal A) regularly every 10 minutes.
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Palpation of Radial A → systolic BP ˃ 90 mmHg.
Palpation of Dorsalis Pedis A → systolic BP ˃ 80 mmHg.
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Palpation of Superficial Temporal A → systolic BP ˃
80 mmHg.
i.e If Radial A pulsations are lost = systolic BP is < 90 mmHg.
If dorsalis pedis & superficial temporal pulsations are lost
= systolic BP is < 80 mmHg.
Check pt colour for pallor : lips, tongue, nails, conjunctiva.

Intraoperative monitoring: (3) BP
IBP: (invasive arterial blood pressure monitoring)
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It is beat to beat monitoring of ABP via an arterial cannula.
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Indicated in: major surgeries, during deliberate hypotensive anesthesia, during the use of inotropes, cardiac surgery, in surgeries involving extreme hemodynamic changes/instability eg. pheochromocytoma, repeated ABG sampling.

(4) Capnography (CO2)

Intraoperative monitoring: (4) CO2
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Definition :
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What is Capnography?
Continuous CO2 measurement displayed as a waveform sampled from the patient’s airway during ventilation.
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What is EtCO2?
A point on the capnogram. It is the final measurement at the endpoint of the pts expiration before inspiration begins again.
It is usually the highest CO2 measurement during ventilation.

Intraoperative monitoring: (4) CO2
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Phases of the capnogram:
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Balseline: A-B
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Upstroke: B-C
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Plateau: C-D
End-tidal: point D
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Downstroke

Intraoperative monitoring: (4) CO2
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Normal range : 30-35 mmHg . (Usually lower than arterial PaCO2 by 5-6 mmHg due to dilution by dead space ventilation).
Value (data gained from capnography &
ETCO2):
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ETT : esophageal intubation.
Ventilation : hypo & hyperventilation, curare cleft
(spontaneous breathing trials).
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Pulmonary perfusion : pulmonary embolism.
Breathing circuit : disconnection, kink, leakage, obstruction, unidirectional valve dysfunction, rebreathing, exhausted soda lime.
Cardiac arrest: adequacy of resuscitation during cardiac arrest, and prognostic value (outcome after cardiac arrest).

Intraoperative monitoring: (4) CO2
Factors affecting EtCO2: what ↑ what ↓
EtCO2?

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Position of ETT.
Respiratory System.
CVS & Hemodynamic Monitoring.
CNS: Awareness.
Temperature.
Monitoring after Extubation & Recovery.

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After intubation Auscultation MUST be done in 5 areas:
► Rt & Lt infraclavicular.
► Rt & Lt axillary.
► EPIGASTRIUM : to exclude esophageal intubation.
We MUST ALWAYS auscultate the chest after intubation for:
(1) Equal air entry : to exclude endobronchial intubation.
(2) Adventitious sounds : wheezes, crepitations, pulmonary edema.
We MUST ALWAYS auscultate the chest AGAIN after repositioning to exclude:
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Inward displacement → endobronchial intubation.
Outward displacement → slippage & accidental extubation.

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Clinical monitoring:
Colour: cyanosis: nails, lips, palms, conjunctiva.
Chest rise & fall (inflation).
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Vapour in ETT (absent in ventilators with humdifiers/if filter is used).
Airway pressure.
Ventilator bellows (return to full inflation during expiratory phase).
Ventilator sound: during resp cycle.
Abnormal sounds eg. leakage, disconnection, high airway pressure, alarms.

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N.B. Various alarms by the ventilator:
NEVER ignore an alarm by the ventilator!
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Low airway pressure : leakage, disconnection.
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High airway pressure : kink, biting of the tube, bronchospasm, slipped → esophagus.
Low expired tidal volume : leakage.
Apnea alarm : disconnection.
O2 sensor failure : (unfortunately common in many of our ventilators).
Flow sensor failure : (unfortunately common in many of our ventilators).

Respiratory Monitors:
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O2 Saturation.
Capnography EtCO2.
Airway pressure.
ABG samples.

(C) CVS Hemodynamic Monitoring
Clinical monitoring:
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Colour: pallor (lips, tongue, nails) = anemia, shock.
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Palpate peripheral pulsations every 10 minutes
(Radial A, Dorsalis pedis A, Superficial temporal A).
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Capillary refilling time : compress nail bed until it is blanched. After release of pressure refilling should occur within 2 seconds. If ˃ 5 seconds = poor peripheral perfusion/circulation.
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UOP :
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Values: it is an indicator of: 1) good hydration 2) good tissue
(renal) perfusion 3) good renal function. [Urine is the champagne of anesthetists and urologists!!].
Indications: 1) lengthy surgery ˃ 4 hrs 2) major surgery with major blood loss 3) C-section: to monitor injury to the bladder or ureter.
Normal: 0.5-1 ml/kg/hr.
When the catheter is inserted u must always note the baseline urine volume at the start of operation.

(C) CVS Hemodynamic Monitoring
Management of oliguria or anuria:
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Check that the line is not kinked or disconnected .
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Palpate the urinary bladder (suprapubic fullness), or ask the surgeon to palpate it.
Raise BP (MAP ˃ 80 mmHg): renal perfusion.
IV fluid challenge .
Diuretics .
N.B. Sometimes trendlenberg position (head down) causes ↓ UOP. Reversal of this position results in immediate flow of urine.

(C) CVS Hemodynamic Monitoring
CVS Monitors:
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ECG.
Blood pressure (NIBP, IBP).
Central Venous Pressure: value: indicator of:
1)
IV volume.
2)
RV function.

(D) CNS: Awareness
Clinical monitoring:
Signs of pt awareness:
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Movement, grimacing (facial expression).
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Pupils dilated.
Lacrimation.
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Tachycardia.
HTN.
Sweating: is always an alarming/warning sign . Causes:
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Awareness.
Hypoglycemia.
Hypercapnia.
Thyroid storm (thyrotoxic crisis).
Fever.
Always check the concentration of ur vaporizer & make sure that ur vaporizer is not empty (below minimum = gives a concentration lower than adjusted).

(E) Temperature Monitoring
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Clinical monitoring : ur hands.
Monitors : temperature probe: nasopharyngeal, esophageal.
AVOID hypothermia < 36 o C . Why? & How?
Especially in pediatrics & geriatrics (extremes of age).
Why is it necessary to avoid hypothermia?
(complications of hypothermia):
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Cardiac arrhythmias: VT & cardiac arrest.
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Myocardial depression.
Delayed recovery (delays drug metabolism).
Delayed enzymatic drug metabolism.
Metabolic acidosis (tissue hypoperfusion → anerobic glycolysis → lactic acidosis) & hyperkalemia.
Coagulopathy.

(E) Temperature Monitoring
How to avoid hypothermia:
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Warm IV fluids.
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Intermittently switching off airconditioning esp. towards the end of surgery ( ↑ ambient room temp ).
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Pediatrics: warming blanket.

(F) Monitoring After Extubation &
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Recovery
After extubation : immediately fit the face mask on the pt (with a slight chin lift) and observe the breathing bag:
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Good regular breathing with adequate tidal volume transmitted to the bag.
No transmission to the bag → respiratory obstruction
(improve ur support), or apnea (attempt to awaken ur pt by painful stimulus or jaw thrust).
BP: within 20% of baseline.
SpO2 : ˃ 92%
Breathing : regular, adequate tidal volume.
Muscle power : sustained head elevation for 5 seconds, good hand grip, tongue protrusion.
Level of consciousness : fully conscious = 1) obeying orders, 2) eye opening, 3) purposeful movement.
MOST IMP: Pt MUST be able to protect his own
airway.

To Summarize:
The 4 basic monitors displayed on the screen:
1)
ECG.
2)
3)
4)
BP.
SpO2.
± Capnogram (EtCO2).

Normal target values for an adult under GA:
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HR: 60-90 (˃ 90 = tachycardia. < 60 = bradycardia).
BP: 90/60 – 140/90. MAP ˃ 60 mmHg
(cerebral & renal autoregulation).
Diastolic BP ˃ 50 mmHg (coronary perfusion pressure).
SpO2 ˃ 96% on 100% O2.
EtCO2 = 30-35 mmHg.

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Listen to the monitor the whole time :
To the pulse oximeter tone to identify: 1-
Heart rate 2O2 saturation from the tone (pitch) of pulse oximeter.
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To the sound of the ventilator , to any abnormal sounds, any alarms.
RULE: NO silent monitors. ALWAYS keep the HR sound on . If ur monitor is silent
(sound is not working) u have to look at your monitor the WHOLE time.

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Every 5 minutes to note the new BP reading.
If there is any change in the tone of the pulse oximeter.
If there is any irregularity in heart rate & during the use of diathermy.

10
1) Chest inflation .
2) Ventilator bellows : descend and return to become fully inflated.
3) Airway pressure.
4) Palpate peripheral pulsations (radial A, or dorsalis pedis
A, or superficial temporal A):
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For pulse volume.
During the use of cautery.
In doubt of ECG rhythm (arrythmias).
In case monitor or ECG disconnected.
5) Pt colour (nails): cyanosis, pallor.
6) Vaporizer : a)
Check concentration opened.
b)
Level of the volatile agent (if needs to be filled).

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Never start induction with a missing monitor: ECG,
BP, SpO2.
Never remove any monitors before extubation & recovery.
NEVER ignore an alarm by the ventilator.
ALWAYS remember than ur clinical sense & judgement is better than & superior to any monitor. U are a doctor u are not a robot. The monitor is present to help u not to be ignored and not to cancel ur brain.
Last but by no means least:
ALWAYS remember that there is NO such thing as
“all monitors disconnected” → check that ur pt is
ALIVE !! Immediately check peripheral & carotid pulsations to make sure that ur pt is not
ARRESTED !! Once u have ensured pt safety reattach ur monitors once again.