Transcript Intraoperative Monitoring

Intraoperative Monitoring
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?
 To understand & appreciate the value of
clinical monitoring.
 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???
 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.
 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:
 We are NOT authorised to start a surgery in the
absence of any of these monitors:
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ECG.
SpO2: arterial O2 saturation.
Blood Pressure: NIBP (non-invasive), IBP (invasive).
± [Capnography].
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:
 Heart rate.
 Rhythm (arrhythmias) usually best identified from lead
II.
 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:
 Choose a bony prominence. Avoid fatty regions
 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.
 Ensure good contact with the skin: by using KYGel.
 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 ‫)شخبطة‬: follow ECG
cable from the pt to the monitor:
Ensure good contact with the pt: non-hairy areas,
apply KY-Gel, search for slipped or loose
electrodes.
 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). ‫سلك األرضي‬
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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.
Arrythmias → check radial (peripheral)
pulsations.
(2) SpO2
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).
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.
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:
 Normal person on room air (O2 = 21%) ˃
96%.
 Patient under GA (100% O2) = 98-100%.
 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.
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ALWAYS Remember that your clinical
judgement is much more superior to the
monitor. Check pt colour for cyanosis: lips,
nails.
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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.
(3) Blood Pressure
Intraoperative monitoring: (3) BP
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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 BP-Diastolic BP- MAP.
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.
Intraoperative monitoring: (3) BP
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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
How to attach/apply:
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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 tight cuff
leads to false high readings, while a Loose cuff gives false Low
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:
 Pressure line is disconnected.
 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:
 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.
 Palpation of Radial A → systolic BP ˃ 90 mmHg.
 Palpation of Dorsalis Pedis A → systolic BP ˃ 80
mmHg.
 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)
 It is beat to beat monitoring of ABP via an arterial
cannula.
 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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Continuous CO2 measurement displayed
as a waveform sampled from the
patient’s airway during ventilation.
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What is Capnography?
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:
Balseline: A-B
 Upstroke: B-C
 Plateau: C-D
 End-tidal: point D
 Downstroke
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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):
ETT: esophageal intubation.
 Ventilation: hypo & hyperventilation, curare cleft
(spontaneous breathing trials).
 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).
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Intraoperative monitoring: (4) CO2
Factors affecting EtCO2: what ↑ what ↓
EtCO2?
Individual System Monitoring
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Position of ETT.
Respiratory System.
CVS & Hemodynamic Monitoring.
CNS: Awareness.
Temperature.
Monitoring after Extubation & Recovery.
(A) Correct Position of ETT
(A) Correct Position of ETT
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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.
(B) Respiratory Monitoring
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Clinical monitoring:
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Colour: cyanosis: nails, lips, palms,
conjunctiva.
Chest rise & fall (inflation).
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.
(B) Respiratory Monitoring
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.
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Low expired tidal volume: leakage.
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Apnea alarm: disconnection.
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O2 sensor failure: (unfortunately common in
many of our ventilators).
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Flow sensor failure: (unfortunately common
in many of our ventilators).
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(B) Respiratory Monitoring
Respiratory Monitors:
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O2 Saturation.
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Capnography EtCO2.
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Airway pressure.
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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:
 Check that the line is not kinked or
disconnected.
 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.
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Blood pressure (NIBP, IBP).
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Central Venous Pressure: value: indicator
of:
1)
2)
IV volume.
RV function.
(D) CNS: Awareness
Clinical monitoring:
Signs of pt awareness:
 Movement, grimacing (facial expression).
 Pupils dilated.
 Lacrimation.
 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 < 36oC. 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.
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 &
Recovery
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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:
“How do I monitor the patient in OR?”
The 4 basic monitors displayed on the
screen:
1) ECG.
2) BP.
3) SpO2.
4) ± Capnogram (EtCO2).
Normal target values for an adult under GA:
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HR: 60-90 (˃ 90 = tachycardia. < 60 =
bradycardia).
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BP: 90/60 – 140/90. MAP ˃ 60 mmHg
(cerebral & renal autoregulation).
Diastolic BP ˃ 50 mmHg (coronary
perfusion pressure).
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SpO2 ˃ 96% on 100% O2.
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EtCO2 = 30-35 mmHg.
LISTEN
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Listen to the monitor the whole time:
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To the pulse oximeter tone to identify: 1Heart rate 2- O2 saturation from the
tone (pitch) of pulse oximeter.
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.
XX NEVER XX
LööK
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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.
Clinical Check / 10 minutes
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)
b)
Check concentration opened.
Level of the volatile agent (if needs to be filled).
RULES NEVER to FORGET:
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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.