This document provides an overview of intraoperative patient monitoring. It defines monitoring as warning or recognizing issues. Key aspects of monitoring discussed include the cardiovascular, respiratory and central venous pressure systems. Specific monitoring modalities covered are ECG, blood pressure, pulse oximetry, capnography and blood gas analysis. The roles of monitoring in assessing oxygenation, ventilation and perfusion are emphasized.

1. INTRAOPERATIVE
MONITORING
DR T. MASIYIWA

2. DEFINITION
• The word monitor comes from the Latin word MONERE which means
warning
• ANAESTHETIC MONITORING-Interpret available clinical data to help
recognize present or future mishaps or unfavorable system conditions
• The role of intraoperative monitoring is to maintain normal patient
physiology and homeostasis throughout anaesthesia and surgery

3. What is the value of knowing this?
• To understand and appreciate the value of clinical monitoring
• To appreciate how modern monitors have made us more smarter.

4. INTRODUCTION
• The most primitive method of monitoring the patient 25 years ago
was visual monitoring of respiration and continuous palpation of the
radial pulse throughout the operation.

5. HARVEY CUSHING
• not just a famous neurosurgeon but he is the father of anaesthetic
monitoring
• Invented and popularized the use of the anesthetic chart
• Recorded both BP and HR. He then came up with a relationship
between vital signs and neurosurgical signs (increased ICP leads to
hypertension ,bradycardia and irregular respirations)

6. MONITORING IN THE PRESENT
• Standardized basic monitoring requirements from the ASA,CAS and
other national societies
• ASA Standard I-Qualified anaesthesia personell should be present in
the room throughout the conduct of all general, regional and
monitored anaesthesia
• ASA standard II-during all anesthetics the patients oxygen ventilation
circulation and temperature shall be continually evaluated.

7. MONITORING IN THE PRESENT
Canadian guidelines to the Practice of Anesthesia and patient
monitoring are:
• An anesthetist present
• A completed preanesthetic checklist.
• An anesthetic record (HR, BP, Drug, Fluid)
• Oxygenation, ventilation, circulation, and temperature are continually
evaluated both clinically and quantitatively

8. CLINICAL MONITORING
• Skin colour
• Urine output >0.5mls/kg
• Capillary refill
• Heart Rate
• Inflation of chest
• Precordial and esophageal stethoscopy
• Urine output

9. INSTRUMENTAL MONITORING

10. CARDIOVASCULAR SYSTEM MONITORING
•The circulatory system is responsible for oxygen
delivery and removal of waste products from organs
and this must be maintained during anaesthesia.

11. Signs and symptoms of perfusion
abnormalities
• CNS: mental status changes, neurologic deficits
• CVS: shortness of breathe,chest pain
• GIT:abd pain,descreased bowel sounds
• Peripheral:cool peripheries, diminished pulses,poor capillary refill
• Renal:descreased urine output,elevated urea nitrogen and
creatinine,decreased fractional excretion of sodium

12. CARDIOVASCULAR SYSTEM MONITORING
•Non invasive-ECG,NIBP
•Semi Invasive –Transesophageal
Echocardiography
•invasive-IBP,CVP,PAC

13. ECG
• The ECG monitors the conduction of electrical impulses throughout
the heart it can detect heart rate,myocardial ischemia,pacemaker
function,electrolyte abnormalities,drug toxicity,
• Rhythm detection is best seen in lead II (arrhythmias are best seen in
lead II ). Ischemia is detected in V5.
• NB the ECG does not indicate the mechanical performance of the
heart i.e cardiac output, tissue perfusion.

14. ECG PLACEMENT

16. ARTIFACTS IN ECG MONITORING
• Loose electrodes or broken leads
• Misplaced leads
• Wrong lead system selected
• Emphysema, pneumothorax
• Shivering or restelessness
• Respiratory variation and movement

17. BLOOD PRESSURE
TIMING
• Throughout the surgery: before induction till after extubation &
recovery.
FREQUENCY
• By default every 5 minutes.
• Every 3 minutes: immediately after spinal anaesthesia, in conditions
of hemodynamic instability, during hypotensive anaesthesia.
• Every 10 minutes: eg. In awake pts under local anaesthesia:
“monitored anaesthesia care” (minimal hemodynamic changes).

18. NIBP
• Measures BP at set intervals automatically by an automated
oscillometry
• Cuff size should cover 2/3 of arm
• A cuff too small overestimates and a cuff too large underestimates
• Small cuff to be used for children
• Usually attached to the limb opposite
the IV line & pulse oximeter

19. Transesophageal echocardiography
• Most sensitive in detecting any wall abnormalities i.e ischemia,
valvular dysfunction, air embolism.

20. Invasive Blood Pressure
• Required in patients who mandate beat to beat monitoring
• It is the gold standard method of monitoring blood pressure
• Arteries that can be used include the radial artery,brachial artery
femoral artery, dorsalis pedis artery.

21. ARTERIAL BLOOD PRESSURE
• Systolic Bp (SBP), Diastolic Bp (DBP) ,Pulse pressure (PP)= SBP-DBP
• Mean arterial pressure (MAP); average BP in an individual during a
single cardiac cycle
• MAP = DBP + 1/3 PP
• MAP range 65-110 mmHg

22. ALLEN’S TEST
• Normal <7s
• Borderline 7-14s
• Contraindicated >15s

23. Cannulation complications
• Arterial injury,spasms, distal ischemia
• Thrombosis,embolization
• Sepsis
• Tissue necrosis
• Fistula and aneurysm formation
• NB:To prevent complications continuous flush with/out heparin

24. Central venous pressure monitoring
INDICATIONS
• Major surgeries where large fluctuations in hemodynamics are expected
• Open heart surgeries
• Fluid management in shock
• As a venous access
• Parenteral nutrition
• Aspiration of air embolus
• Cardiac pacing Normal CVP is 6 to 8cm of H2O in adults and CVP 3 to 6 cm
of H2O in children
• CVP >20cm H2O indicates right heart failure

25. COMPONENTS OF CVP MONITORING
• a-wave: atrial pressure. It disappears in atrial fibrillation
• c-wave :closure of tricuspid valve
• a-x descent: ventricular systole
• v-wave atrial filling /tricuspid closure
• v- y descent: ventricular filling

26. Examples of CVP waveform abnormalities
• No A waves- Atrial fibrillation
• Giant A waves-uniform every beat, Right ventricular
hypertrophy,tricuspid stenosis,pulmonary hypertensionCOPD
• Cannon A waves-intermittent, various height.premature
beats,ventricular tachycardia,complete AV block
• Large V waves-tricuspid regurgitation,atrial septal defects
• Steep x, y descents-constrictive pericarditis

27. Common sites of insertion

28. Technique of CVP catheterization through
internal jagular
Seldinger technique
• Patient lies in Trendelenburg position to decrease chance of embolism
• The cannula stylet is inserted at the tip of the triangle formed by two heads
of the sternomastoid and clavicle the direction of the needle should be
slightly lateral and towards the ipsilateral nipple.
• Once the internal jugular vein is punctured the stylet is removed and a J
wire passed through cannula.
• Now the CVP catheter is railroad over the J wire
• The tip of the catheter should be at the junction of superior vena cava with
right atrium-15cm from entry point.

31. CVP is increased in
• Fluid overloading
• Congestive cardiac failure
• Pulmonary embolism
• Cardiac tamponade
• Constrictive pericardititis
• Pleural effusion
• Hemothorax
• Coughing and straining
• Intermittent positive pressure ventilation with PEEP

32. CVP is decreased in
• Hypovolemia and shock
• Venodilator
• Spinal/epidural anaesthesia
• General amaesthesia causing vasodilation
• LOW CVP + LOW BP= HYPOVOLEMIA
• HIGH CVP + LOW BP=PUMP FAILURE

33. COMPLICATONS
• Air embolism
• Thromboembolism
• Cardiac arrthymias
• Pneumothorax/hemothorax
• Cardiac perforation
• Trauma to brachial plexus

34. Pulmonary artery catheterization
• It is reserved for very major cases in severely compromised patients
because of cost,technical feasibility, complications
• Swan-ganz-catheter-it is a balloon tipped and flow directed by
pressure recording, pressure tracing and catheter tip,

36. Swan-ganz catheter/pulmonary artery catheter
• Provides diagnostic information to rapidly dertemine hemodynamic
pressures, cardiac output and blood sampling for mixed venous oxygen
saturation
• Measures CVP, PAP, Cardiac output
Indications
• Cardiac surgery/major surgery
• Resuscitation
• Shock
• Oxygen transport ventilation and perfusion
• Post MI

37. CVP VS PCWP

38. RESPIRATORY MONITORING
• Stethoscopes
• Pulse oximeter
• Capnograph
• Blood gas analysis
• Lung volumes
• Oxygen analysers
• Airway pressure monitoring
• Apnea monitoring

39. stethoscopes
• For gaseous exchange monitoring
• Chest auscultation remains the primary method of confirming
bilateral lung ventilation
• Precordial & oesophageal stethoscope
• Oesophageal stethoscope Contraindicated in oesophageal varices and
strictures

40. Pulse oximeter
• Oxygen saturation-SpO2
• Normal SpO2 96% and above and 98-100% in patients under GA
• Probe applied at finger/toe nail bed, ear lobule, tip of the nose
• Used to detect hypoxia intra and post operative

41. Working principle

42. Working principle
• Consists of two emitting lights- a RED(R) light in the visible spectrum
660nm and INFRARED (IR) 940nm light emitting LEDs and a photodetector
• Oxygenated and deoxygenated hemoglobin have differential light
absorption rate
• Oxygenated hemoglobin absorbs more infrared light and allows more red
light to pass through it
• Deoxygenated hemoglobin absorbs more red light and allows more
infrared light to pass through it.
• Photodetector measure the transmitted lights and calculates the R/IR ratio
which then determines the oxygen concentration in the blood

43. Working principle

45. Saturation waveforms

46. ERRORS
• Carboxyhaemoglobinemia
• Methemoglobenemia
• Anemia
• Hypovolemia and vasoconstriction
• Nail polish and Dyes
• Shivering
• Skin pigmentation
• Cardiac arrhythmias may interfere with the oximeter picking up the pulsatile signal properly
and with calculation of the pulse rate
• Sp02 below 70%
• Pernumbra effect
• Critically ill and hypothermic patients with poor peripheral perfusion
• Systolic bp less than 60

47. The role of pulse oximetry in the workup of
methemoglobinemia
• Pulse oximetry readings with low levels of methemoglobinemia often result in falsely low
values for oxygen saturation and are often falsely high in those with high level
methemoglobinemia.
• The reason for this is because:
• The pulse oximeter only measures the relative absorbance of 2 wavelengths of light (660
nm and 940 nm) to differentiate oxyhemoglobin from deoxyhemoglobin. The ratio of
absorption of light at each of these wavelengths is converted into oxygen saturation by
using calibration curves. Methemoglobin increases absorption of light at both
wavelengths (more at 940 nm) and therefore offers optical interference to pulse
oximetry by falsely absorbing light.
• As a result, oxygen saturations by pulse oximetry in methemoglobinemia plateau at
about 85%; therefore, a patient with a methemoglobin level of 5% and a patient with a
level of 40% have approximately the same saturation values on pulse oximetry (~85%).
The severity of the cyanosis does not correspond to the pulse oximetry reading: a patient
may appear extremely cyanotic but still have a pulse oximetry reading in the high 80s.

48. THE RAD-57 PULSE CO-OXIMETER

49. CAPNOGRAPHY
Definition of terms
• CAPNOMETRY: measurement of CO2 concentration during inspiration
and expiration.
• CAPNOGRAM: continuous display of CO2 waveform
• CAPNOGRAPHY continuous monitoring of pt’s capnogram
• Methods to measure CO2 levels include infrared spectrography,
Raman spectrography, mass spectrography, photoacoustic
spectrography and chemical colorimetric analysis

50. ROLE OF CAPNOGRAPH
• Confirmation of tracheal intubation
• Recognition of oesophageal intubation
• Assessment of adequacy of ventilation
• Identifying breathing circuit problems: disconnection, kinking,
leakage, obstruction, unidirectional valve dysfunction, rebreathing,
exhausted soda lime.
• Diagnosis of pulmonary embolism & cardiac arrest

51. Physical Principle
• The infrared method is most widely used and most cost-effective.
• Infrared rays are given off by all warm objects and are absorbed by
non-elementary gases (i.e. those composed of dissimilar atoms),
while certain gases absorb particular wavelengths producing
absorption bands on the IR electromagnetic spectrum.
• The intensity of IR radiation projected through a gas mixture
containing CO2 is diminished by absorption this allows the CO2
absorption band to be identified and is proportional to the amount of
CO2 in the mixture.

52. Types of capnographs
Side stream Capnography
• The CO2 sensor is located in the main unit itself (away from the airway)
and a tiny pump aspirates gas samples from the patients airway through a
6 foot long capillary tube into the main unit.
• The sampling tube is connected to a T-piece inserted at the endotracheal
tube or anaesthesia mask connector.
• Other advantages of the sidestream capnograph: no problems with
sterilisation, ease of connection and ease of use when patient is in unusual
positions like the prone position

53. Types of capnographs
Main stream Capnograph
• Cuvette containing the CO2 sensor is inserted between the breathing circuit and
the endotracheal tube.
• The IR rays traverse the respiratory gases to an IR detector within the cuvette.
• To prevent condensation of water vapour, which can cause falsely high CO2
readings, all main stream sensors are heated above body temperature
to about 40oC.
• It is relatively heavy and must be supported to prevent endotracheal tube
kinking.
• Sensors window must be kept clean of mucus and particles to prevent false
readings.
• Response time is faster

54. Main stream and Sidestream capnographs

55. CAPNOGRAPHY
• Normal range: 30-35 mmHg. (Usually lower than arterial PaCO2 by 5-
6 mmHg due to dilution by dead space ventilation).

56. PHASES OF A CAPNOGRAM
• Inspiratory baseline-gas is exhaled from the large conducting airways which
contain no CO2.it begins with air leaving the trachea,posterior pharynx,mouth
and nose. This is called dead space because no gas exchange occurs.
• Expiratory Upslope- CO2 from the alveoli begins to reach the upper airway and
mix with the dead space air causing a rapid rise in the amount of C02
• Expiratory Plateau-the CO2 curve remains relatively constant,as primarily
alveolar gas is exhaled known as alveolar plateau. The end of phase 3 is the end
of exhalation and it contains the greatest amount C02 (etCO2) which is the
number seen on the monitor.
• Expiratory downstroke-inhalation begins oxygen fills the airway and C02 levels
drop back to zero (amount of C02 measured quickly drops to zero)

58. FACTORS AFFECTING ETCO2

59. BLOOD GAS ANALYSIS
• PRECAUTION
• Glass syringe is preffered for sampling
• Syringes should be heparinized
• Samples should be stored in ice
• Samples from radial and femoral artery
• Important in hypothermia and hypotensive anaesthesia

60. NORMAL VALUES ON ROOM AIR

61. • Mixed venous oxygen is the best indicator of cardiac output i.e tissue
oxygenation
• Arterial oxygen is the better indicator of pulmonary function

62. OTHERS
Lung volumes-spirometry
Oxygen analysers
• they monitor actual value of oxygen delivered.
• Fitted in inspiratory limb of breathing circuit
• Useful in closed circuit (use low flow oxygen)
• Airway pressure monitoring
• It should be less than 20-25cm H2O
• Low pressure-disconnection
• High pressure- obstruction in tube or circuit and bronchospasm

63. EXPIRED GAS ANALYSIS
• There is a multigas analyzer which measures concentration of
anaesthetic vapors like nitrous oxide and inhalational agents like
halothane etc.
• These are mass spectrometers and Raman gas analyzers

64. TEMPERATURE MONITORING
• Continuous temperature monitoring is recommended but every
15minutes is acceptable
• High incidence of intraoperative hypothermia usually in:
• Paediatric patients
• Adults with burns
• Cardiac surgery
• Febrile patient

65. CORE TEMPERATURE MONITORING SITES
• Esophagus
• Pulmonary artery
• Nasopharynx
• Tympanic membrane-most accurate for brain temperature
• Axillary (0.5 less than core body temperature)
• Rectal
• Forehead (1 to 2 degrees less than core body temperature)

66. HYPOTHERMIA
• Core temperatures <35 degrees celcius
• Mild 28-35, moderate 21-27, severe <20
• Most anaesthetics used are vasodilators cause heat loss
• Other causes-cool fluids,cool operating room,evaporation

67. SYSTEMIC EFFECTS OF HYPOTHERMIA
• CVS- bradycardia,hypotension,ventriculat arrhythmias if temperature
less than 28 degrees
• RESP-respiratory arrest at temp below 23 degrees, oxygen
dissociation curve is shifted to the left
• BLOOD-increased blood viscosity and platelet count

68. SYSTEMIC EFFECTS OF HYPOTHERMIA
• ACID BASE BALANCE-increased solubility of blood gases,
acidosis(increased lactic acid production in blood stasis
• KIDNEY-decreased gfr, no urine output at 20 degrees celcius
• ENDOCRINE-decreased adrenaline and nor adrenaline,
hypergylacemia

69. Anaesthetic complications of hypothermia
• Delayed awakening by prolonging anaesthetic drug actions
• Impairs coagulation therefore increasing blood loss and transfusion
requirements
• Increases wound infections
• Increases heart rate, blood pressure and plasma catecholamines
• Increases postoperative discomfort and hospital stay

70. TREATMENT OF HYPOTHERMIA
• Warm intravenous fluids
• Increase room temperature. The ideal operation theatre temperature
should be 21 degrees celcius for adults and 28 degrees celcius for
children
• Cover the patient with blankets
• Forced warm air by a special instrument (Bair Hugger airflow device)

71. Bair Hugger airflow device)

72. USES OF INDUCED HYPOTHERMIA
• Brain protection-in cardiac arrest or neurovascular surgeries the brain
can be protected for 10 minutes at 30 degrees celcius.
• tissue protection against ischemia in cardiac surgeries done on heart
lung machine.

73. URINE OUTPUT
• Urine out put is the reflection of kidney perfusion and function & indicator
of renal, cardiovascular & fluid status
• Catheterization is the most reliable method of monitoring urine output
• Urine output must be about 1ml/kg/hr
• Oliguria <0.5ml/kg/hr
Indications
• Cardiac &vascular surgery
• CCF pts, Renal failure pts and severe liver disease pts
• Method Foley’s catheter

74. MONITORING OF BLOOD LOSS
• Estimation of blood loss is done by weighing blood soaked swabs and
sponges (Gravimetric method) and estimation of blood loss by visual
inspection of suction bottle volume contents(Volumetric method).
• Most accurate method is colorimetric method

75. CENTRAL NERVOUS SYSTEM MONITORING
• There is need to monitor the depth of anaesthesia
• Clinically signs of light anaesthesia are:
• Tachycardia
• Hypertension
• Lacrimation
• Pespiration
• Movement response to painfull stimuli
• Eye movements
• Preserved reflexes
• Tachypnea,breathe holding,coughing,laryngospam

76. CNS MONITORS
• EEG
• Patient evoked response
• Bispectral index
• Entropy-detection of abnormalities in EEG at higher concentration of
anaesthetic agents

77. Neuromuscular monitoring
• Peripheral nerve stimulation
• Train of Four
• Single twitch
• Tetanic stimulation
• Post tetanic facilitation
• Double burst stimulation

78. Take home message
•The best monitor in the operating room is the
anaesthetist your clinical judgement is more valuable
and better than any digital monitor.
•Ecg machine changes in hypothermia

79. References
• Morgan and Mikhail’s Clinical Anaesthesiology Sixth Edition
• Oxford Handbook Of Anaesthesia Third Edition
• Lake CL, Hines RL, Blitt CD. Clinical monitoring: Practical implications
for anesthesia and critical care 2011
• Stoelting RK, Miller RD. Basics of anesthesia Fourth Edition

80. •THANK YOU