Monitoring During anaesthesia

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Monitoring During anaesthesia

• Prof. Abdulhamid Al-Saeed, FFARCSI
• Anaesthesia Department
• College of Medicine
• King Saud University

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Lecture Objectives..Students at the end of the
lecture will be able to knows

• Monitors
• Non-invasive blood pressure , ECG , pulse
  oximetry capnography (CO2 monitor) and oxygen
  analyzer , temperature probe nerve stimulator
• Specialized monitors
• arterial line (invasive blood pressure)
• central venous line (cvp monitoring)
• pulmonary artery flotation catheter ( monitors
  function of right and left side of the heart)
• BIS monitor (depth of anesthesia)

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Monitoring A Definition

• interpret available clinical data to help
  recognize present or future mishaps or
  unfavorable system conditions

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Monitoring in the Past

• Visual monitoring of respiration and overall
  clinical appearance
• Finger on pulse
• Blood pressure (sometimes)

Finger on the pulse
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Monitoring in the Present

• Standardized basic monitoring requirements
  (guidelines) from the ASA (American Society of
  Anesthesiologists), CAS (Canadian
  Anesthesiologists Society) and other national
  societies
• Many integrated monitors available
• Many special purpose monitors available
• Many problems with existing monitors (e.g., cost,
  complexity, reliability, artifacts)

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Standard

• ASA monitoring for general anesthesia ,
  monitored anesthesia care and regional anesthesia
  -
• Oxygenation (oxygen analyzer, pulse oximetry),
• Ventilation (capnography, minute ventilation),
  respiratory rate (under regional anesthesia)
• Circulation (electrocardiogram ECG, arterial
  blood pressure, perfusion assessment),
• Temperature.

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High Tech Patient Monitoring
Examples of Multiparameter Patient Monitors
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High Tech Patient Monitoring
Transesophageal Echocardiography
Depth of Anesthesia Monitor
Evoked Potential Monitor
Some Specialized Patient Monitors
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Cardiovascular system.

• The circulatory system is responsible for oxygen
  delivery to and removal of waste products from
  the organs, and this must be maintained during
  anesthesia.

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Signs and symptoms of perfusion abnormalities

• Central nervous system mental status changes,
  neurologic deficits.
• Cardiovascular system chest pain, shortness of
  breath, ECG abnormalities, wall motion
  abnormalities on echocardiogram.
• Renal decreased urine output, elevated blood
  urea nitrogen and creatinine, decreased
  fractional excretion of sodium.
• Gastrointestinal abdominal pain, decreased bowel
  sounds, hematochezia.
• Peripheral cool limbs, poor capillary refill,
  diminished pulses.

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ECG.

• The ECG monitors the conduction of electrical
  impulses through the heart.
• Rhythm detection is best seen in lead II.

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ECG
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Electrocardiogram

• Displays the overall electrical activities of the
  myocardial cells
• Heart rate dysrhythmias
• Myocardial ischaemia
• Pacemaker function
• Electrolyte abnormalities
• Drug toxicity
• Does NOT indicate mechanical performance of the
  heart
• Cardiac output
• Tissue perfusion

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• Full (12)-lead ECG
• Standard limb leads (bipolar)
• Precordial leads (unipolar)
• 5.lead system
• Unipolar bipolar
• RA, LA, RL, LL, C
• 3.lead system
• Bipolar with RA, LA, LL
• V5 usually used
• Best compromise between detecting ischaemia and
  diagnosing arrhythmia
• May come with ST-segment analysis

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ECG
Standard Limb Leads Unipolar Chest Leads
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Artifacts in ECG Monitoring

• Loose electrodes or broken leads
• Misplaced leads
• Wrong lead system selected
• Emphysema, pneumothorax, pericardial effusion
• Shivering or restlessness
• Respiratory variation and movement
• Monitor Pulse Oximetry, Invasive ABP

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Arterial blood pressure.

• Automated noninvasive blood pressure is the most
  common noninvasive method of measuring blood
  pressure in the operating room.
• Invasive blood pressure monitoring uses an
  indwelling arterial catheter coupled through
  fluid-filled tubing to a pressure transducer.
• The transducer converts pressure into an
  electrical signal to be displayed.
• Indications
• Need for tight blood pressure control (e.g.,
  induced hyper- or hypotension).
• Hemodynamically unstable patient.
• Frequent arterial blood sampling.
• Inability to utilize noninvasive blood pressure
  measurements.

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Arterial Blood Pressure
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Central venous pressure (CVP) and cardiac output

• CVP is measured by coupling the intravascular
  space to a pressure transducer using fluid-filled
  tubing.
• Pressure is monitored at the level of the vena
  cava or the right atrium.
• Indications
• Measurement of the right heart filling pressures
  to assess intravascular volume and right heart
  function.
• Drug administration to the central circulation.
• Intravenous access for patients with poor
  peripheral access.
• Indicator injection for cardiac output
  determination (e.g., green dye cardiac output).
• Access for insertion of pulmonary artery
  catheter.
• Range The CVP is normally 2 to 6 mm Hg

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Central Venous Pressure
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PULMONARY ARTERY CATHETER
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Pulmonary Artery Catheter
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Haemodynamic Profiles Obtained from PA Catheters

• SV CO / HR (60-90 mL/beat)
• SVR (MAP CVP) / CO ? 80
  (900-1500 dynes-sec/cm5)
• PVR (MPAP PCWP) / CO ? 80
  (50-150 dynes-sec/cm5)

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• O2 delivery (DO2)
• C.O. ? O2 content
• Arterial O2 content (CaO2) ( Hb ? 1.38 ) ?
  (SaO2)
• Mixed venous O2 content (CvO2) ( Hb ? 1.38 ) ?
  (SvO2)
• O2 consumption (VO2) C.O. ? (CaO2-CvO2)
• SvO2 SaO2 VO2 / (Hb ? 13.8)(CO)

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• Respiratory system.
• pulse oximetry, capnography, a fraction of
  inspired oxygen analyzer, and a disconnect alarm.
  
•  Pulse oximeter
• combines the principles of oximetry and
  plethysmography to noninvasively measure oxygen
  saturation in arterial blood.
• The pulse oximeter probe contains two light
  emitting diodes at wavelengths of 940nm and 660
  nm.
• Oxygenated and reduced hemoglobin differ in light
  absorption (940 and 660 nm respectively).
• Thus the change in light absorption during
  arterial pulsation is the basis of oximetry
  determination.
• The ratio of the absorption at the two
  wavelengths is analyzed by a microprocessor to
  record the oxygen saturation.
•  
•  

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Pulse Oximetry
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Incomptencies

• Critically ill with poor peripheral circulation
• Hypothermia VC
• Dyes ( Nail varnish )
• Lag Monitor Signalling 5-20 sec
• PO2
• Cardiac arrhythmias may interfere with the
  oximeter picking up the pulsatile signal properly
  and with calculation of the pulse rate
• Abnormal Hb ( Met., carboxy)

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• Capnometry
• What is Capnometry?
• Is the measurement of end-tidal carbon dioxide
  tension.
• This provides valuable information to the
  anesthesiologist.
• The presence of end tidal CO2 aids in confirming
  endotracheal intubation.
• Alteration in the slope of the graph can give
  clues to the presence of airway obstruction.
• A rapid fall in reading may signify extubation,
  air embolism or low cardiac output with
  hypovolemia.

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• The Alpha angle
• The angle between phases II and III, which has
• increases as the slope of phase III increases.
• The alpha angle is an indirect indication of V/Q
• status of the lung.
• Airway obstruction causes an increased
• slope and a larger angle.
• Other factors that affect the angle are the
  response time of the capnograph, sweep speed, and
  the respiratory cycle time.

• The Beta angle
• The nearly 90 degrees angle between phase III and
  the descending limb in a time capnogram has been
  termed as the beta angle.
• This can be used to assess the extent of
  rebreathing. During rebreathing, there is an
  increase in beta angle from the normal 90
  degrees.

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Clinical Applications
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Central nervous system (level of consciousness)
monitoring

• Bispectral index (BIS) assess central nervous
  system depression during general anesthesia.
• It is based on the surface electroencephalogram
  (EEG), which predictably changes in amplitude and
  frequency as the depth of anesthesia increases.

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Temperature monitoring

• Indications
• Infants and small children are prone to thermal
  lability due to their high surface area to volume
  ratio.
• Adults subjected to large evaporative losses or
  low ambient temperatures (as occur with exposed
  body cavity, large volume transfusion of unwarmed
  fluids, or burns) are prone to hypothermia.
• Malignant hyperthermia is always a possible
  complication, and temperature monitoring should
  always be available.

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• Monitoring site
• Tympanic membrane temperature
• Rectal temperature
• Nasopharyngeal temperature,
• Esophageal temperature monitoring reflects the
  core temperature well. The probe should be
  located at the lower third of the esophagus and
  rarely may be misplaced in the airway.
• Blood temperature measurements may be obtained
  with the thermistor of a PAC.

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Neuromuscular blockade monitoring

• Neuromuscular blockade is monitored during
  surgery to guide repeated doses of muscle
  relaxants and to differentiate between the types
  of block.
• All techniques for assessing neuromuscular
  blockade use a peripheral nerve stimulator (PNS)
  to stimulate a motor nerve electrically.

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Detecting Mishaps Using Monitors

• 8. Pneumothorax
• 9. Air Embolism
• 10. Hyperthermia
• 11. Aspiration
• 12. Acid-base imbalance
• 13. Cardiac dysrhythmias
• 14. IV drug overdose
• Source Barash Handbook

• 1. Disconnection
• 2. Hypoventilation
• 3. Esophageal intubation
• 4. Bronchial intubation
• 5. Circuit hypoxia
• 6. Halocarbon overdose
• 7. Hypovolemia

These mishaps
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Detecting Mishaps with Monitors

• Pulse oximeter
• Capnograph
• Automatic BP
• Stethoscope
• Spirometer
• Oxygen analyzer
• ECG
• Temperature

• 1,2,3,4,5,8,9,11,14
• 1,2,3,9,10,12
• 6,7,9,14
• 1,3,4,13
• 1,2
• 5
• 13
• 10
• Source Barash Handbook

are detected using these monitors
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Question NO. 8

• 1- Identify the monitor Tracing?
• 2- What is the Name Cause of the Notch on the
  descending limb of the trace?
• 3- Name two different Clinical informations could
  be interpreted from this tracing?
• a) ..
• b) ..

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Question NO. 10

• 1- Identify the Rhythm in the shown ECG Strip?
• ---------------------------------------------
  ---------
• 2- What is your first line of management in case
  of Unstable patient
• 3- What is the normal QRS duration

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Question NO. 14

• 1- Identify the tracing
• 2- Name the different phases of the trace
• I ?
• II ? ..
• III ? .
• IV ? ..
• 3- What different clinical informations could be
  interpreted from the trace
• a) ..
• b) ..

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Question NO. 15

• 1- Name the different waves on the trace?
• ------------------------------------------------
• 2- Define Central Venous Pressure?
• 3- What are the main determinants regulating CVP?
• A-.
• B- ...

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Question NO. 19

• brief the mechanism of action of this monitor
• 
  
• Name 4 factors affecting the accuracy of this
  monitor?
• If P50 of oxyhemoglobine dissociation curve is
  40 is this curve shifted to the right or left
  mention 3 possible causes?
• ..

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• 36-Each of the following factors may lead to
  error in readings using pulse oximetry EXCEPTA.
  electrocauteryB. high cardiac output statesC.
  infrared lights near the sensorD. intravenous
  dyesE. severe hemodilution