Monitoring During Thoracic Anesthesia

1
Monitoring During Thoracic Anesthesia
2
Outline

• Introduction
• Physiological Aspects
• Monitoring Requirements

3
Introduction
4
Thoracic anesthesia is challenging
Patient
Procedure
5
Physiological Aspects
6
Principles of Ventilation and Perfusion

• V" - ventilation - the air which reaches the
  lungs
• "Q" - perfusion - the blood which reaches the
  lungs
• Normal V is 4 L of air per minute.
• Normal Q is 5L of blood per minute.
• So Normal V/Q ratio is 4/5 or 0.8.
• When the V/Q is higher than 0.8, it means
  ventilation exceeds perfusion.
• When the V/Q is lt 0.8, there is a VQ mismatch
  caused by poor ventilation

7
Principles of Ventilation and Perfusion

• An area with no ventilation (and thus a V/Q of
  zero) is termed "shunt."
• An area with no perfusion (and thus a V/Q of
  infinity) is termed dead space

8
Lung Compliance

• A change in volume divided by a change in
  transpulmonary pressure.
• (CL ?V / ?PL)
• A typical value of compliance is 200 ml/cm H20

9
Monitoring
10
Lateral Decubitus Position

• Optimal access for most operations
• Alter the normal pulmonary ventilation/perfusion
  relationships accentuated by
• Induction of anesthesia Initiation of
  mech.ventilation
• Opening the chest Surgical
  retractions

11
Principles of Ventilation and Perfusion
Perfusion
Ventilation
Pulmonary blood flow distribution relative to the
alveolar pressure
12
Lateral Decubitus Position
The dependent lung is better Ventilated than
the Nondependent lung, ?V/? Q still is well
matched.
Patient awake spontaneously breathing
13
Lateral Decubitus Position
14
Lateral Decubitus Position
15
Patient anesthetized ,mechanically ventilated
,chest open
16
One Lung Ventilation

• The principle physiologic change of OLV is the
  redistribution of lung perfusion between the
  ventilated (dependent) and blocked (nondependent)
  lung
• Many factors contribute to the lung perfusion,
  the major determinants of them are hypoxic
  pulmonary vasoconstriction, HPV and gravity.

17
Hypoxic pulmonary vasoconstriction

• HPV is a widely conserved, homeostatic, vasomotor
  response of precapillary smooth muscle in the PAs
  to alveolar hypoxia. HPV mediates ?V/?Q matching
  and, by reducing shunt fraction, optimizes
  systemic pO2.

18
One Lung Ventilation

• Reduces the surface area available for gas
  exchange
• Reduced arterial oxygen tension

Maintaining oxygenation and elimination of
carbon dioxide is the greatest challenge
19
(No Transcript)
20
Monitoring

• Use of Monitoring to Detect and Diagnose
  Intraoperative Events
• Respiration
• Oxygenation
• Ventilation
• Cardiovascular function

21
Respiration
22
Oxygenation
23
Ventilation
24
Cardiovascular function

• Electrocardiography
• Arrhythmia, ischemia
• Intraarterial catheter
• Hypotension or hypertension
• Arterial compression

25
Cardiovascular function

• Pulmonary artery catheter
• Pulmonary hypertension, filling pressures,
  assess
• cardiac performance
• SvO2
• Adequacy of cardiac output

26
Cardiovascular function

• Transesophageal Echocardiography
• Ischemia, volume status, right ventricular
  dysfunction

27
Tiered Monitoring System of Thoracic Surgery
Failure to check the equipment properly before
induction of anesthesia is responsible for 22
of the critical incidents that occur during
anesthesia
28
Tiered Monitoring System of Thoracic Surgery

• Healthy patients
  no special intraopertive conditions
• Sick patients
  special intraopertive conditions

Tier I
Procedure
Patient
29
Tier I Essential monitors used in all patients
30
Fibro-optic Bronchoscope
31
Tiered Monitoring System of Thoracic Surgery

• Healthy patients
  no special intraopertive conditions
• Sick patients
  special intraopertive conditions

Tier II
Procedure
Patient
32
Tiered Monitoring System of Thoracic Surgery

• Healthy patients
  no special intraopertive conditions
• Sick patients
  special intraopertive conditions

Tier II
Procedure
Patient
33
Tier II Special intermittent or continuous
monitoring needs
34
Spirometry

• Spirometry is a non-invasive monitor device which
  measures volume, pressure and flow in the airway.
• These measurements may be used to construct
• a pressure-volume curve (PV) and
• a flow-volume curve (FV).
• The constructed curves will give important
  information about the peri-operative respiratory
  function.

35
Tiered Monitoring System of Thoracic Surgery

• Healthy patients
  no special intraopertive conditions
• Sick patients
  special intraopertive conditions

Tier III
Procedure
Patient
36
Tier III Advanced monitoring
37
Special considerations for PA catheter
38
Special considerations for PA catheter

• Measured values
• CVP 1-6 mm Hg (reflects right atrial pressure).
• PAP Systolic 15-30mm Hg, Diastolic 6-12mm Hg.
• PCWP 6 - 12mm Hg. Estimates left atrial heart
  pressure and left ventricular end diastolic
  pressure.
• CO 3.5 - 7.5 L/min
• Sv02  (70 - 75).  Drawn from the end of the
  pulmonary artery catheter. Used to calculate how
  well oxygen is extracted by the tissues.  

39
Special considerations for PA catheter
40
Special considerations for PA catheter

• the LDP is important with regard to pulmonary
  artery catheter monitoring in three situations.
• The catheter is in the nondependent collapsed
  lung, the measured cardiac output and mixed
  venous blood (pvo2) may be decreased.
• When the nondependent lung is ventilated with
  PEEP and the catheter is in the nondependent
  lung, Ppaw may not equal Pla.
• When the catheter is in the dependent lung, Ppaw
  will be a faithful index of Pla, even if PEEP is
  used

41
Message to Take Home
Monitors are useful adjuncts, But they alone
cannot replace Careful observation by
Anaesthesiologist.
42
(No Transcript)