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Monitoring During Thoracic Anesthesia. Outline. Introduction Physiological Aspects Monitoring Requirements. Introduction. Thoracic anesthesia is challenging. Patient. Procedure. Physiological Aspects. Principles of Ventilation and Perfusion. - PowerPoint PPT Presentation
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IntroductionIntroduction
Physiological Aspects Physiological Aspects
Monitoring RequirementsMonitoring Requirements
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Thoracic anesthesia is challengingThoracic anesthesia is challenging
Patient Patient Procedure Procedure
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““V" - ventilation V" - ventilation - the air which reaches the lungs
"Q" - perfusion "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. 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 < 0.8, there is a VQ mismatch caused by poor ventilation
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An area with no ventilation (and thus a V/Q of zero) is termed "shunt." "shunt."
An area with no perfusion (and thus a V/Q of infinity) is termed “dead space”“dead space”
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A change in volume divided by a change in transpulmonary pressure.
(CL = ΔV / ΔPL)(CL = ΔV / ΔPL)
A typical value of compliance is 200 ml/cm H20
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Page 11 Pulmonary blood flow distribution relative to the Pulmonary blood flow distribution relative to the alveolar pressurealveolar pressure
Ven
tilation
Ven
tilation
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Patient awake spontaneously breathing
The dependent lung is betterVentilated than the
Nondependent lung,˙V/˙ Q still is well matched.
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The principle physiologic change of Oprinciple 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 hypoxic pulmonary vasoconstriction, HPV and gravity. vasoconstriction, HPV and gravity.
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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.
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Reduces the surface area available for gas exchangeReduces the surface area available for gas exchange
Reduced arterial oxygen tensionReduced arterial oxygen tension
Maintaining oxygenationMaintaining oxygenation and and
elimination of carbon dioxide elimination of carbon dioxide is the greatest challengeis the greatest challenge
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Use of Monitoring to Detect and Diagnose Use of Monitoring to Detect and Diagnose Intraoperative EventsIntraoperative Events
RespirationRespiration
OxygenationOxygenation
VentilationVentilation
Cardiovascular functionCardiovascular function
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ElectrocardiographyElectrocardiography
Arrhythmia, ischemia
Intraarterial catheterIntraarterial catheter
Hypotension or hypertension
Arterial compression
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Pulmonary artery catheterPulmonary artery catheter
Pulmonary hypertension, filling pressures, assess
cardiac performance
SvO2SvO2
Adequacy of cardiac output
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Transesophageal EchocardiographyTransesophageal Echocardiography
Ischemia, volume status, right ventricular dysfunction
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Failure to check the equipment properlyFailure to check the equipment properly before induction of anesthesia isbefore induction of anesthesia is
responsible for 22% of theresponsible for 22% of the critical incidents that occur during anesthesiacritical incidents that occur during anesthesia
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Healthy patients no special intraopertive conditionsHealthy patients no special intraopertive conditions
Sick patients special intraopertive conditionsSick patients special intraopertive conditions
Tier ITier I
ProcedureProcedure PatientPatient
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Gas exchange
Airway mechanics
Endotracheal tube position
PA pressures
Cardiovascul-ar status
Color of tissues and shed blood Spo2, PETCO2
Feel of the breathing bag, stethoscope,PIP, PETCO2
EBBS Ballotable balloon in SSN, FOB afterplaced in LDP
Not measured NIBP, pulse oximeter waveform, ECG, PETco2esophageal stethoscope,± CVP, ± invasive arterialpressure monitoring
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Healthy patients no special intraopertive conditionsHealthy patients no special intraopertive conditions
Sick patients special intraopertive conditionsSick patients special intraopertive conditions
Tier IITier II
ProcedureProcedure PatientPatient
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Healthy patients no special intraopertive conditionsHealthy patients no special intraopertive conditions
Sick patients special intraopertive conditionsSick patients special intraopertive conditions
Tier IITier II
ProcedureProcedure PatientPatient
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Gas exchange
Airway mechanics
Endotracheal tube position
PA pressures
Cardiovascul-ar status
As above plus frequent ABG studies
As above plus spirometry. Individual and whole-lungcompliance
FOB to verify tube position while in supine position, as well as in the LDP
Measure Ppa if lobectomy or lung resection
As above, plus invasive arterial pressure monitoring, + CVP, + PA catheter (if poor EF, PA,HTN), ± TEE
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SpirometrySpirometry is a non-invasive monitor device which measures volume, pressure and flow 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.peri-operative respiratory function.
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Healthy patients no special intraopertive conditionsHealthy patients no special intraopertive conditions
Sick patients special intraopertive conditionsSick patients special intraopertive conditions
Tier IIITier III
ProcedureProcedure PatientPatient
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Gas exchange
Airway mechanics
Endotracheal tube position
PA pressures
Cardiovascul-ar status
As above plus Qs/Qt, VD/Vtfrequent VBGs
As above plus airway resistance
As above plus frequent rechecksto verify position
Measure PA ,Q , PVR , SVR, Dao2 –Dvo2
As above plus PA , TEE
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Measured values:Measured values:
CVPCVP: 1-6 mm Hg (reflects right atrial pressure).
PAPPAP: Systolic 15-30mm Hg, Diastolic 6-12mm Hg.
PCWPPCWP: 6 - 12mm Hg. Estimates left atrial heart pressure and left ventricular end diastolic pressure.
COCO: 3.5 - 7.5 L/min
Sv02:Sv02: (70 - 75%). Drawn from the end of the pulmonary artery catheter. Used to calculate how well oxygen is extracted by the tissues.
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the LDP is important with regard to pulmonary artery catheter the LDP is important with regard to pulmonary artery catheter monitoring in three situationsmonitoring in three situations.
The catheter is in the nondependent collapsed lung, the measured cardiac output and mixed venous blood (pvo2) may be decreased.decreased.
When the nondependent lung is ventilated with PEEP and the catheter is in the nondependent lung, Ppaw may not equal , Ppaw may not equal Pla.Pla.
When the catheter is in the dependent lung, Ppaw will be a Ppaw will be a faithful index of Plafaithful index of Pla, even if PEEP is used
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Monitors are useful adjuncts, But they alone Monitors are useful adjuncts, But they alone cannot replacecannot replace
Careful observation by AnaesthesiologistCareful observation by Anaesthesiologist.
