bedside monitoring of tissue perfusion and oxygenation
DESCRIPTION
This presentation is about bedside monitoring of tissue oxygenation and ischemia, both clinically and with instrumentsTRANSCRIPT
BEDSIDE MONITORING BEDSIDE MONITORING OF TISSUE PERFUSION OF TISSUE PERFUSION
AND OXYGENATIONAND OXYGENATION
Dr.Tushar PatilDr.Tushar PatilMDMD
Oxygen transport involves a series of convective and diffusive
processes. Convective transport -bulk movement of oxygen in air or blood-active, energy consuming processes generating
flow Diffusive transport - passive movement of oxygen down its
concentration gradient across tissue barriers- across the extracellular matrix - depends on the oxygen tension gradient and the
diffusion distance
Capillary blood to individual cells
resting extraction ratio from capillary blood is about 25%
may increase to 70 80% during exercise Factors affecting O2 extraction from
cappilary blood1. Rate of O2 delivery to capillary2. O2-Hb dissociation relation3. Size of capillary to cellular PO2 relation4. Diffusion distance to cells5. Rate of use of O2 by cells
Tolerance to hypoxia of Tolerance to hypoxia of various tissues Tissuevarious tissues Tissue
Survival timeSurvival time
1.1. Brain<3 minBrain<3 min
2.2. Kidney and liver15-20 minKidney and liver15-20 min
3.3. Skeletal muscle60-90 minSkeletal muscle60-90 min
4.4. Vascular smooth muscle24-72 hVascular smooth muscle24-72 h
5.5. Hair and nails -Several daysHair and nails -Several days
Tissue Hypoxia in Critically Tissue Hypoxia in Critically IllIll
disordered regional distribution of blood disordered regional distribution of blood Regional and microcirculatory distribution Regional and microcirculatory distribution
of cardiac output of cardiac output endothelial, receptor, neural, metabolic, endothelial, receptor, neural, metabolic,
and pharmacological factors and pharmacological factors small resistance arterioles and small resistance arterioles and
precapillary sphinctersprecapillary sphincters shunting and tissue hypoxia despite high shunting and tissue hypoxia despite high
global oxygen delivery and mixed venous global oxygen delivery and mixed venous saturation. saturation.
reduce regional distribution, particularly reduce regional distribution, particularly to the renal and splanchnic capillary beds to the renal and splanchnic capillary beds
EFFECTS OF HYPOXIAEFFECTS OF HYPOXIA
PaO2 level approaches 55mmHg-.short PaO2 level approaches 55mmHg-.short term memory loss, euphoria and impaired term memory loss, euphoria and impaired judgment judgment
PaO2 30-50mmHg -Progressive loss of PaO2 30-50mmHg -Progressive loss of cognitive and motor functions, increasing cognitive and motor functions, increasing tachycardia tachycardia
PaO2 below 30mmHg-loss of PaO2 below 30mmHg-loss of consciousnessconsciousness
Clinical features of tissue Clinical features of tissue hypoxiahypoxia
Dyspnoea Dyspnoea Altered mental state Altered mental state Tachypnoea or hypoventilation Tachypnoea or hypoventilation Arrhythmias Arrhythmias Peripheral vasodilatation Peripheral vasodilatation Systemic hypotension Systemic hypotension Coma Coma Cyanosis (unreliable) Cyanosis (unreliable) Nausea, vomiting, and gastrointestinal Nausea, vomiting, and gastrointestinal
disturbance disturbance
Monitoring Tissue Perfusion Monitoring Tissue Perfusion and Oxygenation and Oxygenation
1.1. Clinical EvaluationClinical Evaluation
2.2. Hemodynamic MonitoringHemodynamic Monitoring
3.3. Pulse OximetryPulse Oximetry
4.4. End Tidal CO2 MonitoringEnd Tidal CO2 Monitoring
5.5. Monitoring Tissue HypoxiaMonitoring Tissue Hypoxia
6.6. Cerebral Oxygenation MonitoringCerebral Oxygenation Monitoring
Clinical EvaluationClinical Evaluation
HISTORYHISTORY-Dyspnoea-Dyspnoea-Cough-Cough-Fever-Fever-Rash-Rash-Discolouration of digits/limbs-Discolouration of digits/limbs-Palpitations-Palpitations-Altered sensorium-Altered sensorium-Convulsions-Convulsions
Clinical EvaluationClinical Evaluation
Level of ConsciousnessLevel of Consciousness Evaluation of Peripheral & Central Evaluation of Peripheral & Central
PulsesPulses Capillary Refill TimeCapillary Refill Time CyanosisCyanosis Respiratory Rate & PatternRespiratory Rate & Pattern Blood PressureBlood Pressure Systemic ExaminationSystemic Examination
Hemodynamic MonitoringHemodynamic Monitoring
Arterial Blood PressureArterial Blood Pressure
-Non Invasive-Non Invasive
-Invasive-Invasive Central Venous Pressure MonitoringCentral Venous Pressure Monitoring Pulmonary Artery Catheterisation Pulmonary Artery Catheterisation Measuring Cardiac OutputMeasuring Cardiac Output
Monitoring arterial pressure
Organ perfusion depends on the organ metabolic demand ,perfusion pressure,local vasomotor tone and cardiac output
tissue perfusion is maintained through ‘‘autoregulation’’
Organ perfusion pressure cannot be measured directly at the bedside
As a surrogate for tissue perfusion pressure, arterial blood pressure is monitored.
Noninvasive measurements of arterial pressure
can be determined either manually or by oscillometric method .
Oscillometric devices, determine MAP and then provide readings for systolic and diastolic pressures.
Oscillometric devices tend to underestimate systolic and overestimate diastolic blood pressure
noninvasive measurements less reliable with marked hypovolemia or abnormal cardiac function.
Oscillometric measurements also limited by cycling delay of the device.
Arterial CatheterisationArterial Catheterisation
INDICATIONS ABSOLUTE- As a guide to synchronization of intra-
aortic balloon counter pulsation PROBABLE-1. Guide to management of potent vasodilator drug
infusions2. Guide to management of potent vasopressor drug
infusion3. As a port for the rapid and repetitive sampling 4. As a monitor of cardiovascular deterioration in
patients
Arterial CatheterisationArterial Catheterisation
USEFUL APPLICATIONS Differentiating cardiac tamponade
(pulsus paradoxus) from respiration-induced swings in systolic BP
Differentiating hypovolemia from cardiac dysfunction as the cause of hemodynamic
Arterial Catherisation
COMPLICATIONS - temporary occlusion - hematomas - Serious ischemic damage - sepsis - pseudoaneurysm
Central venous pressure monitoring
Pressure in the large central veins proximal to the right atrium relative to atmosphere.
METHODS- central venous line / Swan-Ganz
catheter with distal tip connected to manometer/ pressure transducer
- noninvasively as jugular venous pressure
Factors affecting measured CVP
1.Central venous blood volume Venous return/cardiac output Total blood volume Regional vascular tone2.Compliance of central compartment Vascular tone RV compliance Myocardial disease Pericardial disease Tamponade3.Tricuspid valve disease Stenosis Regurgitation
Factors affecting measured CVP
4.Cardiac rhythm Junctional rhythm Atrial fibrillation (AF) Atrio ventricular (A-V) dissociation5.Reference level of transducer Positioning of patient6.Intrathoracic pressure Respiration IPPV Positive end-expiratory pressure (PEEP) Tension pneumothorax
Limitations of CVPLimitations of CVP
Being wrongly used as a parameter/ goal for replacement of intravascular volume
The validity as index of RV preload nonexistent
Poor correlation with cardiac index, stroke volume, left ventricular end-diastolic
volume, and right ventricular end-diastolic volume
Pulmonary artery catheterization
Developed in the 1940s and later refined by Swan and Ganz in 1970
INDICATIONSINDICATIONS Diagnostic Diagnostic
– Diagnosis of shock states Diagnosis of shock states – high- versus low-pressure pulmonary edema high- versus low-pressure pulmonary edema – primary pulmonary hypertension (PPH) primary pulmonary hypertension (PPH) – valvular disease, intracardiac shunts, cardiac tamponade, and valvular disease, intracardiac shunts, cardiac tamponade, and
pulmonary embolus (PE) pulmonary embolus (PE) – Monitoring complicated AMI Monitoring complicated AMI – hemodynamic instability after cardiac surgery hemodynamic instability after cardiac surgery
Therapeutic Therapeutic - Aspiration of air emboli- Aspiration of air emboli
PACPAC
CONTRAINDICATIONSCONTRAINDICATIONS Tricuspid or pulmonary valve Tricuspid or pulmonary valve
mechanical prosthesis mechanical prosthesis Right heart mass (thrombus and/or Right heart mass (thrombus and/or
tumor) tumor) Tricuspid or pulmonary valve Tricuspid or pulmonary valve
endocarditisendocarditis
PACPACMEASURED PARAMETERSMEASURED PARAMETERS1.1. Central Venous PressureCentral Venous Pressure2.2. Pulmonary Capillary Wedge PressurePulmonary Capillary Wedge Pressure3.3. Cardiac IndexCardiac Index4.4. Stroke Volume IndexStroke Volume Index5.5. LV Stroke Work IndexLV Stroke Work Index6.6. RVSWIRVSWI7.7. RV Ejection FractionRV Ejection Fraction8.8. RV End Diastolic VolumeRV End Diastolic Volume9.9. Systemic Vascular Resistance IndexSystemic Vascular Resistance Index10.10. Pulmonary Vascular Resistance IndexPulmonary Vascular Resistance Index11.11. Mixed Venous O2 SaturationMixed Venous O2 Saturation12.12. O2 deliveryO2 delivery13.13. O2 uptakeO2 uptake14.14. O2 exraction RatioO2 exraction Ratio
Complications of PACComplications of PAC Venous access complicationsVenous access complications - include arterial puncture - include arterial puncture - hemothorax - hemothorax - Pneumothorax - Pneumothorax ArrhythmiasArrhythmias - PVCs or nonsustained VT- PVCs or nonsustained VT - Significant VT or ventricular fibrillation - Significant VT or ventricular fibrillation Right bundle-branch block (RBBB) Right bundle-branch block (RBBB) PA rupture PA rupture PAC related infection PAC related infection Pulmonary infarction Pulmonary infarction
Measuring Cardiac OutputMeasuring Cardiac Output
1. Pulmonary Artery Catheter1. Pulmonary Artery Catheter2. Pulse Contour Analysis2. Pulse Contour Analysis -Lithium dilution-Lithium dilution -Transpulmonary Thermodilution-Transpulmonary Thermodilution -Without diluion calibration-Without diluion calibration3. CO2 Rebreathing3. CO2 Rebreathing4. Trans thoracic Electrial Bioimpedence4. Trans thoracic Electrial Bioimpedence5. Trans Thoracic Echo5. Trans Thoracic Echo6. Esophageal Doppler Monitoring6. Esophageal Doppler Monitoring
Pulse Oximetry
PRINCIPLE Displayed readings determined primarily by two
components:1. The different absorption spectra of oxyhemoglobin
and deoxyhemoglobin at different wavelengths 2. Pulsatile arterial blood Probe (finger, ear, or forehead) contains two light-
emitting diodes that emit light at 660 nm and 940 nm.
Photoreceptor receives light, and compares absorption two wavelengths,
Pulse Oximetry
APPLICATIONSAPPLICATIONS indicated in circumstance where indicated in circumstance where
hypoxaemia May occur. hypoxaemia May occur. should be included in the routine vital should be included in the routine vital
signs. . signs. . continuous monitoring.continuous monitoring. pattern of oxygenation can be recorded.pattern of oxygenation can be recorded. can replace arterial blood gas analysis in can replace arterial blood gas analysis in
cases where assessment of oxygenation is cases where assessment of oxygenation is indication.indication.
Regulation of oxygen therapyRegulation of oxygen therapy Testing adequecy of circulation Testing adequecy of circulation
Pulse OximetryPulse Oximetry
Improving oximeter signals Improving oximeter signals • Warm and rub the skin Warm and rub the skin • Apply a topical vasodilator Apply a topical vasodilator • Try a different probe site, especially Try a different probe site, especially
the ear the ear • Try a different probe Try a different probe • Avoid motion artefactAvoid motion artefact• Use a different machine Use a different machine
Pulse OximetryPulse Oximetry PITFALLS1. Dyshemoglobinemias2. Poor function wiyh poor performance3. Difficulty in detecting high oxygen partial
pressures4. Delayed detection of hypoxic events5. Erratic performance with irregular rhythms6. Nail polish and coverings7. Loss of accuracy at low values8. Electrical interference9. Failure to detect hypoventilation
Monitoring ventilation using end-tidal carbon dioxide
provides information regarding alveolar ventilation.
PetCO2 - concentration of carbon dioxide at end expiration .
measured in both mechanically ventilated and spontaneously breathing patients.
displayed as either numerical value (capnometry) or as a graphic waveform plotted against time (capnography).
PetCO2 underestimatesPaCO2 by 2 to 5 mm Hg because of the influence of dead space ventilation
relationship between PetCO2 and PaCO2 is unreliable in critically ill patients.
End Tidal Carbon DioxideEnd Tidal Carbon Dioxide
APPLICATIONS Confirming endotracheal tube placement detecting endotracheal tube dislodgment detecting ventilator malfunction assessing the success of
cardiopulmonary resuscitation evaluation of weaning from mechanical
ventilation determining the optimal level of PEEP
End Tidal CO2End Tidal CO2
sudden loss of the capnogram waveform –ET obstruction -extubation - ventilator malfunction –cardiac arrest sudden drop of the waveform -partial obstruction of ET -an airway leak -hypotension
End Tidal CO2End Tidal CO2
Capnography can be used to monitor patients in whom hypercarbia may be detrimental
PetCO2 values greater than 40 mm Hg correlate with equal or higher value of PaCO2
Elevated PetCo2 indicate sthe need for alterations in management
Monitoring Tissue Hypoxia Global markers of tissue hypoxia - serum lactate -central venous oxygen saturation (ScvO2)
Monitoring regional hypoxia -Sublingual Capnometry –Gastric Tonometry - Orthogonal Polarization Spectroscopy (OPS) - Near Infra Red Spectroscopy (NIRS) -Trans cutaneous Oxygen Tension -Resonance Raman Spectroscopy
Serum LactateSerum Lactate byproduct of anaerobic metabolism, resulting from
the inabilityof pyruvate to enter the Krebs cycle. The normal serum value - less than 2 mmol/L. lactate levels above 4mmol/L strongly associated
with worse outcome. more important is the time to normalization of
lactateLevels- ‘‘lactate clearance time.’’ Prolonged lactate clearance time(>48hrs)-
significantly higher rates of infection, organ dysfunction, and death
Better survival correlates with a lactate clearance time <24 hrs.
Central venous oxygen saturation
Mixed venous oxygen saturation (SvO2) - a measure of tissue hypoxia. o
Obtained with pulmonary artery catheter.
FACTORS INFLUENCING SvO2- arterial oxygen saturation- hemoglobin concentration- cardiac output- tissue oxygen consumption.- NORMAL VALUES- 70% to 75%. - Values below 60% indicate cellular oxidative impairment- values below50% associated with anaerobic metabolism
pulmonary artery catheters not placed routinely ScvO2 - surrogate For SvO2
ScvO2ScvO2 venous oxygen saturation near the junction of the
superior vena cava and right atrium. obtained from subclavian or internal jugular
central venous catheter. Because ScvO2 neglects venous return from the
lowerbody, values for ScvO2 typically are 3% to 5% less
than SvO2 values < 65% -ongoing oxidative impairment. values > 80% - cellular dysfunction with impaired
oxygen consumption. - seen in late stages of shock
To be used in context with other markers of tissue perfusion (eg, lactate).
Sublingual capnometry studies perfusion of the splanchnic circulation. sensor placed under the tongue measures partial pressure of carbon dioxide in
the sublingual tissue (PslCO2). Normal values for PslCO2 - 43 to 47 mmHg PslCO2 >70 mm Hg - correlates with elevated
arterial lactate levels more important is the ‘‘PslCO2 gap.’’-
difference between PslCO2 and PaCO2 A PslCO2 gap of> 25 mm Hg identifies patients
at a high risk of mortality.
Gastric TonometryGastric Tonometry
Offers an index of aerobic metabolism in Offers an index of aerobic metabolism in gut mucosa.gut mucosa.
Based on increase in tissue CO2 Based on increase in tissue CO2 A balloon in stomach,measures A balloon in stomach,measures
intramucosal pCO2intramucosal pCO2 Using this and arterial (HCO3), gastric Using this and arterial (HCO3), gastric
intramucosal PH is calculatedintramucosal PH is calculated
Orthogonal polarization spectroscopy
uses polarized light to visualize the microcirculation directly.
hemoglobin absorbs polarized light real-time images reflected to videomicroscope functional capillary density measured. sensitive marker of tissue perfusion and an indirect
measurement of oxygen delivery. Tissues evaluated- oral mucosa, sublingual mucosa, rectal
mucosa,and vaginal mucosa.
LIMITNG FACTORS- -movement artifacts -presence of saliva -observer related bias
Near-infrared spectroscopy measures the concentrations of hemoglobin, oxygen
saturation,and cytochrome aa3 Cytochrome aa3- final receptor in the electron transport
chain - responsible for 90% cellular O2 consumption
- remains in a reduced state during hypoxia used primarily to evaluate the perfusion of skeletal muscles.
PROBLEMS-signal contamination by light scatter-variable interpretations of the data-lack of a reference standard for comparison
Transcutaneous oxygen tension
measure transcutaneous oxygen or carbon dioxide.
Use heated probes placed on the skin
•markers of regional tissue hypoperfusion increased mortality in patients with low transcutaneous oxygen or high CO2
•LIMITATIONS-Tissue trauma from probe insertion,- thermal injury if probes are not moved every4 hours - lack of established critical values to guide resuscitation.
Cerebral Perfusion and Oxygenation monitoring
1. Jugular venous bulb oximetry2. Direct brain tissue oxygen tension3. Near inrared spectroscopy4. Cerebral Microdialysis5. Cerebral Blood Flow Monitoring6. Oxygen-15 PET
Jugular venous oxygen saturation(SjvO2)
Retrograde placement of jugular venous catheter with oximeter
cannulate dominant IJV catheter tip positioned in jugular bulb compatible with MRI. SjvO2 - result of the difference between cerebral oxygen
delivery (supply) and cerebral metabolic rate of oxygen (demand)
Low SjvO2 (!50% for O10 minutes) -hypoperfusion / increased . cerebral metabolism.
APPLICATIONS - comatose patients (GCS <8) -treatment of SAH - - neurosurgical procedures
SjvO2SjvO2LIMITATIONS - changes in arterial oxygen content- hemodilution- prone position of catheter- necessity for frequent calibrations- infection- increase in ICP- thrombosis- arterial Puncture- pneumothorax - reflects global cerebral oxygenation and does not detect
regional ischemia in smaller regions ipsilateral or in contralateral hemisphere
Brain tissue oxygen pressure(PBO2)
Small flexible microcatheter inserted into brain parenchyma. marker of the balance between regional oxygen supply and
use. ICP, brain temperature (Licox, Integra Neurosciences) or tissue
partial pressure of carbon dioxide (PBCO2) and pH (Neurotrend, Johnson & Johnson) can be monitored
Licox device uses polarographic technique by Clark electrode Neurotrend uses ‘‘optimal luminescence’’ catheter should pass through gray matter into white matter tunneled after craniotomy or placed through a double or triple lumen bolt measured tissue volume 17 mm3. PBO2 levels highest in dense population of neurons and lower
in white matter PBO2 and amplitude of changes lower with Neurotrend than
Licox compatible with MRI
Near infrared spectroscopy monitoring of transmittance across the brain at
two or more wavelengths optical attenuation of the spectra converted into
changes of cerebral oxygenation methods include time-resolved, spatially
resolved, and phase-resolved spectroscopy INVOS system provides a numerical value for
oxygen saturation using rSO2 normal range-60-80% NIRO oximeters present values for oxygenated
and total Hb concentration, cytochrome aa3, and a tissue oxyge index
NISNIS
APPLICATIONS detection of changes during carotid cross-
clamping during carotid endarterectomy & cardiac surgery
to detect cerebral vasospasm causing delayed cerebral ischemic deficit after SAH
assessment of perfusion reductions in stroke Reconstruction of a three-dimensional image
using optical tomography attractive because applied by attaching pads to
the forehead or other regions of interest.
NISNIS
LIMITATIONS
limited and variable penetration of infrared light through the skull (2–3 mm, limited to gray matter)
contamination by extra- and intracranial sources (mixture of capillary, venous,and arterial blood), and uniform distribution of infrared light in the CSF layer.
degree of scatter unpredictable inconsistent impact of monitoringof decreased oxygenation on neurologic outcome
Cerebral Microdialysis bedside monitor to provide on-line analysis of brain tissue
biochemistry during neurointensive care. The principles and clinical
double-lumen probe, lined at it tip with dialysis membrane. perfused by an inlet tube with fluid isotonic to the tissue
interstitium perfusate passes along the membrane before exiting
collecting chamber. catheter acts as an artificial blood capillary. Measures microdialysate concentrations of glucose, lactate,
pyruvate, glycerol, and glutamateThe concentration of these substances in the microdialysate
does not correspond to their true extracellular fluid concentration
proportion of the extracellular fluid concentration the ‘‘relative recovery”
Brain Tissue Brain Tissue O2 monitorO2 monitor
MD data MD data displaydisplay
MD Bedside MD Bedside AnalyserAnalyser
Jugular Venous Jugular Venous Saturation Saturation
MonitorMonitor
Applications of MDApplications of MD Most clinical experience with TBI and SAH Severe cerebral hypoxia /ischemia associated
with marked increases in the lactate-pyruvate ratio
Ratio greater than 20 to 25 associated with poor outcome
Glycerol is a marker of ischemic cell damage Increased MD glycerol concentrations associated
with poor outcome Increased excitatory amino acids and reduced
brain ECF glucose associated with metabolic catastrophes after acute brain injury.
Cerebral Blood Flow Cerebral Blood Flow MonitoringMonitoring
Kety-Schmidt method Radioactive tracer techniques Continuous quantitative cerebral
blood flow monitoring-Laser Doppler flowmetry -Thermal diffusion flowmetry Double-indicator dilution technique Transcranial Doppler
ultrasonography
NeuroimagongNeuroimagong
[18F]2-deoxy-D-glucose PET oxygen-15 PET SPECT Xenon-enhanced CT scanning perfusion CT Perfusion weighted imaging (PWI)
THANKSTHANKS