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