Dr. Sushil

PERIOPERATIVE MONITORING

Dr. Chavi Sethi (M.D.)

Speaker

Coordinator

Standards for Basic Anesthetic Monitoring

The AmericanSociety of Anesthesiologists (ASA) guidelines for basic anesthesia monitoring

Standard I- Qualified anesthesia personnel shall be present in the room throughout the conduct of all general anesthetics, regional anesthetics, and monitored anesthesia care

Standard II- During all anesthetics, the patient's oxygenation, ventilation, circulation, and temperature shall be continually evaluated

Introduction

The most primitive method of monitoring the patient 25 years ago was continuous palpation of the radial pulsations throughout the operation!!

What is the value of knowing this? To understand & appreciate the value of clinical monitoring.

RULE: your clinical judgement/assessment is much BETTER & much more VALUABLE than the digital monitor.

To appreciate that modern monitors have made life much easier for us. They are present to make monitoring easier for us NOT to be omitted or ignored.

IntroductionWhy do we need intraoperative monitoring??? To maintain the normal pt physiology & homeostasis

throughout anesthesia and surgery: induction, maintenance & recovery as much as possible. To ensure the well being of the pt.

Surgery is a very stressful condition → severe sympathetic stimulation, HTN, tachycardia, arrhythmias.

Most drugs used for general & regional anesthesia cause hemodynamic instability, myocardial depression, hypotension & arrhythmias.

Under GA the pt may be hypo or hyperventilated and may develop hypothermia.

Blood loss → anemia, hypotension. So it is necessary to recognise when the pt is in need of blood transfusion (transfusion point).

monitoring: - Introduction.....The FOUR BASIC Monitors: We are NOT authorised to start a surgery in the

absence of any of these monitors:ECG.SpO2: arterial O2 saturation.Blood Pressure: NIBP (non-invasive), IBP (invasive).± [Capnography].

The most critical 2 times during anesthesia are: INDUCTION - RECOVERY.

Exactly like “flying a plane” induction (= take off) & recovery (= landing). The aim is to achieve a smooth induction & a smooth recovery & a smooth intraoperative course.

Cardiovascular Monitoring

Just as inspection, palpation, and auscultation are the cornerstones of physical examination of the cardiovascular system, these same clinical procedures are fundamental elements of perioperative cardiovascular monitoring.

Palpation of the pulse and its rate and character should not be forgotten in the perioperative setting.

Blood Pressure Monitoring- Like the heart rate, blood pressure is a fundamental cardiovascular vital sign

and a critical part of monitoring anesthetized or seriously ill patients. The importance of monitoring this vital sign is underscored by the fact that

standards for basic anesthetic monitoring mandate measurement of arterial blood pressure at least every 5 minutes in all anesthetized patients.

Techniques for measuring blood pressure fall into two major categories: indirect cuff devices and direct arterial cannulation and pressure transduction

Indirect Measurement of Arterial Blood Pressure Indications-The use of any anesthetic, no matter how "trivial," is an absolute

indication for arterial blood pressure measurement. The techniques and frequency of pressure determination depend on the patient's condition and the type of surgical procedure. An oscillometric blood pressure measurement every 3–5 min is adequate in most cases.

Contraindications- Although some method of blood pressure measurement is mandatory, techniques that rely on a blood pressure cuff are best avoided in extremities with vascular abnormalities (eg, dialysis shunts) or with intravenous lines.

Techniques 1)Palpation- Systolic blood pressure can be determined by

(1) locating a palpable peripheral pulse,

(2) inflating a blood pressure cuff proximal to the pulse until flow is occluded,

(3) releasing cuff pressure by 2 or 3 mm Hg per heartbeat, and

(4) measuring the cuff pressure at which pulsations are again palpable. This method tends to underestimate systolic pressure, however, because

of the insensitivity of touch and the delay between flow under the cuff and distal pulsations. Palpation does not provide a diastolic or MAP.

Palpation…….RULE: YOUR clinical judgement is always superior to the

monitor. Must check peripheral pulse volume from time to time (Radial A, or Dorsalis Pedis A, or Superficial Temporal A) regularly every 10 minutes.Palpation of Radial A → systolic BP ˃ 90 mmHg.Palpation of Dorsalis Pedis A → systolic BP ˃ 80

mmHg.Palpation of Superficial Temporal A → systolic BP ˃

80 mmHg. i.e If Radial A pulsations are lost = systolic BP is < 90

mmHg. If dorsalis pedis & superficial temporal pulsations are

lost = systolic BP is < 80 mmHg. Check pt colour for pallor: lips, tongue, nails,

conjunctiva.

2)Auscultation

How to attach/apply: Correct cuff size: width of the cuff should be 1.5 times limb

diameter and should occupy at least 2/3 of the arm. 2 cuff sizes for adult: blue: for most adult individuals (60-90 Kg),

red: for morbid obese. Selection of appropriate cuff size is important because a tight

cuff leads to false high readings, while a Loose cuff gives false Low readings.

Is better applied directly to the arm (remove sleeve). May also be applied to the forearm in very obese individuals. May be applied to the calf if the arms are not accessible during surgery.

Correct positioning: cuff is positioned with the hoses over the brachial artery.

Usually attached to the limb opposite the IV line & pulse oximeter. Unless the pt is performing hand or arm or breast surgery, the BP cuff is attached with the IV line and saturation probe on the same side.

AVOID attaching it to an arm with A-V graft (for renal dialysis) → damage of AV graft, & inaccurate measurements.

Inflation of a blood pressure cuff to a pressure between systolic and diastolic pressures will partially collapse an underlying artery, producing turbulent flow and the characteristic Korotkoff sounds.

The pressure at which the first Korotkoff sound is heard is generally accepted as systolic pressure (phase I). The character of the sound progressively changes (phases II and III), becomes muffled (phase IV), and is finally absent (phase V). Diastolic pressure is recorded at phase IV or V. However, phase V may never occur in certain pathophysiologic states such as aortic regurgitation.

3)Oscillometry(automated NIBP devices )-

Arterial pulsations cause oscillations in cuff pressure.

These oscillations are small if the cuff is inflated above systolic pressure.

When the cuff pressure decreases to systolic pressure, the pulsations are transmitted to the entire cuff and the oscillations markedly increase.

Maximal oscillation occurs at the MAP, after which oscillations decrease.. Automated blood pressure monitors electronically measure the pressures at which the

oscillation amplitudes change .

Systolic pressure is typically identified as the pressure at which pulsations are increasing and are at 25% to 50% of maximum

Diastolic pressure is the most unreliable oscillometric measurement and is commonly recorded when the pulse amplitude has declined to a small fraction of its peak value

3)Oscillometry(automated NIBP devices )…….

Gives readings for: systolic BP, diastolic BP & MAP: Systolic/ diastolic (mean).

Value: to avoid and manage extremes of hypotension & HTN. Systolic BP-Diastolic BP- MAP.

Avoid ↓ MAP < 60 mmHg (for cerebral & renal perfusion) & avoid ↓ diastolic pressure < 50 mmHg (for coronary perfusion).

4)Doppler Probe When a Doppler probe is substituted for the anesthesiologist's finger,

arterial blood pressure measurement becomes sensitive enough to be useful in obese patients, pediatric patients, and patients in shock

Based on Doppler effect -Doppler probe transmits an ultrasonic signal that is reflected by underlying tissue.

difference between transmitted and received frequency causes the characteristic swishing sound, which indicates blood flow.

Positioning the probe directly above an artery is crucial, since the beam must pass through the vessel wall.

only systolic pressures can be reliably determined with the Doppler technique.

5)Arterial Tonometry - Arterial tonometry measures beat-to-beat arterial blood pressure by sensing the pressure required to partially flatten a superficial artery that is supported by a bony structure (eg, radial artery).

The contact stress between the transducer directly over the artery and the skin reflects intraluminal pressure.

Continuous pulse recordings produce a tracing very similar to an invasive arterial blood pressure waveform.

Invasive Arterial Blood Pressure Monitoring…..Indications- Indications for invasive arterial blood pressure monitoring by

catheterization of an artery include induced hypotension, anticipation of wide blood pressure swings, end-organ disease necessitating precise beat-to-beat blood pressure regulation, and the need for multiple arterial blood gas analyses

Contraindications- If possible, catheterization should be avoided in arteries without documented collateral blood flow or in extremities where there is a suspicion of preexisting vascular insufficiency (eg, Raynaud's phenomenon).

Techniques & Complications Selection of Artery for Cannulation- Several arteries are

available for percutaneous catheterization

Invasive Arterial Blood……

1)The radial artery- is commonly cannulated because of its superficial location and collateral flow. Five percent of patients, however, have incomplete palmar arches and lack adequate collateral blood flow

Allen's test - is a simple, but not very reliable, method for determining the adequacy of ulnar collateral circulation.

In this test, the patient exsanguinates his or her hand by making a fist. then operator occludes the radial and ulnar arteries with fingertip pressure, the patient relaxes the blanched hand.

Collateral flow through the palmar arterial arch is confirmed by flushing of the thumb within 5 s after pressure on the ulnar artery is released.

Delayed return of normal color (5–10 s) indicates an equivocal test or insufficient collateral circulation (>10 s).

Alternatively, blood flow distal to the radial artery occlusion can be detected by palpation, Doppler probe, plethysmography, or pulse oximetry. Unlike Allen's test, these methods of determining the adequacy of collateral circulation do not require patient cooperation.

Patient Selection: Allen Test

To assess contribution of radial and ulnar arteries in blood supplyof hand:make chenked fist and occlude both radial and ulnar arteries. When fist is open skin is pale, colour should return rapidly on release ofvulnar artery as shown in the above figures. An obvious delay after releasing ulnar artery indicates that the radial aretry is dominant and that procedures that Might damage the radial artery (eg cannulation) should be avoided.

Alternative to the Allen test:: Oxymeter

Only radial artery compression

No significative variation

Invasive Arterial Blood Pressure Monitoring….Ulnar artery- catheterization is more difficult because of the artery's deeper

and more tortuous course. Because of the risk of compromising blood flow to the hand, this would not normally be considered if the ipsilateral radial artery has been punctured but unsuccessfully cannulated

brachial artery- is large and easily identifiable in the antecubital fossa. Its proximity to the aorta provides less waveform distortion. However, being near

the elbow predisposes brachial artery catheters to kinking.

femoral artery- is prone to pseudoaneurysm and formation of atheroma but often provides an excellent access.

The femoral site has been associated with an increased incidence of infectious complications and arterial thrombosis. Aseptic necrosis of the head of the femur is a rare but tragic complication of femoral artery cannulation in

children.

dorsalis pedis and posterior tibial arteries- are at some distance from the aorta and therefore have the most distorted waveforms. Modified Allen's tests can be performed to document adequate collateral flow around these arteries

Invasive Arterial Blood Pressure Monitoring….axillary artery- is surrounded by the axillary plexus, and nerve damage can

result from a hematoma or traumatic cannulation. Air or thrombi can quickly gain access to the cerebral circulation during retrograde flushing of the left

axillary artery.

Technique of Radial Artery Cannulation -

1-preparing the skin with a bactericidal agent2- Supination and extension of the wrist provide optimal exposure of the radial artery3- needle through the skin at a 45° angle

4 )18-, 20-, or 22-gauge catheter over a needle

Radial artery catheter

Arterial pressure monitoring systems have a number of components, beginning with the intra-arterial catheter and including extension tubing, stopcocks, in-line blood sampling

set, pressure transducer, continuous-flush device, and electronic cable connecting the bedside monitor and waveform display screen

Invasive Arterial Blood Pressure Monitoring…. The flush device provides a continuous, slow (1 to 3 mL/hr) infusion of saline to

purge the monitoring system and prevent thrombus formation within the arterial cathete

A dilute concentration of heparin (1 to 2 units heparin/mL saline) has been added to the flush solution to further reduce the incidence of catheter thrombosis, but this practice increases the risk for heparin-induced thrombocytopenia and should be

avoided. Normal Arterial Pressure Waveforms- The systemic arterial pressure

waveform results from ejection of blood from the left ventricle into the aorta during systole, followed by peripheral arterial runoff of this stroke volume during diastole

The systolic components follow the ECG R wave and consist of a steep pressure upstroke, peak, and decline and correspond to the period of left ventricular systolic ejection.

The downslope of the arterial pressure waveform is interrupted by the dicrotic notch, then continues its decline during diastole after the ECG T wave, and reaches its nadir at end-diastole

The dicrotic notch recorded directly from the central aorta is termed the incisura

Normal Arterial Pressure Waveforms-

Normal arterial blood pressure waveform and its relationship to the electrocardiographic R wave. 1, Systolic upstroke; 2, systolic peak pressure; 3, systolic decline; 4, dicrotic notch; 5, diastolic runoff; 6, end-diastolic pressure

The incisura is sharply defined and is undoubtedly related to closure of the aortic valve

Pressure waveforms recorded simultaneously from different arterial sites will have different morphologies because of the physical characteristics of the vascular tree, namely, impedance and harmonic resonance.

As the arterial pressure wave travels from the central aorta to the periphery, the arterial upstroke becomes steeper, the systolic peak becomes higher, the dicrotic notch appears later, the diastolic wave becomes more prominent, and end-diastolic pressure becomes lower

Thus, when compared with central aortic pressure, peripheral arterial waveforms have higher systolic pressure, lower diastolic pressure, and wider pulse pressure

Abnormal Arterial Pressure Waveforms-

A, Normal ART and pulmonary artery pressure (PAP) waveform morphologies demonstrating the similar timing of these waveforms relative to the electrocardiographic R wave

B,In aortic stenosis, the ART waveform is distorted and demonstrates a slurred upstroke and delayed systolic peak. These changes are particularly striking in comparison to the normal PAP waveform. Note the beat-to-beat respiratory variation in the PAP waveform.

C, Aortic regurgitation produces a bisferiens pulse and a wide pulse pressure.

D, The arterial pressure waveform in hypertrophic cardiomyopathy shows a peculiar “spike-and-dome” configuration. The pressure waveform assumes a more normal morphology after surgical correction of this condition.

•Pulsus parvus (narrow pulse pressure)

•Pulsus tardus (delayed upstroke)

In aortic regurgitation, the arterial pressure wave displays a sharp rise, wide pulse pressure, and low diastolic pressure as a result of runoff of blood into the left ventricle and the periphery during diastole.

Because of the large stroke volume ejected from the left ventricle in this condition, the arterial pressure pulse may have two systolic peaks(bisferiens pulse)

These peaks represent separate percussion and tidal waves, the former resulting from left ventricular ejection and the latter arising from the periphery as a reflected wave.

hypertrophic cardiomyopathy, the arterial pressure waveform assumes a peculiar bifid shape termed a “spike-and-dome” configuration.

After an initial sharp pressure upstroke that results from rapid left ventricular ejection in early systole, arterial pressure falls rapidly as dynamic left ventricular outflow obstruction develops during midsystole and is followed by a late systolic reflected wave, thereby creating the characteristic double-peaked waveform

Beat-to-beat variability in arterial pressure waveform morphologies. A, Pulsus alternans. B, Pulsus paradoxus. The marked decline in systolic arterial pressure and pulse pressure during spontaneous inspiration (arrows) is characteristic of cardiac tamponade

Complications-

Complications of intraarterial monitoring include hematoma, bleeding (if the transducer tubing is not tightly affixed and separates from the catheter hub), vasospasm, arterial thrombosis, embolization of air bubbles or thrombi, necrosis of skin overlying the catheter, nerve damage, infection, loss of digits, and unintentional intraarterial drug injection.

The risks are minimized when the ratio of catheter to artery size is small,

heparinized saline is continuously infused through the catheter at a rate of 2–3 mL/h, flushing of the catheter is limited, and meticulous attention is paid to aseptic technique. Adequacy of perfusion can be continually monitored during radial artery cannulation by placing a pulse oximeter on an ipsilateral finger

CENTRAL VENOUS PRESSURE

MONITORING

Central Venous Pressure Monitoring Indirect assessment of CVP through physical examination of the neck veins is a fundamental aspect

of cardiovascular assessment.

Central Venous Cannulation- Cannulation of a large central vein is the standard clinical method for monitoring CVP and is also performed for a number of additional therapeutic interventions, such as providing secure vascular access for the administration of vasoactive drugs or to initiate rapid fluid resuscitation.

Indication- Central venous pressure monitoring     Pulmonary artery catheterization and monitoring    Transvenous cardiac pacing    Temporary hemodialysis     Drug administration    Concentrated vasoactive drugs    Hyperalimentation    Chemotherapy    Agents irritating to peripheral veins    Prolonged antibiotic therapy (e.g., endocarditis)    Rapid infusion of fluids (via large cannulas)    Trauma    Major surgery    Aspiration of air emboli    Inadequate peripheral intravenous access    Sampling site for repeated blood testing

Choosing the Catheter Central venous catheters come in a variety of lengths, gauges,

composition, and lumen number.

These characteristics vary according to the purpose of the catheterization, whether for CVP monitoring or other therapeutic indications and whether intended for short- or long-term use

Seven-French, 20-cm multiport catheters that allow monitoring of CVP and infusion of drugs and fluids simultaneously are the most common.

It should be noted that rapid fluid resuscitation is more efficient with short, large-bore intravenous catheters inserted peripherally because the smaller diameter of each individual lumen and the overall catheter length increase resistance to flow significantly.

eg.maximal flow rate of the 16-gauge lumen of a standard 7-Fr, 20-cm central venous catheter is a quarter that of a 16-gauge, 3-cm intravenous catheter in a large peripheral vein.

Peripherally Inserted Central Catheter (PICC) Venous access is obtained by puncturing the brachial, cephalic, or basilic vein just above or below the antecubital fossa. • The tip rests in the superior vena cava at the cavo-atrial junction. • The catheters are approximately 40-60 cm long, but may be individually sized upon insertion. • PICCs are chosen for patients requiring IV therapy for more than six days and up to one year

Site- Selecting the best site for safe and effective central venous cannulation

ultimately requires consideration of the indication for catheterization (pressure monitoring versus drug or fluid administration), the patient's underlying medical condition, the clinical setting, and the skill and experience of the physician performing the procedure.

patients with severe bleeding diatheses, it is best to choose a puncture site at which bleeding from the vein or adjacent artery is easily detected and controlled with local compression. In such a patient, an internal or external jugular approach would be preferable to a subclavian site

patients with severe emphysema or others who would be severely compromised by pneumothorax would be better candidates for internal jugular than subclavian cannulation because of the higher risk with the latter approach.

transvenous cardiac pacing is required in an emergency situation, catheterization of the right internal jugular vein is recommended because it provides the most direct route to the right ventricle.

physician must recognize that the length of catheter inserted to position the catheter tip properly in the superior vena cava will vary according to puncture site, being slightly (3 to 5 cm) greater when the left internal or external jugular veins are chosen versus the right internal jugular vein.

Site…..LESS COMMONLY USED VEINS-

1. Axillary ( anterior & lateral approach )

2. External jugular3. Brachial ( mid- upper arm

approach )4. Cephalic ( ante- cubital

fossa approach ) 5. Brachio cephalic ( supra –

clavicular approach )

Location Advantage Disadvantage

Internal Jugular

• Bleeding can be recognized and controlled• Malposition is rare• Less risk of pneumothorax

• Risk of carotid artery puncture• PTX possible

Femoral • Easy to find vein• No risk of pneumothorax• Preferred site for emergencies and CPR

• Highest risk of infection• Risk of DVT• Not good for ambulatory patients

Subclavian • Most comfortable for conscious patients

• Highest risk of PTX• Should not be done if < 2 years• Vein is non-compressible

Technique

Seldinger techniqueUse introducing needle to locate veinWire is threaded through the needleNeedle is removedSkin and vessel are dilatedCatheter is placed over the wireWire is removedCatheter is secured in place

Internal Jugular Approach Positioning

Right side preferred Trendelenburg position Head turned slightly away from side

of venipuncture

Needle placement: Central approach Locate the triangle formed by the

clavicle and the sternal and clavicular heads of the SCM muscle

Gently place three fingers of left hand on carotid artery

Place needle at 30 to 40 degrees to the skin, lateral to the carotid artery

Aim toward the ipsilateral nipple under the medial border of the lateral head of the SCM muscle

Vein is 1-1.5 cm deep, avoid deep probing in the neck

Subclavian Approach

Positioning Right side preferred Supine position, head neutral, arm abducted Trendelenburg (10-15 degrees) A small roll is placed between the

shoulder blades to expose the infraclavicular area fully

Needle placement The skin is punctured 2 to 3 cm caudad

to the midpoint of the clavicle

Needle should be parallel to skin

needle as it is inserted just beneath the posterior surface of the clavicle.

Aim towards the supraclavicular notch and just under the clavicle

Femoral Approach Positioning

Supine Needle placement

Medial to femoral artery Needle held at 45 degree angle Skin insertion 2 cm below inguinal

ligament Aim toward umbilicus

Left Internal Jugular Vein-several anatomic details make the left side less attractive than the right. The cupola of the pleura is higher on the left, thereby increasing the risk for pneumothorax

The thoracic duct may be injured during the procedure as it enters the venous system at the junction of the left internal jugular and subclavian veins.

The left internal jugular vein is often smaller than the right and demonstrates a greater degree of overlap of the adjacent carotid artery during head rotation.

Catheters inserted from the left side of the patient must traverse the innominate (i.e., left brachiocephalic) vein and enter the superior vena cava perpendicularly, and their distal tips may impinge on the right lateral wall of the superior vena cava and thereby increase the potential for vascular injury.

This anatomic disadvantage pertains to all left-sided catheterization sites and highlights

the need for radiographic confirmation of proper catheter location.Complications of Central Venous Pressure Monitoring-

1)Mechanical  -  Vascular injury   - Arterial  ,  Venous  ,  Hemothorax  ,  Cardiac tamponade,    Respiratory compromise -   Airway compression from hematoma Tracheal,

laryngeal injury ,   Pneumothorax    Nerve injury    Arrhythmias    Subcutaneous/mediastinal emphysema   

2)Thromboembolic    Venous thrombosis  ,  Pulmonary embolism   , Arterial thrombosis ,and embolism (air, clot)    

3) Infectious    Insertion site infection    Catheter infection     Bloodstreainfection    Endocarditis   

Methods to measure CVP1. Indirect assessment- Inspection of jugular venous pulsations

in neck.

2. Direct assessment- Fluid filled manometer connected to

central venous catheter. Caliberated transducer.

1. Inspection of jugular venous pulsations in neck.

No valves b/w rt. atrium & IJV. Degree of distention & venous wave

form –information about cardiac function

2. Fluid filled manometer connected to central venous catheter-

measured using a column of water in a marked manometer. CVP is the height of the column in cms of H2O when the column is at the

level of right atrium. Advantage- simplicity to measure. Disadvantage- Inability to analyze the CVP waveform.

-Relatively slow response of the water column to changes in intrathoracic pressure.

Normal values = 2 – 8 mm Hg (5 to 10 cm of water) Low CVP = hypovolemia or ↓ venous return

High CVP = over hydration, ↑ venous return, or right-sided heart failure

Phlebostatic Axis4th intercostal space, mid-axillary line

Measurement of cvp cont…

Caliberated transducer.Automated, electronic pressure monitor

Pressure wave form displayed on an oscilloscope or paper.

Advantages-

More accurate.

Direct observation of waveform.

Normal Central Venous Pressure Waveforms CVP is the pressure measured at the junction of the venae cavae and the

right atrium and reflects the driving force for filling the right atrium and ventricle

The CVP waveform consists of five phasic events, three peaks (a, c, v) and two descents (x, y)

Waveform Component

Phase of Cardiac Cycle Mechanical Event

a wave End diastole Atrial contraction

c wave Early systole

Isovolumic ventricular contraction, tricuspid motion toward the right atrium

v wave Late systole Systolic filling of the atrium

h wave Mid to late diastole Diastolic plateau

x descent Mid systole

Atrial relaxation, descent of the base, systolic collapse

y descent Early diastoleEarly ventricular filling, diastolic collapse

Abnormal Central Venous Pressure Waveforms Various pathophysiologic conditions may be diagnosed or confirmed by

examination of the CVP waveform . One of the most common applications is rapid diagnosis of cardiac arrhythmias

Condition Characteristics

Atrial fibrillationLoss of a wave

Prominent c wave

Atrioventricular dissociation Cannon a wave

Tricuspid regurgitationTall systolic c-v wave

Loss of x descent

Tricuspid stenosisTall a wave

Attenuation of y descent

Right ventricular ischemia

Tall a and v waves

Steep x and y descents

M or W configuration

Pericardial constriction

Tall a and v waves

Steep x and y descents

M or W configuration

Cardiac tamponadeDominant x descent

Attenuated y descent

Respiratory variation during spontaneous or positive-pressure ventilation

Measure pressures at end-expiration

Changes in central venous pressure (CVP) in tricuspid valve disease

A, Tricuspid regurgitation increases mean CVP, and the waveform displays a tall systolic c-v wave that obliterates the x descent. In this example the a wave is not seen because of atrial fibrillation. Right ventricular end-diastolic pressure is estimated best at the time of the electrocardiographic R wave (arrows) and is lower than mean CVP

B, Tricuspid stenosis increases mean CVP, the diastolic y descent is attenuated, and the end-diastolic a wave is prominent

the most important application of CVP monitoring is to provide an estimate of the adequacy of circulating blood volume and right ventricular preload

accurate interpretation of CVP requires the physician to consider the alterations in intrathoracic or juxtacardiac pressure that occur during the respiratory cycle

A, During spontaneous ventilation, the onset of inspiration (arrows) causes a reduction in intrathoracic pressure, which is transmitted to both the CVP and pulmonary artery pressure (PAP) waveforms. CVP should be recorded at end-expiration (mean CVP, 14 mm Hg).

B, During positive-pressure ventilation, the onset of inspiration (arrows) causes an increase in intrathoracic pressure. CVP is still recorded at end-expiration (mean CVP, 8 mm Hg).  

Pulmonary Artery Catheter MonitoringPulmonary Artery Catheter -Invented in 1970 by Swan, Ganz and

colleagues for hemodynamic assessment of patients with acute myocardial infarction.

Standard PAC is 7.0, 7.5 or 8.0 French in circumference and 110 cm in length divided in 10 cm intervals

PAC has 4-5 lumens:Temperature thermistor located proximal to balloon to measure pulmonary artery blood temperature

Proximal port located 30 cm from tip for CVP monitoring, fluid and drug administration

Distal port at catheter tip for PAP monitoring

+/- Variable infusion port (VIP) for fluid and drug administration

Balloon at catheter tip

Indications• Diagnostic assessment of shock states (cardiogenic, distributive, hypovolemic) and

assessment of response to treatment

o Using cardiac output, stroke volume, systemic vascular resistance

• LV preload and LV performance, pulmonary vasomotor tone, intravascular volume status, especially in the context of acute lung injury

• Right heart pressures

o Using right atrial pressure, pulmonary artery pressure

• Intracardiac shunt Assess volume status Assess RV or LV failure Assess Pulmonary Hypertension Assess Valvular disease Cardiac Surgery

Sites

• IJV, subclavian, femoral also possible

Pulmonary Artery Catheterization- waveforms

can measure core temperature, CVP as well as pulmonary artery pressure and occlusion pressure, cardiac output, and mixed venous oxygen saturation, and calculate systemic and pulmonary vascular resistance, oxygen delivery, stroke volume, arteriovenous oxygen content differences, oxygen extraction ratios, and shunt fractions.

Cardiac Output MonitoringIndications - Patients who benefit from measurements of pulmonary artery

pressure also benefit from determination of cardiac output. In fact, to use the information available from PACs most effectively, cardiac output must be obtained .

Techniques & Complications1) thermodilution technique has become standard for measuring cardiac output because of its ease

of implementation and extensive clinical experience with its use in various settings.

For thermodilution, heat is injected, and change in temperature downstream is measured.

a fixed volume of iced or room-temperature fluid is injected as a bolus into the proximal (right atrial) lumen of the PAC, and the resulting change in pulmonary artery blood temperature is recorded by a thermistor at the catheter tip.

As in all other forms of cardiovascular monitoring, it is important to have a real-time display of the thermodilution curve resulting from each cardiac output measurement

A modification of the thermodilution technique allows continuous cardiac output measurement with a special catheter and monitor system.

A computer in the monitor determines cardiac output by cross-correlating the amount of heat input with the changes in blood temperature

2) Dye Dilution -If indocyanine green dye (or another indicator such as lithium) is injected through a central venous catheter, its appearance in the systemic arterial circulation can be measured by analyzing arterial samples with an appropriate detector.

3) Ultrasonography- Pulsed Doppler that can be used to measure the velocity of aortic blood flow. Combined with TEE, which determines the aortic cross-sectional area, this technique can measure stroke volume and cardiac output.

4) Fick Principle - Fick cardiac output method is not widely applied in clinical practice, the physiologic relationships described by the Fick equation form the basis for another PAC-based monitoring technique termed continuous mixed venous oximetry.

Mixed venous and arterial oxygen content are easily determined if a PAC and an arterial line are in place. Oxygen consumption can also be calculated from the difference between the oxygen content in inspired and expired gas

4) END-TIDAL CARBON DIOXIDE PRESSURE- Because of high lipid solubility and the ability to cross the blood-air barrier, change in exhaled CO2 is a function of pulmonary blood flow and thus indirectly of cardiac output.

Therefore, the proportion of CO2 in exhaled gases reflects the cardiac output.

5) ECHOCARDIOGRAPHY

6) ARTERIAL LACTATE

7)GASTRIC TONOMETRY- measurement of gut mucosal carbon dioxide has been used to detect

blood flow. Accumulation of carbon dioxide is predominantly a result of hypoperfusion

and not hypoxia

Electrocardiography• The electrical axis of lead II is approximately 60° from the right arm to the left leg, which is parallel to the electrical axis of the atria, resulting in the largest P wave voltages of any surface lead. This orientation enhances the diagnosis of arrhythmias and the detection of inferior wall ischemia.

• Lead V5 lies over the fifth intercostal space at the anterior axillary line; this position is a good compromise for detecting anterior and lateral wall ischemia.

Clinical Considerations

Its routine use allows arrhythmias, myocardial ischemia, conduction abnormalities, pacemaker malfunction, and electrolyte disturbances to be detected

Pulmonary Monitors1) PULSEOXIMETRY

A NON INVASIVE TECHNOLGY TO MONITOR OXYGEN SATURATION OF THE HAEMOGLOBIN

Pulse oximetry works by analyzing the pulsatile arterial component of blood flow, thereby ensuring that arterial saturation (SpO2) rather than venous saturation is being measured

Two wavelengths of light are used, usually 660 nm (red) and 940 nm (infrared), because oxygenated and deoxygenated blood each absorb light quite differently at these wavelengths-Lambert–Beer law-

At 660 nm, HbO2 absorbs less light than HbR does, whereas the opposite is observed with infrared light.

Two diodes emitting light of each wavelength are placed on one side of the probe and a photo diode that senses the transmitted light on the opposite side

The amount of light absorbed at each wavelength by the pulsatile arterial component (AC) of blood flow can be distinguished from baseline absorbance of the nonpulsatile component and surrounding tissue (DC).

The ratio of absorbencies at these two wavelengths is calibrated empirically against direct measurements of arterial blood oxygen saturation (SaO2) in

volunteers, and the resulting calibration algorithm is stored in a digital microprocessor within the pulse oximeter.

Oxygen saturation will not decrease until PaO2 is below 85mmHg.

At SpO2 of 90% PaO2 is already 60mmHg.

Rough guide for PaO2 between saturation of 90%-75% is PaO2 = SpO2 - 30.

SpO2< than 76% is life threatening.

Clinical Considerations

In addition to SpO2, pulse oximeters provide an indication of tissue perfusion (pulse amplitude) and measure heart rate

carboxyhemoglobin (COHb) and HbO2 absorb light at 660 nm identically, pulse oximeters that compare only two wavelengths of light will register a falsely high reading in patients with carbon monoxide poisoning.

Methemoglobin has the same absorption coefficient at both red and infrared wavelengths. The resulting 1:1 absorption ratio corresponds to a saturation reading of 85%.

Thus, methemoglobinemia causes a falsely low saturation reading when SpO2 is actually greater than 85% and a falsely high reading if SpO2 is actually less than 85%.

Other causes of pulse oximetry artifact include excessive ambient light, motion, methylene blue dye, venous pulsations in

a dependent limb, low perfusion (eg, low cardiac output, profound anemia, hypothermia, increased systemic vascular resistance), malpositioned sensor, and leakage of light from the light-emitting diode to the photodiode.

Two extensions of pulse oximetry technology are mixed venous blood oxygen saturation (SvO2) and noninvasive brain oximetry

1)SvO2- requires the placement of a PAC containing fiberoptic sensors that continuously determine SvO2 in a manner analogous to pulse oximetry.

placing the fiberoptic sensor in the internal jugular vein,via PAC, which provides measurements of jugular bulb oxygen saturation in an attempt to assess the adequacy of cerebral oxygen delivery.

2) Noninvasive brain oximetry monitors - regional oxygen saturation (rSO2) of hemoglobin in the brain

Capnography

Capnometry is the measurement of expired CO2 and has become increasingly popular as a diagnostic tool in a number of settings. It is now the confirmation method of choice in anesthesia for proper placement of

an endotracheal tube. CO2 concentration is usually measured by infrared absorption with either

a mainstream or sidestream capnometer. 1998 it was adopted by the American Society of Anesthesiologists as

standard care for all general anesthetics administered. Reflects

Ventilation - movement of air in and out of the lungs

Diffusion - exchange of gases between the air-filled alveoli and the pulmonary circulation

Perfusion - circulation of blood

Capnography – Sidestream or Mainstream

Mainstream Unit – a device that samples the CO2 levels in-line. There is no delay in the capnogram trace. Gives a fast response. Fixed volume of dead space

Sidestream Unit – a device that extracts a sample of the airway gas and performs the analysis inside the machine. Can be very small dead space.

45

0

Capnographic Waveform

A B

C D

E

Baseline

•Although other gases are present in the airway, the capnograph detects only CO2 from ventilation. •There is usually no CO2 present during inspiration so the baseline is normally on zero.

Phase I(Dead Space Ventilation)-

Baseline

Beginning of exhalation

•Beginning of exhalation•No CO2 present•Air from trachea, posterior pharynx, mouth and nose

No gas exchange occurs thereCalled “dead space”

Capnogram Phase IIAscending Phase

CO2 present and increasing in exhaled air

II

A B

C

Ascending PhaseEarly Exhalation

CO2 from the alveoli begins to reach the upper airway and mix with the dead space air

Causes a rapid rise in the amount of CO2

CO2 now present and detected in exhaled air

Alveoli

Capnogram Phase IIIAlveolar Plateau

CO2 exhalation wave plateaus

A B

C D

III

Alveolar Plateau

•CO2 rich alveolar gas now constitutes the majority of the exhaled air •Uniform concentration of CO2 from alveoli to nose/mouth

Capnogram Phase III End-Tidal

End of the the wave of exhalation

A B

C D End-tidal

End of exhalation contains the highest concentration of CO2

The “end-tidal CO2” The number seen on your monitor

Normal EtCO2 is 35-45mmHg

Capnogram Phase IV -Descending Phase

Inspiratory downstroke returns to baseline

A B

C D

EIV

Descending Phase Inhalation

•Inhalation begins•Oxygen fills airway•CO2 level quickly drops to zero

Alveoli

Capnography Waveform Patterns

0

45

Hypoventilation

45

0

Hyperventilation

45

0

Normal

ElectroencephalographyIndications & Contraindications used in cerebrovascular surgery to confirm the adequacy of cerebral oxygenation. Monitoring the depth of anesthesia with a full 16-lead,

Techniques & Complications The EEG is a recording of electrical potentials generated by cells in the cerebral cortex. New two-channeled processed EEG devices pass the EEG signal through a fast Fourier

transform (bispectral analysis) leading to a traditional power spectrum.

Bispectral Index (BIS) represents a numerical value that has been correlated with the patient's current hypnotic state

Clinical Considerations

To perform a bispectral analysis, data measured by EEG are taken through a number of steps

to calculate a single number that correlates with depth of anesthesia/hypnosis Bispectral Index Scale is a dimensionless scale from 0 (complete cortical

electroencephalographic suppression) to 100 (awake). BIS values of 65–85 have been recommended for sedation, values of 40–65 have been recommended for general anesthesia. At BIS values lower than 40, burst cortical suppression At 0 flat EEG

Evoked Potentials

Indications It include surgical procedures associated with possible

neurological injury: spinal fusion with instrumentation, spine and spinal cord tumor resection, brachial plexus repair, thoracoabdominal aortic aneurysm repair, epilepsy surgery, and cerebral tumor resection. Ischemia in the spinal cord or cerebral cortex can be detected by EPs.

Techniques & Complications EP monitoring noninvasively assesses neural function by measuring

electrophysiological responses to sensory or motor pathway stimulation. Commonly monitored EPs are brain stem auditory evoked responses (BAERs), SEPs, and increasingly MEPs

Temperature

Indications The temperature of patients undergoing general anesthesia should be monitored. Very brief procedures (eg, less than 15 min) may be an exception to this guideline.

Contraindications There are no contraindications,

Techniques & Complications Intraoperatively, temperature is usually measured using a thermistor or

thermocouple .

A thermocouple is a circuit of two dissimilar metals joined so that a potential difference is generated when the metals are at different temperatures.

Disposable thermocouple and thermistor probes are available for monitoring the temperature of the tympanic membrane, nasopharynx, esophagus, bladder, rectum, and skin. Complications of temperature monitoring are usually related to trauma caused by the probe (eg, rectal or tympanic membrane perforation).

Urinary Output

Urinary bladder catheterization is the only reliable method of monitoring urinary output

Catheterization is routine in some surgical procedures such as cardiac surgery, aortic or renal vascular surgery, craniotomy, major abdominal surgery, or procedures in which large fluid shifts are expected

Lengthy surgeries and intraoperative diuretic administration are other possible indications

Clinical Considerations- An additional advantage of placing a Foley catheter is the ability to include a thermistor in the catheter tip so that bladder temperature can be monitored

bladder temperature accurately reflects core temperature Urinary output is a reflection of kidney perfusion and function and an

indicator of renal, cardiovascular, and fluid volume status oliguria is often arbitrarily defined as urinary output of less than 0.5

mL/kg/h,

Peripheral Nerve Stimulation Because of the variation in patient sensitivity to neuromuscular blocking

agents, the neuromuscular function of all patients receiving intermediate- or long-acting neuromuscular blocking agents should be monitored

helpful in assessing paralysis during rapid-sequence inductions or during continuous infusions of short-acting agents.

help in locate nerves to be blocked by regional anesthesia.

Techniques- peripheral nerve stimulator delivers a current of variable frequency and amplitude to a pair of either ECG silver chloride pads or subcutaneous needles placed over a peripheral motor nerve.

The evoked mechanical or electrical response of the innervated muscle is observed

Ulnar nerve stimulation of the adductor pollicis muscle and facial nerve stimulation of the orbicularis oculi are most commonly monitored

direct stimulation of muscle should be avoided by placing electrodes over the course of the nerve and not over the muscle itself

To deliver a supramaximal stimulation to the underlying nerve, peripheral nerve stimulators must be capable of generating at least a 50-mA current

Testing- When pressing the train-of-four button, the stimulus is sent as a group of

0.2-millisecond pulses in a square-wave pattern spaced 500 milliseconds apart. This is repeated every 10 seconds.

The number of muscle twitches needs to be counted.

Response is measured as follows:- When 4 twitches are seen, 0-75% of the receptors are blocked. When 3 twitches are seen, at least 75% of the receptors are blocked. When 2 twitches are seen, 80% of the receptors are blocked. When 1 twitch is seen, 90% of the receptors are blocked. When no twitches are seen, 100% of receptors are blocked.

Principles of Peripheral NerveStimulation Each muscle fiber to a stimulus follows an all-or-none pattern In contrast, response of the whole muscle depends on the number of

muscle fibers activated Response of the muscle decreases in parallel with the numbers of fibers

blocked Reduction in response during constant stimulation reflects degree of NM

Blockade For this reason stimulus is supramaximal

Features of Neurostimulation

Nerve stimulator- device that delivers depolarizing current via electrodes Essential Features

• Square-wave impulse, <0.5msec,>0.1msec • Constant current variable voltage• Battery powered • Multiple patterns of stimulation

Features of Neurostimulation…..…

Stimulus strength- it is the depolarizing intensity of stimulating current

Pulse width-duration of the individual impulse delivered by nerve stimulator

Threshold current –lowest current required to depolarize a nerve fiber

Supramaximal current-it is 10 -20% higher intensity than the current required to depolarize all fibers in a nerve bundle

Stimulus Frequency- rate at which each impulse is repeated in

cycles per sec(Hz)

Patterns of Stimulation Single-Twitch Stimulation Train-of-Four Stimulation Tetanic Stimulation Post-Tetanic Count Stimulation Double-Burst Stimulation

Single-Twitch Stimulation

Single supramaximal stimuli applied to a nerve at frequencies from 1.0Hz-0.1Hz Height of response depends on the number of unblocked junctions Prerelaxant control value is needed Does not detect receptor block of <70% Used to assess potency of drugs Stimulation dependent onset time

Train-of-Four Stimulation

In partial non- depolarizing block T4/T1 ratio and is inversely proportional to degree of blockade In partial depolarizing block, no fade occurs in TOF ratio Fade, in depolarizing block signifies the development of phase II block

Four supramaximal stimuli are given every 0.5 sec “Fade” in the response provides the basis for evaluation The ratio of the height of the 4th response(T4) to the 1st response(T1) is TOF ratio

Tetanic Stimulation

Tetanic Stimulation is 50-Hz stimulation 50Hz given for 5 sec During normal NM transmission and pure depolarizing block the response is sustained During non- depolarizing block & phase II block the response fades During partial non- depolarizing block, tetanic stimulation is followed by post-tetanic facilitation

Electromyography

Compound muscle action potential It is cumulative electrical signal generated by individual APs

of individual muscle fibers EMG records the compound MAP via recording

electrodes The amplitude of compound MAP is proportional to

number of muscle units that generate MAP

Electro Sensor

THANK YOU !