Normal central venous pressure (CVP) waveform. The diastolic components (y descent, end-diastolic a wave) and the systolic components (c wave, x descent, end-systolic v wave) are all clearly delineated
Characteristic waveforms recorded during passage of the pulmonary artery catheter. Right atrial pressure resembles a central venous pressure waveform and displays a, c, and v waves. Right ventricular pressure shows higher systolic pressure than seen in the right atrium, although the end-diastolic pressures are equal in these two chambers. Pulmonary artery pressure shows a diastolic step-up when compared with ventricular pressure. Note also that right ventricular pressure increases during diastole whereas pulmonary artery pressure decreases during diastole (shaded boxes). Pulmonary artery wedge pressure has a similar morphology to right atrial pressure, although the a-c and v waves appear later in the cardiac cycle relative to the electrocardiogra
relates the absorption of light to the properties of the material through which the light is traveling.
Standards for Basic Anesthetic Monitoring
The AmericanSociety of Anesthesiologists (ASA) guidelines for basic
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
The most primitive method of monitoring the
patient 25 years ago was continuous palpation
of the radial pulsations throughout the
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.
Why 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
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
Under GA the pt may be hypo or hyperventilated and may
Blood loss → anemia, hypotension. So it is necessary to
recognise when the pt is in need of blood transfusion
monitoring: - Introduction.....
The FOUR BASIC Monitors:
We are NOT authorised to start a surgery in the
absence of any of these monitors:
SpO2: arterial O2 saturation.
Blood Pressure: NIBP (non-invasive), IBP (invasive).
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.
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
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
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.
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 ˃ 90mmHg.
Palpation of Dorsalis Pedis A → systolic BP ˃ 80
Palpation of Superficial Temporal A → systolic BP ˃
i.e If Radial A pulsations are lost = systolic BP is < 90
If dorsalis pedis & superficial temporal pulsations are
lost = systolic BP is < 80 mmHg.
Check pt colour for pallor: lips, tongue, nails,
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
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
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
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
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 beatto-beat blood pressure regulation, and the need for multiple arterial blood
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
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
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
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
Technique of Radial Artery Cannulation -
1-preparing the skin with a bactericidal
2- Supination and extension of the wrist
provide optimal exposure of the radial
3- needle through the skin at a 45° angle
4 )18-, 20-, or 22-gauge catheter over a
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, continuousflush 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
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, enddiastolic pressure
The incisura is sharply defined and is undoubtedly related to closure of the
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 WaveformsA, Normal ART and pulmonary
artery pressure (PAP)
demonstrating the similar timing
of these waveforms relative to
the electrocardiographic R
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-tobeat respiratory variation in
the PAP waveform.
•Pulsus parvus (narrow pulse pressure)
•Pulsus tardus (delayed upstroke)
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.
C, Aortic regurgitation produces a
bisferiens pulse and a wide pulse
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
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 doublepeaked 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 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
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
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
Concentrated vasoactive drugs
Agents irritating to peripheral veins
Prolonged antibiotic therapy (e.g., endocarditis)
Rapid infusion of fluids (via large cannulas)
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
• The tip rests in the
superior vena cava at the
• The catheters are
approximately 40-60 cm
long, but may be
individually sized upon
• PICCs are chosen for
patients requiring IV
therapy for more than six
days and up to
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
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.
• Bleeding can be recognized • Risk of carotid artery puncture
• PTX possible
• Malposition is rare
• Less risk of pneumothorax
• 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
• Most comfortable for
• Highest risk of PTX
• Should not be done if < 2 years
• Vein is non-compressible
Use introducing needle to locate vein
Wire is threaded through the needle
Needle is removed
Skin and vessel are dilated
Catheter is placed over the wire
Wire is removed
Catheter is secured in place
Internal Jugular Approach
Right side preferred
Head turned slightly away from side
Needle placement: Central
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
Right side preferred
Supine position, head neutral, arm
Trendelenburg (10-15 degrees)
A small roll is placed between the
shoulder blades to expose the
infraclavicular area fully
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
Medial to femoral artery
Needle held at 45 degree angle
Skin insertion 2 cm below inguinal
Aim toward umbilicus
Left Internal Jugular Veinseveral 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
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 Monitoring1)Mechanical
Vascular injury - Arterial , Venous , Hemothorax , Cardiac
Respiratory compromise - Airway compression from hematoma
Tracheal, laryngeal injury , Pneumothorax
2)Thromboembolic Venous thrombosis , Pulmonary embolism , Arterial
thrombosis ,and embolism (air, clot)
Insertion site infection
Methods to measure CVP 1. Indirect assessment
Inspection of jugular venous pulsations
Direct assessmentFluid filled manometer connected to
central venous catheter.
Inspection of jugular venous
pulsations in neck.
No valves b/w rt. atrium & IJV.
Degree of distention & venous wave
form –information about cardiac
Fluid filled manometer connected to central venous cathetermeasured 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
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
4th intercostal space, mid-axillary line
Measurement of cvp cont…
Caliberated transducer.Automated, electronic pressure monitor
Pressure wave form displayed on an oscilloscope or paper.
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
The CVP waveform consists of five phasic events, three peaks (a, c, v)
and two descents (x, y)
Phase of Cardiac
toward the right
Systolic filling of the
Mid to late diastole Diastolic plateau
descent of the
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
Loss of a wave
Prominent c wave
Cannon a wave
Tall systolic c-v wave
Loss of x descent
Tall a wave
Attenuation of y descent
Tall a and v waves
Right ventricular ischemia
Steep x and y descents
M or W configuration
Tall a and v waves
Steep x and y descents
M or W configuration
Respiratory variation during
spontaneous or positivepressure ventilation
Dominant x descent
Attenuated y descent
Measure pressures at endexpiration
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 enddiastolic pressure is estimated best at
the time of the electrocardiographic R
wave (arrows) and is lower than mean
B, Tricuspid stenosis increases mean
CVP, the diastolic y descent is
attenuated, and the end-diastolic a wave
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
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 Monitoring
Pulmonary Artery Catheter -Invented in 1970 by Swan, Ganz and
colleagues for hemodynamic assessment of patients with acute myocardial
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
Distal port at catheter tip for PAP
+/- Variable infusion port (VIP) for
fluid and drug administration
Balloon at catheter tip
• 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
• IJV, subclavian, femoral also possible
CVP as well as pulmonary artery pressure and occlusion pressure,
cardiac output, and mixed venous oxygen saturation, and
calculate systemic and pulmonary vascular resistance,
arteriovenous oxygen content differences,
oxygen extraction ratios,
and shunt fractions.
Cardiac Output Monitoring
Indications - 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
Techniques & Complications
1) 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
3) Ultrasonography- Pulsed Doppler that can be used to measure the velocity
of aortic blood flow. Combined with TEE, which determines the aortic crosssectional area, this technique can measure stroke volume and cardiac
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
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
Therefore, the proportion of CO2 in exhaled gases reflects the cardiac
6) ARTERIAL LACTATE
7)GASTRIC TONOMETRY measurement of gut mucosal carbon dioxide has been used to detect
Accumulation of carbon dioxide is predominantly a result of hypoperfusion
and not hypoxia
• 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
• 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
Its routine use allows arrhythmias, myocardial ischemia, conduction
abnormalities, pacemaker malfunction, and electrolyte disturbances to be
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 wavelengthsLambert–Beer lawAt 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.
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
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.
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
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.
•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
normally on zero.
Phase I(Dead Space Ventilation)•Beginning of exhalation
•No CO2 present
•Air from trachea,
mouth and nose
No gas exchange
Called “dead space”
Beginning of exhalation
CO2 from the alveoli begins to reach
the upper airway and mix with the dead
Capnogram Phase II
Causes a rapid rise in the amount of CO2
CO2 now present and detected in
CO2 present and increasing in exhaled air
Capnogram Phase III
•CO2 rich alveolar gas now constitutes the majority of
the exhaled air
•Uniform concentration of CO2 from alveoli to
CO2 exhalation wave plateaus
Capnogram Phase III 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
End of the the wave of exhalation
Capnogram Phase IV -Descending Phase
•Oxygen fills airway
•CO2 level quickly
drops to zero
Inspiratory downstroke returns to baseline
Indications & 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
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
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
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
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
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.
There are no contraindications,
Techniques & Complications
Intraoperatively, temperature is usually measured using a thermistor or
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 bladder catheterization is the only reliable method of monitoring
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
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
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
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
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
Reduction in response during constant stimulation reflects degree of NM
For this reason stimulus is supramaximal
Features of Neurostimulation
Nerve stimulator- device that delivers depolarizing current via electrodes
•Square-wave impulse, <0.5msec,>0.1msec
•Constant current variable voltage
•Multiple patterns of stimulation
Features of Neurostimulation…..…
Stimulus strength- it is the depolarizing intensity of stimulating
Pulse width-duration of the individual impulse delivered by
Threshold current –lowest current required to depolarize a
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
Post-Tetanic Count Stimulation
Single supramaximal stimuli applied to a nerve at frequencies from 1.0Hz0.1Hz
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
stimuli are given every
“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
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
Tetanic Stimulation is
50-Hz stimulation 50Hz
given for 5 sec
During normal NM
transmission and pure
depolarizing block the
response is sustained
During nondepolarizing block & phase
II block the response fades
During partial nondepolarizing block, tetanic
stimulation is followed by
Compound muscle action potential
It is cumulative electrical signal generated by individual APs
of individual muscle fibers
EMG records the compound MAP via recording
The amplitude of compound MAP is proportional to
number of muscle units that generate MAP