Clinical monitoring in the ICU By: ABRAHA HAILU(MD)
Blood pressure monitoring
Central venous pressure monitoring
Pulmonary artery pressure monitoring
Mixed venous oxygen monitoring
Why monitor BP?
Provides data for interpretation/therapeutic decisions
Important for determining organ perfusion (MAP most important, except with the heart)
Noninvasive Hemodynamic Monitoring
Heart Rate, pulses
Indications for Arterial Blood Pressure
Frequent titration of vasoactive drips
Major surgery involving large fluid shifts or EBL
Unstable blood pressures
Frequent ABGs or labs
Unable to obtain Non-invasive BP
Supplies to Gather
Flush – 500cc NS
Suture (silk 2.0)
Potential Complications Associated With Arterial Lines
Altered Skin Integrity
Central Venous Pressure Monitoring
CVP measures the filling pressure of the right ventricular (RV); it gives an estimate of the intravascular volume status and is an interplay of the:
(1) circulating blood volume
(2) venous tone and
(3) right ventricular function .
CVP BLOOD VOLUME (INCREASED VENOUS RETURN RAISES CVP CARDIAC COMPETENCE (REDUCED VENTRICULAR FUNCTION RAISES CVP) INTRATHORACIC AND INTRAPERITONEAL PRESSURE (RAISES CVP) SYSTEMIC VASCULAR RESISTENCE (INCREASED TONE RAISES CVP)
NORMAL CVP MEASUREMENTS
CVP monitoring should normally show measurements as follows:
Mid Axilla: 0 - 8 mmHg
An isolated CVP reading is of limited value;
a trend of readings is much more significant and should be viewed in conjunction with other parameters e.g. BP and urine output.
Indications for central venous catheter placement
Major operative procedures involving large fluid shifts and / or blood loss or Major trauma
Diagnosis of RV failure : evidenced by high CVP in the presence of low Cardiac output
Pharmacological intervention which is likely to result in changes in venous capacitance (Ex: drugs such as sodium nitroprusside can be used more safely if the CVP is known)
fluid management, Intravascular volume assessment, when urine output is not reliable or unavailable (e.g.: renal failure)
Surgical procedures with a high risk of air embolism , such as sitting position craniotomies. In addition to monitoring, the central venous pressure (CVP) catheter may also be used to aspirate intracardiac air.
Frequent venous blood sampling
Venous access for vasoactive or irritating drugs
Chronic drug administration
Inadequate peripheral IV access
Rapid infusion of IV fluids
insertion of PA catheters
insertion of transvenous pacing wires
Infection at the site of insertion
Newly inserted pacemaker wires
Presence of carotid disease
Recent cannulation of the internal jugular vein
Contra lateral diaphragmatic dysfunction
Thyromegaly or prior neck surgery
Central Venous Catheter Placement
Catheter-over-a-guidewire (seldinger technique)
Central line from peripheral site (antecubital fossa commonly selected)
External jugular site
Internal jugular site
All have their own indications, contraindications, advantages & disadvantages
Sterile gown and mask (optional)
Sterile prep solution
Sterile flush solution
Suture material ( might be included in the kit )
Manometer set (this may vary according to whether C.V.P. to be transduced or not )
500ml of0.9% Sodium Chloride. (500ml Sodium Chloride with 500 units heparin used in transduced circuits only)
Pressure bag (only used in transduced circuits)
Sedatives (if required)
• Central venous catheter kit:
Different types of kits are available
All have the use of the Seldinger over-the-wire technique for placement
Likewise, the type of catheter inserted varies with its intended purpose:
A multiple lumen catheter might be needed to infuse several different types of vasoactive medications,
while a large-bore catheter is better for infusing a large volume of fluid or as a port for inserting a Swan-Ganz catheter.
The sites and techniques for placing central venous catheters are numerous
Cannulation of internal jugular vein (IJV) was first described by English et al2 in 1969
Since then, it has steadily increased in popularity as one of the methods of choice for CVP/RAP monitoring.
The reason for this popularity relates to:
it’s short, straight (right IJV), valveless course to SVC and RA; and
its position at the patient’s head, which provides easy access by anesthetists in more intra operative settings
the success rate for its use exceeds 90% in most series of adults and children
For accurate measurement of CVP/RAP and also to aid aspiration of air in venous air embolism, the catheter tip is positioned ideally at
the SVC-RA junction,
high up in the RA, away from the tricuspid valve
Cannulation of the IJV is relatively safe and convenient and various approaches exist for its cannulation
The process of cannulation outlined in the following table
The pressure can be measured in at least two ways :
the height of the column denoting the pressure
2. Pressure transducer:
converts the pressure wave to an electrical signal which can then be displayed
WATER MANOMETER :
Simple & inexpensive
Any piece of open IV tubing can be used
Specific problems include:
Placement of the catheter in the right ventricle
TR with a large reflux pressure wave
Giant ‘a’ waves from the atrium ( cannon waves, A-V dissociation & nodal rhythms)
Each of these will lead to CVP measurements which may be misleading, & markedly different from the real prassure
a sterile bag of fluids
attached fluid administration set
an IV extension set
a manometer and
a. b. c. d. e.
EQUIPMENT IV extension set to entry port of patients central line. IV giving set to fluid bag. Stopcock (Three way tap)
DIRECTION OF FLOW The white arrows indicate the direction of fluid flow. (a). Initially the white knob is turned straight up, allowing fluid to flow from the fluid bag to the patient's catheter to assure the catheter is patent.. If fluid does not flow freely into the patient's catheter a valid CVP reading will not be obtained. (b) Then the knob is turned toward the patient and fluid will fill the manometer. The manometer should not contain any air bubbles . If air is present in the manometer or fluid line, let the fluids run, overfilling the manometer until all air is purged from the system. (c) Then turn the knob toward the fluids. The level of fluid in the manometer will fall (the fluid is running into the patient's catheter) until the height of the fluid column exerts a pressure equivalent to the patient's CVP The top of the fluid column will slightly oscillate up and down as the pt’s heart beats and as the pt breathes. a. c. b.
POSITION OF PATIENT 3-way tap manometer Fluid Bag Patient in supine position Central Venous Access
An electronic system with fast response time & gives a more accurate wave representation
This enables maximum & minimum pressures to be identified as well as visualization of the wave form which may supply information about the presence, for example of tricuspid incompetence
Further more the mean pressure can be measured & this is usually the true CVP as it takes in to account the respiratory cycle
Complex in setting up the system
Nursing staff need to be familiar with the system
There is always a risk of electronic problems (such as ‘baseline drift‘ or mechanical damping of the system by unnoticed air bubbles in the line or transducer dome
To maintain patency of the cannula a bag of normal saline or heparinised saline should be connected to the transducer tubing and kept under continuous pressure of 300mmHg thus facilitating a continuous flush of 3mls/hr
FACTORS AFFECTING THE MEASUREMENT OF CVP
zeroing ( Atmospheric pressure is thus the true zero value)
Leveling (relative to an arbitrary reference level)
where on the waveform to make the measurement :
A primary purpose for measuring CVP is the assessment of cardiac preload best measured at the base of the c wave
The base of the c wave is used because this is the final pressure in the ventricle before the onset of contraction and represents the final distending force for the ventricle, which is preload
actual pressure across an elastic structure ( transmural pressure )
we are restricted to making pressure measurements relative to atmospheric pressure.
To minimize this problem, pressures are made at end expiration when pleural pressure is closest to atmospheric pressure
INFORMATION FROM THE CVP WAVEFORM
Besides the actual pressure measurement there is much information that can be gained from examining the waveforms
WAVEFORMS IN CVP
consists of three upwards (a, c, & v waves) and two downward defections (x and y descents).
1. ‘a’ wave by right atrial contraction and occurs just after the P wave on the ECG.
2. The ‘c’ wave due to isovolumic ventricular contraction forcing the tricuspid valve to bulge upward into the RA
3. The pressure within the RA then decreases as the tricuspid valve is pulled away from the atrium during right ventricular ejection, forming the X descent .
4. The RA continues to fill during late ventricular systole, forming the V wave
5. The Y descent occurs when the tricuspid valve opens and blood from the RA empties rapidly into the RV during early diastole
THE CVP WAVEFORM
Reflects changes in right atrial pressure during the cardiac cycle
Early/Holosystolic Cannon V waves (C-V Waves ) TR
Prominent A and V waves, steep X, Y descent pericardial constriction (“M”sign)
The a and v waves
Typically the a wave is greater than or equal to the v wave in the CVP tracing of a normal person.
The y and x descents get deeper with a spontaneous inspiration; this can be used to time inspiratory events
With positive-pressure ventilation they get smaller
In patients following cardiac surgery the a wave is often smaller than the v wave and is likely due to decreased right ventricular function
M marks the appropriate place for measurement. The bottom tracing shows the overlap tracing with pulmonary artery pressure (PAP). This also can be used for timing the end of diastole and the place to make the measurement. shows a tracing from a young woman who had a major bleed following a hysterectomy
a small a wave and a massive v wave that begins with the onset of systole, which is consistent with the v wave being due to tricuspid regurgitation rather than filling of a noncompliant atrium
This CVP pattern would make insertion of a pulmonary artery catheter very difficult because it would be hard to recognize when the catheter has crossed the tricuspid valve.
This indicates severe TR. It must be appreciated that the peak of the v wave, which is 35 mmHg, will still have an important impact on upstream structures such as the liver and kidney
Recognition of the wave pattern can be helpful for interpreting rhythm disorders
Figure below shows the CVP tracing of a patient with episodes of ventricular tachycardia
Intermittent cannon a waves can indicate the presence of pacemaker syndrome
Cannon A waves
“ M sign” from Pericardial Constriction
The y descent
The presence of a large y descent indicates restriction of right ventricular filling
This can be due to intrinsic stiffness of the ventricular wall or occur in a ventricle that is excessively volume-loaded.
In either case, further volume loading is unlikely to change cardiac output.
Equalization of right and left atrial pressures suggests either cardiac tamponade or a restrictive process.
These diagnoses can be distinguished by examining the x and y descents
Loss of the x and y descent argues strongly for tamponade, whereas the presence of a prominent y descent argues against tamponade
The reason why the x and y descents are lost in tamponade is that the pericardial fluid keeps the pressure inside the pericardium constant.
The only time that fluid can enter the pericardial sac is during systole when the ventricles empty and allow the atria to fill.
During diastole this volume is transferred to the ventricle, again maintaining constant pericardial volume and pressure.
There is thus no period where pericardial pressure falls and thus no x or y descent.
Respiratory variation in CVP
The respiratory pattern in CVP can be used to predict fluid responsiveness
patients who have no inspiratory fall in CVP are on the flat part of their cardiac function curve and will not respond to fluids whereas patients who have an inspiratory fall in CVP are on the ascending part of the cardiac function curve and may or may not respond to fluids, depending how close they start to the plateau
Patients with an inspiratory fall in CVP are also more likely to have a fall in cardiac output with the application of PEEP
Label CVP lines with drugs/fluids etc. being infused in order to minimise the risk of accidental bolus injection
If not in use, flush the cannula regularly to help prevent thrombosis. A 500ml bag of 0.9% normal saline should be maintained at a pressure of 300mmHg.
Ensure all connections are secure to prevent exsanguination, introduction of infection and air emboli
Observe the insertion site frequently for signs of infection.
The length of the indwelling catheter should be recorded and regularly monitored.
CVP lines should be removed when clinically indicated
REMOVAL OF CENTRAL LINE
THIS IS AN ASEPTIC PROCEDURE
THE PATIENT SHOULD BE SUPINE WITH HEAD TILTED DOWN
ENSURE NO DRUGS ARE ATTACHED AND RUNNING VIA THE CENTRAL LINE
CUT THE STITCHES
SLOWLY REMOVE THE CATHETER
IF THERE IS RESISTENCE THEN CALL FOR ASSISTANCE
APPLY DIGITAL PRESSURE WITH GAUZE UNTIL BLEEDING STOPS
DRESS WITH GAUZE AND CLEAR DRESSING EG TEGADERM
PULMONARY ARTERY AND PULMONARY CAPILLARY WEDGE PRESSURE MONITORING
The introduction of pulmonary artery catheter (PAC) in clinical medicine one of the most popular and important advances in monitoring.
With this catheter:
PAP , PCWP & CVP can be measured easily
under most circumstances provides an accurate estimate of the diastolic filling (preload) of the left heart
Cardiac output determination using thermo-dilution technique is an equally important use of this catheter
The filling pressure of the right and left ventricle depends on the blood volume, venous tone, ventricular compliance, contractility and after load.
The left ventricle (LV) is less compliant with greater after load than the right ventricle (RV) and the left sided filling pressure is normally higher than the right
Under normal circumstances, the right side of the heart and lungs are merely passive conduits for blood and it is possible to discern a relationship between the central venous pressure and the left atrial pressure.
In health, it is possible to make reasonable assumptions about the relationship between the CVP and the LAP and manipulate the circulation according to the measurements of the CVP
However, in a critically ill patient and a patient with cardiovascular disease, no such assumptions can be made and conclusions about left heart based on measurements of CVP may be invalid
Since there are no valves between the pulmonary capillaries and the left atrium, PCWP is a reflection of the LAP .
During diastole , when mitral valve is open, the PCWP reflects LVEDP .
LVEDP is an index of left ventricular end-diastolic volume
Indications For PAP & PCWP Monitoring
A. Cardiac problems/surgery:
Poor LV function (EF<0.4; LVEDP> 18 mm Hg)
Pts with right heart failure
Procedures involving CPB
Complications of MI eg. MR, VSD, ventricular aneurysm.
Combined lesions eg. CAD+MR or CAD+AS
Complicated lesions eg. IHSS
Hemodynamically unstable pts requiring inotropes or IABP counterpulsation
Major procedures with large fluid shifts and/or blood loss in pts with CAD
B. Non-cardiac situations:
Shock of any cause or MOF
Severe pulmonary disease , COPD , PHTN, or PE
Pts requiring high levels of PEEP
Complicated surgical procedure
PA (Swan-Ganz) Catheter description
The standard 7F thermo-dilution pulmonary artery catheter consists of a single catheter 110 cm in length containing four lumina .
It is constructed of flexible, radio-opaque polyvinyl chloride.
10 cm increments are marked in black on the catheter beginning at the distal end.
At the distal end of the catheter is a latex balloon of 1.5 cc capacity.
When inflated, the balloon extends slightly beyond the tip of the catheter but does not obstruct it
Balloon is useful in three ways:
(1) it prevents the tip of the catheter from contacting the right ventricular wall during passage and hence reduces the incidence of arrhythmias during insertion
(2) it acts to float the catheter into the PA
(3) inflation of the balloon allows the measurement of PCWP
Distal catheter lumen terminates at the tip of the catheter;
It is used to:
measure chamber pressures; PAP & PCWP
obtain samples of the mixed venous blood
Proximal catheter lumen terminates 30 cm from the catheter tip placing it in the right atrium (RA) when the distal opening is in the PA. It:
carries the injectate necessary for cardiac output computation
Can be used to measure the CVP (RAP)
can be used to infuse vasoactive drugs
The third lumen carries the electrical leads for thermistor, which is positioned at the catheter surface, 4 cm proximal to the tip
PULMONARY ARTERY CATHETER
Components of a Pulmonary Artery Catheter
Components of Swan-Ganz
Normally has four  ports
Proximal port – [Blue] used to measure CVP/RAP and injectate port for measurement of cardiac output
Distal port – [Yellow] used to measure PAP
Balloon port – [Red] used to determine pulmonary wedge pressure;1.5 special syringe is connected
Infusion port – [White] used for fluid infusion
Types of PA catheters
The thermo dilution catheter:
is the one described above; using this catheter, thermo dilution cardiac output & other divided haemodynamic parameters may be measured
Some PAC’s have the capacity to provide intra cardiac pacing
3. Mixed venous oxygen saturation:
Special fiber-optic PAC can be used to monitor mixed venous oxygen saturation SVO2 continuously by the principle of absorption and reflectance of light through blood
The normal SVO2 is 75% and a 5– 10 % increase or decrease is considered significant
A significant decrease in SVO2 may be due to:
a decrease in the cardiac output
increase in metabolic rate
decrease in arterial oxygen saturation.
4. Ejection fraction catheter :
New-catheters with faster thermistor response times can be used to determine the right ventricular ejection fraction in addition to the cardiac output
5. Continuous cardiac output measurement :
Continuous cardiac output measuring PACs contain an integrated thermal filament at level of the RV
This filament is activated in a programmed sequence to provide small amounts of heat, which is then detected in the PA by a thermistor
The data by the device yields a rapidly updated, near continuous value for cardiac output
Insertion procedure :
is a simple, rapid and effective technique
Most anaesthesiologists and critical care physicians choose RIJV approach to insert PAC
Prior to insertion, all lumina of the PAC are flushed and distal port is connected to transducer system with a continuous wave from display
With the patient supine and in 30 degree Trendelenberg position, the head is turned to the left side
The appropriate area of the neck is surgically prepared and draped
The RIJV is identified with a 22G needle Then an 18G thin walled 5 cm teflon catheter is placed into the vein and threaded down the vessel for a short distance
The guide wire’s flexible end is passed through the 18 G catheter into the superior vena cava (SVC) and the 18 G catheter removed.
The skin hole around the guide wire is enlarged with a no. 11 scalpel blade to allow introduction of the dilator set
The dilator set consists of an internal vessel dilator and an external 10 G catheter sheath
This combination is passed into the IJV over the guide wire by a twisting motion until the catheter sheath is in the SVC
Then the 7 F Swan Ganz catheter , which has been filled with fluid and attached to a transducer, is passed through the sheath into the SVC
Location of the catheter tip in a central vein is confirmed by the pressure changes related to respiration or coughing
With the catheter in RA, the balloon is inflated with 1.5 ml of air and the PAC is advanced
Further advancement of the catheter will produce a dramatic change in the pressure tracing as the tip of the catheter enters the RV Pressure changes from that characteristic of RA to a phasic pressure in the range of 25 /0 mm Hg, typical of RV
The catheter is advanced through the RV until it enters the main PA
This can be recognized by an increase in the diastolic pressure (25/12mm Hg.) Usually there is no change in the systolic pressure
The catheter is advanced still further until it wedges in a branch o the PA
It will usually have the appearance of an atrial pressure pattern with a, c and v wave components transmitted retrogradely from LA(PCWP=8-12 mm Hg)
PCW position is verified by:
the characteristic waveform,
a mean pressure lower than the mean PAP and
the ability to withdraw arterialised blood.
After achieving a wedge position, the balloon is allowed to deflate
This should produce a typical PAP tracing
Reinflation of the balloon should reproduce the wedge tracing with 1.5 ml of air.
If less than 1.0 ml of air results in a wedge position , the catheter should be withdrawn to the point where 1-1.5 ml balloon inflation is associated with PCWP
INVASIVE HEMODYNAMIC MONITORING
PA Insertion Waves
Components of the Monitoring System
Bedside monitor – amplifier is located inside
The amplifier increases the size of signal
Transducer – changes the mechanical energy or pressures of pulse into electrical energy; should be level with the phlebostatic axis (intersecting lines from the 4 th ICS,mid axillary line)
Inverse relationship between afterload and CO ( ↑CO = ↓afterload; ↓CO = ↑afterload)
Compliance & diameter of the vessels into which the blood is ejected
Aortic impedance, peripheral vascular resistance, and blood viscosity
Decreased Afterload ( ↓ SVR)
Arterial dilatation from drugs such as nitroprusside, nitroglycerin, calcium channel blockers, beta blockers
Shock (septic, anaphylactic, neurogenic)
Increased Afterload ( ↑SVR)
Accomplished by vasoconstriction
Alpha agonists (pressors)
Levophed, Dopamine, Phenylephrine, Epinephrine
Low CO with hypovolemic or cardiogenic shock
An effect of obstruction
Increased Afterload ( ↑ PVR)
Conditions exhibiting increased PVR
End-stage COPD (Cor pulmonale)
Contractility = Inotropy
Inherent ability of cardiac muscle to contract
Reflected indirectly by stroke volume index (SVI) and the stroke work index for each ventricle (LVSWI & RVSWI)
Influenced by myocardial oxygenation & functionality; electrolyte balance; +/- inotropes; amounts of preload and afterload
Factors/M eds Increasing Contractility
Sympathic stimulation – “fight or flight”
Dopamine (5 – 10 mcg/kg/min)
Calcium; glucagon; caffeine
Digoxin (only oral inotrope)
Factors Decreasing Contractility
Conditions Resulting in PCWP and LVEDP Discrepancies
PCWP > LVEDP
Pos. press. ventilation
Incr. Intrathoracic pressure
Non-west zone III PAC placement
COPD, Incr PVR
Left atrial myxoma
Mitral valve disease
PCWP < LVEDP
AR (premature closure of mitral valve)
LVEDP > 25 mmHg
ASA Guidelines for PAC Use
Thermodilution Cardiac Output
Cardiac output-monitored in patients who are hemodynamically unstable.
Usually the PA catheter is used to measure CO
Thermodilution technique is often used-a known amount of solution(saline or d5w) of known temperature(room or chilled) is injected rapidly into the right atrial lumen of the PA catheter. A drop in blood temp is detected by a thermister embedded in the catheter tip in the PA.
CO is then calculated by a computer from the temperature waveform
CO or CI will be decreased in hypovolemia, shock, heart failure
Increases may be associated with sepsis prior to septic shock
Mixed venous oxygen saturation
PA catheters have a sensor located on them which measures oxygen saturation of hemoglobin of pulmonary artery blood which is mixed venous blood
Normal SVO2 at rest is 60-80%
Blood gases may also be drawn from the PA line to determine mixed venous blood gas analysis and SVO2
Don’t expect to be an expert--requires practice and experience as well as vast knowledge of hemodynamics.