Monitoring in Cardiac Anaesthesia:PCWP

Dr Abhishek RathoreModerator : Col Ramprasad

• History• Pulmonary Artery Catheter• Insertion of PAC• Indications• Waveforms• Complications• Pitfalls

History

• Lewis Daxter (1945): first pulmonary aretry catherization

• Swan, Ganz and colleagues (1970): Flow directed PA catheter

• Hemodynamic assessment of patients with acute MI.

Pulmonary artery catheterization

• Site:– Any central vein– Rt IJV most preferred– For other sites extra distance required• Lt IJV/ Rt & Lt EJV : 5-10 cm• Femoral veins : 15cm• Antecubital veins : 30-35 cms

Pulmonary Artery Catheter

PA Distal

Proximal Injectate

RA infusion port

Thermistor port

Balloon inflationport

The standard catheter is 7.5 FR and 110 cm long. Maximal balloon volume 1.5cc

Pulmonary Artery Catheter

• 7.0 to 9.0 Fr• 110 cm length• 10 cm marking• 4 internal lumens• Distal port used for PAP• 2nd lumen: CVP monitoring• 3rd lumen : balloon near the tip• 4th lumen: houses wires for temperature

thermistor

Equipment

• Informed consent• 7.5 Fr pulmonary artery catheter (PAC)• 8.5 Fr introducer set with “side-port”• Central line insertion tray and central line

dressing kit with sterile dressing• Flush solution, pressure bag, disposable

pressure tubing with transducer• Transducer holder

Quality Control Issues for PA CathetersQuality Control Issues for PA Catheters

• “Zero” system at setup• Do square flush wave test, after zeroing, obtaining blood

samples, with tubing changes, or if waveform distorted.• Prime tubing and stopcocks by gravity.• Maintain continuous flush system.• Use standard (universal) precautions, aseptic technique• Measure all values at end-expiration.

Referencing the “zeroing” stopcock to Phlebostatic Axis

The phlebostatic axis is the approximate level of the left atrium. It is locatedmidway between the anterior-posterior chest wall at the 4th intercostal space.The patient need not be flat, but must be supine.

Inserting a PAC

Indications

• Surgical patients associated with high risk of complications from hemodynamic changes

• Advance cardiopulmonary diseases• Goal directed fluid therapy

Swan Ganz Physiology.mp4

Waveforms identified bymovement of the catheter throughthe right side of the heart into the

pulmonary artery and capillary bed:Right atrial (RA)

Right ventricular (RV)Pulmonary artery pressure (PAP)

Pulmonary capillary wedge pressure(PCWP) or

Pulmonary artery wedge pressure (PAWP)

a wave follows “P” wave on ECG v wave follows the QRS complex on ECG RAP = mean (average) of a wave

Right atrial pressure (RAP) is measured by the distal tip of the PAC on insertion or by the proximal port post insertion. The waveform has two primary characteristics: “a” wave and “v” wave.

a = atrial systolev = ventricular systole

Right Atrium

Tricuspid valve

Pulmonic valve

P

QRS

Measurement of Right Atrial Pressure (RA)from Pulmonary Artery Catheter

Measurement of Right Atrial Pressure (RA)from Pulmonary Artery Catheter

Normal RAP = 2 – 6 mmHg

The “a” wave represents atrial contraction and estimates atrial filling at end-diastole.

Locate the “a” wave by alignment with the PR interval on ECG.Measure the mean (average) of the height of the “a” wave and

the bottom of the “a’ wave at end-expiration.

RA Waveform

“c” wave = closure of the tricuspid valve“x” decent = follows closure of the tricuspid valve, “y” decent = follows closure of the pulmonic valve

Alterations in RA Pressure

• Reflects filling volume of the right atrium• Low pressure consistent with hypovolemia:– Trauma-> blood loss– Dehydration– Loss of fluid from drains– Vomiting, diarrhea– Burns – 3rd spacing of fluid

• Consistent with tachycardia, ↓ urine output, dry skin & mucous membranes

Clinical Situations Consistent with Elevations in RA Pressures

Clinical Situations Consistent with Elevations in RA Pressures

• Tricuspid stenosis, regurgitation• RV ischemia or failure• Pulmonary hypertension• Pulmonic stenosis• Pulmonary embolism• Atrial ventricular dissociation with loss of

synchrony – Atrial arrythmias, A-V conduction blocks)

Systolic pressure

Diastolicpressure

Onset of systole follows QRS complex on ECGEnd diastole occurs at the onset of systole.

Right ventricular pressure (RVP) is measured from the distal tip of PACon insertion or from the RV port (gray) post insertion. RVP has a systolic and diastolic component.

QRS

Right ventricle

RV Waveform

Systole

Diastole

Alterations in RVPReflects filling volume of right ventricle

Normal RV = 25-30/0-5 mmHg• Low pressure consistent with low volume

– Usually accompanies low RAP• Elevation associated with:

– Hypervolemia– Pulmonary embolism– Outflow obstruction– RV infarct/failure– Pericarditis/tamponade– LV failure– Primary and secondary pulmonary hypertension (PHTN)– Pulmonic stenosis– COPD

Pulmonary artery pressure (PAP) is measured from the distal tipof PAC on insertion and distal tip post insertion. It has a systolicand diastolic component.

PAsystolic

PAdiastolic

Dicrotic notchRepresents closure of the pulmonic valve

Systolic pressure follows QRS on ECG. Diastole begins at the closure of the pulmonic valve and continues to next onset of systole.

Pulmonic valve

QRS

Alterations in PAPRepresents filling volume in the pulmonary artery and resistance

to flow within the pulmonary circuitNormal PAP = 20-30/8-15 mmHg

• Low pressure consistent with hypovolemia– Consistent with ↓ RAP and ↓ RVP

• High pressure consistent with– PHTN– COPD– Acute respiratory distress syndrome (ARDS)– Pulmonary embolism (PE)– Mitral stenosis– Left ventricular heart failure

PAP Waveform

Pulmonary capillary wedge pressure (PCWP) or pulmonary artery wedge pressure (PAWP) is measured from the distal port of PAC with balloon inflated.

The PCWP represents left atrial filling pressure reflected through the pulmonary circuit. Normal value 8-14 mmHg.PCWP = mean (average) of “a” wave

a = atrial systolev = ventricular systole

Catheter tip looks “through” the pulmonary circulation to “see” the left atrial pressure.

PCWP indirectly measures left atrial pressure

Measurement of PCWP from Balloon PortMeasurement of PCWP from Balloon Port

• Inflate balloon with only as much air as needed to create a change in the waveform (no more than 1.5cc air).

• Observe for change in waveform.• Locate the “a” wave on the PCWP waveform.

– Use the QRS as a marker to detect the “a” waveform.• Measure the mean of the “a” wave to obtain the PCWP• PA diastolic (PAD) should correlate to the PCWP and be 0-5

mmHg greater. (PAD ≥ PCWP)• High levels of positive end expiration pressure (PEEP) will raise

the PCWP.

Alterations of PCWPAlterations of PCWP

• Low pressure consistent with hypovolemia• Elevations consistent with:– Mitral stenosis/regurgitation– Aortic stenosis/regurgitation– Acute LV ischemia/infarct– LV failure– Atrial ventricular dissociation with loss of synchrony

• Both RA and PCWP elevated in cardiac tamponade, constrictive pericarditis, and hypervolemia

Once inserted balloon should remain DEFLATED and ONLYreinflated for periodic measurement of PCWP. PAP waveform should be displayed at all other times.

Distal tip(Yellow)

Proximal tip(Blue)

Right ventricular Port (Gray)

Distal tip measures PAP and PCWPProximal tip measures RA and is site for CO measurement and fluid administration

Right ventricular port site for fluid administration

RA infusionport (white)

Complications of PA Catheters– Air embolism– Infection– Atrial & ventricular arrhythmias– Hemoptysis ( caused by excessive expansion of the balloon

in the wedge position)– Areas of infarction– Thrombus formation /PE– Local endothelial damage– Pulmonary rupture– Thrombophlebitis– Pneumothorax

Summary of Pulmonary Artery Pressure Waveforms

Normal 2-6 mmHg Normal 20-30/0-5 Normal 20-30/8-14 Normal 8-14 mmHg mmHg mmHg

Pitfalls

• Data provided by PAC may not be accurate• Risks for PAC itself• Harm due to knowledge deficiet• Data may not be useful in managing critically

ill patients• May result in overtreatment

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Phlebostatic axis• Reference levels for various body positions. A, Supine/prone. The

reference point is the phlebostatic axis, which is the intersection of 2 reference lines: first, an imaginary line from the fourth intercostal space at the point where the space joins the sternum, drawn out to the side of the body; second, a line drawn midway between the anterior and posterior surfaces of the chest. B, Supine with the head of the bed elevated. The phlebostatic level is a horizontal line through the phlebostatic axis. Measurements of pulmonary artery pressure and central venous pressure can be obtained at backrest elevations of up to 60°. C, 30° lateral position. The reference point is one-half the distance from the left sternal border to the surface of the bed. (Based on data from VanEtta et al.6) D, 90° lateral position. In the 90° right lateral position, the reference point is the intersection of the fourth intercostal space at the midsternum. In the 90° left lateral position, the reference point is the intersection of the fourth intercostal space at the left parasternal border.