The Swan-Ganz Catheter
What is a Swan? • Full name: Swan-Ganz Catheter• Pulmonary Artery (PA) Catheter = right heart catheter• Used it to monitor a patient’s hemodynamics when we cant answer the question using noninvasive/clinical measures • Useful to measure right atrial, pulmonary artery, right ventricular pressures and indirectly measure left atrial pressures, cardiac output and systemic vascular resistance
Why use a Swan? • Differentiation between causes of shock>cardiogenic, hypovolemic, septic • Differentiation between causes of pulmonary edema>cardiogenic versus noncardiogenic • Diagnosis of pericardial tamponade• Diagnosis of intracardiac shunt• Evaluation/Management of pulmonary hypertension• Diagnosis of lymphangitic spread of tumor and fat embolism • Management of complicated MI, HF• Determine need for vasopressor/inotropic therapy• Fluid Status>in GI bleed, renal failure, sepsis• Ventilator management>determining the best PEEP
Some history… • First pulm catheters were placed in 1940s• 1970-William Ganz and Harold Swan introduced this catheter. Pulmonary artery Catheter that is balloon-tipped and flow directed, placed bedside • Revolutionized catheters>moved from diagnosis only to help in management. No clinical trials were done to see if they improved mortality. Benefit was assumed • 1987- nonrandomized trials:showed mortality was higher in patients with an acute MI who had a Swan placed • 1990s-Ontorio Intensive Care Group attempted a RCT for use of Swans>not done b/c many clinicians felt unethical to withhold Swan placement because accurate diagnosis=accurate treatment=better prognosis????
Is it unethical to withhold Swan Placement? And are they better at predicting clinical outcomes?• 1996 observational study of RHC in first 24 hours said NO. 1. Placement led to worse patient outcomes b/c of complications of placement or misinterpretation of data 2. Use of catheter might be a marker of more aggressive care, which is associated with higher mortality 3. Changes in therapy in response to the information might have led to high mortality (i.e. using pressors) 4. Study might not have adequately adjusted for confounding factors 5. Only looked at SGC placed in first 24 hours. • Connors AF Jr, Speroff T, Dawson NV, et al. The effectiveness of right heart catheterization in the initial care of critically ill patients. JAMA 1996;276:889-897
Randomized, Control ed Trial of the Use of Pulmonary-Artery Catheters in High-Risk Surgical Patients. Sandman et al. NEJM-Jan, 2003 • 1994 high-risk surgical patients underwent randomization for PA catheters (RCT) • Preop placement, for elective or urgent surgery• Looked at 6mo and 12 mo mortality• No difference b/t PA catheter group from placebo in terms of mortality and length of hospitalization • Increased risk of PE in the catheter group and thus, PA catheters may be associated with increased morbidity
Escape Trial • The value of Swan-Ganz catheterization to guide tailored therapy in heart failure patients is an area of controversy. • The randomized ESCAPE trial showed no benefit on a primary end point of the number of days alive and out of the hospital at six months JAMA. 2005;294:1625-1633.
To Swan or Not to Swan? INDIVIDUALIZE CARE Understanding Swan Ganz Catheters=Understanding Hemodynamics
Basic Catheter Features • Made of polyvinylchloride and has a pliable shaft that softens at body temperature • Catheter is 110 cm and external diameter is either 5 or 7 French (1 French=0.0335mm) • Balloon is fastened 1-2mm from the tip and when inflated it guides the catheter (using fluid dynamic drag) from greater intrathoracic veins through tight heart into pulmonary artery • Thermistor-4cm proximal to the tip, measures temperature>important for determining cardiac output
• Typically catheters have 4 ports: 1. White port with blue wire is the proximal port> terminates at 30cm from tip of catheter and is used to measure right atrium pressures 2. White port, yellow wire is the PAD distal port 3. White port with red wire is for balloon inflation 4. Last port has the connection to the thermodilution cardiac output computer> contains the electrical leads for thermistor.
Insertion Techniques • Average time from decision to use PA catheter until onset of catheter based treatment is 120 minutes • Goal: get the catheter to the pulmonary artery• Cordis into right internal jugular vein or left subclavian allows easiest passage • Swan should be oriented ex-vivo to approximate the course in the body • Catheter goes through an introducer and into the vein. The balloon stays closed until we reach the right atrium. • When we reach the right atrium (20cm), balloon should be inflated to reduce possibility of injury to the myocardium. • Then the balloon should be moved quickly through the right ventricle (30cm)> and then pulmonary artery (40cm) and PCWP (50cm) FROM SUBCLAVIAN/IJ APPROACH
How do you know you are in the Right Atrium?>>20 cm Normal right atrial presssure is 0-6mmHg. Normal oxygen content 15%Normal O2 saturation 75% a=atrial contraction.c=sudden motion of the AV ring toward the right atriumx descent=atrial relaxationv=pressure generated by venous fillingof the right atriumy descent=rapid emptying of the RA into RV
What Elevates the Right Atrial Pressure? • RV infarct• Pulmonary hypertension• Pulmonary stenosis• Left to right shunt• Tricuspid valvular disease• Left heart failure
Prominent RA pulsations • Prominent a wave: • Tricuspid stenosis • Cannon a wave: • AV dissociation or Ventricular tachycardia • Prominent v wave: • Tricuspid regurgitation or VSD
How do you know you are in the right ventricle? 30cm RV systolic=17-30RV diastolic=0-6RV O2 content=15%RV O2 saturation 75%
What Increases RV Pressures? • RV failure• Pulmonary hypertension• Pulmonary stenosis• Pulmonary Embolism• Cardiomyopathy• Cardiac tamponade• Cardiac constriction
How do you know you are in the pulmonary artery? Normal PA pressure, systolic 15-30Normal PA pressure, diastolic 5-13O2 content 15%O2 saturation 75%
What Elevates PA pressure? • Volume Overload (backflow)• Primary lung disease• Primary pulmonary hypertension• Pulmonary Embolism• Left to right shunt• Mitral Valve Disease
THE WEDGE: What is the Pulmonary Artery Wedge Pressure? The measurement is obtained when the inflated balloon impacts into a slightlysmaller branch of the pulmonary artery. This is where the arterial pressure exceeds the venous pressure and the venous pressure exceeds the alveolar pressure, thereby creating a continuous column of blood from the catheter tip to the left atrium when the balloon is inflated. Pulmonary venous pressure is the best indicator of left atrial pressure except when there is venoocclusive disease. AND ONLYWHEN THE PA CATHETER IS IN ZONE 3 of the lung.
Inflation of the Balloon for PCWP Tracing Pulmonary artery wedge 2-12 PCWP tracing looks like RA tracing Pulmonary vein O2 content 20% except that the v wave is slightly higher Pulmonary vein O2 sat 98% than the a wave (opposite of RA).Also, b/c of the time required for LA mechanical events, PAWP waveforms are further delayed when recorded by EKG
What Increases PCWP? • PEEP (minimally)• LV failure• Cardiac tamponade• Aortic Insufficiency• Mitral regurgitation• VSD
Prominent PCWP Tracings • Prominent a waves: -mitral stenosis-LV systolic dysfunction-LV overload-Decreased LV compliance • Prominent v waves -mitral regurgitation-VSD
Calculation of Cardiac Output Thermodilution versus Ficks method •Thermodilution: Add an indicator substance (5ml of dextrose or saline) that is cooler than blood. Indicator in injected through the proximal port of the PA catheter and mixes with the blood in the RV. The mixing lowers the temperature of the flowing blood which is carried to the distal thermistor port. The thermistor records the temperature change and electronically displays a temperature/time curve. The area under the curve is inversely proportional to the flow rate in the pulmonary artery which equals the cardiac output in absence of intracardiac shunt -sources of error with thermodilution are seen with tricuspid regurgitation and intracardiac shunts
Fick’s Method • General principle: the release or uptake of a substance by an organ equals the product of the bloodflow through that organ times the difference of arteriovenous concentrations of that substance. • CO= O2 consumption (ml/min) — arterial O2 content(PCWP)-mixed venous (PA) O2 content• O2 consumption varies according to individual, by age and sex. Usually estimated as being 250mL for a 70kg male. Generally estimated at 130mL x BSA • Blood O2 content=% saturation X Hb x 1.39 ml O2/gm Hb• Errors: assumptions of O2 consumption, wont work at all with intracardiac shunts. But works better with TR
Cardiac Output/Index • What is cardiac output?• What is normal cardiac output?• What is normal cardiac index?
Effects of PEEP • Effects of positive end-expiratory pressure — Alveolar pressure will not return to atmospheric pressure at end-expiration in the presence of positive end-expiratory pressure (PEEP), a change that can affect the measurement of intravascular pressures. • The effects of PEEP are generally felt not to be clinically significant. • PEEP does affect right sided pressures (i.e. RA or CVP).
Systemic Vascular Resistance (SVR) • Refers to the resistance to blood flow offered by all of the systemic vascular resistance, excluding the pulmonary vasculature. • This is sometimes referred as total peripheral resistance (TPR). • Mechanisms that cause vasoconstriction increase SVR, and those mechanisms that cause vasodilation decrease SVR. • SVR can be calculated if cardiac output (CO), mean arterial pressure (MAP), and central venous pressure (CVP) are known. • SVR = 80 X (MAP – CVP) ÷ CO• Normal Systemic Vascular Resistance is 800-1200 (dyne*sec)/cm5
Zeroing is performed by opening the system to air to establish atmospheric pressure as zero. Referencing (or leveling) is accomplished by placing the air-fluid interface of the catheter (or the transducer) at a specific point to negate the effects of the weight of the catheter tubing and fluid column
Not an Entirely Benign Lign… •Insertion of an introducer to provide venous access>Pntx, bleeding, infection•Passage of the Swan through the introducer>minimized by inflating the balloon tip after entering the right atrium -Sustained ventricular arrythmias, occur in 0-3% pts-RBBB develops in about 5% of catheter insertions, placing pts with a preexisting LBBB in complete heart block. RBBB is usually temporary. -Knotting catheter-can occur during insertion if loops are allowed to form in one of the cardiac chambers. When knotting occurs, can usually remove transvenously but some require venotomy or surgical extraction.•Maintenance of the catheter>Inflating balloon when catheter has moved distally>causing pulmonary artery perforation. Mortality >30%, usu requires thoracotomy
Not Without Risks??? •Don’t leave balloon inflated in wedge position for extended period of time>can cause pulmonary infarction• Thromboembolic events can occur with the catheter acting as a nidus for thrombus formation. Less common with heparin bonded catheters•Misinterpretation of the data •Mural thrombi can be induced by inflammation of infection of a vessel wall, seen in 33% of patients at autopsy•Sterile vegetations, seen in 90% of patients•Endocarditis of the pulmonic valve•Rupture of the catheter balloon and consequent air embolism
THINK HARD BEFORE YOU STICK
Sample Questions • BP 80/40 HR 120• RA 20 • RV 50/23• PA 70/30• PCWP 28• CO 2.0• SVR 1600
• BP 80/40 HR 120• RA 20 • PA 70/33• PCWP 12• CO 2.0• SVR 1200
• BP 80/40 HR 120• RA 5• RV 18/5• PA 25/15• PCWP 10 • CO 2.0• SVR 1600
• BP 80/40 HR 120• RA 12• PA 25/12• PCWP 14• CO 9• SVR 500
Case Scenario •55 yo male comes into the ED.•
Cath showed 100% RCA occlusion. Treated with O2, heparin, MSO4 and his condition improves. 48 hours later, he becomes pale, diaphoretic and oliguric. Vitals: HR 120bpm, RR 24/min and BP 88/55. PE: JVP+ angle of jaw, +RUQ tenderness, lungs clear. +S3, Grade ¼ holosystolic murmur at LLSB. +LE edema
EKG: unchanged Right heart cath placed which showed:RA 20 mmHgRV 40/18 mmHgPAP 25/15 mmHgPCWP 12 mmHgCO 2L/min RA tracing:
WHAT DOES THIS PT HAVE? a. Papillary muscle ruptureb. Massive PEc. Cardiac Tamponaded. Rupture of the IV septume. RV infarct
Ngorogoro Crater, Tanzania