Pulmonary artery catheter for cardiac pressure monitoring and its role in anesthetic practice

Dr. Shalini Saini

University College of Medical Sciences & GTB Hospital, Delhi

Pulmonary artery catheter

• Introduction• Insertion technique• Indications • Complications• Abnormal pulmonary artery and wedge pressure waveform

Introduction

• In 1970, Swan,Ganz and colleague introduced pulmonary artery catheter

Pulmonary artery catheter

• Standard : 7-9 Fr circumference• 110cm length at 10cm intervals• Four internal lumen-1. Distal-pulmonary artery pressure monitoring2. Proximal-30cm for CVP monitoring3. It leads to balloon near the tip4. It houses wires for a temperature thermistor

Uses of pulmonary artery catheter

• Assessment of volume status in patients undergoing major surgeries

• Cardiac output measurement by thermodilution technique• Various hemodynamic parameters-pulmonary artery pressure,

pulmonary capillary wedge presssure,CVP,systemic vascular resistance, pulmonary vascular resistance.

• Respiratory or oxygen transport measurement-mixed venous oximetry.

Insertion

Sites of insertion• Right internal jugular vein (preferred)• Left internal jugular vein (2nd choice)• Subclavian vein (disadvantages)• External jugular vein ( superficial location but tortous)• Antecubital vein • Femoral vein

*After successful venous cannulation, there might be difficulty in advancement of the catheter due to abnormal venous anatomy.

- most common: persistence of left superior vena cava.

RA RV PA

IJV-right 20cm 30cm 45cm

left 25cm 35cm 50cm

Antecubital –rt 50cm 65cm 80cm

-lt 55cm 70cm 85cm

Femoral v 40cm 50cm 65cm

Subclavian v 10cm 25cm 40cm

Distances to right atrium, right ventricle and pulmonary artery

Pressure Average (mm Hg) Range (mm Hg)Right Atriuma wave 6 2-7v wave 5 2-7Mean 3 1-5Right VentriclePeak systolic 25 15-30End-diastolic 6 1-7Pulmonary ArteryPeak systolic 25 15-30End-diastolic 9 4-12Mean 15 9-19Pulmonary Artery WedgeMean 9 4-12Left AtriumMean 8 2-12Left VentriclePeak systolic 130 90-140End-diastolic 8 5-12

   

Normal Cardiovascular Pressures

Wave form recorded during passage of pulmonary artery catheter

• Right atrial pressure resembles central venous pressure waveform• Right ventricular pressure shows higher systolic pressure• Pulmonary artery pressure shows diastolic step up• Pulmonary artery wedge pressure similar morphology as right atrial pressure but a,c v waves appear later

Temporal relationships between systemic arterial pressure,pulmonary artery pressure, central venous pressure and

pulmonary artery wedge pressure

-PAP upstroke precedes radial artery pressure upstroke -Wedge pressure a wave follows ECG R wave

Three-zone model of pulmonary vasculature

-described by West and colleague-tip of PAC should lie in zone3-supine position favours zone3 condition

Correlations of RAP to LVEDV

Indications

1. Patients undergoing cardiac surgery with• Poor left ventricular compliance(ejection fration <0.4, LVEDP>18mm hg)• Left wall motion abnormality• Recent MI (<6 Months)• Left main coronary lesion• Valvular lesion• Presence of pulmonary artery hypertension

2. Major procedures involving large fluid shifts or blood loss in patients with-

• Cardiogenic or septic shock or with multiple organ failure• Hemodynamic instability requiring ionotropes or intra-aortic

balloon counterpulsation• Hepatic transplantation• Massive ascites requiring major surgery• Surgery of aorta requiring cross-clamping• Large abdomino-perineal resection etc.

3. Intensive care unit• To measure pulmonary artery and pulmonary capillary wedge pressure • To measure cardiac output by thermodilution• To obtain intracavitary electrocardiogram• To perform atrial or ventricular pacing• To allow infusion of drugs• To perform angiography• To detect venous air embolism

4. Continous mixed venous oximetry- To assess the adequacy of perfusion

Recommendations for perioperative use of PACs(AHA 2007 guidelines)

• Class 2b-(level of evidence:B) Use of PAC is reasonable in patients at risk for major hemodynamic

disturbances easily detected by PAC. However, decision must be based on three parameters-

a. disease b. surgical procedure c. practice setting (Experience & interpretation) • Class 3-(level of evidence:A) Routine use of PAC perioperatively, especially low risk of hemodynamic

disturbances, is not recommended.

Pulmonary Artery Catheterisation and outcome controversies

• PAC use in 5735 patients in first 24 hrs intensive care associated with

increased mortality, hospital stay and cost.(Connors etal,1997)• Three trials including 3468 patients showed no effect on mortality but

higher incidence of adverse effects(Harvey etal,2005; The ESCAPE Trial,2005; Sandham etal,2003)

• A review of 53312 patients from National Trauma Data Bank showed -No mortality benefit in patients treated with PAC -Injury scale greater: mortality decreased(Friese etal,2006)• In mixed medical and surgical population,APACHE scores <25 -increased mortality >31 -significant benefit (Chittock etal,2004)

• A group of experienced cardiac anesthesiologists and surgeons

blinded to information from pulmonary artery catheterisation during CABG surgery were unaware of 65% of severe hemodynamic abnormalities.(Waller and Kaplan)• ICU physicians were unable to accurately predict hemodynamic data on clinical grounds and 60% made at least one change in therapy and 33% changed their diagnosis based on PAC data.(Iberti and Fisher)

Contraindications (Kaplan)

Absolute contraindications • Tricuspid or pulmonary stenosis• Right atrial or ventricular mass• Tetralogy of Fallot

Relative contraindications• Severe arrhythmias• Coagulopathy• Newly inserted pacemaker wires

Complications

1. Catheterisation a. Arrythmia-primary complication -most common premature ventricular contractions -ventricular fibrillationb. Right bundle branch blockc. Complete heart block Treatment- balloon deflated and catheter withdrawn to right atrium

2. Catheter residence

a. Catheter knotting -suspected when difficulty in withdrawing

-diagnosed with chest x-ray -untied by radiologist

b.Thromboembolism –rising incidence -increased with antifibrinolytic drugs c. Pulmonary infarction

d. Infection ,endocarditis

e. Endocardial damage, cardiac valve injury

f. Thrombocytopenia (heparin induced)

g. Pulmonary artery rupture -Incidence: 0.064%-0.20% -Increased risk: female sex, hypothermia, anticoagulation, advanced age, pulmonary hypertension, mitral stenosis, coagulopathy, distal placement catheter, balloon hyperinflation -Hallmark:hemoptysis and exsanguination -Treatment: 1. Resuscitation-adequate oxygenation and ventilation 2. If hemorrhage minimal,with coagulopathy-correct coagulopathy 3. Protection of uninvolved lung by-tilting patient to affected side, placement of double lumen endotracheal tube 4. Stop hemorrhage- apply PEEP, Bronchial blockers, resection. 5. Severe hemorrhage with recurrent bleeding-transcatheter coil embolisation.

Abnormal pressure waveforms

A. Artifact Overwedging occurs when balloon overinflated/distal migration of cathter/eccentric balloon inflation.

B.Pathophysiologic changes

1.Mitral regurgitation

-Tall v waves in waveform with bifid appearance-PAP upstroke steeper-Wedge pressure prominent v wave with gradual upstroke-Wedge pressure overestimates left ventricular filling pressure-Tall v wave:hypervolemia,CHF, VSD.

2.Mitral stenosis

-Mean wedge pressure increased-y descent slurred due to obstruction to bloood flow-Similar abnormalities-left atrial myxoma, left ventricle infarction, pericardial constriction,aortic stenosis, systemic hypertension

3.Pericardial constriction

-prominent a and v waves-steep x and y descent-M or W configuration in CVP trace-diastolic ‘dip and plateau’ pattern or square root sign due to early diastolic ventricular filling-mid diastolic h wave (plateau) due to interruption in flow due to restrictive shell

4.Myocardial ischemia

• First time used in patient with acute MI.• PAP normal relatively• PAWP slightly elevated• PAWP morphology abnormal-Tall a waves due to diastolic dysfunction

Condition Site of Discrepancy Cause of Discrepancy

Positive end-expiratory pressure Mean PAWP > mean LAP Creation of lung zone 1 or 2 or pericardial pressure changes

Pulmonary arterial hypertension PADP > mean PAWP Increased pulmonary vascular resistance

Pulmonary veno-occlusive disease Mean PAWP > mean LAP Obstruction to flow in large pulmonary veins

Mitral stenosis Mean LAP > LVEDP Obstruction to flow across the mitral valve

Mitral regurgitation Mean LAP > LVEDPRetrograde systolic v wave raises mean atrial pressure

Ventricular septal defect Mean LAP > LVEDPAntegrade systolic v wave raises mean atrial pressure

Tachycardia PADP > mean LAP > LVEDPShort diastole creates pulmonary vascular and mitral valve gradients

Overestimation of Left Ventricular End-Diastolic Pressure

Condition Site of Discrepacy Cause of Discrepancy

Diastolic dysfunction Mean LAP < LVEDP Increased end-diastolic a wave

Aortic regurgitation LAP a wave < LVEDP Mitral valve closure before end-diastole

Pulmonic regurgitation PADP < LVEDP Bidirectional runoff for pulmonary artery flow

Right bundle branch block PADP < LVEDP Delayed pulmonic valve opening

After pneumonectomy PAWP < LAP or LVEDP Obstruction of pulmonary blood flow

 Underestimation of Left Ventricular End-Diastolic Pressure

Additional uses of pulmonary artery catheter1. Thermodilution cardiac output monitoring• Principle: Stewart-Hamilton equation Q = V(Tb-Ti)K1.K2 Tb(t)dt Q = Cardiac output V = Injectate volume Tb = Blood temperature Ti = Injectate temperature K1 = Density factor: (sp heat)(sp gravity)injectate (sp heat)(sp gravity)blood K2 = A computation constant which includes heat change in transit,dead space of the catheter,injection rate, adjusts units to l/min Tb(t)dt = change in blood temperature as a function of time

2. Mixed venous oximetry Svo2 = Sao2- Vo2 / Q×1.36×Hb

Svo2 = mixed venous hemoglobin saturation(%)

Sao2 = arterial hemoglobin saturation(%)

Vo2 = oxygen consumption(ml/min)

Q = Cardiac output (l/min) Hb = hemoglobin concentration(g/dl) * Mixed venous hemoglobin saturation determined by sampling from PAC either intermittently or continous

3. Right Ventricular Ejection Fraction RVEDV = SV/RVEF RVEDV = Right ventricular end diastolic volume (ml) SV = Stroke volume RVEF = Right ventricular ejection fraction

4. Derived Hemodynamic Variables SVR = MAP-CVP × 80 CO PVR = MPAP-PAWP×80 CO SVR = systemic vascular resistance PVR = pulmonary vascular resistance MAP = mean arterial pressure CVP = central venous pressure MPAP = mean pulmonary artery pressure PAWP = pulmonary artery wedge pressure CO = cardiac output

References

• Ronald.D.Miller: Pulmonary artery catheter monitoring. Cardiovascular monitoring 7th ed:1297-1314.

• Kaplan: Anesthesia techniques for cardiac surgical procedures;399-408.

• Circulation. 2007;116:e418-e500• Blitt: Monitoring. Pulmonary artery cathterisation;221-263.

Thank you