W5 Bedside Pulmonary Artery Catheterization
Before Procedure
Anatomy
Procedure
• Check the patient’s electrocardiogram (ECG), coagulation profile, and serum electrolytes panel. One should consider correcting major clotting disorders. If the patient already has a pacemaker, it may be better to place the catheter under radiographic guidance to avoid dislodging it.
• Connect the distal lumen to the pressure-monitoring system, and flush all lumens with sterile saline solution.
• Insert introducer into a central vein, preferably the internal jugular or subclavian, using the Seldinger technique.
• Advance the catheter for another 15 cm. It should pass into the right ventricle (RV) and give an RV pressure waveform.
• Once the catheter is in place, check the position with a chest radiograph. In the vast majority of cases, the tip is in the right lung. The tip should be within 2 cm of the cardiac shadow.
• All pressures should be measured at end expiration, when alveolar pressure should be closest to atmospheric pressure.
Procedural Precautions
• Do not insert large lengths of catheter without observing a pressure change, because this maneuver may lead to looping and knotting of the catheter.
• There may be difficulties in reaching the RV or PA owing to RA or RV dilatation, tricuspid regurgitation, or abnormalities of the central veins. An option may be to advance the catheter with the balloon partially deflated during inspiration, repositioning the patient in a head-up or right lateral position, or flushing the catheter with iced saline to make it more rigid.
• If the PAOP trace is obtained when the balloon is inflated with less than 1 mL of air, or if there is a progressive elevation of pressure when the balloon is inflated (“overwedging”), the catheter tip is too advanced and should be withdrawn by a few centimeters to decrease the risk of PA rupture/infarction.
After Procedure
Postprocedure Care
Interpretation Of Measured Pressures
• The pulmonary artery waveform has a systolic and diastolic pressure with a dicrotic notch corresponding to closure of the pulmonary valve.
• The PAOP, like the central venous pressure (CVP), has a venous waveform with a, c, and v waves corresponding to LA contraction, closure of the mitral valve, and passive LA filling, respectively.
• The a wave coincides with the point of maximal filling of the LV and is therefore the value that should be used for measurement of LVEDP. A large-amplitude a wave with an increase in measured PAOP suggests LV ischemia and decreased ventricular compliance.
• A large v wave on the PAOP trace represents mitral regurgitation or an acute volume load to the LA, as occurs with septal rupture. The PAOP level should be measured without consideration for this v wave.
• The RA pressure waveform can look like an RV waveform if there is significant tricuspid regurgitation.
Measurement Of Cardiac Output With The Pac
• Measurement is based on the indicator dilution principle: when an indicator substance is added to a stream of flowing blood, the flow rate is inversely proportional to the mean concentration of the indicator at a downstream site. In the case of thermodilution, the indicator used is temperature, using either a bolus of cold injectate (cold thermodilution) or a thermal filament to generate heat (warm thermodilution).
• The old technique included a 10-mL bolus of room temperature 5% dextrose solution or saline injected over 4 seconds through the proximal port of the PAC. The thermistor proximal to the balloon then recorded the temperature change in the pulmonary artery, and a temperature time curve was displayed. The average of at least three curves was then obtained.
• Modern catheters provide a semicontinuous method in which a thermal filament is mounted on the PAC 14 to 25 cm from the tip. The filament intermittently generates pulses of heat, and the temperature change is recorded by the thermistor in the pulmonary artery. These pulses of heat are pseudorandom to minimize the influence of other sources of temperature change such as infusions or respiratory fluctuations. The cardiac output is updated every 30 to 60 seconds and is time-averaged over the previous 3 to 6 minutes.
Complications
• Placement:
• Presence of the catheter:
• Common:
• Rare:
• Pulmonary infarction due to catheter-related thromboembolism, obstruction of the pulmonary blood flow by the catheter tip, or prolonged inflation of the balloon. Usually without consequences.
• Pulmonary artery rupture occurs in less than 0.1% of cases, associated with a mortality of greater than 30%. Warning signs include hemoptysis, with shadowing on the chest radiograph. Diagnosis is confirmed by pulmonary angiography. Treatment consists of embolization or thoracotomy. Factors increasing the risk of rupture include pulmonary hypertension, advanced age, hypothermia, coagulation disorders, and distal positioning of the catheter.
Outcomes and Evidence
• Benefits of bedside pulmonary artery catheterization remain controversial, and insertion of a PAC cannot, per se, improve patient survival.
Swan H, Ganz W, Forrester J, et al. Catheterisation of the heart in man with use of a flow-directed balloon tipped catheter. N Engl J Med. 1970;283:447-451.
Harvey S, Harrison DA, Singer M, et al. Assessment of the clinical effectiveness of pulmonary artery catheters in management of patients in intensive care (PAC-Man): a randomised controlled trial. Lancet. 2005;366:472-477.
Shah MR, Hasselblad V, Stevenson LW, et al. Impact of the pulmonary artery catheter in critically ill patients: meta-analysis of randomized clinical trials. JAMA. 2005;294:1664-1670.
Vincent JL, Pinsky MR, Sprung CL, et al. The pulmonary artery catheter: in medio virtus. Crit Care Med. 2008;36:3093-3096.
