The increasing focus of health administrators on the cost of delivery of health care has prompted vigorous discussion on the usefulness (or otherwise) of PAC monitoring in critically-ill patients. ^{1, 2, 3} Interested readers are referred to original research ^{4, 5}, editorial opinion ^{6, 7} , debate ^{8 , 9 , 10 , 11 , 12 , 13} and meta-analysis ¹⁴ for current views.

When assessing the possible benefits of the PAC, three distinct hypotheses have been examined by investigators.

1. That PAC monitoring might enable diagnosis of clinically undetectable but serious haemodynamic abnormalities.

2. That the availability of PAC data might alter the subsequent management of the patient.

3. That, as a result of improved diagnosis and alterations in management, patient outcome might be improved.

Each of these proposals will now be considered in some detail.

That PAC monitoring might enable diagnosis of clinically undetectable but serious haemodynamic abnormalities:
Both in the operating theatre and the ICU, it is probably true that experienced clinicians are often unable to correctly identify serious haemodynamic abnormalities without the use of PACs.

For example, in a group of patients without signs of serious cardiac dysfunction who were scheduled to undergo major surgery, it was found that nearly two thirds of those cleared for surgery had abnormally high wedge pressures or other evidence of serious cardiovascular derangement when PACs were inserted preoperatively ¹⁵. This inability to detect serious cardiovascular abnormalities by clinical means alone has also been demonstrated in other groups of patients scheduled to undergo major surgery ¹⁶ and in critically ill patients in the ICU ¹⁷.

In contrast there are no studies to support the view that the experienced clinician is more accurate than a PAC in the diagnosis of major haemodynamic abnormalities.

That the availability of PAC data might alter the subsequent management of the patient:
There are several studies which support the view that once PAC data are available, therapeutic strategies are altered.

In an ICU population, it has been reported that PAC data alters the diagnosis in one third of patients and the medical management in nearly two thirds ¹⁸. A similar impact on diagnosis and management has been found when PACs are used in patients scheduled for major vascular surgery ¹⁹.

Notwithstanding the evidence that the availability of PAC data does tend to alter management, it is also true that clinicians do not always use the data appropriately when it is available to them.

What is much less clear, is whether the earlier diagnosis and more appropriate intervention which the PAC monitoring facilitates, does, in fact, lead to a better outcome.

A widely-quoted study by Rao ²⁰ of a group of patients with coronary artery disease who were scheduled for non-coronary surgery apparently demonstrated that the use of PACs combined with aggressive haemodynamic management was associated with a significant reduction in perioperative infarction and mortality rates. Similarly, in a small group of patients with left main trunk disease who were undergoing coronary artery bypass grafting, Moore found a significant reduction in mortality if a PAC was used ²¹. However, both these studies used historical controls, were not prospective and are therefore open to major criticism.

A recent study by Flancbaum ⁵ also demonstrated an improved perioperative outcome if haemodynamic abnormalities which had been detected by a PAC, were corrected prior to surgery, although again, the study was retro- rather than pro-spective. This study can be contrasted with that of Valentine et al ²² who were unable to demonstrate any benefit arising from the use of PACs or the practice of "Preoperative tune up" by "hemodynamic optimization" in a large group of patients scheduled for aortic surgery.

In fact, the use of historical controls, or the provision of a treatment arm which allowed for the subsequent use of a PAC in a patient had not been given this form of monitoring, flaws the design of many of the published outcome studies.

In two large series of patients undergoing coronary artery bypass grafting ^{23 , 24} researchers have been unable to demonstrate any reduction in morbidity or mortality in those who were monitored with central venous pressure measurements alone compared with those who received a PAC. However, as with the beneficial outcome studies quoted above, both series are open to methodological criticism.

In a recent, multi-centre study of PAC use in intensive care units, Connors et al ⁴ reported on the impact of the early use of the PAC in a group of 5735 patients. The use of a PAC was associated with an increased mortality and an increased duration of stay. It should be noted that this study was not randomised or controlled and that the patients who were initially monitored with a PAC were appreciably sicker than those who were not - as evidenced by significantly higher TISS and APACHE scores. To refute this argument, the authors examined the outcomes in a matched subset of 2016 of the patients and were still able to demonstrate an apparently adverse effect of the use of a PAC. - The risk of death within 30 days being increased by about 25% (odds ratio 1.24) in those monitored with a PAC.

Shoemaker et al introduced the concept of 'supranormal' therapy ²⁵. In a group of intensive care patients, PACs were used to guide therapy so that supranormal values of cardiac index and oxygen delivery were achieved ²⁶. Under these circumstances, mortality, duration of ICU stay and cost of treatment of the 'supranormal' group were all significantly reduced. This observation has been confirmed by Fleming et al ²⁷, but has been refuted by others ^{28, 29}.

This view is not shared by the members of the Pulmonary Artery Catheter Consensus Conference ³⁰ who concluded that the existence of clinical equipoise regarding the use or non-use of PAC's was uncertain and that for this reason randomised, controlled trials (RCTs) examining the role of the PAC could be ethically conducted.

If such trials are conducted, extremely large numbers may be needed to demonstrate benefit. - In the case of coronary artery surgery, Spackman ³¹ has calculated that "If a death rate in the control group (CVP) of 3% is assumed, and a 0.2% reduction in the group monitored with PACs is anticipated, then the total sample size needed to show a significant difference (95%CI) with 80% power is 233,010".

An alternative approach to the conduct of large RCTs is the meta-analysis of existing, (smaller) RCTs. Ivanov et al ¹⁴ have recently analysed the outcomes of over 1600 patients who participated in such trials and have concluded that there is a statistically significant reduction in morbidity when PAC-guided strategies are used for the management of criticall-ill patients. In this analysis, the magnitude of the reduction in morbidity as a result of catheter use was about 20%. However, the same authors have also remarked on the shortcomings of the trials which were included in their meta-analysis ³².

1. Davies MJ, Cronin KD, and Domaingue CM Pulmonary artery catheterization: an assessment of risks and benefits in 220 surgical patients. Anaesth Intensive Care 10:9, 1982.

2. Hines RL Pulmonary artery catheters: what's the controversy? J Card Surg, 5:237-9, 1990 Sep

3. Del Guercio LRM Does pulmonary artery catheter use change outcome? Yes. Crit Care Clin, 12:553-7, 1996 Jul

4. Connors JF, Speroff T, Dawson NV et al The effectiveness of right heart catheterisation in the initial care of critically ill patients. JAMA: 1996; 276:889-897

5. Flancbaum L, Ziegler DW, Choban PS Preoperative intensive care unit admission and hemodynamic monitoring in patients scheduled for major elective noncardiac surgery: A retrospective review of 95 patients. J Cardiothorac Vasc Anesth 12:3-9, 1998

6. Soni N Swan song for the Swan-Ganz catheter? BMJ 1996;313:763-764

7. Leibowitz AB Perioperative pulmonary artery catheterization: What is the evidence that it improves outcome. J Cardiothorac Vasc Anesth 12:1-2, 1998

8. Garnett RL Pro: A Pulmonary Artery Catheter should be used in All Patients undergoing Abdominal Aortic Surgery. J Cardiothorac Vasc Anesth 1993, 7:750~752.

9. Ellis JE Con: Pulmonary Artery Catheters are not Routinely Indicated in Patients undergoing Elective Abdominal Aortic Reconstruction. J Cardiothorac Vasc Anesth 1993, 7:753-757.

10. Fink MP The flow-directed, pulmonary artery catheter and outcome in critically ill patients: have we heard the last word? Crit Care Med 1997 Jun;25(6):902-3

11. Pulmonary Artery Catheter Consensus conference: consensus statement. Crit Care Med 1997 Jun;25(6):910-25

12. Vender JS Resolved: A Pulmonary Artery Catheter Should Be Used in the Management of the Critically ill Patient. Pro J Cardiothorac Vasc Anesth 12:9-12, 1998

13. Becker K Resolved: A Pulmonary Artery Catheter Should Be Used in the Management of the Critically ill Patient. Pro J Cardiothorac Vasc Anesth 12:13-16, 1998

14. Ivanov R, Allen J, Calvin JE The incidence of major morbidity in critically ill patients managed with pulmonary artery catheters: a meta-analysis. Crit Care Med 2000 Mar;28(3):615

15. Del Guercio LRM, Cohn JD. Monitoring operative risk in the elderly. JAMA 243:1350, 1980.

16. Flancbaum L, Ziegler DW, Choban PS Preoperative intensive care unit admission and hemodynamic monitoring in patients scheduled for major elective noncardiac surgery: A retrospective review of 95 patients. J Cardiothorac Vasc Anesth 12:3-9, 1998

17. Staudinger T; Locker GJ; Laczika K et al Diagnostic validity of pulmonary artery catheterization for residents at an intensive care unit. J Trauma, 44(5):902-6 1998 May

18. Iberti TJ, Fischer CJ A prospective study on the use of the pulmonary artery catheter in a medical intensive care unit - its effect on diagnosis and therapy. Crit Care Med 10:A283, 1983

19. Babu SC, Sharma PVP, Raciti A et al: Monitor-guided responses - operability with safety is increased in patients with peripheral vascular disease. Arch Surg 115:1384, 1980

20. Rao TLK, Jacobs KH, and El-Etr AA Reinfarction following anesthesia in patients with myocardial infarction. Anesthesiology 59:499-505, 1983.

21. Moore CH, Lombardo TR, Allums JA, Gordon FT Left main coronary artery stenosis; Hemodynamic monitoring to reduce mortality. Ann Thorac Surg 26:445, 1978

22. Valentine RJ, Duke ML, Inman MH et al Effectiveness of pulmonary artery catheters in aortic surgery: a randomized trial. J Vasc Surg 1998 Feb;27(2):203-11

23. Tuman KJ, McCarthy RJ, Spiess BD, et al: Effect of pulmonary artery catheterization on outcome in patients undergoing coronary artery surgery. Anesthesiology 70:199-206, 1989.

24. Bashein G, Johnson PW, Davis KB, Ivey TD Elective coronary bypass surgery without pulmonary artery catheter monitoring. Anesthesiology 63:451, 1985

25. Shoemaker WC, Appel PL, Kram HB, Waxman K, Lee TS Prospective trial of supranormal values of survivors as therapeutic goals in high-risk surgical patients. Chest 94:1176-1186, 1988.

26. Shoemaker WC, Kram HB, Appel PL, et al: The efficacy of central venous and pulmonary artery catheters and therapy based upon them in reducing mortality and morbidity. Arch Surg 125:1332-1338, 1990

27. Fleming A, Bishop M, Shoemaker W. et al: Prospective trial of supranormal values as goals of resuscitation in severe trauma. Arch Surg 127:1175-1181, 1992

28. Hayes MA, Timmins AC, Yau EH, et al: Elevation of systemic oxygen delivery in the treatment of critically ill patients. N Engl J Med 330:1717-1722, 1994

29. Gattinoni L, Brazzi L, Pelosi P. et al: A trial of goal-oriented hemodynamic therapy in critically ill patients. N Engl J Med 333:10251036, 1995

30. Pulmonary Artery Catheter Consensus conference: consensus statement. Crit Care Med 1997 Jun;25(6):910-25

31. Spackman TN A theoretical evaluation of cost-effectiveness of pulmonary artery catheters in patients undergoing coronary artery surgery. J Cardiothorac Vasc Anesth 1994 Oct;8(5):570-6

32. Ivanov RI, Allen J, Sandham JD, Calvin JE Pulmonary artery catheterization: a narrative and systematic critique of randomized controlled trials and recommendations for the future. New Horiz 1997 Aug;5(3):268-76

Last edited on: 14/11/2000