That no consensus exists is probably explained by the marked variability in both the reported risks and benefits of catheter usage.

On the basis of complication rates, there is evidence that the skills of those inserting and subsequently caring for the catheters vary widely. For example, it is easy to find series which report a five-fold variation in the pneumothorax rate following subclavian venepuncture while others describe a similar variation in the incidence of carotid puncture following internal jugular venepuncture.

Similarly, surveys of the knowledge of physicians and nurses who use PACs, suggest that interpretative skills also vary considerably. If one assumes that misinterpretation of data ultimately translates into a lesser benefit, it is hardly surprising that a consensus on use of the catheters is hard to find given the individual and 'institutional' variability which apparently exists on both the risk and benefit sides of the equation.

The need to resolve this question by means of randomised, controlled trials has been strongly advocated by the Pulmonary Artery Catheter Consensus Conference ². However, for reasons which have been elegantly addressed by Horan in his analysis of 'Evidence-Based Medicine and Anaesthesia' ⁵, it may be that this methodology will not provide the answer.

Two committees of review have chosen different approaches to evaluating the indications for pulmonary arterial catheterisation.

The American Society of Anesthesiologists Task Force ¹ recommended consideration of the "Procedure, Patient and Practice Setting" (Figure 1) when deciding whether or not to insert a PAC in a surgical patient. This approach is important because it reinforces the importance of practice setting in the safe-use of the PAC. - Whilst it might be quite reasonable to use a catheter in a patient with a leaking aortic aneurysm being treated in a university teaching hospital, this same patient might be better served by the non-use of a catheter if being treated in a district general hospital.

On the basis of this approach, an appropriate set of guidelines for the use of the PAC in the surgical patient might be:

Procedure:
Any procedure which is associated with acute, severe changes in preload, afterload or the contractile state - particularly where the changes are unpredictable. Examples of derangements in preload which might warrant PA catheterisation would include any procedure where blood loss may be massive, or where partial or complete caval occlusion might occur. Similarly, the changes in afterload which occur during high aortic cross-clamping constitutes a reasonable indication for the use of a PAC. Finally, the changes in contractile state and ventricular compliance which result from prolonged aortic cross-clamping during complex open-heart surgery are also an appropriate indication for PA catheterisation. (In this context, most cardiac anaesthetists would accept that uncomplicated coronary artery grafting, in an otherwise well patient, is not by itself an indication for a PAC.)

Such haemodynamic changes would most typically be seen in the areas of cardiac, vascular and hepatic surgery.

Patient:
Reasonable indications for the insertion of a PAC would include any patient with septicaemic shock or other significant cardiac, respiratory or renal disease.

Significant cardiac disease might reasonably be defined as: impaired left ventricular function (ejection fraction less than 0.30), unstable angina, severe aortic stenosis, or any cardiac condition which results in a marked reduction in exercise capacity **.

Significant pulmonary disease might reasonably be defined as: Any condition which results in hypoxia (PaO2 < 70 mm Hg), hypercarbia (PaCO2 > 45 mm Hg) or a marked reduction in exercise capacity **.

Significant renal disease might reasonably be defined as: Any patient with dialysis-dependent renal failure or any patient in whom plasma creatinine is more than ~ 0.25 mmol/L. - The progression from pre-renal insult to acute renal failure (ARF) in a patient with already impaired renal function carries with it a significant increase in mortality. For this reason, the practice of optimal volume loading ⁶ and 'goal-directed hemodynamic therapy' ⁷ under PAC control have been advocated as means of reducing the incidence of ARF in high-risk surgical patients .

The presence of multi-system disease is also an indication for the use of a PAC.

Practice setting:
It is most appropriate to use a PAC when the physician skills, level of technical support, training and experience of nursing staff and availability of specialists and equipment necessary to treat the abnormalities detected by the PAC are all of the highest order.

The document describing the practice guidelines is available on the world-wide web at: http://www.asahq.org/practice/pulm/pulm_artery.html..

An alternative form of analysis to the 'Procedure, Patient and Practice Setting' suggested by the American Society of Anesthesiologists Task Force was used by the Pulmonary Artery Catheter Consensus Conference ². This conference adopted a more didactic approach and considered the role of the PAC in a group of about twenty quite specific scenarios. They answered the question of whether or not a PAC should be used in the scenario under consideration on the basis of the quality of the evidence in support of employment (Table 1).

As a generalisation, the conference found that the use of a PAC was quite often justified by the evidence in the scenario under examination, but that the evidence for this support was typically of grade IV or V quality. The conference was also strongly of the opinion that randomised, controlled trials examining the use of the PAC were indicated in virtually all areas of practice where catheters were used.

Some of the important conclusions of this conference were that:

1. Management with a PAC did improve outcome in patients with myocardial infarction complicated by progressive hypotension or cardiogenic shock.

2. Management with a PAC did not reduce perioperative complications and mortality in patients undergoing cardiac surgery.

3. PAC guided therapy altered both diagnosis and therapy in patients in respiratory failure, but that the effect on outcome was uncertain.

4. PAC guided therapy altered diagnosis and improved functional outcome in the traumatically injured patient, but that the effect on mortality was uncertain.

5. It was uncertain if PAC guided therapy improved outcome in patients with septicaemic shock.

Indications for a PAC in the patient with myocardial infarction:
The Catheter Consensus Conference concluded that the use of a PAC in the patient with myocardial infarction was justified if infarction was complicated by cardiogenic shock, right ventricular infarction or a mechanical complication such as ventricular septal defect or papillary muscle rupture. However, in all these scenarios, the conclusion was only supported by level IV or V evidence.

If myocardial infarction is complicated by refractory cardiac failure alone, the role of the PAC is contentious. The American College of Cardiology / American Heart Association Task Force ³ recommended the use of a PAC, whereas in a large study by Connors, PAC monitoring was found to be of no benefit ⁸.

Indications for a PAC in the cardiac surgical patient:
In many centres, the decision to use a PAC is dictated by local convention. In the case of routine coronary artery bypass grafting, two large series ^{9, 10} have failed to demonstrate any benefit from the use of a PAC and the view of the Catheter Consensus Conference was that PAC use was not justified in low-risk patients. This opinion has been confirmed in recent studies by Stewart et al ¹¹ and Ramsey et al ¹⁷.

Although there are no data to support the view, the indications for insertion of a PAC in a patient undergoing routine coronary artery bypass grafting appear to us to be strengthened if 'Off-Pump' surgery is to be performed. In such cases, the utility of ECG and / or echocardiographic monitoring can be greatly reduced during the manipulation of the heart while the measurements available from a PAC are largely unaffected.

The situation with high-risk patients is less clear. Many cardiac anaesthetists would agree that the presence of severe ventricular dysfunction, pulmonary hypertension or valvular dysfunction are reasonable indications for the insertion of a PAC although there is little evidence to support this view. Certainly, if the use of specific pulmonary vasodilator therapy is envisaged, it is difficult to imagine the monitoring of such therapy without the use of pulmonary arterial catheterisation.

Indications for a PAC in the patient with respiratory failure:
The Catheter Consensus Conference concluded that the use of a PAC in the patient with respiratory failure altered the diagnosis in a significant proportion of patients, but that it was uncertain if catheter use improved outcome.

In the presence of both respiratory and cardiac disease, arterial PO2 is the result of a complex interaction between cardiovascular, metabolic and respiratory factors. It is only through the use of a PAC that the precise contribution of each factor can be assessed and it is for this reason that diagnostic accuracy is improved when the catheters are used.

The nature of this interaction can be appreciated by experimenting with alteration of one or other of the variables on the 'Calculators' page of the simulator. Refer to the section on Simulation Exercises for further details.

If extreme pulmonary hypertension complicates acute respiratory failure, the PAC has an obvious role in the assessment of pulmonary vascular reserve and the response to vasoactive drugs such as epoprostenol (prostacyclin) ¹².

Indications for a PAC in the trauma patient:
The particular role of pulmonary artery catheters in trauma patients has been examined in a meta-analysis of published studies by Kirton and Civetta ¹³. These authors concluded that there was insufficient evidence to support a definite survival benefit arising from the use of the catheters, but that a reduction in morbidity or improvement in functional outcome was suggested in some cases. They concluded that the use of the PAC was appropriate if used:

a) to direct therapy when noninvasive monitoring was inadequate, misleading, or the endpoints of resuscitation were difficult to define;

b) to potentially decrease secondary injury when severe closed-head or acute spinal cord injuries were components of multisystem trauma;

c) to augment clinical decision-making when major trauma was complicated by severe adult respiratory distress syndrome, progressive oliguria/anuria, myocardial ischaemia, congestive heart failure, or major thermal injury; or

d) to establish the futility of care.

Indications for a PAC in patients with septicaemic shock:
PACs are widely used in the management of patients with septicaemic shock. There appears to be little doubt that catheter use improves diagnostic accuracy ¹⁴ and changes management strategies ¹⁵, but, as with other clinical settings, the effect on outcome remains unclear ⁸.

Other indications for a PAC:
A therapeutic (rather than diagnostic) role for the catheters has emerged with the development of special function pacemaking catheters which enable the clinician to provide emergency ventricular or atrioventricular pacing without the requirement for image intensification.

More recently, a PAC has been used for the temporary closure of a post-infarction ventricular septal defect (VSD) using a femoral transvenous approach. This resulted in substantial improvement in the haemodynamic status of the patient. Subsequently, the patient underwent surgery for VSD closure ¹⁶.

Impending trials:
At least two, large, randomised controlled trials intended to evaluate the role of the PAC in critically ill patients are currently in progress ^{18, 19}. With regard to the UK trial, Angus and Black have noted that "British intensive care units have huge variations in pulmonary artery catheter use, with insertion rates varying from 3% to 76% of admissions. If the pulmonary artery catheter does indeed influence mortality, the number of lives lost or saved due either to inappropriate use or to lack of use could be staggering." ¹⁸

It is to be hoped that such trials do indeed "bring crucial evidence to bear on a problem that has been debated worldwide for decades."

Footnote ** 1. The inability to climb two flights of stairs without stopping.

1. Roizen MF, Berger DL, Gabel RA et al Practice Guidelines for pulmonary artery catheterization. A report by the American Society of Anesthesiologists task force on pulmonary artery catheterization. Anesthesiology 78:380-394, 1993

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

3. Ryan TJ, Anderson JL, Antman EM et al ACC/AHA guidelines for the management of patients with acute myocardial infarction. A report of the American College of Cardiology.

4. Sackett DL, Rosenberg WMC, Muir Gray JA et al Evidence based medicine: What it is and what it isn't.Br Med J 1996; 312: 71-72

5. Horan BF Evidence-based medicine and anaesthesia: Uneasy bedfellows? Anaesth Intens Care 1997; 25: 679 - 685

6. Bush HL Jr, Huse JB, Johnson WC, O'Hara ET, Nabseth DC Prevention of renal insufficiency after abdominal aortic aneurysm resection by optimal volume loading. Arch Surg 116:1517-1524, 1981.

7. 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.

8. 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

9. 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.

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

11. Stewart RD, Psyhojos T, Lahey SJ et al Central venous catheter use in low-risk coronary artery bypass grafting. Ann Thorac Surg 1998 Oct;66(4):1306-11

12. Barst RJ; Rubin LJ; Long WA; et al A comparison of continuous intravenous epoprostenol (prostacyclin) with conventional therapy for primary pulmonary hypertension. The Primary Pulmonary Hypertension Study Group. N Engl J Med, 334:296-302, 1996

13. Kirton OC, Civetta JM Do pulmonary artery catheters alter outcome in trauma patients? New Horiz, 5:222-7, 1997 Aug

14. 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

15. Steingrub JS; Celoria G; Vickers-Lahti M; Teres D; Bria W Therapeutic impact of pulmonary artery catheterization in a medical surgical ICU. Chest, 99:1451-5, 1991 Jun

16. Abhyankar AD, Jagtap PM Post-infarction ventricular septal defect: percutaneous transvenous temporary closure using a Swan-Ganz catheter. Catheter Cardiovasc Interv 1999 Jun;47(2):208-10

17. Ramsey SD, Saint S, Sullivan SD, Dey L, Kelley K, Bowdle A Clinical and economic effects of pulmonary artery catheterization in nonemergent coronary artery bypass graft surgery. J Cardiothorac Vasc Anesth 2000 Apr;14(2):113-8.

18. Angus D, Black N. Wider lessons of the pulmonary artery catheter trial : Intensivists are rising to the challenge of evaluating established practices. BMJ 2001; 322:446.

19. Shah MR, O'Connor CM, Sopko G, Hasselblad V, Califf RM, Stevenson LW. Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness (ESCAPE): design and rationale. Am Heart J. 2001 Apr;141(4):528-35.

Last edited on: 23/12/2001