Connors AF, Speroff T, Dawson NV, Thomas C, Harrell FE, Wagner D, et al. The effectiveness of right heart catheterization in the initial care of critically ill patients. SUPPORT Investigators. JAMA. 1996 Sep 18;276(11):889–97.
Introduction
The utility of the pulmonary artery catheter in critically ill patients has been shrouded in controversy ever since its introduction to clinical practice nearly half a century ago. Perhaps no other monitoring device has aroused as much fervor, passion, and polarization of opinion among critical care physicians over the years. The device was introduced into practice without clinical validation and gained widespread favor and acceptance among clinicians of the time. However, questions were soon raised regarding its safety and impact on clinical outcomes. An observational study nearly two decades later spurred intense interest among professional bodies and the lay press regarding the safety of the pulmonary artery catheter (1). This study proved to be a turning point and triggered controlled trials that evaluated the role of the pulmonary artery catheter in the management of critically ill patients.
Early history
Werner Forssmann (Fig. 1) was a pioneer in the field of cardiac catheterization. In 1929, experimenting upon himself, he passed a ureteric catheter through his elbow vein into the heart, thus performing the first cardiac catheterization in history (2). It was soon realized that the pulmonary capillary pressure closely matched the left atrial pressure, thus opening a window for the assessment of left heart function. Forssmann, along with two of his colleagues, were awarded the Nobel Prize in medicine in 1956 for their trailblazing work on pulmonary artery catheterization.
By the 1960s, pulmonary artery catheterization was firmly established as an important tool in hemodynamic assessment. However, the procedure was cumbersome, time-consuming, and required dexterity to navigate the catheter through to the pulmonary artery, often requiring fluoroscopic guidance in a catheterization laboratory.
The birth of the balloon-tipped catheter
On a bright afternoon in the autumn of 1967, just days after a particularly difficult cardiac catheterization, Jeremy Swan (Fig. 2) stood on a beach in Santa Monica, California, watching sailboats pass by (3). In an inspirational moment, it dawned upon him that he could make a catheter sail through the right heart into the pulmonary artery along the direction of blood flow. It occurred to him that a sail or a parachute at the tip of a highly flexible catheter could help pass a flow-directed device into the pulmonary artery. Teaming up with his colleague, William Ganz (Fig. 2), they refined the concept and contrived the balloon-tipped pulmonary artery catheter, creating a device that would soon become a milestone in the history of medicine. Their original version was a double lumen catheter with a “minor” lumen leading to the inflatable balloon at the tip (Fig. 3).
Three years later, the duo reported their initial experience in 100 patients with their eponymous balloon-tipped catheter (4). They inserted the catheter through the basilic vein. The wedge position could be attained in 95 patients and the pressure was accurately recorded in 72. Right heart catheterization would typically take around 20–30 minutes under fluoroscopy with the conventional approach; however, with the new device, it took an average duration of just 35 seconds to manipulate the catheter from the right atrium to the pulmonary artery.
The shadow of doubt over safety
Over the years, the PAC began to be extensively used in the operating rooms and ICUs. However, the initial enthusiasm was tempered by reports of errors associated with its use compared to the benchmark Fick technique of measurement of cardiac output (5,6). Although no controlled trial had evaluated its impact on clinical outcomes, clinicians persisted with therapeutic interventions tailored to hemodynamic variables obtained from the pulmonary artery catheter. Community hospitals in the US even insisted on skill with the use of the pulmonary artery catheter as a pre-requisite for physicians and nurses seeking critical care placement (7). By the mid 1980s, nearly 43% of critically ill patients underwent pulmonary artery catheterization for assessment of hemodynamic status; however, no tangible outcome benefits were observed during the same period (8). On the contrary, mortality rates were similar or even higher and the duration of hospital stay longer in patients who underwent pulmonary artery catheterization (8). Furthermore, catheter-related complications also began to surface, including thrombosis of the internal jugular vein and the pulmonary artery, pulmonary artery rupture, pulmonary hemorrhage, infective endocarditis, knotting of the catheter, and occasionally, fatal arrhythmias (5,6).
In his 1985 editorial, Eugene Robin of the Stanford School of Medicine alluded to the reservations he had with the seemingly irrational overuse of the pulmonary artery catheter (9). The catheter may help distinguish between cardiogenic and non-cardiogenic pulmonary edema; however, the question remained if management based on this knowledge led to improved outcomes. Similarly, although the catheter was often used to titrate afterload reduction in cardiac failure, it remained to be seen if this intervention had any impact on survival. The pulmonary artery catheter appeared to be employed as a “last rite” in patients who had little hope of survival. Adding to the complicity was the financial incentive, running into hundreds of dollars (a sizable amount in the 1980s) that may have biased clinicians in favor of using the catheter. Despite unsubstantiated benefit, rampant use of the pulmonary artery catheter continued over the next decade.
The landmark study
Against this background, Connors et al. designed a prospective cohort study to evaluate the association between pulmonary artery catheter use and clinical outcomes among patients admitted to the ICU (1). This study was performed largely because a randomized controlled trial seemed unrealistic in that era, considering the unmitigated conviction that clinicians seemed to have on the efficacy of the pulmonary artery catheter. This was exemplified by a previous attempt at a randomized controlled trial (RCT) in Ontario (10). Among 148 eligible patients, the investigators could include just 33 patients; 52 patients were excluded because clinicians had such a deep-rooted faith in the catheter that they considered it unethical not to use it!
The SUPPORT study evaluated 5735 patients who were admitted to the ICU of five hospitals in the US; of these, 2184 patients underwent pulmonary artery catheterization within the first 24 hours of ICU admission. On unadjusted analysis, pulmonary artery catheterization was associated with significantly higher 30-, 60-, and 180-day mortality. The duration of stay in the ICU and hospital was also longer in patients who underwent pulmonary artery catheterization.
Using multivariable logistic regression analysis, the authors assigned a propensity score to each patient based on parameters that would significantly contribute to the insertion of a pulmonary artery catheter. Among the 2184 patients who underwent PAC insertion, a matching patient in the same disease category and the closest propensity score was identified from the remaining 3551 patients who did not undergo PAC.
On propensity matching, there were 1008 matched pairs of patients who were managed with and without a PAC. The demographic and physiological characteristics of patients who underwent pulmonary artery catheterization were similar to propensity-matched patients who did not. For matched pairs of patients, mortality was consistently higher with pulmonary artery catheter use at 30, 60, and 180 days. Furthermore, on each of the 30 days after study entry, mortality was higher among patients who were managed with pulmonary artery catheter compared with those who did not undergo pulmonary artery catheterization. The cost of care was higher, the duration of ICU stay longer, and the intensity of care higher in patients who underwent pulmonary artery catheterization compared to those who did not.
On analysis by disease category, the relative hazard for mortality was significantly higher among patients with acute respiratory failure and multiorgan failure who underwent pulmonary artery catheterization. On pre-specified subgroup analysis, the hazard of death by 30 days was higher in women, the elderly, Caucasians, patients with shock or sepsis, and postoperative patients. The pulmonary artery catheter was associated with the worst outcomes in postoperative patients and those who were less severely ill.
The authors hypothesized four likely mechanisms that may have led to the adverse outcomes associated with pulmonary artery catheterization. First, complications of the catheter itself may have led to worse outcomes. Second, the use of the pulmonary artery catheter may be associated with a generally aggressive line of management, with likely worse outcomes. Third, pulmonary artery catheter-guided treatment, including targeting “supranormal oxygen delivery” that was often practiced during the study period, may have caused the excessive mortality. The fourth possibility may have been a likely beneficial effect from pulmonary artery catheterization being masked by confounding variables that were unaccounted for.
The study was limited by its observational design, and the likelihood of confounding variables that may have led to bias. It was confined to five hospitals and lacked generalizability to other settings. The study evaluated PAC use within the first 24 hours of ICU admission; hence, the possibility of a beneficial effect with later use could not be excluded.
This study strongly suggested that pulmonary artery catheter use may not be useful and could lead to possible harm among critically ill patients. The authors suggested performing an RCT considering the possible adverse outcomes that they demonstrated in their observational study. In an accompanying editorial Dalen and Bone suggested that the National Heart, Lung, and Blood Institute conduct an RCT to evaluate the safety and efficacy of the pulmonary artery catheter, or, if this was considered unfeasible, they recommended that the FDA must issue a moratorium on its use.
Later randomized controlled trials
In the face of this conundrum, considering the potential harm from the use of the pulmonary artery catheter, several RCTs were performed. Sandham et al. conducted an RCT comparing pulmonary artery catheter-guided goal-directed therapy with standard care among patients ≥60 years of age, undergoing major elective or emergency surgery. Patients were in the American Society of Anesthesiologists (ASA) class III or IV risk category and required postoperative care in the ICU. A total of 1994 patients were included, 997 in each group. The hospital mortality was similar among patients who underwent pulmonary artery catheter-guided treatment compared to those who received standard care (7.8% vs. 7.7%). Besides, there was no significant difference between the two groups in the 6-month or 1-year mortality. The median duration of hospital stay was 10 days in both groups of patients. The incidence of pulmonary embolism was significantly higher among patients who underwent pulmonary artery catheterization (11).
Richard et al. evaluated clinical outcomes with the early use of pulmonary artery catheter in patients with shock, mostly septic, acute respiratory distress syndrome (ARDS), or both (12). Patients were randomized to undergo pulmonary artery catheterization or management without the use of a catheter. There was no difference in mortality between the two groups at 14, 28, and 90 days. By day 14, The number of organ failure-free days, use of vasoactive agents, and renal replacement therapy were also similar both groups. The authors concluded that the use of a pulmonary artery catheter in patients with shock and ARDS did not reduce mortality or morbidity.
The PAC-Man RCT echoed these findings. Harvey et al. enrolled 1041 patients from 65 ICUs in the UK; 519 patients underwent management with a pulmonary artery catheter, and 522, without (13). The participating units reserved the option to use less invasive techniques of cardiac output measurement if considered appropriate. Clinical management was based on clinician judgment. There was no significant difference in hospital mortality between the two groups of patients (PAC vs. no PAC: 68% vs. 66%, p = 0.39). Besides, there was no difference in the ICU or hospital length of stay; no difference was observed in the requirement for organ support between groups. This study reinforced the lack of outcome benefit with PAC use in critically ill patients.
The iconic catheter fades away into history
As enthusiasm for the pulmonary artery catheter faded away with time, less invasive modalities of hemodynamic monitoring have come to the forefront in the management of critically ill patients. The pulmonary artery pressure may be indirectly measured with a fair degree of accuracy by interrogation of the tricuspid regurgitation jet using bedside transthoracic echocardiography. The stroke volume may also be calculated from the velocity-time integral of the left ventricular outflow tract and the aortic diameter. Transpulmonary thermodilution is far less invasive and has gained acceptance as a reasonable measure of cardiac output (14). Besides, this technique may also be used to assess the global end-diastolic volume and the intrathoracic blood volume as surrogate markers of the cardiac preload (14).
Pulse contour analysis is another monitoring technique that has shown promise in the bedside assessment of stroke volume. The contour of the arterial waveform is assumed to reflect the stroke volume and analyzed using an algorithm. Stroke volume measurement by pulse contour analysis is less invasive and shown to correlate with thermodilution-derived techniques of stroke volume measurement (15).
Summary
In its heyday, the balloon-tipped pulmonary artery catheter, devised by Jeremy Swan and William Ganz, was truly revolutionary and evolved into a quintessential monitoring modality in the ICU. It was introduced into clinical use in an era when controlled trials that establish efficacy of a novel intervention were not in widespread practice. Clinicians of that period readily embraced a handy bedside tool that appeared to provide answers to vexing questions during the course of the management of critically ill patients. Despite emerging evidence to the contrary, many continued to believe that the pulmonary artery catheter is an important tool in their hands and the seeming lack of benefit may be attributable to the poor understanding or misinterpretation of data by less endowed clinicians. However, the landmark observational study by Connors et al. triggered a detailed investigation into the safety and efficacy of the pulmonary artery catheter. None of the well-conducted RCTs that followed could demonstrate favorable clinical outcomes with its use. The once iconic, 1.1-meter-long catheter may well be on the verge of consignment to the rubbish heap of history apart from its continued use by a handful of diehard devotees.
References
1. Connors AF, Speroff T, Dawson NV, Thomas C, Harrell FE, Wagner D, et al. The effectiveness of right heart catheterization in the initial care of critically ill patients. SUPPORT Investigators. JAMA. 1996 Sep 18;276(11):889–97.
2. Bourassa MG. The history of cardiac catheterization. Can J Cardiol. 2005 Oct;21(12):1011–4.
3. Swan HJ, Ganz W. Hemodynamic monitoring: a personal and historical perspective. Can Med Assoc J. 1979 Oct 6;121(7):868–71.
4. Swan HJ, Ganz W, Forrester J, Marcus H, Diamond G, Chonette D. Catheterization of the heart in man with use of a flow-directed balloon-tipped catheter. N Engl J Med. 1970 Aug 27;283(9):447–51.
5. Chastre J, Cornud F, Bouchama A, Viau F, Benacerraf R, Gibert C. Thrombosis as a complication of pulmonary-artery catheterization via the internal jugular vein: prospective evaluation by phlebography. N Engl J Med. 1982 Feb 4;306(5):278–81.
6. Rowley KM, Clubb KS, Smith GJ, Cabin HS. Right-sided infective endocarditis as a consequence of flow-directed pulmonary-artery catheterization. A clinicopathological study of 55 autopsied patients. N Engl J Med. 1984 Nov 1;311(18):1152–6.
7. Dalen JE, Bone RC. Is it time to pull the pulmonary artery catheter? JAMA. 1996 Sep 18;276(11):916–8.
8. Gore JM, Goldberg RJ, Spodick DH, Alpert JS, Dalen JE. A community-wide assessment of the use of pulmonary artery catheters in patients with acute myocardial infarction. Chest. 1987 Oct;92(4):721–7.
9. Robin ED. The cult of the Swan-Ganz catheter. Overuse and abuse of pulmonary flow catheters. Ann Intern Med. 1985 Sep;103(3):445–9.
10. Guyatt G. A randomized control trial of right-heart catheterization in critically ill patients. Ontario Intensive Care Study Group. J Intensive Care Med. 1991;6(2):91–5.
11. Sandham JD, Hull RD, Brant RF, Knox L, Pineo GF, Doig CJ, et al. A randomized, controlled trial of the use of pulmonary-artery catheters in high-risk surgical patients. N Engl J Med. 2003 Jan 2;348(1):5–14.
12. Richard C, Warszawski J, Anguel N, Deye N, Combes A, Barnoud D, et al. Early use of the pulmonary artery catheter and outcomes in patients with shock and acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2003 Nov 26;290(20):2713–20.
13. Harvey S, Harrison DA, Singer M, Ashcroft J, Jones CM, Elbourne D, 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 Lond Engl. 2005 Aug 6;366(9484):472–7.
14. Schmidt S, Westhoff TH, Hofmann C, Schaefer JH, Zidek W, Compton F, et al. Effect of the venous catheter site on transpulmonary thermodilution measurement variables. Crit Care Med. 2007 Mar;35(3):783–6.
15. Chaney JC, Derdak S. Minimally invasive hemodynamic monitoring for the intensivist: current and emerging technology. Crit Care Med. 2002 Oct;30(10):2338–45.
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Excellent narrative ! Feels like a time travel for me along with the PAC.