Pulmonary Artery Catheters Unhelpful in Shock and ARDS
Abstract & Commentary
Synopsis: In this randomized, multicenter trial, early use of a pulmonary artery catheter in patients with shock, ARDS, or both did not significantly alter mortality or morbidity.
Source: Richard C, et al, for the French Pulmonary Artery Catheter Study Group. Early use of the pulmonary artery catheter and outcomes in patients with shock and acute respiratory distress syndrome. A randomized controlled trial. JAMA. 2003;290:2713-2720.
This study evaluated effects on outcomes of early use of a pulmonary artery catheter (PAC) in patients with shock, mainly of septic origin, the acute respiratory distress syndrome (ARDS), or both. Subjects were patients enrolled from 36 ICUs in France over a 30-month period (January 1999-June 2001) and randomly assigned to either receive a PAC (n = 355) or not (n = 341). Patients with shock for > 12 hours or ARDS for > 24 hours were excluded to avoid studying partly resolved shock or respiratory failure. Criteria for shock and ARDS were precisely defined. Treatment was at the discretion of individual physicians. However, participating physicians agreed on the following principles: optimization of circulating blood volume, vasoactive support if needed at a mean arterial pressure of at least 60 mm Hg when fluid balance was optimized, no objective of maximization of oxygen transport, free access to echocardiography, assist control ventilation with a maximum plateau pressure of 35 cm H2O and SpO2 of more than 90%, and prevention of thromboembolism with low-molecular-weight heparin, if not contradicted. The 2 groups were similar at baseline.
There were no significant differences in mortality with or without a PAC at day 14 (P = 0.70), day 28 (P = 0.67), or day 90 (P = 0.71). At day 14, the mean number of days of organ system failure with or without use of the PAC, renal support, and vasoactive agents did not differ. At day 28, mean days in the hospital with or without the PAC, in the ICU, or mechanical ventilation use also did not differ. Overall mortality at day 28 was 60.2%. On an intention-to-treat basis, this percentage did not differ significantly between the PAC and the control group at day 28 (199 [59.4%] vs 208 [61.0%] deaths). In one center, a significant difference in mortality in favor of the PAC was observed. After adjustment for severity of illness on admission (SAPS II), this difference was no longer significant. There were few complications: arrhythmias and conduction disturbances (n = 60), arterial puncture (n = 17), hemothorax (n = 1), and knotting of the catheter (n = 6). No pulmonary embolism or deep-venous thromboembolism was recorded.
Comment by Leslie A. Hoffman, PhD, RN
The major findings of this study were that patients randomized to early use of a PAC did not experience adverse events, nor did they derive any benefit. Accordingly, findings of this study differ from prior observational studies that raised doubts about the safety of PAC. The present study was unique in several ways. The population was restricted to patients with shock, ARDS, or both. Most (67%) were diagnosed with septic shock. Patients with shock for > 12 hours or ARDS for > 24 hours were excluded to avoid studying partly resolved shock or respiratory failure. General goals were established, but treatment was left to the discretion of each individual physician. This decision was made because adverse results were reported from prior studies that did not use a formal protocol and lack of consensus on how to best manage hemodynamic support in this population. This choice seems reasonable, especially in view of concerns voiced as a result of the ARDSnet investigators’ decision to select one treatment strategy. Protocol violations were infrequent. A PAC was inserted in 15 (4.4%) control patients, and 8 (2.4%) patients in the PAC group did not receive it because they died before insertion (n = 6) or placement was not possible (n = 2). Only 3 patients were lost to follow-up (1 PAC, 2 controls).
The major shortcoming of the study relates to its failure to meet recruitment goals. To avoid changes in practice that might influence study outcomes, the plan was to conclude the study after 18 months. Enrollment was slower than anticipated, and the study was extended to 30 months. Because enrollment continued to be slow, the study was closed 76 patients short of the enrollment goal. As such, the study was powered to detect a difference of 10%, but underpowered to detect a difference of 5%. Within these constraints, no difference was seen in mortality or morbidity.
As Richard and colleagues note, it would be unrealistic to believe that patient prognosis would be improved by use of a PAC alone. Any influence on prognosis would need to result from significant changes in treatment as a result of having the catheter. Of interest, physicians who managed both groups had access to free echocardiography. At least one examination was performed in 64% of the PAC group and 78% of the control group. In the latter group, echocardiography was used to assess ejection fraction and with Doppler analysis to evaluate cardiac output and estimate pulmonary artery pressure and left ventricular end-diastolic pressure. This noninvasive technology may provide benefits similar to those obtained with a PAC without its inherent risks.
Dr. Hoffman is Professor Medical-Surgical Nursing Chair, Department of Acute/Tertiary Care University of Pittsburgh School of Nursing