PAC-Man: Is the Game Over in the ICU?
Abstract & Commentary
By Uday Nanavaty, MD, Assistant Director, AICU, St Agnes Hospital, Baltimore MD, is Associate Editor for Critical Care Alert.
Pulmonary and Critical Care Medicine, Rockville, Md
Dr. Nanavaty reports no financial relationship to this field of study.
Synopsis: In a randomized controlled trial, pulmonary artery catheter (PAC)-guided management did not improve outcomes (including ICU or hospital length of stay or mortality), but insertion of a PAC was associated with significant number of complications.
Source: Harvey S, 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.
Critically ill patients with the acute respiratory distress syndrome (ARDS) and/or multi-organ failure pose a challenge in maintaining effective circulatory function while avoiding volume overload. The management of these patients requires careful assessment of intravascular volume and cardiac output, and also that interventions performed to optimize one function do not result in deterioration of another parameter. Pulmonary artery catheters (PACs) have been used for more than 30 years in the management of such patients.
To assess the effectiveness and possible adverse effects of the PAC, the authors of this study (the PAC-Man study) performed a randomized, controlled trial in critically ill patients whose physicians felt that they should be managed with a PAC. Excluded were patients who were younger than 16 years of age, those who were admitted to the ICU for preoperative optimization, those who already had a PAC at the time of ICU admission, and organ donors in whom a PAC was being used for hemodynamic optimization prior to harvest. No protocol was established for hemodynamic optimization using the PAC. In the control group, non-invasive evaluation of cardiac output was allowed at the discretion of the clinician.
Out of 1263 eligible patients, 1041 were randomized. After excluding a further 23 patients for a variety of reasons, Harvey et al included 1014 patients in the analysis—506 assigned to the PAC group and 508 to a no-PAC (control) group. On average, it took 1.7 hours from randomization to PAC insertion. In the majority of the patients (81%), a PAC was recommended to aid the administration of vasoactive or inotropic medications.
The first 24-hour APACHE II acute physiology score (17.3 vs 18.0) and total score (22.1 vs 22.7) were comparable between the 2 groups. The hospital mortality was 68% in PAC group, which was not different from that in the control group (66%, adjusted hazard ratio, 1.09; 95% CI, 0.94-1.27; P = 0.25). ICU mortality (60% vs 57%) and 28-day mortality (62% vs 60%) were also not different between the 2 groups. The insertion of a PAC was associated with one or more complications in 46 of the 486 patients in whom PAC insertion was attempted. None of these complications were fatal. PAC insertion was associated with one or more changes in therapy within 2 hours of insertion in 389 (80%) patients in the PAC group. These changes included fluid challenges in 205 (42%) patients, a 25% or more change in the dose of vasoactive drug in 211 (43%) patients, and the introduction of vasoactive drug(s) in 156 (32%) patients.
Commentary
In general, monitoring devices are used to provide reliable measurements of physiological variables at some predetermined frequency. The principle of monitoring is based on the premise that the device will give information on a modifiable parameter in such a way that the outcome of a disease state can be changed. The monitoring device should not by itself impose significant risk to the patient. PAC provides information on hemodynamic parameters including central venous pressure and cardiac output as well as left ventricular filling pressures. The information is reliable and to a certain extent reproducible. There have been questions about safety of the device. Multiple complications have been described both during the time of insertion and during the prolonged use of a PAC. However, the biggest problem with the PAC has been a lack of consensus as to what should be done with the information.
Ever since the PAC became a norm in the ICU, there has been a quest to set goals of therapy. From achieving "normal" hemodynamics to aiming for "super-normal" values, studies have been done in attempts to show effectiveness of different strategies. No such study has shown clear superiority over an alternative strategy and questions have been raised about harmful effects, either related to the catheter itself or to the (mis)guided treatment resulting from its use. Especially in United States, clinicians tend to want to do "everything" to save a patient’s life. However, study after study has suggested that more care does not necessarily equate to better care, or better outcomes. A recent study in patients with heart failure, a setting in which the PAC may be the most logical tool to guide therapy, has also failed to show any benefit of using this device.1
The PAC-Man study could have been the final nail in the coffin of the PAC, but unfortunately, the investigators did not use any protocol nor did they have any established goals of therapy. Despite the increasing number of studies showing no benefit from the PAC, it is likely that more will be done, as some researchers remain convinced that there are patients whose outcomes will be improved through the use of this device.
Reference
- Binanay C, et al. Evaluation study of congestive heart failure and pulmonary artery catheterization effectiveness: the ESCAPE trial. JAMA. 2005;294:1625-1633.
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