Guy A Richards
It should be remembered that hemodynamic monitoring is not itself diagnostic of an underlying disease process unless the patient is merely hypovolemic. The following discussion does not therefore consider what further might be wrong with this patient, but this obviously warrants further attention. It is, however, necessary to support the patient until the primary disease responds and invasive monitoring would be useful to guide the use of vasoactive agents and fluid replacement. Clinical parameters alone are relatively inaccurate with regard to hemodynamic status in critically ill patients [11
Parameters that are of particular value are cardiac output, pulmonary artery occlusion pressure, mixed venous oxygen saturation, right ventricular end diastolic volume, and systemic vascular resistance. Whereas some parameters may be obtainable with less invasive techniques, such as Doppler esophageal monitoring, only the PAC can easily and continuously or repetitively monitor them all. Despite these benefits, no agreement has been reached with regard to its potential to cause harm [12
]. There have even been calls for a moratorium on its use until the issue is settled [13
Most recent studies, although not showing benefit, have not shown an increase in mortality or morbidity [15
]; although some have found an increase in length of stay and costs. Those studies that do suggest an increased mortality have serious methodologic flaws such as small numbers of heterogeneous patient populations, inappropriate use of the PAC, insufficient evaluation of intensivist expertise and nonprotocol-driven therapeutic strategies in response to PAC data [17
The most important shortcoming of the PAC appears to be that the derived data is incorrectly measured, interpreted and utilized [19
]. In a recent study by Squara and colleagues, at least 35% of doctors attending three critical care congresses suggested at least one potentially harmful intervention when assessing clinical data in a case study provided. Subsequent to insertion of a PAC, the range of treatments and the number of harmful interventions were reduced and there was improved agreement between participants and designated experts as to correct management [20
]. Nevertheless, the harmful interventions remained greater than 15% even without the participants themselves having to measure and record the PAC data. Ten percent of physicians still suggested harmful therapeutic strategies even after three PAC recordings were given, effectively increasing PAC-associated mortality by 30%. This study concurs that the PAC is more accurate than clinical assessment of hemodynamic status and that, when correctly utilized, diagnosis and management is improved. However, the persistent misutilization of data by a relatively small percentage of participants, and by extension a small percentage of study populations, will result in the misconception that the PAC has no effect on or actually increases mortality. Studies that examine homogeneous populations with protocol-driven responses are the only ones likely to show benefit.
In conclusion, in the present scenario a PAC inserted by an intensivist trained in its use and utilizing protocol-directed responses would not increase mortality and morbidity, and probably would improve outcome.