May 2002
Dr Lau Chun Wing, Department of Medicine, Pamela Youde Nethersole Eastern Hospital
The pulmonary artery catheter (PAC) was introduced by Drs HJC Swan and W Ganz in 1970, with subsequent modifications. Despite its widespread use, its value in decreasing mortality in critically care patients is controversial. Some studies even reported higher mortality associated with its use. Numerous pitfalls exist regarding data acquisition of the primary variables like the pulmonary capillary wedge pressure and thermodilution cardiac output, including mechanical ventilation, respiratory excursions, West zones of catheter placement, hypovolaemia, high pressure surrounding the ventricles, left or right-sided valvular lesions, intracardiac or intrapleural shunts, etc. There are also errors in data interpretation, including inadequate knowledge on the complicated relationship between PCWP and compliance, volume status, and pulmonary edema. Difference in goal, choice and timing of therapy also affects the outcome. A local experience revealed that insertion of PAC was not a common event, and was limited to those patients with uncertain diagnosis or requiring diagnostic monitoring, and in those with complex haemodynamic profiles. Change of central venous pressure (CVP) over time was correlated with that in PCWP, but there was no correlation between the CVP and PCWP at specific points. Ethical problems in performing randomized clinical trials do not exist if there is clinical equipoise, i.e. < 70% experts would determine whether PAC is indicated or contraindicated for a certain clinical indication. There are at least five on-going prospective, randomized controlled trials on PAC use. Preliminary results show that although PAC does not confer extra benefits, it also does not increase mortality. Less invasive alternatives of haemodynamic monitoring are also being developed and validated.