A study to compare 2 methods of inserting a pulmonary artery catheter in high risk cardiac surgical patients.

The pulmonary artery catheter (PAC), also known as Swan-Ganz catheter, is a catheter that is inserted into the heart through a large vein in the neck or groin. It is used routinely in all patients undergoing cardiac surgery at Austin Hospital and allows direct, simultaneous measurement of pressures in the right atrium and right ventricle of the heart and pulmonary artery. In addition, it allows the calculation of important cardiac and respiratory physiological information. The PAC is also used to evaluate the effects of drugs on the cardiovascular system, assess and optimise fluid requirements, and manage complications of cardiac surgery such as myocardial infarction and heart failure. Complications from PAC insertion, although infrequent can be harmful. Mal-positioning can lead to arrhythmias, trauma to the pulmonary artery causing bleeding or thrombosis (clotting), infection and pneumothorax (puntured lung). The “standard” anaesthetic technique used to insert the PAC involves slow advancement of the catheter through the heart chambers. The catheter cannot be visualised as it is inserted, however as the catheter traverses the chambers of the heart (right atrium, right ventricle, and pulmonary artery), a characteristic change in cardiac pressure waveforms is seen in each chamber. This change in waveform allows the clinician to advance the catheter through the heart chambers until is its final positioning in the pulmonary artery. Because the catheter is inserted “blindly”, malposition of the catheter commonly occurs. Prolonged and repeated attempts at placing the PAC increase the risks of complications, particularly arrythmias (irregular heart beats), coiling and incorrect position. A technique commonly used by radiologists to guide catheter placement is the use of an X-ray image intensifier, or video flouroscopy. This allows the catheter to be visualised as it is being inserted through the heart chambers into its final position in the pulmonary artery. This technique is also commonly employed by anaesthetists to insert the PAC if it insertion by the standard "blind" method fails. The use of this technique to insert the PAC has never been studied any any scientific way, therefore we propose to study this X-ray technique on patients who are at increased risk from having a complication from PAC insertion. High-risk patients will include those with poor heart function, high pre-existing pulmonary artery pressures, or severe valvular heart disease. The use of the X-ray image intensifier involves X-ray exposure to the patient, but studies have shown that the risk is very minimal. We hypothesize that the use of the X-ray image intensifier to guide positioning of the PAC in high-risk patients undergoing cardiac surgery results in a shorter insertion time, with fewer attempts at insertion, and precise final positioning of the catheter in the pulmonary artery when compared to standard "blind" insertion. Primary end point: time taken in seconds to insert the PAC and final positioning of the PAC. Secondary end points: number of attempts at insertion and complications from insertion Final correct PAC positioning will be checked in theatre by trans-oesophageal echocardiography.