6 hour infusion of apelin peptide into circulation

Infusion of saline into systemic circulation

Cardiac index will be assess in patients through the 6hr infusion, using thoracic cardiac bioimpedance. Prior to starting the infusion there will be a 30 minute run in period to achieve a stable cardiac index. Thereafter the infusion will be started, with cardiac index assess every five minutes during the first hour. For each subsequent hour participants will be free to mobilise for the thirty minute periods, with cardiac index and systemic haemodynmics assess for the following thirty minutes.

Additionally during the first hour pulmonary artery pressure will be estimated from pulmonary artery pressures assessed with echocardiography. This will be assessed at baseline with four further measurements during the first hour of infusion.

Participants will be asked to void prior to the study starting, thereafter all urine will be collected during the course of the study. Relevant biochemical/humoral factors will be assessed in the urine.

We will assess, using thoracic bioimpedance cardiography, the change in cardiac output in response to apelin infusion

All urine will be collected during the studya and we will assess volume and relevant biochemical/humoral factors

Using echocardiography we will estimate the pulmaonary artery pressure from pulmonary velocity and assess any change during the first hour of study.