Vascular Changes During Colorectal Surgery

The purpose of this study is to investigate whether increases in the blood flow from the heart (the cardiac output), induced by the administration of intravenous fluids, lead to an increase in the blood flow to the vital organs, in patients undergoing bowel surgery. This study will involve 2 phases. Firstly, potential volunteers will be invited to meet the research fellow (medical doctor) undertaking this study, who will check their suitability to participate in the study and who will obtain informed consent. The second phase is the study itself which will take place whilst volunteers are having their bowel operation. They will attend theatre in the normal way, but once they have been anaesthetised (put to sleep), a special monitor called an oesophageal doppler probe will be placed into their oesophagus (food pipe) via the nose. This monitor is frequently used in bowel surgery to help assess how much intravenous fluid to administer to a patient by measuring the cardiac output (the amount of blood pumped out of the heart each minute). Using the cannula (drip) already inserted in the arm to allow administration of the anaesthetic, a special fluid, called an ultrasound contrast agent, will be injected into the drip, to allow a contrast enhanced ultrasound scan of the abdominal organs to be performed, to measure the blood flow to these organs. A small sample of blood will be taken from the earlobe to allow us to measure a chemical in the blood called lactate. After this, intravenous fluid will be administered in order to increase the amount of blood pumped out of the heart. Once the oesophageal doppler monitor suggests that an adequate amount of fluid has been given, a second ultrasound scan will be performed to measure whether blood flow to the abdominal organs has also increased. A further blood sample will be taken from your earlobe to measure any change in lactate level. At the completion of the operation, a third ultrasound scan will be performed and another sa