The cardiovascular effects of crystalloid administration in endoscopy patients

Intravenous fluids are commonly administered for patients having colonoscopy despite relatively little data to support this practice. It is unclear what, if any, effect crystalloid administration has on stroke volume and cardiac output in patients who are fasting and have had bowel preparation agents. We aimed to assess the physiological effect of 10 ml/kg of crystalloid administration in colonoscopy patients on haemodynamic parameters including stroke volume, stroke volume variation and cardiac output, as measured with transthoracic echocardiography. Our secondary aims were to determine whether stroke volume variation predicted fluid responsiveness in gastrointestinal endoscopy patients and whether these haemodynamic measures are different in fasting patients with bowel preparation (colonoscopy patients) compared to fasting patients alone (gastroscopy patients). We recruited 54 patients having elective gastrointestinal endoscopy (25 colonoscopy, 29 gastroscopy). All patients had stroke volume, cardiac output and stroke volume variation measured with transthoracic echocardiography at baseline. In colonoscopy patients, stroke volume, cardiac output and stroke volume variation were remeasured after 10 ml/kg of intravenous crystalloid. Administration of 10 ml/kg of crystalloid increases stroke volume by 19.6 ml ( p < 0.00005) and cardiac output by 0.81 l/min ( p < 0.001). Stroke volume variation reduced from 23% to 14% after fluid administration ( p < 0.0011). The optimum threshold of stroke volume variation to predict fluid responsiveness was 21% with a sensitivity of 77.8% and specificity of 62.5%. Administration of 10 ml/kg of crystalloid increases stroke volume and cardiac output, and reduces stroke volume variation in fasting elective colonoscopy patients.