Fluid responsiveness and hypotension in patients undergoing propofol-based sedation for colonoscopy following bowel preparation: a prospective cohort study

Purpose Fasting and bowel preparation may deplete intravascular volume in patients undergoing colonoscopy. Nevertheless, rigorous demonstration of volume depletion and assessment of clinical consequences is lacking. We designed this study to explore the relationship between intravascular volume status and intraprocedural hypotension and to compare transthoracic echocardiography (TTE) and the ClearSight (TM) (Edwards Lifesciences, Irvine, CA, USA) noninvasive cardiac output monitor to measure intravascular volume status. Methods We recruited adult patients undergoing elective colonoscopy following bowel preparation at the Royal Melbourne Hospital. We assessed the volume status preprocedure by taking TTE and ClearSight measurements in patients in the semirecumbent position and following passive leg raising. Patients received propofol-based sedation, and significant intraprocedural hypotension was defined as a mean arterial pressure (MAP) < 60 mm Hg. The primary outcome was the occurrence of intravascular volume depletion as assessed by a positive result in a passive leg raise test on TTE (a 15% increase in the subaortic velocity time integral). Results Ninety-nine patients completed the study. The primary outcome was recorded in 29 of the 90 patients with adequate TTE images (32%; 95% confidence interval, 23 to 43). There was inadequate agreement between average TTE and ClearSight measurements of stroke volume at baseline or after passive leg raising. More patients experienced significant intraprocedural hypotension in the fluid-responsive group (48%) than in the normovolemic group (21%). Conclusion Patients undergoing elective colonoscopy after bowel preparation were often fluid responsive. These patients were more likely to have significant intraprocedural hypotension than patients who were volume replete. Transthoracic echocardiography assessment of volume status cannot be readily replaced by ClearSight monitoring.