Hemodynamics During Colonoscopy Using Impedance Cardiography

Abstract

Purpose: To measure the cardiac output, stroke volume, heart rate and blood pressure before and during colonoscopy in normal subjects without a prior history of heart disease. Methods: 20 normal controls (5 males, 15 females), with a mean age of 59.9¡À12.6 underwent colonoscopy. Cardiac output (CO), stroke volume (SV) and heart rate (HR) were measured noninvasively five minutes prior to and during the colonoscopy procedure using impedance cardiography. Mean CO, SV, BP and HR pre-procedure was compared to the same parameters post-procedure in each patient to determine any changes. Results: During the colonoscopy cardiac output decreased by 19.6% (p < 0.002), stroke volume decreased by 22.9% (p < 0.0004), systolic blood pressure decreased by 5% (p < 0.006). The heart rate remained stable. Conclusions: Continuous measurement of cardiac impedence makes it possible to measure and calculate cardiac output and stroke volume during colonoscopy. Cardiac output, stroke volume and systolic BP decrease significantly during colonoscopy, without a change in heart rate. We hypothesize that the decrease in CO and SV is not due to vasovagal effects, since there was no change in heart rate, but is due to increased intraabdominal pressure, caused by compression of the inferior vena cava, secondary to air insufflation and external compression. Compression of the inferior vena cava leads to decreased cardiac blood return, decreased pre-load and a subsequent decrease in SV and CO. This study has implications for cardiac patients with already compromised CO who are undergoing colonoscopy.