Abstract: Background The hemodynamic effects of non-ionic contrast (iohexol) administration on invasive pressure measurements in dogs have not been evaluated. Hypothesis/ Objectives To evaluate effects of iohexol on invasive pressure assessment in dogs undergoing patent ductus arteriosus (PDA) occlusion or balloon valvuloplasty (BVP) for pulmonic stenosis (PS). The authors hypothesized there would not be a statistically or clinically relevant difference in measurements obtained pre and post-iohexol administration. Animals Client owned dogs undergoing PDA occlusion (N=15) or BVP (N=15). Methods Prospective observational study. Invasive pressures for PDA (main pulmonary artery (MPA) and aorta) and PS dogs (right ventricle and MPA) were obtained. Heart rate and direct peripheral blood pressure (BP) were recorded simultaneously. Pressures acquired prior to contrast injection (t0), 60-90 seconds post injection (t1), and 5 minutes post injection (t2). The mean pressure difference between time points was calculated, including peak-to-peak gradient (P2P) for PS dogs. Results There was a significant mean difference for the following: PDA group: diastolic and mean arterial pressure in the aorta between t1-t0 (p =0.019, 0.003) and diastolic BP between t2-t0 (p=0.020); in the PS group: MPA systolic BP between t1-t0 (p=0.02). There were wide 95% tolerance limits for most measurements, including P2P change between t1-0 and t2-0. Conclusions and clinical importance Although mean pressure change was generally not statistically significant, tolerance intervals suggest large changes can occur in some animals. Wide 95% tolerance limits for P2P could lead to misinterpretation of surgical success intra-operatively. Ideally, invasive pressure measurements should be obtained prior to contrast administration.
