Intra-aortic balloon pumping increases renal blood flow in patients with low left ventricular ejection fraction

Intra-aortic balloon pumping (IABP) has, for decades, been one of the key treatment modalities following impaired cardiac function after cardiac surgery. IABP increases cardiac output, decreases oxygen consumption of the heart and relieves the left ventricle. However, a number of complications have been reported in connection with IABP treatment. Only a few studies have evaluated renal blood flow and the purpose of this prospective study was to evaluate whether renal blood flow was affected by IABP treatment in high-risk patients. After approval from the county ethical committee and informed consent, seven consecutive patients with low left ventricular ejection fraction and scheduled for preoperative IABP treatment were allocated to the study. Assessment of renal blood flow was based on ultrasound spectral Doppler estimation of the flow velocity profiles in the interlobar kidney arteries. The result was described as balloon index (BI), which is maximal systolic velocity divided by the temporal mean velocity. Typical velocity profiles were demonstrated in all patients before, during and after IABP. BI measurement changed with time (p <0.05). BI was lower during IABP compared to both pre-IABP and post-IABP (p <0.025), indicating a higher renal blood flow. No statistically significant changes were seen in s-creatinine or creatinine clearance. Assuming unchanged diameter of kidney arteries and no considerable decrease in renal resistance and/or compliance, we conclude that the interlobar renal blood flow was significantly increased during IABP treatment, measured by ultrasound Doppler technique, but without a simultaneously significant change in creatinine clearance.