Short-term effects of intra-aortic balloon pumping on renal blood flow and renal oxygen consumption in cardiogenic shock

A Mock Circulatory Loop Analysis of Cardiorenal Hemodynamics With Intra-Aortic Mechanical Circulatory Support

Type 1 cardiorenal syndrome is associated with significant excess morbidity and mortality in patients with severe acute decompensated heart failure. Previous trials of vasoactive drugs and ultrafiltration have not shown superiority over placebo or intravenous diuretics. Pilot data suggest short-term mechanical support devices may support diuresis in the cardiorenal syndrome. We evaluated the intra-aortic balloon pump (IABP) and a novel intra-aortic entrainment pump (IAEP) in a mock circulation loop (MCL) biventricular systolic heart failure model, to assess impact on renal flow and cardiac hemodynamics. Both devices produced similar and only modest increase in renal flow (IABP 3.3% vs. IAEP 4.3%) and cardiac output, with associated reduction in afterload elastance in the MCL. There were minor changes in coronary flow, increase with IABP and minor decrease with IAEP. Differences in device preload and afterload did not impact percentage change in renal flow with IABP therapy, however, there was a trend toward higher percentage flow change with IAEP in response to high baseline renal flow. The IAEP performed best in a smaller aorta and with more superior positioning within the descending aorta. Demonstrated changes in MCL flow during IAEP were of lower magnitude than previous animal studies, possibly due to lack of autoregulation and hormonal responses.

Acute kidney injury and cardiac arrest in the modern era: an updated systematic review and meta-analysis

Objective: Acute kidney injury (AKI) is associated with higher morbidity and mortality in cardiac arrest (CA). There are limited contemporary data on the incidence and outcomes of AKI in CA.Methods: We comprehensively searched the databases of MEDLINE, EMBASE, PUBMED, and the Cochrane from inception to November 2020. Observational studies that reported the incidence of AKI in CA survivors were included. Data from each study were combined using the random effects to calculate pooled incidence and risk ratios with 95% confidence intervals (CIs). The primary outcome was short-term mortality and secondary outcomes included long-term mortality, incidence of AKI, and use of renal replacement therapy (RRT). Subgroup and meta-regression analyses were performed to explore heterogeneity.Main results: A total of 25 observational studies comprising 8,165 patients were included. The incidence of AKI in CA survivors was 40.3% (range 32.9-47.8%). In stage 3 AKI, one-fourth of patients required RRT. AKI was associated with an increased risk of both short-term (OR 2.27 [95% CI 1.74-2.96]; p < 0.001) and long-term mortality (OR 1.51 [95% CI 1.93-3.25]; p < 0.001). Meta-regression and subgroup analyses did not suggest any effect of hypothermia on incidence of AKI.Conclusion: AKI complicates the care of 40% of CA survivors and is associated with significantly increased short- and long-term mortality.

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.

Metabolic setpoint control mechanisms in different physiological systems at rest and during exercise

Using a number of different homeostatic control mechanisms in the brain and peripheral physiological systems, metabolic activity is continuously regulated at rest and during exercise to prevent catastrophic system failure. Essential for the function of these regulatory processes are baseline "setpoint" levels of metabolic function, which can be used to calculate the level of response required for the maintenance of system homeostasis after system perturbation, and to which the perturbed metabolic activity levels are returned to at the end of the regulatory process. How these setpoint levels of all the different metabolic variables in the different peripheral physiological systems are created and maintained, and why they are similar in different individuals, has not been well explained. In this article, putative system regulators of metabolic setpoint levels are described. These include that: (i) innate setpoint values are stored in a certain region of the central nervous system, such as the hypothalamus; (ii) setpoint values are created and maintained as a response to continuous external perturbations, such as gravity or "zeitgebers", (iii) setpoint values are created and maintained by complex system dynamical activity in the different peripheral systems, where setpoint levels are regulated by the ongoing feedback control activity between different peripheral variables; (iv) human anatomical and biomechanical constraints contribute to the creation and maintenance of metabolic setpoints values; or (v) a combination of all these four different mechanisms occurs. Exercise training and disease processes can affect these metabolic setpoint values, but the setpoint values are returned to pre-training or pre-disease levels if the training stimulus is removed or if the disease process is cured. Further work is required to determine what the ultimate system regulator of metabolic setpoint values is, why some setpoint values are more stringently protected by homeostatic regulatory mechanisms than others, and the role of conscious decision making processes in determining the regulation of metabolic setpoint values.