Renal Perfusion Research Articles

Synthetic Angiotensin II ameliorates alterations of systemic hemodynamics, microcirculatory deterioration, and renal damage in septic rats

IntroductionSeptic shock is a systemic infection that causes persistent systemic hypotension, inflammation, tissue hypoperfusion and acute kidney injury (AKI). Despite norepinephrine being the currently recommended vasopressor agent, an alternative vasopressor agent that positively affects peripheral and organ microcirculatory perfusion and oxygenation is needed. This study investigated a new synthetic Angiotensin II agent suitable for improving microcirculatory parameters in a rat model of sepsis-induced systemic hemodynamic dysfunction. Methods48 mechanically ventilated, anesthetized male rats were allocated as control; lipopolysaccharide (LPS, 20 mg/kg) and LPS groups received either ringer acetate (RA), norepinephrine (NE), Angiotensin II (Ang II), or a combination of NE and Ang II. Systemic hemodynamics, renal cortical pO2 and perfusion, and muscle microcirculatory oxygen saturation were evaluated. ResultsMAP was restored in all LPS groups that received Ang II, NE, and NE + Ang II compared to the LPS group alone (p < 0.05). The deterioration of renal microcirculatory cortical oxygen, oxygen delivery, and consumption after sepsis was not restored by any of the resuscitation strategies. However, urine output was improved after Ang II resuscitation compared to the LPS and LPS + RA groups (p < 0.05). Furthermore, the muscle capillary oxygen saturation and functional capillary density (FCD) were improved by a combined infusion of NE and Ang II (p < 0.05). ConclusionsAng II can improve the MAP in rats in a way comparable to norepinephrine. Ang II increased urine output and muscle capillary oxygenation and reduced renal tissue damage. Our study supports that broad-spectrum vasopressors can benefit tissue perfusion and oxygenation in the resuscitation of septic patients.

The Relationship Between Postoperative Drainage Volume and the Incidence of Postoperative Renal Injury in Infants Undergoing Cardiac Surgery

Cardiac surgery-related acute kidney injury (CS-AKI) is a serious and frequently encountered complication that occurs in children undergoing cardiac surgery. It is particularly prevalent among those who undergo complex and prolonged surgical procedures. CS-AKI is a complex condition that can lead to significant morbidity and even mortality, and thus, understanding its pathogenesis and identifying potential risk factors is crucial for improving patient outcomes. One of the most consistent contributing factors to the development of CS-AKI is intraoperative bleeding. Bleeding during surgery can lead to hemodynamic instability, which in turn can affect renal perfusion and oxygen supply, ultimately leading to kidney injury. Intraoperative renal hypoperfusion and oxygen supply and demand imbalances are recognized as important pathogenic mechanisms underlying CS-AKI. To further investigate the relationship between intraoperative bleeding and postoperative kidney damage, researchers have conducted prospective observational studies. These studies focus on infants and young children undergoing cardiac surgery, as they are particularly vulnerable to the complications of such surgeries. By carefully observing and documenting the postoperative drainage volume, researchers aim to evaluate the correlation between postoperative blood loss and the incidence of postoperative renal injury. The results of these studies have provided valuable insights into the pathophysiology of CS-AKI. However, it is important to note that the correlation between postoperative eCrCl (estimated creatinine clearance) and postoperative drainage volume has not been found to be significant. This suggests that while intraoperative bleeding may contribute to the development of kidney injury, it may not be the sole determinant of renal outcome.

Autologous vein graft in living donor kidney transplant (case report)

Renal transplantation is the preferred treatment for end-stage renal disease, with vascular complications being a significant cause of graft dysfunction. Although many surgical methods are used to ensure the most effective possible vascular anastomosis, autologous saphenous vein grafting remains a less explored approach to renal transplantation. Chronic kidney disease often presents with complications related to impaired renal perfusion, necessitating interventions to improve blood flow to the kidneys. Herein, we present a case report detailing the utilization of autologous saphenous grafting to establish an anastomosis between the renal vein and external iliac vein in a patient with сhronic kidney disease with maintenance hemodialysis twice a week. This case report indicates the potential and prospective advantages of using autologous saphenous grafting for intricate renal vein reconstructions in patients with chronic kidney disease.

The effect of endoscopic renal and ureteral stone surgeries on renal blood flow in children: a prospective trial

Aim: To assess the impact of endoscopic stone surgeries on renal perfusion and blood flow in children. Materials and methods: Children who underwent percutaneous nephrolithotomy (PCNL), retrograde intrarenal surgery (RIRS), ureterorenoscopy (URS), endoscopic combined intrarenal surgery (ECIRS) were included to the study. Renal Doppler ultrasonography (RDUS) was performed one day before the operation, and on the postoperative 1st day and 1st month. Peak systolic velocity (PSV) and end-diastolic velocity (EDV) were measured, and resistive index (RI) was calculated with the (PSV-EDV)/PSV formula. RDUS parameters were compared before and after surgery and between ipsilateral and contralateral kidneys. Results: A total of 45 children with a median age was 8 (2–17) years were included (15 (33.3%) girls, 30 (66.7%) boys). PCNL was performed in 13 children (28.9%), RIRS 11 (24.4%), URS 12 (26.7%), and ECIRS 9 (20%). There was no significant difference in renal and segmental PSV, EDV and RI values of operated kidney in the preoperative, postoperative periods. There was no significant difference between RDUS parameters of the ipsilateral and contralateral kidneys in preoperative or postoperative periods. PSV and EDV values were significantly higher in the 1st postoperative month in the group without preoperative DJ stent than in the group with DJ stent (p = 0,031, p = 0,041, respectively). However, RI values were similar. The mean RI were below the threshold value of 0.7 in each period. Conclusion: RDUS parameters didn’t show a significant difference in children. Endoscopic surgeries can be safely performed in pediatric stone disease.

Value of Ultrasound Super-Resolution Imaging for the Assessment of Renal Microcirculation in Patients with Acute Kidney Injury: A Preliminary Study.

The present study aimed to explore the clinical applicability of ultrasound super-resolution imaging (US SRI) for assessing renal microcirculation in patients with acute kidney injury (AKI). A total of 62 patients with sepsis were enrolled in the present study-38 with AKI and 24 control patients-from whom renal ultrasounds and clinical data were obtained. SonoVue contrast (1.5 mL) was administered through the elbow vein and contrast-enhanced ultrasound (CEUS) images were obtained on a Mindray Resona A20 ultrasound unit for 2 min. The renal perfusion time-intensity curve (TIC) was analyzed and, after 15 min, additional images were obtained to create a microscopic blood flow map. Microvascular density (MVD) was calculated and its correlation with serum creatinine (Scr) levels was analyzed. There were significant differences in heart rate, Scr, blood urea nitrogen, urine volume at 24 h, and glomerular filtration rate between the two groups (p < 0.01), whereas other characteristics, such as renal morphology, did not differ significantly between the AKI group and control group (p > 0.05). The time to peak and mean transit times of the renal cortex in the AKI group were prolonged compared to those in the control group (p < 0.01), while the peak intensity and area under the TIC were lower than those in the control group (p < 0.05). The MVD of the renal cortex in the AKI group was lower than that in the control group (18.46 ± 5.90% vs. 44.93 ± 11.65%; p < 0.01) and the MVD in the AKI group showed a negative correlation with Scr (R = -0.84; p < 0.01). Based on the aforementioned results, US SRI can effectively assess renal microcirculation in patients with AKI and is a noninvasive technique for the diagnosis of AKI and quantitative evaluation of renal microcirculation.

Interventions for renal artery stenosis: Appraisal of novel physiological insights and procedural techniques to improve clinical outcome.

Randomized clinical trials failed to show additional benefit of renal artery stenting on top of medical therapy. Instead of writing an obituary on renal artery stenting, we try to explain these disappointing results. A transstenotic pressure gradient is needed to reduce renal perfusion and to activate the renin-angiotensin-aldosterone system. In only a minority of patients included in trials, a transstenotic pressure gradient is measured and reported. Like the coronary circulation, integration of physiological lesion assessment will allow to avoid stenting of non-significant lesions and select those patients that are most likely to benefit from renal artery stenting. Renal artery interventions are associated with peri-procedural complications. Contemporary techniques, including radial artery access, no-touch technique to engage the renal ostium and the use of embolic protection devices, will minimize procedural risk. Combining optimal patient selection and meticulous technique might lead to a netto clinical benefit when renal artery stenting is added to optimal medical therapy.

The role of preterm birth in stress-induced sodium excretion in young adults.

Early-life programming due to prematurity and very low birth weight (VLBW, <1500 g) is believed to contribute to development of hypertension, but the mechanisms remain unclear. Experimental data suggest that altered pressure natriuresis (increased renal perfusion pressure promoting sodium excretion) may be a contributing mechanism. We hypothesize that young adults born preterm will have a blunted pressure natriuresis response to mental stress compared with those born term. In this prospective cohort study of 190 individuals aged 18-23 years, 156 born preterm with VLBW and 34 controls born term with birth weight at least 2500 g, we measured urine sodium/creatinine before and after a mental stress test and continuous blood pressure before and during the stress test. Participants were stratified into groups by the trajectory at which mean arterial pressure (MAP) increased following the test. The group with the lowest MAP trajectory was the reference group. We used generalized linear models to assess poststress urine sodium/creatinine relative to the change in MAP trajectory and assessed the difference between groups by preterm birth status. Participants' mean age was 19.8 years and 57% were women. Change in urine sodium/creatinine per unit increase in MAP when comparing middle trajectory group against the reference group was greater in those born preterm [β 5.4%, 95% confidence interval (95% CI) -11.4 to 5.3] than those born term (β 38.5%, 95% CI -0.04 to 92.0), interaction term P = 0.002. We observed that, as blood pressure increased following mental stress, young adults born preterm exhibited decreased sodium excretion relative to term-born individuals.

Interaction of Angiotensin-(1−7) with kinins in the kidney circulation: Role of B1 receptors

Changes in renal hemodynamics impact renal function during physiological and pathological conditions. In this context, renal vascular resistance (RVR) is regulated by components of the Renin-Angiotensin System (RAS) and the Kallikrein-Kinin System (KKS). However, the interaction between these vasoactive peptides on RVR is still poorly understood. Here, we studied the crosstalk between angiotensin-(1−7) and kinins on RVR. The right kidneys of Wistar rats were isolated and perfused in a closed-circuit system. The perfusion pressure and renal perfusate flow were continuously monitored. Ang-(1−7) (1.0–25.0 nM) caused a sustained, dose-dependent reduction of relative RVR (rRVR). This phenomenon was sensitive to 10 nM A-779, a specific Mas receptor (MasR) antagonist. Bradykinin (BK) promoted a sustained and transient reduction in rRVR at 1.25 nM and 125 nM, respectively. The transient effect was abolished by 4 μM des-Arg9-Leu8-bradykinin (DALBK), a specific kinin B1 receptor (B1R) antagonist. Accordingly, des-Arg9-bradykinin (DABK) 1 μM (a B1R agonist) increased rRVR. Interestingly, pre-perfusion of Ang-(1−7) changed the sustained reduction of rRVR triggered by 1.25 nM BK into a transient effect. On the other hand, pre-perfusion of Ang-(1−7) primed and potentiated the DABK response, this mechanism being sensitive to A-779 and DALBK. Binding studies performed with CHO cells stably transfected with MasR, B1R, and kinin B2 receptor (B2R) showed no direct interaction between Ang-(1−7) with B1R or B2R. In conclusion, our findings suggest that Ang-(1−7) differentially modulates kinin's effect on RVR in isolated rat kidneys. These results help to expand the current knowledge regarding the crosstalk between the RAS and KKS complex network in RVR.

Influence of Aortic Arch Morphology on Renal Perfusion in Patients with Coarctation of the Aorta: An Exploratory Study.

Objectives: The configuration of the aortic arch, particularly a Gothic arch shape, in individuals with corrected coarctation of the aorta (CoA) has been associated with a decreased systolic wave amplitude across the arch, which could potentially impair renal perfusion and elevate the risk of arterial hypertension. This study aims to explore the relationship between the morphological characteristics of the aortic arch and their impact on renal perfusion in patients with CoA. Methods: Seventy-one subjects with corrected CoA underwent continuous 24 h ambulatory blood pressure monitoring, computed tomography to assess the aortic arch, and renal perfusion scanning. Subjects were stratified into three groups based on the height-to-width (H/W) ratio of their aortic arch: Group 1 with a H/W ratio of <0.65, Group 2 with a H/W ratio between 0.65 and 0.85, and Group 3 with a H/W ratio of >0.85. Results: Groups 1 and 2 (53,78% and 62.63%) presented with a higher hypertension prevalence of elevated blood pressure than Group 3 (38.89%). Notable variations were observed among the subjects in the time to peak perfusion (Tmax) in the left kidney across the groups. Group 1 showed a median Tmax at 0.27, Group 2 at 0.13, and Group 3 at -0.38 (p-value = 0.079). The differences in Tmax for the right kidney followed a similar trend but were not statistically significant (Group 1 at 0.61, Group 2 at 0.22, and Group 3 at 0.11; p-value = 0.229). Conclusions: This study suggests that variations in the aortic arch morphology might not significantly influence renal perfusion in CoA patients. This indicates the potential adaptability of the renal blood flow, which appears to compensate for reduced perfusion, thus minimizing adverse effects on the kidney function. This adaptability suggests an inherent physiological resilience, emphasizing the need for further targeted research to understand the specific interactions and impacts on treatment strategies for CoA.

Effects of Hemorrhagic Shock and Rhabdomyolysis on Renal Microcirculation, Oxygenation, and Function in a Female Swine Model.

Hemorrhagic shock (HS) and rhabdomyolysis (RM) are two important risk factors for acute kidney injury after severe trauma; however, the effects of the combination of RM and HS on kidney function are unknown. The purpose of this study was to determine the impact of RM and HS on renal function, oxygenation, perfusion, and morphology in a pig model. Forty-seven female pigs were divided into five groups: sham, RM, HS, HS and moderate RM (RM4/HS), and HS and severe RM (RM8/HS). Rhabdomyolysis was induced by intramuscular injection of glycerol 50% with a moderate dose (4 ml/kg for the RM4/HS group) or a high dose (8 ml/kg for the RM and RM8/HS groups). Among animals with HS, after 90 min of hemorrhage, animals were resuscitated with fluid followed by transfusion of the withdrawn blood. Animals were followed for 48 h. Macro- and microcirculatory parameters measurements were performed. RM alone induced a decrease in creatinine clearance at 48 h (19 [0 to 41] vs. 102 [56 to 116] ml/min for RM and sham, respectively; P = 0.0006) without alteration in renal perfusion and oxygenation. Hemorrhagic shock alone impaired temporarily renal microcirculation, function, and oxygenation that were restored with fluid resuscitation. The RM4/HS and RM8/HS groups induced greater impairment of renal microcirculation and function than HS alone at the end of blood spoliation that was not improved by fluid resuscitation. Mortality was increased in the RM8/HS and RM4/HS groups in the first 48 h (73% vs. 56% vs. 9% for the RM8/HS, RM4/HS, and HS groups, respectively). The combination of HS and RM induced an early deleterious effect on renal microcirculation, function, and oxygenation with decreased response to resuscitation and transfusion compared with HS or RM alone.

Exploring Acute Kidney Injury Following Aortic Dissection: A Comprehensive Review of Machine Learning Models for Predicting Risk, Management Strategies, Complications, and Racial and Gender Disparities.

Both types of aortic dissection (AD), Stanford type A and type B, can result in complications such as acute kidney injury (AKI) and aortic rupture. Renal complications in AD arise from compromised renal perfusion affecting the renal arteries. Understanding the intricate connection between AD and AKI is crucial for navigating the complexities of tailored treatment and formulating specific management plans. Concerning machine learning models, in patients with type A aortic dissection, factors such as decreased platelet count on admission, increased D-dimer level, longer cardiopulmonary bypass duration, elevated white blood cell levels, the need for blood transfusion, longer aortic clamp time, extended surgery duration, advanced age, and an elevated body mass index were positively associated with the development of AKI. For the risk of AKI after type B aortic dissection, elevated Nt-pro brain natriuretic peptide, prolonged activated partial thromboplastin time, elevated admission systolic blood pressure, and a higher contrast agent requirement during operative repair were found to predict the risk. Male gender was associated with a higher risk of AKI, and nonwhite race was linked to a higher risk of AKI, a greater likelihood of requiring more urgent procedures, and lower levels of insurance coverage. The treatment of AKI following AD requires a multifaceted approach. Identifying and addressing the underlying cause, such as low blood pressure, renal artery involvement, or medication-induced injury, is crucial for effective management and preventing further kidney damage. Maintaining proper fluid balance is essential for improving renal perfusion, but careful monitoring is necessary to avoid complications. The evolving landscape of research, particularly in biomarkers and AI programs, reveals a promising role in predicting the risk for and managing AKI post-AD.

#2500 Renal perfusion and SGLT2i

Abstract Background and Aims Sodium-Glucose Cotransporter 2 inhibitors (SGLT2i) have revolutionized treatment of type 2 diabetes mellitus (DM2) and chronic kidney disease (CKD), improving cardiovascular and renal endpoints. This improvement could be due to a decrease in renal perfusion (RP), attenuating glomerular hyperfiltration thus leading to kidney protection. This has been demonstrated in patients with type 1 diabetes and in animal studies, but not in patients with DM2 and it has never before been investigated in patients with CKD. Our aim was to examine the effects of the SGLT2i empagliflozin on RP in patients with DM2, DM2 and CKD and non-diabetic CKD, respectively. Methods We conducted three randomized, double-blind placebo controlled cross-over studies, including patients with: Participants were randomized to four weeks' treatment with empagliflozin 10 mg or matching placebo and were, after a washout period of at least two weeks, crossed over to four weeks of the opposite treatment. At the end of each treatment period we measured RP using 82Rb-PET/CT and standardized GFR using 99mTc-DTPA-clearence. We also measured 24-hour ambulatory blood pressure (BP), urinary albumin/creatinine ratio (UACR) and Hb1Ac. Results A total of 49 patients completed the studies, 16 in the DM2-group, 17 in the DM2-CKD-group and 16 in the CKD-group. In the combined study-population empagliflozin reduced RP compared to placebo by 4% (geometric mean ratio: 0.96, 95% CI: 0.94; 0.99, p = 0.0171). This change was most pronounced in the DM2-CKD-group, with a reduction of 6% (geometric mean ratio: 0.94, 95% CI: 0.91; 0.97), p &amp;lt; 0.001). There was a decrease of 4% in the DM2-group and 1% in the CKD-group, though these changes were not statistically significant (p = 0.29 and 0.72, respectively, see Fig. 1). In the 29 patients with a UACR &amp;gt; 30 mg/g, empagliflozin treatment led to a significant decrease in UACR in the combined study-population (geometric mean ratio: 0.61, 95% CI: 0.46; 0.80, p = 0.001), again primarily driven by a decrease in the DM2-CKD-group (geometric mean ratio: 0.51, 95% CI: 0.31; 0.85, p = 0.014), with non-significant decreases in the remaining groups. Empagliflozin decreased standardized GFR and BP in the combined population as well as in all sub-groups, while we found no change in Hb1Ac. For further details, see Table 1. Conclusion Short-term empagliflozin treatment reduces RP, GFR, BP and albumin excretion. Relative changes in RP and UACR were most pronounced in patients with concomitant DM2 and CKD, whereas changes in BP and GFR were seen in all groups.

#337 Renal 3D photoacoustic imaging and contrast-enhanced ultrasound to assess oxygenation and perfusion and to predict fibrosis after ischemia-reperfusion

Abstract Background and Aims Renal 3D photo-acoustic imaging (3D-PAI) and contrast-enhanced ultrasound (CEUS) are promising tools in mice models to assess repeatedly and non-invasively renal ischemia-reperfusion (RIR) consequences and damages, or their improvement by nephroprotective strategies like mild therapeutic hypothermia (mTH), at the early phase of reperfusion as well as in the chronic late phase. Method C57Bl6 mice underwent 15 minutes of unilateral renal vascular clamping, with body temperature at 37°C (RIR-37°C, n=7) or mTH at 34°C (RIR-34°C, n=7), or a sham procedure (Sham, n=5). Renal volume and oxygen saturation (sO2-3D; corresponding to the percentage of oxyhemoglobin over the total hemoglobin content) were measured with 3D-PAI (3D reconstruction of the whole kidney through multi-plane acquisition with an automatized mobile support), and renal perfusion parameters (rBV, mTT, rBF) with CEUS (“destruction-replenishment” model of intravenous microbubbles), performed with VEVO3100 echograph (Fujifilm Visualsonic) 1 week before RIR (basal), 20 minutes after reperfusion, and 1 month after. Renal fibrosis was quantified at 1 month with Masson's trichrome coloration on histological samples. Data were compared with Mann-Whitney test or Wilcoxon test (paired data) as appropriate. Correlation was tested by Spearman test. All animal procedures were approved by the Ethics Committee. Results Sham showed no significant changes during follow-up. RIR-37°C led to renal hypotrophy (volume on 3D-PAI) and fibrosis at 1 month, compared to RIR-34°C (median volume 76 IQR [71-119] vs 143 IQR[108-180] mm3; p=0.03), and those parameters were correlated (R=−0.49; p=0.03). In RIR-37°C, sO2-3D tended to lower at 20 minutes compared to basal values (median sO2-3D 37 IQR [37-44] vs 49 IQR [36-57]%; p=0.08), but not in RIR-34°C (p &amp;gt; 0.99), and these early variations of sO2-3D were correlated with fibrosis at 1 month (R=−0.48; p=0.04). Renal perfusion was altered in RIR-37°C at 20 minutes compared to basal values (median rBV 73 IQR [46-105] vs 100 IQR [89-126] a.u.; p=0.047), and remained altered at 1 month (median rBV 71 IQR [57-83] a.u.; p=0.03), but not in RIR-34°C (p=0.47 at both 20 minutes and 1 month). Renal perfusion early alterations at 20 minutes were correlated with late alterations at 1 month (R=0.63; p=0.005), and tended to correlate with fibrosis (R=−0.41; p=0.08). Conclusion Renal 3D-PAI (on the whole 3D-reconstructed kidney) and CEUS can detect early alterations of renal perfusion and oxygen saturation after RIR, and predict chronic disturbances of perfusion and the onset of fibrosis, as well as the protection conferred by mTH. 3D-PAI can also be used to evaluate non-invasively renal volume as a surrogate of renal fibrosis after RIR.

#2781 Renal cortical necrosis—a rare cause of acute kidney injury

Abstract Background and Aims Renal cortical necrosis (RCN) is a rare and catastrophic cause of acute kidney injury (AKI). It is characterized by ischemic destruction of all the elements of renal cortex due to marked reduction in renal arterial perfusion of renal cortex due to vascular spasm and microvascular injury. It can be patchy or diffuse depending upon the cause and extent of hypoperfusion. Snake bite is rare cause of RCN. Incidence of RCN following snake bite has been reported to be as high as in 25% of the bitten patients to &amp;lt;1%. Lack or delay in receiving anti snake venom (ASV) has been observed to be a contributing factor in development of RCN following snake bite. Method A 45-year-old female had an unknown bite on foot while returning to home at twilight. She had intense pain at site of bite with slight ooze of blood. Overnight she had vomiting and pain abdomen. Subsequently she developed progressive fall in urine output and dyspnoea. After about 36 hours of bite at the time of admission in hospital she had anuria, prolonged whole blood clotting time, tachypnoea, hypoxemia and required oxygen (O2) to maintain normal O2 saturation. She was given two doses of polyvalent ASV 6 hours apart which corrected her coagulation defect. Investigations showed: haemoglobin—9 gm/dl, total leucocyte count—18700/mcl, platelet—1.15 lakh/mcl, blood urea—88 mg/dl and serum creatinine—10.5 mg/dl. She was managed with haemodialysis and supportive care. Even after 3 weeks of onset of AKI, she had anuria so a kidney biopsy was done. Results kidney biopsy on light microscopy examination showed 9 glomeruli; 8 revealing global tuft necrosis along with necrosis of adjacent tubules and vasculature and necrotic process affected around 60% of sampled cortical area consistent with cortical necrosis (Fig. 1). She was continued with haemodialysis support and urine output and pre-dialysis serum creatinine were monitored. Her urine output after 3 months of onset of AKI is around one litre per day but her pre-dialysis serum creatinine stays in the range of 9-10 mg/dl and so she continues to receive biweekly haemodialysis. Conclusion In our index case, there was delay in getting ASV which may have contributed to development of RCN. So, early treatment of snake bite is important to prevent this catastrophic complication.

Acute Kidney Injury and Aorta-Related Mlity During Open Surgery of the Abdominal Aorta With Suprarenal Clamping Using Different Renal Perfusion Solutions

Acute Kidney Injury and Aorta-Related Mlity During Open Surgery of the Abdominal Aorta With Suprarenal Clamping Using Different Renal Perfusion Solutions

Periods of low renal perfusion pressure are associated with acute kidney injury following paediatric cardiac surgery.

Acute kidney injury is associated with worse outcomes after cardiac surgery. The haemodynamic goals to ameliorate kidney injury are not clear. Low post-operative renal perfusion pressure has been associated with acute kidney injury in adults. Inadequate oxygen delivery may also cause kidney injury. This study evaluates pressure and oximetric haemodynamics after paediatric cardiac surgery and their association with acute kidney injury. Retrospective case-control study at a children's hospital. Patients were < 6 months of age who underwent a Society of Thoracic Surgery-European Association for Cardio-Thoracic Surgery Congenital Heart Surgery categories ≥ 3. Low renal perfusion pressure was time and depth below several tested thresholds. The primary outcome was serum creatine-defined acute kidney injury in the first 7 days. Sixty-six patients (median age 8 days) were included. Acute kidney injury occurred in 36%. The time and depth of renal perfusion pressure < 42 mmHg in the first 24 hours was greater in acute kidney injury patients (94 versus 35 mmHg*minutes of low renal perfusion pressure/hour, p = 0.008). In the multivariable model, renal perfusion pressure < 42 mmHg was associated with acute kidney injury (aOR: 2.07, 95%CI: 1.25-3.82, p = 0.009). Mean arterial pressure, central venous pressure, and measures of inadequate oxygen delivery were not associated with acute kidney injury. Periods of low renal perfusion pressure (<42 mmHg) in the first 24 post-operative hours are associated with acute kidney injury. Renal perfusion pressure is a potential modifiable target that may mitigate the impact of acute kidney injury after paediatric cardiac surgery.

Bridging Stent-Graft Implantation in the Renal Artery During Complex Endovascular Aortic Procedures does not alter the Renal Sonographic Resistance Index

Abstract Background Ultrasound examination of the resistance index (RI) of both kidneys can provide evidence of renal artery stenosis. The extent to which the RI is changed after bridging stent-graft implantation due to altered flow characteristics is not known. Aims The aim of the study was to investigate the influence of renal bridging stent-grafts on the RI of the kidneys after fenestrated endovascular aortic repair (FEVAR). Methods Ultrasound examinations of the kidneys were conducted using a GE LOGIQ S7 XDclear ultrasound system (GE Medical Systems AG, Glattburg, Switzerland). The evaluation was performed according to SGUM 2D standard criteria. The RI was determined in all consecutive patients on the day before and after renal bridging stent-graft implantation. For this purpose, the kidneys were divided into 3 areas according to the standard protocol and 2 RI values were recorded per area by evaluating intrarenal arterial Doppler signals. Mean values were calculated and compared for each kidney. Results For 64 kidneys in 32 consecutive patients (73.9±7.8 years, 4 female, 28 male) treated with FEVAR and renal bridging stent–graft implantation pre- and postinterventional examinations were carried out. Sono-morphologically, the kidneys examined were inconspicuous (pre: size at least 107.1x52.4 mm, parenchymal margin 18.3 mm versus post: size at least 107.9x52.9 mm, parenchymal margin 18.6 mm, p&amp;gt;0.4). The arborization of the renal perfusion was preserved pre and post implantation. The RI did not differ before and after implantation (0.66±0.06 versus 0.67±0.07; p=0.10). None of the patients experienced severe impairment of renal function. Conclusion After successful implantation of a bridging stent-graft in a non-stenosed renal artery, there is no relevant change in the RI of the kidney. The RI seems therefore to be suitable for assessing renal perfusion after complex endovascular aortic therapy.

Midodrine plus propranolol versus propranolol alone in preventing first bleed in patients with cirrhosis and severe ascites: a randomized controlled trial.

Propranolol, a non-selective beta-blocker, commonly used to prevent variceal bleed, but might precipitate circulatory dysfunction in severe ascites. Midodrine, an alpha-1 adrenergic agonist improves renal perfusion and systemic hemodynamics. Addition of midodrine might facilitate higher maximum tolerated dose (MTD) of propranolol, thereby less risk of variceal bleed in cirrhosis patients with severe ascites. 140 patients with cirrhosis and severe/refractory ascites were randomized- propranolol and midodrine (Gr.A,n = 70) or propranolol alone (Gr.B,n = 70). Primary outcome was incidence of bleed at 1year. Secondary outcomes included ascites control, achievement of target heart rate (THR), HVPG response and adverse effects. Baseline characteristics were comparable between two groups. Cumulative incidence of bleed at 1year was lower in Gr.A than B (8.5%vs.27.1%,p-0.043). The MTD of propranolol was higher in Gr.A (96.67 ± 36.6mg vs. 76.52 ± 24.4mg; p-0.01) and more patients achieved THR (84.2%vs.55.7%,p-0.034). Significantly higher proportion of patients in Gr.A had complete resolution of ascites [17.1%vs.11.4%,p-0.014), diuretic tolerance (80%vs.60%,p-0.047) at higher doses(p-0.02) and lesser need for paracentesis. Patients in Gr.A also had greater reduction in variceal grade (75.7%vs.55.7%;p-0.01), plasma renin activity (54.4% from baseline) (p = 0.02). Mean HVPG reduction was greater in Gr.A than B [4.38 ± 2.81mmHg(23.5%) vs. 2.61 ± 2.87mmHg(14.5%),p-0.045]. Complications like post-paracentesis circulatory dysfunction and spontaneous bacterial peritonitis on follow-up were higher in Gr.B than A (22.8%vs.51.4%,p = 0.013 and 10%vs.15.7%, p = 0.03, respectively). Addition of midodrine facilitates effective use of propranolol in higher doses and greater HVPG reduction, thereby preventing first variceal bleed, reduced paracentesis requirements with fewer ascites- related complications in patients with cirrhosis with severe/refractory ascites.

Dynamic rubidium-82 PET/CT as a novel tool for quantifying hemodynamic differences in renal blood flow using a one-tissue compartment model.

Assessing renal perfusion in-vivo is challenging and quantitative information regarding renal hemodynamics is hardly incorporated in medical decision-making while abnormal renal hemodynamics might play a crucial role in the onset and progression of renal disease. Combining physiological stimuli with rubidium-82 positron emission tomography/computed tomography (82Rb PET/CT) offers opportunities to test the kidney perfusion under various conditions. The aim of this study is: (1) to investigate the application of a one-tissue compartment model for measuring renal hemodynamics with dynamic 82Rb PET/CT imaging, and (2) to evaluate whether dynamic PET/CT is sensitive to detect differences in renal hemodynamics in stress conditions compared to resting state. A one-tissue compartment model for the kidney was applied to cardiac 82Rb PET/CT scans that were obtained for ischemia detection as part of clinical care. Retrospective data, collected from 17 patients undergoing dynamic myocardial 82Rb PET/CT imaging in rest, were used to evaluate various CT-based volumes of interest (VOIs) of the kidney. Subsequently, retrospective data, collected from 10 patients (five impaired kidney functions and five controls) undergoing dynamic myocardial 82Rb PET/CT imaging, were used to evaluate image-derived input functions (IDIFs), PET-based VOIs of the kidney, extraction fractions, and whether dynamic 82Rb PET/CT can measure renal hemodynamics differences using the renal blood flow (RBF) values in rest and after exposure to adenosine pharmacological stress. The delivery rate (K1) values showed no significant (p=0.14) difference between the mean standard deviation (SD) K1 values using one CT-based VOI and the use of two, three, and four CT-based VOIs, respectively 2.01(0.32), 1.90(0.40), 1.93(0.39), and 1.94(0.40) mL/min/mL. The ratio between RBF in rest and RBF in pharmacological stress for the controls were overall significantly lower compared to the impaired kidney function group for both PET-based delineation methods (region growing and iso-contouring), with the smallest median interquartile range (IQR) of 0.40(0.28-0.66) and 0.96(0.62-1.15), respectively (p<0.05). The K1 of the impaired kidney function group were close to 1.0mL/min/mL. This study demonstrated that obtaining renal K1 and RBF values using 82Rb PET/CT was feasible using a one-tissue compartment model. Applying iso-contouring as the PET-based VOI of the kidney and using AA as an IDIF is suggested for consideration in further studies. Dynamic 82Rb PET/CT imaging showed significant differences in renal hemodynamics in rest compared to when exposed to adenosine. This indicates that dynamic 82Rb PET/CT has potential to detect differences in renal hemodynamics in stress conditions compared to the resting state, and might be useful as a novel diagnostic tool for assessing renal perfusion.

Impact of arginine-vasopressin on regional perfusions in a porcine model of post-resuscitation syndrome

BackgroundPost-cardiac arrest (CA) shock is associated with multiple organ failure, including acute kidney injury, and is the leading cause of early death among patient successfully resuscitated from CA. Arginine-vasopressin (AVP) may be an interesting therapeutic alternative or complement to noradrenaline (NAD) to both control shock and preserve regional, especially renal, organ perfusions. Methods18 swine (24–39 kg) were submitted to 14 min of ventricular fibrillation and cardio-pulmonary resuscitation. After return of spontaneous circulation (ROSC), animals randomly received either AVP, NAD or AVP-NAD combination for maintaining a targeted mean arterial pressure of 70 ± 5 mmHg for 6 h. Haemodynamic and biological parameters, including kidney function biomarkers and diuresis, were monitored throughout the follow-up. ResultsTargeted mean arterial pressure was successfully obtained in the NAD (n = 6) and the AVP-NAD (n = 6) groups, but not in the AVP group (n = 6), where 4 animals died. As compared to NAD alone, renal blood flow (2.9 ± 1.15 vs 4.36 ± 0.64 mL//kg/min in NAD and AVP-NAD groups) and diuresis were higher in the AVP-NAD group. This was associated with a reduction of carotid blood flow and a more severe metabolic acidosis during the first 3 h of follow-up in the AVP-NAD group as compared to NAD group. ConclusionCombination of AVP and NAD improved renal perfusion and diuresis but reduced carotid blood flow as compared to NAD alone in a porcine model of post-resuscitation syndrome. AVP alone failed to manage shock and led to mortality.