Ultrasound Modulates the Splenic Neuroimmune Axis in Attenuating AKI.

We showed previously that prior exposure to a modified ultrasound regimen prevents kidney ischemia-reperfusion injury (IRI) likely via the splenic cholinergic anti-inflammatory pathway (CAP) and α7 nicotinic acetylcholine receptors (α7nAChR). However, it is unclear how ultrasound stimulates the splenic CAP. Further investigating the role of the spleen in ischemic injury, we found that prior splenectomy (-7d) or chemical sympathectomy of the spleen with 6-hydroxydopamine (6OHDA; -14d) exacerbated injury after subthreshold (24-minute ischemia) IRI. 6-OHDA-induced splenic denervation also prevented ultrasound-induced protection of kidneys from moderate (26-minute ischemia) IRI. Ultrasound-induced protection required hematopoietic but not parenchymal α7nAChRs, as shown by experiments in bone marrow chimeras generated with wild-type and α7nAChR(-/-) mice. Ultrasound protection was associated with reduced expression of circulating and kidney-derived cytokines. However, splenocytes isolated from mice 24 hours after ultrasound treatment released more IL-6 ex vivo in response to LPS than splenocytes from sham mice. Adoptive transfer of splenocytes from ultrasound-treated (but not sham) mice to naïve mice was sufficient to protect kidneys of recipient mice from IRI. Ultrasound treatment 24 hours before cecal ligation puncture-induced sepsis was effective in reducing plasma creatinine in this model of AKI. Thus, splenocytes of ultrasound-treated mice are capable of modulating IRI in vivo, supporting our ongoing hypothesis that a modified ultrasound regimen has therapeutic potential for AKI and other inflammatory conditions.

Validation of the pulse decomposition analysis algorithm using central arterial blood pressure.

BACKGROUND: There is a significant need for continuous noninvasive blood pressure (cNIBP) monitoring, especially for anesthetized surgery and ICU recovery. cNIBP systems could lower costs and expand the use of continuous blood pressure monitoring, lowering risk and improving outcomes.The test system examined here is the CareTaker® and a pulse contour analysis algorithm, Pulse Decomposition Analysis (PDA). PDA's premise is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses that are due to the left ventricular ejection and reflections and re-reflections from only two reflection sites within the central arteries.The hypothesis examined here is that the model's principal parameters P2P1 and T13 can be correlated with, respectively, systolic and pulse pressures. METHODS: Central arterial blood pressures of patients (38 m/25 f, mean age: 62.7 y, SD: 11.5 y, mean height: 172.3 cm, SD: 9.7 cm, mean weight: 86.8 kg, SD: 20.1 kg) undergoing cardiac catheterization were monitored using central line catheters while the PDA parameters were extracted from the arterial pulse signal obtained non-invasively using CareTaker system. RESULTS: Qualitative validation of the model was achieved with the direct observation of the five component pressure pulses in the central arteries using central line catheters. Statistically significant correlations between P2P1 and systole and T13 and pulse pressure were established (systole: R square: 0.92 (p < 0.0001), diastole: R square: 0.78 (p < 0.0001). Bland-Altman comparisons between blood pressures obtained through the conversion of PDA parameters to blood pressures of non-invasively obtained pulse signatures with catheter-obtained blood pressures fell within the trend guidelines of the Association for the Advancement of Medical Instrumentation SP-10 standard (standard deviation: 8 mmHg(systole: 5.87 mmHg, diastole: 5.69 mmHg)). CONCLUSIONS: The results indicate that arterial blood pressure can be accurately measured and tracked noninvasively and continuously using the CareTaker system and the PDA algorithm. The results further support the physical model that all of the features of the pressure pulse envelope, whether in the central arteries or in the arterial periphery, can be explained by the interaction of the left ventricular ejection pressure pulse with two centrally located reflection sites.

Higher doses of erythropoietin-stimulating agents and hyporesponsiveness to their effects are associated with increased mortality among prevalent hemodialysis patients.

BACKGROUND: Attempts to achieve near-normal hemoglobin levels have been associated with higher mortality among chronic kidney disease patients. Evidence suggests a higher mortality rate for those with resistance to erythropoietin-stimulating agents (ESA). We investigated the association between responsiveness to ESA, dose of ESA and mortality in our hemodialysis population. METHODS: A retrospective cohort study of chronic hemodialysis patients receiving dialysis was conducted at the University of Virginia facilities. We collected data on patient demographics, comorbidities, dialysis vintage, vascular access type, body weight, ESA dose and hemoglobin, as well as data on known risk factors for ESA hyporesponsiveness. Vital status was determined 30 months later. The association between ESA responsiveness and mortality was investigated by using the Cox proportional hazard model adjusting for demographics, comorbidities, access type, dialysis adequacy, serum albumin, serum parathyroid hormone and ferritin concentrations. RESULTS: A total of 606 patients were included. The overall 30-month mortality was 35.8%. Compared to those in the lowest tertile of ESA hyporesponsiveness, patients in the middle and upper tertiles had significantly higher mortality (hazard ratio, HR: 1.64, 95% CI: 1.14-2.37, and HR: 2.08, 95% CI: 1.46-2.97, respectively). In the Cox proportional hazard model each unit increment in the ESA resistance index was associated with an HR of 2.27 (95% CI: 1.60-3.23) for mortality. In this model each 1-unit increment in ESA dose/kg or each 100-µg increment in absolute darbepoetin alfa dose were associated with a 9% increased risk of mortality (HR: 1.09, 95% CI: 1.04-1.13, and HR: 1.09, 95% CI: 1.03-1.15, respectively). CONCLUSIONS: Among prevalent hemodialysis patients, a higher degree of resistance to and higher doses of ESA are associated with increased mortality.