We examined the ability of different frequencies in sympathetic nerve activity (SNA) to induce oscillations in renal blood flow (RBF). In anesthetized rabbits the renal nerves were stimulated using modulated sine patterns (base frequency 5 Hz, 5-ms duration pulses) that varied in amplitude between 0 and 10 V at a frequency between 0.04 and 1.0 Hz. The strengths of the induced oscillations in RBF were calculated using spectral analysis. Although faster rhythms in simulated SNA >0.6 Hz contributed to the level of vascular tone, 95% of the power in the frequency response curve was below this frequency, indicating a low-pass filtering/integrating characteristic of the vasculature. Frequencies <0.6 Hz were associated with increasing ability to induce oscillations in RBF. The ability of an SNA rhythm at 0.6 Hz to induce a rhythm in RBF was 21 times less than that at 0.25 Hz. At 0.16 Hz there was a distinct peak in the frequency response curve, indicating the vasculature was more sensitive in this frequency band to sympathetic stimulation. Blockade of endogenous nitric oxide by N G-nitro-l-arginine methyl ester (l-NAME; 20 mg/kg) did not alter resting RBF levels nor was the low-pass filtering/integrating characteristic of the vasculature to nerve stimulation changed (i.e., the curve was not shifted left or right); however, there was a selective increase in the sensitivity to stimulation at 0.16 Hz, i.e., larger oscillations in RBF were evoked. These results indicate an ability of SNA to induce resonant oscillations in the renal vasculature and that there may be active and passive modulators of these responses. Naturally occurring oscillations in SNA <0.6 Hz are likely to contribute to the dynamic control of RBF, ensuring it responds rapidly and with high gain to the stimuli of daily life, while filtering out the faster oscillations ensures stable glomerular filtration.
Background: Textbook Outcome (TO) is a novel composite measure of clinical outcomes that can be used to measure the quality of surgical outcomes. TOs for pancreatic surgery were published by the Dutch Pancreatic Cancer Group (DPCG) in 2020. The aim of this study was to explore how a medium volume hepatopancreaticobiliary unit could use TO to benchmark local outcomes following pancreatic surgery. Methods: Retrospective analysis of prospectively collected data from patients who underwent pancreaticoduodenectomy (PD) or distal pancreatectomy (DP) for all indications between March 2005 and February 2020 at Christchurch Hospital (CH). Analysis of TO items as defined by the DPCG was performed and compared to nationwide Dutch outcomes (2014-2017), including cumulative analysis using CuSum. Results: In total, 273 patients were included (median age 63 years; 51% female) of which 182 (67%) underwent PD and 91 (33%) underwent DP (median annual volume 12 PDs/6 DPs). Overall, 58% of patients undergoing PD and 74% of patients undergoing DP achieved TO, compared with 58% and 67%, P = 0.944 and P = 0.231, respectively, for the Netherlands (median annual volume 33 PDs/8 DPs per hospital). Conclusions: TO offers a useful quality measure to benchmark local outcomes following pancreatic surgery against an external nationwide analysis. The results show that as a medium volume centre performance was comparable to previously published Dutch results, which included high volume centres. Applying CuSum methodology to the TO metric allows a continuous measure of performance. This offers the potential to provide feedback for quality improvement strategies.
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