Autonomic Nerve Activity and Blood Pressure in Ambulatory Dogs

Background The relationship between cardiac autonomic nerve activity and blood pressure (BP) changes in ambulatory dogs is unclear. Objective To test the hypotheses that simultaneous termination of stellate ganglion nerve activity (SGNA) and vagal nerve activity (VNA) predisposes to spontaneous orthostatic hypotension and that specific β2 adrenoceptor blockade prevents the hypotensive episodes. Methods We used a radiotransmitter to record SGNA, VNA and blood pressure (BP) in 8 ambulatory dogs. Video imaging was used to document postural changes. Results Out of these 8 dogs, 5 showed simultaneous sympathovagal discharges in which the minute by minute integrated SGNA correlated with integrated VNA in a linear pattern (“Group 1”). In these dogs abrupt termination of simultaneous SGNA-VNA at the time of postural changes (as documented by video imaging) was followed by abrupt (>20 mmHg over 4 beats) drops in BP. Dogs without simultaneous on/off firing (“Group 2”) did not have drastic drops in pressure. ICI 118,551 (ICI, a specific β2-blocker) infused at 3.1 µg/kg/hr for 7 days significantly increased BP from 126 (95% confidence interval, CI: 118 to 133) mmHg to 133 (95% CI 125 to141) mmHg (p=0.0001). The duration of hypotension (mean systolic BP < 100 mmHg) during baseline accounted for 7.1% of the recording. The percentage was reduced by ICI to 1.3% (p = 0.01). Conclusions Abrupt simultaneous termination of SGNA-VNA was observed at the time of orthostatic hypotension in ambulatory dogs. Selective β2 adrenoceptor blockade increased BP and reduced the duration of hypotension in this model

Perioperative Outcomes are Adversely Affected by Poor Pretransfer Adherence to Acute Limb Ischemia Practice Guidelines

Objectives The accepted treatment for acute limb ischemia (ALI) is immediate systemic anticoagulation and timely reperfusion to restore blood flow. In this study, we describe the retrospective assessment of pretransfer management decisions by referring hospitals to an academic tertiary care facility and its impact on perioperative adverse events. Methods A retrospective analysis of ALI patients transferred to us via our Level I Vascular Emergency program from 2010 to 2013 was performed. Patient demographics, comorbidities, Rutherford ischemia classification, time to anticoagulation, and time to reperfusion were tabulated and analyzed for correlation to incidence of major adverse limb events (MALE), mortality, and bypass patency in the perioperative period (30-day postoperative). All time intervals were calculated from the onset of symptoms and categorized into three subcohorts (48 hrs). Results Eighty-seven patients with an average age of 64.0 (± 16.2) years presented to outlying hospitals and was transferred to us with lower extremity ALI. The mean delay from symptom onset to initial referring physician evaluation was 18.3 hrs. At that time of evaluation, 53.8% had Rutherford class IIA ischemia and 36.3% had class IIB ischemia. Seventy-six (87.4%) patients were started on heparin previous to transfer. However, only 44 (57.9%) patients reached therapeutic levels as measured by activated partial thromboplastin time (aPTT) prior to definitive revascularization. A delay of anticoagulation initiation >48 hrs from symptom onset was associated with increased 30-day reintervention rates compared with the <6 hrs group (66.7% vs. 23.5%; p<0.05). However, time to reperfusion had no statistically significant impact on MALE, 30-day mortality, or 30-day interventional patency in our small cohorts. Additionally, patients with a previous revascularization had a higher 30-day reintervention rate (46.5%; p<0.05). Conclusions The practice of timely therapeutic anticoagulation of patients referred for ALI from community facilities occurs less frequently than expected and is associated with an increased perioperative reintervention rate

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Nanoelectrode Arrays for measuring Sympathetic Nervous Activity

This paper reports on the use of arrays of nanoelectrodes to measure activity of the Sympathetic Nervous System. Measurements of the Sympathetic Nervous Activity (SNA) have not been easy; primarily because of poor signal-to-noise ratio (SNR). We report improved SNR of SNA measurements achieved by the use of novel Planar Nanoelectrode Arrays (PNA). Nano scale features on the electrodes provide increased contact area with the host nerve reducing the limiting (Johnson) noise. These electrodes are fabricated using standard CMOS compatible fabrication techniques on a high resistivity silicon substrate and used to measure SNA in test animals. For comparison, traditional wire electrodes were used simultaneously to measure the same signal. The PNAs consistently exhibit significant improvement in the SNR of the measured SNA (35.71 dB vs. 25.08 dB for the wire electrode). Moreover, the PNAs are capable of recording events lost in the noise floor of the wire electrodes

Wireless Measurement of Sympathetic Nervous Activity using Planar Nanoelectrode Arrays

This paper reports on the use of arrays of nanoelectrodes as implantable sensors to wirelessly measure the activity of the Sympathetic Nervous System - Sympathetic Nervous Activity (SNA). SNA can be measured as a train of electrical pulses. Traditionally, SNA has been measured with wire electrodes. These measurements have not been easy because of poor signal-to-noise ratio (SNR). In the current work, we have successfully demonstrated improved SNR of SNA measurements achieved by the use of novel Planar Nanoelectrode Arrays (PNAs) in a chronic setting. The PNAs are placed on the left stellate ganglion (SG) via a thoracotomy. Nano scale features on the electrodes provide increased contact area with the nerve of interest (in this case the SG) thereby reducing the limiting (Johnson) noise. The PNAs were fabricated using standard CMOS compatible fabrication techniques on a high resistivity silicon substrate. After suitable wire-bonding and packaging, the PNAs were placed on the left stellate ganglion of a canine test subject. For adequate comparison, a standard set of wire electrodes were embedded on the same nerve in close proximity of the PNAs. Both the sensors were connected to a wireless transmitter (Model No. TR 70BB) powered with a rechargeable battery also placed within the canine test subject. The thoracotomy incision was repaired and the canine test subject allowed to recover before beginning SNA measurements. Our results showed that the PNAs consistently exhibit superior SNR of the measured SNA. Measurements have been successfully made up to three months after implantation of the electrodes and the SNR of the PNA has been consistently better than the wire electrodes. After one month the SNR of the PNA was 48.54 +/- 2.71 dB vs. 17.88 +/- 4.49 dB for the wire electrode (p \u3c 0.001). At three months the SNR of the PNA was 48.57 +/- 1.63 dB vs. 18.98 +/- 2.38 dB for the wire electrode (p \u3c 0.001)

Surgical Management of Chronic Mesenteric Venous Thrombosis: A Case Report

Although mesenteric venous thrombosis is an uncommon disease, it is a diagnostic dilemma and if left untreated results in significant morbidity and mortality. The clinical presentation of mesenteric venous thrombosis (MVT) is varied and depends on the etiology. Prompt recognition and treatment is important as this may limit the progression of thrombosis. Even though medical management is the current mainstay of therapy, there have been reported cases of clinical improvement with operative management. The authors describe an improved outcome following mesenteric-systemic shunting in a symptomatic patient with acute-on-chronic MVT affecting the proximal superior mesenteric vein

Evidence for nonoperative management of acute limb ischemia in infants

Acute limb ischemia (ALI) in infants is a catastrophic event. We performed a query of our database to determine those with ALI. Twelve patients were identified. The most frequent presentation was cyanotic limbs. Eleven patients were treated nonoperatively with anticoagulation. One patient was treated surgically with Fogarty balloon thrombectomy. There were three deaths all due to associated comorbidities. All had viable limbs on follow-up examination. There were three complications in the patients managed conservatively. Our recommendation for infants presenting with ALI is conservative observation with anticoagulation and intervention only for cases with tissue loss