Autonomic modulation, spontaneous baroreflex sensitivity and fatigue in young men after COVID-19

Impaired autonomic modulation and baroreflex sensitivity (BRS) have been reported during and after COVID-19. Both impairments are associated with negative cardiovascular outcomes. If these impairments were to exist undetected in young men after COVID-19, they could lead to negative cardiovascular outcomes. Fatigue is associated with autonomic dysfunction during and after COVID-19. It is unclear if fatigue can be used as an indicator of impaired autonomic modulation and BRS after COVID-19. This study aims to compare parasympathetic modulation, sympathetic modulation, and BRS between young men who had COVID-19 versus controls and to determine if fatigue is associated with impaired autonomic modulation and BRS. Parasympathetic modulation as the high-frequency power of R-R intervals (lnHFR-R), sympathetic modulation as the low-frequency power of systolic blood pressure variability (LFSBP), and BRS as the -index were measured by power spectral density analysis. These variables were compared between 20 young men who had COVID-19 and 24 controls. Independent t-tests and Mann-Whitney U tests indicated no significant difference between the COVID-19 and the control group in: lnHFR-R, P=0.20; LFSBP, P=0.11, and -index, P=0.20. Fatigue was not associated with impaired autonomic modulation or BRS. There is no difference in autonomic modulations or BRS between young men who had COVID-19 compared to controls. Fatigue did not seem to be associated with impaired autonomic modulation or impaired BRS in young men after COVID-19. Findings suggest that young men might not be at increased cardiovascular risk from COVID-19-related dysautonomia and impaired BRS.

Care and cleaning of the endoscope

The purchase of veterinary endoscopy equipment requires a large investment on the part of the hospital. To ensure good return on the investment as well as to provide adequate service to clients, the equipment should be properly maintained. Close attention to this detail enables the practitioner to extend the life of the endoscope and its accessory instruments.

Inhaled nitric oxide delivery by anesthesia machines

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used to treat intraoperative pulmonary hypertension and hypoxemia. In contrast to NO delivered by critical care ventilators, NO delivered by anesthesia machines can be complicated by rebreathing. We evaluated two methods of administering NO intraoperatively: via the nitrous oxide (N(2)O) flowmeter and via the INOvent (Datex-Ohmeda, Madison, WI). We hypothesized that both systems would deliver NO accurately when the fresh gas flow (FGF) rate was higher than the minute ventilation (VE). Each system was set to deliver NO to a lung model. Rebreathing of NO was obtained by decreasing FGF and by simulating partial NO uptake by the lung. At FGF > or = VE (6 L/min), both systems delivered an inspired NO concentration ([NO]) within approximately 10% of the [NO] set. At FGF < VE and complete NO uptake, the N(2)O flowmeter delivered a lower [NO] (70 and 40% of the [NO] set at 4 and 2 L/min, respectively) and the INOvent delivered a higher [NO] (10 and 23% higher than the [NO] set at 4 and 2 L/min, respectively). Decreasing the NO uptake increased the inspired [NO] similarly with both systems. At 4 L/min FGF, [NO] increased by 10%-20% with 60% uptake and by 18%-23% with 30% uptake. At 2 L/min, [NO] increased by 30%-33% with 60% uptake and by 60%-69% with 30% uptake. We conclude that intraoperative NO inhalation is accurate when administered either by the N(2)O flowmeter of an anesthesia machine or by the INOvent when FGF > or = VE.

IMPLICATIONS

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In a lung model, we demonstrated that NO can be delivered accurately by a N(2)O flowmeter or by a commercial device. We provide guidelines for intraoperative NO delivery.

Effect of angiotensin converting enzyme inhibition on the Doppler waveform in dogs with renal artery stenosis

Our objective was to investigate whether the angiotensin converting enzyme inhibitor enalaprilat improves detection of hemodynamically significant renal artery stenoses in dogs. Renal artery stenoses of 50 to 99% were surgically created unilaterally in five dogs. Doppler ultrasonographic evaluation was performed at baseline (no stenosis), after creation of the stenosis, and after the administration of enalaprilat. The resistive index increased in the nonstenotic kidney (P < 0.01) but not in the stenotic kidney after administration of enalaprilat. The difference in resistive indices between nonstenotic and stenotic kidneys increased significantly (P < 0.05) after administration of enalaprilat. Measurement of the resistive index after administration of an angiotensin converting enzyme inhibitor in humans may improve the performance of Doppler ultrasonography in detecting hemodynamically significant renal artery stenoses.

Effect of iodine deficiency and cold exposure on thyroxine 5'-deiodinase activity in various rat tissues

We measured thyroxine 5'-deiodinase I (T(4)5'D-I) activity in thyroid, liver, and kidney and thyroxine 5'-deiodinase II (T(4)5'D-II) activity in brown adipose tissue (BAT) in rats on a low-iodine diet (LID) to test the possibility that increased deiodinase activity in these tissues might contribute to the maintenance of ther serum 3,5,3'-triiodothyronine (T3) level. Control rats received LID plus KI. Experiments were also performed with LID and LID plus KI rats exposed to cold. T(4)5'D-I activity was greatly increased in the thyroids of LID rats but not in liver or kidney. We consider it likely that increased thyroxine (T4)-to-T3 conversion in the greatly enlarged thyroids of LID rats contributed to the maintenance of serum T3. T(4)5'D-II activity in BAT was markedly increased in LID rats and was further greatly increased on cold exposure. However, we were unable to demonstrate an increase in uncoupling protein mRNA levels in BAT in response to cold in LID rats. We attribute this to the very low serum T4 level, which limits substrate availability. This factor also makes it unlikely that BAT contributes to maintenance of serum T3 in LID rats.

Atrial and ventricular arrhythmias in asymptomatic active elderly subjects: correlation with left atrial size and left ventricular mass

Elderly normal subjects have an increased prevalence of cardiac arrhythmias compared with young and middle-aged subjects. The objective of this study was to test the hypothesis that the incidence and complexity of atrial and ventricular arrhythmias may be related to either left atrial enlargement or to increased left ventricular mass, respectively. From 146 asymptomatic volunteers older than 60 years, 86 subjects were considered to be free of cardiovascular abnormalities and had adequate M-mode echocardiograms and 24-hour ambulatory electrocardiograms. The mean age was 72 +/- 7 years, with a range of 60 to 96 years. There were 37 men and 49 women. During 1415 +/- 73 minutes of ambulatory electrocardiography, the average heart rate was 72 +/- 8 beats/min in men and 76 +/- 6 beats/min in women (p less than 0.05). Atrial arrhythmias were present in 64 subjects (74%); the frequency and complexity of these arrhythmias correlated with left atrial size (p less than 0.01). Ventricular arrhythmias were present in 55 subjects (64%); the frequency and complexity of ventricular arrhythmias did not correlate with left ventricular mass index. These results suggest that left atrial dilatation, a normal development in healthy elderly subjects, plays a significant role in the pathophysiology of the increased incidence of atrial arrhythmias. Increased left ventricular mass, which also occurs normally in the aging heart, is not, on the other hand, associated with an increased frequency and/or complexity of ventricular arrhythmias.

Isolation of an antigenically "null" cell line from pig peripheral blood mononuclear cells

A new pig cell line (A4) isolated from a primary culture of pig peripheral blood mononuclear cells was characterized. A4 was demonstrated to be morphologically, antigenically and functionally distinct from the more commonly isolated pig lymphoblastoid B cell lines (e.g. P-SC). When the A4 cell line and clones derived from it were tested against a panel of monoclonal antibodies, which define specific subpopulations of pig mononuclear cells, little or no reactivity was observed. The A4 cell line, unlike the P-SC cell line, was unable to induce a mixed lymphocyte reaction. The amount of immunoglobulin secreted by A4 cells as detected by an ELISA was reduced compared to that produced by P-SC cells. The P-SC cell lines produced an IL-1-like factor, whereas no IL-1-like activity was found in the A4 supernatant. The A4 cell line appeared to be a null cell in respect to the P-SC cell line properties; only the slight amount of immunoglobulin produced suggested that the A4 cell line is of the B cell lineage. An association of viral particles with cells of the A4 morphology and null antigenic characteristics was observed and may provide an explanation for the reduced B cell properties of A4 cells.

Left ventricular diastolic function in a population of healthy elderly subjects. An echocardiographic study

Diastolic left ventricular function was comparatively assessed in 19 healthy elderly individuals (mean age 71 years) and in 20 young normal subjects (mean age 26 years), using digitized echocardiograms. Peak and average filling rates were slower in the group of elderly subjects than in the younger population (128 +/- 26 and 75 +/- 11 v 182 +/- 37 and 92 +/- 17 mm per second, respectively, P less than .001). The duration of the rapid filling phase and the time to peak filling rate were significantly longer in the older than in the younger population (207 +/- 39 and 125 +/- 21 v 174 +/- 38 and 90 +/- 26 ms, respectively, P less than .01). The atrial contribution to total ventricular filling was 18 +/- 6% in the elderly and 10 +/- 3% in the young (P less than .001). The group differences of most of these measurements of diastolic function retained statistical significance after correction for heart rate. Measurements of left ventricular systolic function were similar in both age groups. The authors conclude that aging is associated with a decline of left ventricular compliance, unrelated to heart rate or systolic performance. The contribution of atrial contraction to ventricular filling is quantitatively larger in elderly individuals.

Effect of propranolol (inderal) on exercise tolerance in angina pectoris

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