Prospective association between hypotension and idiopathic chronic fatigue

Autonomic dysreflexia: a cardiovascular disorder following spinal cord injury

Autonomic dysreflexia (AD) is a serious cardiovascular disorder in patients with spinal cord injury (SCI). The primary underlying cause of AD is loss of supraspinal control over sympathetic preganglionic neurons (SPNs) caudal to the injury, which renders the SPNs hyper-responsive to stimulation. Central maladaptive plasticity, including C-fiber sprouting and propriospinal fiber proliferation exaggerates noxious afferent transmission to the SPNs, causing them to release massive sympathetic discharges that result in severe hypertensive episodes. In parallel, upregulated peripheral vascular sensitivity following SCI exacerbates the hypertensive response by augmenting gastric and pelvic vasoconstriction. Currently, the majority of clinically employed treatments for AD involve anti-hypertensive medications and Botox injections to the bladder. Although these approaches mitigate the severity of AD, they only yield transient effects and target the effector organs, rather than addressing the primary issue of central sympathetic dysregulation. As such, strategies that aim to restore supraspinal reinnervation of SPNs to improve cardiovascular sympathetic regulation are likely more effective for AD. Recent pre-clinical investigations show that cell transplantation therapy is efficacious in reestablishing spinal sympathetic connections and improving hemodynamic performance, which holds promise as a potential therapeutic approach.

Hypotension and environmental noise: a replication study

Up to now, traffic noise effect studies focused on hypertension as health outcome. Hypotension has not been considered as a potential health outcome although in experiments some people also responded to noise with decreases of blood pressure. Currently, the characteristics of these persons are not known and whether this down regulation of blood pressure is an experimental artifact, selection, or can also be observed in population studies is unanswered. In a cross-sectional replication study, we randomly sampled participants (age 20–75, N = 807) from circular areas (radius = 500 m) around 31 noise measurement sites from four noise exposure strata (35–44, 45–54, 55–64, >64 Leq, dBA). Repeated blood pressure measurements were available for a smaller sample (N = 570). Standardized information on socio-demographics, housing, life style and health was obtained by door to door visits including anthropometric measurements. Noise and air pollution exposure was assigned by GIS based on both calculation and measurements. Reported hypotension or hypotension medication past year was the main outcome studied. Exposure-effect relationships were modeled with multiple non-linear logistic regression techniques using separate noise estimations for total, highway and rail exposure. Reported hypotension was significantly associated with rail and total noise exposure and strongly modified by weather sensitivity. Reported hypotension medication showed associations of similar size with rail and total noise exposure without effect modification by weather sensitivity. The size of the associations in the smaller sample with BMI as additional covariate was similar. Other important cofactors (sex, age, BMI, health) and moderators (weather sensitivity, adjacent main roads and associated annoyance) need to be considered as indispensible part of the observed relationship. This study confirms a potential new noise effect pathway and discusses potential patho-physiological routes of actions.

Hemodynamic and autonomic modifications during sleep stages in young hypotensive women

This study examined cardiovascular activity and autonomic involvement during sleep in essential hypotension. We compared young female hypotensives and normotensives using ambulatory blood pressure monitoring, impedance cardiography, and frequency-domain analysis of heart rate variability during a night of polysomnographic recording. Hypotensives, as compared to normotensives, exhibited lower blood pressure, reduced myocardial contractility and reduced sympathovagal balance across the whole night. Both groups exhibited a reduction in cardiovascular involvement from wake to sleep with similar cardiovascular activity during wake and REM. No group difference was observed in sleep architecture suggesting similar sleeping quality in hypotensives and normotensives. The lower blood pressure and reduced myocardial contractility associated with a lower sympathovagal balance in hypotensives, as compared to normotensives, suggest a night-time hypoactivation of the cardiovascular system supporting the hypothesis of impairment in autonomic control in essential hypotension.

No prospective association between hypotension and idiopathic fatigue

OBJECTIVE

To test the hypothesis that there is a prospective association between constitutional hypotension and new-onset fatigue in a large, representative sample.

METHODS

In this prospective study using a large population-based cohort dataset, the Health and Lifestyle Survey, a representative sample of the population residing in private dwellings in Great Britain in 1984 (n=9003, ages 18-97 years) had their blood pressure measured and were asked about fatigue. Participants reporting fatigue at baseline were excluded. The outcome was fatigue state in 1991.

RESULTS

No association was shown, unadjusted or adjusted for likely confounders, in the healthy young population [systolic BP: adj. OR (95% CIs)=1.25 (0.90-1.74); diastolic BP: 1.18 (0.84-1.65)] or the whole population [systolic BP: 0.98 (0.77-1.26); diastolic BP: 1.01 (0.79-1.26)].

CONCLUSION

In this British population-based study, hypotension was not a risk factor for incident idiopathic fatigue.

Orthostatic intolerance in survivors of childhood cancer

PURPOSE

To compare the prevalence and severity of orthostatic intolerance in survivors of childhood cancer and in healthy controls, and to correlate results of self-reported measures of health status with orthostatic testing in survivors of childhood cancer.

PATIENT AND METHODS

Thirty-nine survivors of childhood cancer and 56 controls were recruited for this study. Each cancer survivor completed standardised self-report measures and all participants underwent a standing test (5 min supine, 10 min of motionless standing leaning against a wall, followed by another 2 min supine). The main outcomes of the standing test were orthostatic tachycardia (OT), defined as a heart rate increase of at least 30 beats per minute (bpm) during standing, and neurally mediated hypotension (NMH), defined as a drop in systolic blood pressure of at least 25 mmHg.

RESULTS

OT developed in 22/39 (56%) cancer survivors versus 17/56 (30%) controls (P=.01). Cancer survivors had a higher baseline and maximum standing heart rate (both P<.001) and a more rapid onset of significant OT (P=.005). No significant difference in scores on self-report measures was found between cancer survivors with or without OT.

CONCLUSION

This study provides preliminary evidence of a higher rate of orthostatic intolerance in childhood cancer survivors. Further study is warranted to better define whether this is a modifiable risk factor for fatigue in this population, and how orthostatic intolerance interacts with other known risk factors for lowered quality of life.

Association of low blood pressure with anxiety and depression: the Nord-Trøndelag Health Study

BACKGROUND

Low blood pressure has mainly been regarded as ideal, but recent studies have indicated an association with depression in elderly people.

OBJECTIVE

To investigate whether low blood pressure is associated with anxiety and depression in the general population.

DESIGN

Cross-sectional study.

SETTING

Participants in the population-based Nord-Trøndelag Health Study (HUNT-2, 1995-7), Norway.

PARTICIPANTS

60,799 men and women aged 20-89 years filled in the Hospital Anxiety and Depression Scale as part of a general health study. Systolic and diastolic blood pressure was classified in age-stratified and sex-stratified centile groups.

MAIN RESULTS

Compared with participants with systolic blood pressure within the 41-60 centile (reference) group, the odds ratio for anxiety was 1.31 (95% confidence intervals (CI) 1.16 to 1.49), for depression 1.22 (95% CI 1.03 to 1.46), and for comorbid anxiety and depression 1.44 (95% CI 1.24 to 1.68) in the group with < or =5 centile systolic blood pressure. Slightly weaker associations were found of low diastolic blood pressure with anxiety and depression. These associations were similar across sex and age groups. Physical impairment, smoking and angina pectoris influenced the associations only marginally, whereas stroke, myocardial infarction, use of drugs for hypertension, body mass index and several other covariates had no influence.

CONCLUSIONS

This study represents epidemiological evidence for an association of low blood pressure with anxiety and depression, which is not caused by cardiovascular disease.

Effects of arterial hypotension on microvascular oxygen exchange in contracting skeletal muscle

In healthy animals under normotensive conditions (N), contracting skeletal muscle perfusion is regulated to maintain microvascular O2 pressures (Pmv[Formula: see text]) at levels commensurate with O2 demands. Hypovolemic hypotension (H) impairs muscle contractile function; we tested whether this condition would alter the matching of O2 delivery (Q̇o2) to O2 utilization (V̇o2), as determined by Pmv[Formula: see text] at the onset ofmuscle contractions. Pmv[Formula: see text] in the spinotrapezius muscles of seven female Sprague-Dawley rats (280 ± 6 g) was measured every 2 s across the transition from rest to 1-Hz twitch contractions. Measurements were made under N (mean arterial pressure, 97 ± 4 mmHg) and H (induced by arterial section; mean arterial pressure, 58 ± 3 mmHg, P < 0.05) conditions; Pmv[Formula: see text] profiles were modeled using a multicomponent exponential fitted with independent time delays. Hypotension reduced muscle blood flow at rest (24 ± 8 vs. 6 ± 1 ml−1·min−1·100 g−1 for N and H, respectively; P < 0.05) and during contractions (74 ± 20 vs. 22 ± 4 ml−1·min−1·100 g−1 for N and H, respectively; P < 0.05). H significantly decreased resting Pmv[Formula: see text] and steady-state contracting Pmv[Formula: see text](19.4 ± 2.4 vs. 8.7 ± 1.6 Torr for N and H, respectively, P < 0.05). At the onset of contractions, H reduced the time delay (11.8 ± 1.7 vs. 5.9 ± 0.9 s for N andH, respectively, P < 0.05) before the fall in Pmv[Formula: see text] and accelerated therate of Pmv[Formula: see text] decrease (time constant, 12.6 ± 1.4 vs. 7.3 ± 0.9 s for N and H, respectively, P < 0.05). Muscle V̇o2 was reduced by 71% at rest and 64% with contractions in H vs. N, and O2 extraction during H averaged 78% at rest and 94% during contractions vs. 51 and 78% in N. These results demonstrate that H constrains the increase of skeletal muscle Q̇o2 relative to that of V̇o2 at the onset of contractions,leading to a decreased Pmv[Formula: see text]. According to Fick's law, this scenario will decrease blood-myocyte O2 flux, thereby slowing V̇o2 kinetics and exacerbating the O2 deficit generated at exercise onset.