Readaptation from simulated microgravity as a stimulus for improved orthostatic tolerance: role of the renal, cardioendocrine, and cardiovascular systems

Statistical analysis plan: Early mobilization by head-up tilt with stepping versus standard care after severe traumatic brain injury

Background

Early mobilization on a tilt table with stepping versus standard care may be beneficial for patients with severe brain injury, but data from randomized clinical trials are lacking. This detailed statistical analysis plan describes the analyses of data collected in a randomized clinical feasibility trial for early mobilization by head-up tilt with stepping versus standard care after severe traumatic brain injury.

Methods

Primary feasibility outcomes are the proportion of included participants who were randomized out of all screened patients; the proportion of participants allocated to the experimental intervention who received at least 60% of the planned exercise sessions; and safety outcomes such as adverse events and reactions and serious adverse events and reactions. Exploratory clinical outcomes are suspected unexpected serious adverse reactions; and functional outcomes as assessed by the Coma Recovery Scale-Revised at four weeks; Early Functional Ability Scale and Functional Independence Measure at three months. The description includes the statistical analysis plan, including the use of multiple imputations and Trial Sequential Analysis.

Intravenous saline administration in patients with severe acquired brain injury and orthostatic intolerance for tilt-table mobilization

PRIMARY OBJECTIVE

This study aimed to investigate the effect of intravenous saline administration on orthostatic hypotension (OH) during head up tilt (HUT) and the change in the renin-angiotensin-aldosterone system before and after HUT in patients with severe acquired brain injury (ABI).

RESEARCH DESIGN

The study is designed as an observational study.

METHODS AND PROCEDURES

Fourteen patients with ABI, low level of consciousness and OH were monitored before, during and after HUT with non-invasive beat-to-beat blood pressure measurement, and transcranial Doppler determination of middle cerebral artery blood flow velocity. Blood samples were collected before and after two HUT sessions separated by 1 hour and saline was administered in between.

MAIN OUTCOMES AND RESULTS

Patients' ability to stand upright did not change after saline administration due to OH. The patients showed signs of reduced cerebral autoregulation at both HUT sessions. The patients had a significant lower level of renin and angiotensin II but not aldosterone.

CONCLUSIONS

Patients with severe ABI and OH demonstrate no improvement in standing time with reduced plasma renin and angiotensin II after two HUT sessions and 1 hour fluid administration. Research focusing on the ability to retain fluid after bed rest is warranted.

Transcutaneous electrical acupuncture stimulation as a countermeasure against cardiovascular deconditioning during 4 days of head-down bed rest in humans

OBJECTIVE

Spaceflight is associated with cardiovascular deregulation. However, the influence of microgravity on the cardiovascular system and its mechanisms and countermeasures remain unknown. Our previous studies have demonstrated that transcutaneous electrical acupuncture stimulation (TEAS) is effective in improving orthostatic tolerance (OT). The purpose of this study was to determine if TEAS treatment can attenuate cardiovascular deconditioning induced by a 4-day -6° head-down bed rest (HDBR).

METHODS

Fourteen healthy male subjects were randomly allocated to a control group (control, n=6, 4 days HDBR without countermeasures) and a TEAS treatment group (TEAS, n=8, 4 days HDBR with TEAS at Neiguan (PC6) for 30 min each day for 4 consecutive days during HDBR). OT, plasma hormones, plasma volume and heart rate variability were assessed before and after HDBR. Cardiac function and cerebral blood flow were measured before, during and after HDBR.

RESULTS

The data showed that TEAS treatment mitigated the decrease in OT that was observed in the control group and cardiac function, alleviated autonomic dysfunction, and partially prevented plasma volume reduction after HDBR. Angiotensin II and aldosterone were significantly increased by 129.3% and 133.3% after HDBR in the TEAS group (p<0.05).

CONCLUSIONS

These results indicate that 30 min of daily TEAS treatment at PC6 is partially effective in maintaining OT, probably due to increased plasma volume-regulating hormones and activation of the peripheral sympathetic nervous system. TEAS treatment appears effective at reducing cardiovascular deconditioning induced by HDBR for 4 days.

TRIAL REGISTRATION NUMBER

NCT02300207.

Short-term physical inactivity impairs vascular function

BACKGROUND

Sedentarism, also termed physical inactivity, is an independent risk factor for cardiovascular diseases. Mechanisms thought to be involved include insulin resistance, dyslipidemia, hypertension, and increased inflammation. It is unknown whether changes in vascular and endothelial function also contribute to this excess risk. We hypothesized that short-term exposure to inactivity would lead to endothelial dysfunction, arterial stiffening, and increased vascular inflammation.

METHODS

Five healthy subjects (four men and one woman) underwent 5 d of bed rest (BR) to simulate inactivity. Measurements of vascular function (flow-mediated vasodilation to evaluate endothelial function; applanation tonometry to assess arterial resistance), inflammation, and metabolism were made before BR, daily during BR, and 2 d after BR recovery period. Subjects maintained an isocaloric diet throughout.

RESULTS

BR led to significant decreases in brachial artery and femoral artery flow-mediated vasodilation (brachial: 11 ± 3% pre-BR versus 9 ± 2% end-BR, P = 0.04; femoral: 4 ± 1% versus 2 ± 1%, P = 0.04). The central augmentation index increased with BR (-4 ± 9% versus 5 ± 11%, P = 0.03). Diastolic blood pressure increased (58 ± 7 mm Hg versus 62 ± 7 mm Hg, P = 0.02), whereas neither systolic blood pressure nor heart rate changed. 15-Hydroxyeicosatetraenoic acid, an arachidonic acid metabolite, increased but the other inflammatory and metabolic biomarkers were unchanged.

CONCLUSIONS

Our findings show that acute exposure to sedentarism results in decreased endothelial function, arterial stiffening, increased diastolic blood pressure, and an increase in 15-hydroxyeicosatetraenoic acid. We speculate that inactivity promotes a vascular "deconditioning" state characterized by impaired endothelial function, leading to arterial stiffness and increased arterial tone. Although physiologically significant, the underlying mechanisms and clinical relevance of these findings need to be further explored.

Étude préliminaire de la désadaptation cardiorespiratoire après une ligamentoplastie de genou chez le sportif

AIM

The aim of this study was to analyze changes in cardiorespiratory fitness of athletes who had surgery following a lesion of the anterior cruciate ligament of the knee.

METHODS

Two groups of 12 athletes at the regional level underwent surgical repair to rebuild the external anterior crossed ligament of the knee (central third bone patellar tendon bone autograft and doubled semitendinosus/doubled gracilis autograft techniques). All subjects were evaluated before and after surgery within 7 days: the first group underwent maximal incremental tests with the upper limbs, and the second group measurement of resting cardiac volumes.

RESULTS

Surgery followed by a few days of confinement generated a quick and significant reduction in the maximal oxygen consumption (-7%, P<0.05) and peak aerobic power (-8%, P<0.05). End diastolic volume and stroke volume were reduced, by 23% and 27% respectively (P<0.05). A significant reduction of ejection fraction was also observed (P<0.05). The mean left ventricular ejection fraction was 65% before the surgery 60% after 7 days' of hospitalization.

CONCLUSION

In sportsmen, 7 days of hospitalization due to surgery of the knee led to resting cardiac unsuitability characterized by a significant reduction in the stroke volume. These elements could involve decreased aerobic fitness and should encourage the hospital practitioner to propose a program of aerobic training in addition to conventional rehabilitation.