Circadian and Sex Differences After Acute High-Altitude Exposure: Are Early Acclimation Responses Improved by Blue Light?

OBJECTIVE: The possible effects of blue light during acute hypoxia and the circadian rhythm on several physiological and cognitive parameters were studied. METHODS: Fifty-seven volunteers were randomly assigned to 2 groups: nocturnal (2200-0230 hours) or diurnal (0900-1330 hours) and exposed to acute hypoxia (4000 m simulated altitude) in a hypobaric chamber. The participants were illuminated by blue LEDs or common artificial light on 2 different days. During each session, arterial oxygen saturation (Spo2), blood pressure, heart rate variability, and cognitive parameters were measured at sea level, after reaching the simulated altitude of 4000 m, and after 3 hours at this altitude. RESULTS: The circadian rhythm caused significant differences in blood pressure and heart rate variability. A 4% to 9% decrease in waking nocturnal Spo2 under acute hypoxia was observed. Acute hypoxia also induced a significant reduction (4%-8%) in systolic pressure, slightly more marked (up to 13%) under blue lighting. Women had significantly increased systolic (4%) and diastolic (12%) pressures under acute hypoxia at night compared with daytime pressure; this was not observed in men. Some tendencies toward better cognitive performance (d2 attention test) were seen under blue illumination, although when considered together with physiological parameters and reaction time, there was no conclusive favorable effect of blue light on cognitive fatigue suppression after 3 hours of acute hypobaric hypoxia. CONCLUSIONS: It remains to be seen whether longer exposure to blue light under hypobaric hypoxic conditions would induce favorable effects against fatigue.

Impact of non-neurological complications in severe traumatic brain injury outcome.

INTRODUCTION: Non-neurological complications in patients with severe traumatic brain injury (TBI) are frequent, worsening the prognosis, but the pathophysiology of systemic complications after TBI is unclear. The purpose of this study was to analyze non-neurological complications in patients with severe TBI admitted to the ICU, the impact of these complications on mortality, and their possible correlation with TBI severity. METHODS: An observational retrospective cohort study was conducted in one multidisciplinary ICU of a university hospital (35 beds); 224 consecutive adult patients with severe TBI (initial Glasgow Coma Scale (GCS) < 9) admitted to the ICU were included. Neurological and non-neurological variables were recorded. RESULTS: Sepsis occurred in 75% of patients, respiratory infections in 68%, hypotension in 44%, severe respiratory failure (arterial oxygen pressure/oxygen inspired fraction ratio (PaO2/FiO2) < 200) in 41% and acute kidney injury (AKI) in 8%. The multivariate analysis showed that Glasgow Outcome Score (GOS) at one year was independently associated with age, initial GCS 3 to 5, worst Traumatic Coma Data Bank (TCDB) first computed tomography (CT) scan and the presence of intracranial hypertension but not AKI. Hospital mortality was independently associated with initial GSC 3 to 5, worst TCDB first CT scan, the presence of intracranial hypertension and AKI. The presence of AKI regardless of GCS multiplied risk of death 6.17 times (95% confidence interval (CI): 1.37 to 27.78) (P < 0.02), while ICU hypotension increased the risk of death in patients with initial scores of 3 to 5 on the GCS 4.28 times (95% CI: 1.22 to 15.07) (P < 0.05). CONCLUSIONS: Low initial GCS, worst first CT scan, intracranial hypertension and AKI determined hospital mortality in severe TBI patients. Besides the direct effect of low GCS on mortality, this neurological condition also is associated with ICU hypotension which increases hospital mortality among patients with severe TBI. These findings add to previous studies that showed that non-neurological complications increase the length of stay and morbidity in the ICU but do not increase mortality, with the exception of AKI and hypotension in low GCS (3 to 5).

First CT findings and improvement in GOS and GOSE scores 6 and 12 months after severe traumatic brain injury.

PRIMARY OBJECTIVE: To analyse the association between individual initial computerized tomography (CT) scan characteristics and Glasgow Outcome Scale (GOS) and Extended Glasgow Outcome Scale (GOSE) improvement between 6 months and 1 year. METHODS AND PROCEDURES: Two hundred and twenty-four adult patients with severe traumatic brain injury and Glasgow Coma Scale (GCS) score of 8 or less who were admitted to an intensive care unit were studied. GOS and GOSE scores were obtained 6 and 12 months after injury in 203 subjects. Patients were predominantly male (84%) and median age was 35 years. MAIN OUTCOMES AND RESULTS: Traumatic Coma Data Bank (TCDB) CT classification was associated with GOS/GOSE improvement between 6 months and 1 year, with diffuse injury type I, type II and evacuated mass improving more than diffuse injury type III, type IV and non-evacuated mass; for GOS 43/155 (28%) vs 3/48 (6%) (chi(2) = 9.66, p < 0.01) and for GOSE 71/155 (46%) vs 7/48 (15%) (chi(2) = 15.1, p < 0.01). CT individual abnormalities were not associated with GOS/GOSE improvement, with the exception of subarachnoid haemorrhage, which showed a negative association with GOSE improvement (chi(2) = 4.08, p < 0.05). CONCLUSIONS: TCDB CT scan classification and subarachnoid haemorrhage were associated with GOS/GOSE improvement from 6-12 months, but individual CT abnormalities were not associated.

Improvement in GOS and GOSE scores 6 and 12 months after severe traumatic brain injury.

PRIMARY OBJECTIVE: To assess improvements in Glasgow Outcome Scale (GOS) and GOS extended (GOSE) scores between 6 months and 1 year following severe traumatic brain injury (TBI). METHODS AND PROCEDURES: One studied 214 adult patients with severe TBI with Glasgow Coma Scale (GCS) <9 admitted to Intensive Care Unit (ICU). GOS scores were obtained 6 and 12 months after injury in 195 subjects. Patients were predominantly male (84%) and median age was 35 years. MAIN OUTCOMES AND RESULTS: Outcome (GOS and GOSE at 6 months and 1 year) was better in the high GCS score at admission (6-8) group than in the low score group (3-5). The improvement in GOS scores between 6 months and 1 year was greater in the high GCS score at admission group than in the low score group. At 6 months, 75 patients had died and 120 survived. None died between the 6-12-month assessments; at 12 months, 36% had improved GOS score. CONCLUSIONS: GOS scores improved between 6-12 months after severe TBI in 36% of survivors and it is concluded that the expectancy of improvement is incomplete at 6 months. This improvement was greater in patients with better GCS scores (6-8) at admission than in those with worse GCS scores (3-5).