Impact of Head-of-Bed Posture on Brain Oxygenation in Patients with Acute Brain Injury: A Prospective Cohort Study.

BACKGROUND: Therapeutic head positioning plays a role in the management of patients with acute brain injury. Although intracranial pressure (ICP) is typically lower in an upright posture than in a flat position, limited data exist concerning the effect of upright positioning on brain oxygenation and circulation. We sought to determine the impact of supine (0°) and semirecumbent (15° and 30°) postures on ICP, brain oxygenation, and brain circulation. METHODS: An observational cohort study was conducted between February 2012 and September 2015. Twenty-three patients with severe acute brain injury were successively observed at head elevations of 30°, 15°, and 0°. Postural-induced changes in ICP, cerebral perfusion pressure, brain tissue oxygenation pressure, and transcranial Doppler findings were simultaneously measured during three repeated experiments: 24 h after admission to the intensive care unit (exp1), 24 h later (exp2), and 96 h later (exp3). Cerebral perfusion pressure, arterial blood gases, hemoglobin content, and body temperature remained unchanged during the three experiments. RESULTS: Using linear random-slope mixed models, we found that during the early phase of acute brain injury (exp1), lowering the head posture from 30° to 15°, and then to 0°, was associated with a gradual mean ICP increase of 2.6 mm Hg (1.4-3.7 mm Hg; P < 0.001); and from 30° to 0°, an increase of 7.4 mm Hg (6.3-8.6 mm Hg; P < 0.001). Furthermore, brain tissue oxygenation pressure and mean blood flow velocity improved when the head posture was lowered from 30° to 0° by 1.2 mm Hg (0.2-2.3 mm Hg) and 4.1 cm/s (0.0-8.2 cm/s), respectively (both P < 0.05). CONCLUSIONS: Changing the positioning of stable patients with acute brain injury resulted in opposite changes of ICP versus brain oxygenation and circulation. This information supports the concept of an individualized approach to head positioning that is based on the multimodal monitoring of brain parameters.

Reliability of standardized ultrasound measurements of quadriceps muscle thickness in neurological critically ill patients: a comparison to computed tomography measures.

OBJECTIVE: Muscle atrophy is frequent in critically ill patients and is associated with increased mortality and long-lasting alteration in quality of life. Muscle ultrasound has not been clearly validated in intensive care unit patients. The aim of this study was to compare the level of agreement between ultrasound and computed tomography scan for the measurement of quadriceps muscle thickness. DESIGN: A prospective observational study. PATIENTS: Forty-two consecutive patients admitted to a neurological intensive care unit. METHODS: Quadriceps thickness was measured 15 cm above the upper edge of the patella. Iterative brain computed tomography scans were associated with a quadriceps-centred acquisition sequence. Concomitantly, an ultrasound of the quadriceps was performed. The position of the studied leg was standardized for ultrasound and computed tomography. RESULTS: A total of 73 measurements of ultrasound and computed tomography quadriceps thickness were compared. The correlation between both measures was 0.93 (95% confidence interval (95% CI) 0.84-1.02). Intra-rater reliability of ultrasound measurements and inter-rater reliability were excellent, with an ICC of 0.98 (95% CI 0.97-0.99) and 0.96 (95% CI 0.92-0.98), respectively. CONCLUSION: A specific ultrasound set-up for measurement of quadriceps thickness is reliable and reproducible in an intensive care unit population.

Transcranial Color Duplex Ultrasound: A Reliable Tool for Cerebral Hemodynamic Assessment in Brain Injuries.

BACKGROUND: Transcranial color duplex ultrasound (TCCD) is becoming an important tool for cerebral monitoring of brain-injured patients. To date, TCCD reproducibility has been studied in healthy volunteers or patients with subarachnoid hemorrhage and its efficiency in many brain injuries has not been proved. Our aim was to evaluate TCCD interobserver agreement in different brain injuries. PATIENTS AND METHODS: We performed a prospective monocentric trial conducted from January 2014 to September 2014 in intensive care unit (ICU) of Saint-Etienne university teaching hospital, France.Brain-damaged patients admitted in ICU were included, excluding those with decompressive craniectomy. Two randomized operators among the ICU medical staff consecutively performed measurements of cerebral blood flow velocities with TCCD. RESULTS: One hundred measurements were obtained from 42 patients. Hemodynamic and end-tidal CO2 pressure were similar between both measurement set. The results obtained with the Bland-Altman method showed bias at 0.52 (95% confidence interval [CI], -4.19 to 3.16), 0.53 (95% CI, -1.86 to 2.92), and 0.002 (95% CI, -0.06 to 0.06) for mean velocity, diastolic velocity, and pulsatility index, respectively. The limits of agreement were (-32.4; 31.4), (-20.4; 21.4), (-0.5; 0.5) for mean velocity, diastolic velocity, and pulsatility index, respectively. The Passing and Bablok regression have shown a quasilinear relationship between measurements. CONCLUSIONS: We reported the reliability of TCCD interobserver agreement in brain-damaged patients.