head injury

Cerebrovascular Pressure Reactivity and Cerebral Oxygen Regulation After Severe Head Injury

Authors: Jaeger M, Lang EW.

BACKGROUND: To investigate the relationship between cerebrovascular pressure reactivity and cerebral oxygen regulation after head injury.
METHODS: Continuous monitoring of the partial pressure of brain tissue oxygen (PbrO2), mean arterial blood pressure (MAP), and intracranial pressure (ICP) in 11 patients. The cerebrovascular pressure reactivity index (PRx) was calculated as the moving correlation coefficient between MAP and ICP. For assessment of the cerebral oxygen regulation system a brain tissue oxygen response (TOR) was calculated, where the response of PbrO2 to an increase of the arterial oxygen through ventilation with 100 % oxygen for 15 min is tested. Arterial blood gas analysis was performed before and after changing ventilator settings.
RESULTS: Arterial oxygen increased from 108 ± 6 mmHg to 494 ± 68 mmHg during ventilation with 100 % oxygen. PbrO2 increased from 28 ± 7 mmHg to 78 ± 29 mmHg, resulting in a mean TOR of 0.48 ± 0.24. Mean PRx was 0.05 ± 0.22. The correlation between PRx and TOR was r = 0.69, P = 0.019. The correlation of PRx and TOR with the Glasgow outcome scale at 6 months was r = 0.47, P = 0.142; and r = -0.33, P = 0.32, respectively.
CONCLUSIONS: The results suggest a strong link between cerebrovascular pressure reactivity and the brain's ability to control for its extracellular oxygen content. Their simultaneous impairment indicates that their common actuating element for cerebral blood flow control, the cerebral resistance vessels, are equally impaired in their ability to regulate for MAP fluctuations and changes in brain oxygen.

Delayed Intracranial Hypertension and Cerebral Edema in Severe Pediatric Head Injury: Risk Factor Analysis

Authors: Bennett Colomer C, Solari Vergara F, Tapia Perez F, Miranda Vasquez F, Horlacher Kunstmann A, Parra Fierro G, Salazar Zenkovich C.

Introduction: Diffuse brain edema has been described as a major cause of intracranial hypertension (IH) following traumatic brain injury (TBI), and several studies suggest that it may be more frequent in children than in adults. While most cases of IH following TBI are present from the beginning, several studies have described a subgroup of patients with delayed elevations in intracranial pressure (ICP). Methods: Retrospective review of severe pediatric TBI cases admitted to a single institution during a 6-year period. Patients were classified into three groups, based on the temporal evolution of ICP: patients who evolved without IH, patients who had IH at admission and patients with delayed IH. A risk factor analysis was performed to find differences between these groups. Results: 31 cases of severe pediatric TBI were analyzed. 13 patients were female and 18 male, with an average age of 8.9 years. 4 patients met the described criteria for delayed IH; the only significant risk factor was presence of edema at the initial brain CT (p = 0.008). 3 additional patients presented clinical deterioration after 48 h and signs of brain edema in the CT, after ICP monitoring had been discontinued. Conclusions: Late-onset IH is a relatively common clinical condition in the pediatric population with severe TBI (present in 13% of the cases in our series), and the presence of a Marshall III CT scan at admission is a significant risk factor for this condition. Pediatric patients may benefit from a more prolonged period of ICP monitoring than adults, and the lack of amelioration of brain edema at follow-up brain CT (even with normal ICP values) may be an indication that more prolonged monitoring is needed.

Advances in the management of the critically injured patient in the operating room

Authors: Rock KC, Bakowitz M, McCunn M.

Care of trauma patients continues to improve through better understanding of optimal timing of operating room (OR) interventions, improved monitoring for patients with head injury and hemodynamic compromise, optimization of volume status, and use of appropriate vasoactive agents. Investigation of the pathophysiology of trauma patients as they progress to the chronic phase continues to advance interventions in the ICU and the OR. This article is an evidence-based update of anesthetic considerations for these patients, including management of intracranial pressure, cardiac monitoring, management of the damage control abdomen, fluid and hemodynamic management, and control of coagulopathies.

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