Impact of intracranial pressure monitoring on mortality in patients with traumatic brain injury: a systematic review and meta-analysis

Authors: Yuan Q, Wu X, Sun Y, Yu J, Li Z, Du Z, Mao Y, Zhou L, Hu J.

OBJECT Some studies have demonstrated that intracranial pressure (ICP) monitoring reduces the mortality of traumatic brain injury (TBI). But other studies have shown that ICP monitoring is associated with increased mortality. Thus, the authors performed a meta-analysis of studies comparing ICP monitoring with no ICP monitoring in patients who have suffered a TBI to determine if differences exist between these strategies with respect to mortality, intensive care unit (ICU) length of stay (LOS), and hospital LOS. METHODS The authors systematically searched MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (Central) from their inception to October 2013 for relevant studies. Randomized clinical trials and prospective cohort, retrospective observational cohort, and case-control studies that compared ICP monitoring with no ICP monitoring for the treatment of TBI were included in the analysis. Studies included had to report at least one point of mortality in an ICP monitoring group and a no-ICP monitoring group. Data were extracted for study characteristics, patient demographics, baseline characteristics, treatment details, and study outcomes. RESULTS A total of 14 studies including 24,792 patients were analyzed. The meta-analysis provides no evidence that ICP monitoring decreased the risk of death (pooled OR 0.93 , p = 0.40). However, 7 of the studies including 12,944 patients were published after 2012 (January 2012 to October 2013), and they revealed that ICP monitoring was significantly associated with a greater decrease in mortality than no ICP monitoring (pooled OR 0.56 , p = 0.0006). In addition, 7 of the studies conducted in North America showed no evidence that ICP monitoring decreased the risk of death, similar to the studies conducted in other regions. ICU LOSs were significantly longer for the group subjected to ICP monitoring (mean difference 0.29 ; p < 0.00001). In the pooled data, the hospital LOS with ICP monitoring was also significantly longer than with no ICP monitoring (MD 0.21 ; p = 0.01). CONCLUSIONS In this systematic review and meta-analysis of ICP monitoring studies, the authors found that the current clinical evidence does not indicate that ICP monitoring overall is significantly superior to no ICP monitoring in terms of the mortality of TBI patients. However, studies published after 2012 indicated a lower mortality in patients who underwent ICP monitoring.

Intracranial hypertension associated with obstructive sleep apnea: A discussion of potential etiologic factors

Authors: Wardly DE.

Obstructive sleep apnea has been shown to increase intracranial pressure, and to be a secondary cause of intracranial hypertension. There are a few theories that attempt to explain this relationship, however there is little data, and even less recognition among physicians that this actually occurs. This paper discusses multiple pieces of data, from anatomical correlates to biochemical information involving neuro-excitotoxicity, as well as hematologic factors and issues surrounding brain edema and blood-brain barrier dysfunction. A complex paradigm for how obstructive sleep apnea may lead to increased intracranial pressure is thus proposed. In addition, suggestions are made for how obstructive sleep apnea must as a result be managed differently in the setting of idiopathic intracranial hypertension.

Intraoperative secondary insults during extracranial surgery in children with traumatic brain injury

Authors: Fujita Y, Algarra NN, Vavilala MS, Prathep S, Prapruettham S, Sharma D.

PURPOSE: Data on intraoperative secondary insults in pediatric traumatic brain injury (TBI) are limited.
METHODS: We examined intraoperative secondary insults during extracranial surgery in children with moderate-severe TBI and polytrauma and their association with postoperative head computed tomography (CT) scans, intracranial pressure (ICP), and therapeutic intensity level (TIL) scores 24 h after surgery. After IRB approval, we reviewed the records of children <18 years with a Glasgow Coma Scale score <13 who underwent extracranial surgery within 72 h of TBI. Definitions of secondary insults were as follows: systemic hypotension (SBP <70 + 2 × age or 90 mmHg), cerebral hypotension (cerebral perfusion pressure <40 mmHg), intracranial hypertension (ICP >20 mmHg), hypoxia (oxygen saturation <90 %), hypercarbia (end-tidal CO2 >45 mmHg), hypocarbia (end-tidal CO2 <30 mmHg without hypotension and in the absence of intracranial hypertension), hyperglycemia (blood glucose >200 mg/dL), hyperthermia (temperature >38 °C), and hypothermia (temperature <35 °C).
RESULTS: Data from 50 surgeries in 42 patients (median age 15.5 years, 25 males) revealed systemic hypotension during 78 %, hypocarbia during 46 %, and hypercarbia during 25 % surgeries. Intracranial hypertension occurred in 64 % and cerebral hypotension in 18 % surgeries with ICP monitoring (11/50). Hyperglycemia occurred during 17 % of the 29 surgeries with glucose monitoring. Cerebral hypotension and hypoxia were associated with postoperative intracranial hypertension (p = 0.02 and 0.03, respectively). We did not observe an association between intraoperative secondary insults and postoperative worsening of head CT scan or TIL score.
CONCLUSIONS: Intraoperative secondary insults were common during extracranial surgery in pediatric TBI. Intraoperative cerebral hypotension and hypoxia were associated with postoperative intracranial hypertension. Strategies to prevent secondary insults during extracranial surgery in TBI are needed.

High-Pressure Headaches, Low-Pressure Syndromes, and CSF Leaks: Diagnosis and Management

Authors: Graff-Radford SB, Schievink WI.

BACKGROUND: Headache resulting from idiopathic intracranial hypertension (IIH) in a population of moderately to obese women of childbearing age. The causes overall remain unclear. With this review, we provide an overview of clinical treatment and management strategies.
RESULTS: IIH management is dependent on the signs and symptoms presented. Symptomatic treatment should attempt to lower intracranial pressure, reduce pain, and protect the optic nerves. Consideration for lumbar puncture and draining fluid as an option for reducing pressure may be helpful; however, repeated treatment is not usually favored by patients. Traditional prophylactic medications used in migraine may help reduce the primary headache often induced by raised intracranial pressure. We suggested surgical intervention for patients experiencing visual loss or impending visual loss and not responding to medication therapy.
CONCLUSION: In this review, we discuss headache associated with IIH and spontaneous intracranial hypotension. Much needs to be learned about treatment options for patients with cerebrospinal fluid leaks including methods to strengthen the dura.

Pathophysiology of cerebral oedema in acute liver failure

Authors: Scott TR, Kronsten VT, Hughes RD, Shawcross DL.

Cerebral oedema is a devastating consequence of acute liver failure (ALF) and may be associated with the development of intracranial hypertension and death. In ALF, some patients may develop cerebral oedema and increased intracranial pressure but progression to life-threatening intracranial hypertension is less frequent than previously described, complicating less than one third of cases who have proceeded to coma since the advent of improved clinical care. The rapid onset of encephalopathy may be dramatic with the development of asterixis, delirium, seizures and coma. Cytotoxic and vasogenic oedema mechanisms have been implicated with a preponderance of experimental data favouring a cytotoxic mechanism. Astrocyte swelling is the most consistent neuropathological finding in humans with ALF and ammonia plays a definitive role in the development of cytotoxic brain oedema. The mechanism(s) by which ammonia induces astrocyte swelling remains unclear but glutamine accumulation within astrocytes has led to the osmolyte hypothesis. Current evidence also supports an alternate 'Trojan horse' hypothesis, with glutamine as a carrier of ammonia into mitochondria, where its accumulation results in oxidative stress, energy failure and ultimately astrocyte swelling. Although a complete breakdown of the blood-brain barrier is not evident in human ALF, increased permeation to water and other small molecules such as ammonia has been demonstrated resulting from subtle alterations in the protein composition of paracellular tight junctions. At present, there is no fully efficacious therapy for cerebral oedema other than liver transplantation and this reflects our incomplete knowledge of the precise mechanisms underlying this process which remain largely unknown.

Predictability of intracranial pressure level in traumatic brain injury: features extraction, statistical analysis and machine learning-based evaluation

Authors: Chen W, Cockrell CH, Ward K, Najarian K.

This paper attempts to predict Intracranial Pressure (ICP) based on features extracted from non-invasively collected patient data. These features include midline shift measurement and textural features extracted from Computed axial Tomography (CT) images. A statistical analysis is performed to examine the relationship between ICP and midline shift. Machine learning is also applied to estimate ICP levels with a two-stage feature selection scheme. To avoid overfitting, all feature selections and parameter selections are performed using a nested 10-fold cross validation within the training data. The classification results demonstrate the effectiveness of the proposed method in ICP prediction.

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