Hyperventilation in head injury: a review

Hyperventilation Therapy for Control of Posttraumatic Intracranial Hypertension

During traumatic brain injury, intracranial hypertension (ICH) can become a life-threatening condition if it is not managed quickly and adequately. Physicians use therapeutic hyperventilation to reduce elevated intracranial pressure (ICP) by manipulating autoregulatory functions connected to cerebrovascular CO₂ reactivity. Inducing hypocapnia via hyperventilation reduces the partial pressure of arterial carbon dioxide (PaCO₂), which incites vasoconstriction in the cerebral resistance arterioles. This constriction decrease cerebral blood flow, which reduces cerebral blood volume and, ultimately, decreases the patient’s ICP. The effects of therapeutic hyperventilation (HV) are transient, but the risks accompanying these changes in cerebral and systemic physiology must be carefully considered before the treatment can be deemed advisable. The most prominent criticism of this approach is the cited possibility of developing cerebral ischemia and tissue hypoxia. While it is true that certain measures, such as cerebral oxygenation monitoring, are needed to mitigate these dangerous conditions, using available evidence of potential poor outcomes associated with HV as justification to dismiss the implementation of therapeutic HV is debatable and remains a controversial subject among physicians. This review highlights various issues surrounding the use of HV as a means of controlling posttraumatic ICH, including indications for treatment, potential risks, and benefits, and a discussion of what techniques can be implemented to avoid adverse complications.

Critical Evaluation of the Lund Concept for Treatment of Severe Traumatic Head Injury, 25 Years after Its Introduction

When introduced in 1992, the Lund concept (LC) was the first complete guideline for treatment of severe traumatic brain injury (s-TBI). It was a theoretical approach, based mainly on general physiological principles-i.e., of brain volume control and optimization of brain perfusion and oxygenation of the penumbra zone. The concept gave relatively strict outlines for cerebral perfusion pressure, fluid therapy, ventilation, sedation, nutrition, the use of vasopressors, and osmotherapy. The LC strives for treatment of the pathophysiological mechanisms behind symptoms rather than just treating the symptoms. The treatment is standardized, with less need for individualization. Alternative guidelines published a few years later (e.g., the Brain Trauma Foundation guidelines and European guidelines) were mainly based on meta-analytic approaches from clinical outcome studies and to some extent from systematic reviews. When introduced, they differed extensively from the LC. We still lack any large randomized outcome study comparing the whole concept of BTF guidelines with other guidelines including the LC. From that point of view, there is limited clinical evidence favoring any of the s-TBI guidelines used today. In principle, the LC has not been changed since its introduction. Some components of the alternative guidelines have approached those in the LC. In this review, I discuss some important principles of brain hemodynamics that have been lodestars during formulation of the LC. Aspects of ventilation, nutrition, and temperature control are also discussed. I critically evaluate the most important components of the LC 25 years after its introduction, based on hemodynamic principles and on the results of own an others experimental and human studies that have been published since then.

Neurocritical Care of Acute Subdural Hemorrhage

Although urgent surgical hematoma evacuation is necessary for most patients with subdural hematoma (SDH), well-orchestrated, evidenced-based, multidisciplinary, postoperative critical care is essential to achieve the best possible outcome. Acute SDH complicates approximately 11% of mild to moderate traumatic brain injuries (TBIs) that require hospitalization, and approximately 20% of severe TBIs. Acute SDH usually is related to a clear traumatic event, but in some cases can occur spontaneously. Management of SDH in the setting of TBI typically conforms to the Advanced Trauma Life Support protocol with airway taking priority, and management breathing and circulation occurring in parallel rather than sequence.

Alterations in Cerebral Blood Flow after Resuscitation from Cardiac Arrest

Greater than 50% of patients successfully resuscitated from cardiac arrest have evidence of neurological disability. Numerous studies in children and adults, as well as in animal models have demonstrated that cerebral blood flow (CBF) is impaired after cardiac arrest. Stages of cerebral perfusion post-resuscitation include early hyperemia, followed by hypoperfusion, and finally either resolution of normal blood flow or protracted hyperemia. At the level of the microcirculation the blood flow is heterogeneous, with areas of no flow, low flow, and increased flow. CBF directed therapies in animal models of cardiac arrest improved neurological outcome, and therefore, the alterations in CBF after cardiac arrest likely contribute to the development of hypoxic ischemic encephalopathy. Current intensive care after cardiac arrest is centered upon maintaining systemic oxygenation, normal blood pressure values for age, maintaining general homeostasis, and avoiding hyperthermia. Assessment of CBF and oxygenation is not routinely performed after cardiac arrest. Currently available and underutilized techniques to assess cerebral perfusion include transcranial doppler, near-infrared spectroscopy, and arterial spin labeling magnetic resonance imaging. Limited clinical studies established the role of CBF and oxygenation monitoring in prognostication after cardiac arrest and few studies suggest that guiding critical care post-resuscitation to mean arterial pressures above the minimal autoregulatory range might improve outcome. Important knowledge gaps thus remain in cerebral monitoring and CBF and oxygen goal-directed therapies post-resuscitation from cardiac arrest.

Emergency Neurological Life Support: Airway, Ventilation, and Sedation

Airway management and ventilation are central to the resuscitation of the neurologically ill. These patients often have evolving processes that threaten the airway and adequate ventilation. Furthermore, intubation, ventilation, and sedative choices directly affect brain perfusion. Therefore, airway, ventilation, and sedation was chosen as an emergency neurological life support protocol. Topics include airway management, when and how to intubate with special attention to hemodynamics and preservation of cerebral blood flow, mechanical ventilation settings, and the use of sedative agents based on the patient's neurological status.

Neurologic Emergencies in the Patients With Cancer

Neurologic complications of cancer are common and are frequently life-threatening events. Certain neurologic emergencies occur more frequently in the cancer population, specifically elevated intracranial pressure, epidural cord compression, status epilepticus, ischemic and hemorrhagic stroke, central nervous system infection, and treatment-associated neurologic dysfunction. These emergencies require early diagnosis and prompt treatment to ensure the best possible outcome and are best managed in the intensive care unit. This article reviews the presentation, pathophysiology, and management of the most common causes of acute neurologic decompensation in the patient with cancer.

Monitoring intracranial pressure utilizing a novel pattern of brain multiparameters in the treatment of severe traumatic brain injury

The aim of the study was to evaluate the clinical value of multiple brain parameters on monitoring intracranial pressure (ICP) procedures in the therapy of severe traumatic brain injury (sTBI) utilizing mild hypothermia treatment (MHT) alone or a combination strategy with other therapeutic techniques. A total of 62 patients with sTBI (Glasgow Coma Scale score <8) were treated using mild hypothermia alone or mild hypothermia combined with conventional ICP procedures such as dehydration using mannitol, hyperventilation, and decompressive craniectomy. The multiple brain parameters, which included ICP, cerebral perfusion pressure, transcranial Doppler, brain tissue partial pressure of oxygen, and jugular venous oxygen saturation, were detected and analyzed. All of these measures can control the ICP of sTBI patients to a certain extent, but multiparameters associated with brain environment and functions have to be critically monitored simultaneously because some procedures of reducing ICP can cause side effects for long-term recovery in sTBI patients. The result suggested that multimodality monitoring must be performed during the process of mild hypothermia combined with conventional ICP procedures in order to safely target different clinical methods to specific patients who may benefit from an individual therapy.

Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a worldwide health burden with high fatality and permanent disability rates. The overall prognosis depends on the volume of the initial bleed, rebleeding, and degree of delayed cerebral ischemia (DCI). Cardiac manifestations and neurogenic pulmonary edema indicate the severity of SAH. The International Subarachnoid Aneurysm Trial (ISAT) reported a favorable neurological outcome with the endovascular coiling procedure compared with surgical clipping at the end of 1 year. The ISAT trial recruits were primarily neurologically good grade patients with smaller anterior circulation aneurysms, and therefore the results cannot be reliably extrapolated to larger aneurysms, posterior circulation aneurysms, patients presenting with complex aneurysm morphology, and poor neurological grades. The role of hypothermia is not proven to be neuroprotective according to a large randomized controlled trial, Intraoperative Hypothermia for Aneurysms Surgery Trial (IHAST II), which recruited patients with good neurological grades. Patients in this trial were subjected to slow cooling and inadequate cooling time and were rewarmed rapidly. This methodology would have reduced the beneficial effects of hypothermia. Adenosine is found to be beneficial for transient induced hypotension in 2 retrospective analyses, without increasing the risk for cardiac and neurological morbidity. The neurological benefit of pharmacological neuroprotection and neuromonitoring is not proven in patients undergoing clipping of aneurysms. DCI is an important cause of morbidity and mortality following SAH, and the pathophysiology is likely multifactorial and not yet understood. At present, oral nimodipine has an established role in the management of DCI, along with maintenance of euvolemia and induced hypertension. Following SAH, hypernatremia, although less common than hyponatremia, is a predictor of poor neurological outcome.

Anesthetic management of labor and delivery in patients with elevated intracranial pressure

The anesthetic management of labor and delivery in patients with elevated intracranial pressure is complex. This review discusses the etiologies of diffuse and focal pathologies which lead to elevated intracranial pressure in pregnancy. The role of neuraxial and general anesthesia in the management of labor and delivery is also examined. Finally, a comprehensive review of strategies to minimize increases in intracranial pressure during general anesthesia for cesarean delivery is presented.

Postsurgical meningitis complicated by severe refractory intracranial hypertension with limited treatment options: the role of mild therapeutic hypothermia

Intracranial hypertension is a commonly encountered neurocritical care problem. If first-tier therapy is ineffective, second-tier therapy must be initiated. In many cases, the full arsenal of established treatment options is available. However, situations occasionally arise in which only a narrow range of options is available to neurointensivists. We present a rare clinical scenario in which therapeutic hypothermia was the only available method for controlling intracranial pressure and that demonstrates the efficacy and safety of the Thermogard (Zoll, Chelmsford, Massachusetts, United States) cooling system in creating and maintaining a prolonged hypothermic state. The lifesaving effect of hypothermia was overshadowed by the unfavorable neurologic outcome observed (minimally conscious state on intensive care unit discharge). These results add further evidence to support the role of therapeutic hypothermia in managing intracranial pressure and provide motivation for finding new strategies in combination with hypothermia to improve neurologic outcomes.

Brain cell swelling during hypocapnia increases with hyperglycemia or ketosis

BACKGROUND

Severe hypocapnia reduces cerebral blood flow (CBF) and is known to be a risk factor for diabetic ketoacidosis (DKA)-related cerebral edema and cerebral injury in children. Reductions in CBF resulting from hypocapnia alone, however, would not be expected to cause substantial cerebral injury. We hypothesized that either hyperglycemia or ketosis might alter the effects of hypocapnia on CBF and/or cerebral edema associated with CBF reduction.

METHODS

We induced hypocapnia (pCO₂ 20 ± 3 mmHg) via mechanical ventilation in three groups of juvenile rats: 25 controls, 22 hyperglycemic rats (serum glucose 451 ± 78 mg/dL), and 15 ketotic rats (β-hydroxy butyrate 3.0 ± 1.0 mmol/L). We used magnetic resonance imaging to measure CBF and apparent diffusion coefficient (ADC) values in these groups and in 17 ventilated rats with normal pCO₂ (40 ± 3 mmHg). In a subset (n = 35), after 2 h of hypocapnia, pCO₂ levels were normalized (40 ± 3 mmHg) and ADC and CBF measurements were repeated.

RESULTS

Declines in CBF with hypocapnia occurred in all groups. Normalization of pCO₂ after hypocapnia resulted in hyperemia in the striatum. These effects were not substantially altered by hyperglycemia or ketosis. Declines in ADC (suggesting brain cell swelling) during hypocapnia, however, were greater during both hyperglycemia and ketosis.

CONCLUSIONS

We conclude that brain cell swelling associated with hypocapnia is increased by both hyperglycemia and ketosis, suggesting that these metabolic conditions may make the brain more vulnerable to injury during hypocapnia.

Body temperature affects cerebral hemodynamics in acutely brain injured patients: an observational transcranial color-coded duplex sonography study

Introduction

Temperature changes are common in patients in a neurosurgical intensive care unit (NICU): fever is frequent among severe cases and hypothermia is used after cardiac arrest and is currently being tested in clinical trials to lower intracranial pressure (ICP). This study investigated cerebral hemodynamics when body temperature varies in acute brain injured patients.

Methods

We enrolled 26 patients, 14 with acute brain injury who developed fever and were given antipyretic therapy (defervescence group) and 12 who underwent an intracranial neurosurgical procedure and developed hypothermia in the operating room; once admitted to the NICU, still under anesthesia, they were re-warmed before waking (re-warming group). We measured cerebral blood flow velocity (CBF-V) and pulsatility index (PI) at the middle cerebral artery using transcranial color-coded duplex sonography (TCCDS).

Results

In the defervescence group mean CBF-V decreased from 75 ± 26 (95% CI 65 to 85) to 70 ± 22 cm/s (95% CI 61 to 79) (P = 0.04); the PI also fell, from 1.36 ± 0.33 (95% CI 1.23 to 1.50) to 1.16 ± 0.26 (95% CI 1.05 to 1.26) (P = 0.0005). In the subset of patients with ICP monitoring, ICP dropped from 16 ± 8 to 12 ± 6 mmHg (P = 0.003). In the re-warming group mean CBF-V increased from 36 ± 10 (95% CI 31 to 41) to 39 ± 13 (95% CI 33 to 45) cm/s (P = 0.04); the PI rose from 0.98 ± 0.14 (95% CI 0.91 to 1.04) to 1.09 ± 0.22 (95% CI 0.98 to 1.19) (P = 0.02).

Conclusions

Body temperature affects cerebral hemodynamics as evaluated by TCCDS; when temperature rises, CBF-V increases in parallel, and viceversa when temperature decreases. When cerebral compliance is reduced and compensation mechanisms are exhausted, even modest temperature changes can greatly affect ICP.

Capillary transit time heterogeneity and flow-metabolism coupling after traumatic brain injury

Most patients who die after traumatic brain injury (TBI) show evidence of ischemic brain damage. Nevertheless, it has proven difficult to demonstrate cerebral ischemia in TBI patients. After TBI, both global and localized changes in cerebral blood flow (CBF) are observed, depending on the extent of diffuse brain swelling and the size and location of contusions and hematoma. These changes vary considerably over time, with most TBI patients showing reduced CBF during the first 12 hours after injury, then hyperperfusion, and in some patients vasospasms before CBF eventually normalizes. This apparent neurovascular uncoupling has been ascribed to mitochondrial dysfunction, hindered oxygen diffusion into tissue, or microthrombosis. Capillary compression by astrocytic endfeet swelling is observed in biopsies acquired from TBI patients. In animal models, elevated intracranial pressure compresses capillaries, causing redistribution of capillary flows into patterns argued to cause functional shunting of oxygenated blood through the capillary bed. We used a biophysical model of oxygen transport in tissue to examine how capillary flow disturbances may contribute to the profound changes in CBF after TBI. The analysis suggests that elevated capillary transit time heterogeneity can cause critical reductions in oxygen availability in the absence of 'classic' ischemia. We discuss diagnostic and therapeutic consequences of these predictions.

Cushing's reflex in a rare case of adult medulloblastoma

BACKGROUND

Medulloblastoma is a primitive neuro-ectodermal tumor. It is common in childhood, but rarely seen at adult age, comprising only 1% of primary brain tumors.

METHODS

We treated a 31-year-old man presented to the emergency department (ED) with a chief complaint of nausea and vomiting for one week duration. Immediate frozen section revealed a grade IV medulloblastoma. During the hospital course, the patient was given craniospinal irradiation with chemotherapy.

RESULTS

The patient was eventually discharged from the hospital to an assisted living facility after an uneventful 15-day course with the aid of social work.

CONCLUSIONS

Despite intracranial tumors generally being slow growing masses, this patient demonstrates how quickly one can decompensate, and how important it is to recognize these clinical signs and symptoms of an intracranial lesion. Although these symptoms (i.e. Cushing response) are extremely rare, the ED physician should be aware and appreciate their clinical significance.

A survey of routine treatment of patients with intracranial hypertension (ICH) in specialized trauma centers in Sao Paulo, Brazil: a 11 million metropole!

OBJECTIVE

A survey of intensive care units (ICU) in São Paulo that care for patients with TBI and ICH using the hyperventilation technique.

METHODS

A questionnaire was given to the physiotherapist coordinator at 57 hospitals in São Paulo, where 24-h neurosurgery service is provided.

RESULTS

Fifty-one (89.5%) hospitals replied. From this total, thirty-four (66.7% perform the hyperventilation technique, 30 (85%) had the objective to reach values below 35 mmHg, four (11%) levels between 35 mmHg and 40 mmHg and one (3%) values over 40 mmHg.

CONCLUSIONS

We concluded that most hospitals in São Paulo perform hyperventilation in patients with severe brain trauma although there are not any specific Brazilian guidelines on this topic. Widespread controversy on the use of the hyperventilation technique in patients with severe brain trauma highlights the need for a specific Global policy on this topic.

Management of increased intracranial pressure

OPINION STATEMENT

After brain injury, neurologic intensive care focuses on the detection and treatment of secondary brain insults that may compound the initial injury. Increased intracranial pressure (ICP) contributes to secondary brain injury by causing brain ischemia, hypoxia, and metabolic dysfunction. Because ICP is easily measured at the bedside, it is the target of numerous pharmacologic and surgical interventions in efforts to improve brain physiology and limit secondary injury. However, ICP may not adequately reflect the metabolic health of the underlying brain tissue, particularly in cases of focal brain injury. As a result, ICP control alone may be insufficient to impact patients' long-term recovery. Further studies are needed to better understand the combination of cerebral, hemodynamic, and metabolic markers that are best utilized to ensure optimal brain and systemic recovery and overall patient outcome after brain injury.

Cerebral hyperemia measured with near infrared spectroscopy during treatment of diabetic ketoacidosis in children

OBJECTIVE

To use near infrared spectroscopy (NIRS) to evaluate the timing of onset and duration of cerebral hyperemia during diabetic ketoacidosis (DKA) treatment in children, and to investigate the relationship of cerebral hyperemia to intravenous fluid treatment.

STUDY DESIGN

We randomized children aged 8-18 years with DKA to either more rapid or slower intravenous fluid treatment (19 total DKA episodes). NIRS was used to measure rSo2 during DKA treatment. NIRS monitoring began as soon as informed consent was obtained and continued until the patient was transferred out of the critical care unit.

RESULTS

rSo2 values above the normal range (>80%) were detected in 17 of 19 DKA episodes (mean rSo2 during initial 8 hours of DKA treatment: 86% ± 7%, range 65%-95%). Elevated rSo2 values were detected as early as the second hour of DKA treatment and persisted for as long as 27 hours. Hourly mean rSo2 levels during treatment did not differ significantly by fluid treatment group.

CONCLUSIONS

During DKA treatment, children have elevated rSo2 values consistent with cerebral hyperemia. Hyperemia occurs as early as the second hour of DKA treatment and may persist for ≥ 27 hours. Cerebral rSo2 levels during treatment did not differ significantly in patients treated with slower versus more rapid intravenous rehydration.

Influence of probe pressure on the diffuse correlation spectroscopy blood flow signal: extra-cerebral contributions

A pilot study explores relative contributions of extra-cerebral (scalp/skull) versus brain (cerebral) tissues to the blood flow index determined by diffuse correlation spectroscopy (DCS). Microvascular DCS flow measurements were made on the head during baseline and breath-holding/hyperventilation tasks, both with and without pressure. Baseline (resting) data enabled estimation of extra-cerebral flow signals and their pressure dependencies. A simple two-component model was used to derive baseline and activated cerebral blood flow (CBF) signals, and the DCS flow indices were also cross-correlated with concurrent Transcranial Doppler Ultrasound (TCD) blood velocity measurements. The study suggests new pressure-dependent experimental paradigms for elucidation of blood flow contributions from extra-cerebral and cerebral tissues.

Strategies for the use of mechanical ventilation in the neurologic intensive care unit

Mechanical ventilation in neurologically injured patients presents unique challenges. Patients with acute neurologic injuries may require mechanical ventilation for reasons beyond respiratory failure. There is also a subset of pulmonary pathologic abnormality directly associated with neurologic injuries. Balancing the need to maintain brain oxygenation, cerebral perfusion, and control of intracranial pressure can be in conflict with concurrent ventilator strategies aimed at lung protection. Weaning and liberation from mechanical ventilation also require special considerations. These issues are examined in the ventilator management of the neurologically injured patient.

Effects of indomethacin test on intracranial pressure and cerebral hemodynamics in patients with refractory intracranial hypertension: a feasibility study

BACKGROUND

Intracranial hypertension is the final pathway of many neurocritical entities, such as spontaneous intracerebral hemorrhage (sICH) and severe traumatic brain injury (sTBI).

OBJECTIVE

This study aimed to (1) determine alterations in intracranial pressure (ICP) and cerebral hemodynamics after an indomethacin (INDO) infusion test and the related association with survival in patients with refractory intracranial hypertension (RICH) secondary to sICH or sTBI and (2) assess the safety profile after INDO.

METHODS

INDO was administered in a loading dose (0.8 mg/kg/15 min), followed by a 2-hour continuous infusion (0.5 mg/kg/h) in RICH patients with ICP greater than 20 mm Hg who did not respond to first-line therapies. Changes in ICP, cerebral perfusion pressure (CPP), and cerebrovascular variables (assessed by transcranial Doppler and jugular bulb saturation) were observed. Clinical outcome was assessed at 1 and 6 months according to the Glasgow Outcome Scale and correlated with INDO infusion test response. Analysis of INDO safety profile was conducted.

RESULTS

Thirteen sICH and 10 sTBI patients were studied. The median GCS score at admission was 6. Within 30 minutes of INDO infusion, ICP decreased (42.0 ± 13.5 vs 27.70 ± 12.7 mm Hg; Δ%: -48.4%; P < .001), and both CPP (57.7 ± 4.8 vs 71.9 ± 7.0 mm Hg; Δ%: +26.0%; P < .001) and middle cerebral artery velocity (35.2 ± 5.6 vs 42.0 ± 5.1 cm·s(-1); Δ%: +26.1%; P < .001) increased. The CPP response to a 2-hour INDO infusion test was correlated (R2 = 0.72, P < .001) with survival. No adverse events were observed after INDO.

CONCLUSION

Our findings support the effectiveness and feasibility of an INDO test in decreasing ICP and improving cerebral hemodynamics in surviving RICH patients. Future studies to evaluate different doses, lengths of infusion, and longer term effects are needed.

Clinical review: Respiratory monitoring in the ICU - a consensus of 16

Monitoring plays an important role in the current management of patients with acute respiratory failure but sometimes lacks definition regarding which 'signals' and 'derived variables' should be prioritized as well as specifics related to timing (continuous versus intermittent) and modality (static versus dynamic). Many new techniques of respiratory monitoring have been made available for clinical use recently, but their place is not always well defined. Appropriate use of available monitoring techniques and correct interpretation of the data provided can help improve our understanding of the disease processes involved and the effects of clinical interventions. In this consensus paper, we provide an overview of the important parameters that can and should be monitored in the critically ill patient with respiratory failure and discuss how the data provided can impact on clinical management.

Mechanical ventilation after injury

Injury is a major cause of critical illness worldwide. Severely injured patients often require mechanical ventilation not only to manage primary respiratory failure but also as adjunct to manage other conditions. Injury induces fundamental changes in multiple organ systems which directly impact ventilator management; these changes are not shared by patients without concomitant tissue injury. In this article, we review the physiologic changes after injury and discuss the impact of injury on ventilator strategies and management. We also explore the special considerations in patients with traumatic brain injury, thermal injury, blast injury or bronchopleural fistula.

Increased inspired oxygen in the first hours of life is associated with adverse outcome in newborns treated for perinatal asphyxia with therapeutic hypothermia

OBJECTIVE

To assess whether increased inspired oxygen and/or hypocarbia during the first 6 hours of life are associated with adverse outcome at 18 months in term neonates treated with therapeutic hypothermia.

STUDY DESIGN

Blood gas values and ventilatory settings were monitored hourly in 61 newborns for 6 hours after birth. We investigated if there was an association between increased inspired oxygen and/or hypocarbia and adverse outcome (death or disability by Bayley Scales of Newborn Development II examination at 18-20 months).

RESULTS

Hypothermia was started from 3 hours 45 minutes (10 minutes-10 hours) and median lowest Pco(2) level within the first 6 hours of life was 30 mm Hg (16.5-96 mm Hg). The median highest fraction of inspiratory oxygen within the first hour of life was 0.43 (0.21-1.00). The area under the curve fraction of inspiratory oxygen and Pao(2) for hours 1-6 of life was 0.23 (0.21-1.0) and 86 mm Hg (22-197 mm Hg), respectively. We did not find any association between any measures of hypocapnia and adverse outcome (P > .05), but increased inspired oxygen correlated with adverse outcome, even when excluding newborns with initial oxygenation failure (P < .05).

CONCLUSION

Increased fraction of inspired oxygen within the first 6 hours of life was significantly associated with adverse outcome in newborns treated with therapeutic hypothermia following hypoxic ischemic encephalopathy.

Perioperative management of the pediatric patient with traumatic brain injury

TBI and its sequelae remain a major healthcare issue throughout the world. With an improved understanding of the pathophysiology of TBI, refinements of monitoring technology, and ongoing research to determine optimal care, the prognosis of TBI continues to improve. In 2003, the Society of Critical Care Medicine published guidelines for the acute management of severe TBI in infants, children, and adolescents. As pediatric anesthesiologists are frequently involved in the perioperative management of such patients including their stabilization in the emergency department, familiarity with these guidelines is necessary to limit preventable secondary damage related to physiologic disturbances. This manuscript reviews the current evidence-based medicine regarding the care of pediatric patients with TBI as it relates to the perioperative care of such patients. The issues reviewed include those related to initial stabilization, airway management, intra-operative mechanical ventilation, hemodynamic support, administration of blood and blood products, positioning, and choice of anesthetic technique. The literature is reviewed regarding fluid management, glucose control, hyperosmolar therapy, therapeutic hypothermia, and corticosteroids. Whenever possible, management recommendations are provided.

Change in the electroencephalogram delta wave in the frontal cranial region of rats with the hyperventilation

Hyperventilation is one way to cause activation on the electroencephalogram (EEG) to diagnose brain disorders. The hyperventilation is also known to affect on the delta power in EEG. This study divided the total delta wave into low, middle, and high bands corresponding to the wave frequency. The power in these three delta wave bands was examined in the frontal cranial region of adult male Sprague-Dawley rats hyperventilated with ventilation (VE) of 360, 540, and 720 ml/min for 5 min. The control group was ventilated normally with a volume of 160 ml/min. The results show that the relative power of the low delta band in the rats hyperventilated at 360 ml/min VE was significantly increased compared with powers of pre-hyperventilation (p<0.05). The relative power of the middle delta band was not significantly affected by hyperventilation at any VE, and in the high delta band, all of the relative powers were decreased significantly in all hyperventilated rats compared with powers of pre-hyperventilation (p<0.05). We concluded that hyperventilation affects the frontal cranial region, by increasing the low delta band and decreasing the high delta band.

Contemporary view on neuromonitoring following severe traumatic brain injury

Evolving brain damage following traumatic brain injury (TBI) is strongly influenced by complex pathophysiologic cascades including local as well as systemic influences. To successfully prevent secondary progression of the primary damage we must actively search and identify secondary insults e.g. hypoxia, hypotension, uncontrolled hyperventilation, anemia, and hypoglycemia, which are known to aggravate existing brain damage. For this, we must rely on specific cerebral monitoring. Only then can we unmask changes which otherwise would remain hidden, and prevent adequate intensive care treatment. Apart from intracranial pressure (ICP) and calculated cerebral perfusion pressure (CPP), extended neuromonitoring (SjvO₂, ptiO₂, microdialysis, transcranial Doppler sonography, electrocorticography) also allows us to define individual pathologic ICP and CPP levels. This, in turn, will support our therapeutic decision-making and also allow a more individualized and flexible treatment concept for each patient. For this, however, we need to learn to integrate several dimensions with their own possible treatment options into a complete picture. The present review summarizes the current understanding of extended neuromonitoring to guide therapeutic interventions with the aim of improving intensive care treatment following severe TBI, which is the basis for ameliorated outcome.

Randomized controlled trials affecting polytrauma care

Trauma remains the leading cause of death in the world in patients under 45 years of age. The evaluation, resuscitation, and appropriate management of polytraumatized patients are paramount to successful outcomes. The advance of evidence-based medicine has had a powerful and positive impact on trauma care, even though the nature of many traumatic injuries lends itself poorly to study in a randomized fashion. During the initial management of bleeding patients, hypotensive resuscitation prior to surgical control has found strong support in the literature, and its use has been adopted by many surgeons. Head injury is the most common cause of traumatic death, and while high-level evidence is limited, adherence to management guidelines is associated with improved outcomes. For abdominal trauma, the concept of damage control surgery, while popular, has never been put to the test in a randomized controlled trial. Numerous randomized trials in the field of critical care have affected the management of severely injured patients, including intensive insulin therapy and low tidal volume ventilation in patients with compromised respiratory function. Finally, a multidisciplinary approach to trauma care in designated trauma centers allows for improved outcomes in polytraumatized patients.

Managing malignant cerebral infarction

OPINION STATEMENT

Managing patients with malignant cerebral infarction remains one of the foremost challenges in medicine. These patients are at high risk for progressive neurologic deterioration and death due to malignant cerebral edema, and they are best cared for in the intensive care unit of a comprehensive stroke center. Careful initial assessment of neurologic function and of findings on MRI, coupled with frequent reassessment of clinical and radiologic findings using CT or MRI are mandatory to promote the prompt initiation of treatments that will ensure the best outcome in these patients. Significant deterioration in either neurologic function or radiologic findings or both demand timely treatment using the best medical management, which may include osmotherapy (mannitol or hypertonic saline), endotracheal intubation, and mechanical ventilation. Under appropriate circumstances, decompressive craniectomy may be warranted to improve outcome or to prevent death.

Inappropriate prehospital ventilation in severe traumatic brain injury increases in-hospital mortality

In the setting of acute brainstem herniation in traumatic brain injury (TBI), the use of hyperventilation to reduce intracranial pressure may be life-saving. However, undue use of hyperventilation is thought to increase the incidence of secondary brain injury through direct reduction of cerebral blood flow. This is a retrospective review determining the effect of prehospital hyperventilation on in-hospital mortality following severe TBI. All trauma patients admitted directly to a single level 1 trauma center from January 2000 to January 2007 with an initial Glasgow Coma Scale (GCS) score <or=8 were included in the study (n = 77). Patients without documented or with late (>20 min) arterial blood gas at presentation (n = 12) were excluded from the study. The remaining population (n = 65) was sorted into three groups based on the initial partial pressure of carbon dioxide: hypocarbic (Pco(2) < 35 mm Hg), normocarbic (Pco(2) 35-45 mm Hg), and hypercarbic (Pco(2) > 45 mm Hg). Outcome was based on mortality during hospital admission. Survival was found to be related to admission Pco(2) in head trauma patients requiring intubation (p = 0.045). Patients with normocarbia on presenting arterial blood gas testing had in-hospital mortality of 15%, significantly improved over patients presenting with hypocarbia (in-hospital mortality 77%) or hypercarbia (in-hospital mortality 61%). Although there are many reports of the negative impact of prophylactic hyperventilation following severe TBI, this modality is frequently utilized in the prehospital setting. Our results suggest that abnormal Pco(2) on presentation after severe head trauma is correlated with increased in-hospital mortality. We advocate normoventilation in the prehospital setting.

Spontaneous intracerebral haemorrhage: a clinical review

This article provides a clinical overview of spontaneous intracerebral haemorrhage, focusing on clinical aspects of the aetiology, diagnosis and management (both in the emergency department and in a critical care environment) of this important and devastating condition.

Impact of hyperventilation on stimulus efficiency during the early phase of an electroconvulsive therapy course: a randomized double-blind study

OBJECTIVE

The question whether hyperventilation during electroconvulsive therapy (ECT) can improve stimulus efficiency is as yet unanswered.

METHODS

Twenty-five consecutive consenting patients (N = 25) with major depression who were administered ECT entered into the study. Right unilateral ECT at thrice the threshold dose was administered using Mecta spECTrum 5000Q (Mecta Corp, Lake Oswego, Ore), with standard titration procedures and stimulus configurations. At the second ECT session, they were randomly allocated to ECT either with hyperventilation or with no hyperventilation. Hyperventilation was actively administered by an anesthetist just after anesthetic paralysis and before the ECT stimulus during the second, third, and fourth ECT sessions. Assessments were double-blind and performed at baseline and 24 to 48 hours after the fourth ECT session. Time to reorient after ECT was assessed during the first up to the fourth ECT session. Ictal electroencephalogram (EEG) quality was visually assessed using standard scales.

RESULTS

There were no significant differences across the 2 groups about depression severity and global cognitive impact. However, the orientation time was 34% longer among those who did not receive hyperventilation. The ratio of orientation time without hyperventilation to that with hyperventilation equals 1.34 (95% confidence interval, 0.94-1.92; P = 0.103). There was a significant increase in threshold over time across both groups (mean difference, 16.4; SE, 5.5; P = 0.006) with no significant main effect for the groups (P = 0.399). There were no significant group differences in the EEG quality.

CONCLUSIONS

The addition of hyperventilation during the early phase of the ECT course shows a trend to lessen the impact on immediate orientation without impeding clinical response. This does not seem to be mediated by differential threshold changes or change to the ictal EEG quality.

The pathophysiology and causes of raised intracranial pressure

This article explains the pathophysiology and causes of raised intracranial pressure (ICP), and the significance of assessing and recording vital observations for all patients when admitted to hospital. It discusses the nursing care, treatment and management required in order to minimize the risk of further increases in ICP.

Neurobiology of repeated transcranial magnetic stimulation in the treatment of anxiety: a critical review

Transcranial magnetic stimulation (TMS) has been applied to a growing number of psychiatric disorders as a neurophysiological probe, a primary brain-mapping tool, and a candidate treatment. Although most investigations have focused on the treatment of major depression, increasing attention has been paid to anxiety disorders. The aim of this study is to summarize published findings about the application of TMS as a putative treatment for anxiety disorders. TMS neurophysiological and mapping findings, both clinical and preclinical, have been included when relevant. We searched Medline, PsycInfo, and the Cochrane Library from 1980 to January 2009 for the terms 'generalized anxiety disorder', 'social anxiety disorder', 'social phobia', 'panic', 'anxiety', or 'posttraumatic stress disorder' in combination with 'TMS', 'cortex excitability', 'rTMS', 'motor threshold', 'motor evoked potential', 'cortical silent period', 'intracortical inhibition', 'neuroimaging', or 'intracortical facilitation'. Most of the therapeutic experiences with repetitive TMS available in the literature are in the form of case reports, not controlled or blinded studies. Stimulation of the right dorsolateral prefrontal cortex, especially at high frequencies, has been reported to reduce anxiety symptoms in posttraumatic stress disorder and panic disorder; nevertheless, results are mixed. A specific role for the right dorsolateral prefrontal cortex in the posttraumatic stress disorder symptom core can be hypothesized. TMS remains an investigational intervention that has not yet gained approval for the clinical treatment of any anxiety disorder. Clinical sham-controlled trials are scarce. Many of these trials have supported the idea that TMS has a significant effect, but in some studies, the effect is small and short lived. The neurobiological correlates suggest possible efficacy for the treatment of social anxiety that still has to be investigated.

Management of intracranial hypertension

Raised intracranial pressure (ICP) is a life threatening condition that is common to many neurological and non-neurological illnesses. Unless recognized and treated early it may cause secondary brain injury due to reduced cerebral perfusion pressure (CPP), and progress to brain herniation and death. Management of raised ICP includes care of airway, ventilation and oxygenation, adequate sedation and analgesia, neutral neck position, head end elevation by 20 degrees-30 degrees, and short-term hyperventilation (to achieve PCO(2) 32-35 mm Hg) and hyperosmolar therapy (mannitol or hypertonic saline) in critically raised ICP. Barbiturate coma, moderate hypothermia and surgical decompression may be helpful in refractory cases. Therapies aimed directly at keeping ICP <20 mmHg have resulted in improved survival and neurological outcome. Emerging evidence suggests that cerebral perfusion pressure targeted therapy may offer better outcome than ICP targeted therapies.