Quelle pression de perfusion cérébrale après traumatisme crânien chez l’enfant ?

The management of cerebral perfusion pressure (CPP) is the one of the main preoccupation for the care of paediatric traumatic brain injury (TBI). The physiology of cerebral autoregulation, CO₂ vasoreactivity, cerebral metabolism changes with age as well as the brain compliance. Low CPP leads to high morbidity and mortality in pediatric TBI. The recent guidelines for the management of CPP for the paediatric TBI indicate a CPP threshold 40–50 mmHg (infants for the lower and adolescent for the upper). But we must consider the importance of age-related differences in the arterial pressure and CPP. The best CPP is the one that allows to avoid cerebral ischaemia and oedema. In this way, the adaptation of optimal CPP must be individual. To assess this objective, interesting tools are available. Transcranial Doppler can be used to determine the best level of CPP. Other indicators can predict the impairment of autoregulation like pressure reactivity index (PRx) taking into consideration the respective changes in ICP and CPP. Measurement of brain tissue oxygen partial pressure is an other tool that can be used to determine the optimal CPP.     

Pour ou contre les halogénés en neuroanesthésie pour chirurgie intracrânienne

Isoflurane, desflurane and sevoflurane all preserve cerebrovascular carbone dioxide (CO₂) reactivity. They are all concentration-dependant cerebral vasodilatators and decrease cerebral metabolism. Sevoflurane induces the smallest cerebral vasodilatation and preserve cerebral autoregulation up to 1.5 CAM, compared to isoflurane and desflurane which impair it upon 1 CAM. Propofol has been compared to inhaled agents. Propofol preserve cerebrovascular CO₂ reactivity, blood flow-metabolism coupling, cerebral autoregulation and has no vasodilatation effect. None of the three inhaled agents induce any clinical relevant increase of intracranial pressure (ICP), but studies were conducted in patients without any intracranial hypertension (ICHT). However, compared to propofol, ICP and brain swelling were higher with inhaled agents, more with isoflurane compared to sevoflurane. Finally, neuroprotective properties have been described in experimental model for all the inhaled agents but clinical proofs are still lacking. In conclusion, for intracranial surgery without any ICHT inhaled agents can be used as a maintenance anesthetic with a preference for sevoflurane. In case of ICHT or a risk of ICHT during the surgery, propofol is preferred for it slightest effect on ICP and cerebral hemodynamic.     

Intérêt du monitorage de l’index bispectral (BIS) pour la détection précoce des hypoperfusions cérébrales

Objectives

The goal of the study was to assess whether clinically significant cerebral hypoperfusion in awake patients would be associated with some alterations in the values of the bispectral index (BIS) monitoring.

Study design

Observational study.

Population and methods

We monitored the BIS during endovascular carotid artery occlusion testing in awake patients.

Results

Twenty-eight patients were included. Twenty-one adequately tolerated the procedure. Their BIS value remained stable throughout the procedure. Four patients had poor angiographic tolerance, but no clinical symptoms. Their BIS value slightly decreased during the test (minimal BIS: 83 [79–87]). Three patients had poor clinical and angiographic tolerance of the occlusion. They all experienced an immediate and dramatic decrease in their BIS value (minimal BIS: ipsilateral to clamping: 50 [45–60]; contralateral to clamping: 48 [45–52]). In all patients, the clinical symptoms and the BIS normalized after deflating the occlusion balloon.

Conclusion

In awake patients, the observed values of the BIS monitoring seem to be associated with clinically relevant cerebral hypoperfusion.     

Pression tissulaire cérébrale en oxygène : pour quoi faire et pour qui ?

The main purpose of neurointensive care is to fight against cerebral ischaemia. Ischaemia is the cell energy failure following inadequacy between supply of glucose and oxygen and demand. Ischemia monitoring starts with a global approach, especially with cerebral perfusion pressure (CPP) determined by mean arterial pressure and intracranial pressure (ICP). However, global monitoring is insufficient to detect “regional” ischaemia, leading to development of local monitoring such as brain oxygen partial pressure (PtiO₂). PtiO₂ is measured on a volume of a few mm³ from a probe implanted in the cerebral tissue. The normal value is classically included between 25 and 35 mmHg and critical ischemic threshold is 10 mmHg. Understanding what exactly is PtiO₂ is still a matter of debate. PtiO₂ is more an indicator of oxygen diffusion depending of oxygen arterial pressure (PaO₂) and local cerebral blood flow (CBF). Increase PaO₂ to treat PtiO₂ would hide information about local CBF. PtiO₂ is useful for the detection of low local CBF even when ICP is low as in hypocapnia-induced vasoconstriction. PtiO₂-guided management could lead to a continuous optimization of arterial oxygen transport for an optimal cerebral tissue oxygenation. Finally, PtiO₂ has probably a global prognostic value because studies showed that hypoxic values for a long period of time lead to an unfavourable neurologic outcome. In conclusion, PtiO₂ provides additional information for regional monitoring of cerebral ischaemia and deserves more intensive use to better understand it and probably improve neurointensive care management.     

Hypothermie et protection cérébrale après traumatisme crânien. Influence des gaz du sang

The usefulness of therapeutic hypothermia is highly debated after traumatic brain injury. A neuroprotective effect has been demonstrated only in experimental studies: decrease in cerebral metabolism, restoration of ATP level, better control of cerebral edema and cellular effects. Despite negative multicenter clinical studies, therapeutic hypothermia is still used to a better control of intracranial pressure. However, important issues need to be clarified, particularly the level and duration of hypothermia, the depth and modalities of sedation. A clear understanding of blood gases variations induced by hypothermia is needed to understand the cerebral perfusion and oxygenation changes. It is essential to recognize and to use hypothermia-induced physiological hypocapnia and alkalosis under strict control of cerebral oxygen balance (jugular venous saturation or tissue PO₂) and also to take into account the increased affinity of hemoglobin for oxygen. Management of post-traumatic intracranial hypertension using hypothermia, directed by intracranial pressure level, and consequently for long duration, is potentially beneficial but needs further clarification.     

Focal cerebral ischemia after surgery in the "beach chair" position: the role of a congenital variation of circle of Willis anatomy

A 50-year-old man underwent shoulder surgery in the beach chair position. His mean arterial blood pressure at arm level was approximately 65 mm Hg. Postoperatively, there was delayed awakening and a right hemiparesis. Radiologic evaluation revealed a congenital asymmetry of the circle of Willis that resulted in limited collateral flow to the left anterior and middle cerebral artery distributions. Similar anatomical variations are relatively common in the general population and may render some patients relatively and unpredictably more vulnerable to hypotension.     

Hyperoxie normobarique chez le patient traumatisé crânien

Cerebral ischaemia plays a major role in the outcome of brain-injured patients. Because brain oxygenation can be assessed at bedside using intra-parenchymal devices, there has been a growing interest about whether therapeutic hyperoxia could be beneficial for severely head-injured patients. Normobaric hyperoxia increases brain oxygenation and may improve glucose-lactate metabolism in brain regions at risk for ischaemia. However, benefits of normobaric hyperoxia on neurological outcome are not established yet, that hinders the systematic use of therapeutic hyperoxia in head-injured patients. This therapeutic option might be proposed when brain ischemia persists despite the optimization of cerebral blood flow and arterial oxygen blood content.     

Anesthésie et hypertension artérielle pulmonaire chez l’enfant en chirurgie non cardiaque

Paediatric pulmonary arterial hypertension (PAH) is a challenge for the paediatric anaesthetist. Due to its high morbidity and mortality, support should be provided by a dedicated team. Understanding the pathophysiology of PAH allows performing an appropriate therapeutic approach. In case of high vascular pulmonary resistance, the main objectives of anaesthetic management are to maintain an optimal pulmonary flow and to avoid the decrease in systemic arterial pressure. Haemodynamic monitoring is essential to detect the onset of an acute PAH crisis but also to give direct information on the efficacy of treatment.     

Cerebral oxygenation in patients undergoing shoulder surgery in beach chair position: Comparing general to regional anesthesia and the impact on neurobehavioral outcome

BackgroundIschemic brain damage has been reported in healthy patients after beach chair position for surgery due to cerebral hypoperfusion. Near-infrared spectroscopy has been described as a non-invasive, continuous method to monitor cerebral oxygen saturation. However, its impact on neurobehavioral outcome comparing different anesthesia regimens has been poorly described.MethodsIn this prospective, assessor-blinded study, 90 patients undergoing shoulder surgery in beach chair position following general (G-group, n = 45) or regional anesthesia (R-group; n = 45) were enrolled to assess the prevalence of cerebral desaturation events comparing anesthesia regimens and their impact on neurobehavioral and neurological outcome. Anesthesiologists were blinded to regional cerebral oxygen saturation values. Baseline data assessed the day before surgery included neurological and neurobehavioral tests, which were repeated the day after surgery. The baseline data for regional cerebral oxygen saturation/bispectral index and invasive blood pressure both at heart and auditory meatus levels were taken prior to anesthesia, 5 min after induction of anesthesia, 5 min after beach chair positioning, after skin incision and thereafter all 20 min until discharge.ResultsPatients in the R-group showed significantly less cerebral desaturation events (p < 0.001), drops in regional cerebral oxygen saturation values (p < 0.001), significantly better neurobehavioral test results the day after surgery (p < 0.001) and showed a greater hemodynamic stability in the beach chair position compared to patients in the G-group.ConclusionsThe incidence of regional cerebral oxygen desaturations seems to influence the neurobehavioral outcome. Regional anesthesia offers more stable cardiovascular conditions for shoulder surgery in beach chair position influencing neurobehavioral test results at 24 h.     

L’hypernatrémie contrôlée est-elle utile en neuroréanimation ?

Hypernatremia invariably denotes hyperosmolarity and, at least transiently, causes cellular dehydratation. Because of blood brain barrier properties, cerebral tissue volume is modified by acute changes in osmolarity. An acute hyperosmolarity (by intravenous sodium or mannitol) temporally decreases intracranial pressure. This treatment is thus useful in critical situations, allowing time for diagnosis and, if possible, other treatment. But in cases of sustained hypernatremia, cellular dehydratation is rapidly counterbalanced by an increase in cellular osmolarity. For the brain, it has been shown that cerebral volume is restored in a few hours during prolonged hypernatremia. Moreover, the plasmatic osmotic load induces an increase in diuresis and natriuresis. A tight control is then necessary to prevent hypovolemia and electrolytes disorders. Teams using this treatment should undertake controlled randomized studies to ascertain any beneficial effect that cannot be explained by physiology.     

Œdème cérébral : nouvelles pistes thérapeutiques

Cerebral oedema (CO) after brain injury can occur from different ways. The vasogenic and cytotoxic oedema are usually described but osmotic and hydrostatic CO, respectively secondary to plasmatic hypotonia or increase in blood pressure, can also be encountered. Addition of these several mechanisms can worsen injuries. Consequences are major, leading quickly to death secondary to intracerebral hypertension and later to neuropsychic sequelae. So therapeutic care to control this phenomenon is essential and osmotherapy is actually the only way. A better understanding of physiopathological disorders, particularly energetic ways (lactate), aquaporine function, inflammation lead to new therapeutic hopes. The promising experimental results need now to be confirmed by clinical data.     

Rôle délétère de l’hyperthermie en neuroréanimation

Fever is a secondary brain injury and may worsen neurological prognosis of neurological intensive care unit (NICU) patients. In response to an immunological threat, fever associates various physiological reactions, including hyperthermia. Its definition may vary but the most commonly used threshold is 37.5 °C. In animal studies, hyperthermia applied before, during or after cerebral ischemia may increase the volume of ischemic lesions. The mechanism of this effect may include increase in blood brain barrier permeability, increase in excitatory amino acid release and increase in free radical production. In NICU patients, fever is frequent, occurring in up to 20–30% of patients. Moreover, after haemorrhagic stroke, fever has been reported in 40–50% of patients. In half of the patients, fever may be related to an infectious cause but in more than 25% of patients, hyperthermia may be of central origin. After ischemic stroke, hyperthermia during the first 72 hours is associated with an increase in infarct size and increase in morbidity and mortality. This holds true also after subarachnoid haemorrhage. After traumatic brain injury, fever is not related to mortality but may increase morbidity. Whereas no causal link has been established between fever and unfavourable outcome, it seems reasonable to treat hyperthermia in patients suffering from brain injuries. In such patients, antipyretics have a moderate efficacy. In case of failure, they should be replaced by physical cooling techniques.     

L’oxymétrie cérébrale transcutanée en anesthésie pédiatrique

Cerebral oximetry allows continuous real-time and non-invasive monitoring of cerebral oxygen saturation (cSO₂), by measuring oxyhaemoglobin and deoxyhaemoglobin near infrared light absorption, similarly to pulse oximetry. cSO₂ measurement predominantly reflects brain venous compartment, and is correlated with jugular venous saturation. As jugular venous saturation, cSO₂ must therefore be interpreted as a measure of balance between transport and consumption of O₂ in the brain. Cerebral oximetry should be used as a trend monitoring, because its accuracy is insufficient to be considered as reliable measure of absolute value of ScO₂. In adult, correction of intraoperative cerebral desaturation reduces hospital stay, heavy morbidity and mortality, and serious postoperative neurocognitive impairment after cardiac and major abdominal surgery. In children, the occurrence of intra- and postoperative cerebral desaturations during congenital heart surgery is associated with increased neurological morbi-mortality. Cerebral oximetry could be a useful monitoring during anaesthesia of (ex) preterm neonates, due to the risk of impaired cerebral blood flow autoregulation in these patients.     

Postpartum reversible cerebral angiopathy: an unusual cause of headache

We present the case of a 34-year-old woman who developed, in postpartum period of an uncomplicated pregnancy, a thunderclap headache with visual disturbance associated with a severe arterial hypertension. Both clinical evolution and cerebral imaging including angio-MR confirmed the diagnosis of postpartum reversible vasoconstriction syndrome. One of the leading causes of this syndrome is the use of vasoactive drugs as it was observed in the case of this patient. It is important to consider this syndrome in the differential diagnosis in patients presenting with headache in the postpartum period.     

Effects of alterations in arterial CO2 tension on cerebral blood flow during acute intracranial hypertension in rats.

Cerebrovascular reactivity to CO2 in clinical and experimental studies has been found to be impaired during increased intracranial pressure (ICP). However, from previous study results it has not been possible to estimate whether the impairment was caused by elevated ICP, or caused by decreased cerebral perfusion pressure (CPP). The current study was carried out in a group of unmanipulated control rats and in six investigation groups of six rats each: two groups with elevated ICP (30 and 50 mm Hg) and spontaneous arterial blood pressure (MABP), two groups with spontaneous ICP and arterial hypotension (77 and 64 mm Hg), and two groups with elevated ICP (30 and 50 mm Hg) and arterial hypertension (124 mm Hg). Intracranial hypertension was induced by continuous infusion of lactated Ringer's solution into the cisterna magna, arterial hypotension by controlled bleeding, and arterial hypertension by continuous administration of norepinephrine intravenously. Cerebral blood flow (CBF) was measured repetitively by the intraarterial 133Xe method at different levels of arterial PCO2. In each individual animal, CO2 reactivity was calculated from an exponential regression line obtained from the corresponding CBF/PaCO2 values. By plotting each individual value of CO2 reactivity against the corresponding CPP value from the seven investigation groups, CPP was significantly and directly related to CO2 reactivity of CBF (P < .001). No correlation was found by plotting CO2 reactivity values against the corresponding MABP values or the corresponding ICP values. Thus, the results show that CO2 reactivity is at least partially determined by CPP and that the impaired CO2 reactivity observed at intracranial hypertension and arterial hypotension may be caused by reduced CPP.     

Prise en charge initiale en réanimation des traumatisés graves du bassin

Pelvic trauma care is complex since it is frequently associated with multiple injuries and may lead to dramatic and uncontrollable haemorrhage. After pelvic trauma, the mortality, around 8 to 10%, is mainly related to severe pelvic hemorrhage but also to extrapelvic injuries (thoracic, abdominal or brain injuries). It is therefore crucial to manage pelvic trauma in specialized trauma center. The initial trauma assessment aims to determine the role of the pelvic injury in hemorrhage to define the therapeutic strategy of pelvic trauma care (arterial embolisation/pelvic ring stabilisation). This review was performed with a systematic review of the literature; it describes the pelvic fracture pathophysiology, and the efficacy and safety of haemostatic procedures and with their respective indications. A decision making algorithm is proposed for the treatment of trauma patients with pelvic fracture.     

The effect of positive end-expiratory pressure (PEEP) ventilation in neurogenic pulmonary oedema

Summary The effect of positive end-expired pressure ventilation (PEEP) on mean systemic arterial pressure, mean pulmonary arterial pressure, mean pulmonary wedge pressure, mean intracranial pressure (ICP), and cerebral perfusion pressure (CPP), in a case of neurogenic pulmonary oedema (NPO) is presented. PEEP improved oxygenation, reduced, and finally stopped clinical pulmonary oedema. In this patient PEEP produced severe systemic hypotension. As a consequence of this, CPP was impaired.     

Anesthésie et insuffisance cardiaque droite

Objective

The purpose of this review was to present an update of the anaesthesic management in patients with right ventricular failure (RVF).

Data sources

All references obtained from the medical database Medline^® related to the area and more specifically during the last five years were reviewed.

Data synthesis

The preanaesthesic visit leads to identify the etiology of RVF, to evaluate the functional reserve of the patient, to plan complementary exams and to inform the patients about the risks associated with the perioperative period. During the peroperative period, the monitoring depends of the severity of the illness; however the invasive monitoring of the systemic blood pressure seems always necessary. Any hemodynamic instability should be avoided during the peri-operative period. Since the risk of death is maximal in the first days after the anaesthesia, the patient is ideally managed in intensive care during this period.

Conclusion

Right ventricular failure is often misestimates. However, the perioperative morbidity and mortality of patients with RVF are important. In the perioperative period, the anaesthesiologist should identify patients at risk of right ventricular failure in order to adapt their management.     

Agressions cérébrales,immunité et infections

Infections are a major cause of death and morbidity after acute injury of the central nervous system (CNS). Acute lesions of the CNS alter immune homeostasis contributing to the development of immunosuppression (IS), and making the bed of the infection. IS results in a decreased phagocytic functions of neutrophils and macrophages as well as monocyte deactivation (decreased capacity of antigen presentation to lymphocytes). The immune abnormalities occur very quickly and may last for weeks. The neurovegetative system is closely connected to the secondary lymphoid organs where cells of innate immunity receive information from injured organs inducing the long lasting adaptive immune response (immune synapse). The sympathetic system is critically involved in the IS through production of anti-inflammatory mediators like interleukin-10. This may prove important as all types of acute injury of the CNS can lead to direct damage to sympathetic centers. Specialized units of care for ischemic stroke, taking into account the risk of infection related to the IS, have improved the prognosis until 18th month after the initial damage of the SNC. It is now well recognized that the improved long-term prognosis is related with the secondary prevention of recurrent ischaemia as well as aggressive management of pulmonary infections. A better understanding of the pathophysiology of IS can be considered in the near future, opening the door to immunomodulatory therapeutic trials.     

Thrombus aortique compliquant un traumatisme thoracique balistique

We report the case of a stroke due to a ballistic thoracic traumatism. The vascular injury, provoked by the passage of the bullet, associated to a procoagulating state led to the formation of a thrombus in the ascending aorta. The migration of this thrombus caused a stroke, finally reversible upon medical treatment only.