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.     

Inflammation et lésions cérébrales aiguës en anesthésie réanimation

Patients with acute brain injuries or susceptibility to post-surgery stroke are a major therapeutic challenge for intensive care and anaesthesiology medicine. The control of systemic stress involved in brain damage is necessary to reduce the frequency and severity of secondary brain lesions. Inflammation is known to be directly involved in acute brain lesions. The brain is a major participant in inflammation control through activation or inhibition effects. The exact mechanisms involved in deleterious effects following acute brain injuries due to inflammation are still unknown. This non-exhaustive study will expose the principal processes involved in inflammatory brain disease and explain the consequences of peripheral inflammation for the brain. Neuroprotection strategies in acute neuroinflammation will be reported with a focus on anaesthetic agents and the inflammation cascade.     

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.     

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.     

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.     

EEG en réanimation : quelles indications,quel matériel ?

There is a growing development of continuous EEG monitoring (cEEG) in the intensive care unit (ICU) management of neurological patients. Its main objective is the detection of epileptic seizures or status epilepticus because the sensitivity of standard short-duration EEG recording in the ICU is poor. The aim of monitoring is to allow rapid recognition and treatment of epileptic complications in order to decrease secondary insults to the brain and improve outcome. Several studies have demonstrated that a large proportion of patients has epileptic crisis after subarachnoid haemorrhage, stroke or brain trauma, without any clinical manifestation. The EEG feature has also demonstrated a prognosis value but its value for clinical management needs further studies. Another application of EEG in the ICU is monitoring depth of anaesthesia or barbiturate treatment. Due to artifacts contamination, this is possible only in deeply sedated of paralyzed patients. The impact or cEEG monitoring on clinical management and its indications have to be further defined.     

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.     

Pas de chirurgie sans échographie préalable en cas de thrombose veineuse superficielle clinique : à propos d’un cas d’embolie paradoxale grave

Lower limbs superficial venous thrombosis (LLSVT) is usually considered as common and of a benign prognosis. LLSVT can, however, be responsible for major thromboembolic complications: lower limbs deep vein thrombosis (LLDVT) and pulmonary embolism (PE). We report a case of a LLSVT complicated with a massive bilateral PE and an ischemic cerebral stroke, occurring immediately after a varicose vein surgery. Venous ultrasonography of the lower limbs must be systematically performed in case of LLSVT, in order to evaluate the presence of an associated LLDVT. A rigorous diagnostic and therapeutic approach is the only way to optimize the treatment of this disorder, and to avoid the occurrence of dramatic venous thromboembolic complications.     

Les dangers de l’hypothermie thérapeutique

Therapeutic hypothermia (less than 35 °C) is a promising strategy to improve neuroprotection after severe brain injury. Except in patients resuscitated from cardiac arrest, its effectiveness has not yet been demonstrated. Therapeutic hypothermia results in various side effects, including cardiovascular, hydroelectrolytic and infectious disorders, which could explain, in part, the lack of conclusive clinical studies. These hazards are associated with practical difficulties to induce and maintain targeted hypothermia and with rewarming management. An improvement in the techniques for achieving targeted hypothermia, more knowledge about side effects and further randomized clinical trials are needed before recommending the use of therapeutic hypothermia for patients with severe traumatic brain injury.     

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.     

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.     

Le syndrome post-arrêt cardiaque chez l’enfant

The occurrence of post-cardiac arrest syndrome may lead to death in some children who have recovered from a cardiac arrest. The post-cardiac arrest syndrome includes systemic ischaemia/reperfusion response, brain injury, myocardial dysfunction, and persistence of the precipitating pathology. The main cause of death is brain injury. Management includes strictly control of ventilation, oxygen therapy and haemodynamics associated with protection of the brain against any secondary injury: management of seizures, control of glycaemia and central temperature. Mild hypothermia should be considered in comatose children after cardiac arrest.     

Pronostic des nouveau-nés de mère prééclamptique

Preeclampsia (PE) is associated with 3 main risks for the fetus: perinatal death, intrauterine growth restriction (IUGR), preterm birth. Perinatal mortality is increased in infants with IUGR or asphyxia. Conversely, mortality and morbidity associated with preterm birth are not altered by PE without IUGR or asphyxia. Very preterm infant with IUGR are exposed to high risk of prolonged respiratory insufficiency. Neurological complications of prematurity are not more frequent in infants born to mothers with PE. Nevertheless birth asphyxia, (i.e. placental abruption) is associated with impaired neurological out-come especially in infants with neonatal encephalopathy. Long term outcome of infants born to mothers with PE is strongly correlated to gestational age. IUGR increases the risk of hypertension and metabolic syndrome in adulthood. Acute fatty liver of pregnancy can by caused by a fetal fatty-acid oxidation disorder.     

Thrombolyse postopératoire immédiate dans un contexte d’accident vasculaire sylvien gauche

Intravenous thrombolytic therapy for ischemic stroke was performed on a 75-year-old patient at recovery from cervicocephalic superficial surgery. The patient recovered totally from ischemic stroke and no neurologic sequelae was observed. Thrombolytic therapy must be performed in an intensive care unit in order to manage some bleeding events which can occur.     

Chirurgie arthroscopique de l’épaule et complications ischémiques cérébrales

The authors report three cases in which cerebral ischemia occurred during arthroscopic shoulder surgery performed in beach chair position under general anaesthesia and interscalene plexus block. Several similar cases have been published in the literature. This rare but extremely severe complication is related to the decrease in cerebral perfusion pressure (CPP). Monitoring of CPP in the beach chair position using the measurement of arterial pressure and taking into account the hydrostatic gradient is essential. Prevention includes correction of preoperative hypovolaemia, treatment of postural arterial hypotension, adequate installation of the patient's head, aggressive treatment of perioperative arterial hypotension (whatever the cause) and avoidance of deliberate perioperative arterial hypotension. Routine use of non-invasive monitoring of cerebral oxygenation has been advocated to avoid this accident but its usefulness has to be confirmed by clinical studies.     

Accident vasculaire cérébral ischémique : une complication rare du kyste hydatique du foie

Hydatid cyst of the liver (HCL) is a widespread disease in North African countries. We report the case of a 39-year-old patient who was admitted in our intensive care unit because of anaphylactic shock due to a cracked HCL fortuitously discovered. This accident was also complicated by an ischemic stroke witch underline mechanisms are discussed.     

Fibrillation atriale en anesthésie–réanimation : de la cardiologie médicale à la période périopératoire

Atrial fibrillation (AF) is the most frequent arythmia. During the perioperative period and in intensive care units, management of patients with AF is frequent and difficult. As in cardiology, two main issues are present: the risk of acute hemodynamically instability and the risk of thromboembolic complication. Cardiological guidelines recently published must guide the management of patients in this context. Two main factors must be kept in mind: acute AF in these situations are often of short duration; the risk of anticoagulation can be superior to the risk of thrombotic complication in this situation. An individualized benefit–risk analysis must be done in each patient. New treatments, antiarrhythmic or mainly antithrombotic drugs, are under evaluation and will be soon available.     

Chirurgie éveillée des gliomes cérébraux : plaidoyer pour un investissement accru des anesthésistes

The recent development of awake surgery in neuro-oncology allowed a conceptual change, i.e. the realization of resection for invasive brain tumors according to functional and not anatomic boundaries. This paradigmatic shift enabled a significant improvement of results in surgery for gliomas, by opening the door to resections within eloquent areas classically considered as “inoperable”, while preserving and even improving the quality of life of patients. In addition, the extent of resections has been maximized, leading to an increase of median survival – especially in low-grade gliomas. Strong relationships between the different teams (surgeons, neuropsychologists, anaesthesiologists) are crucial for the development and improvement of awake surgery. Thus, it seems important that anesthesiologists can benefit from a clear and accurate knowledge of the real contribution of this procedure, in order to better evaluate the balance between the theoretical risks of surgery under local anesthesia versus the actual risk of not performing resection with a maximum of safety and efficiency for the patients. The purpose of this plea is to advocate the spread of awake surgery in routine practice, due to its major impact on both functional and survival outcomes, by nonetheless keeping in mind that a multidisciplinary staff is mandatory for selection of patients as well as into the operating room. In this state of mind, anaesthesiologists have to play a central role, through an increased involvement in this field.     

Hématome rétroplacentaire

Retroplacental haematoma (RPH) is a complication affecting 0.25 to 0.4% of all pregnancies and 4% of severe PEs. It is of acute onset, usually unpredictable and its symptoms are not specific: Isolated metrorrhagia, foetal distress, uterine hypertonicity. Clinical, biological and sonographic features suggesting a RPH can be early or late. Haemoconcentration and the forming of notches on Doppler examination of the uterus can appear weeks before the event, whereas raised D-Dimers and foetal tachycardia are identified within days of the event. Although Caesarian section reduces the perinatal death rate by 20 to 50% in a setting of RPH with a live foetus, vaginal delivery is indicated in cases of RPH with fetal demise, following the control of haemorrhagic shock, clotting disorders and uterine hypotonicity.     

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.