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.     

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.     

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.     

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.     

Hémorragie cérébrale chez un enfant asthmatique ventilé : mécanismes multifactoriels

We report the case of a 7-year-old boy with acute status asthmaticus requiring mechanic ventilation in the pediatric intensive care unit. He developed a brain hemorrhage during the course of his illness. We discuss the mechanisms that may have precipitated this neurological complication.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.