Techniques de mesure de la pression intracrânienne

A wide variety of monitoring devices have been used for intracranial pressure measurement. The aim of this article is to present the most common devices and to assess their accuracy, stability and complications, with reference to current literature. Measurement with an intraventricular catheter remains the reference method. However new techniques with distal measurement (fiberoptic or strain gauge) seem to be accurate, but have a higher cost. Some practical problems, such as the zero pressure reference level and the side of measurement, are also discussed.     

Effet de la position sur la pression intracrânienne

The question as to whether the head and trunk of neurosurgery patients should be elevated remains controversial. This question is particularly important when intracranial hypertension is present. Head up position may have beneficial effects on intracranial pressure (ICP) via changes in mean arterial pressure (MAP), airway pressure, central venous pressure and cerebro spinal fluid displacement. However, in some circumstances, head up position may decrease MAP which in turn will result in a paradoxical rise in ICP through autoregulation mechanisms. Therefore, the degree of head elevation has to be titrated by evaluating the most adequate cerebral perfusion pressure (CPP) for each patient by means of transcranial Doppler or measurement of jugular venous blood oxygen saturation. Head elevation above 30° should be avoided in all cases. In most patients with intracranial hypertension, head and trunk elevation up to 30° is useful in helping to decrease ICP, providest that a safe CPP of at least 70 mmHg or even 80 mmHg is maintained. Patients in poor haemodynamic conditions are best nursed flat. CPP is thus the most important factor in assessment and monitoring when considering head elevation in patients with increased ICP.     

Monitorage et maintien de la volémie au cours de la chirurgie intracrânienne

Intraoperative monitoring usually does not assess intravascular blood volume of the patient. The variations of the systolic blood pressure and the right auricular pressure allow to appreciate the intravascular blood volume changes and their consequences on the cerebral perfusion pressure. However, when the autoregulation of the cerebral blood flow is strongly depressed, the evaluation of the cerebral perfusion pressure alone is inadequate. In this case, the optimal monitoring should be metabolic (jugular bulb venous oxygen saturation) to finally assess the cerebral flow-metabolic coupling.     

Développement et croissance de la base du crâne

The skull base is a part of the neuro-cranium formed by endochondral ossification. The embryological origin of the skull base is not perfectly known, but there seems to be an anterior region derived from the neural crest and a posterior part derived from the mesoderm. Further studies are needed to define reliable presumptive maps. The origin of the different components of the occipital bone is just as poorly known. Much fundamental work remains to be done to suggest any solution to these problems in humans.     

Dermatoscopia no teste cutâneo da patergia: série de casos de pacientes com suspeita de Doença de Behçet

Behçet's disease is a multisystemic disease consisting of a varying combination of ocular, mucocutaneous, neurologic, cardiovascular, gastrointestinal and other manifestations. Its diagnosis is based on clinical criteria, in which a positive pathergy test scores 1. A case series with 26 suspected patients is presented, and the skin pathergy test was performed in 23. The results were read in 48 hours, and they were considered negative when without papule, and positive with a papule or pustule. Positive results were divided by papule size, and dermatoscopy was done to measure and observe its clinical aspects. After the readings, a biopsy was performed, with annotation of histopathological aspects. The test was negative in 2 (8.7%) and positive in 21 (91.3%) patients. The results and the literature review are presented.     

Développement et croissance de la voûte du crâne

The vault of the skull is a region of the neurocranium formed by a process of membranous ossification. It consists of several bones: frontal bone, parietal bone, squamous part of the temporal bone, lamina ascendens of the sphenoid, and interparietal bone. The embryological origin of the bones of the skull vault is still the subject of controversy. This can be explained by the different animal models used for these purposes, but also by the various techniques applied to this problem. At all events, it seems that the cells of the neural crest generate some of the bones of the vault and that the others are derived from the mesoderm. This uncertainty should lead readers to be extremely cautious before using the presumptive maps published in the literature. Several tissues interact with osteo-progenitor cells: neural tube, surface ectoderm and dura mater. Analysis of genes in which mutations lead to abnormalities of the skull vault has partly revealed the molecular interactions. These are very complex and are the field of very numerous experimental investigations. In the relatively near future, we can hope to discover some of the molecular networks leading to the formation of these bony structures.     

Eficácia de diferentes doses e esquemas de administração de ácido tranexâmico em cirurgias ortopédicas de grande porte: estudo randomizado

BackgroundTranexamic acid was studied in four different dosage regimens and their efficacy was compared for perioperative blood loss reduction, blood transfusion requirements and deep vein thrombosis (DVT) complication.MethodsTwo hundred patients undergoing major orthopedic procedures were divided into five groups containing 40 each: placebo, low dose (bolus 10 mg.kg^‐1), low dose + maintenance (bolus 10 mg.kg^‐1 + maintenance 1 mg.kg^‐1.hr^‐1), high dose (bolus 30 mg.kg^‐1) and high dose + maintenance (bolus 30 mg.kg^‐1 + maintenance 3 mg.kg^‐1.hr^‐1). Surgical blood loss was measured intraoperatively and drains collection in the first 24 hours postoperative period. Blood transfusion was done when hematocrit falls less than 25%. DVT screening was done in the postoperative period.ResultsThe intraoperative blood loss was 440 ± 207.54 mL in the placebo group, 412.5 ± 208.21 mL in the low dose group, 290 ± 149.6 ml in the low dose plus maintenance group, 332.5 ± 162.33 mL in the high dose group and 240.7 ± 88.15 mL in the high dose maintenance group (p < 0.001). The reduction in postoperative blood loss in the drain for the first 24 hours was 80 ± 44.44 mL in the placebo group, 89.88 ± 44.87 mL in the low dose group, 56.7 ± 29.12 mL in the low dose plus maintenance group, 77.9 ± 35.74 mL in the high dose group and 46.7 ± 19.9 mL in the high dose maintenance group (p < 0.001). DVT was not encountered in any patient.ConclusionTranexamic acid was most effective in reducing surgical blood loss and blood transfusion requirements in a low dose + maintenance group.     

Bloqueio do nervo articular e cutâneo no cotovelo: relato de dois casos

Background and objectivesIn patients with elbow fractures, when there is suspected injury to underlying nerves, it is imperative for surgeons to elicit the function in the immediate postoperative period. Brachial plexus blocks like interscalene, supraclavicular and infraclavicular approaches can be a hurdle in such situations. The block planned should allow assessment of integrity of the nerves immediately in the postoperative period.Case reportWe describe two cases in which we administered a block not yet described in literature. We blocked the cutaneous and articular branches innervating the elbow under ultrasound guidance. General anesthesia was administered in both cases. The block provided stable intraoperative hemodynamics, good postoperative analgesia and also allowed surgeons to test the viability of the nerve.ConclusionIn situations where nerves are injured during elbow fractures, selective articular cutaneous block at elbow can be used as it provides good perioperative analgesia, besides allowing evaluation of motor and sensory components in the postoperative period.     

Prévention de l'augmentation de la pression artérielle et de la pression intracrânienne lors de l'intubation endotrachéale en neurochirurgie: esmolol versus lidocaïne

ObjectivesTo compare the preventive effects of esmolol and lidocaine on the increase in mean arterial pressure (MAP) and intracranial pressure (ICP) during endotracheal intubation in neurosurgery.Study designComparative, randomised, double-blind study.PatientsTwenty-two patients, physical status ASA I or II, undergoing neurosurgery, and randomised into two groups (esmolol group and lidocaine group).MethodsAfter induction of anaesthesia with thiopentone, vecuronium, fentanyl and isoflurane, one group received iv esmolol 1.5 mg·kg⁻¹ and the other iv lidocaine 1.5 mg·kg⁻¹, 130 sec before endotracheal intubation. The MAP measured with a radial catheter, the ICP obtained with a lumbar subarachnoid catheter and the cerebral perfusion pressure (CPP, calculated from MAP and ICP) were assessed before induction of anaesthesia, before esmolol or lidocaine injection, and before intubation, during the maximal change in MAP, as well as 2 and 5 minutes after intubation.ResultsThe time course of MAP, ICP and CCP were similar throughout the study in the two groups, with a significant decrease (P < 0.05) of the CPP from 92 ± 12 to 628 mmHg after esmolol, and from 96 ± 12 to 68 ± 15 mmHg after lidocaine. Following intubation, CPP increased significantly (P < 0.05) to 99 ± 23 mmHg after esmolol and to 99 ± 17 mmHg after lidocaine. The ICP increased also significantly (P < 0.05) after intubation from 11 ± 6 to 17 ± 10 mmHg in the esmolol group, and from 10 ± 6 to 16 ± 9 mm Hg in the lidocaine group.ConclusionsEsmotol or lidocaine as an iv bolus of 1.5 mg·kg⁻¹ before laryngoscopy and intubation do not completely prevent the increase in MAP and ICP.     

Y a-t-il encore une place pour l'hypocapnie profonde de routine en chirurgie intracrânienne ?

Deliberate hypocapnia during the anaesthetic management of the patient undergoing craniotomy has become an accepted standard of care. However there has been a resurgence of interest, in how hypocapnia should be applied in intra- and extra-operative settings. There are three possible therapeutic effects of hypocapnia, namely, (a) reduction of brain bulk through a reduction in cerebral blood volume, with a decrease cerebral blood flow; (b) developing an « inverse stealby redistribution of blood from normal to ischaemic regions and (c) acting to offset cerebral acidosis by increasing pH in the extracellular space. In anaesthetic intraoperative practice, hypocapnia is used as a specific treatment of, or prophylaxis against, intracranial hypertension during induction of anaesthesia and the period before dural exposure. More commonly, hypocapnia is used for intraoperative brain relaxation (intracranial pressure = 0). Severe hypocapnia (< 20 mmHg) may result in cerebral production of lactate; however no studies have shown that a Paco₂ in the range of 23–28 mmHg has deleterious effects. Recent studies in head-injured patients suggest that routine long-term hyperventilation, without an objective index of cerebral flow/metabolism coupling, may place the brain at risk for adverse outcome. The few data available for intraoperative management suggest that Paco₂ figures of 30–35 mmHg result in acceptable operating conditions. Unless otherwise specifically indicated by surgical conditions or cerebral flow/metabolism coupling (e.g. jugular O2 saturation), routine application of profound (Paco₂ < 28–30 mmHg) hyperventilation should probably be avoided and its use needs reevaluation.