Biomedical subjects

J-F Payen

Publications and source records attributed to J-F Payen.

8 recordsLinked to original sources

PubMed2006

[Brain perfusion and metabolism imaging techniques].

Due to recent efforts in improving spatial and temporal resolution in imaging techniques, it is now possible to get relevant information about brain perfusion and metabolism in humans. This information can significantly impact on brain pathophysiology, diagnosis assessment and therapy options, particularly in patients having brain ischemia. Among these imaging and metabolism techniques are dynamic perfusion computed tomography, perfusion MRI, positron emission tomography and NMR spectroscopic imaging. The goal of this article is an overview of these four techniques, with their own technical description, advantages and drawbacks. Details are provided about brain parameters given by each technique and their clinical relevance, the accessibility of the technique in the emergency setting and the optimal window to use it during the patient's evolution.

Brain↗

PubMed2005

[Contribution of magnetic resonance spectroscopy in predicting severity and outcome in traumatic brain injury].

Nuclear magnetic spectroscopy (MRS) is a useful method for noninvasively studying intracerebral metabolism. Proton MRS can identify markers of the neuronal viability (N-acetyl-aspartate, NAA), of the metabolism of cellular membranes (choline), of the cellular energy metabolism (creatine, lactate). In Phosphorus MRS, the peaks most readily identified are involved in the high-energy cellular metabolism (ATP, phosphocreatine, inorganic phosphate), and intracellular pH (pHi) can be determined using this method. MRS has been used in experimental models of traumatic brain injury (TBI), primarily to study the cellular metabolism and the relation between biochemical and histological changes after trauma. In trauma patients, significant changes in NAA, choline and pHi were found in both grey and white matter comparing with controls, and these alterations correlated with injury severity. Correlations have been reported between these biochemical changes (reduction in NAA, increase in choline) measured at 1 to 6 months after TBI and the clinical outcome of the patients. However, there are methodological issues which still impede to recommend MRS as a tool for predicting neurological outcome in the clinical setting.

Animals↗

PubMed2005

[Prevention of venous perioperative thromboembolism in ENT and maxillofacial surgery].

There are few studies of poor methodological quality on the risk of thromboembolism in head and neck surgery. The incidence of symptomatic deep vein thrombosis is estimated between, 0.1% and 0.6%. The patient's risk factors (cancer, alcoholism, smoking, malnutrition) determine for the assessment of the potential benefit of thromboembolism prophylaxis. No method can be recommended based on the literature. In patients receiving anticoagulant therapy undergoing superficial head and neck surgery or dental extraction, the literature suggest to continue anticoagulation throughout the perioperative period.

Humans↗

PubMed2005

[Thromboprophylaxis in elective spinal surgery and spinal cord injury].

The risk of deep vein thrombosis (DVT) after spinal cord injury is very high. Without prophylaxis the incidence of DVT using venography is 81% and the risk of symptomatic DVT is between 12 and 23%. The risk is much lower in elective spine surgery. After discectomy or laminectomy on less than two spine levels, the risk of DVT is less than 1%. After spinal fusion or extended laminectomy, the risk can be estimated between 0.3 and 2.2%. A prophylaxis is recommended for all patients after spinal cord injury (grade A). The association of a mechanical method and heparin is recommended (grade B). The duration of prophylaxis is 3 months in patients with a motor deficit (grade C). No prophylaxis is recommended after discectomy or limited laminectomy in patients without additional risk factors. Mechanical methods are recommended after spinal fusion or extended laminectomy. For patients with additional risk factors a low molecular weight heparin is recommended.

Ambulatory Surgical Procedures↗

PubMed2005

[Thromboprophylaxis in neurosurgery and head trauma].

The incidence of deep vein thrombosis (DVT) is between 20 and 35% using contrast venography, with a rate of symptomatic DVT between 2.3 and 6% in neurosurgery without any prophylaxis. The risk of DVT is poorly evaluated in head injured patients but is around 5%. Specific risk factors in neurosurgery are: a motor deficit, a meningioma or malignant tumour, a large tumour, age over 60 years, surgery lasting more than 4 hours, a chemotherapy. The benefit of mechanical methods or low molecular weight heparin (LMWH) for the prevention of DVP in neurosurgery is demonstrated (grade A). Each method decreases the risk by about 50%. A postoperative prophylaxis with a LMWH does not seem to increase the risk of intracranial bleeding (grade C). There is no demonstrated benefit to begin a prophylaxis with LMWH before the intervention. The duration of the prophylaxis is 7 to 10 days but this has not been scientifically determined.

Craniocerebral Trauma↗

PubMed2004

Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded hypoxic hypoxia.

While morphological and molecular events during angiogenesis in brain glioma have been extensively studied, the functional properties of tumour vessels have yet received little attention. We have determined changes in regional blood volume (BV) during graded hypoxic hypoxia using susceptibility contrast magnetic resonance imaging in a model of rat brain glioma. Nine anaesthetised and ventilated rats with C6 glioma were subjected to incremental reduction in the fraction of inspired oxygen (FiO(2)): 0.35, 0.25, 0.15, 0.12, 0.10 and reoxygenation to 0.35. At each episode, BV was determined in peritumoral, intratumoral and contralateral regions. Baseline BV values (FiO(2) of 0.35) were higher in peritumoral than in the contralateral and intratumoral regions. Progressive hypoxia resulted in a graded increase in BV in contralateral and peritumoral regions. At FiO(2) of 0.10, BV increases were comparable between these two regions: 49+/-22% (s.d.) and 28+/-17% with respect of control values, respectively. These BV changes reversed during the reoxygenation episode. By contrast, the intratumoral region had a significant increase in BV at FiO(2) of 0.10 only, with no evidence of return to the basal value during reoxygenation. Immunohistochemical staining of alpha-smooth muscle actin confirmed reactivity of vessels in the peritumoral region. Our findings indicate that peritumoral vessels present a vascular reactivity to hypoxia, which is comparable to that of nontumoral vessels. A method is thus available for noninvasively demonstrating whether any particular vascular modifying strategy results in the desired outcome in terms of tumour blood volume changes.

Animals↗

PubMed2004

[Sheehan's syndrome: an erratic diagnosis in the early postpartum].

Post-partum pituitary necrosis (Sheehan's syndrome) is a rare complication of the post-partum haemorrhage. The diagnosis can be erratic and often delayed. We report the case of a patient who had headaches and meningitis signs few hours after a post-partum haemorrhage. Magnetic Resonance Imaging (MRI) performed at day 2 showed a specific hypophysitis. The onset of asthenia, loss of weight, polyuro-polydipsy, persistent amenorrhoea and absence of lactation led to hormonal investigation. This permitted to diagnose global antehypopituitarism associated with diabetes insipidus. Progressive pituitary atrophy due to necrosis was found using MRI follow-up over 1 year. Our report summarises pathophysiological features of Sheehan's syndrome and early clinical and biological signs are discussed. MRI of the sellar region may be useful to early suspect the diagnosis.

Adult↗

PubMed2004

[Functional surgery for movement disorders: implications for anaesthesia].

Functional surgery for movement disorders is a recent stereotactic neurosurgical operation, restricted yet to patients with advanced Parkinson's disease or with generalized primary dystonia. One or two electrodes are implanted in the basal ganglia, namely in the globus pallidus pars interna or in the subthalamic nucleus, to realize a deep brain stimulation at high frequency. While this approach needs additional data to demonstrate clinical benefits, first results observed after short and long-term follow up are encouraging. Perioperative problems in patients with Parkinson's disease are possible respiratory disorders, a postoperative miss in medication doses and potential drug interactions with anaesthesia. The objectives of anaesthesia will be to allow stereotactic neurosurgical procedure, to maintain the upper airway patency and to be quickly reversible.

Anesthesia↗