The added value of virtual reality technology and force feedback for surgical training simulators.

Laparoscopic surgery requires more specialized training of the surgeons than traditional open surgery. The Virtual Basic Laparoscopic Surgical Trainer (VBLaST) is being developed as a virtual version of the Fundamentals of Laparoscopic Skills (FLS) trainer. This study assessed the current haptic and virtual reality (VR) technology of a virtual peg transfer task of the VBLaST, based on the subjective preference of surgeons and their objective task performance measures. Twenty-one surgical residents, fellows and attendings performed a peg-transfer task in the FLS and the VBLaST. Each subject performed 10 trials on each simulator. Results showed that subjects performed significantly better on the FLS than on the VBLaST. Subjects showed a significant learning effect on both simulators, but with an accelerated improvement on the VBLaST. Even so, 81% of the subjects preferred the FLS over the VBLaST for surgical training which could be attributed to the novelty of the VR technology and existing deficiencies of the haptic interface. Despite the subjective preference for the physical simulator, the performance results indicate an added value of VR and haptics in surgical training, which is expected to be demonstrated in more surgically relevant tasks such as suturing and knot-tying.

[Protective effects of Ginkgo biloba extract on the early rupture of the hemato-encephalic barrier in the rat]. / Effets protecteurs de l'extrait de Ginkgo biloba sur la rupture précoce de la barrière hémoencéphalique chez le rat.

During the hours immediately following an hypertensive burst or a cerebral ischemia induced by the intracarotid administration of microspheres, damage to the blood brain barrier can be observed with molecules of low molecular weight, such as angiotensin, whereas albumin or large proteins will not yet have been able to cross over and there is virtually no edema. Gingko biloba extract causes the brain uptake index of angiotensin hypertensive animals. This effect is proportional to the dose of extract used (500-100 mg/kg). A similar effect can be observed in animals showing embolism in one hemisphere. The process can therefore doubtlessly be explained by the stabilizing effect of Ginkgo biloba on membranes.

Simultaneous study of haemodynamic, metabolic and behavioural sequelae in a model of cerebral ischaemia in aged rats: effects of nicergoline.

Unilateral cerebral ischaemia was induced in 18-month-old Long-Evans rats by injection of 2,000 labelled microspheres (phi 50 microns) into the carotid blood stream. This results in an ipsilateral decrease in cerebral blood flow, development of severe oedema and modifications of glucose uptake and consumption. Furthermore, this ischaemia led to a deterioration of the avoidance response in conditioned animals. All these disturbances, including the cerebral oedema, diminished with nicergoline pretreatment.

Effects of naftidrofuryl on cerebral hemodynamics, metabolism and function after a retracted ischaemia.

Unilateral microemboli were formed in the brains of Long Evans rats by means of an intracarotid injection of microspheres (50 mu). This embolization resulted in a decrease in blood flow, severe cerebral oedema and a modification of glucose uptake. Furthermore, these microemboli affected a conditioned avoidance response. Naftidrofuryl enabled a better recovery of the processes involved in the expression of acquisition. This has been related to a decrease in the development of oedema on one side and to a better glucose uptake on the other. These data demonstrated that naftidrofuryl influences the sequelae of rapidly regressive ischaemia.

[Cerebral blood flow metabolism and behavior following cerebral infarction in the awake rat (author's transl)]. / Conséquences d'un infarctus cérébral chez le rat vigile, sur le débit sanguin cérébral, le métabolisme et le comportement.

In the awake rats, a cerebral ischemia was performed by means of 2,000 microspheres administered into the internal carotid via a chronic catheter. After a coma lasting for a few minutes and a 24-48 h palsy, the Long Evans rats gradually recover a normal behavior. The acquisition of an avoidance response is deeply disturbed by microembolization but the capacities of memorization reappeared with the regression of oedema. 7 days after embolization, the cerebral blood flow in ischemized hemisphere was still significantly decreased, and in spite the glucose consumption was identical in ischemized and non ischemized side. This latter parameter is a better index of the cell activity. This model in the awake rat was proposed for the study of molecules used in cerebral ischemia without interference of anesthetics drugs.

Short-term memory and cerebral ischemia: pharmacological application.

Transient ischemia results in changes in the cerebral blood flow at the level of microinfarcts, enzymatic and metabolic changes and the development of a cerebral edema; all these disorders regress in the week following ischemia. Besides, the observed functional disorders disappear as the cerebral edema regresses. The brain functional activity is protected by the use of treatments which reduce the development of the cerebral edema and/or a quicker regression of the edema.

[Cerebral blood flow, metabolism and learning after a cerebral infarction in the rat (author's transl)]. / Débit cérébral, métabolisme et comportement a la suite d'un infarctus cérébral chez le rat.

Experimental microembolization of the rat brain has been used as a model for the production of cerebral microinfarction which resulted in a decrease in blood flow and secondary brain edema with changes in the oxidative metabolic pathways. The use of radioactive microspheres as embolizing agents allowed to determine the number of microinfarctions and their localization. In every microinfarct, oedema developed and it could be quantified by measuring the water percentage as soon as the fourth hour following the microembolization. The activity of oxygen-dependent enzymes was severely reduced in the ischemic area around which hyperemia was present. A quick decrease in the ATP and glucose levels and an increase in the lactate levels were observed, showing that the energetic metabolism was deviated towards the anaerobic pathway. On the fifth day following the microembolization, the oedema disappeared. The cellular metabolic activity and the cerebral blood flow almost returned to normal values within the same time. The simultaneously study of an avoidance response in a conditioned learning test showed a correlation between the reappearance of this response and the regression of the oedema.