[Evaluation of cerebral hemodynamics by transcranial Doppler in anesthesia and reanimation].
Doppler technics are widely used for the investigation of the peripheral flows. The main objective of the method is to detect and quantify the vascular disease (stenosis, arterio-venous malformation) at the level of the carotid bifurcation or on the intracranial vessels. The spectral analysis provides informations on the velocity profile, and allows to quantify systolic, diastolic, and mean frequencies from which the usual haemodynamic parameters are determined. In case of vasospasm, the maximal frequency increases significantly (> 3 kHz). The amplitude of the diastolic flow is related to the vascular resistance. Vascular disease or distal vessel compression make the resistance increase; on the contrary vasodilation decreases the vascular resistance. The Doppler index R = S-D/S, with S and D the systolic and diastolic amplitude is generally accepted to change in proportion with the vascular resistance. The blood flow volume can be evaluated from the mean Doppler frequency, the vessel diameter, and the angle theta between the vessel and the Doppler beam. In case of intracranial arteries the diameter cannot be accurately measured by echography. Nevertheless if the diameter does not change and the angle theta remains constant, the variations of the mean frequency represent the blood flow volume changes. If there is a vasospasm, this method cannot be used, and the only possibility to evaluate the cerebral blood flow changes is to measure the variations of the common carotid blood flow or carotid mean frequency. The haemodynamic parameters are used in anesthesiology or in intensive care.(ABSTRACT TRUNCATED AT 250 WORDS)
Arbeille
P
P
Unité INSERM 316, Centre hospitalier et universitaire Trousseau, Tours.
Ades
P
P
Rastel
V
V
Legros
B
B
Jan
M
M
D000768:Anesthesia, General; D002536:Cerebral Arteries / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004453:Echoencephalography; D006439:Hemodynamics; D006801:Humans; D008991:Monitoring, Physiologic; D012151:Resuscitation / Q000379:methods*
Evaluation de l'hémodynamique cérébrale par Doppler transcranien en anesthésie et réanimation.