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Free Communications (Section D)
Author(s) -
D Bosone,
M Zaletel,
G Micieli,
S Marcheselli,
G Nappi
Publication year - 1995
Publication title -
journal of neuroimaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.822
H-Index - 64
eISSN - 1552-6569
pISSN - 1051-2284
DOI - 10.1111/jon19955s2s88
Subject(s) - medicine , hyperventilation , vasodilation , cerebral blood flow , middle cerebral artery , vascular resistance , cerebral circulation , blood pressure , anesthesia , mean arterial pressure , lumen (anatomy) , heart rate , hemodynamics , cardiology , ischemia
In TCD studies, the pulsatility index (PI), which is based on flow waveform analysis, are widely used for assessment of cerebral vascular resistance (CVR). However, PI is not very accurate, because it has many sources of variability and error. We propose a ratio between mean arterial pressure (MAP) and mean velocity (Vm) for an index of CVR. If we assume that the lumen of basal cerebral vessels is constant than MAPNm should be directly proportional to CVR. The aim of our study was to evaluate validity of MAPNm. For this purpose different vasodilatatory stimuli, which affected cerebral resistance and conductive vessels, were used. Hyperventilation (HV) and rebreathing (RE) change blood pCO2, which has predominantly an influence on resistance vessels. Clonidine, alfa‐adrenegic blocker, produce vasodilation on perifery. L‐arginine (L‐arg), precursor of nitro oxide, supposed to be able to induce vasodilatation of cerebral vessels. Nitroglicerinc (NTG) acts primarily on conductive vessels. Ten heathy subjects, both gender, aged from 21 to 57 years (mean 33.4+−11.9 years) participated in our study. HV and RE were performed using capnograph (Oxicap, Ohmeda) We registered end‐tidel (ET) CO2. Clonidin was administrated intramusculary at dose? L‐arg was infused at rate 5mg/kg/min for 30 minutes. NTG was applied sublingualy at dose 0.6 mg. The response of cerebral circulation was continously monitored by Multi‐dop X (OWL, Germany), usmg bitemporal probes for recording of Vm in middle cerebral artenes. Simultaneously the MAP and heart rate (HR) were sampled by pletysmographic device (Finapress. Ohmeda, USA).During RE MAP increased (p=.035), HR did not change, PI (p=.0006) and MAP/Vm (p=.0002) decreased. Dunng HV MAP decreased (p=014), HR increased (p=.048), PI (p=.0001) and MAPNm (p<0001) increased. We found good correlation between changes of PI and MAPNm (r=73, p<01) as well as between changes of MAP/Vm and ET CO2 (r=78, p<01) and moderate correlation between changes of PI and ET CO2 (r=53, p=016) After Clonidine administration MAP decreased (p<0001). HR did not change significantly,PI (p=.04) as well as MAP/Vm (p=.017) decreased. There was no correlation between PI and MAV/Vm. After L=arg infusion MAP and HR did not change, while PI (p<.001) and MAP/Vm (p<.001) decreased. No correlation between PI and MAP/Vm was found. After NTG MAP decreased (p=0.019), HR did not change as well as PI, while MAP/Vm (p=0084) mcrcased There was no correlation between PI and MAP/Vm