SUMMARY Measurement of intracranial arterial blood flow velocity is a new technique with potentially a number of very useful applications. This study validates the technique by comparing it to cerebral blood flow (CBF) measured using intravenous Xenon and extracranial clearance recording. We have measured the middle cerebral artery (MCA) blood flow velocity in 17 symptomatic patients with the EME TC 264 transcranlal Doppler velocimeter and compared these measurements to the ipsilateral hemispheric cerebral blood flow measured with an intravenous Xenon 133 technique (Novo Cerebrograph 10A). Measurements were made at rest and during hypercapnia.The absolute measurement of MCA velocity and hemispheric CBF showed a poor correlation (r = 0.424, p < 0.01) due to wide between-patient variations at rest but the blood flow response to hypercapnia, expressed as a reactivity index, showed a good correlation (r = 0.849, p < 0.001).Thus changes hi MCA velocity reliably correlate with changes hi cerebral blood flow but the absolute velocity cannot be used as an indicator of CBF.Stroke which has a number of potentially useful applications. It has been advocated as a method of peroperative monitoring during carotid endarterectomy when it can provide continuous on-line information about middle cerebral artery velocity, 2 ' 3 information of particular importance when the common carotid artery is clamped in deciding which patients need shunting.4 It may also be used to predict preoperatively whether or not the use of an indwelling shunt is necessary.3 Another use for the technique has been in the assessment of cerebrovascular spasm following subarachnoid hemorrhage 6 ' 7 and furthermore measurement of blood flow velocity in the middle cerebral artery, anterior cerebral artery and posterior cerebral artery combined with common carotid compression can provide information on the integrity of the Circle of Willis. 8 In an attempt to show that Doppler measured middle cerebral artery velocity corresponds to cerebral blood flow, a number of workers have performed hypercapnia stress tests and measured the resulting increase in middle cerebral artery velocity. "11 However, this only provides indirect proof of the validity of these measurements. Therefore, we have measured the response to hypercapnia of both the middle cerebral artery velocity and the cerebral blood flow measured with an intravenous Xenon 133 technique. A good correlation between the two methods would provide direct evidence that middle cerebral artery velocity changes actually reflect changes in cerebral blood flow. Methods PatientsIn order to get a wide spread of response to hypercapnia, we have studied 17 symptomatic patients with Received December 18, 1985; accepted January 23, 1986. cerebrovascular disease aged between 41 and 70 years (mean 61); providing 34 middle cerebral arteries for study. In 11 instances, the ipsilateral internal carotid artery was totally occluded and in the remaining 23 was patent. Measurement of MCA VelocityThe probe of the EME TC 264 2...
PurposeStroke volume (SV) is a parameter that is being recognized as an endpoint in fluid resuscitation algorithms. Its role is now being realized as an important variable in hemodynamic assessment in various clinical scenarios such as septic and cardiogenic shocks. Direct measurement of stroke volume (SV) and its novel corollary, stroke volume variation (SVV) derived by proprietary software, are preferred over mean cardiac output (CO) measurements because they render a more accurate reflection of hemodynamic status independent of heart rate. Flotrac-Vigileo monitor (FTV) (Edwards Lifesciences, Irvine, CA, USA) is a system that uses a complex algorithm analyzing arterial waveform to calculate SV, SVV, and CO. We assessed the feasibility of obtaining SV measurements with a portable echocardiogram and validated its accuracy with the FTV system in mechanically ventilated patients in our intensive care unit (ICU). Furthermore, we emphasized the importance of hemodynamic measurements and familiarity with critical care echocardiography for the intensivists.MethodsTen patients who were on mechanical ventilation were studied. A femoral arterial line was connected to the FTV system monitoring SV and CO. A portable echocardiogram (M-Turbo; Sonosite, Bothell, WA) was used to measure SV. CO was calculated by multiplying SV by heart rate. No patient had arrhythmia. We used biplane Simpson’s method of discs to calculate SV in which subtraction of end-systolic volume from end-diastolic volume yields the SV.ResultsThe comparison of simultaneous SV and CO measurements by echocardiography with FTV showed a strong correlation between the 2. (For SV, y = 0.9545x + 3.3, R2 = 0.98 and for CO, y = 0.9104x + 7.7074, R2 = 0.97).ConclusionsIn our small cohort, the SV and CO measured by a portable echocardiogram (Sonosite M-Turbo) appears to be closely correlated with their respective values measured by FTV. Portable echocardiography is a reliable noninvasive tool for the hemodynamic assessment of the critically ill. Its results need further validation with gold standard measures in a larger cohort of patients. However, our results suggest portable echocardiography could be an attractive tool in assessment of different hemodynamic scenarios in the critically ill.
A double blind placebo-controlled clinical trial was undertaken to investigate the effect of 500 mg bd of Paroven taken for four weeks on the tissue oxygenation, ankle oedema and calf pump function of 48 patients with chronic venous disease. There was no evidence that Paroven reduced ankle swelling or improved calf pump function, but it did cause a significant improvement in transcutaneous oxygen levels measured in the calf skin of the ulcer hearing area ( p = 0.026) which was confirmed when the oxygen levels of the active and placebo treated groups were compared at the end of four weeks treatment ( p = 0.02). This improvement in tissue oxygenation may be the result of alterations in the capillary exchange produced by the drug and may account for the symptomatic benefit associated with its use.
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