Measuring caffeine-induced changes in middle cerebral artery blood velocity using transcranial Doppler in patients recovering from ischaemic stroke

Abstract

Acute ingestion of caffeine is known to reduce cerebral blood flow in normal volunteers and in certain patient groups. There is no evidence that this causes problems in the normal population. However, there may be implications if a similar reduction occurs in patients recovering from an ischaemic stroke, in whom local blood flow has already been reduced. Transcranial Doppler provides a non-invasive method for measuring changes in middle cerebral artery (mca) blood velocity. A method for obtaining consistent. reliable measurements was developed and used in a double blind, randomized, crossover study on 20 patients (18 M, 2 F; mean age 70) recovering from ischaemic stroke in the mca territory. Middle cerebral artery blood velocity was measured bilaterally using transcranial Doppler before and after 250 mg caffeine (equivalent to about two cups of filter coffee) or matched placebo. Caffeine caused an average 12% reduction in blood velocity compared to placebo in the hemisphere affected by the stroke (95%c CI 8%-16%, p < 0.00001), and a 12% reduction in the non-affected hemisphere (95% CI 6%-18%, p < 0.001). The clinical implications are unclear at present, and imaging techniques will be required to establish whether caffeine does reduce flow to hypo-perfused regions.

Cerebral Autoregulation in Stroke

“…7,8,13 Finally, severe extracranial or intracranial artery stenosis and clinical conditions (eg, chronic hypertension, diabetes mellitus, and silent infarcts) may confound the assessment of cerebral autoregulation. 2,17,21,23,57 The effects of presence of collateral or cross-flow need to established in future studies. As an illustration, the finding of generally impaired autoregulation in lacunar stroke may be related to generalized small vessel disease attributable to chronic hypertension or diabetes.…”

“…Inclusion criteria were met by 14 controlled studies and 13 observational studies. Three studies were excluded because of unclear timing of measurements after stroke onset, [21][22][23] and 1 was excluded because TIA and minor stroke patients were grouped together. 24 Hence, 23 publications were eligible for review.…”

Comparison of caffeine-induced changes in cerebral blood flow and middle cerebral artery blood velocity shows that caffeine reduces middle cerebral artery diameter

“…We have already used TCD to show that 250 mg caffeine reduces Vmca by 13% in patients recovering from an ischaemic stroke in the middle cerebral artery (mca) territory (Lunt et al 2002). Caffeine of 250 mg is equivalent to two 150 ml cups of filter coffee or four cups of instant coffee or five to nine cups of tea depending on the brewing time (Bunker and McWilliams 1979).…”