Effects of Caffeine on Cerebral Blood Flow
Condition: Cardiovascular System
Study type: Interventional

Summary: 
      The goal of this clinical trial is to evaluate in clinically healthy young people if:

        -  after caffeine ingestion, there are variations in blood velocity of the middle cerebral
           arteries (VMCA),

        -  this variation is dependent on the administered dose.

      Transcranial Doppler ultrasonography was used to record blood VMCA in three groups of 15
      clinically healthy young adults each - no caffeine, low caffeine (45 mg) and high caffeine
      group (120 mg). Transcranial Doppler ultrasonography provided simultaneous bilateral VMCA
      measurements while subjects performed functional tests (hyperventilation and hypoventilation
      orders) and three cognitive activities (Test 1, short-term remembering, Test 2, solving a
      vocabulary problem, and Test 3, solving a math problem) each in 31-second tests with 1-minute
      rest between them. Participants were assessed before and 30 minutes after caffeine ingestion.
    

Detailed description: 
      Were used in the study, Capsules dosed with 45mg and 120 mg of anhydrous caffeine and flour
      capsules as a placebo. In the preparation of the capsules, a semi-automatic capsulator No. 0
      (Capsunorm® by Tecnyfarma®) were used, colorless hard gelatin capsules No. 0 by Acopharma®
      and anhydrous caffeine (Biochem®, C.A.S. 58-08-2).

      Viasys Sonara transcranial Doppler unit and a 2 MHz probe were used to sample the middle
      cerebral artery at depths of 60 millimeters, using emission doppler pulsed performing
      spectral analysis in real time. Two probes (bilaterally) of 2MHz were placed at a depth
      between 55 and 60 mm, thus making it possible to analyse both middle cerebral arteries
      simultaneously.

      Each participant was asked not to ingest caffeine and exercise vigorously for at least 12
      hours before the assessment. In the case of smokers, they were also asked not to smoke for at
      least 2 hours before the evaluation. The laboratory had medium luminosity, silent and
      controlled temperature (23º/24ºC). To avoid inter-observer errors, all examinations were
      performed by the same investigator who was not aware of what dose was/had been administered
      to the participant.

      Subjects were tested while seated in a reclining chair located in a dimly lit,
      sound-attenuated room and performed the activities with their eyes closed.
    

Intervention name(s): Placebo; Anhydrous caffeine (45mg); Anhydrous caffeine (120mg)
Intervention type(s): Other; Other; Other
Intervention description(s): Flour capsules as a placebo.; Capsules dosed with 45mg of anhydrous caffeine.; Capsules dosed with 120mg of anhydrous caffeine.
Intervention MeSH terms: Caffeine
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: All subjects were submitted to 2 evaluation moments: the first baseline moment and the second moment, 30 minutes after caffeine ingestion, which constitutes the time required for caffeine absorption.
In each of the 2 moments, they performed 30 seconds of continuous breathing (hypoventilation), followed by 30 seconds of continuous rapid breathing (hyperventilation). VMCA measurements were stabilized between these tests. The study started with apnea testing because VMCA requires less time to return to baseline levels after hypoventilation than after hyperventilation.
When VMCA measurements were stable, a 30-second baseline period was followed by three 30-second cognitive tasks, with a 1-minute break between activities: short-term memory test; solve a vocabulary problem; and solving a math problem. Three versions of each cognitive task were used for the three conditions. The procedure was completed with a final rest period of 60 seconds.
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Transcranial Doppler ultrasonography; Middle Cerebral Artery; functional tests; cognitive activities; caffeine