Changchun / China - In randomized controlled study in Neurology (2019; doi:), inflating blood pressure cuff 4 times and then emptying it for 5 minutes improved the blood flow in the brain for up to 24 hours and increased it led by 2 neuroprotective substances in the blood.
Inflating blood pressure cuff creates ischemia in the extremity. The lack of oxygen and glucose leads to the release of protective factors into the blood, which, once the blood pressure has been eliminated, also affect other regions of the body.
Physiologists refer to the procedure as "remote ischemic preconditioning" or RIPC and it is already being tested at some heart centers to prepare patients for major operations. The neuroprotective factors are supposed to protect the heart muscle. In fact, postoperatively, patients experience smaller increase in troponin, marker for damage to heart muscle cells.
A protective effect on the brain is also conceivable. In an earlier study from Denmark, RIPC was used in conjunction with stroke lysis therapy. However, no influence on the size of the infarct could be demonstrated (). Chinese researchers had previously reported that RIPC significantly reduced the risk of recurrence after stroke (). However, the study was small and the therapy has not yet been taken up by other centers.
A team led by Yi Yang from Jilin University in Changchuh has now conducted randomized clinical study on the physiological effects of RIPC on cerebral blood flow 50 healthy people (mean age 35 years) were examined. Blood pressure cuffs were placed on the upper arm and thigh of the participants and inflated for 5 minutes to such an extent that no fresh blood could get into the arteries. This maneuver was repeated 4 times after 5-minute break.
The flow velocity in the left and right middle cerebral artery was determined several times over the following 24 hours. Initially, no changes were found. But after 6 hours there was an increase in blood flow, which continued until the end of the observation period after 24 hours.
The laboratory tests showed that just one hour after the RIPC maneuver, there was an increase in 2 substances in the blood which, as biomarkers, could explain the subsequent effects on cerebral blood flow.
This was once VEGF-A ("vascular endothelial growth factor-A"). VEGF-A stimulates the production of nitric oxide in the vessel wall, which leads to vasodilation (vasodilation).The second factor was GDNF ("glial cell line-derived neurotrophic factor"), which has neuroprotective effect, for example in Parkinson's disease or epilepsy. According to Yang, the concentration of GDNF rose on average from 0.289 to 0.789 pg / ml within the first hour after the maneuver.
There was also an increase in 4 known inflammation markers TGF-beta1, LIF, MMP-9 and TIMP-1, while fifth inflammation marker (MCP-1) decreased. The differences were significant, but since Yang examined total of 30 biomarkers, an incidental finding cannot necessarily be ruled out. In addition, only single blood test was performed.
Another limitation is that the younger participants probably had healthy cerebral arteries. The results cannot therefore necessarily be transferred to older people with an increased risk of stroke. It remains to be seen whether the idea will be taken up and the utility of RIPC for the treatment of stroke or for secondary prevention will be tested in larger clinical studies.