Stroke: Optimal cerebral perfusion pressure and oxygen content of brain tissue in aneurysmal subarachnoid hemorrhage

In order to prevent secondary injury after acute nerve injury, more and more attention has been paid to
the optimal cerebral perfusion pressure (CPPopt) for brain self-regulation.
Oxygenation of brain tissue (PbtO2) can identify cerebral blood flow insufficiency and secondary brain injury
.
Defining the relationship between CPPopt and PbtO2 after aneurysmal subarachnoid hemorrhage may lead to (1) mechanistic understanding of whether and how CPPopt-based strategies are beneficial, and (2) establishing support
for PbtO2 as an adjunct to adequate or optimal local perfusion.

A retrospective analysis of prospectively collected datasets of patients with aneurysmal subarachnoid hemorrhage from 2 centers, regardless of whether delayed cerebral ischemia (DCI)
was later diagnosed.
CPPopt is calculated as a cerebral perfusion pressure (CPP) value
corresponding to the lowest pressure responsiveness index (movement correlation coefficient of mean arterial pressure and intracranial pressure).
The relationship
between (hourly) deltaCPP (CPP-CPPopt) and PbtO2 was investigated using natural curve regression analysis.
Hypoxia in brain tissue is defined as PbtO2<20 mmHg
.

A total of 131 patients were enrolled, with a median CPPopt/PbtO2 data point
of 44.
0 (interquartile range, 20.
8-78.
3) hours.
The regression plot showed a nonlinear relationship between PbtO2 and deltaCPP (P<0.
001), with PbtO2 decreasing at deltaCPP<0mmHg and PbtO2 stable at deltaCPP≥0mmHg, although individual differences were large
.
Hypoxia in brain tissue (34.
6% of all measurements) was more frequent
at deltaCPP<0 mmHg.
These dynamic changes are similar
in patients with or without DCI.

In summary, in patients with subarachnoid hemorrhage of aneurysm, there is a nonlinear relationship between PbtO2 and the deviation of CPP and CPPopt.

A lower CPP value than the calculated CPPopt is associated with
lower PbtO2.
Nevertheless, the nature of PbtO2 measurements is complex and highly
variable.

References:

Optimal Cerebral Perfusion Pressure and Brain Tissue Oxygen in Aneurysmal Subarachnoid Hemorrhage.
https://doi.
org/10.
1161/STROKEAHA.
122.
040339Stroke.
2022;0