Association between brain tissue pH and brain injury during asphyxia in piglets.
BACKGROUND
Acidosis may contribute to brain injury from asphyxia, but its role is unclear. In order to evaluate the association between brain acidosis and cerebral injury, we subjected piglets to hypoxia and hypotension (HYP-HOTN) or hypoxia alone (HYP) to inflict varying amounts of brain damage. We hypothesized that piglets with a more severe brain injury would have a lower brain pH.


METHODS
Piglets had a pH microprobe inserted into the cerebral cortex. HYP animals breathed 5-8% O(2)/7% CO(2) for 30 min with mean arterial pressure (MAP) maintained at >40 mmHg. HYP-HOTN animals breathed the same gas for 30 min, but during the last 15 min, MAP was reduced to 25-30 mmHg by withdrawing blood. After 4 h of recovery, the animals were perfusion-fixed and pathology assessed. Somatosensory-evoked potentials (SEP) were also monitored.


RESULTS
HYP-HOTN piglets had more neuropathology than HYP animals. During the last 15 min of injury, brain pH in the HYP-HOTN group was significantly higher than that in HYP. However, recovery of brain pH was prolonged in the HYP-HOTN animals. The amount of time for brain pH to recover to > or =7.00 correlated very well with both the degree of neuropathology and SEP recovery. The reduction in brain pH, either absolute or relative to baseline, was not associated with the severity of damage.


CONCLUSIONS
The time needed for brain pH to recover after asphyxia, but not its severity, was associated with the amount of brain injury. Further study is warranted to determine whether immediate restoration of brain pH will reduce brain damage.
Bender
Thomas M
TM
Saint Louis University School of Medicine, Pediatric Research Institute, Cardinal Glennon Children's Hospital, St. Louis, MO 63104, USA.
Johnston
Jill A
JA
Manepalli
Anantha N
AN
Mink
Richard B
RB
D000138:Acidosis / Q000503:physiopathology*; D000704:Analysis of Variance; D000818:Animals; D001237:Asphyxia / Q000378:metabolism* / Q000503:physiopathology; D001812:Blood-Brain Barrier; D001921:Brain / Q000098:blood supply; D001930:Brain Injuries; D002545:Brain Ischemia / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D004195:Disease Models, Animal; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D011336:Probability; D011897:Random Allocation; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index