Brain glucose and lactate levels during ventilator-induced hypo- and hypercapnia.
OBJECTIVE
Levels of glucose and lactate were measured in the brain by means of microdialysis in order to evaluate the effects of ventilator-induced hypocapnia and hypercapnia on brain metabolism in healthy non-brain-traumatized animals.


METHODS
Prospective animal study in a university laboratory.


METHODS
Eight adult Landrace/Yorkshire pigs.


METHODS
The microdialysis probe was inserted in the brain along with a multiparameter sensor and intracranial pressure (ICP) probe. The animals were ventilated in a pressure-controlled mode according to the open lung concept with an inspired oxygen fraction of 0.4/1.0. Starting at normoventilation (PaCO(2) +/-40 mmHg) two steps of both hypercapnia (PCO(2) +/- 70 and 100 mmHg) and hypocapnia (PaCO(2) +/- 20 and 30 mmHg) were performed. Under these conditions, brain glucose and lactate levels as well as brain oxygen (PbrO(2)), brain carbon dioxide (PbrCO(2)), brain pH (brpH), brain temperature and ICP were measured.


RESULTS
At hypercapnia (PaCO(2) = 102.7 mmHg) there were no significant changes in brain glucose and lactate but there was a significant increase in PbrCO(2), PbrO(2) and ICP. In contrast, at hypocapnia (PCO(2) = 19.8 mmHg) there was a significant increase in brain lactate and a significant decrease in both brain glucose and PbrCO(2).


CONCLUSIONS
Hypocapnia decreases brain glucose and increases brain lactate concentration, indicating anaerobic metabolism, whereas hypercapnia has no influence on levels of brain glucose and brain lactate.
van Hulst
R A
RA
Department of Anesthesiology, Erasmus Medical Center Rotterdam, 3000 DR Rotterdam, The Netherlands.
Lameris
T W
TW
Haitsma
J J
JJ
Klein
J
J
Lachmann
B
B
D000818:Animals; D001921:Brain / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000032:analysis; D006935:Hypercapnia / Q000209:etiology / Q000378:metabolism*; D016857:Hypocapnia / Q000209:etiology / Q000378:metabolism*; D007773:Lactates / Q000032:analysis; D008297:Male; D023421:Models, Animal; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects*; D013552:Swine
D007773:Lactates; D005947:Glucose