Influence of moderate and profound hyperventilation on cerebral blood flow, oxygenation and metabolism.
OBJECTIVE
The aim of the present study was to examine the impact of moderate and profound hyperventilation on regional cerebral blood flow (rCBF), oxygenation and metabolism.


METHODS
Twelve anesthetized pigs were subjected to moderate (mHV) and profound (pHV) hyperventilation (target arterial pO(2): 30 and 20 mmHg, respectively) for 30 min each, after baseline normoventilation (BL) for 1 h. Local cerebral extracellular fluid (ECF) concentrations of glucose, lactate, pyruvate and glutamate as well as brain tissue oxygenation (p(ti)O(2)) were monitored using microdialysis and a Licox oxygen sensor, respectively. In nine pigs, regional cerebral blood flow (rCBF) was also continuously measured via a thermal diffusion system.


RESULTS
Both moderate and profound hyperventilation resulted in a significant decrease in rCBF (BL: 37.9+/-4.3 ml/100 g/min; mHV: 29.4+/-3.6 ml/100 g/min; pHV: 23.6+/-4.7 ml/100 g/min; p<0.05) and p(ti)O(2) (BL: 22.7+/-4.1 mmHg; mHV: 18.9+/-4.9 mmHg; pHV: 13.0+/-2.2 mmHg; p<0.05). A p(ti)O(2) decrease below the critical threshold of 10 mmHg was induced in three animals by moderate hyperventilation and in five animals by profound hyperventilation. Furthermore, significant increases in lactate (BL: 1.06+/-0.18 mmol/l; mHV: 1.36+/-0.20 mmol/l; pHV: 1.67+/-0.17 mmol/l; p<0.005), pyruvate (BL: 46.4+/-7.8 micromol/l; mHV: 58.0+/-10.3 micromol/l; pHV: 66.1+/-12.7 micromol/l; p<0.05), and lactate/glucose ratio were observed during hyperventilation. (Data are presented as mean+/-S.E.M.)


CONCLUSIONS
Both moderate and profound hyperventilation may result in insufficient regional oxygen supply and anaerobic metabolism, even in the uninjured brain. Therefore, the use of hyperventilation cannot be considered as a safe procedure and should either be avoided or used with extreme caution.
Department of Anesthesiology and Intensive Care Medicine, Martin Luther University Halle-Wittenberg, Ernst-Grube-Str. 40, Halle/Saale, 06120, Germany. tobias.clausen@medizin.uni-halle.de
Tobias
T
Clausen
Alexander
A
Scharf
Matthias
M
Menzel
Jens
J
Soukup
Carsten
C
Holz
Andreas
A
Rieger
Frank
F
Hanisch
Endre
E
Brath
Norbert
N
Nemeth
Iren
I
Miko
Peter
P
Vajkoczy
Joachim
J
Radke
Dirk
D
Henze
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006985:Hyperventilation / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D013552:Swine