Moderate hyperventilation during intravenous anesthesia increases net cerebral lactate efflux
Frank Grüne1, Stephan Kazmaier, Hans Sonntag
1From the Department of Anesthesiology, Erasmus MC, Rotterdam, The Netherlands (F.G., R.J.S.); Department of Anesthesiology, Critical Care, and Emergency Medicine, University of Göttingen, Göttingen, Germany (S.K., H.S.); and Department of Anesthesiology, Critical Care, Emergency, and Pain Medicine, Klinikum Oldenburg, Oldenburg, Germany (A.W.).
Anesthesiology
|September 7, 2013
Summary
Moderate hyperventilation significantly reduces cerebral blood flow (CBF) and oxygen delivery during anesthesia. This leads to increased cerebral lactate efflux, indicating potential impairment of aerobic metabolism in patients undergoing surgery.
Area of Science:
- Anesthesiology
- Neuroscience
- Cardiovascular Surgery
Background:
- Hyperventilation is known to reduce cerebral blood flow (CBF) and impair cerebral metabolism.
- The specific threshold for these effects during intravenous anesthesia is not well-established.
Purpose of the Study:
- To investigate the impact of moderate hyperventilation on cerebral blood flow and metabolism in patients under intravenous anesthesia.
- To determine if reduced CBF during hyperventilation impairs cerebral aerobic metabolism.
Main Methods:
- A prospective, controlled crossover trial involving 30 male patients undergoing coronary surgery under fentanyl-midazolam anesthesia.
- Measurements included global CBF (using a modified Kety-Schmidt technique), middle cerebral artery blood flow velocity (transcranial Doppler), and cerebral metabolic rates for oxygen, glucose, and lactate at partial pressures of carbon dioxide of 30 mmHg and 50 mmHg.
Main Results:
- Moderate hyperventilation (PaCO2 30 mmHg) significantly decreased CBF by 60% and middle cerebral artery velocity by 41%.
- Cerebral oxygen delivery was reduced by 58%, and jugular venous oxygen partial pressure decreased by 45%.
- While cerebral metabolic rates for oxygen and glucose remained unchanged, net cerebral lactate efflux significantly increased, suggesting anaerobic metabolism.
Conclusions:
- Moderate hyperventilation markedly reduces CBF and jugular venous oxygen partial pressure in patients with cardiovascular disease undergoing intravenous anesthesia.
- The increased cerebral lactate efflux suggests a partial impairment of cerebral aerobic metabolism at clinically relevant hypocapnic levels.
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