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Objective: To assess the effects of various anesthetic techniques and PaCO

2

levels on cerebral oxygen sup-ply/consumption balance during craniotomy for removal of tumors

and to explore an anesthetic technique for neurosur-gery and an appropriate degree of PaCO

2

during neuroanesthesia. Methods: One hundred and fourteen patients withsupratentorial tumors for elective craniotomy

ASA grade Ⅰ-Ⅱ

were randomly allocated to six groups. Patients wereanesthetized with continuous intravenous infusion of 2% procaine 1.0 mg·kg

-1

·min

-1

in Group Ⅰ

inhalation of1.0%-1.5% isoflurane in Group Ⅱ

and infusion of 2% procaine 0.5 mg·kg

-1

·min

-1

combined with inhalationof 0.5%-0.7% isoflurane in Group Ⅲ during the period of study. The end-tidal pressure of CO

2

（PET CO

2

）was