Study: NCT01642147

Intervention type: DEVICE
Group type: ACTIVE_COMPARATOR
Intervention: Transcranial Doppler (TCD)
Description: A 2-MHz Transcranial Doppler probe (MULTI-DOP P2.2C; DWL, Elektronische Systeme GmbH, Germany) will be used to measure both sides of Vmca of both patients undergoing craniotomy and patients undergoing abdominal surgery. The signal will be range-gated to a depth of 45 to 60 mm at temporal bone window to achieve the optimal signal according to standard techniques. The measures will be recorded in the operation room before anesthesia, in the recovery room at extubation, 30, 60, 90, and 120 min after extubation.

Intervention type: DEVICE
Group type: EXPERIMENTAL
Intervention: Transcranial Doppler (TCD)
Description: A 2-MHz Transcranial Doppler probe (MULTI-DOP P2.2C; DWL, Elektronische Systeme GmbH, Germany) will be used to measure both sides of Vmca of both patients undergoing craniotomy and patients undergoing abdominal surgery. The signal will be range-gated to a depth of 45 to 60 mm at temporal bone window to achieve the optimal signal according to standard techniques. The measures will be recorded in the operation room before anesthesia, in the recovery room at extubation, 30, 60, 90, and 120 min after extubation.

Intervention type: PROCEDURE
Group type: EXPERIMENTAL
Intervention: jugular venous bulb catheterization
Description: After local anesthesia, a jugular venous bulb catheter(16G, manufactured by Arrow International Inc. USA) will be placed in the dominant side. The proper placement of the tip of the catheter in the jugular bulb will be confirmed later by a postoperative lateral skull X-ray. SjvO2 (blood sample will be drawn slowly at a speed of 2ml per minute) will be measured before anesthesia, at extubation, 30, 60, 90, and 120 min after extubation.

Intervention type: PROCEDURE
Group type: EXPERIMENTAL
Intervention: Tumor removal surgery under general anesthesia
Description: Surgery types include total or subtotal removal of tumors.For all surgical procedures, general anesthesia will be maintained with isoflurane (0.5-1.0 minimal alveolar concentration (MAC) expired), repeated boluses of fentanyl (1\~2 µg/kg IV), and continuous vecuronium 50～70 IV. All patients will be mechanical ventilated with oxygen. During anesthesia, blood pressure and heart rate will be kept stable, within ±10% of the preoperative levels. Hematocrit (Hct) will be maintained higher than 30%. After surgery, tracheal extubation will be performed when patients regain full muscle strength, breathe spontaneously with acceptable oxygenation and normocapnia.

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Radial artery catheterization
Description: After local anesthesia, an intra-arterial pressure line(I.V. catheter and pressure line kit are both manufactured by Smiths Medical International Ltd. USA) will be inserted in radial artery. Sample blood will be drawn from the line before anesthesia, at tracheal extubation, and 30, 60, 90, 120 min after tracheal extubation.

Intervention type: PROCEDURE
Group type: EXPERIMENTAL
Intervention: Radial artery catheterization
Description: After local anesthesia, an intra-arterial pressure line(I.V. catheter and pressure line kit are both manufactured by Smiths Medical International Ltd. USA) will be inserted in radial artery. Sample blood will be drawn from the line before anesthesia, at tracheal extubation, and 30, 60, 90, 120 min after tracheal extubation.

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Abdominal surgery under general anesthesia
Description: For all surgical procedures, general anesthesia will be maintained with isoflurane (0.5-1.0 minimal alveolar concentration (MAC) expired), repeated boluses of fentanyl (1\~2 µg/kg IV), and continuous vecuronium 50～70 IV. All patients will be mechanical ventilated with oxygen. During anesthesia, blood pressure and heart rate will be kept stable, within ±10% of the preoperative levels. Hematocrit (Hct) will be maintained higher than 30%. After surgery, tracheal extubation will be performed when patients regain full muscle strength, breathe spontaneously with acceptable oxygenation and normocapnia.