Guidelines for blood transfusion have been issued for years. According to these guidelines, red blood cells (RBCs) transfusion should be given when the hemoglobin level is less than 6g/dL or 7g/dL and is unnecessary when the level is more than 10g/dL. However, in all the guidelines, the determination of whether RBCs should be administered when the hemoglobin level is in the range of 7~10g/dL is based on the judgment from anesthesiologists or surgeons. Index of transfusion trigger for patients with hemoglobin level between 7/dL and 10g/dL is necessary and important in clinical practice. Based on the aim of blood transfusion that maintain the balance of oxygen supply and oxygen consumption, the investigators hypothesize that index of transfusion trigger for patients with hemoglobin level between 7/dL and 10g/dL could be calculated by their history about heart and blood pressure, and routine monitoring parameters including pulse oximetry, temperature, and the use of vasoactive medications. To verify this hypothesis, the investigators present West China Perioperative Transfusion Score (WCPTS) for the trigger of transfusion according to the patient's history and monitoring parameters, and the investigators design a randomized controlled clinical trial to test this score.

Surgery and trauma are the most common reasons for major blood loss, and blood transfusion provide guarantee for massive hemorrhagic surgery, especially orthopedic, cardiac, liver, and gynecologic procedures. On the other hand, blood transfusion is associated with many risks including hemolytic and nonhemolytic reactions, transfusion related acute lung injury, and others. Besides, blood is insufficient worldwide. How to eliminate allogeneic blood transfusion is an important part in clinical practice.

Guidelines for blood transfusion have been issued by many health institutions or organizations in different countries. According to these guidelines, red blood cells (RBCs) transfusion should be given when the hemoglobin level is less than 6g/dL or 7g/dL and is unnecessary when the level is more than 10g/dL. However, in all the guidelines, the determination of whether RBCs should be administered when the hemoglobin level is in the range of 7~10g/dL is based on the judgment from anesthesiologists or surgeons on the patient's condition including intravascular volume status, ongoing bleeding, any risk factors for vital organs ischemia or hypoxia, and so on. Index of transfusion trigger for patients with hemoglobin level between 7/dL and 10g/dL is necessary and important in clinical practice.

The aim of blood transfusion is to provide sufficient oxygen for the whole body, and to maintain the balance of oxygen supply and oxygen consumption. Factors associated with oxygen supply are hemoglobin level, cardiac output (CO), and oxygen saturation. Oxygen consumption is increased by the increase of metabolism, which could be reflected by increase of heart rate, blood pressure, and body temperature. If a patient's oxygen supply is decreased or oxygen consumption is increased, he will need a higher hemoglobin level to maintain the balance. Based on these findings, the investigators hypothesize that index of transfusion trigger for patients with hemoglobin level between 7/dL and 10g/dL could be calculated by their CO (reflected by the use of adrenalin), and routine monitoring parameters including pulse oximetry and core temperature.

West China Perioperative Transfusion Score (WCPTS)

The initial score is 7.

If a patient's cardiac output (CO) is normal without continuous infusion of adrenalin, or his SpO2 is more than 95%, or his core temperature is less than 38℃, he doesn't have any bonus point factor, and his score is 7.

If a patient's CO is maintained in normal range by continuous adrenalin infusion with concentration of less than 0.05μg/kg.min, or his SpO2 is 85~94%, or his core temperature is 38~40℃, his score should be added 1 point for every item mentioned above.

If a patient's CO is only maintained by continuous adrenalin infusion with concentration of more than 0.05μg/kg.min, or his SpO2 is less than 84%, or his core temperature is above 40℃, his score should be added 2 points for every item mentioned above.

For example, if a patient's CO is normal, his SpO2 is more than 95%, and his core temperature is 39℃,his WCPTS should be calcultaed as 7 plus 1 (core temperature is 39℃), and his final score is 8.

Here's another example, if a patient's CO is normal, his core temperature is less than 38℃, but he has COPD and his SpO2 is less than 84%, his score could be calculated as 7 plus 2(SpO2 is less than 84%), and his final score is 9.

Value of SaO2 is evaluated 5min after endotracheal intubation with inhalation of compressive air.

The initial score is 7，and the patient's score is calculated by 7 plus the sum of every item.

Score 7：To maintain the patient's Hb level not less than 7g/dL

Score 8：To maintain the patient's Hb level not less than 8g/dL

Score 9：To maintain the patient's Hb level not less than 9g/dL

Score 10 or >10：To maintain the patient's Hb level not less than 10g/dL

Inclusion criteria

• Patients aged 15years to 70years.
• American Society of Anesthesiologists (ASA) physical status I, II, Ⅲ or Ⅳ.
• Undergoing elective spine surgery with estimated blood loss more than 800ml or 20% of the patient's whole blood volume.
• Glasgow Coma Scale (GCS) score of 15.
• Ability to communicate by telephone call.
• Informed consent has been signed by the patient or his legal guardian.

Exclusion criteria

• Declined to receive blood transfusion.
• Refuse to sign consent.
• Pregnancy.
• Psychopathy.
• Coagulopathy.
• Impairment of communication or cognition.
• Active participation in another trial where the primary endpoint follow-up is ongoing.
• Unwillingness or inability to comply with protocol procedures.