Ethical approval for this study (No. 2010-58) was provided by the Biological-Medical Ethical Committee of West China Hospital, Sichuan University, Chengdu, Sichuan, China on 24 December 2010, and informed consent was obtained from each patient or their designated representatives at the preoperative visit (ClinicalTrials.gov Identifier: NCT01345643).
How to Use WCPTS
WCPTS is a dynamic score that to be assessed whenever the decision of allogeneic RBCs transfusion is needed, and it should be carried out when the patient's volume status is clinically normal assessed by senior clinicians.
CO is estimated clinically based on patient's hemodynamic and cardiac rhythm/rate. Assessment tools, such as central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP) or other CO monitoring could be applied for estimation of the CO. Patients with insufficient CO would be administered with adrenaline infusion (or equivalent conversion of other vasoactive agent infusion) to maintain the CO, and the adrenaline infusion rate will be included as points added in WCPTS. For other situations, such as bradycardia, hypotension or massive hemorrhage in which vasoactive drugs may be needed temporarily (for example, atropine, ephedrine, phenylephrine or noradrenaline), these vasoactive drugs will not be included during WCPTS assessment.
If SpO2 cannot be obtained or measured accurately with pulse oximetry, arterial blood gas analysis is recommended to measure the SaO2 value. Core body temperature may be measured at either nasopharyngeal, oropharyngeal, tympanic membrane, rectal or esophageal route. Temperature obtained by axillary route with 0.5℃ added can be accepted as core temperature.
The initial score is 7，and the final WCPTS score is the sum of all points plus 7, that is 7, 8, 9, 10, or >10. The score means the RBCs transfusion trigger and target of Hb level of 7, 8, 9, or 10 g/dl respectively, and the transfusion target is the same Hb level as the score. If WCPTS score ≥10, patients will be managed as if the WCPTS score is 10, which means Hb level should be maintained not less than 10 g/dl during perioperative period.
From 22 February 2011 through 11 February 2012, we enrolled patients in West China Hospital of Sichuan University and the First Affiliated Hospital of XinJiang Medical University. Telephone follow-up ended on 30 August 2012.
Patients aged 15 to 70 years, with both gender, American Society of Anesthesiologists (ASA) physical status I, II, III or IV, Glasgow Coma Scale (GCS) score of 15, undergoing elective spine surgery with estimated blood loss more than 800 ml or 20% of the patient's whole blood volume, were considered for inclusion. We excluded patients if they declined to undergo a blood transfusion or refused to sign consent, or had pregnancy, psychopathy, coagulopathy, impairment of communication or cognition, and other reasons that not suitable for this trial.
Treatment Assignment and Follow-Up
We randomly assigned patients to the WCPTS group or the liberal-strategy group using computer-generated random numbers, with the group assignments placed in sealed, consecutively numbered, opaque envelopes. After randomization, anesthesiologists, surgeons, and ward nurses were aware of study-group assignments, but the research nurses and statisticians participated in this trial were blind to group allocation.
In the WCPTS group, the Hb threshold of each patient for RBCs transfusion was set under the guidance of WCPTS. In the liberal-strategy group, the threshold was 10 g/dl, which means if the patient's Hb level was decreased less than 10 g/dl, RBCs transfusion should be given to the patient, and only to keep his Hb level not less than 10 g/dl.
During the perioperative period, whenever the senior clinicians had to decide upon RBCs transfusion, it's important to ensure that patient was normovolemic and Hb level was measured. Then decision on RBCs transfusion would be based on the group allocation. Hb level should be measured in 15 minutes after RBCs transfusion was completed. The mode of anesthesia, anesthetic drugs or their dosage, anesthetic management, anesthetic recording, surgery approach and intensive care unit (ICU) care were not restricted in this study. Decision of administration of fresh frozen plasma (FFP), platelet, cryoprecipitate, or other blood products was made by attending anesthesiologists or surgeons according to their own experience without restriction. Research nurses who were not involved in study implementation and were unaware of study-group assignments telephoned patients or proxies closely at 4, 8, 12, 16, 20, and 26 weeks after hospital discharge. They spoke directly to patients who were accessible by telephone or to proxies if patients were dead or could not talk on telephone.
The primary outcomes were the proportion of patients who received RBCs transfusion, and units of transfused RBCs.
Secondary outcomes included:
1. Hb level at different time points.
2. Death for any reason within 30 days postoperatively.
3. In-hospital complications, which included: (1) cardiac and pulmonary events such as cardiac arrest, arrhythmia, heart failure, pulmonary edema, etc.; (2) febrility without antibiotic treatment; (3) infection needed antibiotic treatment; (4) reoperation for bleeding; (5) deep venous thrombosis; (6) other complications.
4. Length of hospital stay and ICU stay.
5. Costs of hospitalization and transfusion.
6. Stitches removal time, which was defined as the time period (days) from the day of operation to the day of stitches removal.
7. Healing status of surgical incision, which was divided into grade I, II, and III. Grade I was defined as the wound healed nicely without any adverse reaction, grade II was defined as the inflammatory wound without the need of re-incision, and grade III was defined as the wound suppurated with the need of re-incision for clearance.
8. Time to get recovery of daily life and/or working, which was defined as the time period (weeks) from the day of discharge to the day that patient get recovery of normal daily life and/or working.
According to the primary outcome of the proportion of patients who received RBCs transfusion, we considered a difference of 25% (e.g. 50% vs. 75%) between the WCPTS group and the liberal-strategy group to be clinically important. Assuming a type I error protection of 0.05 and a power of 0.90, 77 patients in each group were required for a comparison within the group.
Analyses were performed with the use of SPSS 18.0 software. Data were expressed as mean ± standard deviation (with normal distribution) or median (with skewed distribution). Quantitative data were compared by using unpaired, two-tailed Student's t-test, qualitative data were analyzed by using the X2 test (Chi-square test), and data with skewed distribution were compared by the application of Mann-Whitney U test. A P value<0.05 was considered significant.