....here information that what I hope fits to the overall image, it originates from a polish article "Surgery in J.W. our experiences" and after a long extensive discussion (read & click on the link) concludes that
"We found that abdominal surgeries in our small group of Jehovah's Witnesses patients were safe. However, two of our female patients agreed to blood transfusion in a “life or death” situation after serious discussion with them. The first woman was a middle-aged mother and the second older female patient underwent major abdominal surgery and developed postoperative complications.
In the section "Discussion" following is stated about the mentioned reports:
In 1977, Ott and Cooley reported on 542 cardiovascular operations ...
= report: https://www.ncbi.nlm.nih.gov/pubmed/302345 (link added by me)performed on Jehovah's Witnesses without blood transfusion and concluded that this procedure could be done “with acceptably low risk”. He (who?) also did a statistical review of 1,026 operations (REVIEW not REPORT is this relevant?) and determined that the risk of surgery in patients of the Jehovah's Witness group was not substantially higher than for others [6, 13]. Similarly, DeBakey communicated that in the vast majority of situations involving Witnesses, the risk of operation without the use of blood transfusions was no greater than in those patients on whom he used blood transfusions [6]. Jassar et al. developed a comprehensive multimodality programme for Jehovah's Witness patients and obtained excellent results in cardiac surgery. Based on their 10-year experience, they reported that bloodless cardiac surgery in Jehovah's Witness patients could be performed with excellent outcomes in both elective and urgent situations. Major complication rates were not significantly different between the elective group and the urgent group [14]. Similarly, Vaislic et al. reported their 21-year experience in cardiac surgery based on 500 Jehovah's Witness patients and concluded that cardiac surgery without transfusion in high-risk Jehovah's Witnesses patients could be carried out with results equivalent to those of low-risk patients thanks to recent advances in surgical techniques and blood conservation protocols [15].