Patient selection:
(1) elective cases >= 16 years of age
(2) exclusions: HIV, transplant, chemotherapy, metastatic cancer, major surgery within previous 6 weeks
(3) while not an exclusion criterion, no patients were ASA classes IV or V
The mean blood loss was 3.6 units, with the mean blood replacement 2 units. Blood loss was estimated by the difference in pre and postoperative hematocrits (divided by 3) and the total number of units transfused.
Risk factors for increased blood loss:
(1) male gender
(2) ASA class III
(3) general anesthesia
where:
• Comorbid conditions other than hypertension were infrequent.
• The method for estimating blood loss is subject to hemodilution from crystalloid infusion during surgery.
• Some surgeries were performed by residents and fellows in training, which was controlled for.
• Most of the replacements were done for osteoarthritis (71%) or rheumatoid arthritis (17%).
• 60% of the patients had the procedure done under local anesthesia only. 16% had general only and 24% had local plus general anesthesia (Table 2, page 169).
