This study found a 39% decrease in perioperative blood loss during TKA surgery following preoperative administration of LIA compared to perioperative administration. No studies examining blood loss during TKA surgery with different protocols of LIA were available for comparison.
In this study, blood loss was measured by weighing saturated surgical cloths and measuring irrigation fluid to objectively measure blood loss, as opposed to estimation of blood loss through the use of a formula. Limitations include a possible methodical error in measurement of blood loss by weighing saturated surgical cloths, as blood absorbed by surgical drapes and lost on the floor was either not recorded or estimated by the surgical staff. However, this is likely only a fraction of the total blood loss, and the effects should therefore be similar in the intervention and control group. This is also compensated by the large sample size of this study. Estimating perioperative blood loss is difficult and this method was chosen to objectively quantify blood loss by means other than estimation. As the total blood loss is rarely large enough to significantly impact haemoglobin levels, estimating blood loss by calculating hemoglobin dilution was deemed unsuitable. Although this measurement may arguably not reflect the true blood loss of each patient, the margin of error should be approximately equal in all cases.
Tranexamic acid was administered intravenously twice during surgery for patients in both groups to reduce blood loss. While this may have decreased the total blood loss, the effects would be equal in both groups. It is possible that administration of a higher dose would have further reduced blood loss in both groups, rendering the effects of perioperative LIA non-significant. However, the use of tranexamic acid is not without risk, and preoperative LIA has the advantage of not only reducing blood loss but also providing postoperative pain relief.
No significant difference in self-reported pain 24 hours after surgery was found, hence this study suggests that preoperative LIA does not provide inferior postoperative pain relief compared to perioperative administration. All patients were given postoperative oral analgesic drugs (paracetamol as well as short- and long-acting oxycodone) according to the same protocol. Unfortunately, consumption could not accurately be assessed, in part because 18 patients were discharged during the first 24 hours after surgery. There are also various psychological factors affecting tendency to consume postoperative oral analgesic drugs, which this study was not designed to adjust for.
The decision of involving twelve different surgeons performing TKA was done to accurately mimic the clinical setting and for the results to be clinically relevant to the department. Although this may influence the results for any given patient, the randomized study design, as well as having a sample size in far excess of what was deemed necessary by the power analysis, should suffice for these differences to be negligible when comparing the intervention and control group. This also reflects the clinical reality of many emergency hospitals, and the results should therefore be applicable at other similar orthopaedic units and allow for a high degree of replicability.
Although this study demonstrates a decrease in perioperative blood loss, the clinical relevance of this finding is debatable as the mean total blood loss in both groups was 130 ml and 212 ml respectively. However, the trend towards shorter duration of surgery in the intervention group could potentially be due to less blood in the surgical field allowing for improved visualisation and shorter surgical time.