Systemic analysis of factors determining blood loss during total hip replacement

The authors analyzed intraoperative blood loss volume in 513 patients who had undergone total hip replacement in 1996-1999 for dystrophic-degenerative disease or injury sequels. Its seasonal and weekly changes were evaluated. It was found out that blood loss level depends upon two groups of factors: medical ones and those which are connected with external influences. The lowest "chronorisk" of excessive blood loss was found in July - November, the highest - from January till June (the maximal value being registered in March, and its decrease in May). The analysis of blood loss dynamics for 14 surgical teams demonstrated that 40% of them had the highest value of blood loss only on Thursdays, 30% - on Tuesdays; in 20% of the teams it had in an analogy with the average statistical model two peaks, namely on Thursdays and Tuesdays; and in 10% the peak was on Mondays. Thus, 80% of the surgical teams demonstrated circaseptan (around a week) and 20%- circahemiseptan (around half a week) periodicity of intraoperative blood loss oscillations. Basing on these findings one may assume that the "chronorisk" of excessive intraoperative blood loss increases on Tuesday and Thursday.