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Detection and differentiation of cerebral microemboli in patients undergoing major orthopaedic surgery using transcranial Doppler ultrasound

Background
Cerebral microemboli (ME) are frequently generated during orthopaedic surgery and may impair cerebral integrity. However, the nature of cerebral ME, being either of solid or gaseous origin, is poorly investigated. Our primary aim was to determine both the frequency and nature of cerebral ME in generally anaesthetised patients undergoing major orthopaedic surgery.


Methods
Fifty patients (hip/knee/shoulder prosthesis, spine surgery) were enrolled. Cerebral ME and cerebral blood flow velocity (CBFV) were determined in both middle cerebral arteries for 15 min preoperatively and postoperatively, using transcranial Doppler ultrasound. Cerebral tissue oxygen index, determined by near-infrared spectroscopy, was further examined. Statistical analysis was carried out using the Wilcoxon matched-pairs signed-ranks test (median (25 th ; 75 th percentile), P  < 0.05).


Results
Overall the frequency of postoperative cerebral ME rose to 600% of preoperative values. Primarily gaseous ME occurred preoperatively and postoperatively [19 (6; 63) vs 116 (24; 373), P  < 0.001], while the number of solid ME was negligibly small [1 (0; 2) vs 2 (0; 6), P  < 0.001]. CBFV and cerebral tissue oxygen index remained unaltered bilaterally before and after surgery.


Conclusions
Our findings indicate that cerebral ME considerably increase after major orthopaedic surgery under general anaesthesia. The predominant accumulation of gaseous ME and their preoperative occurrence, suggest that the general anaesthesia and individual patient factors may contribute to the embolic load in addition to orthopaedic surgery.


Clinical trial registration
. NCT02340416.