INTRAOPERATIVE CEREBRAL MICROEMBOLI DURING TOTAL KNEE ARTHROPLASTY – PRELIMINARY DATA

Abstract

To quantify the intraoperative cerebral microemboli load during primary total knee arthroplasty (TKA) using transcranial Doppler ultrasound and to investigate whether a patent foramen ovale influences cerebral embolic load in general.

Patients undergoing primary TKA, with no history of stroke, TIA, ongoing CNS disease or alcoholism were included. All operations were carried out under a standardised general anaesthetic and performed by two consultant orthopaedic surgeons. Microemboli l oad was recorded, using transcranial Doppler ultrasound (TCD), onto VHS tape for subsequent playback and analysis. Patent foramen ovale detection was performed using bolus intravenous injection of agitated saline followed by valsalva manoeuvre technique and TCD. Timing of specific surgical steps was recorded for each operation and emboli load calculated for that period.

Results: 50 TKA patients were studied (31 females, 19 males); 28 right and 22 left TKAs were performed. Cerebral microembolisation occurred in 19 patients (42%). Mean microembolic load was 3.56 per patient (range 0–21). PFO was detected in 9 patients (18%). Two thirds of PFO positive patients displayed cerebral microemboli. However, 36.6% (n=15) of PFO negative patients also displayed microemboli intraoperatively. Deflation of the tourniquet was followed by a larger microembolic load than the other phases of the operation.

Conclusion: Intraoperative cerebral microembolisation occurs in a significant proportion of patients during total knee arthroplasty. The presence of a patent foramen ovale does not appear to influence the incidence microemboli intraoperatively. Specific surgical activities are associated with generating greater embolic loads. These questions will be comprehensively assessed in the larger study currently underway.