Value of a single preoperative PFA-100 measurement in assessing the risk of bleeding in patients taking cyclooxygenase inhibitors and undergoing total knee replacement.
BACKGROUND
The usefulness of the PFA-100 in assessing the risk of bleeding in non-cardiac surgery is not clear. This study aims to examine this by correlating preoperative PFA-100 measurement with perioperative bleeding in patients receiving cyclooxygenase (COX) inhibitors.


METHODS
PFA-100 with adenosine-5'-diphosphate (ADPCT) and epinephrine (EPICT) cartridges were measured before operation in consecutive patients undergoing elective total knee replacement and taking different COX inhibitors. Surgery and anaesthesia were performed by the same team using standardized techniques. Intraoperative blood loss and postoperative drain output were recorded by anaesthetists and nurses blinded to the PFA-100 measurements. Surgeons, similarly blinded, were asked to rate the quality of haemostasis. Correlation was sought between these data and PFA-100 measurements.


RESULTS
Thirty patients were studied, involving 51 knees. Preoperative PFA-100 EPICT was correlated with drain output (r=0.30, P=0.03). The correlation becomes stronger when a 20% in vitro haemodiluted sample was used for measurement (r=0.42, P=0.01). Receiver-operating characteristic curve analysis using the diluted measurements [area under curve (AUC) 0.74 (95% CI 0.54-0.94)] suggested using a cut-off value of 188 s for EPICT, which will predict excessive drain output with 89% sensitivity, 54% specificity, and a likelihood ratio of 1.93. Diluted EPICT was also correlated with surgeon rating of haemostasis (r=0.36, P=0.04) although none of the measurements correlated with intraoperative blood loss.


CONCLUSIONS
Preoperative PFA-100 prolongation is correlated with increased postoperative drain output. It can be a potentially useful preoperative measurement in patients taking COX inhibitors.
Department of Anaesthesiology, The University of Hongkong, Room 424, Block K, Queen Mary Hospital Hongkong, Hongkong SAR, China. jkfng@hku.hk
K F J
KF
Ng
J-C
JC
Lawmin
S F
SF
Tsang
W M
WM
Tang
K Y
KY
Chiu
D000368:Aged; D000886:Anthropometry; D019645:Arthroplasty, Replacement, Knee; D016063:Blood Loss, Surgical; D016861:Cyclooxygenase Inhibitors / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010979:Platelet Function Tests / Q000295:instrumentation / Q000379:methods*; D019095:Point-of-Care Systems; D019106:Postoperative Hemorrhage / Q000097:blood* / Q000139:chemically induced; D011300:Preoperative Care / Q000379:methods*; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods; D016037:Single-Blind Method
D016861:Cyclooxygenase Inhibitors