Intravenous ketorolac tromethamine worsens platelet function during knee arthroscopy under spinal anesthesia

Ketorolac prolongs bleeding time and inhibits platelet aggregation and platelet thromboxane production in healthy, awake volunteers. However, platelet function was recently shown not to worsen after ketorolac was given during general anesthesia. The purpose of this study was to investigate platelet function changes during a standardized spinal anesthetic and surgery, as well as after a single intraoperative dose of intravenous (IV) ketorolac. The study comprised 30 ASA physical status I patients undergoing spinal anesthesia for knee arthroscopy. Subjects were randomized to receive either ketorolac 60 mg IV 15 min after skin incision or placebo IV. Platelet function testing consisted of an Ivy bleeding time, platelet aggregometry with adenosine diphosphate (ADP) and collagen, thromboelastography (TEG), and serum thromboxane B2 (TxB2) assays. Platelet function testing was performed: 1) 15 min prior to the performance of spinal anesthesia; 2) 10 min after surgical skin incision; and 3) 45 min after administration of study drug. The placebo group demonstrated no changes in any platelet function variable during spinal anesthesia and surgery relative to preoperative values. The ketorolac group, however, demonstrated a significant increase in bleeding time from postincision to poststudy drug data points (213 +/- 60s to 275 +/- 85s, mean +/- SD; P < 0.01). Further, platelet aggregometry to collagen was diminished in the ketorolac group from preoperative to poststudy drug data points (90.8% +/- 7.6% to 60.5% +/- 32.5%; P < 0.01). Platelet aggregometry with ADP, however, was unchanged in the ketorolac group. Platelet TxB2 production decreased dramatically in the ketorolac group from preoperative to poststudy drug data points (157.2 +/- 129.4 to 0.3 +/- 0.3 ng/mL; P < 0.01). Platelet function does not appear to be accentuated during spinal anesthesia as it is during general anesthesia. Unlike during general anesthesia, platelet function during spinal anesthesia is impaired, with respect to bleeding time and platelet aggregometry to collagen, by a single intraoperative dose of IV ketorolac.