Increasing numbers of patients prescribed clopidogrel and aspirin are presenting for non-elective surgery. No consensus on the timing of surgery exists after withdrawal of antiplatelet and tests of platelet function are not routinely available. The Thrombelastography Platelet Mapping (TEG-PM) assay is designed to assess platelet inhibition secondary to antiplatelet therapy. We assessed its ability to detect platelet inhibition in preoperative acute surgical patients.
We conducted a prospective observational study in three groups of preoperative patients: those taking clopidogrel or aspirin up to admission, and a control group. TEG-PM was performed on the day of admission and alternate days until surgery.
Mean (SD) platelet thromboxane A(2) receptor inhibition in the control group was 17.5% (23.8) (n=20), 52.6% (32.3) (n=18) in the aspirin group, and 31.9% (27.6) (n=21) in the clopidogrel group (P<0.01). Mean (SD) platelet adenosine diphosphate (ADP) receptor inhibition in the control group was 47.8% (18.9) (n=20), 52.6% (19.7) (n=18) in the aspirin group, and 71.5% (18.4) (n=21) in the clopidogrel group (P<0.01). Among the clopidogrel group awaiting surgery, mean platelet ADP channel inhibition decreased on day 3 to 67.1% (24.7) (n=11), 48.8% (24.4) (n=4) on day 5, and 36.1% (15.9) (n=2) on day 7 (P=0.57).
TEG-PM can identify statistically significant platelet inhibition after antiplatelet therapy; however, the overlap in platelet receptor inhibition between the three groups is likely to limit the clinical usefulness of this test.
[Show abstract][Hide abstract] ABSTRACT: MEDICATION SAFETY Overlooked Renal Dosage Adjustments A retrospective analysis of 647 patients at hospital discharge com-pared required renal dosage adjust-ments to dosage actually prescribed. This study was conducted at VieCuri Medical Centre in Venlo, Netherlands. Patient demographics and renal function data were col-lected, and dosage adjustment needs were assessed via the pharmacy-supported discharge counseling ser-vice. The incidence of inappropriate dosing based on renal function was measured at hospital discharge. Thirty-seven percent of patients evaluated during the study period (237/647) had a creatinine clear-ance less than 51 mL/min/1.73 m 2 ; dosage adjustment was warranted in 23.9% (411/1,718) of prescrip-tions. When dosage adjustment should have been performed, more than 40% of prescriptions (169/411; 41.1%) were inappropri-ate for renal function (9.8% of pre-scriptions overall; 169/1,718). Fur-thermore, 60.4% (102/169) of inappropriate prescriptions pos-sessed the potential for moderate or severe clinical consequences, as evaluated by a panel of two clinical pharmacologists and one nephrolo-gist. Study authors also noted a lack of standardized dosing guidelines for agents requiring renal dosage adjustment. The authors also sug-gested that augmenting medication systems by adding dynamic renal dosing alerts would improve moni-toring. Summary: A comparison of suggested renal dosing and actual dosing at hospital discharge revealed that appropriate prescribing may be overlooked. van Dijk EA, Drabbe NRG, Kruijtbosch M, De Smet PAGM. Drug dosage adjust-ments according to renal function at hos-pital discharge. Ann Pharmacother. 2006;40:1254-1260.
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