To the Editor:
We describe the usefulness of the PFA II and P2Y12 assays in determining the residual antiplatelet activity of clopidogrel when neuraxial block is planned. The patient was a 68-year-old man who sustained a left femoral neck fracture and was scheduled for a hemiarthroplasty of the left side of the hip. He had a history of failed intubation because of his ankylosing spondylitis and placement of 3 bare metal coronary artery stents. He has been taking 75 mg of clopidogrel and 81 mg of aspirin daily since stent placement. The clopidogrel and aspirin were stopped 5 days before the surgery, although the patient was administered aspirin on the day of the surgery. Physical examination showed severely limited range of motion of his neck. His platelet count was 235,000/μL. The PFA II result was 87 seconds (reference range, 41-134 seconds). The P2Y12 assay showed 8% platelet inhibition and a platelet reaction unit (PRU) of 250 (reference range, 194-418). We performed spinal anesthesia with 12 mg of hyperbaric bupivacaine, which resulted in a sensory level of T4. He was brought to the post anesthesia care unit with a sensory level of T5, and there was complete sensory and motor recovery 3.5 hrs later. There was no bruising at the site of the spinal anesthesia, and the rest of his recovery was uneventful.
The American Society of Regional Anesthesia consensus guidelines recommend the discontinuation of clopidogrel for 7 days before a neuraxial injection. There is a case report of a caudal steroid injection 5 days after discontinuation of the clopidogrel; no test of platelet activity was performed before the injection.
1 In our patient, we performed a spinal anesthesia in view of the 8% platelet inhibition and a P2Y12 PRU that showed no residual antiplatelet activity of the clopidogrel. The numbers representing residual platelet reactivity (≥68 seconds for the PFA II and ≥264 P2Y12 PRU for the P2Y12 assay) were determined in 1267 patients by comparing the 2 assays with the light transmission aggregation test, the standard test for the determination of antiplatelet activity of drugs.
2 It was also noted that there was a better correlation of the P2Y12 assay with light transmission aggregation than the PFA test.
2 The PFA test cost $154.00, whereas the P2Y12 assay costs $459.00. Another test, the platelet mapping portion in the thrombelastography, has been used, but limitations in its clinical usefulness have been noted.
3 Our 1 case of an uneventful spinal anesthesia does not guarantee the safety of neuraxial injections 5 days after clopidogrel is stopped. If a neuraxial injection has to be performed before 7 days after clopidogrel is stopped, then either the PFA II or the P2Y12 assay, preferably the P2Y12 assay if available, should be considered to determine the residual antiplatelet activity of clopidogrel. Further studies are required to determine the clinical appropriateness of these tests.
Honorio T. Benzon, MD
Robert Fragen, MD
Hubert A. Benzon, MD
Jason Savage, MD
Jennifer Robinson, CRNA
Lalit Puri, MD
Departments of Anesthesiology and
Orthopaedic Surgery
Northwestern University
Feinberg School of Medicine
Chicago, IL