Influence of COX-inhibiting Analgesics on the Platelet Function of Patients with Subarachnoid Hemorrhage

Background: Platelet function of patients with subarachnoid hemorrhage (SAH) may play an important part in both rebleeding and delayed cerebral ischemia, but little is known about aggregation pathways during the acute phase of stroke. Analgesics are used regularly in the first days after bleeding, and some can potentially inhibit the cyclooxygenase (COX) enzyme. We examined the platelet function of patients with SAH in order to describe their basal situation and determine whether the administration of intravenous nonsteroidal antiinflammatory drugs (NSAIDs) affected platelet aggregation. Methods: Arachidonic acid (AA)-induced aggregation and the platelet function analyzer (PFA)-100 test with collagen/epinephrine cartridges were used to study a group of SAH patients that was treated with dexketoprofen and dipyrone and to compare them to patients that had received no analgesia. Results: Ninety-six consecutive SAH patients prospectively enrolled in platelet studies. Twenty-seven patients were taking NSAIDs (10 on dexketoprofen and 17 on dipyrone), and there were 15 cases in the control group. AA-induced aggregation was 10% +/- 3.2% for NSAIDs (mean +/- standard error), specifically 17.2% +/- 7% for dexketoprofen and 5.7% +/- 1% for dipyrone. Aggregation in the control group was 72.4% +/- 6% (P = .001). Both analgesics slowed the platelet plug formation during the PFA-100 test, with closure times of 237.2 +/- 25 seconds for dexketoprofen and 198.4 +/- 22 seconds for dipyrone and 138.1 +/- 21 seconds in controls (P=.02). Conclusions: The administration of COX-inhibiting analgesics leads to an hypoaggregability state in the first days of SAH. Further insight into their impact on complications such as rebleeding and delayed cerebral ischemia is needed in order to optimize the headache treatment of SAH.