In addition to producing thrombocytopenia by suppressing platelet production, alcohol consumption can also cause platelet functional defects. The bleeding time is prolonged in chronic alcoholics even when the platelet count is normal. In vitro studies have shown that alcohol impairs platelet aggregation and thromboxane A 2 release. Platelet function returns to normal after two to three weeks of abstinence. In addition to a prolonged bleeding time, patients given the 70,000 MW dextran show evidence of red blood cell aggregation.
Management involves support until the dextran is excreted.
Transfused platelets are affected by the dextran in plasma. Carbenicillin and ticarcillin can inhibit platelet aggregation and contribute to a bleeding disorder, as can massive doses of penicillin. The clinical situation is particularly disconcerting when a platelet function defect that adds to the hemorrhage develops in a pancytopenic patient being treated for septicemia. Discontinuing the antibiotics or reducing the dose is a reasonable maneuver. This third-generation cephalosporin can cause a platelet function disorder after three to five days of therapy at a daily dosage of 4 g or more.