There was a lower incidence of HIT and HIT complicated by VTE in postoperative patients undergoing thromboprophylaxis with LMWH compared with UFH. This is consistent with the current clinical use of LMWH over UFH as front-line heparin therapy. However, conclusions are limited by a scarcity of high quality evidence. We did not expect the paucity of RCTs including HIT as an outcome as heparin is one of the most commonly used drugs worldwide and HIT is a life-threatening adverse drug reaction. To address the scarcity of clinically-relevant information on the topic of HIT as a whole, HIT should be included as an outcome in future RCTs of heparin, and HIT as an adverse drug reaction should be considered in clinical recommendations regarding monitoring of the platelet count for HIT.
The severity of trauma determines the immune response to PF4/heparin and the frequency of heparin-induced thrombocytopenia.
Heparin can induce heparin-induced thrombocytopenia (HIT). The combined effect of type of surgery (major vs minor) and heparin on this prothrombotic immune reaction to platelet factor 4 (PF4)/heparin was analyzed. In a randomized, double-blind study, trauma patients receiving low-molecular-weight (LMWH) or unfractionated heparin (UFH) for thrombosis prophylaxis were assessed for PF4/heparin-antibody seroconversion, HIT, and thrombosis according to type of surgery. The risk for seroconversion was higher than major versus minor surgery odds ratio, 7.98 [95% confidence interval, 2.06-31.00], P = .003, controlled for potential confounders, as was the risk for HIT (2.2% [95% confidence interval, 0.3%-4.1%] vs 0.0%, P = .010). During LMWH compared with UFH thromboprophylaxis, HIT (1 of 298 vs 4 of 316; P = .370) and PF4/heparin seroconversion (1.7% vs 6.6%; P = .002) were less frequent, driven by differences in patients undergoing major surgery (incidence of HIT: LMWH 0.8% vs UFH 4.0%; P = .180; seroconversion rates: 4.0% vs 17.0%; P = .001). After minor surgery, no case of HIT occurred. The severity of trauma and the need for major surgery strongly influence the risk of an anti-PF4/heparin immune response, which is then increased by UFH. In major trauma certoparin may be safer than UFH because it induces HIT-antibody seroconversion, and the corresponding risk of HIT, less frequently.