Rat pregnancy, experimental pseudopregnancy, and experimental decidua induction promote skin allograft survival of paternal and unrelated skin donors by specific and nonspecific mechanisms. Experimental pseudopregnant females were given allogeneic cells by two routes: intraperitoneal (IP) and in utero (IU). The females injected by the IU route, with allosensitized spleen cells, tolerated paternal skin allografts (average 26 days) better than those from other experimental groups and even from allopregnant females bearing a paternal allograft. The orthotopic immunization by the IU route, as shown by an enhancing effect of in utero culture medium injection, seemed important. In vitro studies revealed that the ability of subscapular lymph node (SCLN) cells draining the allograft to destroy Wistar/Furth (W/Fu) target cells decreases markedly in parallel with prolongation of skin allograft survival. Suppression of lymphocyte-mediated cytotoxicity against W/Fu target cells exceeded 70% when SCLN cells were used as responder cells. We propose that maternal T-cell immunization (via in utero) against fetal antigens occurs in pregnancy and plays a role in maintaining fetal tolerance, while specific cell-mediated cytotoxicity is impaired. Both specific and nonspecific local factors may promote such an enhancement of allograft survival.

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[Potentials risks in drug prevention of thrombosis--low-molecular-weight heparin versus standard heparin].

INTRODUCTION: At present, low molecular-weight heparins are recommended for efficient prophylaxis of thrombembolic complications (TEC), especially in the high-risk areas of orthopedics and trauma surgery. In addition to improved efficacy, a markedly reduced risk of side-effects should also be of great advantage, particularly in terms of heparin-induced thrombocytopenia (HIT) type II, a medicative side-effect which can be associated with severe to life-threatening complications. METHODS: In a prospective study, the incidence of heparin-induced thrombocytopenia HIT type II and the incidence of symptomatic TEC in high-risk orthopedic patients was investigated when the low molecular-weight heparin, enoxaparin, was applied. An analogous study using standard heparin (UFH) served as the comparison group. When the thrombocyte count dropped by 50% compared to the initial value, or when thrombembolic complications with clinical symptoms arose, the serum was examined in the heparin-induced platelet activation test (HIPA test). Phlebography was used to verify symptomatic TEC. RESULTS: 325 patients who had undergone surgery for total hip or knee arthroplasty or for the revision of hip and knee total endoprostheses took part in the study. 3 patients (0.92%) developed clinically symptomatic complications. No HIT type II was observed in the study population. The comparison group (UFH) consisted of 307 patients who had undergone analogous surgery. 13 patients (4.2%) developed clinically symptomatic TEC. In 10 patients (3.3%), these were associated with HIT type II The difference in the thrombosis rate and incidence of HIT type II between the two groups is highly significant. CONCLUSION: For the prophylaxis of thrombembolic complications--especially in the high-risk areas of orthopedics and trauma surgery--unfractioned standard heparin (UFH) is insufficiently effective and associated with a high risk of side-effects, particularly of HIT type II. Low molecular-weight heparins must thus be considered the preferred medication in thrombembolism prophylaxis.

Adult↗

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[Prevention of thromboembolism as a cause of thromboembolic complications. A study of the incidence of heparin-induced thrombocytopenia type II].

PROBLEM: A life-threatening complication of the thrombembolism prophylaxis with heparin is heparin-induced thrombocytopenia (HIT) type II. HIT type II is based on immunological mechanisms. Even low, subcutaneously applied doses may produce HIT type II. In those patients, continued application may cause thromboembolic complications. The most important symptom of HIT type II is a decrease of platelets. METHODS: In a prospective study, we investigated the incidence of HIT type II within the period from 01.07.95 to 30.06.96 in orthopedic patients. We also evaluated the importance of the daily platelet count from the fifth postoperative day for the early diagnosis of HIT type II and a possible reduction of the thrombosis rate. The study included 307 patients after primary implantation of hip and knee endoprosthesis and after hip endoprosthesis replacement. All patients received 3 x 5000 IU/d of unfractionated heparin subcutaneously. Whenever there was a decrease of platelets of at least 50% in relation to the preoperative value or whenever thrombembolic complications occurred, serum was analyzed by the heparin-induced platelet activation test (HIPA). RESULTS: 20 patients developed HIT type II. This corresponds to an incidence of 6.5%. 10 of the HIT type II antibody positive patients (50%) developed thrombembolic complications. 3 patients (0.9%) of the group studied developed clinically symptomatic thrombembolic complications without evidence of heparin antibodies. The total risk of getting thrombembolic complications was 4.2% (13 patients). 3.3% (10 patients) of the entire group developed HIT type II antibody associated thrombembolic complications; 1 patient died. The lethality in the HIT type II antibody positive patient group amounted to 5%. The patients with HIT type II received LMW heparinoid Orgaran (AKZO-Organon, The Netherlands) or hirudin (as a clinical trial). The comparison group (retrospective study from 17.10.92 to 16.10.93) was composed of 262 patients with the same operations and equal thromboembolism prophylaxis. The platelet count was made only as part of routine diagnostic tests. 21 patients (8.0%) developed clinically symptomatic thrombembolic complications. The difference in the thrombosis rate between these two groups of patients is statistically significant. Unrecognized HIT type II is probably the reason for the high thrombembolic complication rate in the comparison group. CONCLUSIONS: The daily platelet count from the fifth postoperative day and from the first day in case of reexposure to heparin is an important measure for the early diagnosis of HIT type II.

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