Tissue plasminogen activator in human plasma measured by radioimmunoassay

A radioimmunoassay (RIA) has been set up using purified human melanoma tissue plasminogen activator and a specific antiserum raised against it. Concentration of antigen in citrated plasma of resting human subjects was found to be 7.1 ± 1.6 ng/ml (mean ± S.D.) while the lower limit of sensitivity of the RIA was 2 ng/ml. After venous occlusion or DDAVP infusion the levels of antigen were invariably elevated and a significant increase in the proportion of antigen having fibrin binding properties was observed. Decay studies $\text{in vitro}$ and gel filtration of post-stimulus plasma indicated that the RIA detects active and inactive forms of antigen and the possible nature of the inactive antigen is discussed.     

去氨加压素在全膝关节置换术中的应用研究

目的：评价去氨加压素用于全膝关节置换术中减少患者失血与降低血栓形成风险的效果。方法：选取2007年3月~2009年5月间120例行全膝关节置换术患者,随机分为两组,每组60例,Ⅰ组（对照组）：术中常规使用止血带,Ⅱ组（去氨加压素组）：术前1 h,给予0.3μg.kg-1剂量的去氨加压素,以100 mL0.9%氯化钠注射液配制,在30~40 min内静脉滴注,术中常规使用止血带,术后第1天、第2天均给予0.3μg.kg-1的去氨加压素,以100 mL0.9%氯化钠注射液配制,在30~40 min内静脉滴注完毕。比较两组术中及术后失血量、输血量、引流量的情况,观察患者术后是否出现有下肢深静脉血栓形成;在术前及术后48 h检测凝血酶原时间（PT）、部分凝血活酶时间（APTT）、凝血酶时间（TT）、纤维蛋白原（FIB）、血管性血友病因子（vWF）、组织型纤维蛋白溶酶原激活剂（t-PA）等凝血功能相关因子。结果：Ⅰ组（对照组）和Ⅱ组（去氨加压素组）术中出血量分别为310±207mL和224±125 mL（P〈0.01）;术后引流量分别为832±166 mL和426±146 mL（P〈0.01）,两组的输血量分别是950±295 mL和496±148 mL（P〈0.01）,术后观察随访,患者下肢深静脉血栓形成情况,Ⅰ组有2例有下肢深静脉血栓形成,而Ⅱ组均未发生下肢深静脉血栓。血液学检查结果：使用DDAVP后,部分凝血活酶时间（APTT）缩短而血管性血友病因子（vWF）、组织型纤维蛋白溶酶原激活剂（t-PA）含量增加,且具有统计学意义。而凝血酶原时间（PT）、凝血酶时间（TT）、纤维蛋白原（FIB）的变化无统计学意义。结论：去氨加压素能增强患者的凝血功能,减少全膝关节置换术患者术中术后失血量、输血量以及引流量,同时能减少术后深静脉血栓形成,能安全、有效地用于膝关节置换术围手术期止血与防止术后血栓的形成。     

Intranasal DDAVP induced increases in plasma von Willebrand factor alter the pharmacokinetics of high-purity factor VIII concentrates in severe haemophilia A patients

Because native circulating factor VIII (FVIII) is maximally stabilized when it is bound to von Willebrand factor (vWf), increased plasma vWf levels may enhance the infused FVIII concentrate intravascular survival and efficacy in severe haemophiliacs. To assess whether the kinetic characteristics and recovery of high purity, plasma-derived (Monoclate-P, Centeon) and recombinant (Bioclate , Centeon) FVIII concentrates are enhanced by increased plasma vWf concentrations, we compared the pharmacokinetic response to a bolus of FVIII infused alone with the response to a bolus infused 2 h after the intranasal delivery of 300 microg of desmopressin acetate (DDAVP) High Concentration Nasal Spray (Stimate, Centeon) in 10 adult severe haemophiliacs. FVIII activity was determined using a one-stage clotting assay on cryopreserved plasma specimens obtained at baseline and at 14 distinct time points (0.25-48 h) following the FVIII infusions. Ristocetin co-factor activity (RCoFA) and vWf antigen levels were assayed at baseline and 2 h after Stimate. FVIII kinetic parameters were calculated using standard, noncompartmental kinetic methods. Statistical analysis was performed using a paired t-test with 95% confidence limits. The mean rises in RCoFA (0.65+/-0.44 IU mL(-1)) and vWf antigen (0.19+/-0.07 IU mL-1) induced by Stimate were significant (P<0.01 and P<0.0001, respectively). The mean increases in the volume of distribution at steady state (Vss) (13.2+/-9.3 dL) and mean residence time (MRT) (4.4+/-3.9 h) between the FVIII-only arm and the FVIII plus Stimate arm were highly significant (P = 0.0015 and P = 0. 0059, respectively). The mean differences in recovery, area under the curve (AUC), half-life, and clearance (Cl) were not significantly altered. Subgroup analysis revealed statistically significant increases in Vss and MRT (P = 0.025 and P = 0.012, respectively) following the administration of intranasal DDAVP in the Monoclate-P cohort, but not in the Bioclate group. These data suggest that even modest pharmacologically induced increases in plasma vWf can favourably affect the kinetics of high-purity, plasma-derived FVIII concentrates in severe haemophiliacs.     

Management of von Willebrand disease: a survey on current clinical practice from the haemophilia centres of North America.

The optimal treatment of patients with von Willebrand's disease (vWD) remains to be defined. Moreover, it has not been firmly established which, if any, commonly measured parameters of von Willebrand factor (vWF) protein in the plasma are useful in guiding treatment. To better understand what guidelines physicians follow in the management of vWD, we surveyed 194 North American physicians who are members of the Hemophilia Research Society. Ninety-nine per cent of responding physicians depend on factor VIII (FVIII):C, vWF:RCo activity and vWF:AG to diagnose vWD, while only 49% use the bleeding time. The minimal goals of treatment for patients undergoing major surgery/trauma or central nervous system haemorrhage were FVIII:C and vWF:RCo activity greater than 80% while levels of more than 50% for minor surgery and dental extractions were considered adequate. Treatment of vWD was based on the type of vWD with type 1 patients being treated most often with desmopressin acetate (DDAVP) alone, types 2A and 2B patients with a combination of DDAVP and a vWF-containing FVIII product, type 3 patients with vWF-containing concentrate. Viral infections, including human immunodeficiency virus, hepatitis A, B and C viruses, and parvovirus have been seen in vWD and the efficacy of viral attenuation processes is a major criterion for the selection of treatment by physicians. Based on this survey, prospective studies need to be designed to address the clinical efficacy, safety and predictive value of laboratory monitoring of patients with vWD.     

Elevated sleep arousal thresholds in enuretic boys: clinical implications

Enuretic children are described as difficult to arouse from sleep. We studied auditory sleep arousal thresholds in enuretic boys and report on die clinical implications of these findings. Fifteen enuretic and 18 control subjects (7–12-year-old males) were studied in a sleep laboratory for four consecutive nights using standard polysomnographic recording techniques. Sleep was undisturbed for the initial two nights and waking thresholds were measured on the following two nights. Enuretic children wet most frequently in the first two-thirds of the night. Arousal attempts were successful 39.7% of the time in controls and only 9.3% of the time in enuretics. In conclusion, enuretic males were more difficult to arouse than age-matched controls. The elevated arousal thresholds may be due to delayed maturation. Treatment programmes that rely on awakening should be aware of these features.     

A new Italian family with severe prekallikrein deficiency. Desmopressin-induced fibrinolysis and coagulation changes in homozygous and heterozygous members

Summary In this paper we report the case of a new Italian family with severe cross-reacting material prekallikrein deficiency (CRM⁻). The proposita is a 22-year-old woman referred for evaluating an extremely prolonged activated partial thromboplastin time (APTT) detected during a routine screening. No clearcut bleeding history was reported. Prekallikrein antigen and activity were not measurable. The other contact-phase factors were within the normal range. Using an electromechanical coagulometer, six different commercial reagents yielded a markedly prolonged APTT (ratio>2). By prolonging the incubation time up to 10 min, APTT was normalized only with reagents employing ellagic acid as activator. On the contrary, APTT remained markedly prolonged using particulate activators (i.e. micronized silica and celite). No differences were observed using either rabbit or bovine brain cephalin. APTT was also performed on a laser automated ACL instrument; in this case reagents using ellagic acid yielded only moderately prolonged APTT values (ratio 1.3vs 1.4). The intrinsic fibrinolytic activity, as assessed by blood activator inventory test, was found to be moderately reduced (about 50% of normal) in the proposita, whereas normal values were measured in the heterozygous relatives. After infusion of 0.3 μg/kg 1-desamino-8-D-arginine vasopressin (DDAVP), kallikrein levels did not change in the proposita and her heterozygous relatives. A normal release of tissue-plasminogen activator, as assessed by fibrin-plate assay, was observed in all family members including the proposita.     

Hyper-responsiveness to DDAVP for patients with type I von Willebrand's disease and normal intra-platelet von Willebrand factor

Desmopressin (DDAVP) has gained wide acceptance as the drug of first choice in the treatment or prevention of haemorrhages in the majority of patients with von Willebrand's disease (vWd). However, data concerning the clinical effectiveness of DDAVP refer generally to mild vWd, with factor VIII and vW factor levels usually above 20% of normal. In 14 patients with type I vWd characterized by very low plasma levels of factor VIII coagulant activity (VIII:C) and vWf, measured as ristocetin cofactor activity (lower than 20% and 3% of normal respectively), but with a normal intraplatelet content of vWf, a test infusion of DDAVP (0.4 microgram/kg) elicited a very marked increase of VIII:C and vWf and normalized the bleeding time. All these patients subsequently underwent tooth extraction after DDAVP infusion. The incidence of bleeding was remarkably low, with only two minor late bleeding episodes easily stopped by repeating DDAVP infusion. Compared to the cases of type I vWd with unknown intraplatelet vWf content reported in the literature, this subgroup of patients had a more marked, albeit short-lived, increment of VIII:C and vWf.     

DDAVP challenge tests in boys with mild/moderate haemophilia A

Desmopressin (DDAVP) increases plasma factor VIII coagulant activity (FVIII:C) levels in patients with mild/moderate haemophilia A. In some subjects, FVIII can be increased to haemostatic levels, thereby avoiding use of factor VIII concentrates. We reviewed our hospital's experience with 62 boys with FVIII:C levels 0.01-0.3 IU/ml who had a DDAVP challenge test (i.v. 0.3 microg/kg) following diagnosis. A therapeutic response was defined as a 1 h post-FVIII:C increase at least twofold over baseline and > 0.3 IU/ml. Of the total group, 29 (47%) boys responded to DDAVP, all of them with mild haemophilia (baseline FVIII:C > or = 0.05 IU/ml), yielding a response rate of 57% in this subgroup. Boys who responded to DDAVP had higher baseline FVIII:C levels (mean +/- SEM, 0.17 +/- 0.01 vs 0.10 +/- 0.01 IU/ml, P < 0.01) and were older (5.2 +/- 0.8 vs 3 +/- 0.4 years, P = 0.02) than those who failed to do so. The association between DDAVP response and age, however, remains unclear: seven boys who failed the initial challenge test responded to re-challenge after a mean of 6.3 years (median 4.9, range 0.5-12.5), increasing the response rate in boys with mild haemophilia to 71%. Age and FVIII:C association with DDAVP response are both important in boys with mild/moderate haemophilia A. Absence of response to DDAVP should therefore be confirmed by later re-challenge.