Viable pregnancies beyond 28 weeks gestation in women with a history of unexplained recurrent miscarriage have reduced platelet function.

OBJECTIVE: The aim of this study was to characterize platelet function in pregnant patients with a history of unexplained recurrent miscarriage (RM) in the third trimester of a subsequent viable pregnancy, a time at which platelet dysfunction may be associated with an increased obstetric risk. STUDY DESIGN: A prospective study was performed comparing 30 viable pregnancies that had reached at least 28 weeks' gestation amongst patients who had a background history of unexplained RM, with 30 healthy pregnant controls at a similar gestational age. Platelet function was determined by means of platelet aggregation in response to 5 different agonists at multiple concentrations. RESULTS: Amongst the 30 RM patients with ongoing viable pregnancies, we demonstrated significantly reduced platelet aggregation compared to the pregnant controls in the third trimester. For three out of five agonists, we demonstrated statistically significantly decreased platelet aggregation and for all five agonists we demonstrated significantly decreased platelet aggregation in the postnatal period. There were no obvious differences in obstetric outcomes. CONCLUSION: This study shows that women with a history of unexplained RM have reduced platelet function after 28 weeks' gestation in their subsequent pregnancies compared to healthy pregnant controls, but without this difference leading to any obvious increase in adverse obstetric risk.

Reduced spontaneous platelet aggregation: a novel risk factor for adverse pregnancy outcome.

OBJECTIVE: Spontaneous platelet aggregation has not been adequately assessed as a potential risk factor for adverse outcomes in pregnancy. Therefore the objective of this study was to assess spontaneous platelet aggregation (SPA), measured via a novel functional assay, as a risk factor for hypertensive disease and intra-uterine growth restriction (IUGR). STUDY DESIGN: This was a prospective longitudinal study. Spontaneous platelet aggregation was assessed as a marker of platelet reactivity using a modification of light transmission aggregometry. Platelet reactivity was assessed in four groups: non-pregnant healthy female volunteers (n=30), longitudinally in normal uncomplicated pregnancy (n=50), hypertensive disorder (n=40) and IUGR (n=30). The mean percentage SPA was plotted and compared across all groups. RESULTS: Spontaneous platelet aggregation was significantly reduced in the first trimester compared to the non-pregnant group (p-value=0.003). The mean aggregation for the hypertensive group was 1.9%, (95% CI -0.08 to 4.02) and for the IUGR group was 1.6%, (95% CI -0.6 to 3.72). Platelet aggregation in the hypertensive group was significantly reduced compared to the normal pregnant group (p<0.05). Spontaneous platelet aggregation was also reduced in the IUGR group compared to normal pregnancy (p<0.05). CONCLUSION: This study demonstrates that a reduction of spontaneous platelet aggregation may be a novel risk factor for adverse pregnancy outcomes such as pre-eclampsia and IUGR. The most clinically significant finding is that SPA is significantly lower in pregnancies complicated by hypertension and IUGR compared to those who had a normal pregnancy outcome. Further studies should be carried out to asses if spontaneous platelet aggregation may be a clinically useful tool for the prediction of pre-eclampsia and IUGR.

Altered Platelet Function in Intrauterine Growth Restriction: A Cause or a Consequence of Uteroplacental Disease?

Objective A limited number of platelet function studies in intrauterine growth restriction (IUGR) have yielded conflicting results. We sought to evaluate platelet reactivity in IUGR using a novel platelet aggregation assay. Study Design Pregnancies with IUGR were recruited from 24 weeks' gestation (estimated fetal weight < 10th centile) and had platelet function testing performed after diagnosis. A modification of light transmission aggregometry created dose-response curves of platelet reactivity in response to multiple agonists at differing concentrations. Findings were compared with healthy third trimester controls. IUGR cases with a subsequent normal birth weight were analyzed separately. Results In this study, 33 pregnancies retained their IUGR diagnosis at birth, demonstrating significantly reduced platelet reactivity in response to all agonists (arachidonic acid, adenosine diphosphate, collagen, thrombin receptor-activating peptide, and epinephrine) when compared with 36 healthy pregnancy controls (p < 0.0001). Similar results were obtained for cases demonstrating an increasing in utero growth trajectory. When IUGR preceded preeclampsia or gestational hypertension, platelet function was significantly reduced compared with normotensive IUGR. Conclusion Using this comprehensive platelet assay, we have demonstrated a functional impairment of platelets in IUGR. This may reflect platelet-derived placental growth factor release. Further evaluation of platelet function may aid in the development of future platelet-targeted therapies for uteroplacental disease.

Platelet function in patients with a history of unexplained recurrent miscarriage who subsequently miscarry again.

OBJECTIVE: This study was designed to evaluate platelet aggregation in pregnant women with a history of unexplained recurrent miscarriage (RM) and to compare platelet function in such patients who go on to have either another subsequent miscarriage or a successful pregnancy. STUDY DESIGN: A prospective longitudinal study was performed to evaluate platelet function in a cohort of patients with a history of unexplained RM. Platelet reactivity testing was performed at 4-7 weeks gestation, to compare platelet aggregation between those with a subsequent miscarriage and those who had successful live birth outcomes. Platelet aggregation was calculated using a modified assay of light transmission aggregometry with multiple agonists at different concentrations. RESULTS: In a cohort of 39 patients with a history of RM, 30 had a successful pregnancy outcome while nine had a subsequent miscarriage again. Women with subsequent miscarriage had reduced platelet aggregation in response to adenosine diphosphate (P value 0.0012) and thrombin receptor activating peptide (P value 0.0334) when compared to those with successful pregnancies. Women with subsequent miscarriages also had a trend towards reduced platelet aggregation in response to epinephrine (P value 0.0568). CONCLUSION: Patients with a background history of unexplained RM demonstrate reduced platelet function if they have a subsequent miscarriage compared to those who go on to have a successful pregnancy.

Cardioactive steroid poisoning: a comparison of plant- and animal-derived compounds.

INTRODUCTION: Cardioactive steroids (CASs) are found in plants, animals, and insects. Their affinity for Na+-K+ ATPase is attenuated by the type of lactone at carbon 17 (C17) of the steroid backbone: those with 5-membered lactone rings, or cardenolides, are derived mostly from plants with 6-membered rings or from animals with bufadienolides. A systematic review of CAS poisoning was performed to compare the mortality rate of cardenolides and bufadienolides. METHODS: MEDLINE was searched for articles using commonly reported names of CASs, and keywords were limited to human cases only. We searched cases from 1982 to 2003, so that supportive care was similar and digoxin-specific Fab was available. Identified reports of CAS poisoning were read to exclude cases involving licensed pharmaceuticals. Inclusion criteria included hyperkalemia, gastrointestinal symptoms, electrocardiographic evidence of CAS toxicity, digoxin serum concentration, or history of exposure to a substance containing a CAS. Clinical data was collected, including information about treatment with digoxin-specific Fab and treatment outcome. RESULTS: Fifty-nine articles, describing 924 patients, were identified. Eight hundred ninety-seven patients (97%) ingested a CAS with a 5-membered lactone ring, and mortality was 6% (n = 54). Twenty-seven patients (2.9%) ingested a CAS with a 6-membered lactone ring, and mortality was 29.6% (n = 8). The difference in mortality rates was statistically significant (p < 0.001, [X2]). CASs with 6-member rings accounted for the highest percentage of nonsuicidal exposures. CONCLUSION: Although cardenolides accounted for the majority of exposures, bufadienolides were five times more lethal than cardenolides.

Amiodarone fails to improve survival in amitriptyline-poisoned mice.

OBJECTIVE: Amiodarone, a class III antidysrhythmic agent, blocks Na+, Ca2+, and K+ channels as well as the beta-adrenergic receptor. Despite increased use of amiodarone for wide-complex tachycardia, its efficacy in the treatment of dysrhythmias induced by tricyclic antidepressants has not been tested. We investigated the effect of amiodarone and amitriptyline in a mouse lethality model. METHODS: The LD50 of amitriptyline obtained from reference sources was confirmed by giving 100 mg/kg to 40 mice by intraperitoneal (IP) injection. The safety of the treatment dose of amiodarone was confirmed by giving 50 mg/kg by IP injection to 10 mice. One hundred and nine mice were randomized to receive pretreatment with 50 mg/kg amiodarone (n=55) or an equal volume of saline or water as a volume control (n=54). Thirty minutes after pretreatment or control injection, the mice received amitriptyline, 100 mg/kg. Outcome was defined as death or survival 3 h after amitriptyline injection. RESULTS: In our confirmation of the LD50 of amitriptyline, 25/40 mice died (62.5%). None of the 10 mice that received only amiodarone died. In the control + amitriptyline arm, 36/54 (66.7%) died, compared with 39/55 (70.9%) in the amiodarone+amitriptyline arm (X2, p=0.663). Power analysis demonstrated a 90% chance of finding a 28% difference. CONCLUSIONS: Pretreatment with amiodarone does not appear to significantly alter the lethality of amitriptyline poisoning in mice. Given the inability to monitor cardiac activity in this model, further investigation in a larger animal is required.