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Biomedical subjects

K A Louden

Publications and source records attributed to K A Louden.

11 recordsLinked to original sources
PubMed1994

Neonatal platelet reactivity and serum thromboxane B2 production in whole blood: the effect of maternal low dose aspirin.

OBJECTIVES: Concern has been expressed about possible neonatal side effects after the use of maternal anti-platelet agents in pregnancy, particularly low dose aspirin treatment. We have studied neonatal platelet behaviour using whole blood techniques, and assessed the neonatal effect of the maternal ingestion of 60 mg aspirin daily. DESIGN: Cross sectional and randomised, double-blind, placebo-controlled. SETTING: University hospital. SUBJECTS: 1. Eight normal women, studied before conception, and their infants. 2. Twenty-four infants whose mothers had been randomised to receive either 60 mg aspirin daily, or placebo, in double-blind fashion. METHODS: The Clay Adams Ultra Flo 100 whole blood single platelet counter was employed to measure platelet aggregation in response to various agonists. The platelet release reaction was also measured in whole blood, and serum thromboxane B2 (TxB2) production was measured by radio-immunoassay. Umbilical cord blood samples were obtained at delivery. RESULTS: 1. Neonatal platelet aggregation induced by adrenaline, ADP and platelet activating factor was reduced in comparison with their mothers (P < 0.01), whereas the neonatal platelet release reaction was reduced when stimulated by collagen and U46619 (a thromboxane mimetic) (P < 0.01). Serum TxB2 production was similar in mothers and babies. 2. Neonatal platelet aggregation, release reaction and serum TxB2 production were not significantly reduced in infants exposed to maternal aspirin in comparison with those neonates exposed to maternal placebo. This is in contrast to the effect on maternal platelets. CONCLUSIONS: Although only a small number of patients were studied, we interpret this as a relative sparing of neonatal platelet reactivity due to the presystemic action of low dose aspirin.

Adult↗
PubMed1992

A randomized placebo-controlled study of the effect of low dose aspirin on platelet reactivity and serum thromboxane B2 production in non-pregnant women, in normal pregnancy, and in gestational hypertension.

OBJECTIVE: To investigate the effect of 60 mg aspirin daily on platelet reactivity and prostaglandin production in various groups of patients. Similar regimens, which are thought to act through inhibition of platelet thromboxane production, are currently undergoing clinical assessment for the prevention of pre-eclampsia and intrauterine growth retardation. DESIGN: A prospective randomized placebo controlled study. SETTING: University Hospital, Nottingham. SUBJECTS: 12 non-pregnant female volunteers, 18 normal primigravidae before 16 weeks gestation and 16 pregnant women admitted with gestational hypertension (GH) at a mean gestation of 38 weeks. INTERVENTIONS: In the non-pregnant women blood samples were taken before and after a 10-day course of 60 mg aspirin daily. The primigravidae had blood samples taken at 16 weeks and then they were randomized to receive either 60 mg aspirin daily or a matched placebo. Further blood samples were obtained at 28, 32 and 36 weeks. MAIN OUTCOME MEASURES: Changes in platelet reactivity and release reaction, and serum thromboxane production, were estimated in whole blood. RESULTS: 60 mg aspirin daily significantly inhibited cyclo-oxygenase dependent platelet aggregation, release reaction and serum thromboxane production in non-pregnant and pregnant women, and in women with GH (P less than 0.01). When adrenaline was used as the aggregating agent, the cyclo-oxygenase pathway was recruited in the increased reactivity seen in the third trimester of normal pregnancy, and was sensitive to inhibition by low dose aspirin. CONCLUSION: Low dose aspirin would appear to be an appropriate agent for the inhibition of platelet reactivity associated with hypertensive pregnancy.

Adult↗
PubMed1991

Platelet reactivity and serum thromboxane B2 production in whole blood in gestational hypertension and pre-eclampsia.

OBJECTIVE: To determine the nature and extent of changes in platelet reactivity in gestational hypertension and pre-eclampsia (using whole blood techniques which may be more physiological than those previously employed). DESIGN: Cross-sectional observational study. SUBJECTS: 8 normal primigravidae, 16 women with gestational hypertension and 12 women with pre-eclampsia, studied at around 36 weeks gestation. RESULTS: Platelet reactivity (aggregation and release reaction) induced by stimulation with adrenaline was decreased in the pre-eclamptic group. Serum thromboxane B2 production was unchanged in both hypertensive groups compared with the control group. CONCLUSIONS: In the context of evidence of platelet activation in pre-eclampsia, our findings are interpreted as reflecting platelet exhaustion.

Adult↗
PubMed1990

A longitudinal study of platelet behaviour and thromboxane production in whole blood in normal pregnancy and the puerperium.

A longitudinal study of platelet behaviour (platelet aggregation and release reaction) in whole blood and of serum thromboxane B2 production was performed before, during and after normal pregnancy. The response of platelets to arachidonic acid and to adrenaline was significantly increased in the third trimester. Six weeks after delivery, values were still modestly increased but return to non-pregnant values was complete by 12 weeks. Serum thromboxane B2 production was unchanged throughout pregnancy and the puerperium.

Arachidonic Acid↗