The Hemostatic Activity of Amniotic Fluid

An assessment of the effects on coagulation of midtrimester and final-trimester amniotic fluid on whole blood by Thrombelastograph analysis

The Thrombelastograph((R)) test (TEG; Haemoscope Corporation, Skokie, IL) was used to assess the effects of midtrimester and final-trimester amniotic fluid (AF) on whole blood coagulation. Different volumes of midtrimester and final-trimester AF were added to whole blood from nonpregnant volunteers in a series of TEG tests. The addition of both midtrimester and final-trimester AF resulted in significant decreases in reaction time (P < 0.001) and time from reaction to a fixed level of clot firmness (P < 0.05) and significant increases in angle (P < 0.05) and coagulation index (P < 0.05) values. This reflects accelerated clot initiation and propagation. There was no significant change in the maximal amplitude or % lysis at 30 and 60 min with the addition of either midtrimester or final-trimester AF. There was no significant difference between the effects of midtrimester and final-trimester AF on whole blood TEG. TEG may be an additional useful tool in the treatment of coagulopathy in AF embolism.

IMPLICATIONS

We used the Thrombelastograph((R)) test (Haemoscope Corporation, Skokie, IL) to assess the effects of midtrimester and final-trimester amniotic fluid (AF) on whole blood coagulation. Results demonstrate that AF accelerates clot initiation and propagation. The Thrombelastograph((R)) test may be useful in assessing coagulopathy in patients with AF embolism.

Meconium and amniotic fluid embolism: effects on coagulation in pregnant mini-pigs

OBJECTIVE

A hallmark of amniotic fluid embolism is the induction of coagulation defects. Little is known about the nature of these defects or the causative agent or agents. The purpose of this study was to assess the effects of meconium containing (native) meconium-amniotic-fluid infusion (MAFI) and meconium-free (centrifuged) amniotic-fluid infusion (AFI) on the coagulation system in the mini-pig model.

DESIGN

Laboratory study.

SETTING

University institute animal laboratory.

SUBJECTS

Near-term pregnant Göttingen bred mini-pigs in three groups (control, MAFI, AFI) of six animals each.

INTERVENTIONS

After induction of anesthesia, amniotic fluid was collected by cesarean section in all animals. Depending on the group, animals received either Ringer's solution (control), native amniotic fluid (MAFI), or centrifuged amniotic fluid (AFI) via an ear vein.

MEASUREMENTS AND MAIN RESULTS

Blood samples were taken from a central vein before infusion (baseline), immediately after infusion, every 10 mins until 90 mins after infusion, and finally, every 20 mins until 150 mins after infusion. The following parameters were measured: Platelets, partial thromboplastin time, prothrombin time, fibrinogen, factors V, VII, VIII, antithrombin III, and protein C. The values relative to baseline in the MAFI and AFI groups were compared with control by rank order test. A p<.05 was considered statistically significant. Compared with the control group, platelets were lower in the MAFI group (p<.005), PTT was prolonged in both the MAFI and AFI groups (p<.005), fibrinogen was lower in both the MAFI and AFI groups (p<.05), prothrombin index was lower (i.e., prothrombin time was prolonged) in the MAFI group (p<.05), and protein C was lower in the MAFI group (p<.005).

CONCLUSIONS

Both MAFI and, to a much lesser extent, AFI cause an activation of coagulation in mini-pigs. The changes induced by meconium-free AFI are probably not sufficient to explain the high mortality of the condition.

Delayed onset of coagulopathy following amniotic fluid embolism: two case reports

Two cases of amniotic fluid embolism with markedly similar clinical presentations occurred in the same unit in a 6 month period. Both patients were under general anaesthesia for caesarean section at the time of embolism. Having been successfully extubated and found to be haemodynamically stable, they developed a coagulopathy after an interval of 2 hours. There had been initial uncertainty as to the diagnosis in the first patient and the haematological sequelae were not fully anticipated. Experience in dealing with the first patient who died, may have influenced the survival of the second. The diagnosis of amniotic fluid embolism should be considered at an early stage in all cases of maternal collapse and the appropriate preparations made to combat a potential coagulopathy.

Factors influencing hemostasis after umbilical vein puncture in vitro

Bleeding from the site of cordocentesis can be detected by ultrasound examination, but significant hemorrhage into the amniotic fluid rarely occurs. To evaluate the relative contribution of amniotic fluid thromboplastins and the quantity of Wharton's jelly in facilitating coagulation at the puncture site, amniotic fluid samples and umbilical cord segments were obtained at cesarean section from 20 patients. After puncture of the umbilical vein, bleeding times were measured in amniotic fluid and 0.9% sodium chloride. The quantity of Wharton's jelly was assessed by measuring umbilical cord circumference. Mean bleeding times were significantly shorter in amniotic fluid compared with saline solution, but there was no consistent relationship between bleeding times and umbilical cord circumference. We conclude that properties of amniotic fluid facilitate coagulation at the site of umbilical vein puncture.

Renal and cerebral necrosis in survivor after in utero death of co-twin

A newborn with bilateral renal cortical necrosis and severe cerebral damage in association with a macerated stillborn twin is reported. The alterations in the kidneys and brain of the twin born alive suggest that the primary event took place before birth. Thromboplastic material and embolizing particles derived from the dead fetus may have passed the monoamnionic-monochorionic twin placenta and caused disseminated intravascular coagulation in the living twin, followed by infarction in other organ systems.

Effect of hydatidiform molar vesicular fluid on blood coagulation

The effect of fluids from both complete and partial hydatidiform moles on blood coagulation was determined. Coagulation was evaluated with use of the one-stage prothrombin time and the activated partial thromboplastin time. These studies demonstrated that the fluids shortened the activated partial thromboplastin time but not the prothrombin time. The use of plasmas deficient in factors V, VIII, IX, and X as substrate showed that the fluids shortened the activated partial thromboplastin time in the presence of plasmas deficient in factors VIII and IX but had no effect on the activated partial thromboplastin time in the presence of plasmas deficient in factors V and X. These data suggest that hydatidiform mole fluids possess procoagulant activity and that the activation of blood coagulation takes place at the level of factor X. These findings may have relevance to the placental and decidual focal necrosis seen in molar pregnancies, especially those of the complete variety.

Studies on the procoagulant activity of human amniotic fluid. I. Stability and coagulation factor requirements

A fraction of human amniotic fluid possessing procoagulant activity was purified 35-70 fold by gel filtration on Sepharose 4B. The activity eluted in the void volume indicating a particle size in excess of 5 X 10(6) daltons. The amniotic fluid factor (AFF) activity is stabilized on storage in the presence of Ca++ ions which could not be replaced by Mg++. Addition of phospholipids resulted in accelerated loss of activity. Steps taken to remove factor VII did not affect the activity, but factor X and V are required.

Prenatal diagnosis of classic hemophilia

Prenatal diagnosis of classic hemophilia (hemophilia A) in mid-trimester was achieved by means of immunoradiometric assays for factor VIII on fetal plasma and amniotic-fluid mixtures obtained by fetoscopy. Samples were analyzed from six male fetuses at risk for severe hemophilia and from nine control fetuses for which fetoscopy was carried out to attempt prenatal diagnosis of other genetic disorders. The factor VIII coagulant-antigen values for the control (non-hemophilic) samples were 17 to 94, and the factor VIII related-antigen concentrations were 50 to 155 U per deciliter. Three of the fetuses at risk for hemophilia had factor VIII values in the control range, and these infants were normal at birth. The other three fetuses had low concentrations of factor VIII coagulant antigen but normal concentrations of factor VIII related antigen. These values and the diagnoses of severe hemophilia were confirmed with blood from the abortuses.

Amniotic fluid embolism

The statement that amniotic fluid embolism is the most dangerous and untreatable condition in obstetrics appears to be true. It must be suspected in any patient who collapses or bleeds excessively during labour or the immediate post-partum period. Attempts should be made to secure a definitive diagnosis in life by examination of blood obtained from the right side of the heart and the sputum for elements of amniotic fluid. Lung scanning is a useful aid to diagnosis. The principal factors that have been implicated in the clinical syndrome of amniotic fluid embolism are anaphylaxis, vascular obstruction by particulate matter, vascular spasm due to prostaglandins and possibly some other vasoactive substances, and the possibility that all the changes could be explained by disseminated intravascular coagulation as a primary event. Further work is required to elucidate the relative contributions of these various factors. Due to the suddeness of the catastrophe and the very high mortality, haemodynamic data in humans is virtually non-existent. With improved methods of resuscitation it is to be hoped that the mortality rate will be reduced and that such data will become available. In this way it might become possible to apply the results of animal research and indicate the most effective method of treatment.

The defibrination syndrome

Defibrination is a fairly common clinical entity seen in a wide variety of clinical disorders. With an awareness of the likely clinical settings, a high degree of suspicion, and widely available sensitive laboratory tests, the diagnosis is ordinarily easily made. The best therapy is usually that which is directed at the underlying disease rather than at the defibrination syndrome itself. In certain symptomatic cases, heparin and/or replacement therapy is indicated, especially if the underlying disorder cannot be immediately successfully treated. On occasion, antifibrinolytic therapy will be useful, always with due regard to the danger of renal cortical necrosis. Depending on the clinical setting, it may be advisable to give heparin with the antifibrinolytic therapy to minimize that danger.