Anticoagulants in pregnancy

Anticoagulant rodenticides on our public and community lands: spatial distribution of exposure and poisoning of a rare forest carnivore

Anticoagulant rodenticide (AR) poisoning has emerged as a significant concern for conservation and management of non-target wildlife. The purpose for these toxicants is to suppress pest populations in agricultural or urban settings. The potential of direct and indirect exposures and illicit use of ARs on public and community forest lands have recently raised concern for fishers (Martes pennanti), a candidate for listing under the federal Endangered Species Act in the Pacific states. In an investigation of threats to fisher population persistence in the two isolated California populations, we investigate the magnitude of this previously undocumented threat to fishers, we tested 58 carcasses for the presence and quantification of ARs, conducted spatial analysis of exposed fishers in an effort to identify potential point sources of AR, and identified fishers that died directly due to AR poisoning. We found 46 of 58 (79%) fishers exposed to an AR with 96% of those individuals having been exposed to one or more second-generation AR compounds. No spatial clustering of AR exposure was detected and the spatial distribution of exposure suggests that AR contamination is widespread within the fisher’s range in California, which encompasses mostly public forest and park lands Additionally, we diagnosed four fisher deaths, including a lactating female, that were directly attributed to AR toxicosis and documented the first neonatal or milk transfer of an AR to an altricial fisher kit. These ARs, which some are acutely toxic, pose both a direct mortality or fitness risk to fishers, and a significant indirect risk to these isolated populations. Future research should be directed towards investigating risks to prey populations fishers are dependent on, exposure in other rare forest carnivores, and potential AR point sources such as illegal marijuana cultivation in the range of fishers on California public lands.

Use of genetic and nongenetic factors in warfarin dosing algorithms

Despite the fact that warfarin has been used as an anticoagulant for many years, the safety profile for this drug has been poor. Inappropriate dosing continues to contribute to significant morbidity and mortality due to thrombotic disease and bleeding. Therefore, there is a need for the development, characterization and implementation of dosing algorithms using a patient's demographic information and genotype. Recently, polymorphisms in two genes, cytochrome P450 2C9 and vitamin K epoxide reductase complex 1, have been shown to affect warfarin's pharmacogenomics and pharmacodynamics, respectively. Adding genotypes to a dosing algorithm may enable better prediction of initial warfarin dosing than use of demographic data alone. An advisory committee of the US FDA voted on November 14, 2005, to require manufacturers of warfarin to relabel their product, indicating that genotyping is recommended prior to drug administration. The exact date when this recommendation will be enacted remains to be determined. Successful implementation of pharmacogenomics into clinical practice requires genotyping results that can be translated directly into clinical decisions. The development of a warfarin dosing algorithm that includes genotyping may be the means to achieve this goal.

Brodifacoum toxicosis in two neonatal puppies

Eight out of a litter of 13 puppies were either born dead or died within 48 hours of birth. Three puppies that died shortly after birth were necropsied. Two puppies had hemorrhage in the thoracic and peritoneal cavities, intestinal serosa, and meninges. The third puppy was smaller than the other two puppies but did not have detectable hemorrhage. Brodifacoum, a second-generation coumarin anticoagulant, was detected in livers from the two puppies with hemorrhage. The dam did not have clinical signs of coagulopathy before or subsequent to whelping. The owners were confident that the dog had not been exposed to rodenticide for at least 4 weeks before whelping. A presumptive diagnosis of in utero brodifacoum toxicity was made. To the authors' knowledge this is the first time a second-generation coumarin anticoagulant has been detected in the liver of a newborn animal. This case is also unique because the dam was unaffected, suggesting that fetuses are more susceptible to brodifacoum toxicity than adult animals.

Free tissue transfer in pregnancy: guidelines for perioperative management

A successful free tissue transfer of serratus anterior muscle, to provide coverage for an open ankle defect in a pregnant patient, is described. Microvascular surgery in the presence of a viable pregnancy demands considerations unique to this situation. Although rarely possible, an attempt should be made to plan surgery to coincide with the second trimester, to lessen the risk of anesthesia to the fetus. Maternal positioning, fluid balance, and aspiration precautions need to be critically addressed. Close perioperative monitoring by an obstetrician is essential. The condition of pregnancy results in a hypercoagulable state that may lead to an increased risk of anastomotic failure. The use of anticoagulants results in increased risk of bleeding, not only for the patient but also for the fetus, as well as risk of teratogenic effects. Closely monitored heparin is considered safe in pregnancy as is low-molecular-weight dextran and low-dose aspirin. Additional considerations include the use of narcotics and sedatives for comfort postoperatively, as well as antibiotic choices, if indicated.

Feto-maternal morbidity and mortality after cardiac valve replacement

BACKGROUND

The aim of this study is to evaluate the fetomaternal morbidity and mortality of the pregnancies of women who conceived after cardiac valve replacement.

METHODS

A consecutive series of one hundred and thirty-six pregnancies of one hundred and one patients who conceived after cardiac valve replacement were retrospectively analyzed. Regarding the anticoagulation therapy, 101 patients were classified into three groups: A: patients on oral anticoagulants (n=68), B: patients on heparin (n=16) and C: patients who received no anticoagulation (n=17).

RESULTS

Three groups (patients on oral anticoagulants (A), on heparin (B), patients who received no anticoagulation (C)) were compared in terms of spontaneous abortion (19%, 11%, 5.6%), preterm delivery (14%, 22.3%, 16.6%), maternal mortality (3%, 11.1%, 0%), thromboembolic events (4%, 11.1%, 0%), cardiac failure (6%, 11.1%, 11.1%), atrial fibrillation (9%, 11.1%, 5.6%), antenatal bleeding (9%, 11.1%, 5.6%), delivery route and fetal malformation (5%, 0%, 0%) and no statistically significant differences were detected. In group B, hematoma formation rate (22.2%) (p=0.011) and transfusion rate (27.8%) (p=0.005) were significantly higher. Five cases of congenital anomalies were detected, all belonging to group A, but this tendency was not found to be statistically significant.

CONCLUSIONS

Management of pregnancies with prosthetic heart valves require closely monitored anticoagulation, and an obstetrician should be familiar with the potential fetal and maternal adverse effects of any anticoagulant therapy during the course of pregnancy.

Anticoagulation with warfarin in infants and children

OBJECTIVE

To provide a comprehensive review of warfarin use in infants and children, including recommendations for appropriate dosage and monitoring parameters.

DATA SOURCES

A MEDLINE search (1966-1995) was used to identify pertinent English-language articles in the medical literature. The key search term was warfarin. Additional material was obtained from references cited in articles retrieved through MEDLINE.

STUDY SELECTION

All articles involving children younger than 18 years were evaluated. In addition, articles on the pharmacokinetics and pharmacodynamics in adults, adverse effects, and drug interactions were included.

DATA EXTRACTION

Material selected for review included clinical trials, case reports, and surveys of practice.

DATA SYNTHESIS

Warfarin has been used as prophylactic therapy in children with prosthetic cardiac valves as well as for prevention of thromboembolic complications associated with autoimmune disorders and protein C or protein S deficiency. Warfarin also has been used to prevent embolization in children with deep-vein thrombosis or clots in central venous catheters. According to the literature, an initial dosage of 0.1 mg/kg/d should provide anticoagulation without significant adverse effects. As in adults, dosing should be adjusted to achieve a target international normalized ratio (INR). Although the target range in children is not well established, INR values of 1.5-3 are recommended for most patients. Higher values have been used in children with prosthetic cardiac valves and hereditary clotting disorders.

CONCLUSIONS

Due to its infrequent use, there is limited information on the effects of warfarin in children. Basic guidelines for initiating and monitoring warfarin were developed by using data gathered from clinical trials, retrospective reviews, case series, and surveys of practice.

Thrombosis and embolism

Prevention offers the best approach to limiting morbidity and mortality from deep vein thrombosis and pulmonary embolism in obstetric patients. The use of anticoagulant drugs during pregnancy, however, can be problematic, from the maternal or the fetal point of view. Deciding on the best management is further limited by the lack of controlled clinical trials in the obstetric setting. From the data available, it can be recommended that anticoagulant prophylaxis should be targeted at groups of patients at high risk of thrombosis during pregnancy and the puerperium. Heparin is the agent of choice in most situations during pregnancy for the prophylaxis of venous thrombosis, while warfarin is still the most effective agent for the prevention of systemic embolism from artificial cardiac valves. Prophylactic measures against venous thrombosis are probably underused in the puerperium. Controlled clinical studies are urgently required to optimize prophylaxis of venous thromboembolism associated with pregnancy, and large studies may be more feasible in the puerperium when the incidence of thromboembolism is highest.