Pulmonary embolism

What an practising Obstetrician should know on Thromboembolism??

Point 1:-DVT remains a leading cause of obstetric morbidity and mortality.

. Point 2:- It is the hypercoagulable nature of pregnancy is the prime cause: of DVT & PE . Point 3 The hypercoagulable nature of pregnancy It remains more common in the postpartum period than during pregnancy. It is now recognized that a significant portion of these thrombotic events occur as early as the first trimester, it is prudent to start treatment soon after the pregnancy is recognized and viability confirmed, and continue until 6 weeks post delivery.

 . Point 4 Why DVT is more common in Pregancy??  The increased prevalence is due to arterio of equilibrium or balance of procoagulant and anticoagulant factors in the circulation pendulum favoring  toward clot formation during pregnancy. Under normal circum­stances, the increased levels of clotting factors do not result in thrombus formation, but some clinical situations such as trauma or vascular injury may predispose toward lower extremity clotting. Point 5 :- Other risk factors for thrombosis during pregnancy include venous status, inactivity, obesity, prior thrombosis, antiphospholipid syndrome and thrombophilias such as factor V Leiden mutation.

It is estimated that the risk of venous thrombosis is approximately five times higher during pregnancy than in the non­pregnant state due to the hypercoagulable nature of pregnancy. While previously thought to be more prevalent in the third trimester, it is now recognized to occur at similar frequencies throughout pregnancy. Point: 6:-  Despite its risk, thromboembolism during pregnancy is a poorly studied area and significant controversy remains over the management of pregnant women at risk for this disorder.

current pregnancy	control) for 5-10 days, followed by q 8-12 h injections to prolong midinterval aPTT 1 VS times control for remainder of the pregnancy; warfarin can be used postpartum	100 mg maximum) q 12 h; monitoring of anti-Factor Xa levels at 4-6 hours post injection
Patient who requires	Heparin q 8-12 h to prolong	1 mg/kg (up to 100 mg
long-term therapeutic	mid-interval aPTT 1 VS times	maximum) q 12 h;
anticoagulation	control	monitoring of anti-Factor Xa levels at 4-6 hours post injection
Previous DVT or PE	5000 units q 12 h first trimester	40 mg q 12 h; monitoring
before current	7500 units q 12 h second trimester	unnecessary for patients
pregnancy (prophylactic treatment)	10,000 units q 12 h third trimester; monitoring unnecessary	under 100 kg

That prophylactic anticoagulation  1) may not be necessary in some patients with a history of venous thromboembo­lism   Significantly increases the risk of recurrence. Anticoagulant doses lower than needed to prolong the aPTT have been used unless the patient is thought to be at such increased risk that full anticoagulation is necessary. Because it is now recognized that a significant portion of these thrombotic events occur as early as the first trimester, it is prudent to start treatment soon after the pregnancy is recognized and viability confirmed, and continue until 6 weeks post delivery.

A recent study suggested that prophylactic anticoagulation may not be necessary in some patients with a history of venous thromboembo­lism. In this study of women with a single previous episode of thrombosis associated with a temporary risk factor (e.g., oral contraceptives, surgery, trauma), and no recognized thrombophilia, no recurrences were seen without treatment during pregnancy. However, the number of patients in this study was relatively small. Larger studies in the future may fur­ther support the idea that prophylactic treatment with anticoagulants is unnecessary for this type of patient.

Risks to the mother from heparin therapy include a rare thrombocy­topenia and the possibility of heparin-induced osteoporosis. These risks are thought to be lower with the use of low molecular weight heparin. Heparin-induced thrombocytopenia occurs within the first week of treat­ment, so checking the platelet count 5 to 10 days after beginning therapy will provide reassurance. Up to one-third of women may demonstrate subclinical bone loss and the reversibility of this process is not assured. Significant maternal hemorrhage is a possibility in patients that are over- ant coagulated.

Special considerations

Patients with artificial heart valves are at a high risk for thromboembo­lism, stroke and valve failure and, therefore, must be therapeutically ant coagulated throughout pregnancy. Patients with a documented clot and also a family history of thromboembolic events should be evaluated for antithrombin-III, protein C or protein S deficiency because these traits are autosomal dominant with variable penetrance. Full-dose anticoagulation should be used when these conditions are identified. It is more difficult to diagnose protein S deficiency in pregnancy since levels normally decrease beginning in the first trimester; prophylaxis may be appropriate if pro­tein S deficiency is suspected. Patients with a prior thromboembolic event who have been diagnosed with antiphospholipid antibody syndrome should be given heparin prophylaxis at a minimum, with consideration of full anticoagulation for those thought to be at significant risk. Screening for factor V Leiden and prothrombin mutation should not be performed in patients without a history of prior thrombosis, as patients with these mutations without prior thrombotic events do not need treatment. Patients with mutations of more than one factor (double heterozygote’s or those homozygous for mutation) are thought to be at high risk for thrombosis, and treatment is warranted.

There is concern regarding the use of epidural anesthesia during labor and delivery in patients treated with anticoagulants. Some anesthesiologists suggest avoiding regional anesthesia for 12-24 hours from the last injection of low molecular weight heparin, especially if full-dose treatment is used. Because of its more rapid disappearance, a shorter waiting time is used for patients on heparin, and these patients can receive regional anesthesia when laboratory tests confirm a normal PTT result. For this reason, switch­ing from low molecular weight to standard heparin at 36 weeks' gestation may increase the number of patients eligible for regional anesthesia.

Pathophysiology-of thrombosis--Normal pregnancy is associated with an increase in the level or activ­ity of many of the clotting factors in the blood. These increases provide a defense against hemorrhage after delivery, but they also contribute to thrombus formation. Once formed, portions of the clot can emblaze  to the pulmonary tree, with symptoms rang­ing from mild hypoxia to cardiovascular collapse. With mild to moderate symp & few signs... LMWH vs  Enoxaparin:-  injections are also given twice daily because of the rapid metabolism. Monitoring of enoxaparin when given outside of pregnancy is thought to be unnecessary for most patients, but its pharmacokinetics in pregnancy are incompletely studied. If monitoring is to be performed, anti- factor Xa levels are followed, with the target being 0.6 to 1.0 IU/mL. Both heparin and low molecular weight heparins do not cross the placenta, but warfarin does due to its smaller size. Warfarin is contraindicated in preg­nancy due to its fetopathic (toxic effects on foetus) (toxic effects on foetus) effects in the first trimester (stippled epiphyses and nasal and limb hypoplasia) and the risk of fetal bleeding complica­tions in the second and third trimesters.

In postpartum period :-However, warfarin does not enter breast milk in sufficient quantities to anticoagulant the newborn, and is safe to use in the breastfeeding mother. For the patient needing full anti­coagulation who prefers to take warfarin rather than frequent injections during the postpartum period, the INR is followed.

Prevention of thromboembolism

The use of anticoagulation to prevent thromboembolism is more con­troversial. Traditionally, chemoprophylaxis has been recommended to pregnant patients with a history of thrombosis with the idea that pregnancy.

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What are the clinical features of DVT(Deep Venous Thrombosis)?

. Patients presenting with symmetric lower extremity swelling associated with A) pain and B) erythema should be usually be evident in DVT in big vessels like IVC.

Lab Diagnosis:- A) impedance plethysmography:-- impedance plethysmography compres­sion ultrasonography for pregnant women as the primary tool for evalu­ation of clinical symptoms in the lower extremities.  Use of Doppler also enables evaluation of thrombosis in the iliac veins . Ultrasonography is less sensitive for thrombosis below the knee. 3) Venography But Venography  once a traditionally recognized method  which was a  gold standard for making the diagnosis, even in pregnancy  but is performed less frequently now because of its invasive nature and its use of radiation.

. But all these modalities are less frequently today (i.e. impedance plethysmography, Venography)   and people are insisting on B) serum D-dimer for PE cases mainly  :--Assays for serum D-dimer are useful for detecting thrombosis outside of pregnancy because of its high negative predictive value, but of limited value in pregnancy because most women have increased lev­els by the second trimester. C) MRI use may become more common, especially for evaluation for pelvic vein thrombosis D)

?DVT

MRI or
venography

.

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Symptoms and signs of PE:_The presenting signs and symptoms suggestive of pulmonary embo­lism include A) shortness of breath, B) chest pain, C) tachypnea, D) tachycardia and  E)  decreased oxygen saturation by pulse oxymeter.

Lab tets what to do?? A)  Arterial blood gas to determine the presence of hypoxia and increased A-a gradient, both suggestive of an embolic event. However, this test is now recognized as having limited value in that many patients with pulmonary embolism are without this  abnormality. B) Spiral CT scanning using IV contrast is now the primary diagnostic modality for non-pregnant patients in many centers; its use in pregnancy has not been evaluated, but is likely to be of similar accuracy as in the non-pregnant state. It may also be of use in identifying other thoracic conditions that may be responsible for the patient's symptoms. Fetal radiation exposure has been estimated to be less than 1 rad, and less than that associated with ventilation-perfusion scan­ning  Ventilation- perfusion (V/Q) scanning but more than half of V/Q scans performed in pregnancy are non-diagnostic and require further imaging’s)  Pulmonary angiography is the gold standard for diagnosing pulmonary embolus, but is invasive and associated with a risk of significant complications. D)  . If a diagnosis of pulmonary embolism is made, a search for lower extremity thrombosis may be helpful in identifying the precipitating cause and directing therapy.

What is the basic Tr before she is shifted to a referral hospital or ICU from a different buildings? Treatment of acute thromboembolism: full anti­coagulation using either intravenous heparin or subcutaneous low molecu­lar weight heparin, and it is important to achieve therapeutic doses very early to prevent extension of clot. Later, the patient is then transitioned to either subcutaneous heparin or enoxaparin (or other forms of low molecular weight heparin) injections every 12 hours, which is con­tinued for the remainder of the pregnancy and postpartum period to pre­vent recurrence. Tithe use of heparin injections requires monitoring to maintain the activated partial thromboplastin time (aPTT) at least 1.5  times control throughout the dosing interval. the more rapid metabolism of heparin during pregnancy, it is usually difficult to achieve prolongation of the aPTT throughout the dosing inter­val without an excessive peak level, even when administered three times a day.

Condition	Heparin	Enoxaparin
DVT or PE during	IV heparin (aPTT 2-3 times	Enoxaparin 1 mg/kg (up to
current pregnancy	control) for 5-10 days, followed by q 8-12 h injections to prolong midinterval aPTT 1 VS times control for remainder of the pregnancy; warfarin can be used postpartum	100 mg maximum) q 12 h; monitoring of anti-Factor Xa levels at 4-6 hours post injection
Patient who requires	Heparin q 8-12 h to prolong	1 mg/kg (up to 100 mg
long-term therapeutic	mid-interval aPTT 1 VS times	maximum) q 12 h;
anticoagulation	control	monitoring of anti-Factor Xa levels at 4-6 hours post injection
Previous DVT or PE	5000 units q 12 h first trimester	40 mg q 12 h; monitoring
before current	7500 units q 12 h second trimester	unnecessary for patients
pregnancy (prophylactic treatment)	10,000 units q 12 h third trimester; monitoring unnecessary	under 100 kg

That prophylactic anticoagulation  1) may not be necessary in some patients with a history of venous thromboembo­lism   Significantly increases the risk of recurrence. Anticoagulant doses lower than needed to prolong the aPTT have been used unless the patient is thought to be at such increased risk that full anticoagulation is necessary. Because it is now recognized that a significant portion of these thrombotic events occur as early as the first trimester, it is prudent to start treatment soon after the pregnancy is recognized and viability confirmed, and continue until 6 weeks post delivery.

A recent study suggested that prophylactic anticoagulation may not be necessary in some patients with a history of venous thromboembo­lism. In this study of women with a single previous episode of thrombosis associated with a temporary risk factor (e.g., oral contraceptives, surgery, trauma), and no recognized thrombophilia, no recurrences were seen without treatment during pregnancy. However, the number of patients in this study was relatively small. Larger studies in the future may fur­ther support the idea that prophylactic treatment with anticoagulants is unnecessary for this type of patient.

Risks to the mother from heparin therapy include a rare thrombocy­topenia and the possibility of heparin-induced osteoporosis. These risks are thought to be lower with the use of low molecular weight heparin. Heparin-induced thrombocytopenia occurs within the first week of treatment, so checking the platelet count 5 to 10 days after beginning therapy will provide reassurance. Up to one-third of women may demonstrate subclinical bone loss and the reversibility of this process is not assured. Significant maternal hemorrhage is a possibility in patients that are over- ant coagulated.

Special considerations

Patients with artificial heart valves are at a high risk for thromboembo­lism, stroke and valve failure and, therefore, must be therapeutically ant coagulated throughout pregnancy. Patients with a documented clot and also a family history of thromboembolic events should be evaluated for antithrombin-III, protein C or protein S deficiency because these traits are autosomal dominant with variable penetrance. Full-dose anticoagulation should be used when these conditions are identified. It is more difficult to diagnose protein S deficiency in pregnancy since levels normally decrease beginning in the first trimester; prophylaxis may be appropriate if pro­tein S deficiency is suspected. Patients with a prior thromboembolic event who have been diagnosed with antiphospholipid antibody syndrome should be given heparin prophylaxis at a minimum, with consideration of full anticoagulation for those thought to be at significant risk. Screening for factor V Leiden and prothrombin mutation should not be performed in patients without a history of prior thrombosis, as patients with these mutations without prior thrombotic events do not need treatment. Patients with mutations of more than one factor (double heterozygote’s or those homozygous for mutation) are thought to be at high risk for thrombosis, and treatment is warranted.

There is concern regarding the use of epidural anesthesia during labor and delivery in patients treated with anticoagulants. Some anesthesiologists suggest avoiding regional anesthesia for 12-24 hours from the last injection of low molecular weight heparin, especially if full-dose treatment is used. Because of its more rapid disappearance, a shorter waiting time is used for patients on heparin, and these patients can receive regional anesthesia when laboratory tests confirm a normal PTT result. For this reason, switch­ing from low molecular weight to standard heparin at 36 weeks' gestation may increase the number of patients eligible for regional anesthesia.