Page 462 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

332 PART 3: Cardiovascular Disorders

this complication is more common than previously thought. With no Treatment: The use of heparin in pregnancy is no different than in the
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prospective data, it is unclear whether embolectomy confers any advan- nonpregnant patient. Heparins do not cross the placenta, and are low
tage over thrombolytic therapy, or for that matter, heparin. The patients risk to the fetus. However, coumadin, which is teratogenic, should not
most likely to benefit from embolectomy are those who meet the follow- be instituted. Rather, long-term treatment should consist of subcutane-
ing criteria: having a hemodynamically significant embolism, in whom ous heparin or LMWH. 168,169 LMWHs are preferred in that they have
thrombolytic therapy is contraindicated, and in a center with a rapidly a lower incidence of both bleeding and of heparin-induced thrombo-
responding cardiopulmonary bypass team and a surgeon experienced in cytopenia. Osteoporosis is a serious complication of full-dose heparin
the technique of embolectomy. during pregnancy with fractures occurring in 2% of women. There
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Several new devices have been tested which aim to remove pul- are indications that bone mineral loss is reversible, but several cases
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monary emboli less invasively than the direct surgical approach. For of debilitating back pain have been reported. LMWHs, when prospec-
example, a 10F suction catheter, inserted through a jugular or femoral tively studied, do not appear to accelerate bone mineral density loss.
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venotomy and advanced into the pulmonary artery, has been used to Thrombolytic therapy risks spontaneous abortion and uterine bleeding.
extract clot. Eleven of 18 patients improved immediately. Suction Nevertheless, several case reports of the successful use of thrombolytic
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embolectomy was more likely to be successful in patients treated treatment of PE have appeared. Vena caval interruption requires some
promptly after hemodynamic deterioration. More recently, patients modification as well. The left ovarian vein (a potential source of clot)
with shock underwent mechanical fragmentation of their massive PE drains into the left renal vein. Therefore, when a caval filter is placed, it
with a rotational pigtail catheter, followed by thrombolytic therapy. should be inserted to a suprarenal position, rather than below the renal
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Nine of 10 patients survived, and 6 of the survivors achieved hemody- veins. Again, several cases of successful use of these devices have been
namic stability within 48 hours of the procedure. Alternative methods described. Pregnancy may be an ideal situation for the temporary vena
to reestablish pulmonary artery patency include endovascular stents. caval interruption device.
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A meta-analysis of all published reports of modern catheter—directed
therapy (CDT), using catheters smaller than 10F and post-1990, ■ CHRONIC OBSTRUCTIVE PULMONARY DISEASE
for massive PE reported that CDT was effective at reversing shock,
resolving hypoxemia, and surviving the hospitalization, for 86% of Patients with COPD are at increased risk for PE. In addition, their preex-
patients. The complication rate was reasonably low, with a 2.4% isting respiratory compromise and abnormal pulmonary vasculature leave
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major complication rate. The authors noted that one device in par- them particularly vulnerable to the cardiopulmonary consequences of
ticular, a type of Angiojet, was associated with a significantly higher PE. Ironically, diagnosis of PE in the setting of COPD is unusually dif-
complication rate and has been issued an additional warning by the ficult. Patients commonly complain of dyspnea, chest pain, cough and
FDA. While the authors advocated the consideration of CDT as anxiety, and occasionally note hemoptysis and leg swelling. Their exami-
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first line therapy for patients with massive and potentially submassive nations, chest radiograms, ECGs, and arterial blood-gas values are usually
PE, their meta-analysis included no randomized trials, raising the abnormal at baseline. V/Q scans are most often unhelpful. For example, in
specter of selection bias, and their own analysis pointed to evidence PIOPED 108 patients were identified as having COPD (although objective
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of publication bias. Accordingly, the most recent ACCP guidelines data were available in only 43). Scans were intermediate probability in a
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reserve CDT for patients deemed too high risk for conventional full 60%. Only 20 patients (19%) had results which made pulmonary angi-
thrombolysis; when thrombolysis has failed; or for whom there is inad- ography unnecessary by being normal, high probability, or low probability
equate time to give the thrombolytic dose, and recommend that it be paired with a low pre-test clinical estimate. Nevertheless, for the occa-
done only at centers with considerable expertise. 41 sional patient, V/Q scan obviated pulmonary angiography.
When patients with COPD present with symptoms which are atypi-
cal for their usual exacerbation, particularly when the Paco is reduced
2
SPECIAL CONSIDERATIONS from previously elevated values, it is worth considering the diagnosis.
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■ PREGNANCY Positive leg studies may provide a rationale for anticoagulation and
obviate the need for further investigation, although this approach has
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The pregnant woman who may have PE presents unique challenges. been called into question. CTPA or pulmonary angiography may be
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Pregnancy is thought to be a risk factor for venous thrombosis, and PE is necessary to establish a diagnosis.
the second leading cause of death among gravidas, following trauma.
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The addition of the fetus, as well as anatomic considerations, leads to ■ PATIENTS WITH COAGULATION OR PLATELET DISORDERS
several key differences in management. The risk of venous thromboembolism in patients with chronic liver dis-
Diagnosis: Diagnosis can be more difficult because of reluctance to ease or marked thrombocytopenia is not known. While it seems sensible
perform potentially risky procedures, particularly involving diagnostic to conclude that the risk must be lower than if clotting and platelet
radiology. However, it is important not to lose sight of the risk of failing function were normal, PEs occur even when the bleeding tendency is
to make the diagnosis. Thus, when the diagnosis is seriously considered, severe. 176,177 Therefore, when the clinical presentation strongly suggests
it should be pursued. V/Q scans probably pose little risk to the fetus. The PE, thrombocytopenia and coagulopathy should provide little reassur-
estimated radiation dose is small, and the risk is clearly less than that of ance, and diagnostic testing is indicated. Patients with chronic renal
missing a diagnosis. For gravidas with a normal chest radiograph, the failure—excepting those with nephrotic syndrome—do seem to be at
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most recent ATS and Society of Thoracic Radiology Guidelines recom- a remarkably low risk of venous thromboembolism, so that alternative
mend lung scintigraphy as the next diagnostic test, rather than lower diagnoses should always be sought.
extremity ultrasound or CTPA. The risk of helical CT angiography
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is not known, but when indicated, it should not be withheld out of PROPHYLAXIS AGAINST VENOUS
concern of fetal radiation exposure. The maternal risks of undiagnosed THROMBOEMBOLISM
and untreated PE are clear. A diagnosis of thromboembolism in preg-
nancy has serious implications for the mother, not just in the current A discussion of prophylaxis has been left to the end of the section on
pregnancy, but during any subsequent pregnancies. Because of the risk thromboembolism because here it is particularly easy to emphasize sev-
of heparin-induced osteoporosis and the remaining uncertainties about eral points. PE is common, lethal, usually missed, difficult to evaluate,
effective prophylaxis against recurrence during future pregnancies, and costly to treat. Critical illness makes these statements especially true.
the diagnosis of thromboembolism should never be made lightly in a Therefore, the goal must be to prevent this disease. A full treatment of
gravida, but instead should be based on solid evidence. prophylaxis against VTE is beyond the scope of this chapter, but a few

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