Page 448 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

318 PART 3: Cardiovascular Disorders

KEY REFERENCES • While low-molecular-weight heparin (LMWH) is approved and
• Craig ML. Management of right ventricular failure in the era of recommended as the initial therapy for PE, critically ill patients
ventricular assist device therapy. Curr Heart Fail Rep. 2011;8:65-71. often have reason for a shorter-acting medication. Unfractionated
• Hamon M, Agostini D, Le Page O, et al. Prognostic impact of right heparin is typically used to maintain the partial thromboplastin
ventricular involvement in patients with acute myocardial infarc- time (PTT) at 1.5 to 2.5 times control.
tion: meta-analysis. Crit Care Med. 2008;36:2023-2033. • Thrombolytic therapy is lifesaving and possibly in those with isolated
• Hoeper MM, Granton J. Intensive care unit management of RV dysfunction in patients with massive embolism and circulatory
patients with severe pulmonary hypertension and right heart instability, but does not seem beneficial in patients without shock.
failure. Am J Respir Crit Care Med. 2011;184:1114-1124. • Air and fat embolism usually present as acute respiratory distress
https://kat.cr/user/tahir99/
• Kerbaul F, Rondelet B, Demester JP, et al. Effects of levosimendan syndrome (ARDS), and are managed with mechanical ventilation,
versus dobutamine on pressure load-induced right ventricular oxygen, and positive end-expiratory pressure (PEEP).
failure. Crit Care Med. 2006;34:2814-2819.
• Mahjoub Y, Pila C, Friggeri A, et al. Assessing fluid responsive-
ness in critically ill patients: false-positive pulse pressure variation This chapter covers diseases involving embolism to the pulmonary
is detected by Doppler echocardiographic evaluation of the right circulation, including pulmonary thromboembolism, as well as the
ventricle. Crit Care Med. 2009;37:2570-2575. less common conditions of venous air embolism and fat embolism.
• Mekontso DA, Boissier F, Leon R, et al. Prevalence and prognosis Thromboembolism is predominantly an acute circulatory insult, with
of shunting across patent foramen ovale during acute respiratory important but less dramatic consequences for gas exchange. In contrast,
distress syndrome. Crit Care Med. 2010;38:1786-1792. both air and fat embolism usually present as acute hypoxemic respira-
• Mertens LL, Friedberg MK. Imaging the right ventricle—current tory failure (AHRF). All three of these forms of embolism may cause
state of the art. Nat Rev Cardiol. 2010;7:551-563. acute right heart failure, more fully discussed in Chap. 38.
• Pagnamenta A, Fesler P, Vandinivit A, et al. Pulmonary vascular
effects of dobutamine in experimental pulmonary hypertension. PULMONARY THROMBOEMBOLISM:
Crit Care Med. 2003;31:1140-1146. EPIDEMIOLOGY IN THE ICU
• Taylor RW, Zimmerman JL, Dellinger RP, et al. Low-dose inhaled
nitric oxide in patients with acute lung injury: a randomized PE is a dramatic and life-threatening complication of underlying deep
controlled trial. JAMA. 2004;291:1603-1609. venous thrombosis (DVT). Therefore, much of the management of PE
• Yerebakan C, Klopsch C, Niefeldt S, et al. Acute and chronic is grounded in the prophylaxis, diagnosis, and treatment of DVT. While
extensive prospective data regarding the diagnosis and treatment of PE
response of the right ventricle to surgically induced pressure are available, the vast majority of patients in such trials have not been
and volume overload—an analysis of pressure-volume relations. critically ill, and thus the treatment for ICU patients with thrombo-
Interact Cardiovasc Thorac Surg. 2010;10:519-525.
embolic disease relies on extrapolation, and may lack the strength of
evidence now available for most patients with PE or DVT. Nonetheless,
important distinctions exist between the critically ill and noncritically
REFERENCES ill patient populations when considering PE diagnosis and treatment.
Pulmonary thromboembolism is a common illness, which accounts
Complete references available online at www.mhprofessional.com/hall for substantial morbidity and mortality. Interesting trends have been
recently reported regarding the incidence of PE. Historically, acute PE
was believed to be frequently underdiagnosed, and a frequent cause of
Pulmonary Embolic
CHAPTER unexplained sudden death, as it was estimated that up to 25% of patients
1
may die before admission. However, a recent time-trend analysis using an
39 Disorders: Thrombus, administrative database demonstrated a dramatic increase in PE incidence
Air, and Fat
in the United States, from approximately 62 cases per 100,000 popula-
2
was coincident with the introduction and adoption of multidetector
Nuala J. Meyer tion to over 113 cases per 100,000. This change in the incidence of PE
Gregory A. Schmidt row computed tomographic scanning as a primary diagnostic modal-
ity for PE, raising the possibility that PE is now overdiagnosed, given
that across the same period, the mortality rate was unchanged and case
2
KEY POINTS fatality rates fell. The use of the term overdiagnosis remains controver-
sial as small and even asymptomatic PEs can recur, albeit at apparently
• Pulmonary embolism (PE) is common and potentially lethal, yet much lower rates. Failure to diagnose symptomatic PE remains a
3,4
readily treatable. serious management error since it has been estimated that over 30% of
• Prophylaxis and accurate diagnosis are essential to improving outcome. untreated patients die, while only 8% succumb with effective therapy. 5-7
• The cause of death in PE is most often circulatory failure (acute cor ICU patients are an inhomogeneous group of patients and the
pulmonale) due to right heart ischemia. incidence of thromboembolism ranges widely across subsets of patients.
For general medical/surgical ICU patients, the incidence of DVT is
• There is no perfect diagnostic test for PE; accurate diagnosis approximately 30% based on screening studies. As discussed below,
8,9
requires both an informed clinical pretest probability and a step- prophylaxis of these patients lowers the risk of VTE and has become
wise application of helical CT angiography and/or LE duplex. standard practice in most units; a large registry of hospitalized patients
• A careful risk assessment may identify patients ideal for outpatient with DVT found that the majority had not received prophylaxis prior to
therapy. Conversely, patients with hypotension or right ventricular their DVT diagnosis. Additional risk factors, discussed in more detail
10
strain are at significantly higher risk for death from PE, and war- below, include advancing age, malignancy, and presence of an indwelling
rant ICU admission. venous catheter or pacemaker. Many ICUs now protocolize prophylaxis
decisions in an effort to increase adherence to prophylaxis guidelines.

section03.indd 318 1/23/2015 2:07:29 PM