Page 1020 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 81: Biological Warfare 751

antigen as well as IgM and IgG antibodies. Reverse transcriptase PCR clinical, but serum detection of the toxin is possible with ELISA. Therapy
has also been successfully applied to field diagnosis. 47-49 is currently limited to supportive care. 53,54
Medical management for VHF is largely supportive. Patients should The viral equine encephalitides include Venezuelan, eastern, and
be handled as gently as possible as they are especially prone to western viruses (VEE, EEE, and WEE) of the alphavirus family. Humans
bleeding. Aspirin and other antiplatelet drugs should be avoided. are accidental hosts, acquiring the virus via a mosquito vector. However,
Immunosuppression with steroids or other agents is contraindicated. they are highly infectious by aerosol and readily grow in cell cultures.
Uncontrolled clinical observations support the transfusion of red All three of the viruses are capable of killing with varying degrees of
cells for severe hemorrhage and platelet and clotting factors for DIC. neurologic involvement. EEE is most virulent with 50% to 70% mortal-
Hemodialysis is of particular help in treatment of HFRS. 47-49 ity, WEE follows with <10% mortality, and VEE has <1% mortality. A
The only specific antiviral therapy available for VHF is ribavirin, a febrile prodrome of 1 to 5 days marks replication in bone marrow and
nonimmunosuppressive nucleoside analogue with broad antiviral prop- lymphoid tissue resulting in lymphopenia. Subsequently high viremia
erties. It has been shown to reduce mortality in Lassa fever and shows seeds the brain and spinal cord. Central nervous system symptoms and
promise with the treatment of other arena- and bunyaviruses. Passive signs include menigismus, hyper- or hypoactive reflexes, and spastic
immunotherapy has been used successfully in Argentine hemorrhagic paralysis that can progress to death. Loss of airway protection and status
fever and shows promise in Bolivian hemorrhagic fever. However, epilepticus may require mechanical ventilation and ICU management.
passive immunization is contraindicated in HFRS since an active CSF shows elevated protein and 50 to 2000 WBCs/mL with lymphocyte
immune response is already evolving in most patients who are diagnosed. predominance. Definitive diagnosis relies on viral culture of serum or
Currently the only licensed vaccine is for yellow fever and is mandatory CSF, or antibody detection from serum by ELISA. Therapy is limited
for all travelers to endemic areas. 47-50 to supportive treatment. A live-attenuated vaccine for VEE is available,
Isolation of suspected VHF cases is essential as secondary infections along with inactivated vaccines for VEE, WEE, and EEE. These vaccines
of close contacts and medical personnel are well documented. Until the are available under investigational new drug (IND) release status from
definitive diagnosis has been made, patients with suspected VHF should the US government but are only 50% to 85% effective for <1 year. 55-57
be isolated in a single room with an adjoining anteroom serving as an Ricin toxin is an extract of castor beans. It is highly lethal via inges-
entrance. Negative pressure rooms and strict respiratory precautions may tion, injection, and inhalation. At the cellular level it kills through the
be more appropriate in confirmed severe end-stage disease where the inhibition of protein synthesis. Its clinical features are route-specific.
viral load is maximal. These precautions may not be possible in the case Studies in primates show that within several hours of inhalation a severe
of large outbreaks. However, it is essential to enforce stringent barrier diffuse acute tracheobronchitis manifests, followed by fibrin purulent
nursing, with the use of mask, glove, gown, and needle precautions, along pneumonia with diffuse severe alveolar flooding, peribronchovascular
with hazard labeling of all laboratory specimens. Patient access should be edema, and mediastinal lymphadenitis. Respiratory failure and ARDS
restricted and the incineration or autoclaving of all contaminated materi- are likely to occur within 30 hours. Distinguishing an attack with ricin
als including linens is mandatory. Decontamination of areas can likely from either anthrax or pneumonic plague would be extremely difficult.
be carried out by detergents, bleach, and hypochlorite solutions, as these Diagnosis would be largely clinical, but antigen ELISA of nasal swabs
viruses have lipid envelopes making them susceptible. 47-50 should be done within 24 hours. Treatment would be largely supportive,
though vaccination with a toxoid in animals is very effective and in
CATEGORY B AGENTS development by the U.S. Army. 54
Discussion of all the possible biological weapons is beyond the scope of
this chapter. However, Coxiella burnetii (Q fever), staphylococcal entero- ROLE OF CRITICAL CARE IN BIOTERRORISM
toxin B (SEB toxin), viral equine encephalitides, and ricin toxin deserve The scenario of a biological weapons attack poses several unique chal-
attention, as they have been weaponized. Furthermore they can all present lenges for the intensivist. Although most external disasters will occur
as an upper respiratory viral illness, making differentiation of biological with some degree of warning, biological agent exposure is an exception.
attack from a natural viral epidemic difficult (see Table 81-3). 51 Here the diagnosis is more likely to be made within a hospital, perhaps a
Q fever is a zoonotic disease of herded animals. Humans acquire it few days after the environmental release. Potentially, enormous numbers
via inhalation. It is extremely infectious, requiring as few as 10 organ- of ill and exposed patients presenting with the same level of severity will
isms to produce disease. The incubation time is 2 to 14 days. Patients rapidly overwhelm the health care system, its infrastructure, and sup-
present with signs and symptoms of a seasonal viral syndrome that can plies. Issues of supplies and distribution of medical resources would be a
be prolonged in two-thirds for up to 2 weeks. The most frequent physi- major problem, as already predicted in the TOPOFF exercise. 27
cal finding is rales on chest exam. Chest x-rays are abnormal in 50% The need for the critical care personnel to be involved in the planning
to 60% of cases, most often showing consolidation, but effusions also process cannot be overstated. The intensivist will become a key figure in
occur. Routine blood tests commonly show elevations of liver transami- governing the flow of patient traffic, making triage decisions, and allocat-
nases and alkaline phosphatase up to three times normal. Fatalities are ing ICU resources for patients in the ER, OR, recovery room, and the rest
extremely rare; however, the disease is incapacitating. Treatment and of the hospital. Intensivists should understand capabilities, resources, and
prophylaxis is with doxycycline or tetracycline. 51-53 limitations of various governmental and nongovernmental disaster-related
SEB is a heat-stable pyrogenic toxin produced by Staphylococcus agencies, as well as consider their hospital’s location and community
aureus. This toxin can be mass produced and is stable as an aerosol. resources in anticipating a likely disaster scenario. 58
When inhaled it binds to the MHC class II molecules that stimulate Although the full details of a hospital’s preparedness plan are beyond
T cells with a massive release of cytokines including interferon-γ, inter- the scope of this chapter, certain key issues deserve attention in coping
leukin-6, and tumor necrosis factor (TNF)-α. Within 3 to 12 hours of with such a disaster. 4
exposure, high fever (up to 106°F), myalgias, nonproductive cough, chest
tightness, dyspnea, headache, and vomiting develop. Conjunctival signs 1. Define the area to be covered during a disaster scenario. Intensivists
are notably absent. On chest examination, rales are the prominent find- should familiarize themselves with their hospital disaster plan, and
ing. Chest x-ray typically is normal, but can show interstitial pulmonary know their responsibilities relative to other departments in the plan.
edema. Postural hypotension as well as profound vasodilatory shock 2. Identification and assignment of key personnel in the hospital,
can occur. Patients usually progress rapidly to a relatively stable level of emergency response personnel, state and local authorities, and key
disease, but can be incapacitated for weeks. Lethality is low. Diagnosis is members of the community.

section05_c74-81.indd 751 1/23/2015 12:37:45 PM