Page 36 - Journal of Special Operations Medicine - Fall 2016

to 60% of patients requiring dialysis ; and (2) abnor- confusion, somnolence, seizure, or aphasia. Physical ex-
5
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malities in the complement system occur in up to 90% amination may be notable for signs of anemia to include
of individuals with aHUS, although 30%–50% may go conjunctival or general pallor and delayed capillary refill.
unidentified because current assays cannot identify the The patient may have jaundice or scleral icterus second-
defect. This patient had profound thrombocytopenia, ary to hemolysis. Purpura and prolonged bleeding time
6
mild renal involvement, and no identified complement are indicators of a platelet or coagulation deficiency.
deficiencies.
Given this history and examination in the absence of
Idiopathic TTP with normal ADAMTS13 activity is a trauma or other clear etiology, a provider should con-
potential diagnosis. Literature suggests the sensitivity of sider TMA syndrome as a potential diagnosis. Point-
ADAMTS13 <5%–10% for diagnosis of TTP is about of-care hemoglobin and hematocrit values can be used
60%, ranging from 33% to 100%. 9–12 This wide re- to define the degree of anemia. If basic laboratories are
ported variability led to significant discussion about the available, a complete blood count and chemistry should
ability of ADAMTS13 deficiency to differentiate TTP be obtained. Severe anemia and thrombocytopenia si-
from other TMA syndromes. The cause of the variation multaneously significantly increase the likelihood of
is not known, but may be due to different ADAMTS13 TMA syndrome. Hyperkalemia and elevated blood urea
assays, case definitions, or differing rates of diagnosing nitrogen and creatinine levels are signs of renal failure.
secondary causes of TTP. Considering this, more recent
guidelines and expert consensus now suggest almost all Initial treatment consists of maintaining adequate tissue
cases of nonfamilial idiopathic TTP have ADAMTS13 perfusion. If the patient has hypotension, administra-
activity <5%–15%. 5,7,13 Although this threshold of tion of intravenous fluids should be instituted. Blood
ADAMTS13 activity suggests idiopathic TTP is unlikely transfusions should not be delayed if a TMA syndrome
in this patient, cases of TTP with normal ADAMTS13 is suspected. A specific hemoglobin level at which to
activity are described, and this patient may be another initiate transfusion is ultimately dependent on available
representation of such disease. 6,12 resources, but a hemoglobin of <7g/dL is a reasonable
threshold. Packed red blood cells are an initial treat-
This discussion highlights the continued difficulty in dif- ment; however, platelets, fresh frozen plasma, or whole
ferentiating aHUS and idiopathic TTP. This case likely blood transfusion may be necessary as TMA syndromes
represents an atypical TMA syndrome of unclear eti- are a consumptive process of red blood cells, platelets,
ology. Identification of a specific TMA syndrome can and coagulation factors. Platelet transfusions in this di-
be important for treatment and prognosis. Plasma ex- agnosis can increase the risk for thrombosis and should
change remains a mainstay of TTP treatment; however, only be considered in the setting of active bleeding and
new directed therapies for non-TTP/TMA may have re- if more definitive diagnosis and therapy are not immedi-
duced morbidity. Specifically, in complement-mediated ately available. Additionally, the broadest-spectrum an-
TMA, often referred to as aHUS, the complement neu- tibiotics available should be administered for potential
tralizing antibody to C5, eculizumab, has shown ben- sepsis-induced DIC.
efit. In small initial trials, time-dependent improvements
in renal function and discontinuation of dialysis in four When considering evacuation, it is important to remem-
of five patients was observed with eculizumab therapy. ber that the condition will persist until the underlying
14
etiology is treated. Therefore, a medic should anticipate
TMA syndromes also present challenges of diagnosis continued blood product requirements. If uncertain
and treatment for special operations forces medical pro- about evacuation category based on initial assessment, a
viders outside the hospital setting. Field based medicine repeat hemoglobin level in 4 to 6 hours with continued
limited to physical exam and occasional point of care decline or inappropriate response to transfusion (1 unit
hematology or chemistry studies requires providers to of red blood cells should raise hemoglobin by 1g/dL)
make treatment and evacuation decisions with limited suggests urgent evacuation is necessary.
information. The following is a suggestion of how a
field based provider may evaluate and manage a patient Last, a medic should consider the health of the unit.
with a TMA syndrome. While TMA syndromes are not contagious, ingestion of
beef, water, or produce contaminated with Shiga toxin–
Initial presentation may consist of only vague symptoms, producing E. coli may lead to an outbreak of HUS. This
including abdominal pain, bloody or watery diarrhea, should be suspected if multiple patients have severe ab-
weakness, and fatigue. Other pertinent history to elicit in- dominal pain and bloody diarrhea with the findings de-
cludes new purpura, easy bruising, mucocutaneous bleed- scribed here. Pathogenic fecal bacterial shedding does
ing, or persistent bleeding from small wounds. Severe or occur, so attention to hygiene and isolation as possible
advanced cases may present with neurologic symptoms of is important to prevent further transmission.

18 Journal of Special Operations Medicine Volume 15, Edition 3/Fall 2016