Page 18 - Journal of Special Operations Medicine - Fall 2017

On arrival at the transplant center, the patient’s initial vital exhaustion with the inclusion of central nervous system (CNS)
signs included temperature of 100.4°F (38.0°C); pulse, 115 involvement (e.g., confusion, altered mental status, uncon-
bpm; blood pressure, 138/72mmHg; respiratory rate, 16/min, sciousness). A core temperature higher than 104°F (40°C) and
and oxygen saturation, 99%. On examination, the patient was absence of sweating have classically been taught as the defining
intubated and sedated. His head and neck examination was criteria between heat exhaustion and heat stroke. Clinically,
notable for a right temporal scar with surrounding ecchymosis, however, the presence of CNS involvement with a documented
dry mucus membranes, and scleral icterus with equal, round, core temperature higher than 104°F (40°C) should be suffi-
and reactive pupils. He also had a central venous catheter in cient to diagnose heat stroke. 4
the right internal jugular vein. Cardiopulmonary examination
revealed tachycardia without other abnormalities. His abdo- The pathophysiology of heat illness affects multiple organ sys-
men was soft, and genitourinary examination demonstrated tems. The cardiovascular system will initially compensate for
the presence of an intraurinary drainage catheter with edema- heat strain by vasodilating peripheral blood vessels, constrict-
tous scrotum bilaterally. Extremities showed 2+ pitting edema ing vasculature to the gut and kidneys, and increasing cardiac
from the feet to the knees bilaterally with normal distal pulses. output by increasing heart rate. Escalating heat strain, how-
An arterial catheter was present in the right wrist and a hemo- ever, will cause continued ischemia to the GI tract, resulting in
dialysis catheter was present in the right groin. The patient’s epithelial membrane permeability and leakage of gut bacteria
GCS score was 5T. He showed no spontaneous eye movement and endotoxins. Hyperthermia is also toxic to a multitude of
and would grimace and withdraw from painful stimuli. tissues, including the brain, kidneys, liver, spleen, and endo-
thelium, resulting in the release of heat shock proteins (HSPs). 5
On admission to the transplant center, his laboratory workup
demonstrated fulminant hepatic failure (total bilirubin, During normal conditions, HSPs help in the synthesis and fold-
17μmol/L; AST, 3,333U/L; and ALT, 5,205U/L), acute kidney ing of proteins. Under stress (e.g., heat, hypoxia, acidosis),
injury (creatinine, 5.5mg/dL), significant pancreatic dysfunc- HSPs stabilize unfolded proteins and help refold proteins dam-
tion (lipase, 3,442U/L), lactic acidosis (lactate, 9.3mmol/L), aged by heat or pH fluctuations, allowing the cell time to re-
thrombocytopenia (platelets, 33 × 10 /L), and coagulopathy pair itself. The combination of endotoxin leak from the gut and
9
(INR, 3.2; PTT, 41 seconds; fibrinogen, 98g/L). Other ab- profound upregulation of HSPs set the machinery of the sys-
normal laboratory findings included significant elevations in temic inflammatory response syndrome (SIRS) of the host into
ferritin (17,088ng/mL) and ammonia (71μmol/L). Hepatitis motion. If left untreated, SIRS will progress to disseminated
serology results were consistent with immunization to hepati- intravascular coagulation, multiorgan failure, and death. 5
tis A virus (HAV) and hepatitis B virus (HBV), without other
evidence of infection (HAV immunoglobulin [Ig] G positive; Prevention of EHI is an integral part of military readiness. In-
hep B surface antibody positive; and hepatitis A IgM/hepatitis dividuals should ensure they are taking steps to mitigate the
B core antibody/hepatitis C antibody all negative). His Model risk of becoming a heat casualty. Individual risk factors for
for End-State Liver Disease score was 43. EHI include poor physical fitness, dehydration, obesity, con-
comitant illness such as respiratory infections, and medications
Hepatology, nephrology, neurosurgery, critical care, and trans- such as diuretics, β blockers, and alcohol consumption. Heat
5
plant surgery consultations were obtained. The patient had a acclimation is the repeated exposure to heat stress to allow the
reasonable chance of recovery of his renal function and was body to adapt to the negative effects of heat stress. There are
not considered a candidate for combined hepatic/renal trans- many guidelines about specific heat-acclimation protocols that
plant. He was listed for emergent liver transplant in an ex- are beyond the scope of this paper. It is generally accepted that
pedited priority because of his critical status. A CT scan and individuals can be acclimatized in 3 weeks. It is important to
6
magnetic resonance imaging of his brain demonstrated no evi- note that exercise should mimic the conditions the person is
dence of cerebral edema, so placement of an intracranial pres- expected to perform, such as equal humidity levels and wear-
sure monitor was deferred. ing necessary equipment and uniforms.

On hospital day 7, a suitable liver became available; the donor Early recognition of EHI is imperative for proper treatment and
was a 41-year-old man who died of a hemorrhagic stroke. The reduction of complications. Symptoms will reflect injury to spe-
patient underwent liver transplantation without complication. cific organ systems affected by hyperthermia. Chest pain, short-
He was extubated and transitioned to intermittent hemodi- ness of breath, and fatigue will occur due to increased cardiac
alysis on hospital day 9. He was transferred out of the inten- demand. Nausea and vomiting are secondary to decreased gut
sive care unit on hospital day 12. A tunneled central venous perfusion due to splanchnic vasoconstriction. Decreased perfu-
catheter for hemodialysis was placed. On hospital day 20, the sion of organs and muscles due to dehydration and shunting of
patient began to make urine, his encephalopathy had resolved, blood results in elevated lactate levels and a metabolic acidosis.
and he was able to ambulate 50 yards with assistance from The body responds to this acidemia with increasing respiratory
therapists and nurses. He was transferred to a rehabilitation rate, which further exacerbates metabolic demand. CNS depres-
facility to continue his recovery. sion is a result of worsening acidemia, giving the symptoms of
delirium, ataxia, erratic behavior, and unconsciousness.
Discussion
Prompt cooling is the single most important initial treatment of
Exertional heat illness (EHI) is a continuum of disease. Mi- EHI and should be initiated as soon as possible. The resources
7
nor heat injuries include heat cramps and heat syncope. Heat available may constrain how this is performed. Immediate ac-
exhaustion is characterized by elevated core temperature and tions include moving the patient to a cooler environment or
inability to continue exercise. Heat stroke is the most se- into shade and removing equipment and clothing. Ice-water
3
vere aspect of EHI and clinical diagnosis is the same as heat immersion has been shown to be the most effective cooling
16 | JSOM Volume 17, Edition 3/Fall 2017