Page 77 - Journal of Special Operations Medicine - Summer 2015

severe by limiting the supply of food. The intensity of as acute renal failure or hyperkalemia but can also be
the exercise and additional induced deprivations con- asymptomatic. 16,17 One problem is that severe physical
siderably exceeded those of routine military duty. This exertion often leads to a systemic rise in CK levels as a
means that the physical disorders listed can be expected correlate of muscle damage. 1,18–21 The level above which
to be less frequent and severe in shorter and less intense this leads to serious complications and must be treated
military endurance exercises. cannot, however, be clearly defined. 16,17 It is emphasized
in studies that neither the presence nor the extent of el-
Hyponatremia evated CK levels in cases of exertion-induced rhabdo-
The hyponatremia incidence of 5.9% in this study was myolysis allows any predictions to be made with regard
low, on the whole, and the condition was not very pro- to acute renal failure. Clarkson et al. did not find any
1
18
nounced in terms of intensity. No statistical difference evidence of renal disorders in healthy young volunteers
could be found between Finishers and Nonfinishers. with exertion-induced rhabdomyolysis and CK levels of
Electrolyte imbalance in the form of exercise-induced sometimes more than 10,000U/L. In most clinical case
hyponatremia, therefore, was not a reason for anyone reports on complicated rhabdomyolysis, CK levels con-
participating in the exercise to drop out. sist of five figures. 1,16,17 Some authors also recommend
that patients who solely have CK levels up to 15,000U/L
The incidence we detected in our study was lower than and no other risk factors be treated as outpatients un-
the incidence in comparable, extreme long-term endur- der close supervision. This all implies that a marked
22
ance exercises (e.g., Ironman) and mass events such as elevation of CK levels alone need not be considered an
marathons, which show incidences of 13% to 30% illness requiring treatment, but rather a normal corre-
for hyponatremia. 7,8,12,13 It seems that among the par- late of extreme physical exertion. None of our soldiers
ticipants in this exercise, consuming pure water with suffered from hyperkalemia or continuous oliguria, so
a sodium concentration of approximately 20mmol/L we can assume that any rhabdomyolysis did not involve
14
did not increase the risk of developing hyponatremia. complications and rhabdomyolysis has not been listed
Therefore, our data imply that no special electrolyte as a reason for dropping out. However, it must be em-
drinks are necessary to prevent exertional hyponatre- phasized that medical personnel must always be aware
mia. This finding is supported by Almond et al., who of the complications that may develop both in the Fin-
8
did not find any correlation between hyponatremia and isher group (higher average CK concentration) and the
the type of liquid consumed , whereas there is evidence Nonfinisher group (higher maximum levels).
8
that sodium-free liquids increase the risk of hyponatre-
mia. In view of the fact that common sports drinks Extreme CK elevations have also been observed dur-
15
have an average sodium concentration of 18mmol/L, ing civilian events involving extreme physical exertion.
which is less than one-fifth of the normal physiologic Examples are average levels of more than 15,000U/L
sodium concentration, it seems that the sodium concen- during a 24-hour race and almost 40,000U/L in 20%
tration of the consumed liquid is of considerably less of a random group of participants during a race of
importance than commonly assumed. What is relevant 161km. 1,21 However, even during mass sporting events
7,8
is the amount of liquid consumed, since most authors such as marathons, considerable CK elevations with
consider water intoxication to cause hyponatremia. mean levels of 2,470U/L are frequently detected the day
6–8
This means that the condition may develop at any time, after the event, which means that the levels detected in
23
especially in soldiers who drink at predefined intervals our groups need not be considered excessive.
and not when they are thirsty. 8
Systemic Physical Exertion
Muscle Damage A comparison of the two groups showed that the Finish-
Significantly elevated CK, ALT, and AST levels were ers had significantly elevated CRP levels and a signifi-
detected in both groups as evidence of muscle tissue cant loss of body weight, whereas the Nonfinishers had
damage, with ALT and AST levels significantly higher a significantly elevated leukocyte count (Table 2).
among the Finishers and average CK concentration only
slightly elevated. The longer average period of exertion Exertion-induced systemic reaction or fatigue is difficult
can account for this. Liver damage could be ruled out as to represent in objective measurements. However, in ad-
a cause for the release of ALT and AST, as the soldiers dition to the CK elevation discussed, which correlates
had normal GGT levels. with the distance covered by the soldiers, loss of body
21
weight and the systemic inflammatory response set off
In cases of acute necrosis of muscle cells (rhabdomyoly- by exertion-induced cell damage 20,21 can be used to as-
sis), the CK level is the most sensitive marker for deter- sess overall physical exertion. The elevated CRP levels
19
mining the extent of tissue breakdown. This condition and the greater loss of body weight among the soldiers
can have potentially life-threatening complications such who finished the exercise can be accounted for by their

Medical Conditions in German SOF Selection 67