Page 65 - Journal of Special Operations Medicine - Winter 2014

Table 1 Summary of Selected Dexamethasone High-Altitude Research Studies
Subject
Author Description Subjects Dexamethasone Dosage Key Results
Ellsworth Healthy Dexamethasone (n = 10) 4mg every 8 h beginning Dexamethasone decreased the
et al., 1991 23 climbers Acetazolamide (n = 10) 24 h prior to climb until occurrence of AMS and severity of
Control (n = 9) descent symptoms (p = .025).
Maggiorini Adults prone Dexamethasone (n = 10) 8mg twice daily starting Dexamethasone reduced the risk of
20
et al., 2006 to HAPE Tadalafil (n = 10) the day before the ascent developing HAPE (p < .001) and
Control (n = 9) to 4559m throughout the reduced the occurrence of AMS
2-day study (p = 0.02).
Levine et al. Healthy adults Dexamethasone (n = 5) 4mg every 6 h during Dexamethasone decreased the
24
1989 Control (n = 5) a chamber flight to occurrence of AMS and severity of
12,100 ft symptoms (p = 0.005).
Fischler et al., Adults prone Dexamethasone (n = 8) 8mg twice daily starting Dexamethasone improved
25
2009 to HAPE Tadalafil (n = 7) the day before the ascent Vo -max (p < .05) and oxygen
2
Control (n = 8) to 4559m throughout the kinetics (p < .05) and reduced
2-day study ventilator equivalent for CO 2
(p < .01); no significant difference in
peak O saturation between groups.
2
Siebenmann Adults prone Dexamethasone (n = 10) 8mg twice daily starting Dexamethasone improved
et al., 2011 to HAPE Control (n = 14) the day before the ascent Vo -max (p = .025); no significant
26
2
to 4559m difference existed in arterial O
2
saturation during maximal exercise.
LeFleur et al., Adults prone Dexamethasone (n = 6) 4mg given twice each Dexamethasone decreased the
2003 to HAPE prior to ascent of 4800m cognitive deficits in participants
22
who were pretreated.
However, researchers discovered that subjects’ ability to saturation levels at maximal exercise. Also, treatments
perform certain tasks after acute exposure to high alti- prior to hypoxic exposure reduced pulmonary arterial re-
tude improved after pretreatment with dexamethasone. sistance and increased alveolar fluid clearance. 26
These researchers also determined that acute exposure
25
to high altitude, in even asymptomatic subjects, resulted Fischler and colleagues conducted a study on 29 moun-
in small cognitive deficits that could be reversed with taineers with a history of HAPE. Subjects were random-
dexamethasone treatment. It is generally accepted in the ized to tadalafil 10mg twice daily, dexamethasone 8mg
scientific literature that dexamethasone can reduce the twice daily, or placebo a day before ascent to 14,000 feet.
abnormal leakiness of the blood–brain barrier, thereby Baseline maximal oxygen uptake measurements were
resulting in improved cognition. 22 performed at low and high altitudes (14,000 feet). Dexa-
methasone increased maximal aerobic capacity com-
pared with placebo. Pulse oximeter oxygen saturation
Effects of Dexamethasone on Cognitive and at rest was significantly lower with both dexametha-
Physical Performance at Altitude
sone and tadalafil compared to placebo (both p < .05).
Past studies suggest dexamethasone may be useful in im- However, heart rate significantly increased in all groups
proving maximal aerobic capacity of special operators but was substantially lower in the dexamethasone
susceptible to HAPE. For example, Siebenmann and col- group compared to the other study groups (p < .01 vs.
26
leagues found improvements in maximal aerobic exer- placebo and tadalafil). There were no statistically sig-
cise in HAPE-susceptible subjects at 14,000 feet. In their nificant differences in AMS scores between the three
study, maximal aerobic capacity was evaluated on a cycle groups on day 1. However, there was a statistically sig-
ergometer at an altitude of 1600 feet and 24 hours after nificant difference in the dexamethasone group on day
rapid ascent to 14,000 feet. Subjects were divided into a 2 (p < .01). Dexamethasone improved maximal aerobic
control group (n = 14) and a dexamethasone group (n capacity and oxygen uptake kinetics while also reduc-
= 10). The control group performed both tests without ing hypoxia-induced pulmonary hypertension in HAPE-
dexamethasone. The dexamethasone group received 8mg susceptible subjects at 14,000 feet. Conversely, tadalafil
twice a day starting 24 hours prior to ascent. Researchers did not significantly improve maximal aerobic exercise
showed that dexamethasone prophylaxis increased maxi- capacity. Tadalafil also showed a limited ability to re-
mal aerobic capacity of HAPE-susceptible subjects after duce hypoxia-induced pulmonary hypertension. The pos-
the first night at 14,000 feet without affecting oxygen sible mechanisms contributing to an improved exercise

Dexamethasone for Prevention and Treatment of High-Altitude Illness 55