ROBERT SCHOENE: I would like to bring out a point that COL Schumacher made with respect to making the troops or expedition members more aware, so they know what to expect. Education about the cold has been pretty well emphasized, but I would like to make a plea for better education about high-altitude operations.
When the troops are operating in the Sierras at 7,000 to 8,000 ft (2,134–2,439 m), the problems are not generally serious. They are acclimatized and are probably at full physical capacity at that point. However, when they get higher than 8,000 ft (2,439 m), the omnipresent hypoxia exerts a subtle, mysterious effect on people, their energy, and their psychological energy. I think the troops need to know about altitude illness and what to expect when they get some of those symptoms, so they do not think they are dying. They also need to know that they will need to make extra efforts to overcome the lack of spontaneity and vigor that is inevitable at 11,000 to 14,000 ft (3,354–4,268 m).
I say this from personal experience and from my own sense of what happens. When collecting data at 20,000 ft (6,098 m), I really had to make an effort. At Denali, at 14,000 ft (4,268 m) for months, I had to make an effort. The troops must know about these effects. Perhaps there should be a more
complete educational system with respect to altitude. As is often said, the commanders know this, but the troops also need to know what to expect.
MURRAY HAMLET: Physiologically, the first change that occurs is physiological vasoconstriction, resulting from both cold and high altitude. Many studies define the impact of altitude on cold injury, and clearly physiological vasoconstriction has an impact. It is essentially a mediated constrictor response. We understand a little bit about how it works.
Decreased thirst also seems to be common to both cold and high altitude. But there is a concomitant increased water requirement for some reason. Therefore, not only are you not drinking as much as you need, you need more. These two things may be synergistic in cold and high altitude.
Regarding fatigue, clearly people become more tired in cold and altitude than they would under other conditions. There is also probably an increased caloric requirement in cold and high altitude.
Therefore peripheral constriction and its relation to the ability to perform certain tasks—to do things with one's hands, for example—affects a mission. Other examples of impaired tasks are preparing food and taking one's clothes on and off.
ROBERT NESHEIM: Is there any evidence that the fatigue you are talking about can be overcome if people take in an adequate amount of calories? Is that fatigue a result of inadequate caloric intake, or is there some other physiological activity going on?
RUSSELL SCHUMACHER: Anecdotally, I would say no. I think they are getting all the calories they need. I do not think anyone suffers in that regard below 12,000 ft (3,659 m). But fatigue over time drags you down. The physical nature of the cold in conjunction with the altitude is the cause.
ROBERT SCHOENE: Sleep is a problem. I think the problem of sleep needs to be addressed, particularly above 10,000 ft (3,049 m). Periodic breathing and all the things that take place that alter the sleep patterns might be very important factors.
A. J. DINMORE: The big problem at high altitude is the fatigue upon exertion. You perception of what can be done is actually much greater than what you are physically able to do. As soon as you try to do something, you immediately hit this fatigue barrier. I think over the long term, that is very worrying.
MURRAY HAMLET: It is both a physical and mental fatigue. It is a combination of ''I know I have got to do this," "I might be able to drive myself to do it," but psychologically "I do not think I want to bother."
Regarding meal preparation, ease of preparing meals is absolutely critical in cold and high altitude. If it is difficult to prepare, you are not going to do it. If it is too hard to fix, you go to bed.
A. J. DINMORE: There is a conflicting requirement here. When you go to altitude, you want to carry a very light-weight ration. When you are climbing and going on a long-range mission, carrying everything on your back, that is significantly different from a mission in cold, when the location is more static and there is more logistical backup. The conflicting requirement is between ease of preparation and trying to get light-weight rations that can be carried in the field.
NICOLE HOTSON: Has anybody ever tested how your taste is affected by high altitude?
ROBERT REYNOLDS: Yes, I think there have been a number of anecdotal studies. One study that we will be going over next month is from Mount Everest, where they are looking at changes in perception and threshold of taste as a function of altitude. Those of us who have been at high altitude know that taste perception goes down. To overcome this we added more spices. McCormick Spice was one of our sponsors, and they gave us 5 lb (2.3 kg) of cayenne pepper. It was gone within a matter of weeks.
Colonel, you mentioned flavoring agents, such as garlic, pepper, and the more subtly flavored things that will make the food more palatable, acceptable, or desirable at altitude.
ELDON W. ASKEW: Certainly taste at altitude goes out the window if you are taking Diamox (acetazolamide, a cerebral vasodilator), at least in my experience.
ROBERT NESHEIM: What I am hearing here is a common need to push water at both high altitude and cold, and when you are at altitude usually you are also experiencing cold. There is a common need to push calories in those areas, but you are not likely to overcome the difficulties of caloric intake by pushing them.
GAIL BUTTERFIELD: In the exercise community, it is pretty well accepted that you can maintain the thirst mechanism in an individual who has lost a significant amount of water as a result of heavy exercise by replacing the fluid with a fluid and electrolyte potion rather than plain water. I wonder if anybody has ever tried that to maintain a better thirst mechanism.
ALLISON YATES: Do you mean that the voluntary consumption is higher with a beverage replacement that has electrolytes?
GAIL BUTTERFIELD: Yes.
ROBERT NESHEIM: I was thinking of it not so much as a response to the thirst mechanism, but that maybe people are voluntarily willing to take in more.
GAIL BUTTERFIELD: If you take in plain water, you dilute the electrolytes that are present in the body. Therefore, you turn off the thirst mechanism more quickly than if you replace with water and electrolytes, because the electrolytes then add to the electrolytes in the body and keep the osmolarity slightly higher and promote the thirst mechanism longer.
I. SIMON-SCHNASS: I have some anecdotal data. I had some friends who were convinced they had to take electrolytes. They forced themselves to drink up to 4 liters of electrolyte-containing sport drinks at high altitude. They became sick because they lost most of the fluid by the lung (through respiration), which is distilled water. They did not sweat a lot, so they were actually overdosing. They were convinced it was good for them, even though they felt sick. I think you need to teach people what kind of fluid loss is taking place, whether it is vapor from the lungs or sweating. Then they can decide for themselves what they need to replace.
RUSSELL SCHUMACHER: I would like to address the comment on pushing food and water. The converse is that at altitude and in the cold, the failure to do so is catastrophic. The failure at sea level and with exertion does not even compare. Not just individuals are lost, but whole units, companies, and platoons. That is what is really scary about the fluid scenario from my personal experience.
ROBERT REYNOLDS: With respect to the electrolytes, I would like to suggest caution in pushing them. On our On Top Everest '89 expedition, we took zero salt. Where possible, we had a low-salt alternative for a number of the freeze-dried or the retort-pouched entrees. The first 2 weeks, there were great objections to the taste, but after 2 weeks, they were totally acceptable. People went for the spices, and I think we had lower fluid retention as a result. The acceptability of the food went up because of the additional spices.
WILLIAM BEISEL: The matter of salt and water balance is not clear to me. We heard stories about why we need to push fluid intake, as well as stories about edema and fluid in the wrong places as a major cause of catastrophe. I wonder if the committee could address this paradox in more depth?
A. J. DINMORE: From the mountaineer's point of view, the question is one of acclimatization and then chronic altitude state. During the acclimatization
phase, normally there is diuresis, which is beneficial to the body in getting to high altitude. However, in any prolonged stay at high altitude, you must have that immediate increase in water intake.
MURRAY HAMLET: The endothelial cells are incapable of holding water in the vascular space. When they drop below 30 in an acid medium—in hypothermia, for example—the sodium pump dies, so they do not hold fluid in the vascular space. Thus one of the problems in resuscitation and one of the things killing hypothermics today is trying to raise their central venous pressures too fast and too early in resuscitation, resulting in fluid leaking out. Until they are warmed up to the point where those sodium pumps and endothelial cells start, they are unable to hold fluid.
Something is wrong with the endothelial cells' ability to do that at altitude. So when you are thinking about where the fluid is, you have to think about where it is going next and what kind of damage it is going to cause. Recall the pitting edema that we saw. Many people get a small amount in their hands or their feet, and I think I have seen it more in women than in men. The edema is transient; it lasts a day or two and then goes away. It is related to endothelial cell function somewhere in the extremities, but it is not clear what is wrong with them, why, and what we can do about it.
We do not know what to do about it in resuscitation, other than warming them up.
ROBERT SCHOENE: I think Bill's point is a very good one. You hear us say, push fluids with increasing altitude, and you heard me say this morning that all the pathological effects are due to fluid in the wrong place. I think Murray is right that the endothelium is the culprit.
In my view, if we can maintain optimal intervascular volume, optimal cardiac output, and optimal oxygen delivery in a hypoxic situation, we will minimize whatever the effect of hypoxia is on making the endothelium leak. It happens in the intensive care unit all the time. Endotoxins may play a role, but there is something about hypoxia that triggers permeability in the vascular endothelium. So if we can optimize oxygen delivery and minimize hypoxia during acclimatization, then I think we will minimize altitude dysfunction.
Once it is leaking, I do not know what the solution is. The point is, you do not want to volume deplete people at altitude.
ALLEN CYMERMAN: I wanted to talk about sleep at altitude. I think once you get over the illness stage and you still have the troops in a high-altitude situation, sleep is paramount. Sleep disturbances continue for a long period of time after that. If the committee could come up with something like a hot glass of milk as a solution, it would be perfect. In that sense, if Harris has done something with serotonin or any of the serotonin analogs, where there are no
aftereffects on both mental and physical performance the next day, I think we would go a long way toward helping the soldier at high altitude.
WILLIAM BEISEL: I worked on the original studies in the late 1950s that solved the problems with fluid electrolytes and cholera, so fluid and electrolytes have been in my field for a long time. You are saying we have to worry about something that does not follow the rules, like capillary leak problems. If we are going to anticipate capillary leak problems, perhaps we should be thinking about it during indoctrination and training, at least for a certain period of time, to anticipate it and protect our troops in some way. I do not see this in any of the written guidelines. Do we need a new set of guidelines that anticipate the problems of cerebral edema and other conditions that can be life threatening?
MURRAY HAMLET: There is not enough predictability in those conditions to be able to warn anybody ahead of time. However, there are certain people who are going to get cerebral edema, and others who are going to get pulmonary edema. We know there is some past history that would affect their susceptibility. But I do not think there is a general statement we can make that is a prognosticator of edema in the extremities, or cerebral edema, for example, other than prior exposure or prior injury. It would be nice if there were; it would solve a lot of our problems.
We have looked at cold-induced dilation of the extremities to see if that might be a predictor of people who get sick at altitude. We did not pursue it, but we wondered if someone whose peripheral sympathetic system really constricts badly at high altitude or at moderate altitude may be the one who is going to get sick first.
WILLIAM BEISEL: Is acute mountain sickness or acute edema strictly a phenomenon of the first few days, or can it occur any time?
ROBERT SCHOENE: Any time. Most commonly it occurs in the first 6 to 40 hours, but I have seen it occur after a couple of weeks at high altitude.
ALLEN CYMERMAN: Change in altitude is what does you in with cerebral edema and pulmonary edema, but they are probably not the same.
WILLIAM BEISEL: These are life- threatening conditions. My first thought as a physician is, take care of the life-threatening things, and the other things can be solved later.
ROBERT SCHOENE: It can occur at any time. That is why I emphasized this morning that education and knowledge where HAPE (high-altitude pulmonary edema) can occur will prevent any fatalities.
WILLIAM BEISEL: Part of the training of the soldiers and leaders should be the recognition of the early symptoms. We must prepare the leadership and the soldiers to pick it up in each other—a buddy system kind of management.
RUSSELL SCHUMACHER: In the Marine Corps, it is.
MURRAY HAMLET: Fortunately we have a quick treatment in place, so there is a built-in process. But the one that scares me is when people who develop pulmonary edema go down, recover, and then climb again. I grip my chest on that one. I would not want to be the doctor on that trip. That is scary.
JOHN VANDERVEEN: Is there enough training for physicians in this area? Do the military programs and other programs cover this well?
RUSSELL SCHUMACHER: The Navy does. The Navy has a cold-weather medicine program that covers the subject in total. They do it at my base.
JOHN VANDERVEEN: Is it your experience in dealing with physicians in this area that they are knowledgeable enough in how to treat acute cases?
ROBERT SCHOENE: In general, no. Two years ago when I was in Colorado, helping to run the Colorado Altitude Research Institute, many of the physicians at high altitude were not good with altitude illnesses, let alone the doctors who would call from low altitudes and ask whether their patient with a particular condition could tolerate high altitude. I think the education is very thin.
JOHN VANDERVEEN: Specialization might be an area that we could consider suggesting as a follow-on.
DAVID SCHNAKENBERG: Two years ago when the Ration, Cold Weather (RCW) was developed, the Army Surgeon General was asked for recommendations on nutritional composition. We went to the committee for advice. We were advised that for a cold-weather ration for use by troops during operations, we should minimize the sodium and protein contents (compared to the Meal, Ready-to-Eat) because it would reduce somewhat the obligatory water requirements of the soldiers in an environment where liquid water could be scarce. Thus the Ration, Cold Weather was designed so that even if you eat the 4,500 kcal, there are only about 4,500 mg of sodium, that is, 1 mg of sodium per calorie. It contains approximately 90 g of protein in those 4,500 kcal, which is considerably less than the MRE, which would be over 150.
Based on what we have heard today and during this meeting, are those levels still appropriate for a cold-weather operation? Is that ration appropriate for the first few days of an altitude operation, relative to the electrolytes question that was asked, so that the troops must drink water along with it?
Should we have less sodium the first few days, or should we have a carbohydrate-electrolyte supplement during the first few days of altitude operation to address the issue of trying to maintain the body's hydration in the appropriate compartments?
That is a complicated question, but I think it is a practical one that comes back to the Surgeon General giving advice to Irv Taub and his colleagues in putting together this ration.
MURRAY HAMLET: You lose palatability quickly.
ROBERT NESHEIM: Is there any risk of hyponatremia with the RCW? Anecdotally, I think I heard somebody report that.
ELDON W. ASKEW: I have a letter from a member of the Special Forces—a medic—who had been on a climb in Alaska. He had been working hard, sweating quite a bit, even though it was a cold-weather climb. Several members of the team had become exhausted, and in his opinion, they were salt depleted. He had to start intravenous salines to bring them around. He stated that there ought to be more sodium in the Ration, Cold-Weather.
This is the one dissenting opinion we have had so far. Nevertheless, if he is correct, it is significant. I think maybe he had exhaustion, glycogen depletion, and dehydration more than sodium depletion, but I would be interested in hearing a comment on this.
ELSWORTH BUSKIRK: I think David has raised the issue of timing. Because the troops are going in under conditions where early on they will be sweating heavily, they do need some sodium under many circumstances. But I do not think they need as much sodium as some of these rations contain.
HARRIS LIEBERMAN: I would like to comment on behavioral problems and what can be done about them. Someone brought up the issue of sleep. Clinically, there are medicines that help people sleep. You can get a prescription from your physician, take a benzodiazepine, and you will sleep better at high altitude. The question is, can you perform adequately the next day? There is a complicated answer to that question. It depends on the half-life of the benzodiazepine prescribed, the dose taken, and the person's sensitivity to the drug.
There are also a series of other drugs that are less potent than benzodiazepines, will not help your sleep as much, but clearly do not have the next-day aftereffects. For example, antihistamines are reasonably potent sedatives. In fact, one can buy a lot of over-the-counter sleep aids, which are nothing but antihistamines, and they work to a certain degree. In that same potency range, between antihistamines and benzodiazepines is a hormone, melatonin, which seems to have clear sleep-promoting effects at very low doses, and which does
not seem to have the next-day aftereffects. It is in the process of being developed by a number of drug companies and will probably be available in the next few years.
Then the final issue and maybe the one that is most interesting here—the nutrient and amino acid, tryptophan. We had to stop working on tryptophan when contaminated tryptophan was being sold by one company. We need to consider whether people are interested in having some kind of nutrient that will help them sleep.
Tryptophan does not have aftereffects. It is not nearly as potent as benzodiazepines and not as potent as melatonin, but it is a nutrient.
Finally, I want to comment on the converse: The issue of being too tired during the day. Part of that fatigue is probably attributable to poor sleep—the interrupted sleep that produces next-day fatigue. However, I believe that there is a malaise syndrome present at high altitude, and the way to deal with that is probably not nutritionally. I think you could treat maybe 20 or 30 percent of the problem with proper use of caffeine during the day. Timing the caffeine consumption is important to avoid interfering with sleep. But it is a viable option for increasing mental performance during the day at altitude.
PARTICIPANT: How much tryptophan do you have people take?
HARRIS LIEBERMAN: We have given people 50 mg/kg.
ROBERT SCHOENE: Regarding the sleep issue, 10 years ago, Dalmane was being used, which did have prolonged effects and did give people a hangover the next day. That happened on Mount Everest. Someone almost fell off the south face because he was very ataxic.
A couple of other considerations. You want to make sure that whatever you give, it is not a respiratory depressant. Some of the benzodiazepines in larger doses are respiratory depressants, and you want to avoid that. Halcyon has been used in low doses. It is probably short-acting enough that there will not be a next-day aftereffect, and it does not suppress ventilation.
One of the things that will interrupt sleep is periodic breathing. In a very low dose, Diamox or acetazolamide is recommended for sleep, not because it is a sedative, but because it stops periodic breathing and allows people to sleep comfortably through the night.
RUSSELL SCHUMACHER: No commander in his right mind is going to give his front-line troops any kind of sleep inducer. If you have that kind of problem, you will pull your forces off that line and replace them. At high altitude, you are using special operation-type forces, and in those cases, maybe you would do that. But whether you are in the United States or Bosnia, Iran, Turkey—places in the world where there might be problems with high altitude
but the altitudes still are not high enough to produce the level of sleep loss that could necessitate sleep inducers.
ROBERT NESHEIM: Your point is well taken. Most of the altitudes we are dealing with are in the more moderate ranges.
ROBERT POZOS: Some of us are caught up in the euphoria of some of these nutrients. I want to caution the entire group about glycerol. This idea of hydration and glycerol is a very debatable issue. Whether it promotes some kind of intracellular or extracellular movement of fluids and enhances performance is extremely debatable. What always bothers me is that some of these notions get into the folklore very fast and then are implemented with disastrous consequences.
Regarding the issue of salt and hydration, millions of corporate dollars have been spent looking at this specific issue. Yet there is no clear answer to it. The question you raise is excellent, but we do not have a scientific basis for electrolyte drinks and their effectiveness in these kinds of unique environments. I think we must be very cautious. We do not want COL Schumacher's successor coming down on us later because we made recommendations that were not solidly based on scientific fact.
A. J. DINMORE: I have a specific question for Dr. Taub about fluid intake and working in cold environments. As pointed out earlier, you normally melt your water in the morning. You make your food and then you fill up a hot flask, which you carry with you during the day so you can drink from it. I was surprised that your Ration, Cold Weather doesn't have any liter-sized beverages in it. How are soldiers able to make and carry a liter of fluid when they only have a few fluid ounces of drink mix in the ration?
ROBERT NESHEIM: Colonel, I think you commented on that. You indicated that you do not encourage people to melt snow or ice.
RUSSELL SCHUMACHER: No, snow or ice is not a problem. We do encourage that. But they must make sure it boils. All our forces have vacuum flasks in their kits.
A. J. DINMORE: That is the point I am making. They use a vacuum flask, which is 1 liter in size, and they heat water from whichever source in the morning to make this hot drink. But they do not actually have a liter of hot drink mix in their cold-weather rations. It comes in much smaller cup sizes.
RUSSELL SCHUMACHER: That is a good point.
GAIL BUTTERFIELD: Until we adequately nourish people and see what the differential effect of high altitude is, we will not know what is going to happen with salt and fluid. With adequate nourishment, we may eliminate some of the problems we have been talking about. That is a lot simpler then making a potion that has something artificial in it, such as glycerol or a high-caffeine drink that puts people on a jag.
ROBERT NESHEIM: What you are saying is get the calories into them that are more correspondent to their expenditure.
GAIL BUTTERFIELD: And then see what falls out as being additional needs. Until the basic needs are met, I think we are shooting around.
HARRIS LIEBERMAN: I do not agree with that. When we deprive people of food under normal conditions, we have to make them severely calorie deficient for long periods of time before we see any performance decrements. So a couple of days of inadequate nutrition are simply not going to have any effects on mental performance, although it may on physical performance. As far as mental performance is concerned, if you want 100 percent performance, you have to consider that you may not get it simply with adequate nutrition.
JOËL GRINKER: If you have knowledgeable subjects as opposed to naive subjects, are they aware of these performance effects?
HARRIS LIEBERMAN: Which effects, Joël?
JOËL GRINKER: In terms of their being able to show less of a decrement in performance. Are they able to verbalize that?
HARRIS LIEBERMAN: That is a good question. The question is, if you produce performance improvements by giving people things, can you ask them if they have improved performance? Can they detect it themselves? The answer is, it depends how potent the substance is that you give them.
In general, the kind of improvements we get with nutrients are of a magnitude where it is difficult to detect the improvement, with the possible exception of caffeine. I am talking about mental performance.
ROBERT NESHEIM: We have a real challenge as a committee now to sort through all of this excellent information, largely physiological in nature, and then translate it into nutritionally-related recommendations as applied to cold weather and high altitude.
|This page in the original is blank.|