BASIC MEDICAL CARE - Medicine for Mountaineering and Other Wilderness Activities - page 11

Convalescence
Although physical activity should be encouraged during convalescence, strenuous ex-
ercise undertaken too early may delay recovery, particularly at high altitudes. In addition,
individuals are more susceptible to other injuries during convalescence. To be certain that
recovery is complete, delaying a return to full activity for two or three extra days may be
desirable.
FLUID BALANCE
Anadequatefluidintakeisessential.Apersoncanliveforweekswithoutfoodbutonlyfor
a few days without water. Fluid balance implies equilibrium between losses (through the
kidneys, skin, and lungs—or other routes) and gains (from fluids and foods that have been
ingested). During an illness that increases fluid losses and makes fluid intake difficult or
impossible, fluid balance can become critical. As an example, dehydration from massive
diarrheal fluid loss kills two to three million children annually in developing countries.
Anadultofaveragesizenormallyloses1500mlto2000mlofwaterfromthebodyeach
day. The “sensible loss” excreted by the kidneys ranges from 1 to 2 liters per day. The “in-
sensible loss” through perspiration (even in cold climates) and evaporation from the lungs
(to moisten air that is inhaled) is 0.5 to 1 liter per day in temperate climates and at low alti-
tudes. In hot climates or during high fever, several liters of water may be lost daily through
perspiration (which is no longer insensible). At high altitudes up to 4 liters of water can be
lost through the lungs each day.
Salt (sodium chloride), potassium, and bicarbonate, known collectively as electrolytes,
arevital constituents ofbodyfluids.Aswithwater,abalance between intake andlossmust
be maintained. The daily salt requirement for an average adult is 3 grams. When large
amounts of salt are lost through perspiration, needs may be considerably higher.
Normally functioning kidneys are very sensitive to changes in the body's fluid balance
and react immediately to conserve or eliminate water. The urine volume and color are
highlyreliable indicatorsoffluidstatus.Atwenty-fourhourvolumeoflessthan500ml,or
urine that has a deep yellow or orange color, is indicative of fluid depletion; a volume of
2000 ml of very lightly colored urine is typical of a high fluid intake.
These water and electrolyte requirements represent the needs of a healthy adult. Indi-
viduals with heart or kidney disease may be unable to get rid of excess salt and water and
can have quite different requirements. The administration of normal quantities of electro-
lytes and water (particularly salt) to persons with one of these disorders may have serious
consequences.
Whenanillness,suchasdysenteryorcholera,causeshighfluidlossesthroughvomiting
and watery stools, the volume of fluid lost should be estimated to keep current on the per-
son's fluid status. Insensible losses must be estimated also, taking into consideration fever,
environmental temperature, and altitude. The volume of fluid ingested must be recorded to