Chapter 27 - Fluid. Electrolyte and pH Balance
(figures relate to Tortora/Grabowski 9th
edition of Principles of Anatomy and Physiology)
1/3 of all body fluid is ECF (major ions present are Na+ and
Cl-)
2/3 of all body fluid is ICF (major ions present are K+ and
HPO42-)
80% of the ECF is interstitial fluid,
20% is plasma
We gain water, daily, via: (#l) ingested (moist) foods and liquids,
(#2) metabolic reactions
We lose water, daily, via: GI tract,
urinary tract, lungs, skin
Figs: 27.3 and 27.4 summarize the regulatory pathways we discussed in Ch. 26
Enemas can cause electrolyte imbalances (and even death) if a fluid is
used which is too hypotonic or hypertonic to our body fluids.
Edema is caused by retention of Na+ and therefore, H2O
- due to renal failure and/or too much aldosterone secretion.
People at risk for electrolyte
imbalances: those that can't communicate thirst impulses, severe trauma/burn
patients (pts), elderly, infants, hospitalized pts., people receiving IV's,
catheters or diuretics, people experiencing excessive fluid loss or requiring lots of
fluids.
Blood Imbalances:
1 - hypernatremia -
high sodium: due to high salt diet, hypertonic IV, water deprivation
or dehydration
Symptoms: edema due to water
moving into ECF from cells, this also causes excessive thirst, hypertension,
convulsions
2 - hyperkalemia - high potassium: due to high intake, low
aldosterone (low Na reabs.)
Symptoms: nausea, vomiting,
diarrhea, ventricular fibrillation (may cause death)*, metabolic acidosis
3 - hypokalemia - low
potassium: excessive vomiting/diarrhea, high aldosterone, diuretics
Symptoms: muscle fatigue, mental confusion,
increased urine output, shallow respirations, changes in EGG
4 - hypercalcemia
- high calcium: due to hyperparathyroidism or high Vit. D intake
Symptoms: nausea,
vomiting, anorexia, itching, depression
5 - hypocalcemia — low calcium: due to
hypoparathyroidism or increased Ca loss
symptoms: muscle
cramps, tetany, bone fractures, convulsions, spasms
Metabolic Acidosis (plasma HCO3-
reduced 50% and pH drops below 7.35)
Due to: NH4Cl
ingestion, diabetic ketosis, loss of bicarbonate from diarrhea
Compensation:
1 - Increase
respiration (hyperventilation) leads to increase CO2 loss, which
leads to decrease
carbonic acid and H+
2
- Kidney increase H+ excretion (returns 1 HCO3-,
a base, to plasma)
3
- Ammonia and phosphate buffers H+ in
collecting duct
Metabolic Alkalosis (plasma HCO3- increased and pH
rises above 7.45)
Due to: Prolonged
vomiting, overuse of diuretics (loss of H+)
Compensation:
1
- Decrease respiration (hypoventilation) leads to
increase Pco2 plasma, which leads to
increased carbonic acid and H+ in plasma
2
– Kidney increase HCO3- excretion (a base)
Respiratory Acidosis (increase PCO2 plasma and pH drops below 7.35)
Due to: Hypoventilation due to emphysema or
airway obstructions
Compensation:
1
- The increased PCO2 in plasma causes all
cells to become more acidic (higher H+)
2
- Kidney increase H+ excretion (returns 1 HCO3-,
a base, to plasma)