Fluids/ Questions and case studies

Questions

1. What is the proportion (in % of whole body weight) of intracellular fluid on average in a healthy adult?
2. • A – 60
   • B – 40
   • C – 25
   • D – 15
3. The physiological range of plasma osmolality is 275-295 mmol/kg. At what value of osmolality does antidiuretic hormone begin to be secreted?
   • A – 295 mmol/kg
   • B – 300 mmol/kg
   • C – 278 mmol/kg
   • D – 270 mmol/kg
4. Which statements are incorrect?
5. • A - Plasma Na⁺ concentration is not a measure of the body's Na⁺ content
   • B - The level of plasma Na⁺ reflects the state (content) of Na⁺ in the whole organism
   • C - Plasma Na⁺ concentration is a measure of the action of osmoregulatory mechanisms
   • D - In patients with central diabetes insipidus, there is no increase in urine osmolality / plasma osmolality ratio above 50% after ADH administration
6. What are the causes of K⁺ deficiency in the body when vomiting gastric juice?
   • A - Extrarenal loss of K⁺ , which is contained in a relatively high concentration in acidic gastric juice
   • B - Dehydration-induced K⁺ transfer from ECF to ICF
   • C - Decreased circulating volume with consequent increase in aldosterone secretion and renal urinary K⁺ loss
   • D - Alkalemia is accompanied by proportional hypokalemia

Answers

Question 1. A – wrong B - correct - in an adult, 60% of the total body weight is water, 40% is ICF and 20% is ECF. C – wrong D – wrong Question 2. A – wrong B – wrong C – correct– when the osmolality rises to 278 mmol/kg, ADH secretion begins, which increases as the osmolality rises to 298 mmol/kg; after which a further increase in osmolality no longer increases ADH secretion. D – wrong Otázka 3. A – no B – yes C – no D – yes Question 4. A – wrong – gastric juice contains only a small amount of K+, so vomiting can not cause a potassium deficit. B – wrong – dehydration may occur as a result of vomiting but hypokalemia is not caused by the transfer of potassium from ECF to ICF. C – correct – dehydration induced by vomiting (fluid loss) means hypovolemia; this leads to an increase in aldosterone secretion, and there is a decreased resorption of potassium in the distal tubule; the potassium deficit, therefore, arises from increased potassium losses together with bicarbonate in the urine. D – wrong – alkalemia occurs as a result of loss of acidic gastric juice and is accompanied by a decrease in the value of plasma potassium, but this mechanism is not the cause of potassium deficiency in the whole organism.

Case studies

Patient in a diabetic coma

A 15-year-old girl is brought in a coma to the Department of Anesthesiology, Resuscitation and Intensive Medicine. She is a diabetic for 7 years, she takes insulin. She already had several bouts of hypoglycemia and ketoacidosis. She's been studying a lot for school lately and may have neglected some insulin injections.

Examination values

Serum	Values	Blood	Values	Urine	Values
urea	5,8 mmol/l	pH	7,11	ketones	3
creatinine	122 μmol/l	pCO2	2,7 kPa	glucose	3
Na+	148 mmol/l	pO2	12,7 kPa
K+	5,8 mmol/l	glucose	58,3 mmol/l
Cl−	87 mmol/l	HCO3−	8 mmol/l
lactate	5 mmol/l
osmolality	385 mmol/kg

Questions:

1. What is the diagnosis?
2. Calculate the anion gap (AG), what is the cause of high AG?
3. What is the significance of the increased osmolality?
4. Why is chloride and bicarbonate reduced, what is the significance of "normal" sodium and increased potassium?

Answers

Diabetic ketoacidosis (hyperglycemia, acidosis, ketonuria, glycosuria). AG = Na+ + K+ − HCO3− − Cl− = 58.8 mmol/l Increased serum osmolality is due to water loss by osmotic diuresis and hyperglycemia. This is common in ketoacidosis. Diabetic ketoacidosis is a form of metabolic acidosis that leads to a decrease in HCO3-. Patients breathe rapidly to compensate for acidosis and this leads to a reduction in pCO2 (pO2 is usually normal). Hypochloridemia occurs due to osmotic diuresis. High Na+ is relative due to water loss. The patient is thirsty, but usually drinks fluids without enough Na+ and other electrolytes. The K+level is also relative. Only about 2-3% of the total body K+ is in the ECF. Hyperkalaemia is due to severe acidosis and partly to osmotic diuresis (however, many patients with diabetes mellitus have reduced K+ stores). After stabilizing the patient, it is necessary to administer K+ to prevent hypokalaemia.

Obese patient with severe hydration

A 86-year-old woman did not eat or drink fluids for 10 days due to a fever associated with a urinary tract infection and anorexia. Later, she did not eat or drink because she did not leave the bed due to weakness and because she lived alone. A neighbor-called doctor found her in a diseased state and considerable dehydration (dry tongue and mucous membranes, weak skin turgor, she was very thirsty and was breathing fast).

Laboratory values

Serum	Values
Na+	157 mmol/l
K+	3.6 mmol/l
Cl−	121 mmol/l
HCO3−	26 mmol/l
creatinine	135 μmol/l
urea	19.5 mmol/kg

Questions:

1. What kind of indoor environment disorder is it?
2. How is the water redistributed in the body of this patient?

Answers

It is a hypernatremic (hyperosmolar) dehydration. When fluids are not taken in, water is gradually lost more than electrolytes (water vapor in exhaled air and water in insensible perspiration, which is increased during hyperventilation and fever). Significantly higher values ​​of creatinine indicate a reduction in circulating blood volume due to dehydration and centralized circulation. Blood pressure is reduced. The patient must be rehydrated to prevent the so-called shock kidney. When water is depleted faster than electrolyte losses, water is transferred from the ICF to the ECF at the very beginning, and thus intracellular dehydration also occurs rapidly. Therefore, caution should be exercised during therapeutic rehydration and remineralization to avoid the very rapid return of water to cells, especially the CNS, and rapid intracellular expansion.

Patient with lung cancer

Fifty seven year old male with lung cancer (small cell carcinoma) was examined at check-up.

Serum	Values	Urine	Values
Na+	122 mmol/l	osmolality	260 mmol/kg
K+	2.8 mmol/l
Cl-	89 mmol/l
HCO3-	19 mmol/l
osmolality	255 mmol/kg
creatinine	76 μmol/l
urea	3.5 mmol/l

Questions:

1. How do you explain the results of electrolytes and osmolality

Answers [ hide ]

Dilute hyponatremia and hypoosmolality. Due to the fact that this is not an external cause (excessive water supply without electrolytes), the patient has no edema and is not dehydrated (normal urea), glomerular filtration is not limited (normal creatinine), urine osmolality is not significantly reduced (even slightly higher than serum) must be water retention by the renal tubules, ie syndrome of inappropriate ADH. This is the case with ectopic production of ADH (or ADH-like substances), which can occur in some cancers. Small cell lung cancer is an example.

Thirty two year old patient

She hasn't been feeling well for about 3 weeks prior to hospitalization. She started vomiting repeatedly about a week prior to hospitalization. She was dehydrated on admission. There was no evidence of hyperglycosuria or ketonuria in the urine.

Laboratory results

Serum	Values
Na+	120 mmol/l
K+	5.9 mmol/l
Cl-	92 mmol/l
HCO3-	16 mmol/l
creatinine	145 μmol/l
urea	8.4 mmol/l

Questions:

1. Explain the possible cause of the pathological values.

Answers

Metabolic alkalosis and hypokalaemia due to secondary hyperaldosteronism would be expected with repeated vomiting. However, there is hyperkalemia and metabolic acidosis (reduced bicarbonate). So the opposite is true: hypoaldosteronism. Very low serum Na + and increased serum urea are often part of Addison's disease (adrenal cortex insufficiency and mineralocorticoid deficiency)

Heart disease patient treated with thiazide diuretics

A 74-year-old man with congestive heart failure was treated with thiazide diuretics and potassium salts. During the last check-up at, he stated that he felt weak and unbalanced when walking.

Laboratory results

Serum	Values
Na+	135 mmol/l
K+	2.6 mmol/l
Cl-	92 mmol/l
HCO3-	28 mmol/l
creatinine	127 μmol/l
urea	8.4 mmol/l

Questions:

1. How do you evaluate these results?

Answers

Hypokalaemia is common in patients with congestive heart disease treated with thiazide diuretics, despite KCl supplementation, especially in the elderly. This is due to increased urinary excretion of K+. There is also mild hyponatremia induced by hypovolemia due to nonosmotic secretion of vasopressin, which causes water retention (dilute hyponatremia). Volume depletion also causes secondary hyperaldosteronism, which is another reason for the increased excretion of K+ and H+. This also produces metabolic alkalosis. Creatinine and urea levels may be a result of decreased glomerular filtration rate, which is common in the elderly.

Links

Related

• Potassium
• Sodium
• Dehydration
• Acid base balance and its disorders