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Questions and Answers
In the case of vomiting, there is a significant loss of Na while Cl levels remain constant.
In the case of vomiting, there is a significant loss of Na while Cl levels remain constant.
False
Sodium is predominantly found in the intracellular fluid (ICF) of the body.
Sodium is predominantly found in the intracellular fluid (ICF) of the body.
False
The normal range for plasma osmolality is 285-295 mmol/Kg.
The normal range for plasma osmolality is 285-295 mmol/Kg.
True
Arginine vasopressin (AVP) reduces water reabsorption in the kidneys.
Arginine vasopressin (AVP) reduces water reabsorption in the kidneys.
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The calculated osmolality formula includes glucose and blood urea nitrogen.
The calculated osmolality formula includes glucose and blood urea nitrogen.
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In infants, diarrhea causes a severe impairment of their internal water and electrolyte balance.
In infants, diarrhea causes a severe impairment of their internal water and electrolyte balance.
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The urine osmolality to serum osmolality ratio is normally greater than 3.
The urine osmolality to serum osmolality ratio is normally greater than 3.
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Renal failure is indicated by a urine osmolality to serum osmolality ratio of less than 1.1.
Renal failure is indicated by a urine osmolality to serum osmolality ratio of less than 1.1.
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Colloid osmotic pressure affects movement of water only within the intravascular compartment.
Colloid osmotic pressure affects movement of water only within the intravascular compartment.
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The glomerular filtration rate (GFR) is an important regulator of sodium excretion.
The glomerular filtration rate (GFR) is an important regulator of sodium excretion.
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Atrial Natriuritic peptides (ANP) are primarily involved in potassium balance in the body.
Atrial Natriuritic peptides (ANP) are primarily involved in potassium balance in the body.
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Dehydration in infants due to vomiting and diarrhea leads to a decrease in both intracellular fluid (ICF) and extracellular fluid (ECF).
Dehydration in infants due to vomiting and diarrhea leads to a decrease in both intracellular fluid (ICF) and extracellular fluid (ECF).
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The main intracellular cation in the human body is sodium.
The main intracellular cation in the human body is sodium.
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Hyponatraemia refers to a condition characterized by low levels of sodium in the blood.
Hyponatraemia refers to a condition characterized by low levels of sodium in the blood.
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In cases of hypoproteinaemia, reduced plasma albumin results in increased reabsorption of interstitial fluid at capillaries.
In cases of hypoproteinaemia, reduced plasma albumin results in increased reabsorption of interstitial fluid at capillaries.
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The effusion of potassium during hemolysis leads to false high results in blood potassium analysis.
The effusion of potassium during hemolysis leads to false high results in blood potassium analysis.
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ADH is responsible for promoting water excretion in the body.
ADH is responsible for promoting water excretion in the body.
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Patients undergoing major elective surgery require a pre-operative assessment of their electrolyte balance.
Patients undergoing major elective surgery require a pre-operative assessment of their electrolyte balance.
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Correction of fluid requirements includes calculating the basic replacement of insensible losses, which is usually around 1200 ml.
Correction of fluid requirements includes calculating the basic replacement of insensible losses, which is usually around 1200 ml.
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Hypernatraemia indicates an excess of sodium in the blood.
Hypernatraemia indicates an excess of sodium in the blood.
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In cases of excessive sweating, it is necessary to replace fluid losses with 500 ml of isotonic NaCl.
In cases of excessive sweating, it is necessary to replace fluid losses with 500 ml of isotonic NaCl.
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The sodium requirement can be accurately calculated using a 0.9% normal saline solution, which contains 154 mmol of NaCl per liter.
The sodium requirement can be accurately calculated using a 0.9% normal saline solution, which contains 154 mmol of NaCl per liter.
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In cases of acute fluid loss due to pyrexia, the preferred solution to administer is 5% dextrose.
In cases of acute fluid loss due to pyrexia, the preferred solution to administer is 5% dextrose.
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Potassium chloride should be administered cautiously, especially if plasma potassium levels exceed 7.5 mmol/l.
Potassium chloride should be administered cautiously, especially if plasma potassium levels exceed 7.5 mmol/l.
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Normal plasma potassium levels range from 3.5 to 5.5 mmol/l.
Normal plasma potassium levels range from 3.5 to 5.5 mmol/l.
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If urine output is low, it is advisable to decrease the flow rate of fluids.
If urine output is low, it is advisable to decrease the flow rate of fluids.
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Monitoring urine output is not essential as long as the input is measured.
Monitoring urine output is not essential as long as the input is measured.
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Ringer solution contains sodium, potassium, calcium, and chloride as its primary components.
Ringer solution contains sodium, potassium, calcium, and chloride as its primary components.
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To convert mass unit concentrations to SI units, a mass concentration of 0.9% is typically used.
To convert mass unit concentrations to SI units, a mass concentration of 0.9% is typically used.
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Isotonic NaCl is indicated for gastrointestinal disturbances as well as pyrexia and sweating.
Isotonic NaCl is indicated for gastrointestinal disturbances as well as pyrexia and sweating.
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Study Notes
Water & Electrolyte Balance
- Disturbances in water and electrolyte balance can be external or internal.
- External disturbances cause the input and output of Na, K, and water to be equal, maintaining constant amounts in the body.
Daily Intake and Output
- A healthy adult in a temperate climate consumes approximately 1500 mL of water through drinking, 750 mL from food, and 250 mL from metabolism. The total daily intake is 2500 mL.
- The total daily output is also 2500 mL, consisting of 1600 mL of urine, 50 mL of water from feces, 850 mL from expired air, and insensible perspiration.
- Daily intake and output of Na+, K+, and Cl− for a healthy adult are between 100-200 mmol/24h.
Distribution of Water
- An adult (70 kg) has approximately 42 liters of total body water, comprising 20% of extracellular fluid (14 litres) and 60% of intracellular fluid (28 litres).
- An infant (3 kg) has approximately 2.1 litres of total body water, with 40% of extracellular fluid (1.2 litres) and 70% of intracellular fluid (0.9 litres).
Digestive Tract Secretions
- Daily secretions entering the digestive tract include saliva (1-2 L), gastric juice (1-4 L), pancreatic juice (0.5-1.5 L), bile (0.5-1 L), and intestinal secretions (2-4 L).
- These secretions contain various electrolytes (e.g., Na+, K+, Cl−, HCO3−), which are typically reabsorbed.
- Large losses of water and electrolytes can occur during illness.
Water & Na Balance
- Total body sodium is approximately 4200 mmol, distributed 50% in extracellular fluid (ECF), 40% in bone, and 10% in intracellular fluid (ICF).
- Sodium is primarily found in the ECF, while potassium is primarily found in the ICF.
- Osmolality (particles of solutes per kg of plasma) and colloid osmotic pressure influence fluid distribution throughout the ECF compartments.
Osmolality
- Osmolality is measured by an osmometer, estimating the freezing point depression when adding solute to water. Another way to calculate it is with the formula 2[Na] + 2[K] + Glucose/18 + Blood Urea/6.
- Normally, urine osmolality-to-serum osmolality ratio is 1:3. This ratio can change in conditions like renal tubular deficiency, polyuria (in diabetes insipidus), prerenal failure, and renal failure.
External Balance (Water)
- Water balance is controlled by thirst (increasing water intake).
- Arginine vasopressin (AVP) or antidiuretic hormone (ADH) increases water reabsorption in the renal tubules in response to high plasma osmolality or low ECF volume.
External Balance (Sodium)
- The most important regulators of sodium excretion are glomerular filtration rate (GFR), the renin-angiotensin-aldosterone system, atrial natriuretic peptides (ANP), and dopamine.
ADH
- ADH leads to water retention by the action of osmoreceptors in the hypothalamus.
Depletion & Excess of Water
- Water loss is common due to intake, abnormal losses. (e.g., skin, renal tract).
- Water excess is unusual and often due to excessive intake, or reduced renal loss.
Na Depletion & Excess
- Sodium depletion results from factors like reduced oral intake, excessive sweating,vomiting, diarrhoea, or osmotic diuresis.
- Excess sodium may be the result of increased oral or parenteral intake, or reduced renal losses.
Oedema
- Oedema (swelling) may occur when plasma albumin is low, reducing oncotic pressure, drawing fluid into the interstitial spaces.
- Hydrostatic factors like increased venous pressure can also contribute to oedema.
Hypernatremia
- Hypernatremia (high blood sodium) occurs due to decreased body sodium (loss of water and sodium) in extra-renal or renal loss, or increased body sodium (retention of sodium).
Hyponatremia
- Hyponatremia (low blood sodium) occurs due to extra-renal or renal loss of sodium, or due to increased water causing low ECF volume.
Potassium Balance
- Potassium (K) is primarily intracellular, with 98% of the body's potassium in cells and only 2% in extracellular fluid.
Fluid Balance Post-Operative Management
- Post-operative patients at risk for fluid imbalances need baseline assessments of sodium, potassium, chloride, blood urea, creatinine, and liver function tests.
- Corrective measures are implemented to address fluid imbalances.
- The basic replacement for fluid needed often starts with calculating insensible fluid losses and considering previous urine output and other typical losses like sweating.
Intravenous Preparations
- Normal saline (0.9% NaCl), dextrose solutions (5%, 10%, 20%), and Ringer's solution are common intravenous preparations.
Calculation of Values
- To convert a mass value to a molar unit (e.g., from grams to moles per litre) the molar mass of the compound is used, along with the volume of the solution being measured.
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Description
Test your knowledge on water and electrolyte balance, including daily intake and output, and the distribution of body water. This quiz covers essential concepts relevant to a healthy adult's hydration and the role of electrolytes in the body.
