Fluid and Electrolytes

Flashcards about Fluid and Electrolytes lecture notes.

What is the approximate body water content as a percentage of body weight?

60% in males and 55% in females

What are the percentages of body water present in ICF and ECF?

66% ICF and 33% ECF

What are the predominant ions in ICF and ECF?

Na+ predominant in ECF, K+ in ICF

What is the difference between osmolality and osmolarity, and how are they determined?

Osmolality is measured using an osmometer via freezing point depression, while osmolarity is calculated.

How is osmolarity calculated?

2[Na+] + [urea] + [glucose]

How do you calculate the osmolal gap (OG)?

Measured osmolality minus calculated osmolarity.

What are the two major homeostatic systems involved in the control of salt and water balance?

Renin-angiotensin-aldosterone (RAA) system and Antidiuretic hormone (ADH)

What defines hyponatremia?

Plasma concentration below approximately 135 mmol/L

What can cause pseudo-hyponatremia?

Excess lipid or protein

What are the symptoms of cerebral edema due to rapid decline in sodium levels?

Nausea and vomiting, confusion, coma, and even death

What is the treatment for hypervolemic hyponatremia?

Lasix plus fluid restriction

What is the treatment for euvolemic hyponatremia?

Fluid restriction

What is the treatment for hypovolemic hyponatremia?

Saline rehydration

What are the diagnostic criteria for SIADH (Syndrome of Inappropriate ADH secretion)?

Hyponatremia and low serum osmolality, urine osmolality >100 mOsm/kg, normal ECF volume, normal kidney, adrenal and thyroid function and the patient must not be on any drug that may cause hyponatremia.

What defines hypernatremia?

Serum concentration > 145 mmol/L

What is a prerequisite for hypernatremia?

Inadequate water intake

What is the treatment for hypervolemic hypernatremia?

Furosemide and 5% dextrose IVI

What is the treatment for euvolemic hypernatremia?

5% dextrose IVI or H2O orally or n-g tube

What is the treatment for hypovolemic hypernatremia?

Isotonic saline and 5% dextrose IVI

How does the brain adapt to hyponatremia?

Secreting idiogenic molecules (osmolytes) out of brain cells to ECF.

How does the brain adapt to hypernatremia?

Accumulating intracellular idiogenic molecules.

List factors that influence urinary K+ excretion:

Circulating aldosterone levels, amount of Na arriving at the distal tubules, relative availability hydrogen and potassium levels of the cells at the distal tubules and collecting ducts, capacity of the cells to secrete hydrogen ions, dietary potassium intake, Intravascular volume

Examples of transcellular K+ movement that cause hypokalemia:

Alkalosis, Insulin administration, Refeeding syndrome, Increased K excretion

Examples of renal causes that can lead to hypokalemia:

Diuretics, AKI (diuretic phase), RTA 1 and 2, Mineralocorticoid excess, Tubular disorders

Examples of extra renal causes that can lead to hypokalemia:

Diarrhoea and Vomiting

What can cause spurious hyperkalemia?

Haemolysis, EDTA contamination, Old sample, Abnormal blood cells

Examples of transcellular movement that cause hyperkalemia:

Acidosis, Tissue damage (tumour lysis syndrome), Vigorous exercise

List conditions that cause decreased K+ excretion leading to hyperkalemia:

AKI and CKD, K‐sparing diuretics, Mineralocorticoid deficiency

What are the 3 key points about fluid and electrolyte balance?

Sodium, potassium, and water homeostasis are interlinked; Na and K are transported actively, and H2O follows passive transport.