Fluid and Electrolyte balance Flashcards
Describe the different body fluid compartments and the approximate proportion of fluid inside each one.
Two fluid compartments:
- Intracellular fluid = 2/3 total body fluid
- Extracellular fluid= 1/3 total body fluid which consists of 80% interstitial fluid and 20% plasma
Discuss the pressures involved in the movement of water between the plasma, interstitial fluid, lymphatic vessels and intracellular fluid.
The pressures involved in the movement of fluid across the fluid compartments include:
• the capillary hydrostatic pressure (the blood pressure that tends to push against the vessel wall and drive fluid out of the capillary)
• the capillary oncotic pressure (the osmotic pressure of proteins in the blood that pull fluid into the intravascular space)
• the interstitial hydrostatic pressure (that pushes fluid towards the intravascular space)
• the interstitial oncotic pressure (the pressure of proteins in the intravascular space that pulls fluid out of the capillaries).
The latter force is fairly minimal. Normally, the balance of forces still means a small net loss of fluid into the interstitial space, which is drained back into the bloodstream by the lymphatic system.
Explain how an increase in capillary hydrostatic pressure causes oedema, and how a decrease in capillary oncotic pressure causes oedema.
If the capillary hydrostatic pressure rises above normal or the capillary oncotic pressure falls below normal, this encourages more fluid to move out of the capillaries and into the interstitium, causing oedema.
Describe what is meant by fluid being in the third space.
Third spacing refers to fluid that pools outside of a normal fluid compartment.
Briefly describe how sodium, chloride and potassium are normally kept in balance.
If serum sodium levels are decreased or potassium levels are too high, the renin-angiotensin-aldosterone system is activated and the body secretes aldosterone, which causes the kidneys to reabsorb sodium and secrete potassium into the filtrate, adjusting the balance back to normal. Aldosterone also causes more potassium to be excreted in sweat. Chloride has a negative charge that allows it to interact with sodium so the passive transport of chloride follows the active transport of sodium, with levels rising and falling in concert.
Briefly list some common causes of water deficit.
Blood loss Trauma surgery Fluid loss – Severe vomiting/diarrhoea Burns Third spacing
List some causes of water excess. why is the healthy body unable to remain in a state of water excess.
- Acute kidney injury
- Severe congestive heart failure
- Liver cirrhosis
because of the lymphatic system
Discuss why metabolic dysfunctions occur in potassium deficiency and in potassium excess.
Potassium deficiency: hypokalemia
• Because insulin secretion is depressed and muscle excitability and liver glycogen synthesis is reduced
Potassium excess: hyperkalemia
• Because renal function is affected, resulting in fluid retention and oliguria. Muscle excitability
What is the most prominent ECG change associated with hyperkalaemia?
ST-segment depression, flat P wave, wide QRS complex and peaked T wave.
What is the most prominent ECG change associated with hypokalaemia?
Flattening of the T wave and the appearance of a U wave
Identify four clinical manifestations associated with respiratory alkalosis.
Lightheaded Hypertension Dry mouth Palpitation Bloating Tachycardia Decrease BP or normal
Explain how hyperglycaemia contributes to dehydration and metabolic acidosis.
High blood sugar causes further dehydration as your kidneys attempt to get rid of glucose and ketones by producing large amounts of urine. Increased dehydration causes higher blood sugars, which in turn cause further dehydration.
Identify five risk factors associated with the development of fluid, electrolyte and acid-base imbalances.
- Age
- Gender
- Body size
- Environmental temperature
- Lifestyle
Explain the clinical implications of hypovolaemia and hypervolaemia.
Hypovolemia:
Acute weight loss Decrease skin turgor Oliguria Concentrated urine Cool clammy skin due to peripheral vasoconstriction Thirst Anorexia tachy
Hypervolemia:
Odema Crackles, abnormal lung sounds Increased BP Bradycardia Increased CVP Increased weight Increase urine output SOB and wheezing
Discuss the role of Antidiuretic hormone in maintaining homeostasis of body fluids.
The antidiuretic hormone helps to control blood pressure by acting on the kidneys and the blood vessels. Its most important role is to conserve the fluid volume of your body by reducing the amount of water passed out in the urine.
