Lecture 9 Fluid Balance and Renal Disease Flashcards
What is the total body water and its percentage in humans?
60% (40-70% of body mass)
- Total body water is slightly lower in females (55%) than in males (60%)
-
How many % of water are in muscles and fat cells?
70% in muscle cells
10% in fat cells
2/3 of total body water is located inside/outside cells?
- Inside (Intra-cellular volume)
- muscle (70%) and fat cells (10%)
1/3 of total body water is located inside/outside cells?
- Outside (extra-cellular volume)
- Interstitial
- plasma
-l ymph
This is the process of loosing water
Dehydration
This is the process of regaining body water to a euhydrated (optimal state)
Rehydration
Where do we get most of our fluids from? (Note: This card also shows stats on other water inputs)
- Fluids 50-60%
- Food 30-40%
- Metabolism 10-15%
- Higher from fruit and veg, lower from high fat foods
Information about water output (Tap card)
- urine 50-60%
- Faeces - 5%
- sweat - 5%
- insensible loss
- skin - 20-30%
- lungs - 10-15%
Greater in dry climates and less in humid climates
What are the roles of the renal system?
- formation and excretion of urine
- regulate blood volume and blood pressure
- Regulates sodium, potassium, chloride, calcium plasma ion concentration
- Stabilises blood pH (H+ and bicarbonate)
- conserve nutrients - glucose and amino acids
- Excrete waste - urea and ammonium
- Detoxify poisons and drugs
Where is the integration centre for the regulation of body fluids and electrolytes?
- Hypothalamus
Inputs to the Hypothalamus: - osmoreceptors
- atrial baroreceptors
- arterial baroreceptors
- thirst (hypothalamus)
Outputs to Hypothalamus - hormones and modulators
- antidiuretic hormone (ADH) or vasopressin
- aldosterone
- Angiotensin Converting Enzyme (ACE)
- Atrial Natriuretic Peptide (ANP)
Hormone secreted from the cells in the posterior pituitary, its release is stimulated by the activation of the hypothalamic neurons.
Antidiuretic Hormone (ADH)
- Responds to osmoreceptor inputs (if fluid volume down, osmolarity up) and Baroreceptor inputes (if fluid down, bp down)
- Effects of ADH:
- increase water reabsorption in distal and collecting tubules of kidneys (decreases urine output and increases extra cellular volume)
- Increases arteriolar constriction (vasopressive effect)
A hormone secreted by the adrenal cortex and its release is stimulated by low arterial BP and low renal blood flow.
Aldosterone
- Low renal blood flow - stimulates release of renin from the kidneys
- Renin converts angiotensinogen to angiotensin I and ACE converts angiotensin I to angiotensin II
- Effects of Aldosterone:
- increases Na+ reabsorption in the kidneys
- increases water reabsorption (passive to Na+) in kidneys
- Decrease Na+ loss in sweat
- Increase ECV (plasma volume)
What are the effects of Angiotensin II
- increases ADH release
- increases aldosterone release
- Arteriolar vasoconstriction (increases BP)
- increase thirst
An enzyme secreted by the lungs that converts angiotensin I to angiotensin II
Angiotensin Converting Enzyme (ACE)
- Angiotensin II has major effects on sodium and fluid balance
ACE inhibitors are a major class of drugs used in the treatment of hypertension
Its release is stimulated by atrial stretch (increase in central blood volume)
Atrial Natiuretic Peptide (ANP)
- aka Atrial Natiuretic hormone or factor
- Secreted from atrial cells mostly from the right atrium
Effects of ANP:
- increase diuresis (fluid loss)
- blocks release of ADH
- blocks release of aldosterone
- Blocks Na+ reabsorption in kidneys
Reduces sympathetic cardiac and vasoconstrictor drive and arteriolar vasoconstriction directly (decreases arterial BP)
*Mechanism of fluid loss when exposed to cold
What are the effects of Exercise on fluid and electrolyte balance? (During exercise)
- increase sweating
- increase osmotic pressure in cells due to metabolites (water will try and go into cells)
- Increase hydrostatic pressure due to increased BP
Effects: Water moves from plasma into interstitial and intracellular spaces
- Water lost from body
- Some electrolytes lost from the body
Impacts and risks:
- Decrease blood volume
- Compromise cardiac output and blood pressure
What is the physiological response of exercise in relation to fluid balance?
- Inputs:
increased blood osmolality stimulates osmoreceptors in hypothalamus
Responses
- increase ADH release
- increase renin, angiotensin II and aldosterone release
- Decrease ANP release
Effects of hormonal changes causes:
- increase sodium reabsorption
- increase water reabsorption
- decrease urine output
- increase plasma volume
What are the Effects of repeated days of physical activity?
- increases release of fluid balance hormones
- increased plasma volume
- Possible haemodilution
- possible pseudoanemia - sports anemia - essentially you have hemodilution, haematocrit normal but plasma really really high
Preventing dehydration with exercise information (Tap Card)
- ensure at least euhydration pre-exercise
- weigh before and after exercise
- consume fluid to volume lost plus 25%
- ensure urine colour returns to pale yellow
- Hydrate during exercise if:
- long duration
- high ambient temperature
- high humidity
Consume appropriate sports drink if rate of rehydration is important
Be cautious of salt intake
Occurs due to excessive water intake relative to sodium - prolonged sweating and excess plain water intake
Hyponatremia
- Sodium = Natrium (Na+)
water intoxication - Serum Na < 136 meq/L (150 Normal)
Mild symptoms are: headache, nausea, cramps, confusion
Severe symptoms are: seizures, coma, pulmonary oedema, death
What are two major causes of renal diseases?
- Diabetes - 45%
- Hypertension - 27%
(Hypokinetic diseases)
M>F 3:2 ratio
Exercise testing on patients with Renal Disease
- Aerobic testing
*Stages 1-4 - usual considerations
*Transplant - usual considerations
*Stage 5 - requires medical supervision
*Hemodialysis - test on non-dialysis days
*Peritoneal - test when no fluid in the abdomen
Strength testing:
- 3RM or more (not 1 RM)
- Isokinetic - slow velocities (60-180 deg/s)
- Sit to stands
Exercise training recommendations for people with renal diseases. (Aerobic Activities, CV)
- low-mod intensity activities (40-60% max then progress if can)
- As many days as possible
- RPE (11-13) HR is poor indicator
- non dialysis days (RPE 11-16)
- begin with intermittent interval activity
- Progress to continuous
- Aim for 30-45 min continuous (longer if overweight/obese)
Exercise training recommendations for people with renal diseases. (Strength Training)
- aim to increase muscle mass
- 1 set of 10-15 reps to fatigue
- 8-12 exercises targeting major muscle groups
- 2x week non consecutive days
- motivation often difficult
