Consequences of fluid loss from the GI Tract Flashcards Preview

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Flashcards in Consequences of fluid loss from the GI Tract Deck (28)
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1
Q

How much liquid, food and metabolically produced liquid do we consume and contain (ml)?

A
  • Liquids: 1200ml
  • Food: 1000ml
  • Metabolically produced: 350ml
  • Total: 2550ml
2
Q

How much liquid do we excrete (insensible water loss, sweat, faeces and urine)

A
  • “Insensible water loss” (skin and lungs): 900ml
  • Sweat: 50ml
  • Faeces: 100
  • Urine: 1500
3
Q

Excretion is usually small, however when can this increase?

A

Excretion is usually small, but large in diarrhoea, sweating, vomiting, haemorrhage → loss of water and salts

4
Q

What is our intake and output of NaCl?

A

Intake (grams):
• Food: 10.5g

Output (grams):
•	Sweat: 0.25g
•	Faeces: 0.25g
•	Urine: 10.00g – varies considerably
•	Total output: 10.5g
5
Q

List ways in which fluid is lost and gained

A
  • Defecation; diarrhoea
  • Vomiting: what is lost?
  • Urination
  • Ventilation
  • Sweating
  • Menstruation

Water gain:
• Drinking
• Metabolic

6
Q

What causes diarrhoea?

A

Occurs as a result of:
• Failure of water absorption
• ↑ secretion or both

7
Q

What causes decreased absorption?

A

Causes of decreased absorption:
• ↑ number of osmotic particles (osmotic diarrhoea)
• ↑ rate of flow of intestinal contents (deranged motility diarrhoea)
• Abnormal increase in secretions of GIT (secretory diarrhoea)

8
Q

Define Osmotic diarrhoea

What causes it?

A

Decreased absorption of electrolytes and nutrients

Disaccharidase deficiency (disaccharide deficiency/malabsorption), drug-induced, malabsorption of galactose)

9
Q

Define Secretory diarrhoea

What causes it?

A

ACh, substance P, 5-HT and neurotensin act via ↑[Ca2+] to increase rate of intestinal secretion

• Excessive laxative use, defects in digestion and absorption; infections [e.g. cholera (Vibrio cholerae)]

- Survives acidic conditions of the gut
- Enterotoxin stimulates adenylate cyclase → ↑ cAMP → Na+, Cl- and water loss
- Replace water, electrolytes and glucose (treatment)

10
Q

What causes traveller’s diarrhoea?

A

Bacteria

11
Q

What is inflammatory bowel disease?

A

Exudative diarrhea occurs with the presence of blood and pus in the stool. This occurs with inflammatory bowel diseases,

12
Q

What is deranged motility diarrhoea?

What promotes it?

A

Deranged motility diarrhoea: lack of absorption; some agents may promote secretion as well as motility

GI stasis may promote diarrhoea by stimulating bacterial overgrowth

13
Q

What 2 bacteria cause Parasitic diarrhoea?

A

Entamoeba histolytica and Giardia lamblia

14
Q

What symptoms does Entamoeba histolytica cause?

A
  • Entamoeba histolytica → asymptomatic or amoebic dysentery
  • Gradual in onset → systemic symptoms (anorexia, headache)
  • Metronidazole
15
Q

What symptoms does Giardia cause?

A
  • Giardia → steatorrhoea and abdominal pain; maldigestion & malabsorption of lipids, CHOs, vit A, vit B12, folic acid
  • Metronidazole or tinidazole
16
Q

What is dysentery?

What does it cause?

A

Dysentery is an intestinal inflammation, primarily of the colon.

Painful, bloody, low volume diarrhoea

17
Q

What are the major consequences of diarrhoea?

A

Consequences of excessive loss of water, nutrients, Na+, K+ and HCO3- :

  • ↓ blood volume (hypovolaemia)
  • Metabolic acidosis – due to loss of HCO3- e.g., in diarrhoea
18
Q

Describe the physiological response to diarrhoea

A

On image - LEARN IS IMPORTANT

19
Q

Describe the physiological response to sweating

A

On image

20
Q

Describe the response of the body to the consequences hypovolaemia: RAAS cascade

A

On image

21
Q

Describe physiologic response to the consequences of hypovolaemia

A

On image

22
Q

Describe the physiologic response to the consequences of hypovolaemia - THIRST

A

On image

23
Q

Describe the effects of dehydration on calcium

A
  • Dehydration →imbalance of electrolytes in the bloodstream (↓ NaCl and K+), but it also ↑[Ca2+]
  • ↑ [Ca2+] → hypercalcaemia
  • Hypercalcaemia → ↑ risk of kidney stones, kidney failure, dementia and arrhythmia.
24
Q

What are the symptoms of hypercalcaemia?

A
If mild= asymptomatic
•	Nausea
•	Vomiting
•	Loss of appetite
•	Constipation
•	Abdominal pain 
•	Excessive thirst
•	Fatigue, lethargy, muscle weakness
Joint pain, confusion
25
Q

What regulates water loss?

A

Vasopressin (antidiuretic hormone, ADH)
• ADH stimulates thirst mechanism
• Increased osmolarity of body fluids → ADH release

26
Q

How does ADH work?

A

• Inserts water channels (aquaporin-2) in collecting duct of kidney
• This increases the permeability of the collecting ducts to H2O and results in concentrated urine production
• Intake of plain H2O → a ↓ in osmolarity of blood and interstitial fluid
o This decreases ADH secretion and the removal of the water channels
• If there are no water channels, this causes decreased permeability of collecting ducts to water and increased water loss

27
Q

Describe the factors that regulate ADH release

A
  1. Large decrease in blood volume (detected by baroreceptors)*
  2. Severe dehydration: under this condition, GFR decreases causing less H2O in urine*
  3. Hyperventilation: results in increased fluid loss (exhalation)*
  4. Vomiting/diarrhoea: causes increased fluid loss from GIT*
  5. Fever, heavy sweating, and burns cause large H2O loss*

*ADH secretion in all these cases leads to conservation of body H2O
• This is through the sequence of events we just talked
• Intake of copious amounts of water: results in high BP which causes increased GFR and increased H2O in urine

28
Q

Summary of factors that maintain body water balance

A

On table

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