Consequences of Fluid Loss from the GIT Flashcards

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1
Q

How is water gained and lost?

A

Gained in liquids, foods, metabolism and is lost in sweat, urine, faeces, menstruation, vomiting

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2
Q

What is Diarrhoea?

What can cause bloody diarrhoea?

A
  • • Increased frequency and volume of water faeces
    • Occurs as a result of failure of water reabsorption/increased secretion, due to:
    o ↑Osmolality of stool
    o ↑Gut motility - Deranged motility diarrhoea
    o Abnormal increase in secretions of GIT - Secretory diarrhoea
  • Due to Chronic disease, Ulcerative colitis, Neoplasm
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3
Q

Compare Osmotic, Secretory, Deranged Diarrhoea

A
Osmotic Diarrhoea:
Decreased absorption of electrolytes and nutrients
• Drug-induced
• Malabsorption
• Disaccharide deficiency

Secretory Diarrhoea:
Abnormal increase in secretions
• Excessive laxative use
• Infections

Deranged Diarrhoea:
Lack of absorption, may be an increase in motility/secretion
• GI stasis stimulating bacterial overgrowth

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4
Q

What are the peristaltic causes of diarrhoea?

What are the consequences of diarrhoea?

A
  • • Entamoeba histolytica - Gradual onset, treat with Metronidazole
    • Giardia - Steatorrhoea, abdominal pain, treat with Metronidazole/Tinidazole
  • • Excessive loss of water, nutrients, electrolytes = Hypovolemia, Hypokalaemia, Hyponatraemia
    • Metabolic Acidosis - due to loss of HCO3-
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5
Q

What is Vomiting? What does it do?

What are the physiological effects of vomiting?

A
  • • Retrograde contraction of GIT, causing oral expulsion of gastric contents and bile
    • Occurs in pregnancy, metabolic disorders, illness, alcohol dependency
    • Allows for the removal of ingested toxic substances
  • Physiological effects include:
    o ↑Salivation, HR, Sweating
    o Pallor, Nausea (avoid ingesting toxic substances again)
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6
Q

What is the mechanism of Vomiting?

What are the inputs that initiate vomiting?

A

• Neuronal inputs from body to Vomiting Centre in the Medulla:

  1. Deep inspiration = ↑abdominal pressure - retrograde contraction
  2. Breath held, chest fixes to ↓Oesophageal pressure = relaxation of sphincters
  3. Retching and forceful expulsion
  • Distension of stomach/small bowel, ↑Intracranial pressure, Motion Sickness, Intense pain, Gag reflex, Smell/sight/emotion
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7
Q

What are consequences of Vomiting?

A
  • Excessive salt, water, nutrient loss
  • Dehydration
  • Metabolic Alkalosis - loss of gastric acid
  • Hypovolaemia, Hypokalaemia, Hyponatraemia
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8
Q

What are the consequences of fluid loss from the GIT?

A

• Hypovolemia
o ↓Venous return = ↓SV/CO = Hypotension = Myocardial dysfunction due to ↓tissue perfusion. As a result, there is ↑Anaerobic metabolism = Acidosis - Acidosis and Myocardial dysfunction = Multi-organ failure

  • Polycythaemia (↑RBC%) - due to reduced plasma volume
  • Dehydration and Malnourishment
  • Ionic imbalances - poor tissue perfusion
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9
Q

What are the responses to water loss?

A
  • Cardiovascular adaptations - Vasoconstriction, RAAS activation
  • Renal adaptation - ADH secretion, RAAS activation = ↓Urine production
  • Behavioural adaptation - osmoreceptors = ↑Thirst
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10
Q

What is Hypercalcaemia a consequence of?

What are its symptoms?

A
  • Dehydration - due to ionic imbalance
  • Nausea, Vomiting, Loss of appetite, excessive thirst, Constipation, abdominal and joint pain, Fatigue, lethargy, muscle weakness
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11
Q

What are the 4 mechanisms used in the maintenance of water balance?

A
  1. ADH: ↑Permeability of CD = ↑H2O reabsorption
  2. Thirst reflex: ↑Desire to drink
  3. ANP: Stimulates Natriuresis: ↑Na+, Cl-, H2O excretion
  4. RAAS: Aldosterone - ↑Na+/H2O reabsorption
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12
Q

How does ADH work in water balance?

A
  • Stimulates the thirst reflex
  • ↑Water reabsorption in CD
  • Intake of water ↓plasma osmolality, which then ↓ADH secretion
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