Consequences of fluid loss from the GI Tract Flashcards
How much liquid, food and metabolically produced liquid do we consume and contain (ml)?
- Liquids: 1200ml
- Food: 1000ml
- Metabolically produced: 350ml
- Total: 2550ml
How much liquid do we excrete (insensible water loss, sweat, faeces and urine)
- “Insensible water loss” (skin and lungs): 900ml
- Sweat: 50ml
- Faeces: 100
- Urine: 1500
Excretion is usually small, however when can this increase?
Excretion is usually small, but large in diarrhoea, sweating, vomiting, haemorrhage → loss of water and salts
What is our intake and output of NaCl?
Intake (grams):
• Food: 10.5g
Output (grams): • Sweat: 0.25g • Faeces: 0.25g • Urine: 10.00g – varies considerably • Total output: 10.5g
List ways in which fluid is lost and gained
- Defecation; diarrhoea
- Vomiting: what is lost?
- Urination
- Ventilation
- Sweating
- Menstruation
Water gain:
• Drinking
• Metabolic
What causes diarrhoea?
Occurs as a result of:
• Failure of water absorption
• ↑ secretion or both
What causes decreased absorption?
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)
Define Osmotic diarrhoea
What causes it?
Decreased absorption of electrolytes and nutrients
Disaccharidase deficiency (disaccharide deficiency/malabsorption), drug-induced, malabsorption of galactose)
Define Secretory diarrhoea
What causes it?
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)
What causes traveller’s diarrhoea?
Bacteria
What is inflammatory bowel disease?
Exudative diarrhea occurs with the presence of blood and pus in the stool. This occurs with inflammatory bowel diseases,
What is deranged motility diarrhoea?
What promotes it?
Deranged motility diarrhoea: lack of absorption; some agents may promote secretion as well as motility
GI stasis may promote diarrhoea by stimulating bacterial overgrowth
What 2 bacteria cause Parasitic diarrhoea?
Entamoeba histolytica and Giardia lamblia
What symptoms does Entamoeba histolytica cause?
- Entamoeba histolytica → asymptomatic or amoebic dysentery
- Gradual in onset → systemic symptoms (anorexia, headache)
- Metronidazole
What symptoms does Giardia cause?
- Giardia → steatorrhoea and abdominal pain; maldigestion & malabsorption of lipids, CHOs, vit A, vit B12, folic acid
- Metronidazole or tinidazole
What is dysentery?
What does it cause?
Dysentery is an intestinal inflammation, primarily of the colon.
Painful, bloody, low volume diarrhoea
What are the major consequences of diarrhoea?
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
Describe the physiological response to diarrhoea
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Describe the physiological response to sweating
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Describe the response of the body to the consequences hypovolaemia: RAAS cascade
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Describe physiologic response to the consequences of hypovolaemia
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Describe the physiologic response to the consequences of hypovolaemia - THIRST
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Describe the effects of dehydration on calcium
- 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.
What are the symptoms of hypercalcaemia?
If mild= asymptomatic • Nausea • Vomiting • Loss of appetite • Constipation • Abdominal pain • Excessive thirst • Fatigue, lethargy, muscle weakness Joint pain, confusion
