Consequences Of Fluid Loss From The GI Tract Flashcards
How can water be lost from the body?
Defecation, vomiting, urination, ventilation, sweating, mensturation
How can you gain water?
Drinking
Metabolic water
What is the definition of diarrhoea?
Increased frequency (>3 unformed stools in 24 hours) of increased volume and fluidity of faeces
What does diarrhoea occur as a result of?
Failure of water absorption, increased secretion of water or both
What causes osmotic diarrhoea?
Decreased absorption of electrolytes and nutrients
What is the treatment of osmotic diarrhoea?
Electrolytes and water
What are the symptoms of disaccharidase deficiency?
Bloating, nausea and watery diarrhoea
What is the treatment for disaccharidase deficiency diarrhoea?
Glucose
What is disaccharidase deficiency diarrhoea caused by?
Drug induced malabsorption of galactose
What is deranged motility diarrhoea?
Increased rate or flow of intestinal contents
What does increased rate or flow of intestinal contents cause?
Lack of absorption
What causes secretory diarrhoea?
Abnormal increase in secretions of GIT
How does secretory diarrhoea work?
ACh, substance P, 5-HT and neurotensin act via increased calcium ion concentration to increase rate of intestinal secretion
What is secretory diarrhoea caused by?
excessive laxative use, defects in digestion and absorption and infections
How do infections cause secretory diarrhoea?
Enterotoxin stimulates adenylate cyclase -> increased cAMP -> sodium and chloride ions and water loss
What are the treatments for secretory diarrhoea?
Water, electrolytes and glucose
What two parasites can cause diarrhoea?
Entamoeba histolytica and giardia
What does enterotoxin stimulate?
Adenylate cyclase -> inc cAMP -> sodium and chloride ions and water loss
What are the symptoms of amoebic dysentery?
Gradual onset anorexia/ headache
What do you treat entamoeba histolytica with?
Metronidazole
What are the symptoms of giardia?
Steatorrhoea and abdominal pain
What does the giardia parasite cause?
Maldigestion and malabsorption of lipids, CHOs, vit A, B12 and folic acid
What do you treat giardia caused diarrhoea with?
Metronidazole or tinidazole
What is dysentery?
Painful, bloody, low volume diarrhoea
What are the causes of bloody diarrhoea?
Chronic disease
Ulcerative colitis
Neoplasm
What are the major consequences of severe diarrhoea?
Decreased blood volume, metabolic acidosis / alkalosis
What are the consequences of excessive vomiting?
Increased salt and water loss, severe dehydration, circulatory problems, metabolic alkalosis, death
Why does excessive vomiting cause metabolic alkalosis?
Loss of gastric acid
What is lost in vomit?
Food, mucus with Na+ K+ Cl- and HCO3-, gastric acid, upper intestinal contents (inc bile), blood
What are the consequences of fluid loss from the GI tract?
Hypovolaemia, Haemoconcentration, dehydration, ionic imbalances and poor perfusion of tissues
What are the consequences of hypovolaemia?
Decreased venous return, arterial hypotension, myocardial dysfunction due to increased myocardial O2 demand
What does increased anaerobic metabolism lead to?
Acidosis
What does acidosis and myocardial dysfunction lead to?
Multi-organ failure
What are the physiological responses to diarrhoea?
Decreased plasma volume -> decreased venous pressure -> increased renal sympathetic nerve activity
What happens as a cause of the increased activity of renal sympathetic nerves?
Constriction of renal arterioles-> net glomerular filtration pressure -> decreased GFR -> decreased sodium and water secretion
What does severe sweating lead to?
Loss of hyperosmotic salt solution-> decreased plasma volume or increased plasma osmolarity
What does increased plasma osmolarity lead to?
Increased vasopressin -> decreased water excretion
What does decreased plasma volume lead to?
Either decreased GFR or increased aldosterone -> decreased sodium excretion
What are the steps in the RAAS cascade?
Dec plasma volume -> arterial pressure -> inc renin secretion -> inc plasma renin -> inc plasma angiotensin II -> inc aldosterone secretion
What 3 things lead to thirst?
Decreased plasma volume, increased plasma osmolarity, dry mouth or throat
What receptors does decreased plasma volume stimulate?
Baroreceptors
What receptors do increased plasma osmolarity stimulate?
Osmoreceptors
What regulates water loss?
Vasopressin (AKA ADH)
What does ADH do?
Stimulates thirst mechanism and activates the V2 receptor on the renal collecting ducts
What does the V2 receptor on renal collecting ducts do?
Inserts aquaporin-2 in the kidney collecting duct, which increases the water permeability of collecting ducts
What are the consequences of dehydration?
Nausea, headache, irrationality, cramps, temperature, dizziness
What are the effects of dehydration?
Imbalance of bloodstream electrolytes (decrease NaCl and potassium, increased calcium)
What is hypercalcaemia?
Increased calcium concentration
What does hypercalcaemia increase the risk of?
Kidney stones, kidney failure and arrhythmia
What are the symptoms of hypercalcaemia?
Nausea, vomiting, loss of appetite, constipation, abdominal pain, excessive thirst, fatigue, lethargy, joint pain, confusion
