consequences of fluid loss from GI tract Flashcards
what is the average water gains and loss in adults ?
Intake (volumes)
Liquids: 1200ml
Food: 1000ml
Metabolically produced: 350ml
Total: 2550ml
Output (volumes)
“Insensible water loss” (skin and lungs): 900ml
Sweat: 50ml
Faeces: 100
Urine: 1500
Total: 2550ml
what are the sites of water loss ?
- Skin
- Respiratory passageways
- GIT
- Urinary tract
- Menstrual flow
what are the average NaCl intakes and loss ?
Intake (grams):
Food: 10.5g
Output (grams):
Sweat: 0.25g
Faeces: 0.25g
Urine: 10.00g – varies considerably
Total output: 10.5g
- Kidneys can alter excretion to match gain with loss
what is diarrhea and how it it caused ?
- ↑ frequency, with ↑ volume and fluidity of faeces
- > 3 unformed stools per 24hrs
- Change in bowel movement
caused by:
* Failure of water absorption
* ↑ secretion of water
* or both of above
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)
what is osmotic diarrhea ?
- Decreased absorption of electrolytes and nutrients
- Disaccharidase deficiency (disaccharide deficiency/malabsorption), drug-induced, malabsorption of galactose); bloating, nausea, watery diarrhoea
what is secretory diarrhea ?
- 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 is deranged motility diarrhea ?
- lack of absorption; some agents may promote secretion as well as motility
- GI stasis may promote diarrhoea by stimulating bacterial overgrowth
what are the parasitic causes of diarrhea ?
- Entamoeba histolytica → asymptomatic or amoebic dysentery
- Gradual in onset → systemic symptoms (anorexia, headache)
- Metronidazole - treatment
- Giardia → steatorrhoea and abdominal pain; maldigestion & malabsorption of lipids, CHOs, vit A, vit B12, folic acid
- Metronidazole or tinidazole - treatment
what are the major consequences of severe diarrhea ?
- 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
- Volume depletion could lead to acidosis/alkalosis
what are the consequences of severe vomiting ?
- ↑ salt and water loss
- Severe dehydration
- Circulatory problems
- Metabolic alkalosis – due to loss of gastric acid (HCl)
- Death
What is lost in vomit?
Food
Mucus with Na+, K+, Cl-, HCO3-
Gastric acid
Upper intestinal contents (incl. bile)
Blood
what are the consequences of fluid loss from the GI tract ?
- Hypovolaemia
- Haemoconcentration/polycythaemia (dehydration) =↑[RBC]
- Dehydration
- Ionic imbalances; poor perfusion of tissues
- Malnutrition and ↑ mortality
what are the consequences of hypovolemia ?
- ↓ venous return
- Arterial hypotension
- Myocardial dysfunction due to ↑ myocardial oxygen * demand; tissue perfusion is reduced
- ↑ anaerobic metabolism → acidosis
- Acidosis and myocardial dysfunction → multi-organ failure
what is the bodies response to water loss ?
- Cardiovascular adaptation
- Renal adaptation
- Behavioural, and this stimulates fluid intake when possible to do so
describe the Physiologic response to the consequences of hypovolemia: Diarrhea
what are the adaptations that occur via water loss by sweating ?
what are the responses to the body due to hypovolemia ? - raas cascade
what are the Physiologic response to the consequences of hypovolaemia with increased potassium concentration ?
what is the Physiologic response to the consequences of hypovolaemia - THIRST
what regulates water loss ?
- Vasopressin (antidiuretic hormone, ADH)
- ADH stimulates thirst mechanism
- Increased osmolarity of body fluids → ADH release
how does ADH work ?
- 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
- 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 in the urine
what are the factors that regulate ADH release ?
- Large decrease in blood volume (detected by baroreceptors)*
- Severe dehydration: under this condition, GFR decreases causing less H2O in urine*
- Hyperventilation: results in increased fluid loss (exhalation)*
- Vomiting/diarrhoea: causes increased fluid loss from GIT*
- 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 about
- Intake of copious amounts of water: results in high BP which causes increased GFR and increased H2O in urine
give a summary of factors that maintain body H2O balance
what are the consequences of dehydration ?
what is dehydration and what effects does it have ?
- Dehydration →imbalance of electrolytes in the bloodstream (↓ NaCl and K+), but it also ↑[Ca2+]
- ↑ [Ca2+] → hypercalcaemia
- Hypercalcaemia → ↑ risk of kidney stones, kidney failure, and arrhythmia.
Symptoms of hypercalcaemia:
If mild= asymptomatic
Nausea
Vomiting
Loss of appetite
Constipation
Abdominal pain
Excessive thirst
Fatigue, lethargy, muscle weakness
Joint pain, confusion
What is the most likely consequence for a patient experiencing protracted vomiting due to food poisoning?
c) Metabolic alkalosis
Prolonged vomiting can lead to loss of stomach acid, resulting in metabolic alkalosis.
How does ADH mediate its water regulating properties?
c) Inserts aquaporin-2 into the collecting duct of kidneys which improves the reabsorption of water
ADH enhances water reabsorption in the kidneys by facilitating the insertion of aquaporins.
What triggers physiological responses to hypovolaemia?
Reduced plasma volume and increased plasma potassium levels
These factors initiate mechanisms to restore normal physiological states.
What is the end result of the physiological control system in response to hypovolaemia?
Fluid/blood volume is increased and potassium level is reduced
The system corrects low plasma volume and high plasma potassium without causing fluid overload.
Which mediator increases the secretion of aldosterone from the adrenal cortex?
Angiotensin II
Angiotensin II plays a crucial role in regulating blood pressure and fluid balance.
List two consequences of fluid loss from the gastrointestinal tract.
- Dehydration
- Ionic imbalances
These consequences can lead to serious health issues if not addressed.
List two consequences of hypovolaemia.
- Multi-organ failure
- Decreased venous return
Hypovolaemia can lead to severe complications and requires prompt treatment.
Fill in the blank: The physiological consequence A of hypovolaemia is _______.
↑ aldosterone secretion
Aldosterone secretion is prompted to help retain sodium and water.
Fill in the blank: The physiological consequence B of hypovolaemia is _______.
↑ sodium reabsorption
Sodium reabsorption helps to counteract the effects of fluid loss.
True or False: Increased potassium secretion is a consequence of hypovolaemia.
True
This is part of the body’s response to restore electrolyte balance.
Fill in the blank: The physiological consequence D of hypovolaemia is _______.
↓ sodium excretion
This mechanism increases sodium retention, contributing to blood volume restoration.
Fill in the blank: The physiological consequence E of hypovolaemia is _______.
↑ potassium excretion
This helps in correcting elevated potassium levels in the blood.
