GUT- Consequences of Fluid Loss from the GI Tract Flashcards
what is the total body water intake in an adult individual
Total - 2550ml
made from liquids - 1200ml
food- 1000ml
metabolically produced 350ml
what is the total body output in an adult individual
total - 2550ml
made from
sweat - 50ml
faeces- 100ml
urine- 1500ml
what are the sites of water loss
skin, respiratory passages, GIT tract, Urinary tract, Trauma, Menstrual flow
what is the daily intake of NaCl
food - 10.5 g
what is the daily output of NaCl
sweat - 0.25g
faeces- 0.25g
urine 10g - varies considerable
total - 10.5 g
what alters excretion of NaCl
kidneys
outline ways which fluid is lost from the body
defecation - diarrhoea vomiting urination ventilation sweating menstruation
outline ways in which fluids are gained by the body
drinking
metabolism
what is diarrhoea
increase in frequency and increase in fluidity of faeces
>3 unformed stools in 24 hours
change in bowel movement
how does diarrhoea occur
via the failure of water absorption
increased secretion of water
what are causes of decreased water absorption
osmotic diarrhoea
deranged motility of diarrhoea
secretory diarrhoea
what is osmotic diarrhoea
increase in number of osmotic particles
decreases absorption of electrolytes and nutrients
disaccharides deficiency - drug induced, malabsorption of galactose, bloating, nausea, watery diarrhoea
what is deranged motility diarrhoea
increased rate of flow of intestinal contents
lack of absorption of nutrients; some agents may promote secretion as well as motility
GI stasis may promote diarrhoea by stimulating bacterial overgrowth
what is secretory diarrhoea
abnormal increase in secretions of GIT
ACh and substrate P act via increasing calcium concentration to increase rate of intestinal secretion
excessive laxative use; defects in digestion and absorption ; infection
what are the causes of bloody diarrhoea
chronic disease
ulcerative colitis
neoplasm
what is lost in vomiting
food, mucus, Na,K,Cl, biacronate, gastric acid
upper intestinal contents
blood
what are the consequences of severe diarrhoea
decrease in blood volume (hypovolemia)
metabolic acidosis - due to loss of bicarbonate
volume depletion could lead to acidosis / alkalosis
what are the consequences of excessive vomiting
increased salt and water loss severe dehydration circulatory problems metabolic alkalosis (due to loss of gastric acid) death
what are the consequences of fluid loss from GI tract
hypovolemia
haemoconcentration / polycythaemia (dehydration) - increased RBC concentration
dehydration
ionic imbalances; poor perfusion of tissues
malnutrition and increased mortality
what are the consequences of hypovolaemia
decrease venous return
arterial hypotension
myocardial dysfunction due to increased myocardial oxygen demand but tissue perfusion is reduced
increased anaerobic metabolism –> acidosis - build up of lactic acid
acidosis and myocardial dysfunction –> multi organ failure
outline cardiovascular adaptations to water loss
increased Na and H2O loss due to diarrhoea
decreased plasma volume
decreased venous pressure
adaptations: decreased venous return decreased atrial pressure decreased ventricular end diastolic volume decreased stroke volume decreased cardiac output decreased arterial blood pressure
outline renal adaptions to water loss
increased Na and H2O loss due to diarrhoea
decreased plasma volume
decreased venous pressure
increased activity of renal sympathetic nerves
increased constriction of renal arterioles
decreased net glomerular filtration pressure
decreased GFR
decreased Na and water secretions
how does the renal system promote decreased sodium and water excretion
increase in plasma aldosterone causes a decrease in sodium excretion
increase is plasma vasopressin causes a decrease in water secretion
how does the RAAS cascade respond the hypovolemia
a decrease in plasma volume causes a decrease in arterial pressure
this causes an increase in renin secretion - therefore an increase in plasma renin
causing an increase in plasma angiotensin II
causing an increase in aldosterone secretion
causing an increase in sodium reabsorption
how does ADH cause water reabsorption
an increase in osmolarity of body fluids causes ADH release
this activates V2 receptors on the renal collecting ducts of the kidney
this increases the permeability of the collecting ducts to water and results in a concentrated urine production
how does drinking water affect water reabsoprtion
intake of water causes a decrease in osmolarity of blood and intersitital fluid - decreases ADH secretion and the removal of water channels so collecting duct permeability to water is decreased
what factors regulate ADH release
large decrease in blood volume (detected by baroreceptors)
severe dehydration
hyperventilation - results in increased fluid loss
vomiting
diarrhoea
fever - heavy sweating
what factors control the thirst response
decreased plasma volume detected by baroreceptors - increase angiotensin II which triggers thirst further
increased plasma osmolarity detected by osmoreceptors
dry mouth/ throat
the metering of water intake by the GI tract decreases the thirst response- avoids over hydration
what are the consequences of dehydration
nausea headaches irrationality cramps increased temperature dizziness
effects of dehydration
imbalance of electrolytes in the blood stream - decrease in Na and K+ but increase in Ca
what risks does hypercalcaemia have
risk of kidney stones, kidney failure, arrythmia
what are the symptoms of hypercalcaemia
nausea, vomiting, constipation, abdominal pain, fatigue, lethargy, joint pain, confusion
