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sem 2 Liver and GI > Consequences of fluid Loss from the GI Tract > Flashcards

Consequences of fluid Loss from the GI Tract Flashcards

1
Q

what is meant by “Insensible water loss”

A

water loss by transepidermal diffusion, so it is water that evaporates through the skin and respiratory tract

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2
Q

what do water intake and output do?

A

balance each other out

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3
Q

excretion (loss) of water and salts is usually small, but when is it large?

A

diarrhoea
sweating
vomiting
haemorrhage

losing a lot of electrolytes which can cause problems

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4
Q

kidneys can do what?

A

alter excretion to match gain with loss

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5
Q

why would you decrease salt intake?

A

to prevent hypotension

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6
Q

intake of salt should be?

A

similar to the output

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7
Q

list ways in which water, electrolytes and sodium chloride are lost

A 
Defecation, diarrhoea
Vomiting
Urination
Ventilation
Sweating
Menstruation
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8
Q

list ways in which water, electrolytes and sodium chloride are gained

A

Drinking

Metabolic (what we eat)

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9
Q

define diarrhoea

A

characterized by both an increase in frequency and weight of the stool

↑ frequency, with ↑ volume and fluidity of faeces

Greater than 3 unformed stools per 24hrs

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10
Q

give 2 reasons why diarrhoea occurs

A
  • Failure of water absorption (Enterocytes lose ability to reabsorb as Toxins can bind)
  • ↑ secretion (HCO3-, enzymes, Na+, due to crypt cell hyperplasia)

OR both

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11
Q

Causes of decreased absorption

A

↑ number of osmotic particles (osmotic diarrhoea)

↑ rate of flow of intestinal contents (deranged motility diarrhoea)

Abnormal increase in secretions of GIT (secretory diarrhoea)

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12
Q

Osmotic diarrhoea

A

occurs when too much water is drawn into the bowels

if a person drinks a solution with excessive sugar or excessive salt (an osmotically rich solution), this can draw water from the body into the bowel and cause osmotic diarrhoea

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13
Q

what can the build up of bacteria cause

A

de-conjugation of bile salts, which can cause osmotic or secretory diarrhoea

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14
Q

Deranged motility diarrhoea

A

the motility of the small intestine increases, meaning there is reduced time for reabsorption

this means that the volume of the fecal content will increase

some agents may promote secretion as well as motility

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15
Q

Secretory diarrhoea

A

increased secretion of ions from the crypt cells

very common in cholera

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16
Q

what can cause osmotic diarrhoea?

A

Disaccharidase deficiency (can be due to carbohydrate intolerance)

e. g. lactose intolerance
- due to lack of the brush border enzyme lactase, lactose cannot be broken down into Glucose and Galactose

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17
Q

what can cause secretory diarrhoea?

A

ACh, substance P, 5-HT and neurotensin act via ↑[Ca2+] (intracellular calcium levels) to increase rate of intestinal secretion

Excessive laxative use, defects in digestion and absorption, infections (cholera)

cholera survives acidic conditions of gut

enterotoxin stimulates adenylate cyclase, which increases cAMP levels leading to Na+ loss, Cl- loss (from crypt cells) and therefore uncontrolled water loss

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18
Q

what are crypts?

A

grooves between the villi (small fingerlike projections that line the small intestine and promote nutrient absorption)

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19
Q

how do you combat losing water, electrolytes and glucose

A

oral rehydration therapy so you can replace it all

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20
Q

what can inflammatory bowels disease cause?

A

chronic exudative diarrhoea, where you are producing a lot of fluid

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21
Q

why might GI stasis promote diarrhoea?

A

stimulating bacterial overgrowth, which could deconjugate the conjugated bile acids

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22
Q

what is dysentery?

A

painful, bloody, low volume diarrhoea

extreme urge to go but very little comes out

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23
Q

what is giardia, and what does it cause

A

a parasitic cause of diarrhoea

causes steatorrhoea and abdominal pain, maldigestion & malabsorption of lipids, CHOs, vit A, vit B12, folic acid.

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24
Q

causes of bloody diarrhoea?

A
  • Chronic disease
  • Ulcerative colitis
  • Neoplasm
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25
Q

neoplasm

A

a new and abnormal growth of tissue in a part of the body, especially as a characteristic of cancer

26
Q

major consequences of severe diarrhoea

A

excessive loss of water, nutrients, Na+, K+ and HCO3- causes:

↓ blood volume (hypovolaemia)

metabolic acidosis – due to loss of HCO3-

27
Q

what can volume depletion lead to?

A

acidosis/alkalosis

28
Q

consequences of excessive vomiting

A

↑ salt and water loss

Severe dehydration

Circulatory problems – as volume of water has dropped

Metabolic alkalosis – due to loss of gastric acid (HCl)

Death

29
Q

What is lost in vomit?

A

Food

Mucus with Na+, K+, Cl-, HCO3-

Gastric acid

Upper intestinal contents (incl. bile)

Blood

30
Q

consequence of vomiting up lots of gastric acid?

A

can affect the lining of the oesophagus

31
Q

consequences of fluid loss from GI Tract

A

Hypovolaemia (decreased blood volume)

Haemoconcentration/polycythaemia leads to an increase in [RBC]

Dehydration

Ionic imbalances (due to loss of electrolytes), poor perfusion of tissues

Malnutrition and ↑ mortality

32
Q

what does polycythaemia/erythrocytosis mean?

A

having a high concentration of red blood cells in your blood

-makes the blood thicker and less able to travel through blood vesselsand organs. many of the symptoms of polycythaemia are caused by this sluggish flow of blood

33
Q

Signs and symptoms of polycythaemia

A
  • headache
  • blurred vision
  • red skin, particularly in the face, hands and feet
  • tiredness
  • high BP
  • dizziness
  • abdomen discomfort
  • bleeding problems
  • Gout-which can cause joint pain, stiffness and swelling
  • Itchy skin- the result of white blood cells releasing histamine
34
Q

Consequences of hypovolaemia:

A

↓ venous return

Arterial hypotension

Myocardial dysfunction due to ↑ myocardial oxygen demand, but reduced tissue perfusion

tissues are not able to respire properly in terms of aerobic respiration, so ↑ anaerobic metabolism → acidosis

Acidosis and myocardial dysfunction → multi-organ failure

35
Q

Haemoconcentration

A

Decrease in the volume of plasma in relation to the number of red blood cells; increase in the concentration of red blood cells in the circulating blood

36
Q

how does hypovolaemia come about?

A
  • haemorrhage
  • insufficient fluid intake
  • excessive fluid losses from diarrhea or vomiting
  • can often be induced by excessive use of diuretics
37
Q

indicators of hypovolaemia

A
  • absence of perspiration
  • light headedness
  • dark coloured urine
38
Q

consequences of dehydration on the organs

A

brain has priority
-takes water from rest of the body when you’re thirsty

kidneys get overloaded
-toxins accumulate and cannot be flushed. kidneys can be damaged

heart has to work harder
-higher blood viscosity. higher blood pressure. blood clotting

39
Q

consequences of dehydration

A

heat shock, headache,
fainting

digestive problems

  • constipation
  • acid reflux
  • indigestion
  • toxins accumulate
  • reduced nutrients

reduced skin turgor

confusion and lack of mental awareness

Dryness of the lips

There may be reflux

40
Q

why does dehydration cause confusion and lack of mental awareness?

A

because the brain cells have shrunk

41
Q

why might dehydration cause reflux?

A

the secretions that come from the pancreas to neutralise the duodenal chyme need large amounts of water

reduced water means there is reduces neutralisation, meaning chyme builds up, pressure builds up and it can then be refluxed out

42
Q

physiological response to water loss (look at powerpoint)

A

Increased sodium and water loss

volume of plasma goes down, venous return goes down

So, corrective mechanisms will be put in place to correct this

increased activity of renal sympathetic nerves, causing constriction of renal arterioles

decreased net glomerular filtration pressure allowing more time for reabsorption

GFR goes down meaning there is decreased sodium and water secretion

sodium and water blood volume increases

43
Q

Water loss by sweating and physiological adaptations to it

A

severe sweating means there is a loss of hypo-osmotic salt solution which causes a:

  1. decrease in plasma volume, so sodium excretion is reduced by increasing plasma aldosterone and vasopressin, and decreasing GFR
  2. increase in plasma osmolarity, so H2O excretion is reduced by increasing plasma vasopressin (ADH)
44
Q

Response of the body to the consequences hypovolaemia: RAAS cascade

look at notes

A

The RAAS cascade can happen as a result of low sodium, or high potassium

Macula densa senses
[NaCl]fluid passing it; ↓[NaCl] causes
↑renin release
↓ resistance to blood flow in the afferent arterioles via vasodilation →normal GFR

increased renin means increased angiotensin II means increased aldosterone

45
Q

Physiologic response to the consequences of hypovolaemia with increased potassium concentration

A

increased plasma potassium causes increase aldosterone secretion into the plasma, leading to increased potassium secretion and excretion

46
Q

Physiologic response to the consequences of hypovolaemia

A
  • osmolarity goes up in plasma
  • osmoreceptors in hypothalamus are stimulated
  • secretion of vasopressin from posterior pituitary
  • vasopressin will stimulate receptors on the collecting tubules and insert channels on the collecting tubules called aquaporin 2
  • increased water reabsorption
47
Q

Physiologic response to the consequences of hypovolaemia - THIRST

look at notes

A

The osmoreceptor input is very important

Feeling thirst drives us to seek water and ingest it is stimulated by lower extracellular volume and higher plasma osmolarity

increase in plasma osmolarity is detected by osmoreceptors

also, dryness of the mouth and throat causes thirst which can be relieved by moistening them. decrease in plasma volume detected by baroreceptors which increase angiotensin II

48
Q

how is over-rehydration stopped?

A

Metering of water intake by GI tract

49
Q

what can dehydration do to calcium levels?

A

increase them

50
Q

what is hypercalcaemia, and what are the risks associated with it?

A

↑ [Ca2+]

↑ risk of kidney stones, kidney failure, dementia and arrhythmia

51
Q

Symptoms of hypercalcaemia

A 
If mild= asymptomatic
Nausea
Vomiting
Loss of appetite
Constipation
Abdominal pain 
Excessive thirst

Fatigue, lethargy, muscle weakness
Joint pain, confusion

52
Q

What regulates water loss?

A

Vasopressin (antidiuretic hormone, ADH)

ADH stimulates thirst mechanism

53
Q

Increased osmolarity of body fluids causes what?

A

ADH release

54
Q

How does ADH work?

A

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

55
Q

intake of plain H2O leads to what?

A

a ↓ in osmolarity of blood and interstitial fluid

this decreases ADH secretion and the removal of the water channels

56
Q

what is osmolarity?

A

how concentrated a solution is, i.e. the total number of solute particles per litre of solution

57
Q

Factors that regulate ADH release

A

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

58
Q

what happens when there is an intake of copious amounts of water

A

results in high BP, which causes increased GFR and increased H2O in urine

59
Q

how in ANP/ANF involved in H2O balance?

A

Stimulates natriuresis - increased excretion of Na+, Cl- and H2O

Increased loss of water in urine

60
Q

factors involved in H2O balance?

look at notes

A

thirst centre in hypothalamus

ANP/ANF

ATII

Aldoesterone

ADH

sem 2 Liver and GI (11 decks)

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