Consequences of fluid Loss from the GI Tract

Question 1

what is meant by “Insensible water loss”

Answer 1

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

Question 2

what do water intake and output do?

Answer 2

balance each other out

Question 3

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

Answer 3

diarrhoea
sweating
vomiting
haemorrhage

losing a lot of electrolytes which can cause problems

Question 4

kidneys can do what?

Answer 4

alter excretion to match gain with loss

Question 5

why would you decrease salt intake?

Answer 5

to prevent hypotension

Question 6

intake of salt should be?

Answer 6

similar to the output

Question 7

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

Answer 7

Defecation, diarrhoea
Vomiting
Urination
Ventilation
Sweating
Menstruation

Question 8

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

Answer 8

Drinking

Metabolic (what we eat)

Question 9

define diarrhoea

Answer 9

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

Question 10

give 2 reasons why diarrhoea occurs

Answer 10

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

OR both

Question 11

Causes of decreased absorption

Answer 11

↑ number of osmotic particles (osmotic diarrhoea)

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

Abnormal increase in secretions of GIT (secretory diarrhoea)

Question 12

Osmotic diarrhoea

Answer 12

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

Question 13

what can the build up of bacteria cause

Answer 13

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

Question 14

Deranged motility diarrhoea

Answer 14

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

Question 15

Secretory diarrhoea

Answer 15

increased secretion of ions from the crypt cells

very common in cholera

Question 16

what can cause osmotic diarrhoea?

Answer 16

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

Question 17

what can cause secretory diarrhoea?

Answer 17

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

Question 18

what are crypts?

Answer 18

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

Question 19

how do you combat losing water, electrolytes and glucose

Answer 19

oral rehydration therapy so you can replace it all

Question 20

what can inflammatory bowels disease cause?

Answer 20

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

Question 21

why might GI stasis promote diarrhoea?

Answer 21

stimulating bacterial overgrowth, which could deconjugate the conjugated bile acids

Question 22

what is dysentery?

Answer 22

painful, bloody, low volume diarrhoea

extreme urge to go but very little comes out

Question 23

what is giardia, and what does it cause

Answer 23

a parasitic cause of diarrhoea

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

Question 24

causes of bloody diarrhoea?

Answer 24

• Chronic disease
• Ulcerative colitis
• Neoplasm

Question 25

neoplasm

Answer 25

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

Question 26

major consequences of severe diarrhoea

Answer 26

excessive loss of water, nutrients, Na+, K+ and HCO3- causes: ↓ blood volume (hypovolaemia) metabolic acidosis – due to loss of HCO3-

Question 27

what can volume depletion lead to?

Answer 27

acidosis/alkalosis

Question 28

consequences of excessive vomiting

Answer 28

↑ salt and water loss Severe dehydration Circulatory problems – as volume of water has dropped Metabolic alkalosis – due to loss of gastric acid (HCl) Death

Question 29

What is lost in vomit?

Answer 29

Food Mucus with Na+, K+, Cl-, HCO3- Gastric acid Upper intestinal contents (incl. bile) Blood

Question 30

consequence of vomiting up lots of gastric acid?

Answer 30

can affect the lining of the oesophagus

Question 31

consequences of fluid loss from GI Tract

Answer 31

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

Question 32

what does polycythaemia/erythrocytosis mean?

Answer 32

having a high concentration of red blood cells in your blood -makes the blood thicker and less able to travel through blood vessels and organs. many of the symptoms of polycythaemia are caused by this sluggish flow of blood

Question 33

Signs and symptoms of polycythaemia

Answer 33

- 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 

Question 34

Consequences of hypovolaemia:

Answer 34

↓ 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

Question 35

Haemoconcentration

Answer 35

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

Question 36

how does hypovolaemia come about?

Answer 36

- haemorrhage - insufficient fluid intake - excessive fluid losses from diarrhea or vomiting - can often be induced by excessive use of diuretics

Question 37

indicators of hypovolaemia

Answer 37

- absence of perspiration - light headedness - dark coloured urine

Question 38

consequences of dehydration on the organs

Answer 38

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

Question 39

consequences of dehydration

Answer 39

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

Question 40

why does dehydration cause confusion and lack of mental awareness?

Answer 40

because the brain cells have shrunk

Question 41

why might dehydration cause reflux?

Answer 41

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

Question 42

physiological response to water loss (look at powerpoint)

Answer 42

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

Question 43

Water loss by sweating and physiological adaptations to it

Answer 43

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 1. increase in plasma osmolarity, so H2O excretion is reduced by increasing plasma vasopressin (ADH)

Question 44

Response of the body to the consequences hypovolaemia: RAAS cascade look at notes

Answer 44

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

Question 45

Physiologic response to the consequences of hypovolaemia with increased potassium concentration

Answer 45

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

Question 46

Physiologic response to the consequences of hypovolaemia

Answer 46

- 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

Question 47

Physiologic response to the consequences of hypovolaemia - THIRST look at notes

Answer 47

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

Question 48

how is over-rehydration stopped?

Answer 48

Metering of water intake by GI tract

Question 49

what can dehydration do to calcium levels?

Answer 49

increase them

Question 50

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

Answer 50

↑ [Ca2+] ↑ risk of kidney stones, kidney failure, dementia and arrhythmia

Question 51

Symptoms of hypercalcaemia

Answer 51

``` If mild= asymptomatic Nausea Vomiting Loss of appetite Constipation Abdominal pain Excessive thirst ``` Fatigue, lethargy, muscle weakness Joint pain, confusion

Question 52

What regulates water loss?

Answer 52

Vasopressin (antidiuretic hormone, ADH) | ADH stimulates thirst mechanism

Question 53

Increased osmolarity of body fluids causes what?

Answer 53

ADH release

Question 54

How does ADH work?

Answer 54

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

Question 55

intake of plain H2O leads to what?

Answer 55

a ↓ in osmolarity of blood and interstitial fluid this decreases ADH secretion and the removal of the water channels

Question 56

what is osmolarity?

Answer 56

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

Question 57

Factors that regulate ADH release

Answer 57

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

Question 58

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

Answer 58

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

Question 59

how in ANP/ANF involved in H2O balance?

Answer 59

Stimulates natriuresis - increased excretion of Na+, Cl- and H2O Increased loss of water in urine

Question 60

factors involved in H2O balance? look at notes

Answer 60

thirst centre in hypothalamus ANP/ANF ATII Aldoesterone ADH