Consequences of Fluid Loss

Question 1

What are the sites of water loss?

Answer 1

→Skin
→Respiratory passageways
→GIT
→Urinary tract
→Trauma
→Menstrual flow

Question 2

What is the daily NaCl intake?

Answer 2

→ 10.5g in food

Question 3

What 2 things cause water to be gained?

Answer 3

→ Drinking

→metabolism

Question 4

What is diarrhoea and what is the criteria for it?

Answer 4

→Increased frequency with increased volume and fluidity of feces
→>3 unformed stools per 24 hrs

Question 5

Why does diarrhoea occur?

Answer 5

→Failure of water absorption

→Increased secretion of both

Question 6

What are the causes of decreased absorption?

Answer 6

→Increased number of osmotic particles
→Increase in rate of flow of intestinal contents (deranged motility diarrhoea)
→Abnormal increase in secretions of GIT (secretory diarrhoea)

Question 7

What is the cause of osmotic diarrhoea?

Answer 7

→decreased absorption of electrolytes and nutrients
→Disaccharidase deficiency
→drug induced
→malabsorption of galactose

Question 8

What increases the rate of secretion in secretory diarrhoea?

Answer 8

→ACh, substance P, 5-HT and neurotension act via an increase in Ca2+

Question 9

What causes secretory diarrhoea?

Answer 9

→Excessive laxative use, defects in digestion and absorption (infections eg. Cholera)
→Enterotoxin stimulates adenylate cyclase increases cAMP causes Na+ and Cl- and water loss.

Question 10

What causes traveller’s diarrhoea?

Answer 10

→ Bacteria

Question 11

What causes chronic exudative diarrhoea?

Answer 11

→ Inflammatory bowel disease

Question 12

What causes deranged motility diarrhoea?

Answer 12

→ lack of absorption

→some agents promotes secretion as well as motility

Question 13

Why can GI stasis promote diarrhoea?

Answer 13

→stimulating bacterial growth

Question 14

What are the two parasites that cause diarrhoea?

Answer 14

→Entamoeba histolytica

→Giardia lamblia

Question 15

What condition does entamoeba cause and what is the treatment for it?

Answer 15

→asymptomatic dysentery

→ Metronidazole

Question 16

What does giardia cause?

Answer 16

→Steatorrhea and abdominal pain

→Maldigestion and malabsorption of lipids, CHOs, vitamin A, vitamin B12, folic acid

Question 17

What does dysentery cause?

Answer 17

→painful
→ bloody
→low volume diarrhoea

Question 18

What are the consequences of severe diarrhoea?

Answer 18

→loss of water, nutrients, Na+, K+ and HCO3-
→Decreased blood volume (hypovolaemia)
→Metabolic acidosis - due to loss of HCO3-

Question 19

What are the consequences of excessive vomiting?

Answer 19

→Increased salt and water loss
→Severe dehydration
→Circulatory problems
→Metabolic alkalosis - due to loss of gastric acid HCl
→Death

Question 20

What is lost in vomit?

Answer 20

→food
→ mucus
→Na+
→ K+
→ Cl-
→ HCO3-
→ gastric acid
→upper intestinal contents (bile)
→ blood

Question 21

What are the consequences of fluid loss in the GI tract?

Answer 21

→Hypovolaemia
→Haemoconcentration/polycythaemia (dehydration) →Increased RBC
→Dehydration
→Ionic imbalances : poor perfusion of tissues
→Malnutrition and increase in mortality

Question 22

What are the consequences of hypovolaemia?

Answer 22

→Decreased venous return
→Arterial hypotension
→Myocardial dysfunction due to increased myocardial oxygen demand but tissue perfusion is reduced
→Increased anaerobic metabolism → to acidosis
→Acidosis and myocardial dysfunction → multi organ failure

Question 23

What are the consequences of dehydration?

Answer 23

→Nausea
→headache
→ irrationality
→cramps
→increased temperature
→dizziness

Question 24

What is the bodys response to water loss?

Answer 24

→Cardiovascular adaptation
→Renal adaptation
→Behavioral and this stimulates fluid intake when possible

Question 25

What does the renal system do in response to hypovolaemia?

Answer 25

→Increased sodium and water loss due to diarrhoea →Plasma volume decreases →Venous volume decreases →Increased activity of the renal sympathetic nervous system →Increased constriction of afferent renal arterioles, it increases the vascular resistance which reduces renal blood flow (RBF), and it decreases the pressure downstream from the constriction →GFR decreases →Allows more time for reabsorption to occur if there is water present →Decreased Na+ and water secretion →Blood volume increases

Question 26

What are the cardiovascular effects of hypervolaemia?

Answer 26

→The decreased venous return →Decreases atrial pressure →Decreased ventricular end diastolic volume →Stroke volume reduces →Cardiac output reduces →Arterial blood pressure reduces →These effects stimulate the sympathetic nervous renal system

Question 27

What happens during severe sweating?

Answer 27

→Severe sweating decreases the osmotic salt solution →Plasma volume decreases →GFR decreases and plasma osmolarity increases →This stimulates osmoreceptors in the hypothalamus Increase the plasma vasopressin concentration (ADH) →Plasma aldosterone levels increase due to RAAS system →ADH inserts water channels within the collecting duct of the tubules and decreased water secretion occurs as it takes up more water

Question 28

Describe how decreased blood volume can cause the RAAS cascade

Answer 28

→Decreased plasma volume →Decreased GFR and decreased flow to Macula Densa → reduced NaCl concentration in macula densa →Decreases the arterial pressure →This has a direct effect on the stretch receptors →Stimulates an increase in renin secretion →Increased plasma renin generates angiotensin II →Plasma aldosterone secretions increase from adrenal cortex →Sodium reabsorption increases →Water reabsorption increases →Plasma volume increases

Question 29

What is the response to increased K+ concentration?

Answer 29

→A decrease in plasma volume →Increase plasma angiotensin II →Increased aldosterone from the renal cortex →Sodium reabsorption increases so sodium excretion decreases →Water is retained →Increased K+ excretion

Question 30

What can the RAAS cascade be triggered by?

Answer 30

→The RAAS cascade can be triggered by increased K+ concentration and decreased plasma volume.

Question 31

How does increased water reabsorption occur?

Answer 31

→Decreased plasma volume →Decreased venous, atrial and arterial blood pressure →These reflexes are mediated by cardiovascular baroreceptors →The plasma osmolarity increases →Osmoreceptors are stimulated →Hypothalamus causes the secretion of vasopressin →Plasma levels increase →Vasopressin stimulates its receptors on the collecting tubules and insert channels ‘aquaporin 2’ →Increased water reabsorption and decreased excretion

Question 32

How is thirst stimulated?

Answer 32

``` →Hyperosmolarity occurs →Decreases plasma volume →Baroreceptors are stimulated →Increases angiotensin II levels →This stimulates thirst →And stimulates ADH/vasopressin releas ```

Question 33

What does dehydration lead to?

Answer 33

→imbalance of electrolytes in the bloodstream (decreased NaCl and K+ but also increase in Ca2+)

Question 34

What does an increase in Ca2+ cause?

Answer 34

→ Hypercalcaemia

Question 35

What does hypercalcaemia cause?

Answer 35

→increased risk of kidney stone → kidney failure → dementia →arrhythmia

Question 36

What are the symptoms of hypercalcaemia?

Answer 36

``` →Nausea →Vomiting →Loss of appetite →Constipation →Abdominal pain →Excessive thirst →Fatigue,lethargy, muscle weakness →Joint pain and confusion ```

Question 37

What does ADH stimulate?

Answer 37

→Vasopressin (ADH) - stimulates thirst mechanism

Question 38

What leads to ADH release?

Answer 38

→Increased osmolarity of body fluids leads to ADH release

Question 39

How does ADH work?

Answer 39

→ADH activates the V2 receptors on the renal collecting ducts →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 40

What does the intake of plain H2O do?

Answer 40

→Intake of plain H2O leads to a decrease in osmolarity of the blood and interstitial fluid →This decreases the ADH secretion and the removal of water channels

Question 41

What happens if there are no water channels?

Answer 41

→decreased permeability of collecting ducts to water and increased water loss

Question 42

What are the 5 factors that regulate ADH release?

Answer 42

→Large decrease in blood volume (detected by baroreceptors) →2.Severe dehydration: under this condition, GFR decreases causing less H2O in urine →3.Hyperventilation: results in increased fluid loss (exhalation) →4.Vomiting/diarrhoea: causes increased fluid loss from GIT →5.Fever, heavy sweating, and burns cause large H2O loss

Question 43

What does the thirst center in the hypothalamus do?

Answer 43

→ Stimulate the desire to drink

Question 44

What does angiotensin II do?

Answer 44

→ Stimulate the release of aldosterone 2

Question 45

What does aldosterone do?

Answer 45

→ Promotes reabsorption of Na+, Cl- and H2O

Question 46

What does the Macula Densa do?

Answer 46

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

Question 47

What results from increased plasma potassium?

Answer 47

↑ aldosterone secretion from adrenal cortex ↑ plasma aldosterone ↑potassium secretion ↑ potassium excretion

Question 48

What are the effects of dehydration?

Answer 48

→Higher blood viscosity (reduced circulation) Higher blood pressure Blood clotting →Constipation, Acid reflux, Indigestion, Toxins accumulate, Reduced nutrients →Toxins accumulate Cannot be flushed Kidneys can be damaged →Skin with decreased turgor remains elevated after being pulled up and released

Question 49

What is oliguria?

Answer 49

→low urine