Module 6.1-6.3

Question 1

What are the 4 pressures that determines fluid movement?

Answer 1

• Capillary Hydrostatic Pressure: force of blood in capillary pushing outwards into interstitium
• Interstitial Fluid Hydrostatic Pressure: force of fluid in interstitium pushing into capillary
• Capillary Osmotic Pressure: force exerted by proteins (albumin) pulling fluid into capillary
• Interstitial Fluid Osmotic Pressure: force exerted by proteins pulling fluid into interstitial space

Question 2

What is the equation for effective filtration pressure?

Answer 2

P(effective)= [CHP+IFOP] - [COP-IFHP]

Question 3

What is the effect of all four pressures?

Answer 3

• To move fluid out of capillary at arterial end and to suck fluid into capillary at venous end
• Excess fluid and proteins are collected by lymph. system and returned to venous circulation

Question 4

What is an oedema?

Answer 4

• 1+ body compartments become inundated with fluid
• CM. local area of swelling, inc. body weight, pain on area or impaired function
• Managed by leg elevation, compression stocking, albumin infusion if there is liver failure
• Diuretics

Question 5

What is intracellular oedema?

Answer 5

• Fluid accumulation in cells due to hypertonic cells or ineffective pumping of Na/K+ out of cells

Question 6

What are the bodily mechanisms of extracellular oedema?

Answer 6

• Hydrostatic pressure: force pushing plasma into interstitial space
• Oncotic pressure: osmotic pull exerted by plasma to draw fluid back to capillaries
• Lymphatic drainage: removes excess fluid and proteins from interstitial space

Question 7

What are the causes of EC. oedema?

Answer 7

1. Inc. plasma leaving capillaries due to inflam. or inc. Hydrostatic pressure
2. Dec. plasma returning to capillaries due to dec. oncotic pressure
3. Dec, fluid drainage due to lymphatic obstruction or inc. tissue constituents

Question 8

What is hypovolemic shock?

Answer 8

• Loss of blood/plasma in circulation
• Causes can include inc. inflammatory response or peritonitis due to fluid shift out of space (third spacing), or dehydration

Question 9

WHat are CM of Hypovolemic shock?

Answer 9

• CM are thirst, agitation initally due to SNS stimulation, Pale skin, tachycardia and oliguria
• Vasoconstriction shunts blood from surface to vital areas affecting blood flow and causing lethargy
• Inc. hypoxaemia, respiratory alkalosis and metabolic acidosis progresses

Question 10

What is third spacing?

Answer 10

• Fluid shifting out of blood into a body cavity/tissue where it is no longer available as circulating, causing hypovolemia and fluid excess in interstitial space
• Caused by peritonitis, inflam/ infect. of peritoneal membranes, ascites or burns

Question 11

What is dehydration?

Answer 11

• Fluid intake falls below fluid output, affecting the intracellular compartment where most body water is located
• What can be shunted from EC compartment to compensate but can also cause hypovolaemia

Question 12

What is the purpose of sodium ions?

Answer 12

• To determine osmolarity of ECF
• To contribute to membrane potential of excitable cells
• Normal range is 135-145 mmol/L

Question 13

What is the purpose of Potassium ions?

Answer 13

• highly concentrated in IC compartment
• involved in IC ion balance, acid/base balance and muscle function
• Hypokalaemia is serums levels less than 2 mmol/L
• Hyperkalaemia is serum levels of K+ greater than 5 mmol/L, more easily excited muscles

Question 14

What is the purpose of Calcium ion?

Answer 14

• Blood coag, neurotransmission, muscle contraction, cardiac conduction and bone/teeth forming
• Hypocalcaemia is serum level’s below 2.25 mmol/L
• Hypercalcaemia is serum levels above 2.75 mmol/L

Question 15

What is the purpose of Chloride ions?

Answer 15

• Major EC anion with serum levels of 98/106 mmol/L, follow Na due to charge (high Na = high Cl)
• Assist in acid-base balance
• H2CO3 bind with metabolic acids so Cl ions diffuse out fo RBC into serum to maintain -ve ions in blood, or if Cl dec. HCO3 will leave erythrocytes to maintain neutrality (Cl- shift)

Question 16

WHat are the body’s four systems that maintain serum pH?

Answer 16

• Na HCO3-H2CO3 acid
• Phosphate
• Haemoglobin
• Protein

Question 17

What is the bicarbonate buffer system equation?

Answer 17

CO2 + H2O <-> H2CO3 <-> HCO3 + H

Question 18

What is the MoA of the Bicarb. buffering system?

Answer 18

1. Co2 and H2O produced by cells during metabolism which reacts and forms carbonic acid
2. Carbonic acid dissociates into H+ ions and bicarbonate
3. Regulated by lungs excreting CO2 and kidneys regulate and excrete bicarbonate

Question 19

What are the normal values of the blood?

Answer 19

pH: 7.35-7.45
PaCO2: 35-45 mmHg
HCO3: 22-26 mmol/L
PaO2: 75-100 mmHg