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PBLs FunMed > Week 8 - Mrs Mitchell > Flashcards

Week 8 - Mrs Mitchell Flashcards

1
Q

Define the general terms tachycardia.

You do not need to include parameters

A

Tachycardia - increased heart rate
Rapid heartbeat
Faster than normal

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2
Q

Define the general terms tachypnea.

You do not need to include parameters

A

Tachypnea - increased breathing rate

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3
Q

For a 70Kg man what is the amount of total body water and how is this calculated?

A

Body weight x 60%

70Kg x 60% = 42L

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4
Q

The concentration of what solute in the blood is important for the increased osmolarity when fluid volume decreases that stimulates the hypothalamus

A

Sodium

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5
Q

If Mrs Michel had been vomitting rather than having diarrhoea what acid base disturbance would she be most likely to have presented with and why?

A

Metabolic alkalosis (1 mark)

Vomiting leads to the loss of gastric secretions which are rich is hydrochloric acid. (1 mark)

Whenever a hydrogen ion is excreted a bicarbonate ion is gained. (1 mark) in the extracellular space leading to more bicarbonate in the body and therefore alkalosis. (1 mark)

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6
Q

Briefly explain how metabolic acidosis is compensated for both by the lungs and the kidneys? (2 marks)

A

Lungs: Lowering the PCO2 by hyperventilation

Kidney: Adds more H+ (or NH+) to the urine

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7
Q

What are some common symptoms of metabolic acidosis?

A

Headache

Decreased BP

Hyperkalemia (normally with quick onset)

Muscle twitching

Warm, flushed skin

Nausea, Vomiting, Diarrhoea

Changes in LOC (Confusion, drowsiness)

Kussmaul Respirations (compensatory hyperventilation)

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8
Q

What are some causes of Metabolic Acidosis?

A

Severe Diarrhoea
Renal Failure
Shock

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9
Q

What is metabolic acidosis?

A

Decrease ability of the kidney to excrete acid or conserve base

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10
Q

What pH should our body stay within?

A

7.35 and 7.45

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11
Q

Why is it important for the pH of the body to be within 7.35 and 7.45?

A

So enzymes do not denature

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12
Q

Mrs Mitchel is 72 years old and lives in a sheltered accommodation flat. She is admitted to hospital with a one week history of severe diarrhoea. She is weak, lethargic and clinically dehydrated. At the hospital a physician associate takes her blood pressure which is 100/60 mm Hg when lying down and this drops to 70/40 mm Hg when she is sitting up. Her radial pulse is weak, but there was tachycardia and tachypnea. There was reduced urine output.

List Mrs Mitchell’s presenting symptoms when admitted

A

72 years old

  • 1 week of severe diarrhoea
  • weak, lethargic, clinically dehydrated
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13
Q

Mrs Mitchel is 72 years old and lives in a sheltered accommodation flat. She is admitted to hospital with a one week history of severe diarrhoea. She is weak, lethargic and clinically dehydrated. At the hospital a physician associate takes her blood pressure which is 100/60 mm Hg when lying down and this drops to 70/40 mm Hg when she is sitting up. Her radial pulse is weak, but there was tachycardia and tachypnea. There was reduced urine output.

What did the physician’s associate find in the hospital?

A

BP

110/60mmHg (lying down)
70/40mmHg (sitting)

Tachycardia
Tachypnoea
Reduced urine output

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14
Q

What is the definition of tachycardia?

A

Increased heart rate >100bpm

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15
Q

What is the definition of tachypnoea?

A

Increased respiratory rate >20 per min

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16
Q

What is Ringer’s Lactate?

A

Solution for fluid and electrolyte replacement

Isotonic with blood
Lactate has alkaline effect which can help counteract the acidosis (metabolised into HC03-) in blood serum or in urine

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17
Q

What is Creatinine?

A

Waste molecule generated from metabolism of creatine in muscle

Filtered by kidneys and disposed in urine

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18
Q

What is the anion gap?

A

It checks the levels of acid in your blood

Measurement of the difference - or gap - between the negatively charged and positively charged electrolytes

If the anion gap is too high or too low, may be a sign of a disorder in your lungs, kidneys, other organ systems

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19
Q

Summarise the 4 different types of acid-base disturbance

A

Respiratory acidosis - retain CO2, usually because of hypoventilation (not breathing out enough)

Respiratory alkalosis - blow off too much CO2 hyperventilation (fast breathing)

Metabolic acidosis - retain H+ and excrete HCO3- (e.g. diarrhoea)

Metabolic alkalosis - retain HCO3- and excrete H+ (e.g. vomitting)

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20
Q

What acid base disturbance are you likely to have if you have been vomiting?

A

Metabolic alkalosis

Lose H+ ions in vomitting from the stomach (think about it stomach acid lost, lose H+ ions)

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21
Q

What acid base disturbance are you likely to have if you have been diarrhoea?

A

Metabolic acidosis

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22
Q

What acid base disturbance are you likely to have if you have been hyperventilating?

A

Respiratory alkalosis

Lose too much CO2, CO2 is acidic, so the blood becomes alkaline

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23
Q

What acid base disturbance are you likely to have if you have been hypoventilating?

A

Respiratory acidosis

Retain CO2 and so blood gets acidic

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24
Q

What do Mrs Mitchell’s blood work show when she first arrives?

pH - 7.11
pC02 - 16 (35-45mmHg)
HCO3- 5 (22-26mEq/L)

A

Hyperchloremic (High chloride levels - 118 (98-106)

pH is low 7.11

pCO2 is low - 16 (35-45)
compensatory hyperventilation

HCO3- is very low - 5 (22-26)

Hypokalaemia was very low but then was corrected 2.5 to 4.2 (3.5-5.5)

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25
Q

If you see a pH of 7.11 and a pCO2 of 16 (35-45mmHg) what does the patient have?

A

Acidosis

If pCO2 was high it would be respiratory acidosis

But because it is low you can see that the respiratory system was trying to counteract the low pH through hyperventilation so it is

Metabolic Acidosis

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26
Q

What does Mrs Mitchell’s blood work show after the Ringer’s solution?

pH - 7.49
pC02 - 20 (35-45mmHg)
HCO3- 15 (22-26mEq/L)

A

pH is 7.49

Alkalosis

pCO2 would be high in acidosis and low in alkalosis, which is in line with the high pH

So Respiratory alkalosis

Her body didn’t compensate yet for the Ringer’s solution

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27
Q

What are the 3 compensatory mechanisms that help handle changes in pH?

A
  1. Physiologic buffers - a reversible equation where a weak acid is broken down into a base salt or weak base

Examples:

  • Bicarbonate-carbonic acid buffer system
  • Intracellular protein buffers
  • Phosphate buffers in the bone
  1. Pulmonary compensation - changes in pCO2 driving pH
  2. Renal compensation - kidneys excrete or retain HCO3-
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28
Q

What are 3 examples of physiological buffers?

A

Bicarbonate-carbonic acid buffer system

Intracellular protein buffers

Phosphate buffers in the bone

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29
Q

How does pulmonary compensation work?

A

So when pH is low, increase ventilation gets rid of acidic CO2 and works to increase pH

When pH is high, there is a decrease in ventilatory effort, which increases pCO2 (retains acidic CO2) and lowers pH back towards normal

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30
Q

How does renal compensation work?

A

Starts 6 hours after sustained acidosis or alkalosis

In acidosis, kidneys excrete H+ and retains HCO3-

In alkalosis, kidneys excrete HCO3- and retain H+ in the form of organic acids

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31
Q

How long does it take for renal compensation to kick in?

A

6 hours after sustained acidosis or alkalosis

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32
Q

What are the final reserves for acidosis/alkalosis?

A

Bone

Bone can act as a buffer because it has a large reservoir of bicarbonate and phosphate and can buffer a significant acute acid load

If patients have low albumin levels, bone density due to malnutrition or chronic disease and anaemic patients, buffering ability is compromised

33
Q

Why does respiratory acidosis occur? Physiological mechanism

A

The only mechanism is alveolar hypoventilation

(pCO2 is above 45mmHg)
pH is less than 7.35

Alveolar hypoventilation can occur due to paralysis, brain stem disturbances, patient is sedated, elderly unwell and can’t move, respiratory paralysis (Guillain Barre)

Pulmonary emphysema, pulmonary oedema, COPD, bronchitis

34
Q

Why does respiratory alkalosis occur? Physiological mechanism

A

pH is high
pCO2 is low (breathed out)

Most common cause is due to increased alveolar ventilation (hyperventilation (anxious), hepatic disease, pregnancy, septicaemia, over ventilated in iCU)

Paper bag in hyperventilation helps to regulate CO2

35
Q

Why does metabolic acidosis occur? Physiological mechanism

A

Increase in amount of body acid (excess production of acids or excessive loss of bicarbonate, sodium and potassium)

Lactic acidosis

Diabetic ketoacidosis

Loss of bicarbonate through severe diarrhoea

Bicarbonate wasting through kidneys or GI tract

36
Q

What are some signs and symptoms of metabolic acidosis?

A

Headache

Lethargy

Anorexia

Deep, rapid respirations (Kussmaul)

Nausea

Diarrhoea

Abdominal discomfort (severe acidosis)

Coma and dangerous dysrhythmias

37
Q

What ions are involved in the anion gap?

A

(Na + K) - (Cl + HCO3)

As sodium is the most dominant cation can do

Na - (Cl + HCO3)

38
Q

What does a normal anion gap indicate in metabolic acidosis?

A

You have a very high level of Cl- to make up for the low HCO3- in the equation

Na - (Cl + HCO3)

39
Q

Why does metabolic alkalosis occur? Physiological mechanism

A

HCO3- is increased, usually due to an excessive loss of metabolic acids

Diuretics
Prolonged vomitting
Hyperaldosteronism
Cushing's syndrome
Exogenous steroids
40
Q

What are some signs and symptoms for metabolic alkalosis?

A

Cardiac dysrhythmias as a result of low K

Physical weakness

Muscle cramping

Hyperactive reflexes

Tetany

Convulsions

Confusion

41
Q

Reasons for an elevated anion gap

Don’t really need to know

A

Particular medications can cause it to be elevated

Methanol, metformin
Ethylene glycol
Toluene
Alcoholic ketoacidosis
Lactic acidosis

Aminoglycosides, other uremic agents

Cyanide, carbon monoxide

Isoniazid, iron

Diabetic ketoacidosis

Generalised seizure-producing toxins

ASA or other salicylate

Paraldehyde, phenformin

42
Q

Mrs Mitchell’s potassium levels were:

2.5 then 4.2 next day (3.5-5.5 mEq/L)

Though this is not the case for Mrs Mitchell..

How does Acidosis lead to Hyperkalemia?

A

Hyperkalemia is when potassium levels are higher than normal

H+ ions are taken into the cell from the extracellular fluid, and this is done by exchanging K+ ions to maintain electroneutrality

I.V potassium would still be given to these patients early in treatment despite the often elevated serum potassium levels because the cells themselves don’t have much K+ in them

43
Q

Mrs Mitchell’s sodium levels were:

137 on admission
137 the next day
(Normal - 135-147 mEq/L)

Explain this?

A

Normal sodium levels despite everything else changing

The kidneys try to keep sodium by exchanging it for excreted H+ or potassium

Sodium levels are kept quite constant

44
Q

What is saline responsive?

A

When you have metabolic alkalosis and you are deciding what treatment to give a patient based on their chloride ion levels in their urine

Saline responsive = less 15mmol/L

Nonsaline responsive = above 25mmol/L

45
Q

Metabolic acidosis and serum anion gap decreased due to?

A

Low albumin

46
Q

Metabolic acidosis and serum anion gap increased diagnosis

A

Lactic acidosis

or Ketoacidosis

47
Q

Metabolic acidosis and normal anion gap = ?

A

Hyperchloraemic metabolic acidosis

Her Chloride levels are in line with this:

118 on admission
114 next day
Normal = 98-106 mEq/L

48
Q

What are the three major causes of Hyperchloraemic metabolic acidosis and which one applies to Mrs Mitchell?

A

Renal tubular acidosis
Gastrointestinal losses
Chronic hypoventilation

GI losses applies to Mrs Mitchell

49
Q

In metabolic acidosis what are the following levels going to be like?

pH
H+
Primary disturbance (HCO3 or pCO2?)
Secondary response (HCO3 or pCO2?)

A

pH - Low

H+ - High

Primary disturbance - Low HCO3-

Secondary response - Low pCO2

50
Q

In metabolic alkalosis what are the following levels going to be like?

pH
H+
Primary disturbance (HCO3 or pCO2?)
Secondary response (HCO3 or pCO2?)

A

pH - High

H+ - Low

Primary disturbance - High HCO3-

Secondary response - High pCO2

51
Q

In respiratory acidosis what are the following levels going to be like?

pH
H+
Primary disturbance (HCO3 or pCO2?)
Secondary response (HCO3 or pCO2?)

A

pH - Low

H+ - High

Primary disturbance - High pCO2

Secondary response - High HCO3

52
Q

In respiratory alkalosis what are the following levels going to be like?

pH
H+
Primary disturbance (HCO3 or pCO2?)
Secondary response (HCO3 or pCO2?)

A

pH - High

H+ - Low

Primary disturbance - Low pCO2

Secondary response - Low HCO3

53
Q

Explain generally renal compensation in acidosis/alkalosis

A

So you secrete or reabsorb H+ or HCO3- in the collecting duct in the kidneys

So you urinate one of the ions out to compensate for what is going on in the body

Longer term solution

54
Q

What do the Type A intercalated cells in the kidney’s collecting duct do? In what conditions?

A

In acidosis

The Type A intercalated cells
Excretes: H+
Reabsorbs: HCO3- and K+

55
Q

What do the Type B intercalated cells in the kidney’s collecting duct do? In what conditions?

A

In alkalosis

The Type B intercalated cells
Excretes: HCO3- and K+
Reabsorbs: H+

56
Q

How many ml is Ringers fluid?

A

1L

57
Q

What treatment is Mrs Mitchell given?

A

IV Lactated Ringer’s fluid

Potassium supplementation

58
Q

What is going on in the next day after Mrs Mitchell is admitted?

Sodium 137 (135-147mEq/L)
       Next day: 137

Potassium 2.5 (3.5-5.5 mEq/L)
Next day: 4.2

Chloride 118 (98-106mEq/L)
       Next day: 114
Bicarbonate 5 (22-26mEq/L)
       Next day: 15

Creatinine 3.1 (0.6-1.1mg/dL women)
Next day: 2.0

Anion gap 10 (Less than 11mEq/L)
Next day: 8

pH 7.11 (7.35-7.45)
Next day: 7.49

pCO2 16 (35-45mmHg)
       Next day: 20
A

So she came in with metabolic acidosis

(Primary problem is HCO3- lost through diarrhoea)

So you can see the Bicarbonate is increasing :D

pCO2 is still much lower than predicted which means she is still hyperventilating

This results in respiratory alkalaemia

This is because the central chemoreceptors in the brain are slow to respond to the reversal in bicarbonate and so you still see compensatory hyperventilation

Bicarbonate will slowly enter the brain over 12-24 hours and central chemoreceptor inhibition will be progressively inhibited

pCO2 back to normal and normal breathing lags behind the increase in bicarbonate

59
Q

What is the key equation of buffering in the blood?

A

HCO3- + H+ > H2CO3 > CO2 + H20

60
Q

What 3 organs regulate fluid balance?

A

Brain
Adrenal glands
Kidneys

61
Q

What is the process that happens in the body when the fluid volume decreases?

A

Concentration of sodium increases in the blood (increased osmolarity)

Hypothalamus has osmoreceptors

Stimulates posterior pituitary to release ADH

ADH goes to the kidneys and they retain water (more concentrated urine, water returned to ECF)

Adrenal glands secrete aldosterone in response to low BP (retain fluid)

62
Q

How much of the Total Body Water is the Extracellular Fluid Volume?

A

1/3

63
Q

How much of the Total Body Water is the Intracellular Fluid Volume?

A

2/3

64
Q

What are the primary components of the extracellular fluid?

A 
Interstitial Fluid (3/4)
Plasma (1/4)
Transcellular Fluid (rest around 0.5L)
65
Q

What is the recommended daily intake of fluid?

A

2.5 L

66
Q

What makes up our intake of fluid?

A

Drink 1.6L
Food 0.7L
Metabolic water 0.2L

67
Q

What makes up our outtake of fluid?

A 
Feces (0.2L)
Expired air (0.3L)
Cutaneous transpirational (0.4L)
Sweat (0.1L)
Urine (1.5L)
68
Q

What is the daily output of fluid in L?

A

2.5L

69
Q

What are the two types of fluid that patients can get for rehydration?

A

Crystalloid fluids - water with electrolytes added to it (what Mrs Mitchell was given)

Colloid fluids - bigger molecules so they stay in blood vessels and water is drawn into the blood vessels (e.g. through trauma and scarring)

70
Q

Different reasons for dehydration?

A

(Sodium or water loss)

Vomitting and diarrhoea

Inadequate fluid intake

Low-sodium diet or no sodium intake

Diabetes insipidus (rare)

71
Q

Symptoms for dehydration

A 
Skin turgor
Hypovolemia
Tachycardia
Weak pulse
Postural hypotension
Confusion

Also: thirst, dry skin, sticky or dry mucous membranes, weight loss, concentrated urine

72
Q

What is a minimum urine output required for kidney function?

A

30ml per hour

73
Q

What is the definition of dehydration?

A

Lost 1% of body mass

74
Q

When does performance become impaired with water loss?

A

Loss 2% in body weight

75
Q

What are different effects of water loss on performance?

A

Loss 1% body weight - dehydration

Loss 2% body weight - impaired performance

Loss 4% body weight - capacity for muscular work reduced

Loss 6% body weight - heat exhaustion

Loss 8% body weight - hallucination

Loss 10% body weight - circulatory collapse and heat stroke

76
Q

ROME?

A

Respiratory Opposite
Metabolic Equal

In terms of the acidosis and alkalosis

77
Q

What does high creatinine indicate?

Mrs Mitchel
On admission = 3.1
Next day = 2.0
Normal = 0.6-1.1mg/dL (women)

A

Decreased Renal Function

78
Q

Properties of crystalloid fluids?

A

Saline plus electrolytes
Remain longer in ECF
Isotonic

PBLs FunMed (8 decks)

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