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chemical pathology > Diabetes Cases > Flashcards

Diabetes Cases Flashcards

1
Q

diabetes is confirmed by

A

fasting plasma glucose >7.0mM

2 hour plasma glucose in a GTT of >11.1mM

HbA1c > 6.5% (48mmol/mol) - not useful if in people with end-stage chronic kidney disease

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2
Q

CASE 1
- 16-year-old unconscious
- Acutely unwell a few days
- Vomiting
- Breathlessness
Data
- pH: 6.85
- PCO2: 2.3kPa (N: 4-5)
- PO2: 15kPa

QUESTION 1: What is the acid/base abnormality?

A

Low PH
low PCO2

  • Metabolic acidosis
    LOW pH= ACIDOSIS – this means there are excess H+ ion >> this will lead to a LOW CO2

NOTE: If you have a LOW CO2, this means there is LOW bicarbonate

HCO3- + H+ >>> CO2 + H20

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3
Q

More Data

  • Na: 145
  • K: 5
  • U: 10
  • pH: 6.85
  • Glucose: 25

What is the osmolality?

A

osmolality = (cations (Na, K) + anions (Cl, HCO3) + urea+ glucose)

But Since anions = cations, this can be reduced to: 2 x (Na + K) + Urea + Glucose

= 335

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4
Q

define Anion Gap + equation + what is normal anion gap

A

Cations (Na/ K) = Anions (Cl, HCO3, others)

‘Others’ are known as the anion gap

ANION GAP= Na+ + K+ - (Cl- + HCO3-)

A NORMAL anion gap is ~ 18mM

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5
Q

acidosis + high anion gap means:

A

there are extra ‘other’ anions in the patient’s blood e.g. KETONES/Lactate

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6
Q

acidosis + normal anion gap means:

A

this is due to the a HIGH Cl-

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7
Q

commonest causes of metabolic acidosis

A

o DKA -1st
o Lactic acidosis – 2nd (e.g. sepsis)
o if neither of these consider poisons

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8
Q
  • 19-year-old known to have T1DM for several years presents unconscious
  • Results:
    o pH: 7.65
    o PCO2: 2.8kPa
    o HCO3: 24mM (NORMAL)
    o PO2: 15kPa

What is the acid-base abnormality

A

Respiratory Alkalosis
HIGH pH: ALKALOSIS, LOW CO2: respiratory

indicates: primary hyperventilation

Treatment is to help slow their breathing to bring them back to normality

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9
Q
  • 19-year-old known to have T1DM for several years presents unconscious
  • Results:
    o pH: 7.65
    o PCO2: 2.8kPa
    o HCO3: 24mM (NORMAL)
    o PO2: 15kPa

Na: 140, K: 4.0, HCO3: 24, Cl: 100, Glucose: 1.3mM

What is the anion gap? + What is the diagnosis?

A

ANION GAP= Na+ + K+ - (Cl- + HCO3-) = 20mM

Respiratory Alkalosis

  • Anxiety caused by hypoglycaemia because they are diabetic patient

but if they were non diabetic: Anxiety may just lead to respiratory alkalosis in a non-diabetic patient- COMMON CAUSE

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10
Q

what can cause respiratory alkalosis commonly + how do you treat this

A

Anxiety

To treat: give them a BROWN BAG to rebreathe in- CO2 goes up, patient calms down. Slow down the breathing.

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11
Q

what happens to calcium when PH goes up

A

When pH goes UP, the ionised calcium FALLS.

When the pH goes up, the calcium sticks more avidly to the albumin. So the ionised calcium falls

*so alkalosis is associtaed iwth both hypoklaaemia and hypocalcaemia

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12
Q

why do people hyperventilating get hypocalcaemic signs

A

hyperventilating: Respiratory alkalosis so PH goes up

When the pH goes up, the calcium sticks more avidly to the albumin. So the ionised calcium falls = hypocalcaemic signs

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13
Q

CASE 3
-60-year-old man presents unconscious to casualty, with a history of polyuria and polydipsia.

Investigations reveal:
- Na: 160, K: 6.0, U: 50, pH: 7.30, Glucose: 60

QUESTION 6: What is the osmolality? + what is the diagnosis

A

osmolality = 2 x (Na + K) + Urea + Glucose

2 x (160 + 6) + 50 + 60 = 332 + 110 = 442mosm/kg (very high osmolality)

undiagnosed DM >>> hyperosmolar non-ketotic coma (HONKC)/hyperosmolar state (HHS

(PH is not too bad (not very acidotic) so unlikely to be DKA + long-standing DM will not present with DKA

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14
Q

treatment for
hyperosmolar non-ketotic coma (HONKC.)/hyperosmolar state (HHS)

A

-0.9% NORMAL saline = 0.9g/ 100ml of NaCl.

GIVE THIS SLOWLY: 500ml over 1 hour + reassess and continue until visible JVP (euovolaemic)

If patient is VERY dehydrated can give 1L of saline over 1 hour - like in this case

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15
Q

what is the worry about giving too much fluid quickly

A

can lead to cerebral and pulmonary oedema, especially in the elderly

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16
Q

how do you treat hyperglycaemia in T1DM and T2DM

A

T1DM management involves giving lots of insulin

T2DM management involves very slow infusion of fluids + observe + then give insulin >> do not want to precipitate pulmonary oedema

17
Q

what happens if you give insulin first in hyperosmolar state in T2DM:

A

circulatory collapse: insulin will pump whatever is in the circulation into the cell. So, the BP will fall.

must give fluids first and then give insulin as they are insulin resistant

18
Q

CASE 4

  • 59-year-old man known to have T2DM on a good diet and metformin presents to casualty unconscious
  • Urine negative for ketones
  • Na: 140, K: 4.0, U: 4.0, pH: 7.1, Glucose: 4.0
  • PCO2: 1.3kPa, Cl: 90, HCO3: 4.0

What is the osmolality? + anion gap + What is the acid/ base abnormality?

A
  • 2 x (140 + 4) + 4 + 4 = 296- high osmolality
  • 140 + 4 – 90 – 4= 50- large excess of anions
  • Metabolic acidosis
19
Q

EXCESS ANIONS- examples

A
  • KETOSIS (excess ketones)
  • Methane: Meth drinks
  • Ethanol: Ethylene glycol + Other organic solvents
  • Lactate: Sepsis + Metformin overdose
20
Q

in which 2 scenarios can excessive metformin causes lactic acidosis and how does metformin cause lactic acidosis

A

Lactate accumulates in large excess of metformin >> lactic acidosis: Metformin inhibits hepatic gluconeogenesis- gluconeogenesis (the conversion of lactic acid to glucose in the liver)

Metformin overdose + occurs in people

  • who have acute renal failure
  • suicide attempt

excess lactic acid is normally excreted by the kidneys, but in renal failure the kidneys cannot handle the excess lactic acid which is why people with renal failure are affected

21
Q

Definition: T2DM

A

T2DM: Fasting glucose ≥ 7.0mM

Fasting plasma glucose:

  • FPG: ≤ 6.0mM is NORMAL
  • IFG: 6.1-6.9mM
  • DM: ≥ 7.0mM

GTT: plasma glucose ≥ 11.1mM at 2 hours

Impaired glucose tolerance on GTT: 7.8-11.0 at 2 hours

22
Q

acid base abnormality in DKA + effect of Kausmaal respiration + what should be done

A
  • If a patient has DKA, then the PCO2 + pH will FALL – the acid will go up leading to metabolic acidosis (without compensation)

If he starts to get Kausmaal respiration (hyperventilate), the pH will start to normalise as the CO2 will start to drop more

Give this patient insulin to help turn off the acid production

23
Q
  • If a patient has acute severe asthma and has an acute asthmatic attack what acid base abnormality will be seen
A

there will be a rapid rise in CO2 leading to acute respiratory acidosis and hypoxia

24
Q

define compensation in acid base abnormalities

A

Compensation is IMPROVING the pH by WORSENING the CO2 (either VERY low or high)

Metabolic acidosis- over-breathe to compensate

Chronic respiratory acidosis + acute respiratory acidosis- not breathing enough and compensate by retaining HCO3

25
Q

DKA vs HHS

A

DKA more common in T1DM, prominent PH acidosis

HHS- more common in T2DM, extremely high osmolarity

26
Q

DKA criteria

A

pH < 7.3

Plasma Glucose >11mM

Blood Ketones>3mM (2+ in urine).

27
Q

Sx and precipitants of DKA

A

Symptoms: confusion, Kussmaul breathing, abdominal pain, nausea, vomiting

  • Precipitants include infection, surgery, missed insulin doses, trauma
  • Management
28
Q

Management of DKA

A
29
Q

Criteria for HHS

A

pH > 7.3,

Osmolarity > 320mOsm,

Blood Glucose > 30mM

30
Q

What duration does HHS develop over?

A

Few days

31
Q

Management of HHS

A

A to E approach

Fluid replacement FIRST to prevent low BP : 0.9% saline over 1 hr

Then IV insulin >> Only if >1 mmol/L ketones

0.05u/Kg/hr fixed rate

Monitoring
§ Serial U+Es and glucose readings

32
Q

differences between HHS and DKA

A
  • DKA- T1DM and HHS - T2DM
  • HHS- higher osmolaity, higher glucose, high PH
  • DKA- lower PH + presence of ketones >3
33
Q

good way to remember acid base status

A
34
Q

when do you need 2 abnormal readings for diagnosis of diabetes

A

In asymptomatic patients, 2 abnormal readings are required for diagnosis.

35
Q

Conditions where HbA1c may not be used for diagnosis:

A

haemoglobinopathies

haemolytic anaemia

untreated iron deficiency anaemia

suspected gestational diabetes

children

HIV

chronic kidney disease

people taking medication that may cause hyperglycaemia (for example corticosteroids)

chemical pathology (22 decks)

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