METABOLIC

Question 1

ABG of Renal Tubular Acidosis

Answer 1

metabolic acidosis associated with hyperchloraemia and a normal plasma anion gap (And normal renal function)

Question 2

ABG Anion Gap Calculation formula and RR

Answer 2

(sodium +potassium) - (bicarbonate +Chloride)
Normal range is 8-14mmol/L

Question 3

Causes of HAGMA (High Anion Gap Metabolic Acidosis (hint: ABCD)

Answer 3

Aspirin and other toxins (ethylene glycol, methanol)

Blood loss → lactic acidosis (type A), and type B lactic acidosis eg metformin

Chronic or acute renal failure
Excretion of nonvolatile acids is also impaired in renal failure, and this also leads to metabolic acidosis.

Diabetic ketoacidosis and other causes of ketoacidosis (starvation, alcoholic)
In diabetic ketoacidosis, when ketoacids, acetoacetic acid, and β-hydroxybutyric acid accumulate in the plasma.

Question 4

Causes of NAGMA (Normal Anion Gap Metabolic Acidosis)
hint: HARDUP or USEDCRAP

Answer 4

Expanded Causes (HARDUP)

Hyperchloraemia
Acetazolamide, Addison’s disease
Renal tubular acidosis
Diarrhoea, ileostomies, fistulae
Ureteroenterostomies
Pancreatoenterostomies

or USEDCRAP

Ureteroenterostomies
Small bowel fistula
Excess Chloride
Diarrhoea
Carbonic anhydrase inhibitors
Renal tubular acidosis
Addisson’s disease
Pancreatoenterostomies

Question 5

Causes of HAGMA (High Anion Gap metabolic acidosis).
Hint: CAT MUDPILES

Answer 5

Causes (CATMUDPILES)

CO, CN
Alcoholic ketoacidosis and starvation ketoacidosis
Toluene
Metformin, Methanol
Uremia
DKA
Pyroglutamic acidosis, paracetamol, phenformin, propylene glycol, paraladehyde
Iron, Isoniazid
Lactic acidosis
Ethylene glycol
Salicylates

Question 6

Treatment Targets for treating DKA

Answer 6

• Reduction of the blood ketone concentration by 0.5 mmol/L/hour
• Increase the venous bicarbonate by 3.0 mmol/L/hour
• Reduce capillary blood glucose by 3.0 mmol/L/hour (but no more than 6.0mmol/hr
• Maintain potassium between 4.0 and 5.5 mmol/L

If these targets are not achieved, then the fixed rate insulin should be increased by 1 unit/hr increments hourly until targets achieved.

In addition to this if the patients normally use exogenous basal insulin (i.e. Lantus) this should also be administered as normal.

Question 7

Diagnostic Criteria for DKA

Answer 7

1) Raised plasma glucose >11mmol/l or/and known
Diabetes Mellitus (capillary sample not sufficient)
N.B Glucose levels can be normal even with severe
DKA e.g pregnancy

2) Ketonaemia (Blood Ketones ≥ 3.0 mmol/L) or
significant Ketonuria > 2+ on urine ketostix.

3) Acidosis (Venous HCO3 ≤ 15mmol/l and/or pH <7.30)
with a raised anion gap

All three diagnostic criteria must be present to make
the diagnosis of DKA

Question 8

One or more of the following 9 indicate severe DKA

If the patient has any of these signs they should be immediately reviewed by medical SpR and discussed with the on call consultant physician and Critical Care for HDU monitoring.

Answer 8

1. Blood ketones over 6 mmol/L (although lower values between 3-6 can also occur in severe DKA)
2. Bicarbonate level below 5 mmol/L
3. Venous/arterial pH below 7.0
4. Hypokalaemia on admission (under 3.5 mmol/L)
5. GCS less than 12 or abnormal AVPU scale
6. Oxygen saturation below 92% on air (assuming normal baseline respiratory function)
7. Systolic BP below 90mmHg
8. Pulse over 100 or below 60bpm
9. Anion gap above 16 [Anion Gap = (Na+ + K+) – (Cl + HCO3)

Question 9

3 Main Aims of Fluid Replacement in DKA

Answer 9

1. Restoration of circulatory volume
2. Clearance of ketones
3. Correction of electrolyte imbalance

Exercise caution in the following groups:
* Young people aged 18-25 years
* Elderly
* Pregnant
* Heart or kidney failure
* Other serious co-morbidities
In these situations admission to a Level 2 / HDU facility should be considered. Fluids should be replaced cautiously

Question 10

Frequency of potassium monitoring in DKA

Answer 10

Trust Guidelines:
K+ replacement must be adjusted based on plasma K+
levels taken on admission, after 2h and after 6h (at least). (More frequent if potassium <3.0 or >6.0
(same frequency for U&E and VBG. BUT for glucose and ketones do hourly)

RCEM Guidelines:
Serum potassium level should be measured on arrival, at 60 minutes, 2 hours, and 2 hourly after that.

Question 11

Rate for Fixed rate insulin in DKA

Answer 11

Trust Guidelines:
- Start Insulin Infusion at 6 units per hour and continue to do so until acidosis corrected, i.e. venous bicarbonate >15 mmol/l or blood ketones < 0.6 mmol/l.

If the blood ketones are not falling at the expected rate (0.5 mmol/L/hr) or the blood glucose is not falling by at least 3 mmol/L/hr then increase the insulin infusion rate by 1 unit/hr increments upto 8 units/hr. Severely insulin resistant, obese or pregnant patients who are not responding appropriately within the first few hours may need higher rates (the equivalent of 0.1units/kg/hour) but this should not exceed 15units per hour.

RCEM:
- Infuse at a fixed rate of 0.1 unit/kg/hr (i.e. 7 ml/hr if weight is 70 kg)
- Only give a bolus (stat) dose of intramuscular insulin (0.1 unit/kg) if there is a delay in setting up a FRIII

Question 12

Define Resolution of DKA

Answer 12

Resolution of DKA is defined as ketones less than 0.6mmol/L and venous pH over 7.3.

NB: Do not rely on bicarbonate alone to assess the resolution of DKA at this point due to the possible hyperchloraemia secondary to high volumes of 0.9% sodium chloride solution. The hyperchloraemic acidosis will lower the bicarbonate and thus lead to difficulty in assessing whether the ketosis has resolved. The hyperchloraemic acidosis may cause renal vasoconstriction
and be a cause of oliguria.

Question 13

BLAST- overdose ammenable to haemofiltration

Answer 13

Barbituates
Lithium
Alcohol
Salicylates
Theophylline

Other indications: refractory hyperkalaemia, metabolic acidosis, uraemia and fluid overload.