Diagnosing impaired glucose tolerance
HbA1c 42-47mmol/L or Fasting plasma glucose 6.1-6.9mmol/L or OGTT (2hrs after 75g) 7.9-11.0mmol/L
Anion gap
Na + K - Cl - bicarb
NB: ketones are unmeasured anions, therefore DKA will have a raised anion gap
Osmolality
2(Na+K) + urea + glucose
How to distinguish between DKA and HONKC?
Calculate osmolality (raised in HONKC) and anion gap (raised in DKA due to ketones)
Management of hypoglycaemia
If alert - oral carbs
If drowsy but can swallow - sublingual glucose / hypostop
If unconscious, 100ml 20% glucose via large bore cannula
If persistent, 1mg IM / SC glucagon
Causes of high anion gap
'KULT' Ketones Uraemia Lactate Toxins
Causes of metabolic acidosis
Increased H+ production e.g. DKA, lactate
Decreased H+ excretion e.g. renal tubular acidosis
Bicarbonate loss e.g. fistulae
Causes of metabolic alkalosis
H+ losses e.g. vomiting
Hypokalaemia (perpetuates alkalosis and vice versa)
Ingestion of bicarbonate
Causes of respiratory acidosis
Hypoventilation
V/Q mismatch
Lung injury
Causes of respiratory alkalosis
Hyperventilation e.g. mechanical or anxiety
Low insulin + low c-peptide in the context of hypoglycaemia indicates what?
Appropriate response to hypoglycaemia e.g. malnutrition.
High insulin and high c-peptide in the context of hypoglycaemia indicates what?
Inappropriate response to hypoglycaemia e.g. insulinoma or islet cell hyperplasia
High insulin and low c-peptide in the context of hypoglycaemia indicates what?
Exogenous insulin administration
Calcium normal range
2.2-2.6mmol/L but should not vary from one day to the next in each person
3 forms of serum calcium
- 50% biologically active free ionised calcium
- 40% protein-bound (albumin)
- 10% complex (citrate / phosphate)
Symptoms of hypercalcaemia
Moans, bones, stones, groans, polyuria and polydypsia
Causes of hypercalcaemia
Primary hypercalcaemia (PTH zero)
- hypercalcaemia of malignancy: paraneoplastic due to PTHrP from small cell lung Ca, due to bony mets, or due to cytokines stimulating osteoclasts in multiple myeloma.
- sarcoidosis
- vitamin D excess
Secondary hypercalcaemia (PTH not zero)
- primary hyperparathyroidism (commonest cause of hypercalcaemia) e.g. adenoma, or MEN1
- familial hypocalciuric hypercalcaemia (benign!)
Management of hypercalcaemia
Medical emergency (Ca >3mmol/L)
Fluids
Treat underlying cause
Bisphosphonates if cause is cancer
Symptoms of hypocalcaemia
Neuromuscular excitability - Chvostek`s and Trousseau`s signs Hyperreflexia Seizures Stridor Wide QT
Causes of hypocalcaemia
Low PTH
- Iatrogenic (thyroidectomy)
- Autoimmune hypoPTH
- Congenital abscence (DiGeorge)
- HypoMg
High PTH (secondary hyperparathyroidism)
- vitamin D deficiency / osteomalacia
- CKD
- PTH resistance
Secondary hypocalcaemia
Diagnosis of osteoporosis
T-score (mean of young healthy population) on DEXA scan:
Osteoporosis
T score vs. Z score (DEXA)
T score = SD from mean of young healthy population (useful for fracture risk)
Z score = SD from mean of age-matched controls (useful to identify accelerated bone loss in younger pts)
Diagnosing diabetes
HbA1c >/=48mmol/L (>/=6.5%) or Fasting plasma glucose >/=7mmol/L or OGTT (2hrs after 75g) >/=11.1mmol/L
