Chem path Flashcards
Units for osmolality
Mmol/kg
Units for osmolarity
mmol/l
Osmolarity calculation
2(Na+K) + urea + glucose
Normal range for osmolality
275 - 295 mmol/kg
Normal range sodium
135 - 145 mmol/l
Symptoms of hyponatraemia, starting with symptoms experienced as Na falls
Nausea and vomiting (
What can happen if you correct hyponatraemia too fast? What rate should you aim for?
Central pontine myelinosis (pseudobulbar palsy, paraperesis, locked-in syndrome)
Rate: 1mmol/l per hour
Two reasons why hyponatraemia may occur post-surgery?
Over hydration with hypotonic IV fluids
Transient increase in ADH due to stress of surgery.
Causes of SIADH
Malignancy - small cell lung cancer, pancreas, prostate, lymphoma
CNS disorders - meningoencephalitis, haemorrhage, abscess
Chest - TB, Pneumonia, abscess
Drugs - opiates, SSRIs, carbamazepine
Symptoms of hypernatraemia
Thirst Confusion Seizures and ataxia Coma Death
Three types of ECF
Intravascular
Transcellular
Interstitial
What is the test used in diagnosing Diabetes Insipidus? There are four potential type of results from the test, name them and what you would expect to see.
8hr fluid deprivation test
Normal: Urine concentration >600mOsmol/kg
Primary polydipsia: Urine concentrates >400-600mOsmol/kg
Cranial DI: urine concentrates only after giving desmopressin
Nephrogenic DI: zero concentration urine after desmopressin
What is the normal range for potassium? (with units)
3.5-5.5mmol/l
Four causes of hypokalaemia?
GI loss Renal loss (hyperaldosteronism, excess cortisol) Redistribution into the cells (insulin, beta-agonists, alkalosis) Rare causes (tutbular acidosis type 1 & 2)
Normal pH range
7.35-7.45
normal CO2 range
4.7-6kPa
normal bicarbonate range
22-30mmol/l
normal O2 range
10-13kPa
Anion gap calculation
(Na + K) - (Cl + HCO3)
Normal anion gap range
14-18 mmol/l
Causes of a metabolic acidosis with elevated anion gap
mnemonic KULT
Ketoacidosis (DKA, alcoholic, starvation)
Uraemia (renal failure)
Lactic acidosis
Toxins ( ethylene glycol, methanol, paraldehyde, salicylate)
Osmolar gap calculation
Osmolality (measured) - Osmolarity (calculated)
What is the normal osmolar gap?
Normal range of AST/ALT
What causes AST/ALT (the aminotransferases) to rise?
Death of hepatocytes
What condition causes an AST:ALT of 2:1
Alcoholic liver disease
What condition causes an AST:ALT of
Viral liver disease
What is the normal range of ALP?
30-150iu/L
In what conditions does ALP rise?
cholestasis (intra/extrahepatic)
Bone disease
Pregnancy
What is the normal range of GGT
15-85iu/L men
5-55iu/l women
What causes GGT to rise?
chronic alcohol use
bile duct disease
metastases
Acute intermittent porphyria is characterised by what enzyme? Is it raised or low?
Porphobilinogen (PBG) deaminase deficiency
What are the symptoms of acute intermittent porphyria?
Abdominal pain Seizures Psych disturbances N+V Tachycardia Muscle weakness NO cutaneous manifestations
What are the 6 Ps of Acute Intermittent Porphyria?
Porphobilinogen deaminase deficiency Pain in abdomen Psychological symptoms (anxiety, hallucinations) Peripheral neuropathy (patchy numbness) Pee abnormality (dark urine) Precipitated by drugs (barbiturates, oral contraceptives)
How to diagnose acute intermittent porphyria
aminolevulinic acid (ALA) and porphobilinogen (PBG) in the urine
What are the three aspects to interpret in the combined pituitary function test?
Insulin Tolerance Test
Thyrotrophin Releasing Hormone Test
Gonadotrophin Releasing Hormone Test
What is an adequate cortisol response in an Insulin Tolerance test?
Rise above 550 nmol/l =normal
400-550 =impaired
Rise of less than 170 = Cushing’s syndrome
What is an adequate growth hormone response in an Insulin tolerance test?
greater than 6 mcg/l
In primary hypothalamic disease which would be greater in a TRH test? 30min or 60min TSH levels?
60min
What hormones are produced from the anterior pituitary?
ADH and Oxytocin
In diabetes insipidus, which of the following are raised or low: urine osmolality; serum osmolality.
Urine osmolality is decreased
Serum osmolality is raised
Normal range for TSH?
0.33-4.5 mu/L
Normal range for free T4?
10.2-22.0 pmol/L
normal range of free T3?
3.2-6.5 pmol/L
Raised TSH, Low T4
Hypothyroidism
Raised TSH, normal T4
Treated hypothyroidism/subclinical hypothyroidism
Raised TSH, raised T4
TSH secreting tumour or thyroid hormone resistance