Electrolytes and Fluid Balance Flashcards
What is hypernatraemia often due to?
Water deficit
Consequences of hypernatraemia
- Cellular dehydration
- Vascular shear stress - bleeding and thrombosis
Symptoms of hypernatraemia
- Thirst
- Apathy
- Irritable
- Weakness
- Confusion
- Reduced conc
- Seizures
- Hyperreflexia
- Spasticity
- Coma
Causes of hypovolaemic hypernatraemia
Renal water loss:
* osmotic diuresis (via NG feeding),
* loop diuretics
* intrinsic renal disease
Non-renal water loss:
* excess sweating
* burns
* diarrhoea
* fistulas
Cause of euvolaemic hypernatraemia
Renal:
* Diabetes insipidus
* Hypodipsia (no thirst mechanism)
Extra renal:
* Insensible - skin, resp, stool
* Respiratory losses
Causes of hypervolaemic hypernatraemia
- Primary hyperaldosteronism
- Cushing syndrome
- Hypertonic dialysis
- Hypertonic sodium bicarbonate
- Sodium chloride tablets
Diabetes insipidus differential
Psychogenic polydipsia
Urine in diabetes insipidus
Dilute - osmolality of <300
Diabetes insipidus symptoms
- Polydipsia
- Polyuria
Na+ in diabetes insipidus
Not always hypernatraemic
If are will be euvolaemic
What are two types of diabetes insipidus?
Cranial - impaired release of ADH
Renal - impaired response/resistance to ADH
Causes of cranial diabetes insipidus
- Trauma/post op
- Cerebral sarcoid/TB
- Infection - meningitis/encephalitis
- Cerebral vasculitis (SLE/Wegener’s)
Causes of renal diabetes insipidus
- Congenitial
- Drugs (lithium, amphotericin, demeclocyline)
- Hypokalaemia
- Hypercalcaemia
- Tubulointerstitial disease
Treatment for hypernatreamia
Free water
Hyponatraemia symptoms
- Decreased perception
- Gait distubance
- Yawning
- Nausea
- Reversible ataxia
- Headache
- Apathy
- Confusion
- Seizures
- Coma
What causes psuedohyponatraemia?
Occurs with:
* high lipids
* myeloma
* hyperglycaemia
* uraemia
Investigations for hyponatraemia
- Plasma osmolality - if normal or raised then pseudohyponatraemia
- K+ and Mg levels - Hypokalaemia/hypomagnesia potentiates ADH release
- Urine sodium - if less than 20 non renal loss, >40 = SIADH
- TSH
- 9am cortisol
- Calcium
- Albumin
- Glucose
- LFT
- CT head/chest if suspect SIADH
How to assess whether hypovolaemic hyponatraemia is renal or non renal loss?
Urine Na+
If more than 20mmol/L - renal loss
If Less than 20 - non renal loss
Renal losses causing hypovolaemic hyponatraemia
- Diuretics - thiazides
- Osmotic diuresis (glucose, urea in recovering acute tubular necrosis)
- Addisons disease
Non-renla losses causing hypovolaemic hyponatraemia
- Diarrhoea
- Vomitting
- Sweating
- Third space losses - burns, bowel obstruction, pancreatitis
Treatment for hypovolaemic hyponatraemia
- IV fluids - 0.9% saline at 1-3ml/kg/hr
- Give K+ if needed
Causes of eurvolaemic hyponatraemia
- Hypothyroidism
- Primary polydipsia (if urine osmolality less than 100)
- Glucocorticoid deficiency - adrenal insifficiency
- SIADH
SIADH findings
- Low serum osmolality
- Concentrated urine - inapporpirate greater than 100
- Urine Na is more than 20
- Euvolaemia
- NOt on diuretics
- Elimination diagnosis - normal renal, thyroid, adrenal function
Management SIADH
- Fluid restrict less than 800ml per day
- PO sodium chloride
- Furosemide?
- Demeclocycline induces diabetes insipidus (reverse)
- Tolvaptan alternatively
Causes of hypervolaemic hyponatraemia
- CHF
- Nephrotic syndrome
- Liver cirrhosis
Treatment of hypervolaemic hyponatraemia
- Fluid restrict
- Consider furosemide
Risk of correcting hyponatraemia too fast
- Pontine/osmotic myelinosis
- Aim to correct less than 12mmol/L/day
general acute treatment of hyponatraemia
- If within 48hrs and symptomatic
- Give 3% hypertonic saline IV boluses +/- furosemide
Usual causes of acute hyponatraemia
- Iatrogenic
- Polydipsia
- Colonoscopy prep
- Ecstasy
Treatment for chronic hyponatraemia
If >48hrs and symptomatic
* hypertonic saline boluses if seizing
* Otherwise isotonic saline and furosemide - aim to correct 8mmol/L in 24hrs
* If chronic and asymptomatic - water restrict, stop offending drug, if dehydrated restore volume, if overloaded Na and water restriction and diuretics
Causes of hyperkalaemia
- CKD or K+ rich diet + CKD
- Drugs - ACEi, ARBs, Spironolactone, amiloride, NSAIDs, LMWH, heparin
- Hypoaldosteronism
- Addisons disease
- Acidosis
- Massive tissue damage - tumour lysis, burns, haemolysis, rhabdomyolysis
- Psuedohyperkalaemia - haemolysed blood sample
Rarer cause of hyperkalaemia
- Hyperkalaemic periodic paralysis
- Gordons syndrome
ECG changes in hyperkalaemia
- Tall tented T waves
- P wave flattened
- Prolonged QRS
- Slurred ST segment
- Asystole?
Treatment for hyperkalaemia steps
- Stabilise myocardium
- Shift K+ into cells
- Eliminate K+ from body
Stabilise myocardium treatment
10 mls of 10% calcium gluconate over 5-10 minutes
Shifting K+ back into cells treatment
- 10 units of IV fast acting insulin
- And IV glucose/dextrose 50% 50mls
- 500mls of 1.4% Sodium bicarbonate (only effective it pt acidotic)
- 5-10mg Salbutamol nebuliser
Eliminating K+ from body treatment
- Calcium resonium - 15-45g oral or rectal mixed with sorbitol or lactulose
- Furosemide 20-80mg depending on hydration
- Dialysis - if resistant to medical treatment
Symptoms of hypokalaemia
- Fatigue
- Confusion
- Proximal muscle weakness
- Paralysis
- Cardiac arrhtymias
- Worsened glucose control in diabetics
- Hypertension
Causes of hypokalaemia
- Pseudohypokalaemia - acute leukaemia
- Vomitting + diarrhoea
- Conns syndrome
- Cushing syndrome
- Diuretics
ECG changes in hypokalaemia
- Small T waves
- U wave (after T wave)
- Increased PR interval
Treatment for hypokalaemia
Replace magnesium
Oral K+ replacement
IV K+ replacement (usually in 0.9% saline avoid in dexrose as induces further hypokalaemia)
Insulin secreted when dextose given = K+ into cells
