COMMON ELECTROLYTE ABNORMALITIES IN EMERGENCY MEDICINETim Martin Dec 2016

AIMS AND OBJECTIVES

To discuss the investigation and diagnosis of common electrolyte abnormalities

Specifically focusing on hyponatraemia and a way to subdivide causes

To become familiar with emergency management of these conditions

SODIUMMain extracellular electrolyte

Distributed in the extracellular fluid which accounts for 20% total body weight and 33% total body water

Sodium concentrations mEq/L:

• Plasma 142

• Normal saline 154

• Hartmann’s 130

HYPONATRAEMIA

Serum sodium below 130mEq/L

Moderate symptoms < 130 : Headache, confusion, agitation

Severe symptoms < 120 : Intractable seizures, vomiting, coma

Mortality due to cerebral oedema and brainstem herniation

ASSESSMENT

Clinical fluid status

Urine and plasma osmolality

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

Urine sodium

61 year old male referred in from GP with Sodium 121 on routine blood tests

Repeat blood checked - sample as shown

What specific management does this patient require?

PSEUDOHYPONATRAEMIA

Occurs with severe hyperproteinaemia or hyperlipidaemia

Analytical error due to water displacement in sample

Some laboratories may be able to correct value

No treatment required for sodium, GP to review lipid profile please!

HYPEROSMOLAR HYPONATRAEMIA - >295

Similar phenomenon with hyperglycaemia

Corrected Sodium = Sodium + (Glucose - 5)/4

Hyponatraemia occurs due to osmotic diuresis including mannitol use

Correct with saline

HYPO-OSMOLAR HYPONATRAEMIA < 275

Hypovolaemic

Normovolaemic

Hypervolaemic

Hypovolaemic hyponatraemia - Loosing sodium in excess to water

PRE RENAL RENAL LOSS

Third space lossSweating/vomiting/diarrhoea

Addison’sDiuretic phase of renal failureRenal tubular acidosisThiazide diuretics

Normovolaemic hyponatraemia

URINE OSMOLALITY < SERUM OSMOLALITY URINE OSMOLALITY > SERUM OSMOLALITY

Tea and toast dietPsychogenic polydipsiaIatrogenicAmphetamine useExercise induced - hypotonic fluid ingestion

SIADH

SYNDROME OF INAPPROPRIATE ADH SECRETION

Precipitated by malignancy (ectopic ADH in small cell lung cancer), head injury/intracerebral infection, medications (cyclophosphamide, carbamazepine, SSRIs, amiodarone)

Hypotonic hyponatraemia

Urine osmolality > serum osmolality

Urine Sodium > 20mmol

Euvolaemia clinically

Normal adrenal, renal, cardiac, hepatic and thyroid function

Treatment includes:

Fluid restriction

Vasopressin antagonists eg tolvaptan

Demeclocycline and lithium

Hypervolaemic - Oedematous state

Congestive cardiac failure, liver cirrhosis, nephrotic syndrome

Treated with fluid restriction

In CCF consideration loop diuresis and or vasopressin antagonist eg tolvaptan

EMERGENCY MANAGEMENT HYPONATRAEMIA - SEIZURES

Target a sodium of 125

3ml/kg of 3% sodium chloride will raise sodium by 3

OR

100ml 3% sodium chloride over 10-15 minutes repeated unto a total of 300ml based on clinical symptoms

Limit sodium increase to 8mEq/L in first 24 hours

3 days post admission for hyponatraemia, corrected with hypertonic saline in intensive care patient stepped down to ward

Over next day develops dysarthria, dysphagia and a bulbar palsy

What complication has occurred?

2 weeks post total thyroidectomy a 60 year old man presents with cramping in hands and feet

Surgical note state 2 parathyroid glands spared

When blood pressure checked his left wrist painfully contracts

What is the most likely underlying problem?

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc

HYPOCALCAEMIAIonised calcium less than < 2

Most body calcium bound in bone

Ionised calcium (50%) is the active form compared with protein bound (40%) and complex calcium (10%)

PTH secreted in response to hypoclacaemia and is influenced by vitamin D and magnesium

PTH increases osteoclast activity as well as inducing calcium reabsorption in the kidney and vitamin D synthesis

CLINICAL SIGNS AND COMPLICATIONS

Chvostek sign and Trousseau sign

https://www.youtube.com/watch?v=6jFwxawwcbg

https://www.youtube.com/watch?v=2quH8gvtEAw

Spasms and cramps

Arrhythmias and Torsade de Pointes

Hallucinations and seizures

INVESTIGATIONS

Total and ionised calcium, PTH level, Vitamin D, Magnesium, Albumin level, Renal function and electrolytes

ECG - prolonged QTc, T wave changes resembling ischaemia

TREATMENT

Oral replacement 500 - 3000mg elemental calcium/day

IV calcium chloride (10ml of 10%) vs calcium gluconate (10-30ml of 10%)

Caution if concurrent digoxin use

75 year old lady presents short of breath

?COPD, crackles all over chest

? Ischaemic ECG

VBG shows a new creatinine of 750 and a potassium of 7.9

MANAGEMENT OF HYPERKALAEMIA

Cessation of nephrotoxic agents and potassium sparing diuretics

Enhanced elimination - fluids, diuretics, binding agents, dialysis

Membrane stabilisation with constant ECG monitoring - Calcium (gluconate vs chloride again)

Moving potassium intracellularly - Salbutamol nebulisers, 10 units ActRapid insulin in 50mls 50% dextrose, Sodium bicarbonate (if patient acidotic)

Tintinalli’s Emergency Medicine 8th edition. Tintinalli et al

Oxford Handbook Emergency Medicine 7th edition. Longmore et al

Textbook of Adult Emergency Medicine 4th edition. Cameron et al

Life in the Fast Lane