Fluid & Electrolytes

Question 1

What are the symptoms and signs of hypokalaemia?

Answer 1

MUSCLE –> weakness, myalgia
CARDIAC –> arrhythmia, palpitations, syncope
ECG progresses from T wave flattening –> T wave inversion + ST depression –> U waves appear –> U waves become larger than T waves.
Arrhythmias that can occur:
- Ectopic atrial and ventricular beats
- Sinus bradycardia
- Atrial tachycardia
- AV block
- VT
- VF
RENAL –> hypokalaemia leads to impaired urinary concentrating ability and eventually nephropathy –> polyuria, nephrogenic DI

Question 2

What causes hypokalaemia?

Answer 2

INADEQUATE INTAKE - needs to be extreme dietary insufficiency to cause hypokalaemia - e.g. anorexia nervosa
INTRACELLULAR SHIFT -
K shifts into cells is stimulated by insulin and adrenaline
LOSSES -
GIT: diarrhoea, vomiting
RENAL: K-wasting diuretics, Conn syndrome (excess aldosterone), tubular disease (Bartter and Gitelman syndromes), RTA
OTHER: burns, excessive sweating

Question 3

How would you treat hypokalaemia?

Answer 3

For mild hypoK (i.e. K 3.0-3.5)
Oral supplementation with KCl
For more severe hypoK (i.e. <3.0) or cannot tolerate oral intake –> IV KCl with normal saline + continuous ECG monitoring.
+ correct any other electrolyte disorders
+ correct any dehydration
+ investigate and treat underlying cause

Question 4

What are the symptoms and signs of hyperkalaemia?

Answer 4

MSK --> 
- Weakness (starts in lower limbs)
- Muscle cramps
CARDIAC -->
- Palpitations
- Arrhythmia
ECG changes:
First (usually at 5.5-6.5 mmol/L):
- Peaked T waves
- Prolonged PR interval
Then, as K continues to rise:
- Loss of P waves
- Widened QRS
- Sine wave pattern
- Asystole

Question 5

What causes hyperkalaemia?

Answer 5

The 2 main underlying causes are:

1. Impaired renal K excretion - could be due to:
   - CKD
   - AKI
   - Drugs: ACE-I, ARB, K-sparing diuretic
   - Aldosterone deficiency: Addison’s disease
2. Shifts of K out of cells
   - Cell breakdown: rhabdomyolysis, trauma
   - Drugs: B-blocker
   - Insulin deficiency: e.g. in DKA

Question 6

How would you treat hyperkalaemia?

Answer 6

CARDIAC MONITORING
IV ACCESS

• Prevent arrhythmia –> Give IV calcium
• Drive K into cells –> Give insulin + dextrose infusion, B2-agonist (nebulised albuterol)
• Remove K from body –> loop diuretic (if not volume depleted), intestinal K-binders, or dialysis
• Identify and treat cause

Question 7

What are the 2 main organ systems affected by K abnormalities?

Answer 7

Both HYPOKALAEMIA and HYPERKALAEMIA can cause:
MSK –> weakness, myalgia
CARDIAC –> arrhythmia, palpitations

Question 8

What is the daily recommended fluid intake?

Answer 8

Men = approx. 3.7L/day
Women = approx. 2.7L/day

Question 9

How would you assess volume/fluid status?

Answer 9

VITALS: tachycardia, orthostatic hypotension, hypotension
WEIGHT
URINE OUTPUT
SKIN & MUCOUS MEMBRANES:
Skin - temperature, turgor, capillary refill (normal = <2 sec)
Mucous membranes - dry or moist
JVP (height = cm above angle of sternum measured vertically. Considered elevated if > 3cm at 45 degrees)
OEDEMA/EFFUSION
Pulmonary oedema - SOB, crackles
Ascites
Peripheral oedema

Question 10

Fluid management strategies:
Hypovolemic shock?
Dehydration without shock?
NBM?
Ongoing losses?

Answer 10

HYPOVOLEMIC SHOCK - GIVE FLUID BOLUS
- UNSTABLE –> stat bolus of 1L 0.9% normal saline or bolus of 10-20mL/kg NS; watch response and repeat if necessary +/- vasopressors

DEHYDRATION W/O SHOCK - FLUID RESUSCITATION with CHALLENGE
Possible approach: fluid challenge = stat bolus of 250mL 0.9% normal saline; watch response –> if partially rectifies issue - repeat with further 250mL 0.9%NS stat then slow to 1L/8-10 hours.
OR, if only mildly dehydrated –>
1L NS over 4 hours, then
1L NS over 6 hours, then
1L NS over 8 hours –> then normal maintenance if required

NIL BY MOUTH –> MAINTENANCE FLUIDS
Possible approach: 3L/24 hours = 1L/8 hourly 0.9% normal saline.
If NBM for 24+ hours –> add 30mmol KCl to 2 of the bags of NS.
Alternatively, use Hartmann’s instead of NS –> reduced risk of metabolic acidosis. Still need to add 30mmol KCl to 2 of the bags.

ONGOING LOSSES –> MAINTENANCE + REPLACE ONGOING LOSSES.

Question 11

What causes hypercalcemia?

Answer 11

PTH-MEDIATED HYPERCA

• Primary hyperparathyroidism: hyperplasia, adenoma
• Tertiary hyperparathyroidism from CKD

NON-PTH-MEDIATED HYPERCA
- Malignancy:
From paraneoplastic production of PTHrP
From osteolytic metastases

• Granulomatous disease e.g. TB
  From activated mononuclear cells –> have hydroxylase activity –> increased active vitamin D
• Mediations:
  Thiazide - reduce renal calcium excretion
  Vitamin D excess
  Calcium supplementation
  Vitamin A excess
  Lithium - reduces renal calcium excretion and alters PTH secretion set point
  Milk-Alkali syndrome
• Thyrotoxicosis
  From T3/T4 –> stimulation of osteoclasts
• Immobilization –> stimulation of osteoclasts

Question 12

What are the symptoms and signs of hypercalcemia?

Answer 12

BONES, STONES, Abdominal GROANS, Psychic MOANS and CARDIAC

BONES:
Bone pain
Muscle weakness, especially proximal myopathy
Fracture

STONES:
Kidney stones

GROANS:
N&V
Anorexia
Constipation
PUD
Pancreatitis

MOANS:
Fatigue
Inability to concentrate
Depression
--> confusion --> coma

CARDIAC:
Bradycardia
1st degree AV block
Short QT
Arrhythmia

Question 13

How would you treat hypercalcaemia?

Answer 13

• Evaluate patient:
  DRSABCD, Vitals, LOC, stable/unstable
  Obtain ECG/ cardiac monitoring
  IV access
• Initial IX for underlying aetiology:
  FBC, EUC, CMP, ALP
  PTH, vitamin D
  Further IX depending on suspected cause.
• Appropriate hydration & diuresis
  (hypercalcemia may cause N&V + will dilute calcium)
  IV fluids with 0.9% NS - may require a lot of fluid e.g. 5-10L over 24 hours
  Loop diuretic if volume overloaded
• Avoid medications that aggravate hypercalcaemia (thiazide, lithium, vitamin D, calcium)
• Mild –> as above + monitor with serial CMP; arrange consultation e.g. endocrinology, nephrology
• Moderate/ Severe –> as above + consider:
  Rapid onset, short-term control of hyperca –> calcitonin
  Slower onset, long-term control of hyperca –> Bisphosphonates
  Dialysis
  Monitor - serial CMP, ECG