Introduction

• Normal range: 0.7 – 0.9 mmol/L

Fast correction

• IV MgSO4 2.47 g in 100 mL NS over 1 hour
• Repeat Mg 1 hour post correction (not a fixed rule)

“Dr., this patient X has hypokalaemia, potassium 2.5. Can I fast correct with IV KCl 2g stat?”

Introduction

• Normal range of serum potassium: 3.5 – 5.1 mmol/L
• Severity of hypokalaemia:
  • Mild: 3.1 – 3.5 mmol/L -> oral potassium supplement, then repeat RP tomorrow
  • Moderate: 2.5 – 3 mmol/L -> ECG + consider fast correction with IV KCl, then repeat serum potassium after 1 hour
    • ±IV KCl maintenance in drip / oral supplementation
  • Severe: <2.5 mmol/L -> ECG + fast correction with IV KCl, then repeat serum potassium after 1 hour
    • ±IV KCl maintenance in drip / oral supplementation

*There is no fixed rule on the treatment. Treatment must be aligned with clinical judgement.

Calculation of potassium deficit & requirement

(i) Potassium deficit

Potassium deficit (g) = [(4 – current potassium level) × 0.4 × bodyweight]/13.4]

• 1 g KCl contains 13.4 mmol potassium & 13.4 mmol chloride (as shown in the picture above)
• 1 vial = 10 mL KCl = 1 g KCl

(ii) Potassium requirement

Potassium daily requirement (g) = 1 mmol/kg/day

Example

Patient X, weight 60kg, serum potassium 2.5 mmol/L

• Deficit: [(4 – 2.5) x 0.4 x 60] / 13.4 = 2.68 g
• Daily requirement: 1 x 60 / 13.4 g = 4.47 g

• Correction of deficit: fast correct with IV KCl 2g in 200 mL NS over 2 hours
  • Repeat serum potassium post correction
• Daily requirement:
  • If the patient is on IV drip maintenance e.g. 4 pints NS / 24 hours, may add 1g KCl in each pint NS (the calculated requirement is 4.47 g per day. Hence 1g in each pint is applicable.)
  • If the patient is not on IV drip and having good oral intake, add oral potassium supplement (e.g. Tab Slow K 1.2 g TDS for 3 days), and encourage oral intake

Medications for hypokalaemia

• Intravenous – IV KCl, examples of administration:
  • IV KCl 1g in 100 mL NS over 1 hour
  • IV KCl 2g in 200 mL NS over 2 hours
• Oral:
  • Tab Slow K e.g. 1.2 g TDS
  • Mist KCl e.g. 15 mL TDS

Introduction

• Normal range of serum potassium: 3.5 – 5.1 mmol/L
• Severity of hyperkalaemia:
  • Mild: 5.5 – 5.9 mmol/L
  • Moderate: 6 – 6.4 mmol/L
  • Severe: ≥6.5 mmol/L
• One very common cause of ‘hyperkalaemia’ is lysed sample. Remeber to check lab formal report whether there is any documentation regarding lysed sample. In that case, it is better to repeat RP / potassium first before starting treatment for the ‘hyperkalaemia’.

• Not all hyperkalaemia cases require fast correction with lytic cocktail!
• Moderate / Severe hyperkalaemia warrants fast correction, but also depends on clinical condition

Lytic cocktail regime

• IV Calcium gluconate 10% over 10 minutes (ideally attach with cardiac monitor during administration), then
• IV Dextrose 50% 50 mL , then
• IV Actrapid 10 units (1 mL)

Repeat serum potassium 1 hour post lytic cocktail, may require repeated lytic cocktail / urgent haemodialysis if persistent severe hyperkalaemia

Oral Kalimate

• Dose example: PO Kalimate 15 g TDS for 3 days
• Do not give oral Kalimate for long term due to risk of bowel necrosis

Flowchart of emergency management of hyperkalaemia

“49 years old man, no known medical illness, presented with lethargy for 3 weeks, loss of appetite for 2 weeks, and constipation for 3 days. At ED, noted corrected serum calcium 3.98 mmol/L”

Introduction

• Normal range of serum calcium: 2.1 – 2.65 mmol/L
• Severe hypercalcaemia = Serum calcium >3.5 mmol/L
• Acute therapy is warranted if serum calcium >3 mmol/L or severe symptoms
• Patients with severe hy[ercalcaemia are usually dehydrated during initial presentation

Investigations

(i) Initial investigations

• FBC, RP, Ca, Mg, PO4
• LFT (look for ALP level)
• Thyroid function test
• iPTH (intact parathyroid hormone)

(ii) Other investigations to be considered

• If suspect PTB / TB related hypercalcaemia: CXR, Sputum AFP x1, x2, x3; Sputum MTB GeneXpert
• If suspect malignancy (e.g. multiple myeloma): urine protein electrophoresis, serum protein electrophoresis, skeletal survey, full blood picture, tumour markers
• KUB X-rays, KUB USG e.g. if AKI not resolving despite on hydration — TRO obstructive uropathy

Acute therapy of severe hypercalcaemia

1) Hyperhydration

• Initially 300 – 500 mL normal saline over 1 hour, sometimes up to 10 – 20 mL/kg over 1 hour
• Followed by 3 – 4L (=6 – 8 pints) normal saline over 24 hours
• Correct electrolyte abnormality e.g. IV KCl maintenance / fast correction for hypokalaemia; IV MgSO4 for hypomagnesaemia

• Hyperhydration with 3 – 4L normal saline over 24 hours can be given for 2 – 3 days, depending on clinical response and assessment
  • The patient must be reassessed (e.g. after 24 hours of fluid) to determine whether fluid can be titrated down or maintained. Check input/output balance, RP, and electrolytes.
  • How much fluid to be given depends on patient’s hydration status (e.g. from IVC diameter & collapsibility; presence of GI loss, amount of oral intake, urine output; CVP monitoring if available), haemodynamic status (BP, HR), and whether patient having fluid restriction (e.g. CCF, ESRF)
• Normal saline helps to restore extracellular fluid (i.e. rehydrate the patient) and to promote calcium excretion (Na competitively inhibits renal tubular absorption of Ca)

2) Diuretics

• IV Frusemide 20 – 40 mg TDS

• DO NOT use thiazides which can reduce calcium excretion
• IV Frusemide helps to prevent fluid overload and to further promote calcium excretion

3) Bisphosphonates

Examples:

• Zoledronate (Zometa®): IV Zoledronate 4 mg over at least 15 minutes (agent of choice for malignancy-associated hypercalcaemia because it’s more potent and effective than pamidronate)
• Pamidronate: IV Pamidronate 30 mg / 60 mg / 90 mg in 1L normal saline over 4 – 6 hours.
  • Action starts after several days and lasts for weeks to months
  • Example dose: 30 mg for Ca <3 mmol/L, 60 mg for Ca 3 – 3.4 mmol/L, 90 mg for Ca >3.4 mmol/L)

• Useful especially if suspect hypercalcaemia due to malignancy. Bisphosphonates work by inhibiting bone resorption.
• Prescriber category: A* (must be discussed with specialist for initiation and dosage)
• Treatment can be repeated if hypercalcaemia recurs (usually after 2 – 3 weeks)

4) Treatment of underlying disease / cause

Further reading

• Sarawak Handbook of Medical Emergencies (4th edition)

“Patient X, presented with fitting episode. Upon arrival at ED, blood taken shows serum calcium 1.4, albumin 40″

Introduction

• Normal range of serum calcium: 2.1 – 2.65 mmol/L
• Fast correction is indicated if the patient is symptomatic or if hypocalcaemia is severe e.g. <1.8 mmol/L

Correction of severe / acute symptomatic hypocalcaemia:

Fast correction, followed by infusion

(i) Fast correction

• IV calcium gluconate 10% 10 mL over 10 minutes

(ii) IV infusion of Calcium gluconate 10%

• Rate: 1 mg elemental calcium/kg/hr // 0.5 – 2 mg/kg/hr
• Dilute 50 mL (i.e. 5 vials) of Calcium gluconate 10% into 400 mL of D5% or normal saline -> final volume = 450 mL -> 1mg/mL of elemental calcium solution

• For example, a 70 kg patient requiring 1 mg/kg/hr of elemental calcium will need 70 mL of infusion per hour

• Correct hypomagnesaemia if present.
• Treat underlying cause

Writing the instruction:

1. Add 50 mL of Calcium gluconate 10% into 400 mL normal saline. Total volume = 450 mL = 1 mg/mL calcium.
2. Run diluted IVI calcium gluconate 10% at 50 mL/hr*
3. Repeat serum calcium after fast correction
4. Monitor serum calcium and albumin levels 4 -6 hourly
5. Aim corrected calcium level 2 – 2.25 mmol/L
6. Correct hypomagnesaemia if present

[*If the patient’s weight is 70 kg, 50 mL/hr = 0.71 mg/kg/hr (within the range of elemental calcium 0.5 – 1 mg/kg/hr)]

[*If the patient has fluid restriction, e.g. ESRF consider to give half of the standard infusion e.g. 25 mL/hr]

Further reading:

• Sarawak Handbook of Medical Emergencies 4th ED (7.16)