Hypokalaemia Nursing Guide

Definition & Classification

Hypokalaemia is defined as serum potassium < 3.5 mmol/L. Normal range: 3.5–5.0 mmol/L.

Mild
3.0–3.5 mmol/L

Moderate
2.5–3.0 mmol/L

Severe
< 2.5 mmol/L

Critical: K⁺ < 2.5 mmol/L or ANY ECG changes = emergency. Immediate cardiomonitoring + urgent replacement required.

Symptoms by System

Neuromuscular

Muscle weakness, cramps, fatigue
Ascending paralysis (severe)
Hypo/areflexia
Rhabdomyolysis (severe K⁺ < 2.5)

Cardiac

Palpitations, premature beats
AF, ventricular ectopics
VT/VF (life-threatening)
Enhanced digoxin toxicity

GI

Nausea, vomiting
Constipation, ileus
Abdominal distension

Renal

Polyuria, polydipsia (nephrogenic DI)
Metabolic alkalosis
Increased ammonia production

Quick Reference — Key Numbers

Parameter	Value	Clinical Significance
Normal K⁺	3.5–5.0 mmol/L	Target range
Mild hypokalaemia	3.0–3.5	Oral replacement; monitor ECG
Moderate	2.5–3.0	IV replacement if symptomatic
Severe / Critical	< 2.5	Emergency IV replacement + cardiac monitor
Max IV rate (peripheral)	10 mmol/hr	Never exceed without central line monitoring
Max IV rate (central, ICU)	20–40 mmol/hr	Continuous cardiac monitoring mandatory
Max concentration peripheral	40 mmol/L (0.3%)	Higher = phlebitis/extravasation risk

NEVER give IV potassium as a bolus/push. IV K⁺ push = cardiac arrest. Always infuse slowly via pump.

ECG Changes in Hypokalaemia

ECG changes occur progressively as K⁺ falls. Unlike hyperkalaemia (peaked T waves), hypokalaemia causes flattened/inverted T waves and prominent U waves.

3.0–3.5

Flattened T waves
Mild ST depression

2.5–3.0

Prominent U waves
T-U wave fusion

2.0–2.5

Widened QRS
Prolonged QT

< 2.0

VT / Torsades
VF / Arrest

U wave: A positive deflection after the T wave, best seen in V2–V3. Prominent U wave (>1mm or taller than T wave) = hallmark of hypokalaemia.

Digoxin + Hypokalaemia = Dangerous: Hypokalaemia potentiates digoxin toxicity even at therapeutic digoxin levels. Always correct K⁺ before/alongside digoxin therapy.

Monitoring Requirements

Severity	Monitoring	Recheck K⁺
Mild (3.0–3.5)	Vital signs, symptoms	24–48 hrs after replacement
Moderate (2.5–3.0)	Continuous cardiac monitor if IV	4–6 hrs after replacement
Severe (<2.5) or ECG changes	Continuous cardiac monitor + ICU consideration	Every 1–2 hrs during replacement

Magnesium — The Hidden Key

Critical Concept: Hypomagnesaemia causes refractory hypokalaemia. If K⁺ fails to correct despite adequate replacement, check and correct Mg²⁺ first. Normal Mg²⁺: 0.7–1.0 mmol/L.

Low Mg²⁺ promotes K⁺ loss through the kidneys (inhibits ROMK channels)
Always check Mg²⁺ in hypokalaemia — especially in diarrhoea, alcoholism, diuretic use, PPIs
If Mg²⁺ < 0.7: give IV magnesium sulphate 2–4g over 30–60 minutes
Concurrent phosphate and calcium should also be checked

Potassium Replacement Protocol

Assess severity and symptoms — mild/asymptomatic vs moderate/severe or ECG changes. Obtain baseline ECG, UE, Mg²⁺, phosphate.

Oral replacement (mild, no ECG changes) — Sando-K or KCl dispersible tablets 2–4 tablets (48–96 mmol) daily in divided doses. Well absorbed and preferred route when tolerated.

IV replacement (moderate-severe, symptomatic, nil-by-mouth) — KCl in 0.9% NaCl or Hartmann's solution via infusion pump. Max 10 mmol/hr peripheral (up to 20–40 mmol/hr via central line in ICU with continuous monitoring).

Recheck electrolytes — serum K⁺ 4–6 hours after IV replacement, or 24 hours after oral. Adjust dose accordingly.

Treat underlying cause — stop culprit diuretic if possible, treat diarrhoea/vomiting, correct hypomagnesaemia.

IV Potassium Preparation Guidelines

Route	Max Concentration	Max Rate	Monitoring
Peripheral IV	40 mmol/L (0.3%)	10 mmol/hr	Cardiac monitor if rate >10 mmol/hr
Central venous (ICU)	Up to 200 mmol/L	20–40 mmol/hr	Continuous ECG mandatory

NEVER:

Bolus/push IV potassium — causes cardiac arrest
Give neat KCl ampoule undiluted
Infuse at >10 mmol/hr peripherally without cardiac monitoring
Use dextrose solutions to dilute KCl (insulin release drives K⁺ into cells — worsens hypokalaemia)

Potassium-Sparing Strategies

Add potassium-sparing diuretic (spironolactone, amiloride) if ongoing diuretic need
ACE inhibitors / ARBs reduce renal K⁺ wasting
High-potassium diet: bananas, avocados, dates, lentils, oranges
Ensure adequate dietary magnesium intake concurrently

Calculating Potassium Deficit

Approximate formula (only an estimate — clinical monitoring essential):

K⁺ deficit (mmol) = (Desired K⁺ – Actual K⁺) × 0.4 × Body weight (kg)
Example: 70 kg patient, K⁺ = 2.8, target = 4.0
Deficit = (4.0 – 2.8) × 0.4 × 70 = 33.6 mmol
Note: This under-estimates true deficit as only ~2% of total body K⁺ is extracellular.

Clinical practice: replace in increments of 20–40 mmol IV, recheck, repeat — rather than replacing total estimated deficit in one infusion.

Causes of Hypokalaemia

Remember using 3 mechanisms: Inadequate intake, GI losses, Renal losses, Shift into cells.

GI Losses (most common)

Vomiting / NGT suctioning
Diarrhoea, ileostomy, fistulae
Laxative abuse
VIPoma (severe secretory diarrhoea)

Renal Losses

Diuretics — thiazides & loop diuretics (most common drug cause)
Primary/secondary hyperaldosteronism (Conn's)
Cushing's syndrome
Renal tubular acidosis type I & II
Hypomagnesaemia
Bartter/Gitelman syndromes

Transcellular Shift

Insulin + dextrose infusion
Beta-2 agonists (salbutamol, terbutaline)
Alkalosis (respiratory or metabolic)
Familial hypokalaemic periodic paralysis
Thyrotoxic periodic paralysis

Inadequate Intake

Prolonged NG/TPN without adequate K⁺
Anorexia nervosa / eating disorders
Poor diet during Ramadan (reduced meals)

GCC-Specific Clinical Context

Ramadan & Hypokalaemia ▼

Ramadan fasting patients may have reduced K⁺ intake from fewer meals. Diuretics taken once daily during Iftar can lead to nocturnal K⁺ wasting. Monitor electrolytes in diuretic-dependent patients during Ramadan. Dates (common Iftar food) are a useful natural potassium source.

Diarrhoeal Illnesses & Food Preparation ▼

GCC countries have a high burden of gastroenteritis during summer months (outdoor catering, Hajj/Umrah food mass preparation). Severe diarrhoea + vomiting leads to combined hyponatraemia, hypokalaemia, and dehydration. Always check full electrolyte panel in gastroenteritis admissions.

Hajj Medical Teams: Periodic Paralysis ▼

Thyrotoxic periodic paralysis (TPP) is more common in Asian and Middle Eastern pilgrims. Severe hypokalaemia (often K⁺ < 2.5) causes acute flaccid paralysis during Hajj. Treat with IV K⁺ replacement — avoid beta-agonists and high carbohydrate intake which worsen the shift. Check thyroid function.

Diuretics in GCC Hypertensive Patients ▼

Hypertension is highly prevalent across GCC countries. Loop (furosemide) and thiazide (bendroflumethiazide, indapamide) diuretics are commonly prescribed. K⁺ supplementation or potassium-sparing diuretics (spironolactone) should be considered in patients on long-term loop or thiazide diuretics, especially the elderly.

Heat, Sweat & K⁺ Loss in GCC ▼

Heavy physical work in extreme GCC heat (construction workers, outdoor labourers) causes massive sweat losses. Sweat contains K⁺ (~5 mmol/L). In combination with inadequate dietary intake, this can cause significant hypokalaemia — presenting as muscle cramps, weakness, and arrhythmias in occupational health settings.

Complications of Hypokalaemia

Cardiac
Ventricular tachycardia, Torsades de Pointes, ventricular fibrillation, cardiac arrest. Potentiation of digoxin toxicity at therapeutic levels.

Neuromuscular
Ascending muscle weakness → respiratory muscle paralysis requiring mechanical ventilation. Rhabdomyolysis with myoglobinuria and acute kidney injury.

Renal
Nephrogenic diabetes insipidus (polyuria, polydipsia). Metabolic alkalosis. Increased renal ammoniagenesis — may precipitate hepatic encephalopathy in cirrhosis.

GI
Paralytic ileus, constipation, abdominal distension, nausea. In severe cases, bowel obstruction-like presentation requiring surgical review.

Drug Interactions Worsening Hypokalaemia

Drug	Mechanism	Clinical Note
Loop diuretics (furosemide)	Renal K⁺ wasting	Most common cause of drug-induced hypokalaemia
Thiazide diuretics	Renal K⁺ wasting	Especially with indapamide
Salbutamol (IV/high dose)	Beta-2: K⁺ shift into cells	Monitor in severe asthma treated with back-to-back nebs
Amphotericin B	Renal tubular toxicity	Daily electrolytes during antifungal therapy
Insulin + dextrose	Intracellular shift	Used therapeutically in hyperkalaemia — can overshoot
Corticosteroids	Mineralocorticoid effect → renal loss	Monitor K⁺ in long-term steroid patients
Gentamicin	Renal tubular wasting	Also causes hypomagnesaemia

MCQ Practice — Hypokalaemia

Q1. A patient's serum K⁺ is 2.8 mmol/L. The ECG shows prominent U waves and flattened T waves. The MOST appropriate immediate action is:

A) Oral Sando-K tablets and recheck in 24 hours

B) IV KCl infusion with continuous cardiac monitoring

C) IV potassium chloride bolus 10 mmol over 5 minutes

D) Administer IV calcium gluconate first

✅ B — ECG changes with K⁺ 2.8 requires IV replacement with cardiac monitoring. Oral replacement is insufficient urgency. IV bolus is NEVER appropriate. Calcium gluconate is used for hyperkalaemia, not hypokalaemia.

Q2. A patient on long-term furosemide has persistent hypokalaemia despite adequate oral potassium replacement. Serum Mg²⁺ is 0.55 mmol/L. The correct next step is:

A) Double the oral potassium dose

B) Switch to IV potassium replacement

C) Administer IV magnesium sulphate first, then continue K⁺ replacement

D) Stop furosemide and recheck in 48 hours

✅ C — Hypomagnesaemia causes refractory hypokalaemia by promoting renal K⁺ wasting. Correcting magnesium first is essential for potassium replacement to be effective.

Q3. What is the maximum safe rate for peripheral IV potassium infusion in a monitored patient?

A) 20 mmol/hour

B) 10 mmol/hour

C) 40 mmol/hour

D) 5 mmol/hour

✅ B — Maximum peripheral IV KCl rate is 10 mmol/hr. Rates of 20–40 mmol/hr may be used via central line in ICU with continuous cardiac monitoring only.

Q4. Which ECG finding is the hallmark of hypokalaemia?

A) Peaked T waves

B) Shortened QT interval

C) Prominent U waves with flattened T waves

D) Widened P waves with delta waves

✅ C — Prominent U waves (positive deflection after T wave, best in V2–V3) with flattened/inverted T waves and ST depression are characteristic of hypokalaemia. Peaked T waves = hyperkalaemia.

Hypokalaemia — Nursing Guide