Hyperkalemia 

Definition

Hyperkalemia is defined as:

πŸ‘‰ Serum potassium > 5.0 mEq/L

Severity Classification

Severity

Potassium Level

Mild

5.1 – 5.5 mEq/L

Moderate

5.6 – 6.4 mEq/L

Severe

β‰₯ 6.5 mEq/L or ECG changes

Clinical severity correlates more with rate of rise rather than absolute level.

Normal Potassium Physiology

Distribution

  • Total body potassium β‰ˆ 3500 mEq
  • 98% intracellular
  • 2% extracellular

Regulation of Potassium Balance

1. Renal Excretion (Major Mechanism)

Occurs in:

  • Distal convoluted tubule
  • Collecting duct (principal cells)

Controlled by:

  • Aldosterone
  • Distal sodium delivery
  • Tubular flow rate


2. Cellular Shift

Potassium moves between intracellular and extracellular compartments via:

Factor

Effect

Insulin

Drives K inside cells

Ξ²2 stimulation

Drives K inside

Acidosis

Moves K outside

Hyperosmolality

Moves K outside

Exercise

Transient increase


Etiology of Hyperkalemia

A. Decreased Renal Excretion

Renal Causes

  • Acute kidney injury
  • Chronic kidney disease
  • Tubular disorders
  • Obstructive uropathy


Endocrine Causes

  • Hypoaldosteronism
  • Adrenal insufficiency
  • Type 4 RTA


Drug-Induced Hyperkalemia

Drug Class

Examples

Mechanism

RAAS inhibitors

ACE inhibitors, ARBs

↓ Aldosterone

Potassium-sparing diuretics

Spironolactone, Amiloride

↓ K excretion

NSAIDs

Various

↓ Renin

Heparin

UFH, LMWH

↓ Aldosterone synthesis

Trimethoprim

Co-trimoxazole

ENaC blockade

Calcineurin inhibitors

Cyclosporine, Tacrolimus

Tubular toxicity

Beta blockers

Non-selective

↓ Cellular uptake


B. Transcellular Shift Causes

  • Metabolic acidosis
  • DKA
  • Tumor lysis syndrome
  • Rhabdomyolysis
  • Hemolysis
  • Burns
  • Hyperosmolar states


C. Excess Potassium Load

  • Potassium supplements
  • Blood transfusion (stored blood)
  • Salt substitutes
  • Parenteral nutrition


D. Pseudohyperkalemia

False elevation due to sample error.

Common causes:

  • Hemolyzed sample
  • Leukocytosis
  • Thrombocytosis
  • Prolonged tourniquet use


Clinical Manifestations

Neuromuscular Symptoms

  • Muscle weakness
  • Flaccid paralysis
  • Ascending paralysis
  • Reduced reflexes


Cardiac Manifestations (Most Dangerous)

Arrhythmias include:

  • Ventricular tachycardia
  • Ventricular fibrillation
  • Asystole


ECG Changes in Hyperkalemia 

Sequential ECG Changes

Potassium Level

ECG Finding

5.5–6.5

Tall peaked T waves

6.5–7.5

P wave flattening, PR prolongation

7.5–8.5

QRS widening

>8.5

Sine wave pattern β†’ arrest

ECG severity does not always correlate with potassium level.


Urinary Indices

Transtubular Potassium Gradient (TTKG)

The Transtubular Potassium Gradient (TTKG) is a calculated index used to estimate:

πŸ‘‰ How effectively the cortical collecting duct is secreting potassium
πŸ‘‰ Whether the kidney is responding appropriately to hyperkalemia

Helps differentiate renal vs extrarenal causes . But Not commonly used in routine ICU practice today.


TTKG

Interpretation

<5

Impaired renal excretionβ€”Hypoaldosteronism

Type 4 RTA,Adrenal insufficiency,RAAS inhibitor use,Advanced CKD

>7

Appropriate renal response


Indications for Immediate Treatment

πŸ‘‰ K β‰₯ 6.5 mEq/L
πŸ‘‰ ECG changes
πŸ‘‰ Rapidly rising potassium
πŸ‘‰ Neuromuscular symptoms

πŸ”΄ Step 1 – Cardiac Membrane Stabilization (Immediate)

Drug

Dose

Onset

Duration

Key Notes

IV Calcium Gluconate (10%)

10 mL IV over 2–5 min

1–3 min

30–60 min

Does NOT lower K

IV Calcium Chloride (10%)

10 mL IV (central line)

1–3 min

30–60 min

More potent; avoid peripheral vein


🟑 Step 2 – Shift Potassium into Cells

Therapy

Dose

Onset

Duration

↓K Expected

Important Risk

Regular Insulin + Dextrose

10 units IV + 25 g glucose

15–30 min

4–6 hrs

↓ 0.6–1.2 mEq/L

Hypoglycemia

Nebulized Salbutamol

10–20 mg

30 min

2–4 hrs

↓ 0.5–1 mEq/L

Tachycardia

IV Sodium Bicarbonate

50–100 mEq (if acidotic)

30–60 min

Variable

Mild

Volume overload

🟒 Step 3 – Remove Potassium from Body (Definitive Control)

Therapy

Onset

Indication

Key Notes

Loop Diuretics (Furosemide)

1–2 hrs

If urine output present

Needs functioning kidney

Sodium Polystyrene Sulfonate

2–6 hrs

Mild–moderate cases

Risk: bowel necrosis

Patiromer

4–7 hrs

CKD

Not for emergencies

Sodium Zirconium Cyclosilicate

1–2 hrs

Subacute

Safer than SPS

Hemodialysis

Immediate

Severe/refractory

Definitive therapy


πŸ”΅ Dialysis Indications 

  • Severe renal failure
  • Refractory hyperkalemia
  • Life-threatening ECG changes
  • Ongoing tissue breakdown
  • Severe metabolic acidosis