The Hs and Ts of ACLS are mnemonics used to recall major contributing factors to pulseless arrest.
Commonly associated with Pulseless Electrical Activity (PEA), but relevant for other arrhythmias in ACLS like Asystole, Ventricular Fibrillation, and Ventricular Tachycardia.
The Hs
Hypovolemia: Loss of fluid volume; check for blood loss; treat with CPR, intravenous/IO access, and fluid challenge.
Hypoxia: Inadequate oxygen supply; ensure airway is open and oxygen source is connected.
Hydrogen ion (acidosis): Check arterial blood gas for respiratory acidosis; treat with ventilation or sodium bicarbonate.
Hyper-/hypokalemia:
Hyperkalemia: High potassium; signs include tall T-waves, wide QRS; treat with sodium bicarbonate, glucose+insulin, calcium chloride, Kayexalate, dialysis, or albuterol.
Hypokalemia: Low potassium; signs include flat T-waves, prominent U-waves; treat with controlled IV potassium infusion.
Hypothermia: Exposure to cold; rewarm patient, raise core temperature above 86°F (30°C).
The Ts
Toxins: Overdose of medications or drugs (e.g., tricyclics, digoxin, cocaine); treat with circulation support and antidotes.
Tamponade: Fluid in pericardium; signs include JVD, muffled heart sounds; treat with pericardiocentesis.
Tension Pneumothorax: Air in pleural space; signs include JVD, tracheal deviation; treat with needle decompression.
Thrombosis (coronary): Blocked coronary artery causing MI; ECG signs include ST-segment changes; treat with fibrinolytic therapy or PCI.
Thrombosis (pulmonary): Blockage in lung artery causing PE; signs include positive d-dimer, distended neck veins; treat with surgery or fibrinolytics.
Removed Yet Important Causes
Hypoglycemia: Low blood glucose; treat with IV dextrose.
Trauma: Physical injuries; assess and treat reversible causes.