5Hs and 5Ts in myocardial infraction
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5 Hs and 5 Ts cardiac arrest reversible causes ACLS
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Here is a complete, structured overview of the 5 Hs and 5 Ts - the reversible causes of cardiac arrest per ACLS guidelines.
Clarification: 5 Hs & 5 Ts vs. MI
The 5 Hs and 5 Ts are not specific to MI - they are the reversible causes of cardiac arrest (especially PEA and asystole). Coronary thrombosis (MI) is itself one of the "Ts." The framework helps rescuers ask: why did this arrest happen, and can I fix it right now?
The 5 Hs
| H | Full Name | Pathophysiology | Recognition | Treatment |
|---|---|---|---|---|
| H1 | Hypovolemia | Reduced preload and cardiac output from blood loss or dehydration | Flat neck veins, hypotension, tachycardia, trauma history | IV fluid bolus, blood transfusion, control bleeding |
| H2 | Hypoxia | Inadequate oxygen delivery leads to myocardial and cerebral dysfunction | Airway obstruction, cyanosis, low SpO2 | Ensure patent airway, high-flow O2, bag-mask ventilation, intubation |
| H3 | Hydrogen ion excess (Acidosis) | Metabolic acidosis depresses myocardial contractility and response to catecholamines | Low pH and HCO3 on ABG, history of shock or respiratory failure | Correct underlying cause; sodium bicarbonate in severe cases; optimize ventilation |
| H4 | Hypo/Hyperkalemia | Electrolyte imbalance disrupts cardiac membrane potential | ECG changes: peaked T-waves (hyperK), flattened T-waves/U-waves (hypoK); renal failure history | Calcium gluconate (hyperK), potassium replacement (hypoK), consider dialysis |
| H5 | Hypothermia | Core temperature <30°C severely depresses cardiac function; "no one is dead until warm and dead" | Cold skin, history of exposure, low core temp | Passive and active rewarming; continue CPR until normothermia is achieved |
The 5 Ts
| T | Full Name | Pathophysiology | Recognition | Treatment |
|---|---|---|---|---|
| T1 | Tension Pneumothorax | Trapped air collapses lung and shifts mediastinum, compressing heart and great vessels | Absent breath sounds (unilateral), tracheal deviation, distended neck veins | Immediate needle decompression (2nd ICS, MCL), then chest tube |
| T2 | Tamponade (Cardiac) | Pericardial fluid compresses cardiac chambers, reducing filling and output | Beck's triad: hypotension, muffled heart sounds, JVD; confirmed on bedside echo | Pericardiocentesis |
| T3 | Toxins | Drug/substance overdose depresses CNS and myocardial function | History of ingestion; medication reconciliation; specific toxidromes | Specific antidotes (naloxone for opioids, atropine for organophosphates, lipid emulsion for LA toxicity, etc.); contact poison control |
| T4 | Thrombosis - Pulmonary (PE) | Massive PE obstructs pulmonary circulation, causing acute right heart failure and arrest | Sudden onset, risk factors for DVT/PE, ETCO2 drop, echo showing right heart strain | Systemic thrombolytics (tPA), or surgical/catheter embolectomy; prolonged CPR if lytics given |
| T5 | Thrombosis - Coronary (MI) | Coronary occlusion causes ischemia, ventricular fibrillation, or pump failure | Preceding chest pain, ST changes on 12-lead ECG, wall motion abnormality on echo | Emergency PCI (percutaneous coronary intervention); fibrinolytics if PCI unavailable |
Key Points for Clinical Practice
- These causes are most relevant for PEA and asystole, where no shockable rhythm exists and the underlying cause must be found and fixed.
- They also apply to refractory VF/VT that does not respond to defibrillation.
- A bedside ultrasound (POCUS) during CPR can rapidly identify tamponade, severe hypovolemia, tension pneumothorax, and massive PE simultaneously.
- Per the 2020 AHA ACLS guidelines, the Hs and Ts should be evaluated during every cardiac arrest - they are part of the secondary assessment running in parallel with resuscitation efforts.
- Intraoperative arrests should also consider air embolism as an additional T.
Memory Aid
5 Hs: Hypovolemia, Hypoxia, H+ (Acidosis), Hypo/Hyperkalemia, Hypothermia
5 Ts: Tension pneumothorax, Tamponade, Toxins, Thrombosis-PE, Thrombosis-MI
Source: Miller's Anesthesia 10e; StatPearls ACLS (NCBI NBK613285); 2020 AHA ACLS Guidelines
5Hs and 5Ts for hypotension and hyepertension
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5 Hs 5 Ts mnemonic hypotension hypertension causes differential diagnosis
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Good - I now have all the content needed. Here is a clear, complete answer.
Important Clarification First
There is no official "5 Hs and 5 Ts" mnemonic for hypotension or hypertension in standard medical literature. The 5 Hs and 5 Ts belong exclusively to cardiac arrest (ACLS). For hypotension and hypertension, different frameworks are used - I'll cover those systematically below.
HYPOTENSION - Causes & Framework
The standard approach classifies hypotension by shock mechanism, using the 4-category (HDCO) framework:
The 4 Types of Shock / Hypotension
| Type | Core Problem | JVP | CO | SVR | Prevalence |
|---|---|---|---|---|---|
| Distributive | Low vascular resistance (vasodilation) | ↓ | ↑ | ↓↓ | ~65% |
| Hypovolemic | Low intravascular volume | ↓ | ↓ | ↑ | ~15% |
| Cardiogenic | Pump failure | ↑ | ↓↓ | ↑ | ~15% |
| Obstructive | Mechanical obstruction to flow | ↑ | ↓ | ↑ | <5% |
(Frameworks for Internal Medicine; Goldman-Cecil Medicine)
1. Distributive Shock (most common - ~65%)
- Septic shock (most common of all)
- Anaphylactic shock
- Neurogenic shock (spinal cord injury)
- Adrenal insufficiency (Addisonian crisis)
- Hepatic failure
- Pancreatitis
- Arteriovenous shunts
2. Hypovolemic Shock (~15%)
Hemorrhagic:
- Trauma
- GI hemorrhage (varices, peptic ulcer)
- Intra-abdominal (ruptured AAA, ectopic pregnancy)
- Post-surgical/procedural bleeding
Non-hemorrhagic (volume depletion):
- Vomiting / diarrhea
- Excessive diuresis
- Burns
- Third-spacing (pancreatitis, bowel obstruction)
3. Cardiogenic Shock (~15%)
- Acute MI / left ventricular failure
- Severe cardiomyopathy
- Acute valvular dysfunction (mitral regurgitation, aortic stenosis)
- Arrhythmias (severe bradycardia or tachycardia)
- Myocarditis
4. Obstructive Shock (<5%)
- Tension pneumothorax
- Cardiac tamponade
- Massive PE
- Severe pulmonary hypertension
- Constrictive pericarditis
Note: The last three "obstructive" causes overlap with the Ts in the cardiac arrest mnemonic.
HYPERTENSION - Causes & Framework
Hypertension is classified as primary (essential) or secondary. Secondary causes are organized by organ system:
Primary vs. Secondary
| Primary (Essential) | Secondary | |
|---|---|---|
| Prevalence | 90-95% | 5-10% |
| Cause | Multifactorial (genetic, lifestyle) | Identifiable underlying disease |
| When to suspect secondary | Young age, resistant HTN, sudden onset, hypokalemia, abnormal labs |
Secondary Hypertension - Causes by System
1. Renal (most common secondary cause)
- Chronic kidney disease (CKD)
- Acute kidney injury
- Renovascular disease / renal artery stenosis
- Polycystic kidney disease
- Acute glomerulonephritis
2. Endocrine
- Primary hyperaldosteronism (Conn syndrome) - most common endocrine cause
- Pheochromocytoma - must-not-miss (0.1-0.6% of cases)
- Cushing syndrome (excess cortisol)
- Thyroid disease (hypo- or hyperthyroidism)
- Hyperparathyroidism
- Acromegaly
3. Vascular
- Renovascular disease (fibromuscular dysplasia, atherosclerosis)
- Coarctation of the aorta (especially young patients)
4. Pulmonary
- Obstructive sleep apnea (very common, often missed)
5. Drug-Induced
- NSAIDs / COX-2 inhibitors
- Oral contraceptives (estrogen)
- Corticosteroids (prolonged use)
- Cocaine / amphetamines / sympathomimetics
- Cyclosporine / tacrolimus
- Erythropoietin
- Alcohol (chronic)
6. Other
- Obesity
- Ureteral / bladder outlet obstruction
- Pre-eclampsia / eclampsia (in pregnancy)
Memory Aids (Custom Mnemonics)
For Hypotension/Shock - remember "DCHO":
Distributive, Cardiogenic, Hypovolemic, Obstructive
For Secondary Hypertension - remember "RECIPE":
Renal, Endocrine, Coarctation (vascular), Iatrogenic (drugs), Pulmonary (sleep apnea), Eclampsia (pregnancy)
Sources: Frameworks for Internal Medicine; Symptom to Diagnosis 4th Ed.; Goldman-Cecil Medicine; Miller's Anesthesia 10e
5H and 5T for OT technician students
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5 Hs 5 Ts operation theatre OT technician perioperative cardiac arrest intraoperative
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