Malignant Hyperthermia Clinical Grading Scale
Ranks how likely an episode was malignant hyperthermia, using the Larach clinical grading scale.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- End-tidal carbon dioxide over 55 mmHg with appropriate controlled ventilation
- Yes
- Generalized muscular rigidity
- Yes
- Creatine kinase over 20
- Yes
- Cola-colored urine perioperatively
- Yes
- Inappropriate sinus tachycardia
- Yes
Result: raw score 48, rank 5
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Raw score 0
- Rank 1, almost never. A score of 0 records that no indicator was described, not that malignant hyperthermia was excluded.
- 3 to 9
- Rank 2, unlikely.
- 10 to 19
- Rank 3, somewhat less than likely.
- 20 to 34
- Rank 4, somewhat greater than likely.
- 35 to 49
- Rank 5, very likely.
- 50 and above
- Rank 6, almost certain.
- Highest per process
- Only the highest-scoring indicator in each of the seven processes counts. Adding every indicator inflates the raw score.
- Not a treatment trigger
- The scale ranks likelihood for research and retrospective review. During a crisis dantrolene is given on clinical suspicion, and stopping to score is itself the harm.
- Fever
- Neither required nor early. An unexplained rise in end-tidal carbon dioxide under controlled ventilation is the earliest and most specific sign.
What you enter
- Generalized muscular rigidity (15 points)
- Masseter spasm shortly after succinylcholine (15 points)
- Creatine kinase over 20,000 units per liter after an anesthetic that included succinylcholine (15 points)
- Creatine kinase over 10,000 units per liter after an anesthetic without succinylcholine (15 points)
- Cola-colored urine perioperatively (10 points)
- Urine myoglobin over 60 micrograms per liter (5 points)
- Serum myoglobin over 170 micrograms per liter (5 points)
- Potassium over 6 millimoles per liter, without kidney failure (3 points)
The other 16 fields
- End-tidal carbon dioxide over 55 mmHg with appropriate controlled ventilation (15 points)
- Arterial carbon dioxide over 60 mmHg with appropriate controlled ventilation (15 points)
- End-tidal carbon dioxide over 60 mmHg with spontaneous ventilation (15 points)
- Arterial carbon dioxide over 65 mmHg with spontaneous ventilation (15 points)
- Inappropriate hypercarbia judged inappropriate by the anesthesia team (15 points)
- Inappropriate tachypnea (10 points)
- Inappropriately rapid increase in temperature judged inappropriate by the anesthesia team (15 points)
- Inappropriately increased temperature over 38.8 degrees Celsius perioperatively (10 points)
- Inappropriate sinus tachycardia (3 points)
- Ventricular tachycardia or ventricular fibrillation (3 points)
- Malignant hyperthermia in a first-degree relative (15 points)
- Malignant hyperthermia in a relative who is not first-degree (5 points)
- Arterial base excess more negative than -8 millimoles per liter (10 points)
- Arterial pH below 7.25 (10 points)
- Raised resting creatine kinase with a family history of malignant hyperthermia (10 points)
- Rapid reversal of the signs with intravenous dantrolene (5 points)
How this is calculated
Larach MG, Localio AR, Allen GC, et al. A clinical grading scale to predict malignant hyperthermia susceptibility. Anesthesiology. 1994;80(4):771-779. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.