# Intraoperatively a 25-year-old develops sudden tachycardia, jaw rigidity, ETCO2 doubling, and temperature 40.4 C while under sevoflurane and after succinylcholine. Which interventions should the team implement? Select all that apply.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=375024&lang=en  
> language: en  
> subject: Physiological Adaptation  
> category: PA

## Question

Intraoperatively a 25-year-old develops sudden tachycardia, jaw rigidity, ETCO2 doubling, and temperature 40.4 C while under sevoflurane and after succinylcholine. Which interventions should the team implement? Select all that apply.

1

Administer dantrolene 2.5 mg/kg IV bolus repeated to total 10 mg/kg

2

Apply active cooling with cold IV fluids and surface cooling

3

Hyperventilate with 100 percent oxygen at high fresh gas flow

4

Restart succinylcholine to relax masseter spasm

5

Discontinue volatile anesthetic and succinylcholine immediately

## Explanation

Malignant hyperthermia is a hereditary skeletal muscle channelopathy triggered by volatile anesthetics and succinylcholine. Treatment: STOP triggers, give dantrolene 2.5 mg/kg IV (repeat to 10 mg/kg total), hyperventilate with 100 percent oxygen at high flow to wash out CO2, active cooling (cold saline IV, ice packs, lavage) until temperature 38, treat hyperkalemia and acidosis. Charcoal filters on the anesthesia circuit reduce volatile residual. RESTARTING succinylcholine is contraindicated. Family must be counseled regarding screening.

## In-depth explanation

MH cart contents: dantrolene (Ryanodex 250 mg vial faster than older Dantrium 20 mg), sterile water, cooling supplies. Mortality dropped from 70 percent to under 5 percent with prompt dantrolene.

## Clinical scenario

Family history of unexplained anesthesia death. Surgery suspended.

## Key concepts

- **malignant hyperthermia** — Hereditary RYR1 channelopathy with massive intracellular calcium release in muscle.
- **dantrolene** — Ryanodine receptor antagonist; specific antidote for MH.
- **ETCO2** — End-tidal CO2; rapid rise is the earliest reliable sign of MH.

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