This man has malignant hyperthermia, a rare but life-threatening complication of some anesthetics (particularly the volatile/inhaled) (FA2020 p550)

The treatment is dantrolene, a ryanodine receptor antagonist which decreases calcium release from the sarcoplasmic reticulum (Dantrolene is also used as a treatment for neuroleptic malignant syndrome).

If you want a refresher on what the heck a ryanodine receptor (RYR) is: (FA2020 p456)

• In skeletal muscle, the RYR is the calcium channel on the sarcoplasmic reticulum which is coupled to a voltage sensitive dihydropyridine calcium channel.
• Remember skeletal muscle is calcium channel induced calcium release, so it is an actual physical coupling of the receptors which causes the RYR to open (this is different than in cardiac muscle where the RYR are calcium induced, and it is a binding of calcium that triggers their opening)
• In the heart, dihydropyridine receptors are also called L-type calcium channels or Long-acting. T-type are a completely different channel and are transient (respond to lower voltage). RYR are still RYR but a different subtype than in skeletal muscle.