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Difficulty: MediumPreoperative and Postoperative Care

A 2828-year-old man with no significant past medical history is undergoing an elective open reduction and internal fixation of a right femur fracture. Anesthesia is induced with propofol and succinylcholine, and maintained with sevoflurane. Approximately 4545 minutes into the surgery, the anesthesiologist notes a sudden, unexplained rise in end-tidal carbon dioxide (ETCO2) from 3535 mmHg to 6868 mmHg. The patient's heart rate increases to 142142/min, and generalized masseter muscle rigidity is observed. His core body temperature begins to rise rapidly and is currently 39.4∘C39.4^\circ\text{C} (102.9∘F102.9^\circ\text{F}). Arrange the following steps in the most appropriate chronological sequence for the immediate management of this patient's suspected complication.

  1. 1Discontinue the administration of sevoflurane and succinylcholine.
  2. 2Hyperventilate the patient with 100%100\% oxygen at a high fresh gas flow rate.
  3. 3Administer rapid intravenous dantrolene sodium.
  4. 4Initiate active cooling measures using iced intravenous fluids and surface cooling.

Answer

The correct sequence for managing malignant hyperthermia is to first discontinue the triggering agents (sevoflurane and succinylcholine), then hyperventilate with 100% oxygen to clear residual gases, followed by the administration of intravenous dantrolene as the definitive antidote, and finally initiating active cooling measures.
Malignant hyperthermia is a life-threatening hypermetabolic crisis triggered by volatile anesthetics (e.g., sevoflurane) and depolarizing neuromuscular blockers (e.g., succinylcholine). According to standard protocols, the absolute first step is to remove the offending agents. This is immediately followed by hyperventilating the patient with 100% oxygen at high flows to flush the residual anesthetic gas from the circuit and correct hypercarbia. Once ABCs and trigger cessation are complete, the definitive pharmacological treatment, intravenous dantrolene (a ryanodine receptor antagonist), must be administered to stop the massive calcium release from the sarcoplasmic reticulum. Finally, supportive measures such as active cooling and correction of metabolic acidosis/hyperkalemia are implemented to prevent end-organ damage.

Step-by-Step Solution

1
Identify the clinical presentation of malignant hyperthermia.
Recognize that the sudden elevated ETCO2, tachycardia, muscle rigidity, and hyperthermia after succinylcholine and sevoflurane administration strongly indicate malignant hyperthermia.
Early recognition is crucial for patient survival in a perioperative hypermetabolic crisis.
2
Halt the inciting mechanism.
Discontinue sevoflurane and succinylcholine immediately.
Continued exposure to the triggering agents will worsen the unregulated calcium release from the sarcoplasmic reticulum.
3
Support respiratory function and clear the anesthetic.
Hyperventilate the patient with 100% oxygen.
This clears residual volatile agents from the anesthesia circuit and lungs, while directly addressing the severe hypercarbia.
4
Administer the specific antidote.
Give rapid intravenous dantrolene.
Dantrolene binds to the ryanodine receptor (RYR1), inhibiting calcium ion release from the sarcoplasmic reticulum and halting the hypermetabolic state.
5
Provide supportive physiological care.
Initiate active cooling and correct electrolyte abnormalities.
Severe hyperthermia can lead to rhabdomyolysis, brain damage, and disseminated intravascular coagulation if not rapidly controlled after the primary process is halted.

Key Concept

Management of Malignant Hyperthermia
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Topics

Preoperative and Postoperative Care

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