From the Guidelines
The earliest and most specific sign of malignant hyperthermia is an increase in end tidal CO2 (option c). This elevation in exhaled carbon dioxide occurs before other clinical manifestations and serves as a critical early warning sign of this potentially fatal condition, as evidenced by the 2021 guideline from the Association of Anaesthetists 1. Malignant hyperthermia is a rare genetic disorder triggered by certain anesthetic agents, causing hypermetabolism in skeletal muscle. The increased muscle metabolism produces excess CO2, which is detected in the exhaled breath before temperature elevation occurs.
Some key points to consider in the management of malignant hyperthermia include:
- An unexplained and unexpected progressive increase in carbon dioxide production as evidenced in ETCO2 should lead to a high index of suspicion for malignant hyperthermia 1
- The principles of management of a malignant hyperthermia reaction are to immediately reverse the reaction and treat the consequences of the reaction, including eliminating the trigger agent, giving intravenous dantrolene, and starting active body cooling 1
- Dantrolene should be given until the ETCO2 is < 6 kPa with normal minute ventilation and the core temperature is < 38.5°C 1
While tachycardia, hyperthermia (fever), hypotension, and hypoxia are all associated with malignant hyperthermia, they typically develop later in the progression of the syndrome. Anesthesia providers should immediately discontinue triggering agents, hyperventilate with 100% oxygen, administer dantrolene sodium, and initiate cooling measures when malignant hyperthermia is suspected, as outlined in the guideline 1. Early recognition through capnography monitoring and prompt intervention are essential for preventing mortality in this condition.
From the Research
Malignant Hyperthermia Signs
The earliest and most specific sign of malignant hyperthermia is:
Comparison of Options
Other options, such as:
- High fever, is a symptom but not the earliest sign 5, 6, 3
- Hypotension, is not the earliest sign and may occur later 5, 6
- Tachycardia, is a symptom but not the most specific sign 5, 6
- Hypoxia, is a symptom but not the earliest sign 5, 6
Evidence from Studies
Studies have shown that an increase in end tidal CO2 is a key indicator of malignant hyperthermia 2, 3, 4
- A case report described two cases of malignant hyperthermia where the earliest sign was a rise in end-tidal CO2 concentration 2
- Another case report described a patient who developed postoperative hyperthermia after mastectomy, which was diagnosed as malignant hyperthermia by the calcium-induced calcium release rate measurement test, and had a rapid increase in end-tidal carbon dioxide (ETCO2) 3
- A case report described a patient who underwent radical cervical cancer surgery under general anesthesia and experienced a gradual increase in end-tidal carbon dioxide (ETCO2) to a maximum of 75 mm Hg, which indicated malignant hyperthermia 4