As anesthetic complications go, malignant hyperthermia is rare, but it's potentially fatal. It's possible to screen patients who report a family history of MH (it's inherited) and to prevent it by avoiding triggering agents, especially in patients who are known to be susceptible (see "Screening for MH"). But suppose that a patient whose operative history doesn't indicate susceptibility appears to be having an MH episode. Is it MH? Here are three real cases reported to the MH Hotline (800-MH-HYPER) to test your knowledge of the signs and symptoms of the complication.

1. Fever after circumcision
Scenario: A 9-month-old undergoes circumcision. Anesthesia is induced and maintained with sevoflurane, N2O and fentanyl. Intraoperatively, his axial temperature is 35.4?C (95.7?F). Three hours later, in Step 2 PACU, he is drinking and has urinated, but his axial temperature is 41?C (105.8?F).

Is it MH? Fever after any operation is very common, especially when you break an endothelial barrier, as you do in urological cases such as this, or in airway and GI procedures. It's even more common in pediatric cases (see "Challenging Four Myths of Pediatric Anesthesia" on page 40). When you consider that post-op MH is extremely rare, usually occurs intraoperatively (this fever is occurring three hours post-op) and that many kids will have fever after circumcision, MH is highly unlikely. If there is disproportionately increased minute ventilation, check end tidal CO2 and for clear urine to rule out myoglobinuria as a result of rhabdomyolysis. As it's unlikely that this scenario is MH, performing an arterial blood gas to determine respiratory acidosis is not recommended. The patient should be treated symptomatically with antipyretics and observed until normothermic.

2. The missing dantrolene
The scenario: A 28-year-old woman is undergoing her first surgery, a breast augmentation. Anesthesia is induced using sevoflurane and succinylcholine; intubation is accomplished without incident. Two hours into the procedure, the patient's end tidal CO2 is on the rise despite appropriate increases in minute ventilation, and her skin temperature rises from 34.4?C (93.9?F) to 36.6?C (97.8?F). Her heart rate rises from 80 beats per minute to 120 beats per minute.

Is it MH? Based on the signs and the extent of changes, the anesthesiology team recognized this as an acute MH episode. But there was no dantrolene at the office-based surgery center, so she could not be treated with the only drug that reverses MH. When the patient reached a local hospital's ER, her temperature was 43?C (109.4?F). Dantrolene was begun, but she died within 24 hours from disseminated intravascular coagulation.

This case highlights the importance of stocking dantrolene. But who should supply it - the surgical facility, or the anesthesia group or provider? A full 36-bottle supply of dantrolene costs about $2,500 (three-year shelf life), and isn't exactly portable. The Malignant Hyperthermia Association of the United States and JCAHO recommend having a full supply immediately available should MH occur, but there is no recommendation on who should provide it. The facility and the anesthesia group or provider need to work this out.

When should you stock dantrolene? Some say you should stock it only if you perform surgery under general anesthesia, as inhalational agents are known triggers for MH. However, patients can potentially require airway rescue even when non-triggering agents such as sedatives or propofol are used, which might require the use of the paralytic agent succinylcholine for emergency airway management. Succinylcholine is considered a triggering agent. MHAUS recommends stocking dantrolene in any facility that could potentially administer any triggering agent. After this particular case, the physician's insurance company mandated that dantrolene be available whenever triggering agents may be administered.

3. Increased end tidal CO2
The scenario: A 31-year-old male undergoing laparoscopic inguinal hernia repair, who has not previously received general anesthesia, is anesthetized with a combination of propofol, cisatracurium and sevoflurane. Intraoperatively, his end tidal CO2 is above 60mm Hg, despite increased minute ventilation. There is no rigidity or tachycardia.

Is it MH? An arterial blood gas was taken, and the patient's blood pH measured 7.23, indicating acidosis. There are a lot of reasons expired CO2 can increase; in the case of MH, it results from increased production compared to elimination. The fact that there is no rigidity or tachycardia indicates this may not be MH. The anesthesia provider noted that the patient's inspired CO2 levels were also high, indicating a possible problem with the anesthesia machine or valve apparatus. With MH, inspired CO2 is normal. The anesthesia machine was checked for malfunction, and the anesthesia team found that the CO2 absorbent was so old, it no longer changed color. Once the absorbent was changed, the patient did well.