Ascension All Saints Hospital
Racine, Wis.
Malignant hyperthermia (MH) is a clinical syndrome characterized by elevated temperature, tachycardia, hypercarbia, acidosis, hyperkalemia and rigidity. The incidence of MH is estimated to range between one in 5,000 and one in 100,000. An MH event does not necessarily occur every time a susceptible person is exposed to an anesthetic triggering agent. Patients susceptible to MH have a defective calcium channel located in the membrane of the sarcoplasmic reticulum of the skeletal muscle.
A 20-year-old man, ASA class I, had elective right anterior cruciate ligament reconstruction as a result of an injury to the right knee while he was jumping on a trampoline. The patient’s weight was 82 kg, and he had no significant medical history. He had not undergone anesthesia with surgical procedures in the past. He denied any family history of complications with anesthesia. Preoperative blood routine evaluation was normal.
The patient received a single-shot adductor canal block in the preoperative area. He was induced using 100 mg of lidocaine and 200 mg of propofol. A laryngeal mask airway (LMA) size 4 was placed, followed by the placement of a nasopharyngeal temperature probe. Anesthesia was maintained with 50% oxygen and 50% air, and sevoflurane. The patient was breathing spontaneously, with an end-tidal carbon dioxide (ETCO2) ranging between 50 and 60, and a temperature starting at 36° C and gradually increasing. Two hours into the procedure, the ETCO2 suddenly rose to values between 80 and 99. The patient’s tidal volumes increased to over 1,000 mL.
Around the same time, the temperature increased from 37.2° C to 38° C over a 12-minute period. The patient’s heart rate also increased from the 80s to 110 beats per minute. Suspecting MH, we called for help. Sevoflurane was discontinued and a propofol infusion was started; charcoal filters were placed on the anesthesia machine; and the soda lime canister was changed. The surgeon was informed to expedite the surgery. An arterial line was placed, and administration of dantrolene was initiated with two doses of 2.5 mg/kg for a total of 5 mg/kg. During dantrolene administration, serial blood gases were measured every 15 minutes. All results showed respiratory acidosis (pH, =7.23), with potassium level increasing from 4.9 to 6.9 mmol/L.
Insulin and dextrose, and calcium gluconate were given to treat hyperkalemia. At the conclusion of the surgery, vital signs returned to normal, the LMA was removed and the patient was transferred to the PACU. His blood gases showed a pH of 7.35; pCO2, 51; bicarbonate, 27.1; and potassium, 4.7. Initial total creatine kinase in the PACU was 1,958 U/L (reference range, 29-168 U/L), and its value gradually decreased to 219 U/L over the next two days. The patient was admitted to the ICU for continuous observation and follow-up treatment with dantrolene. He was transferred to the floor on postoperative day (POD) 1 and then discharged home on POD 2.
Discussion
Malignant hyperthermia is a rare complication of anesthesia caused, in the majority of cases, by a defect in the ryanodine receptor. The increase in calcium in the sarcoplasmic reticulum leads to accelerated aerobic metabolism, resulting in acidosis, rigidity and hyperkalemia.
In our patient, the sudden increase in ETCO2 served as the earliest sign of MH. Although the patient did not develop muscle rigidity and his increased in temperature and tachycardia were not very significant, we realize that this was a result of prompt treatment with dantrolene.
The diagnosis of MH is presumptive, based on the presence of clinical manifestations associated with MH. There is no confirmatory test during an acute event. To determine the likelihood of MH (Table 1), Larach et al described a clinical grading score (Anesthesiology 1994;80[4]:771-779) (Table 2). In our case, the score was 58 (Table 3), which makes it almost certain that this was an MH crisis.
| Table 1. Clinical Significance of MH Raw Score and Rank | ||
| Raw score | MH rank | Likelihood of MH |
|---|---|---|
| 0 | 1 | Almost never |
| 3-9 | 2 | Unlikely |
| 10-19 | 3 | Less than likely |
| 20-34 | 4 | More than likely |
| 35-49 | 5 | Very likely |
| =50 | 6 | Almost certain |
| MH, malignant hyperthermia. | ||
| Table 2. Clinical Grading Score For MH | |
| Clinical indication | Points |
|---|---|
| Muscle rigidity | |
| Generalized rigidity | 15 |
| Masseter rigidity | 15 |
| Process II: myonecrosis | |
| Elevated CK >20,000 (after succinylcholine administration) | 15 |
| Elevated CK >10,000 (without succinylcholine) | 15 |
| Cola-colored urine 10 | |
| Myoglobin in urine >60 mL/L | 5 |
| Blood/plasma/serum K+ >6 mEq/L | 3 |
| Process III: respiratory acidosis | |
| PETCO2 >55 with controlled ventilation | 15 |
| PaCO2 >60 with controlled ventilation | 15 |
| PETCO2 >60 with spontaneous ventilation | 15 |
| Inappropriate hypercarbia | 15 |
| Inappropriate tachypnea | 10 |
| Process IV: temperature increase | |
| Rapid increase in temperature | 15 |
| Inappropriate temperature >38.8° Cin perioperative period | 10 |
| Process V: cardiac involvement | |
| Inappropriate tachycardia | 3 |
| Ventricular tachycardia or fibrillation | 3 |
| Other variables | |
| Arterial base excess more negative than 8 mEq/L | 10 |
| Arterial pH <7.25 | 10 |
| Rapid reversal of MH signs of metabolic and/or respiratory acidosis with IV dantrolene | 5 |
| CK, creatine kinase; MH, malignant hyperthermia; PaCO2, partial pressure of carbon dioxide; PETCO2, quantitative end-tidal carbon dioxide. | |
| Table 3. Case Patient Total Score | |
| Clinical indication | Points |
|---|---|
| Blood potassium >6 mEq/L | 3 |
| PETCO2 >60 with spontaneous ventilation | 15 |
| Rapid increase in temperature | 15 |
| Inappropriate tachycardia | 10 |
| Arterial pH <7.25 | 10 |
| Rapid reversal with IV dantrolene | 5 |
| PETCO2, quantitative end-tidal carbon dioxide. | |
In conclusion, this case report supports that early awareness and prompt treatment are essential when clinical signs of MH are present. In our case we were fortunate that multiple staff members (both anesthesia and OR nurses) were available to provide excellent assistance during this critical event.
Epure reported no relevant financial disclosures.
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Not sure about this statement “The diagnosis of MH is presumptive……..”
if it walks like a duck and it quacks like a duck…..it’s a duck!
I might leave out the word “almost” in the penultimate paragraph.
Great response to a life threatening crisis and shows the benefit of availability of help in the OR.
“At the conclusion of the case, the LMA was removed”?
Did I misread that? Isn’t it obvious that you switch out the LMA for an ETT ASAP if MH is suspected??????
Am I wrong?